Dissertations / Theses on the topic 'Communications and networks technologies'

The past few years have seen a major change in cellular networks, as explosive growth in data demands requires more and more network capacity and backhaul capability. New wireless technologies have been proposed to tackle these challenges. One of the emerging technologies is device-to-device (D2D) communications. It enables two cellular user equipment (UEs) in proximity to communicate with each other directly reusing cellular radio resources. In this case, D2D is able to offload data traffic from central base stations (BSs) and significantly improve the spectrum efficiency of a cellular network, and thus is one of the key technologies for the next generation cellular systems. Radio resource management (RRM) for D2D communications and how to effectively exploit the potential benefits of D2D are two paramount challenges to D2D communications underlaying cellular networks. In this thesis, we focus on four problems related to these two challenges. In Chapter 2, we utilise the mixed integer non-linear programming (MINLP) to model and solve the RRM optimisation problems for D2D communications. Firstly we consider the RRM optimisation problem for D2D communications underlaying the single carrier frequency division multiple access (SC-FDMA) system and devise a heuristic sub-optimal solution to it. Then we propose an optimised RRM mechanism for multi-hop D2D communications with network coding (NC). NC has been proven as an efficient technique to improve the throughput of ad-hoc networks and thus we apply it to multi-hop D2D communications. We devise an optimal solution to the RRM optimisation problem for multi-hop D2D communications with NC. In Chapter 3, we investigate how the location of the D2D transmitter in a cell may affect the RRM mechanism and the performance of D2D communications. We propose two optimised location-based RRM mechanisms for D2D, which maximise the throughput and the energy efficiency of D2D, respectively. We show that, by considering the location information of the D2D transmitter, the MINLP problem of RRM for D2D communications can be transformed into a convex optimisation problem, which can be efficiently solved by the method of Lagrangian multipliers. In Chapter 4, we propose a D2D-based P2P le sharing system, which is called Iunius. The Iunius system features: 1) a wireless P2P protocol based on Bittorrent protocol in the application layer; 2) a simple centralised routing mechanism for multi-hop D2D communications; 3) an interference cancellation technique for conventional cellular (CC) uplink communications; and 4) a radio resource management scheme to mitigate the interference between CC and D2D communications that share the cellular uplink radio resources while maximising the throughput of D2D communications. We show that with the properly designed application layer protocol and the optimised RRM for D2D communications, Iunius can significantly improve the quality of experience (QoE) of users and offload local traffic from the base station. In Chapter 5, we combine LTE-unlicensed with D2D communications. We utilise LTE-unlicensed to enable the operation of D2D in unlicensed bands. We show that not only can this improve the throughput of D2D communications, but also allow D2D to work in the cell central area, which normally regarded as a “forbidden area” for D2D in existing works. We achieve these results mainly through numerical optimisation and simulations. We utilise a wide range of numerical optimisation theories in our works. Instead of utilising the general numerical optimisation algorithms to solve the optimisation problems, we modify them to be suitable for the specific problems, thereby reducing the computational complexity. Finally, we evaluate our proposed algorithms and systems through sophisticated numerical simulations. We have developed a complete system-level simulation framework for D2D communications and we open-source it in Github: https://github.com/mathwuyue/py- wireless-sys-sim.

Optical packet switching (OPS) is the most prominent candidate transport solution that can seamlessly integrate electrical and optical layers by transferring certain switching functionality from electronics to optics, thus alleviating unnecessarily slow and expensive optical-electrical-optical conversions and signal processing at the switching node. Optical Label Switching (OLS) is an important aspect of the optical packet switched network that enables very low-latency forwarding of ultra-high bit-rate, protocol-independent packets entirely in the optical domain. The objective of the proposed research is to develop novel, efficient techniques to realize several key enabling technologies such as optical label generation and encoding, optical label swapping, all-optical buffering, and spectral efficient transmission system for optical label switched based OPS networks. A novel scheme of generating optical label at the ingress node using optical carrier suppression and separation (OCSS) technique is proposed. This scheme does not suffer from any unavoidable interference, limited extinction ratio or strict synchronization requirements between payload and label as observed by the currently available other label generation methods. One of the primary challenges to realize optical label swapping at the core node of scalable OLS network is the insertion of new optical labels without any wavelength conversion for same wavelength packet routing. A novel mechanism to realize same wavelength packet switching without using any conventional wavelength converter in the OLS network carrying differential phase-shift keying (DPSK) modulated payload and on-off keying (OOK) modulated optical label is demonstrated. Also a new dense wavelength division multiplexing (DWDM) optical buffer architecture using optical fiber delay lines that can provide wavelength selective reconfigurable variable delays is proposed. Optical packet switching provides automated, reconfigurable, and faster provision of both wavelength and bandwidth with finer granularity in the optical layer. However, a newer, cost-effective, and spectrally efficient optical transmission technology is essential to support the explosive bandwidth demand expected by the future optical packet switched networks. To meet this challenge, a spectrally efficient solution for transporting 40 Gbps per channel data over 50 GHz spaced DWDM system is developed by exploiting optical carrier suppression and separation technique and optical duobinary modulation.

Wireless network virtualization (WNV) and millimeter wave (mmW) communications are emerging as two key technologies for cellular networks. Virtualization in cellular networks enables wireless services to be decoupled from network resources (e.g., infrastructure and spectrum) so that multiple virtual networks can be built using a shared pool of network resources. At the same time, utilization of the large bandwidth available in mmW frequency band would help to overcome ongoing spectrum scarcity issues. In this context, this dissertation presents efficient frameworks for building virtual networks in sub-6 GHz and mmW bands. Towards developing the frameworks, first, we derive a closed-form expression for the downlink rate coverage probability of a typical sub-6 GHz cellular network with known base station (BS) locations and stochastic user equipment (UE) locations and channel conditions. Then, using the closed-form expression, we develop a sub-6 GHz virtual resource allocation framework that aggregates, slices, and allocates the sub-6 Ghz network resources to the virtual networks in such a way that the virtual networks' sub-6 GHz downlink coverage and rate demands are probabilistically satisfied while resource over-provisioning is minimized in the presence of uncertainty in UE locations and channel conditions. Furthermore, considering the possibility of lack of sufficient sub-6 GHz resources to satisfy the rate coverage demands of all virtual networks, we design a prioritized sub-6 GHz virtual resource allocation scheme where virtual networks are built sequentially based on their given priorities. To this end, we develop static frameworks that allocate sub-6 GHz resources in the presence of uncertainty in UE locations and channel conditions, i.e., before the UE locations and channel conditions are revealed. As a result, when a slice of a BS serves its associated UEs, it can be over-satisfied (i.e., resources left after satisfying the rate demands of all UEs) or under-satisfied (i.e., lack of resources to satisfy the rate demands of all UEs). On the other hand, it is extremely challenging to execute the entire virtual resource allocation process in real time due to the small transmission time intervals (TTIs) of cellular technologies. Taking this into consideration, we develop an efficient scheme that performs the virtual resource allocation in two phases, i.e., virtual network deployment phase (static) and statistical multiplexing phase (adaptive). In the virtual network deployment phase, sub-6 GHz resources are aggregated, sliced, and allocated to the virtual networks considering the presence of uncertainty in UE locations and channel conditions, without knowing which realization of UE locations and channel conditions will occur. Once the virtual networks are deployed, each of the aggregated BSs performs statistical multiplexing, i.e., allocates excess resources from the over-satisfied slices to the under-satisfied slices, according to the realized channel conditions of associated UEs. In this way, we further improve the sub-6 GHz resource utilization. Next, we steer our focus on the mmW virtual resource allocation process. MmW systems typically use beamforming techniques to compensate for the high pathloss. The directional communication in the presence of uncertainty in UE locations and channel conditions, make maintaining connectivity and performing initial access and cell discovery challenging. To address these challenges, we develop an efficient framework for mmW virtual network deployment and UE assignment. The deployment decisions (i.e., the required set of mmW BSs and their optimal beam directions) are taken in the presence of uncertainty in UE locations and channel conditions, i.e., before the UE locations and channel conditions are revealed. Once the virtual networks are deployed, an optimal mmW link (or a fallback sub-6 GHz link) is assigned to each UE according to the realized UE locations and channel conditions. Our numerical results demonstrate the gains brought by our proposed scheme in terms of minimizing resource over-provisioning while probabilistically satisfying virtual networks' sub-6 GHz and mmW demands in the presence of uncertainty in UE locations and channel conditions.
Doctor of Philosophy
In cellular networks, mobile network operators (MNOs) have been sharing resources (e.g., infrastructure and spectrum) as a solution to extend coverage, increase capacity, and decrease expenditures. Recently, due to the advent of 5G wireless services with enormous coverage and capacity demands and potential revenue losses due to over-provisioning to serve peak demands, the motivation for sharing and virtualization has significantly increased in cellular networks. Through wireless network virtualization (WNV), wireless services can be decoupled from the network resources so that various services can efficiently share the resources. At the same time, utilization of the large bandwidth available in millimeter wave (mmW) frequency band would help to overcome ongoing spectrum scarcity issues. However, due to the inherent features of cellular networks, i.e., the uncertainty in user equipment (UE) locations and channel conditions, enabling WNV and mmW communications in cellular networks is a challenging task. Specifically, we need to build the virtual networks in such a way that UE demands are satisfied, isolation among the virtual networks are maintained, and resource over-provisioning is minimized in the presence of uncertainty in UE locations and channel conditions. In addition, the mmW channels experience higher attenuation and blockage due to their small wavelengths compared to conventional sub-6 GHz channels. To compensate for the high pathloss, mmW systems typically use beamforming techniques. The directional communication in the presence of uncertainty in UE locations and channel conditions, make maintaining connectivity and performing initial access and cell discovery challenging. Our goal is to address these challenges and develop optimization frameworks to efficiently enable virtualization and mmW technologies in cellular networks.

Mestrado em Engenharia Eletrónica e Telecomunicações
Low-Power Wide Area Networks (LPWANs) are one set of technologies that are growing in the eld of the Internet of Things (IoT). Due to the long range capabilities and low energy consumption, Low-Power Wide Area Networks (LPWANs) are the ideal technologies to send small data occasionally. With their unique characteristics, LPWANs can be used in many applications and in di erent environments such as urban, rural and even indoor. The work developed in this dissertation presents a study on the LPWAN LoRa technology, by testing and evaluate its range, signal quality properties and its performance in delivering data. For this, three distinct scenarios are proposed and tested. The inclusion of LoRa in a multi-technology data gathering platform is the key objective of this dissertation. For this it is proposed: (1) an organization based in clusters of sensor nodes; (2) a Media Access Control (MAC) protocol to provide e cient communications through the LoRa technology; and nally, (3) a Connection Manager that is capable of managing the di erent available technologies in the sensor nodes and that is able to adapt its actions according to the acquired data type is proposed. The performed tests aim to perceive which type of parameters can in uence the performance of the overall proposed solution, as well as the advantages of a multi-technology approach in a data gathering platform.
Low-Power Wide Area Networks (LPWANs) são um conjunto de tecnologias em crescimento na área da Internet of Things (IoT). Devido ás suas capacidades de comunicar a longo alcance e de baixo consumo energético, as LPWANs apresentam-se como a tecnologia ideal para o envio ocasional de pequenas porções de dados. Ao possuírem características únicas, as LPWANs podem ser usadas em diversas aplicações e em diferentes ambientes, sejam eles urbanos, rurais ou interiores. O trabalho desenvolvido nesta dissertação apresenta um estudo acerca da tecnologia Long Range (LoRa), uma LPWAN, testando e avaliando o seu alcance, a qualidade do sinal e o desempenho na entrega de dados. Para isso, três cenários distintos são propostos e testados. A inclusão de LoRa numa plataforma de aquisição de dados com múltiplas tecnologias e um dos objectivos chave desta dissertação. Para isso, são propostas: (1) uma organização baseada em clusters de sensores; (2) um protocolo de controlo de acesso ao meio (MAC) para permitir que as comunicações através de LoRa sejam eficientes; e finalmente, (3) um gestor de conectividade com capacidade de gerir as diferentes tecnologias disponíveis nos sensores e que seja capaz de agir consoante o tipo de dados adquiridos. Os testes efectuados tem como objectivo perceber que tipo de parâmetros podem influenciar o desempenho global da soluçao proposta, bem como as vantagens de usar uma abordagem baseada em múltiplas tecnologias numa plataforma de aquisição de dados.

Over the past decade, wireless data communication has experienced a phenomenal growth, which is driven by the popularity of wireless devices and the growing number of bandwidth hungry applications. During the same period, various advanced communication technologies have emerged to improve network throughput. Some examples include multi-input multi-output (MIMO), full duplex, cognitive radio, mmWave, among others. An important research direction is to understand the impacts of these new technologies on network throughput performance. Such investigation is critical not only for theoretical understanding, but also can be used as a guideline to design algorithms and network protocols in the field. The goal of this dissertation is to understand the impact of some advanced technologies on network throughput performance. More specifically, we investigate the following three technologies: MIMO, full duplex, and mmWave communication. For each technology, we explore the performance envelope of wireless networks by studying a throughput maximization problem.
Ph. D.

L’étude réalisée dans ce mémoire porte sur la communication et la transmission des données dans le contexte des réseaux de capteurs. Pour améliorer la fiabilité de transmission, des relais sont insérés entre les capteurs et la destination afin de pouvoir corriger les erreurs de transmissions en utilisant des codes LDPC. L’architecture est donc optimisée grâce aux codes en blocs mais aussi à l’aide des protocoles de détection d’erreurs et aussi à l’aide de la combinaison de la correction et de la détection d’erreurs. Les systèmes d’antennes multiples forment également une option très intéressante pour l’amélioration des performances. L’efficacité énergétique est étudiée dans les différents protocoles et solutions proposés. Une optimisation conjointe du codage de canal et du codage de réseau physique est également effectuée
The work done in this study focuses on communication and data transmission in the context of sensor networks. To improve the reliability of transmission, relays are inserted between the sensors and the destination in order to correct errors in transmissions using LDPC codes. The architecture is optimized thanks to the block codes but also to the error detection protocols and the use of a combination of the error correction and detection. Another interesting way to improve performances is to use multiple antenna systems. Energy efficiency is evaluated in the protocols studied and the solutions proposed. Besides, a joint optimization of channel coding and physical network coding is proposed in this paper

The unlicensed wireless spectrum offers exciting opportunities for developing innovative wireless applications. This has been true ever since the 2.4 GHz band and parts of the 5 GHz bands were first opened for unlicensed access worldwide. In recent years, the 5 GHz unlicensed bands have been one of the most coveted for launching new wireless services and applications due to their relatively superior propagation characteristics and the abundance of spectrum therein. However, the appetite for unlicensed spectrum seems to remain unsatiated; the demand for additional unlicensed bands has been never-ending. To meet this demand, regulators in the US and Europe have been considering unlicensed operations in the 5.9 GHz bands and in large parts of the 6 GHz bands. In the last two years alone, the Federal Communications Commission in the US has added more than 1.2 GHz of spectrum in the pool of unlicensed bands. Wi-Fi networks are likely to be the biggest beneficiaries of this spectrum. Such abundance of spectrum would allow massive improvements in the peak throughput and potentially allow a considerable reduction of latency, thereby enabling support for emerging wireless applications such as augmented and virtual reality, and mobile gaming using Wi-Fi over unlicensed bands. However, access to these bands comes with its challenges. Across the globe, a wide range of incumbent wireless technologies operate in the 5 GHz and 6 GHz bands. This includes weather and military radars, and vehicular communication systems in the 5 GHz bands, and fixed-service systems, satellite systems, and television pick-up stations in the 6 GHz bands. Furthermore, due to the development of several cellular-based unlicensed technologies (such as Licensed Assisted Access and New Radio Unlicensed, NR-U), the competition for channel access among unlicensed devices has also been increasing. Thus, coexistence across wireless technologies in the 5 GHz and 6 GHz bands has emerged as an extremely challenging and interesting research problem. In this dissertation, we first take a comprehensive look at the various coexistence scenarios that emerge in the 5 GHz and 6 GHz bands as a consequence of new regulatory decisions. These scenarios include coexistence between Wi-Fi and incumbent users (both in the 5 GHz and 6 GHz bands), coexistence of Wi-Fi and vehicular communication systems, coexistence across different vehicular communication technologies, and coexistence across different unlicensed systems. Since a vast majority of these technologies are fundamentally different from each other and serve diverse use-cases each coexistence problem is unique. Insights derived from an in-depth study of one coexistence problem do not help much when the coexisting technologies change. Thus, we study each scenario separately and in detail. In this process, we highlight the need for the design of novel coexistence mechanisms in several cases and outline potential research directions. Next, we shift our attention to coexistence between Wi-Fi and vehicular communication technologies designed to operate in the 5.9 GHz intelligent transportation systems (ITS) bands. Until the development of Cellular V2X (C-V2X), dedicated short range communications (DSRC) was the only major wireless technology that was designed for communication in high-speed and potentially dense vehicular settings. Since DSRC uses the IEEE 802.11p standard for its physical (PHY) and medium access control (MAC) layers, the manner in which DSRC and Wi-Fi devices try to gain access to the channel is fundamentally similar. Consequently, we show that spectrum sharing between these two technologies in the 5.9 GHz bands can be easily achieved by simple modifications to the Wi-Fi MAC layer. Since the design of C-V2X in 2017, however, the vehicular communication landscape has been fast evolving. Because DSRC systems were not widely deployed, automakers and regulators had an opportunity to look at the two technologies, consider their benefits and drawbacks and take a fresh look at the spectrum sharing scenario. Since Wi-Fi can now potentially share the spectrum with C-V2X at least in certain regions, we take an in-depth look at various Wi-Fi and C-V2X configurations and study whether C-V2X and Wi-Fi can harmoniously coexist with each other. We determine that because C-V2X is built atop cellular LTE, Wi-Fi and C-V2X systems are fundamentally incompatible with each other. If C-V2X and Wi-Fi devices are to share the spectrum, considerable modifications to the Wi-Fi MAC protocol would be required. Another equally interesting scenario arises in the 6 GHz bands, where 5G NR-U and Wi-Fi devices are likely to operate on a secondary shared basis. Since the 6 GHz bands were only recently considered for unlicensed access, these bands are free from Wi-Fi and NR-U devices. As a result, the greenfield 6 GHz bands provide a unique and rare opportunity to freshly evaluate the coexistence between Wi-Fi and cellular-based unlicensed wireless technologies. We study this coexistence problem by developing a stochastic geometry-based analytical model. We see that by disabling the listen before talk based legacy contention mechanism---which has been used by Wi-Fi devices ever since their conception---the performance of both Wi-Fi and NR-U systems can improve. This has important implications in the 6 GHz bands, where such legacy transmissions can indeed be disabled because Wi-Fi devices, for the first time since the design of IEEE 802.11a, can operate in the 6 GHz bands without any backward compatibility issues. In the course of studying the aforementioned coexistence problems, we identified several gaps in the literature on the performance analysis of C-V2X and IEEE 802.11ax---the upcoming Wi-Fi standard. We address three such gaps in this dissertation. First, we study the performance of C-V2X sidelink mode 4, which is the communication mode in C-V2X that allows direct vehicular communications (i.e., without assistance from the cellular infrastructure). Using our in-house standards-compliant network simulator-3 (ns-3) simulator, we perform simulations to evaluate the performance of C-V2X sidelink mode 4 in highway environments. In doing so, we identify that packet re-transmissions, which is a feature introduced in C-V2X to provide frequency and time diversity, thereby improving the system performance, can have the opposite effect if the vehicular density increases. In fact, packet re-transmissions are beneficial for C-V2X system performance only at low vehicular densities. Thus, if vehicles are statically configured to always use/disable re-transmissions, the maximum potential of this feature is not realized. Therefore, we propose a simple and effective, distributed re-transmission control mechanism named Channel Congestion Based Re-transmission Control (C2RC), which leverages the locally available channel sensing results to allow vehicles to autonomously decide when to switch on re-transmissions and when to switch them off. Second, we present a detailed analysis of the performance of Multi User Orthogonal Frequency Division Multiple Access (MU OFDMA)---a feature newly introduced in IEEE 802.11ax---in a wide range of deployment scenarios. We consider the performance of 802.11ax networks when the network comprises of only 802.11ax as well as a combination of 802.11ax and legacy stations. The latter is a practical scenario, especially during the initial phases of 802.11ax deployments. Simulation results, obtained from our ns-3 based simulator, give encouraging signs for 802.11ax performance in many real-world scenarios. That being said, there are some scenarios where naive usage of MU OFDMA by an 802.11ax-capable Wi-Fi AP can be detrimental to the overall system performance. Our results indicate that careful consideration of network dynamics is critical in exploiting the best performance, especially in a heterogeneous Wi-Fi network. Finally, we perform a comprehensive simulation study to characterize the performance of Multi Link Aggregation (MLA) in IEEE 802.11be. MLA is a novel feature that is likely to be introduced in next-generation Wi-Fi (i.e., Wi-Fi 7) devices and is aimed at reducing the worst-case latency experienced by Wi-Fi devices in dense traffic environments. We study the impact of different traffic densities on the 90 percentile latency of Wi-Fi packets and identify that the addition of a single link is sufficient to substantially bring down the 90 percentile latency in many practical scenarios. Furthermore, we show that while the addition of subsequent links is beneficial, the largest latency gain in most scenarios is experienced when the second link (i.e., one additional) link is added. Finally, we show that even in extremely dense traffic conditions, if a sufficient number of links are available at the MLA-capable transmitter and receiver, MLA can help Wi-Fi devices to meet the latency requirements of most real-time applications.
Doctor of Philosophy
Wireless networks have become ubiquitous in our lives today. Whether it is cellular connectivity on our mobile phones or access to Wi-Fi hotspots on laptops, tablets, and smartphones, never before has wireless communication been as integral to our lives as it is today. In many wireless communication systems, wireless devices operate by sending signals to and receiving signals from a central entity that connects to the wired Internet infrastructure. In the case of cellular networks, this entity is the cell tower deployed by the operators (such as ATandT, Verizon, etc. in the US), while the Wi-Fi router deployed in homes and offices plays this role in Wi-Fi networks. There is also another class of wireless systems, where wireless devices communicate with each other without requiring to communicate with any central entity. An example of such a distributed communication system---which is fast gaining popularity---is vehicular communication networks. End-user devices (e.g. cellphone, laptop, tablet, or a vehicle) can communicate with each other or the central entity only if they are both tuned to the same frequency channel. This channel can lie anywhere within the radio frequency spectrum, but some frequency channels (the collection of channels is referred to as frequency bands) are more favorable—--in terms of how far the signal sent over these channels can reach—--than others. Another dimension to these frequency bands is the licensing mechanism. Not all frequency bands are free to use. In fact, most frequency bands in the US and other parts of the world are licensed by the regional regulatory agencies. The most well-known example of this licensing framework is the cellular network. Cellular operators spend large amounts of money (to the tune of billions of dollars) to gain the privileges of exclusively operating in a given frequency band. No other operator or wireless device is then allowed to operate in this band. Without any external interfering wireless device, cellular operators can guarantee a certain quality of service that is provided to its customers. Thus, the benefits of using licensed frequency bands are obvious but these bands and their associated benefits come at a high price. An alternative to licensed frequency bands are the unlicensed ones. As the name suggests, unlicensed frequency bands are those where any two or more wireless devices can communicate with each other (subject to certain rules) without having to pay any licensing fees. Unsurprisingly, because there is no limit to who or how many devices can communicate over these bands, wireless devices in these bands frequently experience external interference, which manifests to the end-user in terms of interruption of service. The best example of a wireless technology that uses unlicensed bands is Wi-Fi. One of the greatest advantages of Wi-Fi networks is that anyone can purchase a Wi-Fi router and deploy it within their homes or offices—--flexibility not afforded by licensed bands. However, this very flexibility and ease-of-use can sometimes contribute negatively to Wi-Fi performance. Arguably, we have all faced scenarios where the performance of Wi-Fi is poor. This is most likely to happen in scenarios where there are hundreds (or even thousands) of neighboring Wi-Fi devices, such as at stadiums, railway stations, concerts, etc. Based on our discussions above, it is clear as to why Wi-Fi performance suffers in such scenarios. Thus, although unlicensed bands are lucrative in terms of low-cost, and ease of use, there is no guarantee on how good a voice/video call or a video streaming session conducted over Wi-Fi will be. The above problem is well-known and well-researched. Regulators, researchers, and service providers actively seek solutions to offer better performance over unlicensed bands. An obvious solution is to make more unlicensed bands available; if all neighboring Wi-Fi users communicate with their respective routers on different channels, everyone could communicate interference-free. The problem, however, is that frequency bands are limited. Even more limited are those bands that support wireless communications over larger distances. Another solution is to improve the wireless technology—if a Wi-Fi device can more efficiently utilize the channel, its performance is likely to improve. This fact has driven the constant evolution of all wireless technologies. However, there are fundamental limits to how much a frequency channel can be exploited. Therefore, in recent years, stakeholders have turned to spectrum sharing. Even though a wireless network may possess an exclusive license to operate on a given frequency band, its users do not use the band everywhere and at all times. Then why not allow unlicensed wireless devices to operate in this band at such places and times? This is precisely the premise of spectrum sharing. In this dissertation, we look at the problem of coexistence between wireless technologies in the 5 GHz and 6 GHz bands. These two bands are extremely lucrative in terms of their relatively favorable propagation characteristics (i.e., their communication range) and the abundance of spectrum therein. Consequently, these bands have garnered considerable attention in recent years with the objective of opening these bands up for unlicensed services. However, the 5 GHz and 6 GHz bands are home to several licensed systems, and the performance of these systems cannot be compromised if unlicensed operations are allowed. Significant activity has taken place since 2013 concerning new technologies being developed, new spectrum sharing scenarios being proposed, and new rules being adopted in these two bands. We begin the dissertation by taking a comprehensive look at these issues, describing the various coexistence scenarios, surveying the existing literature, describing the major challenges, and providing directions for potential research. Next, we look at three coexistence problems in detail: (i) coexistence of dedicated short range communications (DSRC) and Wi-Fi, (ii) coexistence of cellular V2X (C-V2X) and Wi-Fi, and (iii) coexistence of 5G New Radio Unlicensed (5G NR-U) and Wi-Fi. The former two scenarios involve the coexistence of Wi-Fi with a vehicular communication technology (DSRC or C-V2X). These scenarios arose due to considerations in the US and Europe to allow Wi-Fi operations (on an unlicensed secondary basis) in the spectrum that was originally reserved for vehicular communications. Our work shows that because DSRC and Wi-Fi are built on top of fundamentally similar protocols, they are, to an extent, compatible with each other, and coexistence between these two technologies can be achieved by relatively simple modifications to the Wi-Fi protocol. However, C-V2X, owing to its inheritance from the cellular LTE, is not compatible with Wi-Fi. Consequently, significant research is required if the two technologies are to share the spectrum. On the other hand, in the coexistence of 5G NR-U and Wi-Fi, we focus on the operations of these two technologies in the 6 GHz bands. NR-U is a technology that is built atop the 5G cellular system, but is designed to operate in the unlicensed bands (in contrast to traditional cellular systems which only operate in licensed bands). Although these two technologies can coexist in the 5 GHz and 6 GHz bands, we restrict our attention in this dissertation to the 6 GHz bands. This is because the 6 GHz bands are unique in that the entire range of the 6 GHz bands were opened up for unlicensed access all at once recently, and no Wi-Fi or NR-U devices currently operate in these bands. As a result, we can learn from the mistakes made in the 5 GHz bands, where a vast majority of today's Wi-Fi networks operate. Our work shows that, indeed, we can take decisive steps---such as disabling certain Wi-Fi functions---in the 6 GHz bands, which can facilitate better coexistence in the 6 GHz bands. Finally, in the course of identifying and tackling the various coexistence scenarios in the 5 GHz and 6 GHz bands, we identify some open issues in the performance of new wireless technologies designed to operate in these bands. Specifically, we highlight the need to better understand and characterize the performance of Multi User Orthogonal Frequency Division Multiple Access (MU OFDMA), a feature common in cellular networks but newly introduced to Wi-Fi, in the upcoming Wi-Fi 6 generation of devices. We propose and evaluate an analytical model for the same. We also characterize the performance of Multi Link Aggregation---which a novel feature likely to be introduced in future Wi-Fi 7 devices---that is aimed at reducing the worst-case delay experienced by Wi-Fi devices in dense traffic conditions. Additionally, we identify an issue in the performance of the distributed operational mode of C-V2X. We show that packet re-transmissions, which is a feature aimed at improving the performance of C-V2X, can have a counter-productive effect and degrade the C-V2X performance in certain environments. We address this issue by proposing a simple, yet effective, re-transmission control mechanism.

Dynamic spectrum access (DSA) wireless networks focus on using RF spectrum more efficiently and dynamically. Significant progress has been made during the past few years. For example, many measurements of current spectrum utilization are available. Theoretical analyses and computational simulations of DSA networks also abound. In sharp contrast, few network systems, particularly those with a decentralized structure, have been built even at a small scale to investigate the performance, behavior, and dynamics of DSA networks under different scenarios. This dissertation provides the theory, design, and implementation of a software radio-based decentralized DSA network prototype, and its enabling technologies: software radio, signal detection and classification, and distributed cooperative spectrum sensing. By moving physical layer functions into the software domain, software radio offers an unprecedented level of flexibility in radio development and operation, which can facilitate research and development of cognitive radio (CR) and DSA networks. However, state-of-the-art software radio systems still have serious performance limitations. Therefore, a performance study of software radio is needed before applying it in any development. This dissertation investigates three practical issues governing software radio performance that are critical in DSA network development: RF front end nonlinearity, dynamic computing resource allocation, and execution latency. It provides detailed explanations and quantitative results on SDR performance. Signal detection is the most popular method used in DSA networks to guarantee non-interference to primary users. Quickly and accurately detecting signals under all possible conditions is challenging. The cyclostationary feature detection method is attractive for detecting primary users because of its ability to distinguish between modulated signals, interference, and noise at a low signal-to-noise ratio (SNR). However, a key issue of cyclostationary signal analysis is the high computational cost. To tackle this challenge, parallel computing is applied to develop a cyclostationary feature based signal detection method. This dissertation presents the methodâ s performance on multiple signal types in noisy and multi-path fading environments. Distributed cooperative spectrum sensing is widely endorsed to monitor the radio environment so as to guarantee non-interference to incumbent users even at a low SNR and under hostile conditions like shadowing, fading, interference, and multi-path. However, such networks impose strict performance requirements on data latency and reliability. Delayed or faulty data may cause secondary users to interfere with incumbent users because secondary users could not be informed quickly or reliably. To support such network performance, this dissertation presents a set of data process and management schemes in both sensors and data fusion nodes. Further, a distributed cooperative sensor network is built from multiple sensors; together, the network compiles a coherent semantic radio environment map for DSA networks to exploit available frequencies opportunistically. Finally, this dissertation presents the complete design of a decentralized and asynchronous DSA network across the PHY layer, MAC layer, network layer, and application layer. A ten-node prototype is built based on software radio technologies, signal detection and classification methods, distributed cooperative spectrum sensing systems, dynamic wireless protocols, and a multi-channel allocation algorithm. Systematic experiments are carried out to identify several performance determining factors for decentralized DSA networks.
Ph. D.

Doutoramento em Engenharia Eletrotécnica - Telecomunicações
The work presented herein, studies Next Generation Optical Access Networks (NG-OAN) economically (e.g. energy consumption) and technologically (e.g. rate, reach and dedicated/shared bandwidth). The work is divided into four main topics: energy efficiency in optical access architectures, novel spectrally efficient Long-Reach Passive Optical Networks (LR-PON), crosstalk impacts in heterogeneous and homogenous access networks and hybrid optical wireless transmissions. We investigate the impact of user profiles, optical distribution network topologies and equipment characteristics on resource sharing and power consumption in LR-PON. To have a clear vision on the energy consumption evolution of each part of NG-OAN, a model is proposed to evaluate the energy efficiency of optical access technologies. A spectrally efficient bidirectional Ultra-Dense Wavelength Division Multiplexing (UDWDM) PON architecture is developed using Nyquist shaped 16-ary quadrature amplitude modulation, offering up to 10 Gb/s service capabilities per user or wavelength. Performance of this system in terms of receiver sensitivity and nonlinear tolerance under different network transmission capacity conditions are experimentally optimized. In bi-directional transmis-sion, using frequency up/down-shifting of Nyquist pulse shaped signal from optical carrier, a full bandwidth allocation and easy maintenance of UDWDM networks as well as reduction of Rayleigh back-scattering are achieved. Moreover, self-homodyne detection is used to relax the laser linewidth requirement and digital signal processing complexity at the optical network unit. Simplified numerical model to estimate the impact of Raman crosstalk of multi-system next generation PONs in video overlay is proposed. Coexistence of considered G.98X ITU-T series and coherent multi-wavelength systems is considered and assessed. Additionally, the performances of bidirectional hybrid optical wireless coherent PONs over different optical distribution network power budgets and hybrid splitting ratios are evaluated.
O trabalho aqui apresentado estuda redes óticas de acesso de próxima geração (NG-OAN) nas vertentes económica (consumo de energia) e tecnológica (taxa, alcance e largura de banda dedicada/partilhada). O trabalho está dividido em quatro grandes temas de investigação: a eficiência energética em arquiteturas de acesso ótico, as redes óticas passivas de longo alcance (LR-PON) com nova eficiência espetral, o impacto da diafonia em redes de acesso heterogéneas e homogéneas e as transmissões ópticas híbridas com tecnologias sem fio. Investiga-se o impacto dos perfis dos utilizadores, as tipologias da rede de distribuição ótica, as características do equipamento de partilha de recursos e o consumo de energia em LR-PON. Para se ter uma visão clara sobre o consumo de energia de cada parte das NG-OAN, é proposto um modelo para avaliar a eficiência energética das tecnologias de acesso óticas. Desenvolve-se uma arquitetura PON bi-direcional com elevada eficiência espetral, recorrendo a multiplexagem por divisão de comprimento de onda ultra-densa (UDWDM), modulação de amplitude em quadratura com formato de impulso de Nyquist, oferecendo até 10 Gb/s por utilizador/comprimento de onda. O desempenho deste sistema em termos de sensibilidade do recetor e da tolerância à resposta não linear do canal de comunicação, sob diferentes condições de transmissão, é avaliado experimentalm-ente. Em transmissão bi-direcional, utilizando desvio de frequência (cima/baixo) do impulso com formato de Nyquist relativo à portadora ótica conseguiu-se uma alocação de largura de banda completa e uma manutenção mais simplificada de redes UDWDM, bem como a redução do espalhamento de Rayleigh. Além disso, a deteção auto-homodina é usada para relaxar o requisito de largura de linha do laser e a complexidade do processamento digital de sinal nas unidades da rede ótica. Propõe-se um modelo numérico simplificado para estimar o impacto da diafonia de Raman em sistemas PON de próxima geração, com sobreposição do sinal de vídeo. É analisada a coexistência da série G.98X ITU-T e são considerados e avaliados sistemas coerentes multi-comprimento de onda. Adicionalmente avaliam-se os desempenhos de PONs bi-direcionais híbridas, considerando tecnologia coerente e propagação por espaço livre, para diferentes balanços de potência e taxas de repartição na rede ótica de distribuição.

Le cadre général de la thèse concerne les réseaux de capteurs et la sécurisation des communications sans fil pour la mise en œuvre de systèmes fiables de surveillance orienté santé. Plus précisément, ce travail de thèse présente un nouveau système de surveillance biomédical à base de réseau de capteurs sans fil, pour la mesure de l'activité électrique du cerveau. Un réseau de capteurs sans fil de type EEG (électroencéphalogramme) permet de surveiller les ondes cérébrales spontanées, y compris les ondes normales et anormales, des patients souffrant de différents types d'épilepsie. Un capteur sans fil enregistre les signaux du patient (via le cuir chevelu) et filtre ces signaux et leurs données en parallèle selon un traitement approprié des ondes cérébrales. Il est dès lors possible de prédire la gravité d'une attaque épileptique à venir. Une première approche est proposée pour analyser les anomalies des ondes cérébrales et déclencher des alertes le cas échéant. De tels systèmes peuvent permettre de sauver de nombreux patients en prédisant l’arrivée les crises avant qu'elles ne surviennent et éviter ainsi les accidents et les comportements à risque lors d'une crise d'épilepsie. De plus, l’approche peut être utiliser pour d'autres mesures de diagnostic médical. Une autre approche basé sur l’apprentissage pour la prédiction en utilisant les réseaux de neurones de type FFNN (Feed Forward Neural Network ) est également présentée. Par ailleurs, Les approches de prédiction, exploitent la norme IEEE802.11n pour la transmission des données avec un protocole de confidentialité pour la sécurisation des communications. La mise en œuvre de la sécurité peut réduire considérablement le temps de la prédiction et retarder les signaux d’alerte des crises. Les mesures effectuées permettent la calibration des algorithmes de prédiction pour tenir compte des délais introduits par la sécurisation des communications
The general framework of the thesis concerns sensor networks and the privacy protocols for wireless communications in the implementation of reliable healthcare systems. More precisely, it presents a novel biomedical wireless sensor Network monitoring system, as a predictor and advance sensitive portable electroencephalogram (EEG). The EEG wireless sensor network proposed to monitor spontaneous brain waves, including normal and abnormal waves, for the patients suffering from different types of epilepsy. The biomedical epilepsy wireless sensor Network monitoring system (WSN-EEG) read’s signals from a wireless sensor network on the patient scalp, and filter these signals to run parallel data processing for the brain waves. However, the predicting procedure for the severity of the forthcoming epileptic attack based on, a proposed mathematical model, which analyses the abnormality in the brain waves and alerts by giving signals for the patient. This method can save many patients by predicting the seizure before it occurs and helps them from different injuries and risky behavior arising during epilepsy attack. In addition, the proposed approaches can use the patient data for further medical diagnosis measures. Another approach is proposed as a learning-based approach for prediction using Feed Forward Neural Network (FFNN) for the alert system. The research used the IEEE802.11n as a communication method for the wireless sensor networks and measure the IEEE802.11n security performances as privacy protocol for data transmission of the proposed systems. The measurements indicated the calibration of the prediction algorithms to take account of the delays introduced by the security of the communications in the data transmission and seizure prediction which might significantly reduce prediction time and delay the alert signals

Les progrès des technologies de communication à faible consommation d’énergie et à faible cout ont révolutionne les applications de télédétection et de surveillance. L’Internet des objets (IoT) a promis la création d’un écosystème d’appareils connectes à travers un large éventail d’applications, telles que les villes intelligentes. A l’heure actuelle, de nombreuses normes et technologies concurrentes tentent de saisir l’IoT, en particulier dans le domaine des technologies de télédétection et de communication. LoRa (Long Range) est l’une de ces technologies qui gagne en popularité et en attraction dans les réseaux de capteurs sans fil (WSN). La possibilité d’établir des communications longue distance avec des nœuds relativement simples, une infrastructure minimale, des besoins en énergie réduits et l’utilisation de bandes ISM sans licence offre un avantage concurrentiel significatif. Bien que la portée de communication dans LoRa puisse dépasser 15 kilomètres en visibilité directe, le débit binaire maximal pouvant être atteint est limite à quelques kilobits par seconde. De plus, lorsqu’une collision se produit dans LoRa, le débit est encore réduit en raison de pertes de trames et de retransmissions. Les travaux de cette thèse traitent le problème des collisions dans LoRa qui peuvent survenir sous une charge importante et qui dégradent les performances du réseau.Premièrement, nous considérons le contexte des communications en liaison montante dans LoRaWAN. Nous étudions le contexte des signaux LoRa en collision synchronisée, ou chaque appareil terminal doit retransmettre toute sa trame en collision après qu’une collision se produit dans LoRa. Ce comportement diminue le débit global et augmente la consommation d’énergie des terminaux et le délai des trames. Pour cette raison, afin d’atténuer les effets néfastes des collisions, nous avons proposé un algorithme de décodage pour résoudre les signaux LoRa en collision synchronisée, dans un trafic réseau sature et confirme. Nous avons remplacé le modèle de retransmission conventionnel de LoRa en un modèle faisant en sorte que les dispositifs terminaux transmettent des bitmaps au lieu de retransmettre des trames entières pour déterminer les symboles corrects de chaque trame en collision. Notre algorithme a pu améliorer significativement le débit global de la couche LoRaWAN MAC à base de LoRa, et diminuer la consommation d’énergie des émetteurs et le délai des trames.Deuxièmement, nous considérons le contexte des communications en liaison descendante dans LoRaWAN. Nous avons remarqué que la liaison descendante dans LoRa est un goulot d’étranglements. Nous avons donc travaillé sur la sélection de la passerelle par le serveur de réseau et son impact sur le débit, la consommation d’énergie et le délai. Nous avons étudié trois types de déploiement de passerelle et nous avons montre que les performances du système dépendent de ce déploiement. Nous avons montré que l’équilibrage du nombre de terminaux par passerelle (également connu sous le nom de charge) améliore le débit par rapport au choix de la passerelle avec la meilleure qualité de signal. En outre, nous avons montré que la combinaison de la charge et de la qualité du signal n’améliore pas davantage le débit. De plus, nous avons montré que le choix de la passerelle avec la meilleure qualité de signal diminue le délai des trames et la consommation d’énergie des terminaux par rapport au choix de la passerelle avec la charge la plus faible
The progress in low-energy, low-cost communication technologies have revolutionized remote sensing and monitoring applications. Internet of Things (IoT) has promised an ecosystem of connected devices across a wide range of applications such as in smart cities.Currently, many competing standards and technologies are attempting to seize the IoT, particularly in the area of remote sensing and communication technologies. LoRa (Long Range) is one of those technologies that is gaining popularity and attraction in the Wireless Sensor Networks (WSN) applications. The ability to make long-distance communications with relatively simple nodes, minimal infrastructure, reduced power requirements, and the use of unlicensed ISM bands provides a significant competitive advantage. Although the communication range in LoRa can exceed 15 kilometers in line of sight, the maximum bit rate that can be achieved is limited to few kilobits per second. Additionally, when a collision occurs in LoRa, the throughput is further reduced due to frame losses and retransmissions. The work of this thesis deals with the problem of collisions in LoRa that may occur under heavy load, and which degrade the performance of the network.First, we consider the context for LoRaWAN uplink communications. We study the context of fully synchronized colliding LoRa signals, where each end-device has to retransmit its entire colliding frame after a collision occurs in LoRa. This behavior decreases the overall throughput, and increases the energy consumption of the end-devices, and the delay of the frames. Therefore, in order to mitigate the damaging effects of collisions, we proposed a decoding algorithm to resolve synchronized colliding LoRa signals, in a saturated and confirmed network traffic. We substituted the conventional retransmission model of LoRa by having end-devices transmitting bitmaps instead of retransmitting whole frames to determine the correct symbols of each colliding frame. Our algorithm was able to significantly improve the overall throughput of the LoRaWAN MAC layer based on LoRa, and to decrease the energy consumption of the transmitters and the delay of the frames.Second, we consider the context for LoRaWAN downlink communications. We noticed that the downlink in LoRa is a bottleneck. Hence, we worked on the gateway selection by the network server and its impact on the throughput, the energy consumption and the delay. We studied three types of gateway deployment and we show that the system performance depends on this deployment. We showed that balancing the number of end-devices per gateway (also known as load) improves the throughput compared to choosing the gateway with the highest signal quality. Moreover, we showed that combining load and signal quality does not further improve the throughput. In addition, we showed that choosing the gateway with the highest signal quality decreases the delay and energy consumption compared to choosing the gateway with the lowest load

La conception d'un réseau de capteurs sans fil peut présenter de nombreux défis, tels que le passage à l'echèlle, la fiabilité, la longévité et la communication en temps réel. L'existence de plusieurs points de collecte peut augmenter la fiabilité du réseau et facilite le passage à l'echèlle. Toutefois, cette amélioration dépend de l’approche de routage, qui doit être adaptée pour atteindre les objectifs de performance souhaités.Dans cette optique, l’objectif de ce travail est de trouver des moyens pour optimiser la communication dans les réseaux de capteurs sans fil à multiples points de collecte en tenant compte des problèmes liés au passage à l'echèlle, à la durée de vie du réseau, à la fiabilité (livraison des paquets) et à la minimization de la latence. Nous étudions les point d'équilibre entre le délai et la consommation d'énergie en tant que paramètres clés pour la qualité et l'efficacité de la communication. Pour ce faire, nous proposons différents algorithmes de routage, couvrant les trois principaux schémas de communication (unicast, anycast et multicast).Les simulations effectuées montrent que nos approches sont capables d’optimiser la communication, notamment en termes de latence et de durée de vie du réseau. Des expériences sur la plateforme FIT IoT-Lab fournissent également des indications significatives sur les performances de notre solution multicast dans des conditions réelles
The conception of a wireless sensor network may present numerous challenges, such as scalability, reliability, longevity and timeliness. The existence of multiple sinks may increase the network reliability and facilitates the scalability. However, this improvement is dependent on the routing approach, that must be tailored to help achieving the desired performance goals.From this perspective, the objective of this work is to find ways of optimizing the communication in multi-sink wireless sensor networks considering the problems related to the scalability, longevity (network lifetime), reliability (packet delivery) and timeliness (latency). We investigate the trades among data delivery time and energy consumption as key metrics for communication quality and efficiency. For that matter, we propose different routing algorithms, covering all three main communciations schemes (unicast, anycast and multicast).The executed simulations show that our approaches are capable of optimizing the communication, especially in terms of latency and network lifetime. Experiments on the FIT IoT-Lab platform also provide meaningful insights of the performance of our multicast solution in real environment condition

Drones can be used for several civil applications including search and rescue, coverage, and aerial imaging. Newer applications like construction and delivery of goods are also emerging. Performing tasks as a team of drones is often beneficial but requires coordination through communication. In this thesis, the communication requirements of video streaming drone applications based on existing works are studied. The existing communication technologies are then analyzed to understand if the communication requirements posed by these drone applications can be met by the available technologies. The shortcomings of existing technologies with respect to drone applications are identified and potential requirements for future technologies are suggested. The existing communication and routing protocols including ad-hoc on-demand distance vector (AODV), location-aided routing (LAR), and greedy perimeter stateless routing (GPSR) protocols are studied to identify their limitations in context to the drone networks. An application scenario where a team of drones covers multiple areas of interest is considered, where the drones follow known trajectories and transmit continuous streams of sensed traffic (images or video) to a ground station. A route switching (RS) algorithm is proposed that utilizes both the location and the trajectory information of the drones to schedule and update routes to overcome route discovery and route error overhead. Simulation results show that the RS scheme outperforms LAR and AODV by achieving higher network performance in terms of throughput and delay. Video streaming drone applications such as search and rescue, surveillance, and disaster management, benefit from multicast wireless video streaming to transmit identical data to multiple users. Video multicast streaming using IEEE 802.11 poses challenges of reliability, performance, and fairness under tight delay bounds. Because of the mobility of the video sources and the high data-rate of the videos, the transmission rate should be adapted based on receivers' link conditions. Rate-adaptive video multicast streaming in IEEE 802.11 requires wireless link estimation as well as frequent feedback from multiple receivers. A contribution to this thesis is an application-layer rate-adaptive video multicast streaming framework using an 802.11 ad-hoc network that is applicable when both the sender and the receiver nodes are mobile. The receiver nodes of a multicast group are assigned with roles dynamically based on their link conditions. An application layer video multicast gateway (ALVM-GW) adapts the transmission rate and the video encoding rate based on the received feedback. Role switching between multiple receiver nodes (designated nodes) cater for mobility and rate adaptation addresses the challenges of performance and fairness. The reliability challenge is addressed through re-transmission of lost packets while delays under given bounds are achieved through video encoding rate adaptation. Emulation and experimental results show that the proposed approach outperforms legacy multicast in terms of packet loss and video quality.

This dissertation is composed of two independent studies: Cellular research and WBAN (Wireless Body Area Network) research. Both investigations are directed towards improving the system performance in wireless communication systems in terms of Quality of Service (QoS) and system capacity. For the Cellular research part, this dissertation will present novel user-specific QoS requirements as defined by their respective Mean Opinion Score (MOS) formulas, and associated schedulers for wireless applications and systems that optimize spectral allocation. User-specific QoS requirements are defined and several methods to make use of such requirements to maximum the spectral utilization are presented. Five User-Specific QoS Aware (USQA) schedulers are proposed that consider the user-specific QoS requirements in the allocation of spectral resources. Schedulers are introduced that dynamically adapt to the user-specific QoS requirements to improve quality as measured by the MOS, or the system capacity, or can improve both the quality and system capacity. Due to the different cell deployment arrangements and inter-cell interference in heterogeneous networks in comparison to homogeneous networks, the USQA scheduling is also analyzed and the system performance is evaluated in such networks. Throughput improvements of File Transfer Protocol (FTP) applications benefiting from the rate adaptation and MAC (Media Access Control) scheduling algorithms for video applications that incorporate user-specific QoS requirements to improve system capacity are demonstrated. Another novel approach recognizes that the user-specific frequency sensitivity can be used to improve capacity. There is considerable variation in the audible range of frequencies that can be perceived by individuals, especially at the high frequency end, which is primarily affected by a gradual decline with age. This can be utilized to improve the system performance by personalizing the VoIP codecs and decreasing the user's source data rate for people from an older age group and thus increase the system capacity. Given the potentially substantial system performance gain resulting from the USQA schedulers, it is critical to analyze their feasibility and complexity in practical LTE (4G cellular) and future wireless systems. From the LTE system perspective, LTE QoS end-to-end signaling procedures are addressed, and corresponding protocol adaptations are analyzed in order to support the USQA schedulers. In addition, the optimal scheduling period is analyzed that trades off between performance gain and implementation complexity. In the WBAN research, MIMO (Multiple Input Multiple Output) in vivo antenna technologies are introduced and are motivated by the high data rate requirements of wirelessly transmitted low-delay High Definition (HD) video during Minimally Invasive Surgery (MIS). MIMO in vivo technologies are proposed to be used in the in vivo environments to enhance and determine the maximum data transmission rate while satisfying the Specific Absorption Rate (SAR) power limitations. Various factors are considered in the MIMO in vivo study including antenna separation, antenna angular positions, human body size, and system bandwidth to determinate the maximum data rate that can be supported.

Cette thèse s'inscrit dans le domaine du Smart Grid. Les SGs améliorent la sécurité des réseaux électriques et permettent une utilisation adaptée de l'énergie disponible de manière limitée. Ils augmentent également l'efficacité énergétique globale en réduisant la consommation. L'utilisation de cette technologie est la solution la plus appropriée car elle permet une gestion plus efficace de l'énergie. Dans ce contexte, des compagnies comme Hydro-Québec déploient des réseaux de capteurs pour contrôler les principaux équipements. Pour réduire les coûts de déploiement et la complexité du câblage, un réseau de capteurs semble être une solution optimale. Cependant, son déploiement nécessite une connaissance approfondie de l'environnement. Les postes à haute tension sont des points stratégiques du réseau électrique et génèrent un bruit impulsif qui dégrade les performances des communications sans fil. Les travaux dans cette thèse sont centrés sur le développement de protocoles de communication performants dans ces milieux fortement perturbés. Nous avons proposé une première approche basée sur la concaténation du code à métrique de rang et le code convolutif avec la modulation OFDM. C'est une technique très efficace pour réduire l'effet du bruit impulsif tout en ayant un niveau de complexité assez faible. Une autre solution basée sur un système multi-antennaire est développée. Nous avons aussi proposé un système MIMO coopératif codé en boucle fermée basée sur le code à métrique de rang et le précodeur max-dmin. La deuxième technique est également une solution optimale pour améliorer la fiabilité du système et réduire la consommation énergétique dans les réseaux de capteurs
This thesis is mainly in the Smart Grid domain. SGs improve the safety of electrical networks and allow a more adapted use of electricity storage, available in a limited way. SGs also increase overall energy efficiency by reducing peak consumption. The use of this technology is the most appropriate solution because it allows more efficient energy management. In this context, manufacturers such as Hydro-Quebec deploy sensor networks in the nerve centers to control major equipment. To reduce deployment costs and cabling complexity, the option of a wireless sensor network seems the most obvious solution. However, deploying a sensor network requires in-depth knowledge of the environment. High voltages substations are strategic points in the power grid and generate impulse noise that can degrade the performance of wireless communications. The works in this thesis are focused on the development of high performance communication protocols for the profoundly disturbed environments. For this purpose, we have proposed an approach based on the concatenation of rank metric and convolutional coding with orthogonal frequency division multiplexing. This technique is very efficient in reducing the bursty nature of impulsive noise while having a quite low level of complexity. Another solution based on a multi-antenna system is also designed. We have proposed a cooperative closed-loop coded MIMO system based on rank metric code and max-dmin precoder. The second technique is also an optimal solution for both improving the reliability of the system and energy saving in wireless sensor networks

The adoption of wireless broadband technologies to provide network and Internet connectivity in rural communities has conveyed the possibility to overcome the challenges caused by marginalization and many other characteristics possessed by these rural communities. With their different capabilities, these technologies enable communication for rural communities internally within the community and externally on a global scale. Deployment of these technologies in rural areas requires consideration of different factors - these are in contrast, to those considered when deploying these technologies in non-rural, urban areas. Numerous research show consideration of facts for deployment of broadband technologies in urban/ non-rural environments and a little has been done in considering facts for deployment in rural environments. Hence this research aims to define guidelines for selection of broadband technologies and make recommendations on which technologies are suitable for deployment in rural communities, thereby considering facts that are true only within these rural communities. To achieve this, the research determines the metrics that are relevant and important to consider when deploying wireless broadband technology in rural communities of South Africa. It further undertakes a survey of wireless broadband technologies that are suitable for deployment in such areas. The study first profiles a list of wireless communication technologies, determines and documents characteristics of rural communities in Africa, determines metrics used to declare technologies feasible in rural areas. The metrics and rural characteristics are then used to identify technologies that are better suited than others. Informed by this initial profiling, one technology: mobile WiMAX is then selected for deployment and further evaluation. A technical review of mobile WiMAX is then carried out by deploying it at our research site in the rural, marginalized community of Dwesa (Eastern Cape, South Africa). The final section of this research provides recommendations that mobile WiMAX, LTE and Wi-Fi are the best suitable technologies for deployment in rural marginalized environments. This has been supported by extensive research and real life deployment of both Wi-Fi and mobile WiMAX. This research also recommends consideration of the following facts when seeking deployment of these technologies in rural communities: the geographical setting of the target terrain, the distances between sources and target customers and distances between target communities, weather conditions of the area, applications to be deployed over the network, social well-being of the community and their financial freedom as well.

The purpose of this research is to assess the function, form and content of knowledge sharing in communities of practice, social networks and the use of collaborative technologies in Third Sector community networks in the North East of England. This is a significant area worthy of detailed examination due to the acknowledged relationship between communities of practice, social networks and the use of collaborative technologies. These three domains have been examined separately by others and suggestions have been made as to relationships between them but few, if any, studies appear to have used case-based evidence to explore how these relationships add value to knowledge sharing. The research addresses the following research question: To what extent does the use of collaborative technologies in communities of practice and social networks, in the Third Sector of the North East region, add value to face- to-face knowledge sharing and how may this be measured? In order to answer the research question a qualitative holistic case study approach based upon three case studies in Newcastle upon Tyne, South Tyneside and Sunderland has been utilised and grounded theory is used to formulate theory from the observed and analysed practice of the case studies under investigation. The conclusion is drawn that when value is added to knowledge sharing it is relative to the strength of several key variables, including, reciprocity, trust, the strength of network ties and the ability to integrate the use of collaborative technologies into ongoing activities. To aid analysis of the presence and strength of these variables a working paradigm has been designed and developed. Case studies are analysed through this paradigm leading to the development of a theory of knowledge sharing in the Third Sector.

Le routage dans les réseaux de capteurs, est un service essentiel qui transmet les lectures des capteurs à certains points de collecte de données dans le réseau sur la base des relais multi-saut. Cette tâche est particulièrement difficile car elle doit être réalisé d'une manière efficace au niveau de consommation de ressources et avec une quantité limitée d'informations disponible. La facilité de mise à l'échelle et l'utilisation d'information local pour fonctionner ont permis au routage géographique être considéré comme une approche prometteuse. Cependant, lors de son implémentation, certains problèmes subsistent en raison des difficultés pratiques. Dans ce travail de recherche, deux problématiques inhérentes aux protocoles de routages géographique ont été étudiés: i) Le coût associé: aux évanouissements liés aux obstacles et aux multi-trajets suivis par un signal transmis sur un canal radio, aux changements rapides des conditions physiques du canal de transmission and ii) l'administration de resources affectés à chaque noeud appartenant au réseau. Afin de résoudre ce problème, deux protocoles ont été présentés: un protocole de routage géographique avec communications coopératives, Beaconless Cooperative Geographic cross-layer protocol for ad hoc and sensor networks (CoopGeo) et un protocole de routage basé sur le principe d'extension de couverture: Relay-Aware Cooperative Routing (RACR).

L’arrivée de la prochaine technologie 5G va permettre la connectivité des billions de terminaux mobiles et donc une énorme augmentation du trafic de données. A cet égard, les fournisseurs des services Cloud doivent posséder les infrastructures physiques capables de supporter cette explosion de trafic. Malheureusement, les architectures filaires conventionnelles des centres de données deviennent staturées et la congestion des équipements d’interconnexion est souvent atteinte. Dans cette thèse, nous explorons une approche récente qui consiste à augmenter le réseau filaire du centre de données avec l’infrastructure sans fil. En effet, nous exploitons une nouvelle technologie émergente, la technologie 60 GHz, qui assure un débit de l’ordre de 7 Gbits/s afin d’améliorer la QoS. Nous concevons une architecture hybride (filaire/sans fil) du réseau de centre de données basée sur : i) le modèle "Cisco’s Massively Scalable Data Center" (MSDC), et ii) le standard IEEE 802.11ad. Dans une telle architecture, les serveurs sont regroupés dans des racks, et sont interconnectés à travers un switch Ethernet, appelé top-of-rack (ToR) switch. Chaque ToR switch possède plusieurs antennes utilisées en parallèle sur différents canaux sans fil. L’objectif final consiste à minimiser la congestion du réseau filaire, en acheminant le maximum du trafic sur les canaux sans fil. Pour ce faire, cette thèse se focalise sur l’optimisation du routage et de l’allocation des canaux sans fil pour les communications inter-rack, au sein d’un centre de données hybride (HDCN). Ce problème étant NP-difficile, nous allons procéder en trois étapes. En premier lieu, on considère le cas des communications à un saut, où les racks sont placés dans le même rayon de transmission. Nous proposons un nouvel algorithme d’allocation des canaux sans fil dans les HDCN, qui permet d’acheminer le maximum des communications en sans-fil, tout en améliorant les performances réseau en termes de débit et délai. En second lieu, nous nous adressons au cas des communications à plusieurs sauts, où les racks ne sont pas dans le même rayon de transmission. Nous allons proposer une nouvelle approche optimale traitant conjointement le problème du routage et de l’allocation de canaux sans fils dans le HDCN, pour chaque communication, dans un mode online. En troisième étape, nous proposons un nouvel algorithme qui calcule conjointement le routage et l’allocation des canaux pour un ensemble des communications arrivant en mode batch (i.e., par lot). En utilisant le simulateur réseau QualNet, considérant toute la pile TCP/IP, les résultats obtenus montrent que nos propositions améliorent les performances comparées aux méthodes de l’état de l’art
The high proliferation of smart devices and online services allows billions of users to connect with network while deploying a vast range of applications. Particularly, with the advent of the future 5G technology, it is expected that a tremendous mobile and data traffic will be crossing Internet network. In this regard, Cloud service providers are urged to rethink their data center architectures in order to cope with this unprecedented traffic explosion. Unfortunately, the conventional wired infrastructures struggle to resist to such a traffic growth and become prone to serious congestion problems. Therefore, new innovative techniques are required. In this thesis, we investigate a recent promising approach that augments the wired Data Center Network (DCN) with wireless communications. Indeed, motivated by the feasibility of the new emerging 60 GHz technology, offering an impressive data rate (≈ 7 Gbps), we envision, a Hybrid (wireless/wired) DCN (HDCN) architecture. Our HDCN is based on i) Cisco’s Massively Scalable Data Center (MSDC) model and ii) IEEE 802.11ad standard. Servers in the HDCN are regrouped into racks, where each rack is equipped with a: i) Ethernet top-of-rack (ToR) switch and ii) set of wireless antennas. Our research aims to optimize the routing and the allocation of wireless resources for inter-rack communications in HDCN while enhancing network performance and minimizing congestion. The problem of routing and resource allocation in HDCN is NP-hard. To deal with this difficulty, we will tackle the problem into three stages. In the first stage, we consider only one-hop inter-rack communications in HDCN, where all communicating racks are in the same transmission range. We will propound a new wireless channel allocation approach in HDCN to hardness both wireless and wired interfaces for incoming flows while enhancing network throughput. In the second stage, we deal with the multi-hop communications in HDCN where communicating racks can not communicate in one single-hop wireless path. We propose a new approach to jointly route and allocate channels for each single communication flow, in an online way. Finally, in the third stage, we address the batched arrival of inter-rack communications to the HDCN so as to further optimize the usage of wireless and wired resources. For that end, we propose: i) a heuristic-based and ii) an approximate, solutions, to solve the joint batch routing and channel assignment. Based on extensive simulations conducted in QualNet simulator while considering the full protocol stack, the obtained results for both real workload and uniform traces, show that our proposals outperform the prominent related strategies

Geographies of ageing literature recognises the emotional qualities of ageing. However, an historical tendency to overly medicalise ageing means research often focuses on the emotions associated with specific events such as the emotions involved in living with health-related conditions, being a carer, or being cared for in different settings. There remains a paucity of research that attends to the everyday, mundane emotions of being old. This research attends to this lacuna by drawing on theoretical frames emerging from post-humanism and emotional geographies. Specifically, this research engages with the spatial organisation of emotions as it pertains to an increasingly significant element of ageing: the role of communication technology in older people's ability to create and maintain new modes of (techno)sociability. Drawing upon 29 qualitative interviews and 13 cultural probe follow up responses with retired Londoners aged 59 to 89 years, this research examines how technology connects bodies to objects, people to people and (re)connects older adults to place in new and unexpected ways. Among this participant group diverse, highly individualised and complex amalgams of communication technologies were used. Each mode of communication technology was deployed using intricate strategies of selection and implementation, based on varying temporalities and spatialities, enhancing the ability of participants to relate emotionally with others. Technology use in this regard enabled the portability and emotional continuity of social networks, as communication was no longer tied to certain physical spaces. These findings are theoretically significant as emotions are increasingly seen to have a direct impact on the spatial construction of society through shaping human capacities and behaviours, which form the world around us. Work in this domain has been limited with certain emotions and bodies being more readily researched, and affiliated with particular gendered and sexualised bodies, bodily capacities, physical forms and social identities than others. This research is able to offer an understanding not currently present in geographical literatures, and offer new modes of spatial analysis that take into account the pervasive but differentiated use of technology.

Satellite communication system designers are continuously struggling to improve the channel capacity. A critical challenge results from the limited power available aboard the satellite.Because of this constraint, the onboard power amplifier must work with a small power supply which limits its maximum output power. To ensure a sufficient Signal-to-Noise power Ratio (SNR) on the receiver side, the power amplifier must work close to its saturation point. This is power efficient but unfortunately adds non-linear distortions to the communication channel. The latters are very penalizing for high order modulations.In the literature, several equalization algorithms have been proposed to cope with the resulting non-linear communication channel. The most popular solution consists in using baseband Volterra series in order to build non-linear equalization filters. On the other hand, the Recurrent Neural Networks (RNNs), which come from the artificial neural network field, are also interesting candidates to generate such non-linear filters. But they are difficult to implement in practice due to the high complexity of their training. To simplify this task, the Echo State Network (ESN) paradigm has been proposed. It has the advantage of offering performances similar to classical RNNs but with a reduced complexity.The purpose of this work is, first, to compare this solution to the state-of-the-art baseband Volterra filters. We show that the classical ESN is able to reach the same performances, evaluated in terms of Bit Error Rate (BER), and has similar complexity. Secondly, we propose a new design for the ESN which achieves a strong reduction in complexity while conserving a similar BER.To compensate for the channel, the literature proposes to adapt the coefficients of these equalizers with the help of a training sequence in order to recover the transmitted constellation points. We show that, in such a case, the usual symbol detection criterion, based on Euclidean distances, is no longer optimal. For this reason, we first propose a new detection criterion which meets the Maximum Likelihood (ML) criterion. Secondly, we propose a modification of the equalizers training reference points in order to improve their performances and make the detection based on Euclidean distances optimal again. This last solution can offer a significant reduction of the BER without increasing the equalization and detection complexity. Only the new training reference points must be evaluated.In this work, we also explore the field of analog equalizers as different papers showed that the ESN is an interesting candidate for this purpose. It is a promising approach to reduce the equalizer complexity as the digital implementation is very challenging and power-hungry, in particular for high bandwidth communications. We numerically demonstrate that a dedicated analog optoelectronic implementation of the ESN can reach the state-of-the-art performance of digital equalizers. In addition, we show that it can reduce the required resolution of the Analog-to-Digital Converters (ADCs).Finally, a hardware demonstration of the digital solutions is proposed. For this purpose, we build a physical layer test bench which depicts a non-linear communication between two radios. We show that if we drive the transmitter power amplifier close to its saturation point, we can improve the communication range if the non-linear distortions are compensated for at the receiver. The transmitter and the receiver are implemented with Software Defined Radios (SDRs).
Doctorat en Sciences de l'ingénieur et technologie
info:eu-repo/semantics/nonPublished

La forte croissance des Technologies d'Information et de Communication (TIC) constitue un défi, tant pour les études qui portent sur la sociabilité que pour celles qui traitent des usages de ces technologies. Elle oblige en fait à réinterroger des méthodologies et des analyses sociologiques qui se sont jusqu'alors principalement fondées autour de la sociabilité en face-àface. Le travail présenté retrace l'historique des recherches conduites par l'auteur depuis dix ans sur les pratiques de communication outillées par les TIC. Il pose les hypothèses développées autour des liens entre la sociabilité et le téléphone fixe, puis il examine les effets de la popularisation des moyens de contact mobiles et individualisés tels que le téléphone cellulaire sur les pratiques de communication interpersonnelle. Il s'achève avec des questions méthodologiques et un regard sur des recherches plus récentes qui s'efforcent de saisir la sociabilité à travers l'ensemble des contextes et des moyens technologiques de communication largement diffusés ces dernières années. L'articulation entre médias de communication et sociabilités est modifiée par la transformation du paysage technologique actuel. Même s'ils ne les conditionnent ni ne les déterminent, les outils de communication posent les cadres d'interaction dans lesquels sont entretenus les liens sociaux. Les manières de construire, d'administrer et d'alimenter ces liens sont étroitement entrelacées avec l'outillage qui médiatise les contacts. Au même moment, une forte corrélation entre rencontres en face-à-face et appels échangés avec les proches est observée. Ce constat reste d'ailleurs valable pour l'ensemble des nouveaux outils de communication. Les recherches montrent que chaque nouveau service de communication adopté s'inscrit dans l'économie relationnelle globale, en augmentant le nombre des possibilités de tisser le lien. Il n'y a donc pas de substitution entre les différents outils de contact, mais des agencements continuels au fur et à mesure que les nouveaux instruments de communication apparaissent et sont insérés dans la partition qui fait vivre les liens interpersonnels. L'inscription des TIC dans les pratiques sociales est aujourd'hui si forte qu'il devient difficile de pouvoir analyser des interactions, des liens ou des réseaux sociaux, sans prendre en compte les outils techniques qui les épaulent, les orientent et les cadencent. En particulier, le passage vers les outils de communication mobiles et délocalisés, par rapport aux lieux habituels de présence outillée (maison, bureau.), transforme en partie notre accessibilité aux autres. Les nouveaux usages relationnels, lourdement instrumentés en outils de communication, favorisés par le recours aux dispositifs de communication portables, particulièrement adaptés à des enjeux de coordination, s'appuient sur le développement et le recours croissant aux messageries (email, SMS, IM). Même si ces technologies allègent les contraintes de disponibilité que les TIC font peser sur les acteurs en permettant une réponse différée aux sollicitations, la multiplication des échanges médiatisés fait croître la pression d'une nouvelle cadence relationnelle. Cette imbrication du " réel " et du " virtuel " dans la sociabilité de tous les jours risque de produire des formes de contrôle et des manières de gérer sa propre joignabilité inédites et à terme reconstruire les rythmes et les normes relationnels

South Africa the development of small tourism businesses are extremely vital for job creation and a development of a new economy. The South African tourism industry has to look at more innovative ways for marketing their products and services to develop the small tourism businesses. The arrival of web 2.0 led to the development and evolution of web-based communities, hosted services and web applications such as social networking sites. Social networking sites have encouraged new ways to communicate and share information on the web. When it comes to online networking, websites are commonly used. These websites are known as social networking sites and function as online communities on the internet. Social networking sites are currently one of the applications of Web 4.0 developments. This means creation by the majority and web participation a necessity. The importance of customer engagement enablement is recognised. Operating systems are in cloud-computing. The communication medium became social media systems and people sell everything via desktop, mobile, tablets and iTV. This study focuses on the Eastern Free State tourism destination and its development through social networks. The main aim of the study is to critically analyse the application and effective utilisation of social network site technologies within the Eastern Free State tourism industry and to explore this objective of social network applications used within the small businesses in Eastern Free State tourism industry. The empirical study was conducted by means of a field study using a structured questionnaire and interviews with key stakeholders. Data from 60 small tourism businesses were collected and a total of 55 businesses restricted to Eastern Free State Drakensberg were analysed in the process of collecting the peer-aided questionnaires. The biggest problems in the use of digital media are knowledge to develop a proper product that has measured marketing outcomes for the small business.
Thesis (MBA)--North-West University, Potchefstroom Campus, 2013.

Hybrid Networks employing wireless communication technologies have nowadays brought closer the vision of communication “anywhere, any time with anyone”. Such communication technologies consist of various standards, protocols, architectures, characteristics, models, devices, modulation and coding techniques. All these different technologies naturally may share some common characteristics, but there are also many important differences. New advances in these technologies are emerging very rapidly, with the advent of new models, characteristics, protocols and architectures. This rapid evolution imposes many challenges and issues to be addressed, and of particular importance are the interoperability issues of the following wireless technologies: Wireless Fidelity (Wi-Fi) IEEE802.11, Worldwide Interoperability for Microwave Access (WiMAX) IEEE 802.16, Single Channel per Carrier (SCPC), Digital Video Broadcasting of Satellite (DVB-S/DVB-S2), and Digital Video Broadcasting Return Channel through Satellite (DVB-RCS). Due to the differences amongst wireless technologies, these technologies do not generally interoperate easily with each other because of various interoperability and Quality of Service (QoS) issues. The aim of this study is to assess and investigate end-to-end interoperability issues and QoS requirements, such as bandwidth, delays, jitter, latency, packet loss, throughput, TCP performance, UDP performance, unicast and multicast services and availability, on hybrid wireless communication networks (employing both satellite broadband and terrestrial wireless technologies). The thesis provides an introduction to wireless communication technologies followed by a review of previous research studies on Hybrid Networks (both satellite and terrestrial wireless technologies, particularly Wi-Fi, WiMAX, DVB-RCS, and SCPC). Previous studies have discussed Wi-Fi, WiMAX, DVB-RCS, SCPC and 3G technologies and their standards as well as their properties and characteristics, such as operating frequency, bandwidth, data rate, basic configuration, coverage, power, interference, social issues, security problems, physical and MAC layer design and development issues. Although some previous studies provide valuable contributions to this area of research, they are limited to link layer characteristics, TCP performance, delay, bandwidth, capacity, data rate, and throughput. None of the studies cover all aspects of end-to-end interoperability issues and QoS requirements; such as bandwidth, delay, jitter, latency, packet loss, link performance, TCP and UDP performance, unicast and multicast performance, at end-to-end level, on Hybrid wireless networks. Interoperability issues are discussed in detail and a comparison of the different technologies and protocols was done using appropriate testing tools, assessing various performance measures including: bandwidth, delay, jitter, latency, packet loss, throughput and availability testing. The standards, protocol suite/ models and architectures for Wi-Fi, WiMAX, DVB-RCS, SCPC, alongside with different platforms and applications, are discussed and compared. Using a robust approach, which includes a new testing methodology and a generic test plan, the testing was conducted using various realistic test scenarios on real networks, comprising variable numbers and types of nodes. The data, traces, packets, and files were captured from various live scenarios and sites. The test results were analysed in order to measure and compare the characteristics of wireless technologies, devices, protocols and applications. The motivation of this research is to study all the end-to-end interoperability issues and Quality of Service requirements for rapidly growing Hybrid Networks in a comprehensive and systematic way. The significance of this research is that it is based on a comprehensive and systematic investigation of issues and facts, instead of hypothetical ideas/scenarios or simulations, which informed the design of a test methodology for empirical data gathering by real network testing, suitable for the measurement of hybrid network single-link or end-to-end issues using proven test tools. This systematic investigation of the issues encompasses an extensive series of tests measuring delay, jitter, packet loss, bandwidth, throughput, availability, performance of audio and video session, multicast and unicast performance, and stress testing. This testing covers most common test scenarios in hybrid networks and gives recommendations in achieving good end-to-end interoperability and QoS in hybrid networks. Contributions of study include the identification of gaps in the research, a description of interoperability issues, a comparison of most common test tools, the development of a generic test plan, a new testing process and methodology, analysis and network design recommendations for end-to-end interoperability issues and QoS requirements. This covers the complete cycle of this research. It is found that UDP is more suitable for hybrid wireless network as compared to TCP, particularly for the demanding applications considered, since TCP presents significant problems for multimedia and live traffic which requires strict QoS requirements on delay, jitter, packet loss and bandwidth. The main bottleneck for satellite communication is the delay of approximately 600 to 680 ms due to the long distance factor (and the finite speed of light) when communicating over geostationary satellites. The delay and packet loss can be controlled using various methods, such as traffic classification, traffic prioritization, congestion control, buffer management, using delay compensator, protocol compensator, developing automatic request technique, flow scheduling, and bandwidth allocation.

Les Réseaux de Capteurs Sans Fils (RCSFs) et les réseaux véhiculaires sont de plus en plus répandus, et déployés dans des domaines d’applications variés tels que la santé, la surveillance environnementale, les applications d’alerte d’accident, et les applications militaires. Cependant, ces réseaux peuvent être sujets à des attaques, ce qui empêche leur utilisation à grande échelle. Cette thèse étudie la sécurité des communications pour les réseaux de capteurs sans fils, et les communications inter-véhiculaires. Dans ce but, nous abordons quatre aspects importants. La première étude porte sur l’authentification des messages diffusés dans les réseaux de capteurs. Nous nous concentrons sur les principaux schémas à base de divulgation de clés d’authentification. Nous démontrons que le délai de divulgation de clé induit un délai d’authentification, ce qui pourrait conduire à une attaque de mémoire de déni de service. Nous proposons ensuite deux protocoles d’authentification de la source dans les RCSFs, pour surmonter la vulnérabilité des solutions existantes. Les schémas proposés garantissent la gestion efficace de la mémoire tampon du récepteur, en utilisant un mécanisme d’authentification par niveau, et une structure de Filtre de Bloom afin de réduire le coût de communication. Ensuite, nous validons nos protocoles en utilisant l’outil de vérification AVISPA, et nous les évaluons avec des expérimentations dans l’environment TinyOS. Nous confirmons que ces protocoles fournissent un service d’authentification de la source tout en respectant les contraintes de RCSFs. La seconde étude porte sur le problème de stockage au niveau des capteurs. Nous considérons en particulier l’attaque d’authentification différée “Delayed Authentication Compromise” (DAC) dans les RCSFs, qui permet à un attaquant d’utiliser une clé déjà divulguée pour signer d’autres messages. Nous montrons d’abord que les systèmes récemment proposés qui sont résistants également à l’attaque DAC sont vulnérables aussi à deux types d’attaques: attaque de permutation de commandes (où un adversaire prétend “permuter” deux messages au fil du temps), et l’attaque de rejet de commandes (où un adversaire semble “cacher” un message envoyé par la station de base). Nous proposons ensuite une nouvelle solution d’authentification. Notre analyse montre que notre solution est efficace pour détecter à la fois l’attaque de permutation de commandes et l’attaque de rejet de commandes, — et en même temps — est plus efficace (en termes de communication et de calcul) que les solutions existantes. xxiDans la troisième étude, nous considérons le problème de la sécurité de la gestion des clés dans les réseaux de capteurs. Nous présentons de nouveaux schémas d’authentification à base de clés symétriques qui présentent un faible coût d’authentification et de communication. Nos systèmes sont construits en intégrant un mécanisme de réputation, un filtre de Bloom, et un arbre binaire de clés pour la distribution et la mise à jour des clés d’authentification. Nos schémas d’authentification sont efficaces en matière de communication et de consommation de l’énergie. La quatrième étude porte sur la sécurité des communications véhiculaires. Nous nous concentrons sur les applications d’alerte d’accident. Nous analysons les menaces pour un ensemble d’algorithmes. Nous démontrons que ces systèmes sont vulnérables à l’attaque d’injection d’une fausse position, à l’attaque de rejeu de message d’alerte, et à l’attaque d’interruption de message d’alerte. Ensuite, nous proposons des contre-mesures à ces menaces. Nous avons donc proposé une solution qui est à la fois rapide et sécurisée pour les applications d’alerte d’accident : Un algorithme rapide et sécurisé pour la diffusion des messages en multi-saut (FS-MBA). Enfin, nous confirmons l’efficacité et la faisabilité des différents protocoles en effectuant un ensemble de simulations sous le simulateur NS-2
Wireless sensor and vehicular networks play an important role in critical military and civil applications, and pervade our daily life. However, security concerns constitute a potential stumbling block to the impeding wide deployment of sensor networks and vehicular communications. This dissertation studies communication security for Wireless Sensor Networks (WSNs), and vehicular communication. To this aim, we address four important aspects. The first study addresses broadcast authentication in WSNs. We focus on key disclosure based schemes. We demonstrate that key disclosure delay induces an authentication delay, which could lead to a memory DoS attack. We then propose two broadcastauthentication protocols for WSNs, which overcome the security vulnerability of existingsolutions. The proposed schemes guarantee the efficient management of receiver’s buffer, by employing a staggered authentication mechanism, and a Bloom filter data structure to reduce the communication overhead. We also validate our protocols under the AVISPA model checking tool, and we evaluate them with experiments under TinyOS. Our findings are that these protocols provide source authentication service while respecting the WSN constraints.The second study addresses the storage issue in WSNs, in particular the Delayed AuthenticationCompromise attack (DAC). We first demonstrate that recently proposed schemes, which also address the DAC issue are vulnerable to two kinds of attacks: switch command attack (where an adversary pretends to “switch” two messages over time), and drop command attack (where an adversary just pretends to “hide” a message sent from the broadcaster). As a countermeasure against these attacks, we propose a new solution for broadcast authentication. Our analysis shows that our solution is effective in detecting both switch command and drop command attack, and—at the same time—is more efficient (in terms of both communication and computation) than the state of the art solutions.In the third study, we address key management security in WSNs. We present novel symmetric-key-based authentication schemes which exhibit low computation and communication authentication overhead. Our schemes are built upon the integration of a reputation mechanism, a Bloom filter, and a key binary tree for the distribution and updating of the auxviii thentication keys. Our schemes are lightweight and efficient with respect to communication and energy overhead. The fourth study addresses security in vehicular communications. We focus on fast multi hop broadcast applications. We analyze the security threats of state of the art vehicular based safety applications. We demonstrate that these schemes are vulnerable to the position cheating attack, the replay broadcast message attack, and the interrupting forwarding attack. Then, we propose countermeasures for these threats. We hence propose a complete solution which is both fast and secure in broadcasting safety related messages: Fast and Secure Multi-hop Broadcast Algorithm (FS-MBA). Finally, we confirm the efficiency and feasibility of our proposals using an extensive set of simulations under NS-2 Simulator

The enabling technologies and the issues of next-generation millimeter-wave wireless access network and 100G long-haul optical transport network were developed and identified. To develop a simple and cost-effective millimeter-wave optical-wireless system, all-round research on the technical challenges of optical millimeter-wave generation, transmission impairments compensation, and simple base station design were discussed. Several radio-over-fiber systems were designed to simultaneously deliver multi-band wireless services on a single optical infrastructure, enabling converged system control and quality maintenance in central office. For the 100G optical transport network, the issues related to successful implementations of transmitter, fiber link, and receiver of a 112-Gb/s polarization-division multiplexing-quadrature phase shift keying (PDM-QPSK) system were comprehensively explored. The experimental results based on the constructed 112-Gb/s testbed indicated that careful dispersion management can effectively increase nonlinearity tolerance. Furthermore, the special emphasis on the two impairments of the 100G network with reconfigurable optical add-drop multiplexers: passband narrowing and in-band crosstalk, was studied. The results demonstrated that these impairments can be readily predicted with proper experimental and simulation efforts.

This research has been motivated primarily by a desire to extend and enrich existing research on women’s uses of information and communication technologies (ICTs) to manage relationships, and access and construct social support during their transitional midlife years. In doing so, this research addresses a gap in the literature on women’s consumption of such technologies. Since the late 1980s, when several landmark studies investigated women’s use of the telephone, there has been little systematic evaluation of the degree to which newer communication technologies have become integrated into women’s communication practices. Another key feature of this research is an examination of how ‘midlife’, as a stage of life characterised by several common transitions, is experienced by a group of women. These life experiences are modified by the availability of social support and, significantly for this research, by the communication conduits through which this support circulates. Given that midlife involves physical and emotional changes that may impact on a woman’s sense of self, this period of transition can be a source of stress. Numerous studies have identified the critical role social support plays in helping individuals cope with stress. For women, social support is commonly manifested through female networks, maintained through faceto- face encounters, and increasingly through mediated communication channels. In a region as geographically isolated as Western Australia, where over 27% of the population were born overseas, the importance of communication technologies in facilitating access to dispersed social support networks is arguably even more critical. The research procedure, drawing on a qualitative, interpretive methodological approach, involved 40 in-depth, one-on-one ethnographic interviews with women aged between 45 and 55. Initial findings indicated that while women are actively appropriating a range of online communication channels, there was a risk in limiting the research focus to women’s use of the Internet, in isolation from their broader communication practices. In particular, this research makes clear that one significant aspect of women’s uses of ICTs lies in how different communication channels meet the needs of women and their families at particular moments in their lives. At the midway mark in the lifecycle, many of the women interviewed are either consciously, or in some cases intuitively, employing particular communication channels to manage difficult or sensitive relationships; their choices often constrained by the communication needs and/or preferences of their aging parents and/or their own children. Despite such constraints, this research provides strong evidence to suggest that midlife women are as adept at strategically appropriating multiple communication technologies to satisfy their own needs, as are many younger people. This is manifested in a variety of ways, from women’s use of email as a safe conduit through which to maintain tenuous links with difficult siblings; to their strategic employment of email, instant messaging and webcam to foster a richer sense of connection with young adult children living thousands of kilometres away; through to their appropriation of a mix of ‘old’ and new channels such as face-to-face communication, the landline telephone, text messaging and email, as tools to help them manage their hectic lifestyles and sustain relationships with family and friends. Women’s active appropriation of multiple communication channels is therefore critical to the ongoing maintenance of relationships and, by extension, the health and emotional wellbeing not only of the women themselves, but also their loved ones and friends

This study discussed the effect of new information and communication technologies use on adolescents. The research also assessed whether gender and frequency of use of new information and communication technologies would interact to influence self-esteem and social support from family and friends.

Nowadays, the effective use of information and communication technologies plays a significant role in the educational process. The article is about the possibilities of using social networking for educational purposes.

L’émergence de véhicules aériens sans pilote, généralement appelés drones, petits et bon marché favorise leur utilisation dans le domaine des applications civiles. Ces drones sont équipés de différents capteurs et ont la capacité de communiquer via des liaisons sans fil et ont la particularité de se déplacer librement dans l’espace, révolutionnant la gestion des applications de surveillance. Un réseau ad hoc de drones, Flying Ad hoc Networks (FANET) en anglais, est composé d’une flotte de drones autonomes et est utilisé lors de missions dans des environnements hostiles pour la surveillance ou l’inspection de sites dangereux ou inconnus. Les FANETs peuvent être également utilisés pour suivre et filmer des événements spéciaux comme une course de vélos ou un match de football, dans ce cas les liaisons doivent garantir un minimum de qualité. Les FANETs nécessitent une attention particulière en ce qui concerne l’économie d’énergie des UAV dont les ressources en énergie sont limitées, mais aussi d’être immunisés contre des attaques malveillantes. Au cours de cette thèse, nous nous sommes concentrés sur le problème de suivi d’une cible mobile utilisant une flotte de drones pour la filmer. Étant donné que la cible se déplace, les drones doivent la suivre en continu, et une liaison vers la station terrestre doit être disponible. Dans ce contexte, nous proposons une solution qui permet la coordination d’un ensemble de drones afin de maintenir un chemin optimal entre la cible et la station terrestre. Notre solution se révèle efficace en matière de gain en temps et en énergie. Nous avons également proposé une solution basée sur des protocoles hiérarchiques pour économiser plus d’énergie dans le processus de communication avec la station terrestre. Nous avons également développé une autre solution qui permet d’économiser plus d’énergie en forçant les nœuds égoïstes à participer dans le réseau et d’assurer le relais de paquets lorsqu’ils sont sollicités. En effet, si un nœud égoïste refuse de router des paquets d’autres nœuds, cela induit une charge supplémentaire pour le reste des nœuds du réseau. Nous avons validé l’apport de l’ensemble de nos solutions par évaluation de performances à l’aide de simulations
The emergence of small and inexpensive Unmanned Aerial Vehicles (UAVs) promotes their use in several applications. UAVs are usually equipped with different sensors and have the ability to communicate via wireless connections. Their capability to fly freely in the space offers new opportunities to monitoring and tracking applications. A Flying Ad hoc Network (FANET) is composed of a fleet of autonomous UAVs and is used for monitoring applications in hostile environments, surveillance or site inspection. FANETs could also be used for filming special events such as bike races or soccer matches, so, the connections must guarantee a minimum of quality of service. In FANETs, saving energy of UAVs that have limited battery is very challenging and protecting the network from malicious attacks is even more difficult. In this thesis, we focus on tracking and filming a moving target using a fleet of UAVs. Since the target is moving, the UAVs have to follow it continuously, and a path to the ground station must be available. In this context, we propose an efficient solution that allows the coordination of the UAVs to maintain an optimal path between the target and the ground station. The proposed solution is time and energy efficient. We also propose a solution based on hierarchical protocols to save more energy in the communication process with the ground station. Another solution that allows energy saving is to force selfish nodes to participate in the network to route received packets towards their destination. Indeed, a selfish node is concerned only about its own welfare, refusing to route packets of other node, causing an extra charge for the rest of nodes in the network. We validate our solutions through simulation campaigns

Esta pesquisa se insere nas linhas de investigação do Centro de Pesquisa ATOPOS, da Escola de Comunicações e Artes da Universidade de São Paulo (ECA/USP) sobre os aspectos teóricos das mídias digitais. Seu objetivo é analisar o impacto das transformações midiáticas na sociedade, em especial o impacto causado pelas novas tecnologias digitais sobre as formas de organização social. Partindo de uma perspectiva que abandona a visão instrumentalista das tecnologias midiáticas, passando a considerálas como elementos ativos na construção da subjetividade humana e, por consequência, na forma como o homem se relaciona com o mundo, analisamos como a simbiose homemredes digitais proporciona uma experiência tecnosocial baseada na colaboração, isto é, no labor conjunto visando a ação. Nesse percurso, fazemos um resgate histórico sobre a relação transformações midiáticassociedade, estudamos o conceito de rede e dialogamos sobre o conceito de ação / ação social. Empiricamente, nos apoiamos em nossa trajetória através de experiências colaborativas em redes digitais, além de realizar pesquisas e observações específicas para este trabalho.
This research fits into the lines of investigation of the ATOPOS Research Center of Escola de Comunicação e Artes da Universidade de São Paulo [School of Communication and Arts of the University of São Paulo] (ECA/USP) on the theoretical aspects of digital media. Its goal is to analyze the impact of media changes in society, in particular the impact caused by new digital technologies on the forms of social organization. From a perspective that leaves the instrumentalist view of technology media, going to consider them as active elements in the construction of human subjectivity, and consequently, in how humans relate to the world, we analyze how the symbiosis of mandigital networks provides a technosocial experiment based on co-labor-a(c)tion, ie, in joint work aimed at the action. Along that way, we make a historical transformations on the mediasociety relationship, we studied the concept of networking and dialogue on the concept of action / social action. Empirically, we rely on our path through collaborative experiences in digital networks, and conduct research and observations specific to this work.

Dissertação para obtenção do Grau de Mestre em Engenharia Electrotécnica e de Computadores
The society that we live in faces today big demographic changes. Nowadays, peo-ple live longer, and it is expected that this trend will proceed. In 2000, there were already 420 million people with more than 65 years old, which correspond to about 7% of the world population. In 2050, it is expected that this number reaches 1500 million which corresponds to about 16% of the world population. Naturally, in these circumstances, the number of disabled people will increase as well. This context brings new challenges to the traditional health care systems in Portugal and in the rest of the world. There is an urgent need to search for new solutions that will allow people to live in the best possible way, in the latest stages of life. In order to fulfill this need, it is necessary to develop systems that allow to extend their life in their favorite environment, improving their safety, autonomy, mobility and welfare. Nowadays, information and communication technologies (ICT) offer new opportunities to provide care and assistance. Ambient Assisted Living (AAL), is such a paradigm, in which technology is used as a way to improve the independ-ence and welfare of aged or disabled people at their homes. This dissertation has the purpose of contributing to providing an answer to this necessity, associated to a development of an ecosystem for Ambient Assisted Living, associated to a business model and the search for the possibility of collabo-rative networks creation, in order to look for efficient and accessible solutions for AAL services provision.

L’augmentation exponentielle des équipements d’utilisateurs sans fil (UEs) et des services des réseaux associés aux déploiements actuels de cinquième génération (5G) pose plusieurs défis de conception sans précédent qui doivent être résolus avec l’avènement des futurs réseaux au-delà de la 5G. Plus précisément, la demande croissante de débits de données élevés ainsi que la nécessité de desservir un grand nombre d’appareils hétérogènes, allant des téléphones mobiles classiques aux objets connectés formant l’internet des objets (IoT), motivent l’étude de nouveaux schémas de traitement et de transmission du signal. À cet égard, les sorties multiples massives à entrées multiples (massive MIMO) sont une technologie d’accès bien établie, qui permet de desservir plusieurs dizaines d’UEs en utilisant lesmêmes ressources temps-fréquence au moyen de techniques de formation de faisceau hautement directionnelles. Cependant, le massive MIMO présente des problèmes d’évolutivité dans les scénarios accès massif où la population UE est composée d’un grand nombre de périphériques hétérogènes. En effet, si la disponibilité d’un grand nombre d’antennes dans les émetteurs-récepteurs massive MIMO apporte des gains de performances substantiels, elle augmente également considérablement la surcharge et la complexité du système. Plus précisément, la dimensionnalité élevée des canaux nécessite l’allocation de ressources temps-fréquence considérables pour acquérir les informations d’état de canal (CSI) et se traduit par de grandes opérations matricielles pour construire des précodeurs/décodeurs. De plus, dans le contexte de communications de multidiffusion comme, par exemple, la mise en cache périphérique sans fil ou la diffusion de messages critiques pour la mission, les techniques d’antennes multiples conventionnelles présentent des taux de disparition lorsque le nombre d’UEs augmente même dans le régime d’antenne massif. Enfin, le grand nombre de chaînes de radiofréquences (RF) associées aux émetteurs-récepteurs massive MIMO, qui sont utilisés pour contrer les pertes de propagation dans des environnements difficiles tels que, par exemple, à des fréquences d’ondes millimétriques (mmWave), se heurte au budget de puissance limité des appareils IoT. Dans cette thèse, nous proposons de nouvelles méthodes à antennes multiples évolutives pour l’amélioration des performances dans les scénarios d’intérêt susmentionnés. Plus précisément, nous décrivons le rôle fondamental joué par le CSI statistique qui peut être mis à profit pour réduire à la fois la complexité et la surcharge pour l’acquisition de CSI et pour la suppression des interférences multi-utilisateurs. En effet, lorsque les UEs sont équipés au moins de duex antennes, leurs propriétés de sélectivité spatiale peuvent être exploitées pour imposer une orthogonalité statistique parmi les transmissions interférentes. De plus, nous exploitons les communications de périphérique à périphérique (D2D) pour surmonter le goulot d’étranglement fondamental de la multidiffusion conventionnelle. En particulier, nous exploitons les capacités de précodage d’un émetteur multi-antennes pour sélectionner soigneusement les UEs dans des conditions de canal favorables, qui à leur tour agissent comme des relais opportunistes et retransmettent le message via les liaisons D2D. Enfin, dans le cadre des communications mmWave, nous explorons les avantages des surfaces intelligentes reconfigurables (RISs) récemment proposées, qui sont un catalyseur clé de l’innovation grâce à leur structure intrinsèquement passive qui permet de contrôler l’environnement de propagation et de contrer efficacement les pertes de propagation. En particulier, nous utilisons la formation de faisceaux passive au niveau du RIS, c’est-à-dire sans aucune dépense d’énergie significative, ainsi que la formation de faisceaux active conventionnelle au niveau de l’émetteur pour augmenter considérablement les performances du réseau
The exponential increase of wireless user equipments (UEs) and network services associated with current 5G deployments poses several unprecedented design challenges that need to be addressed with the advent of future beyond-5G networks and novel signal processing and transmission schemes. In this regard, massive MIMO is a well-established access technology, which allows to serve many tens of UEs using the same time-frequency resources. However, massive MIMO exhibits scalability issues in massive access scenarios where the UE population is composed of a large number of heterogeneous devices. In this thesis, we propose novel scalable multiple antenna methods for performance enhancement in several scenarios of interest. Specifically, we describe the fundamental role played by statistical channel state information (CSI) that can be leveraged for reduction of both complexity and overhead for CSI acquisition, and for multiuser interference suppression. Moreover, we exploit device-to-device communications to overcome the fundamental bottleneck of conventional multicasting. Lastly, in the context of millimiter wave communications, we explore the benefits of the recently proposed reconfigurable intelligent surfaces (RISs). Thanks to their inherently passive structure, RISs allow to control the propagation environment and effectively counteract propagation losses and substantially increase the network performance

Par leur capacité à créer, traiter et transmettre l’information en temps réel, les TIC jouent aujourd’hui un rôle majeur dans la structuration et le développement des territoires. La présente thèse vise à étudier la relation entre les TIC et les transformations de la forme urbaine du Grand Caire. Pour ce faire, la thèse implique une approche multidisciplinaire qui conjugue les deux méthodes quantitative et qualitative ; elle s’appuie sur le modèle de l’« urbanisme des réseaux » pour décomposer les TIC en trois niveaux : infrastructures, technologies de l’information et usages. Plusieurs ressources sont utilisées : rapports, articles et ouvrages spécialisés, données du terrain et ressources Internet y compris les Big data. Les principaux résultats sont les suivants : la distribution des réseaux des TIC (infrastructures, technologies de l’information et usages) a dessiné une zone étendue, un continuum, qui relie les grandes centralités formées pendant plusieurs périodes historiques du Grand Caire. En outre, les TIC, avec d’autres facteurs, ont mené à la formation dans la banlieue sud d’un centre économique/résidentiel, excentré et non planifié, le premier de ce type dans l’histoire millénaire du Grand Caire. Enfin, les résultats ont montré un rôle important des résidences fermées ; ces dernières semblent trouver dans les TIC le moyen pour mieux réaliser leur objectif : permettre de vivre et travailler au Grand Caire sans affronter les maux de son espace central. Globalement, Les TIC, malgré leur capacité à alléger plusieurs contraintes spatiales, sont parmi les facteurs qui ont consolidé la forme urbaine actuelle du Grand Caire avec tous ses problèmes majeurs
With their ability to create, process and transmit information in real time, ICT are playing today a major role in the structuring and development of urban spaces. The present thesis aims to study the relationship between ICT and the transformations of the Greater Cairo’s urban form. To that end, the thesis draws on a multidisciplinary approach that combines quantitative and qualitative methods; it is based on the model of "Urbanism of networks" that divides ICT networks into three levels: infrastructures, information technologies and uses. Many resources are used in this study: reports, specialised books and articles, data collected from the field and various Internet resources including the Big Data. The main results are as follows: at the metropolitan scale, the distribution of ICT networks (infrastructures, information technologies and uses) has drawn an extended area, a continuum, which connects the main urban centers formed during the several historical periods of Greater Cairo. Moreover, ICT, among other factors, have led to the formation in the southern suburb of an eccentric, unplanned economic/residential center, the first of its kind in the millennial history of Greater Cairo. Finally, the results showed an important role of the gated communities, these latter seem to find in ICT the way to better realise their objective: to allow living and working in Greater Cairo without facing the disadvantages of its central space. Overall, ICT, despite their ability to alleviate many spatial constraints, are among the factors that shaped the current urban form of Greater Cairo with all its major problems

In this thesis, I ask how our understanding of human relations carries implications for the way we understand the affordances of communication technology on human relations. To this end, I examine and compare two opposed perspectives of human relations and social life. The first perspective, networked individualism, is a version of network theory that begins with a foundation of agentic individuals who actively construct and manage their social worlds. Levinasian relationalism, the second perspective, offers a contrasting view that sees human relations as constitutive of human subjectivity. In comparing these two perspectives, I argue that networked individualism is an inadequate framework inasmuch as its ontological assertions prevent it from seeing some of the significant affordances of technology on human relations, and I suggest that Levinasian relationalism is a viable alternative.

Cette thèse étudie les problèmes d’optimisation bi-objectifs des communications dans les réseaux de capteurs hétérogènes du point de vue de la portée de transmission. Le premier critère considéré est nécessairement l'énergie qu’il s’agit d'économiser pour maximiser la durée de vie du réseau. Le second critère, primordial dans le cas des applications en temps réel, est le délai d'acheminement des données. Pour résoudre le problème d’optimalité de la diffusion, nous proposons une formulation en nombres entiers, un algorithme d’approximation, une méta-heuristique et une heuristique permettant de trouver ou s’approcher de l’optimal pour les objectifs considérés.Pour le cas du routage, nous proposons une approche cross-layer via un programme linéaire en nombre entiers entre les couches MAC et Liaison de données permettant de calculer l'optimal et ainsi d'avoir un point de comparaison pour les futures heuristiques ayant les mêmes objectifs
This thesis studies the problems of bi-objective optimization of communications in heterogeneous wireless sensor networks from the point of view of the transmission range. The first criterion considered is necessarily the energy consumption that needs to be reduced in order to maximize the network lifetime. The second criterion is the data transmission delay, which is essential for real-time applications.To solve the optimality problem of the broadcast, we propose an integer linear program, an approximation algorithm, a meta-heuristic and a heuristic. All these techniques allow us to find or to approximate the optimal solutions for the considered objectives.For the routing case, we propose a cross-layer approach via an integer linear program between the MAC and Data Link layers. Our method calculates the optimal solution, which represents a point of comparison for future heuristics having the same goals

Les réseaux de capteurs ont créé un domaine de recherche très intéressant avec un champs d'applications très large. L'assistance aux personnes est notamment une des nombreux champs potentiels. Les contraintes de ce type de réseaux sont nombreuses et nécessitent des mécanismes spécifiques. Les problématiques de consommation d'énergie et de sécurité sont particulièrement importantes et ont fait l'objet de travaux spécifiques. La thématique de l'assistance aux personnes impose notamment des contraintes de robustesse et de fiabilité des communications. Le but de ces travaux de recherche est de définir diverses solutions permettant de répondre à ces problématiques. Ces travaux se décomposent en trois parties. Dans un premier temps, une plate-forme de communications basée sur les réseaux personnels PAN a été définie. Cette plate-forme a été développée et intégrée dans une station de métro Parisienne. Une modélisation de cette plate-forme ainsi qu'une analyse des observations et des résultats issus de cette intégration nous ont permis d'identifier les faiblesses de l'architecture et des technologies mises en œuvre. Dans un deuxième temps, nous avons développé diverses solutions permettant de fiabiliser cette plate-forme. En particulier, nous avons conçu un algorithme d'ordonnancement permettant de réduire la consommation d'énergie dans les réseaux capteurs par l'utilisation d'une analyse sémantique des données. Nous avons ensuite proposé une architecture de sécurité, Tiny 3-TLS, qui permet de sécurisé les communications entre un capteur et une entité située sur un réseau disjoint. Enfin, nous nous sommes intéressés aux communications entre cette plate-forme et les terminaux mobiles. L'aspect fiabilité a en particulier fait l'objet de travaux spécifiques. C'est pourquoi dans un troisième temps, nous avons proposé une solution de routage définissant une nouvelle métrique. Nous avons ensuite proposé un protocole coopératif permettant un apport de fiabilité dans les communications
Wireless Sensors Networks is a very active research area with a very large scope of possible application. In particular, assistance to person is one of the promising applications. The constraints in this kind of networks are strong and needs of specifics mechanisms. Energy consumption and security are particularly important and are subject of several works. Assistance to person set some robustness constraints and communications reliability. The goal of these works is to define several solutions to answer to these problematic. This work has been split in three different parts. First, a communication platform based on Personal Network techniques was defined. This platform was design, develop and install in a Paris metro station. We made an analytical model of our platform to perform an analysis of its performances. This analysis and the results from the platform installation itself allow us to clearly define the architecture weaknesses and the technologies drawbacks. Second, we developed several solutions to bring reliability to the platform. First, we designed a scheduling algorithm allowing to reduce the bandwidth utilization. This algorithm uses a semantic data analysis to help the data scheduling. Then, we define a solution bringing security to the communications between a sensor node and a remote monitoring terminal. This solution allows to establish a secure end-to-end tunnel between two entities in an heterogeneous network. At last, we were interested to the communications between the platform and the mobile terminal. We focus our work on the reliability aspect of the communications. So, in the last part of this thesis, we suggest a routing protocol using a metric based on the RSSI. Then, we define a cooperative protocol bringing more reliability to the communications

The civil rights and other social justice movements, such as the fight against child sex trafficking are examples of an informal context where information and communications technologies (ICTs) have been actively applied in hopes of furthering social justice causes. But while we see that informally organized, grassroots groups have shown considerable interest in ICTs, the actual effectiveness of ICTs for these groups remains largely unknown. This is particularly so when combining both the complexity of the technology landscape and large grassroots interorganizational networks. Given the enormous challenge of social justice issues, there are pressing needs that go beyond connecting more just individuals to help nonprofits. A central need of nonprofit social justice organizations is the connection and coordination of many different groups into interorganizational networks (or groups of groups). In my research, I conducted an in-depth qualitative study of such a network engaged in fighting child sex trafficking. In doing so, I have identified some of the challenges of information sharing and coordination in this context. I gained insight into their information sharing needs and practices for connecting within an interorganizational network. I also conducted a design exploration by building a technology intervention to understand how ICTs can better accommodate the interorganizational needs of information sharing for connecting. My research findings point towards an initial framework in understanding information sharing technologies for informal interorganizational networks.

Au cours des dernières décennies, l'utilisation généralisée des technologies numériques de communication dans la vie quotidienne a donné lieu à une nouvelle relation entre l'individu et le territoire. Cette relation, dans laquelle les différents acteurs sont de plus en plus intégrés, surpasse l'ancien paradigme dichotomique caractérisé par la relation l'homme versus la nature. De cette façon, une nouvelle notion d'environnement, interactif et intégrant de l'espace social surgit, résultat de la représentation technologique de la nature et du dialogue favorisé par les réseaux numériques avec le territoire. L'objectif général de cette recherche est d'étudier le phénomène imaginaire écologique contemporain à partir de la perspective de la contribution de nouvelles technologies de communication numérique aux formes de représentation de la nature et de l'interaction avec le territoire. À cette fin, les voies et moyens d'interaction entre les individus, les technologies de communication numérique et le territoire seront étudiés, compte tenu des exemples de l'utilisation pratique des technologies numériques déjà consolidés. D'après une étude participative sur les réseaux numériques, ainsi que des études de cas, nous avons l'intention d'approfondir l'étude sur la contribution des réseaux numériques comme un territoire informatif ouvert pour les changements par rapport à la sociabilité contemporaine et l'imaginaire écologique contemporain
In recent decades, the widespread use of digital communication technologies in daily life gave rise to a new relationship between individual and territory. This relationship, in which different actors are increasingly integrated, surpasses the old dichotomous paradigm characterized by the man versus nature's relationship. Therefore, a new notion of environment, interactive and member of the social space is born as a result of technological representation of nature and the dialogue fostered by digital networks with the territory. The overall objective of this research is to investigate the contemporary ecological imaginary phenomenon from the perspective of the contribution of new digital communication technologies to the forms of representation of nature and interaction with the territory. To this end, the ways and means of interaction between individuals, digital communication technologies and territory will be studied, considering examples of practical use of digital technologies already consolidated. From a participatory study on digital networks, as well as case studies, we intend to further study on the contribution of digital networks as an open informative territory to changes in relation to contemporary sociability and contemporary ecological imaginary

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This is the ninth workshop to be organised under the postgraduate programmes in electrical and electronic engineering (EEE). The workshop concludes the Research Seminar Series, which has provided a platform for disseminating the latest research activities in related technologies through its weekly seminars. The EEE courses cover a broad range of technologies and this is reflected in the variety of topics presented during the workshop. In total, forty-four papers have been selected for the proceedings, which have been divided into eight sections. The workshop aims to be as close to a `real¿ event as possible. Hence, authors have responded to a Call for Papers with an abstract, prior to the submission of the final paper. This has been a novel experience for many, if not all of the contributors. As usual, authors have taken up the challenge with enthusiasm, resulting in a collection of papers that reflects today¿s research challenges.
School of Engineering, Design and Technology

Scania is increasing its production by improving its efficiency. The company is striving to achieve its new productivity goals without making large investments. In large organizations such as Scania there are many competent and skilled employees. However, since many of their offices are located worldwide communication is not always efficient and optimal. The purpose of this thesis is to show the potential benefits when implementing and operating online social networks within global organizations including Scania. Through empirical studies of global organizations which have utilized online social networks for a relatively long period this study intends to collect information which can help generate knowledge about the implementation and operation of online social networks. Our research revealed that important aspects of the implementation of an organization's online social network are knowledge management, dissemination, social ties and links between micro-and macro-networks. Thereby we concluded that online social networks lead to the creation of benefits for the individual as well as for the organization. Based on the theoretical framework and empirical evidence gathered in this study, we have concluded that an implemented model of an online social network fosters such benefits as improved communication channels and increased efficiency in the workplace.

Cette thèse a pour but d'évaluer la performance théorique des approches coopératives pour la fiabilisation des transmissions dans les réseaux autour du corps humain. Ces réseaux sont formés d'un nombre limité de capteurs communicants disposés sur et dans le corps. Les techniques de coopération dans les réseaux de cette taille sont extrêmement dépendantes de l'information disponible quand à la qualité des canaux de communication au moment de la transmission. Sous une hypothèse de connaissance de la valeur moyenne à moyen et long terme de l'affaiblissement de ces canaux, nous dérivons une approximation du taux d'erreur paquet de bout en bout pour des techniques de relayage. Nous présentons également, pour certains de ces modèles, une allocation de puissance asymptotiquement optimale, fournissant un gain sur une large plage des puissances d'émission. En supposant ensuite que les noeuds ont une connaissance parfaite de l'état du réseau, nous étudions la capacité de Shannon sur des canaux à relais, et des canaux comprenant deux émetteurs coopérant entre eux. Pour ces deux modèles, nous montrons que lorsque l'on cherche à optimiser la répartition de puissance totale disponible à l'émission, l'étude se réduit à celle d'un modèle de canal équivalent simplifiant grandement l'analyse de la capacité et fournissant des solutions analytiques aux problèmes d'allocation de ressources. Nous présentons enfin une plate-forme de mesures pour les réseaux autour du corps humain, permettant de relever de manière quasi-simultanée l'intégralité des affaiblissements des liens entre les nœuds du réseau. Cette plateforme nous permet de traiter de la stabilité de ces liens et de la validité de l'hypothèse de réciprocité. Nous évaluons également la corrélation spatiale de l'affaiblissement des liens et nous montrons en particulier que celle-ci varie fortement au cours du mouvement, mais de façon suffisamment lente pour être estimée au fil de l'eau.

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Recent years have witnessed the emergence of new communication techniques in Computer Science that use both wireless technologies and self-organizing features. Their combination eliminates the need for using pre-defined wired structures and prior configurations. In this work, we develop a simulated version, using the network simulator 3 (ns-3), of the Heterogeneous Technologies Routing (HTR) framework that is suitable for interconnecting devices in a heterogeneous ad hoc network, extending its supported heterogeneous technologies with the addition of WiMAX and LTE devices, proposes an extension to enable multipath routing over this framework and investigates the impact of tuning routing parameters on convergence interval and energy consumption. Although a large number of works exist that investigate the tuning of routing parameter settings, to the best of our knowledge, none of them investigate the impact of these on protocol convergence and energy consumption. Multipath HTR routing, the extension we propose, offers several benefits such as load balancing, fault tolerance, routing loop prevention, energy-conservation, low end-to-end delay, and congestion avoidance, among others. This work performs a comparative analysis of the proposed HTR extension, with the baseline HTR, and the widely used Optimized Link State Routing (OLSR) protocol. Moreover, we investigate the impacts of tuning the HELLO refresh interval and perform a comparative analysis of the tuned HTR with the OLSR protocol. Both evaluations are validated through the simulation of heterogeneous technologies such as WiMAX, 3GPP LTE and Wi-Fi. Results show that the multipath extension effectively improves the data delivery ratio, and reduces the end-to-end delay without major impact on network energy consumption. For the tuned HTR, results show that varying the HELLO refresh interval can improve the convergence of the protocol and reduce the energy consumption.
Recentemente, novas técnicas de comunicação surgiram que usam tecnologia sem fio e são capazes de se autoconfigurar. A combinação desses fatores elimina a necessidade de utilizar estruturas cabeadas e configurações pré-definidas. Neste trabalho, o autor desenvolve uma versão simulada, através do simulador de rede “network Simulator 3” (ns-3), do arcabouço “Heterogeneous Technologies Routing” (HTR), que se propõe à interconectar dispositivos em redes heterogêneas ad hoc, estendendo o seu suporte às tecnologias heterogêneas com a adição de dispositivos WiMAX e LTE, propõe uma extensão para fornecer um roteamento baseado em múltiplos caminhos (“Multipath”) e investiga o impacto de modificar os parâmetros de configuração do roteamento no tempo de convergência da rede e consumo de energia. Apesar de um grande número de obras existentes que investigam o impacto da mudança de parâmetros de configuração do roteamento, no meu conhecimento, nenhum deles investiga o impacto destes no tempo de convergência do protocolo e consumo de energia. O “Multipath HTR”, a extensão proposta, oferece vários benefícios como balanceamento de carga, tolerância a falhas, prevenção de “loops” de roteamento, conservação de energia, baixo atraso fim-a-fim, e evita o congestionamento, entre outros. Este trabalho faz uma análise comparativa da extensão ao HTR proposta, com a base do HTR, e o protocolo amplamente utilizado “Optimized Link State Routing” (OLSR). Além disso, o esse trabalho investiga o impacto de variar o intervalo de envio de mensagens de HELLO e realiza uma análise comparativa do HTR modificado (“Tuned HTR”) com o protocolo OLSR. As duas avaliações são realizadas através de simulação usando tecnologias heterogêneas como WiMAX, 3GPP LTE e Wi-Fi. Resultados mostram que a extensão de múltiplos caminhos proposta melhora a taxa de transmissão de dados, e reduz o atraso fim-a-fim sem maiores impactos no consumo de energia da rede. Para o “Tuned HTR”, resultados mostram que a variação do intervalo de envio de mensagens de HELLO pode melhorar a convergência do protocolo e reduz o consumo de energia.

This study examines young people’s internet access and use in nine locations in Queensland, Australia. The primary aim of the research is to assess if internet use supports young people’s social inclusion: that is, if internet use supports young people to participate in society in ways they have most reason to value. The research findings demonstrate that the digital divide in Queensland – the gap between citizens with and without access to ICTs – continues to inhibit young people’s ability to participate online. This divide is embedded within historic, economic, social and cultural inequalities. To address this, this study proposes that a digital inclusion framework, founded on the concept of social inclusion, offers the Australian federal and state governments an opportunity to extend digital divide policies so that they connect with and complement broader social policy goals. The research outcomes also illustrate that creative uses of online networks provide a powerful means through which young people can participate in a networked society. While young people’s access to a range of ICTs impacts on their ability to use online networks, gradations of use, social networks and informal learning contexts frequently act as mediators to support effective internet use. This study contends that by understanding the social benefits of young people’s online network use and the role that mediators play in different environments, we can move towards a policy framework that supports equitable opportunities for young people’s digital inclusion.

This study examines young people’s internet access and use in nine locations in Queensland, Australia. The primary aim of the research is to assess if internet use supports young people’s social inclusion: that is, if internet use supports young people to participate in society in ways they have most reason to value. The research findings demonstrate that the digital divide in Queensland – the gap between citizens with and without access to ICTs – continues to inhibit young people’s ability to participate online. This divide is embedded within historic, economic, social and cultural inequalities. To address this, this study proposes that a digital inclusion framework, founded on the concept of social inclusion, offers the Australian federal and state governments an opportunity to extend digital divide policies so that they connect with and complement broader social policy goals. The research outcomes also illustrate that creative uses of online networks provide a powerful means through which young people can participate in a networked society. While young people’s access to a range of ICTs impacts on their ability to use online networks, gradations of use, social networks and informal learning contexts frequently act as mediators to support effective internet use. This study contends that by understanding the social benefits of young people’s online network use and the role that mediators play in different environments, we can move towards a policy framework that supports equitable opportunities for young people’s digital inclusion.