Dissertations / Theses on the topic 'Cross-Layer Design PHY/MAC'

The latestWLAN standard, known as IEEE 802.11n, has notably increased the network capacity with respect to its predecessors thanks to the incorporation of the multipleinput multiple-output (MIMO) technology. Nonetheless, the new amendment, as its previous ones, does not specify how crucial configuration mechanisms, most notably the adaptive modulation and coding (AMC) algorithm should be implemented. The AMC process has proved essential to fully exploit the system resources in light of varying channel conditions. In this dissertation, a closed-loop AMC technique, referred to as fast link adaption (FLA) algorithm, that effectively selects themodulation and coding scheme (MCS) for multicarriermultiantennaWLAN networks is proposed. The FLA algorithm determines the MCS that maximizes the throughput while satisfying a quality of service (QoS) constraint, usually defined in the form of an objective packet error rate (PER). To this end, FLA uses a packet/bit error rate prediction methodology based on the exponential effective SNRmetric (EESM). The FLA algorithm performance has been evaluated under IEEE 802.11n systems that thanks to the incorporation of a feedbackmechanismare able to implement closed- loop AMC mechanisms. Initially, this AMC technique relies only on physical layer information but it is subsequently extended to also take into account themediumaccess control (MAC) sublayer performance. At the physical layer, the FLA algorithm has demonstrated its effectivity by performing very close to optimality in terms of throughput, while satisfying a prescribed PER constraint. The FLA algorithm has also been evaluated using imperfect channel information. It has been observed that the proposed FLA technique is rather robust against imperfect channel information, and only in highly-frequency selective channels, imperfect channel knowledge causes a noticeable degradation in throughput. At the MAC sublayer, the FLA algorithm has been complemented with a timeout strategy that weighs down the influence of the available channel information as this becomes outdated. This channel information outdate is caused by the MAC sublayer whose user multiplexing policy potentially results in large delays between acquiring the instant in which the channel state information is acquired and that in which the channel is accessed. Results demonstrate the superiority of FLA when compared to open-loop algorithms under saturated and non-saturated conditions and irrespective of the packet length, number of users, protocol (CSMA/CA or CDMA/E2CA) and access scheme (Basic Access or RTS/CTS). Additionally, several analytical models have been developed to estimate the system performance at the MAC sublayer. These models account for all operational details of the IEEE 802.11n MAC sublayer, such as finite number of retries, anomalous slot or channel errors. In particular, a semi-analytical model that assesses the MAC layer throughput under saturated conditions, considering the AMC performance is first introduced. Then, an analytical model that allows the evaluation of the QoS performance under non-saturated conditions is presented. This model focuses on single MCS and it is able to accurately predict very important system performance metrics such as blocking probability, delay, probability of discard or goodput thanks to the consideration of the finite queues on each station. Finally, the previous non-saturated analytical approach is used to define a semi-analytical model in order to estimate the system performance when considering AMC algorithms (i.e. whenmultiple MCSs are available).
La darrera versió de l’estàndard deWLAN, anomenada IEEE 802.11n, ha augmentat la seva capacitat notablement en relació als sistemes anteriors gràcies a la incorporació de la tecnologia de múltiples antenes en transmissió i recepció (MIMO). No obstant això, la nova proposta, al igual que les anteriors, segueix sense especificar com s’han d’implementar elsmecanismes de configuraciómés crucials, un dels quals és l’algoritme de codificació imodulació adaptativa (AMC). Aquests algoritmes ja han demostrat la seva importància a l’hora demaximitzar el rendiment del sistema tenint en compte les condicions canviants del canal. En aquesta tesis s’ha proposat un algoritme AMC de llaç tancat, anomenat adaptació ràpida de l’enllaç (FLA), que selecciona eficientment l’esquema demodulació i codificació adaptativa per xarxes WLAN basades en arquitectures multiportadora multiantena. L’algoritme FLA determina el mode de transmissió capaç de maximitzar el throughput per les condicions de canal actuals, mentre satisfà un requisit de qualitat de servei en forma de taxa d’error per paquet (PER). FLA utilitza una metodologia de predicció de PER basada en l’estimació de la relació senyal renou (SNR) efectiva exponencial (EESM). El rendiment de l’algoritme FLA ha estat avaluat en sistemes IEEE 802.11n, ja que aquests, gràcies a la incorporació d’unmecanisme de realimentació demodes de transmissió, poden adoptar solucions AMC de llaç tancat. En una primera part, l’estudi s’ha centrat a la capa física i després s’ha estès a la subcapa MAC. A la capa física s’ha demostrat l’efectivitat de l’algoritme FLA aconseguint un rendiment molt proper al que ens proporcionaria un esquema AMC òptim en termes de throughput, alhora que es satisfan els requisits de PER objectiu. L’algoritme FLA també ha estat avaluat utilitzant informació imperfecte del canal. S’ha vist que l’algoritme FLA proposat és robust en front dels efectes d’estimació imperfecte del canal, i només en canals altament selectius en freqüència, la informació imperfecte del canal provoca una davallada en el rendiment en termes de throughput. A la subcapa MAC, l’algoritme FLA ha estat complementat amb una estratègia de temps d’espera que disminueix la dependència amb la informació de canal disponible a mesura que aquesta va quedant desfassada respecte de l’estat actual. Aquesta informació de canal desfassada és conseqüència de la subcapa MAC que degut a la multiplexació d’usuaris introdueix grans retards entre que es determina el mode de transmissió més adequat i la seva utilització per a l’accés al canal. Els resultats obtinguts han demostrat la superioritat de FLA respecte d’altres algoritmes de llaç obert en condicions de saturació i de no saturació, i independentment de la longitud de paquet, nombre d’usuaris, protocol (CSMA/CA i CSMA/E2CA) i esquema d’accés (Basic Access i RTS/CTS). Amés, s’han desenvolupat diversosmodels analítics per tal d’estimar el rendiment del sistema a la subcapa MAC. Aquests models consideren tots els detalls de funcionament de la subcapaMAC del 802.11n, comper exemple un nombre finit de retransmissions de cada paquet, l’slot anòmal o els errors introduïts pel canal. Inicialment s’ha proposat unmodel semi-analític que determina el throughtput en condicions de saturació, considerant el rendiment dels algoritmes AMC. Després s’ha presentat un model analític que estima el rendiment del sistema per condicions de no saturació, mitjançat elmodelat de cues finites a cada estació. Aquestmodel consideramodes de transmissió fixes i és capaç de determinar de manera molt precisa mètriques de rendimentmolt importants comsón la probabilitat de bloqueig de cada estació, el retard mitjà del paquets, la probabilitat de descart o la mesura del goodput. Finalment, el model analític de no saturació s’ha utilitzat per definir un model semi-analític per tal d’estimar el rendiment del sistema quan es considera l’ús d’algoritmes AMC.

Le protocole MAC du standard IEEE 802.11p dédié aux réseaux véhiculaires interdit les transmissions simultanées dans une même zone de détection afin d’éviter d’éventuelles interférences entre les véhicules voisins. Cette interdiction entraîne un blocage temporaire de réception de données, ce qui diminue le débit global du réseau. Pour résoudre ce problème, nous proposons dans cette thèse une architecture cross-layer PHY/MAC basée sur un algorithme de sélection d’antennes émettrices et un protocole MAC dédié afin de réduire le blocage. Ce cross-layer permet au récepteur de choisir la meilleure combinaison d’antennes émettrices pour améliorer le débit utile normalisé de chaque lien V2V. L’algorithme est présenté avec une méthode de détection multi-utilisateurs. Cette méthode annule les interférences entre voisins et permet à plusieurs véhicules d’émettre des données simultanément. Le protocole MAC associé assure la coordination entre les véhicules durant les communications. Les résultats de simulation montrent une amélioration du débit utile normalisé du réseau en comparaison au standard actuel. Néanmoins, ces bonnes performances diminuent avec l’augmentation de la densité véhiculaire. Pour pallier à cette baisse, nous proposons de joindre à la première solution une nouvelle architecture crosslayer PHY/MAC. Cette architecture est basée sur un algorithme d’adaptation de la puissance émise en fonction de la densité de voisinage du récepteur. Elle est également accompagnée par un protocole MAC dédié. Les résultats de simulation montrent que cette solution permet à plus de véhicules de communiquer simultanément et ainsi améliore significativement le débit utile normalisé notamment dans les réseaux véhiculaires denses
The MAC protocol IEEE 802.11p, dedicated to vehicular ad-hoc networks VANETs, prohibits simultaneous transmissions in the same detection area, in order to avoid interference between neighboring vehicles. This prohibition causes a temporary data reception blocking, which reduces the network throughput. To reduce this adverse impact, we propose in this thesis a cross-layer design PHY/MAC based on a transmit antennas selection algorithm jointly with a dedicated MAC protocol. This design allows receivers to select the best combination of transmit antennas to improve the throughput of each V2V link. The algorithm is presented with a multi-user detection method, which cancels neighbor’s interference and allows vehicles to transmit data simultaneously. The associated MAC protocol ensures the coordination between vehicles during the simultaneous transmission period. The simulation results show a significant network throughput improvement compared to the conventional case. However, this improvement is less important in dense VANETs. For this purpose, we propose to join a cross-layer design PHY/MAC based on a transmit power adaptation algorithm. This design allows transmitters to choice the adequate power level based on corresponding receivers density. The simulation results show that this solution allows more vehicles to communicate simultaneously and thus improves the network throughput, in particular in dense VANETs

In this dissertation, we investigate the performance of point-to-point wireless ad hoc networks. The performance evaluation is performed in terms of outage probability, which is defined as the probability of receiving messages correctly. This metric is stochastic, and closely related to the ubiquitous notions of throughput and transmission capacity. In order to make the analysis tractable, we establish a proper analytical framework, and make reasonable approximations in the derivations. Approaching the design of ad hoc networks through the medium access control (MAC) layer, analytical expressions are obtained for the outage probability of a given mobile ad hoc network in an unbounded (infinite) region. We consider the following MAC protocols: slotted and unslotted ALOHA, carrier sensing multiple access (CSMA) with transmitter sensing, and CSMA with receiver sensing. Moreover, we investigate the impact of various ad hoc network characteristics on the outage probability. In particular, we add fading to the path loss channel model and measure the degradation it causes; we bound the network domain to investigate the edge effects; and we introduce fading within a bounded network. In each case, new outage probability expressions are derived. Having established a fundamental understanding of the behavior of various flavors of mobile ad hoc networks, we propose MAC layer techniques to improve the performance. Three schemes are proposed: 1) optimization of the sensing threshold in CSMA, 2) addition of a feedback channel between each transmitter and its receiver for improving the decision making stage of CSMA, and 3) introduction of bandwidth partitioning. In each scenario, new outage probability expressions are derived both in nonfading and fading networks. Finally, we step into the domain of multiple input multiple output (MIMO) communications, allowing for multiple antennas at transmitters and receivers. Within an ad hoc setting with no channel state information (CSI) at the transmitters, lower and upper bounds are derived on the outage probability and ergodic capacity. In the particular case of multiple input single output (MISO) channels, different transmission schemes are proposed in order to achieve the best usage of transmit antennas. With the addition of CSI at the transmitters, we consider various interference management schemes, with focus on the high SNR regime. We propose a binary power control scheme that ensures an increase in the sum rate of the MIMO network with many users, and that operates in a distributed manner, regardless of the interference management algorithm applied.

Les réseaux de capteurs sans fil (WSN) ont attiré un grand intérêt dans la dernière décennie, et ont apporté des solutions dans un nombre croissant d’applications. Toutefois, certaines d’entre elles restent irréalisables en raison de forts points de blocage non résolus, comme un manque de synchronisation entre les prises de mesures, ainsi que des débits de données trop faibles. Ce travail apporte une solution à ces deux points majeurs via la conception d’un noeud communicant sans fil spécifique. Celle ci, basée sur la conception croisée, utilise les propriétés temporelles des modulations UltraLarge Bande (UWB) pour permettre une synchronisation très précise ainsi qu’un débit de données élevé. Notre démonstrateur ASIC basé sur ces travaux permet une précision de synchronisation de 2 ns pour une modulation IR-UWB sur une bande passante de 1,5 GHz. Cette thèse décrit le protocole de synchronisation WiDeCS et la conception de deux preuves de concept fonctionnelles sur FPGA et ASIC
Wireless Sensor Networks have attracted mutch interest in the last decade, opening a new range of applications such as large area monitoring. However, a range of possible applications is still not satisfied due to strong blocking points remaining unsolved such as the lack of synchronization between measurements and low attain- able data rates. This doctoral work aims at solving these two issues issue through the design of a Wireless Sensor node implementation. The proposed solution is based on cross-layer design and uses time-domain properties of UltraWide Band (UWB) to provide nanosecond-scale synchronization between nodes and high data- rate transmission. An ASIC implementation has been designed, and demonstrates a 2 ns synchronization error with IR-UWB modulation over a 1.5 GHz bandwidth. In this thesis, a cross-layer scheme named WiDeCS is proposed, and two proof of concept implementations are detailed

Le domaine des transports intelligents repose sur une infrastructure robuste de communication véhiculaire, essentielle à la gestion du trafic, à la surveillance des routes, à l'accessibilité à l'Internet des objets (IoT) et aux informations des conducteurs/passagers. Alors que la norme conventionnelle IEEE802.11p a longtemps dominé ce domaine, l'avènement de la 5G et de ses successeurs marque un changement de paradigme.Cette thèse représente une exploration complète des technologies 5G et au-delà spécifiquement adaptées aux exigences uniques de la communication véhicule-à-tout (V2X). L'objectif principal est une analyse méticuleuse de la technologie Non-Orthogonal Multiple Access (NOMA) et des schémas de modulation multiporteuse (MCM) dans le contexte des applications V2X de nouvelle génération. Au cœur de cette exploration se trouve la recherche de stratégies de conception PHY/MAC (couches physique et de contrôle d'accès au support) transversales visant à élever les performances.Le parcours de recherche commence par une vue d'ensemble introductive, plongeant dans le contexte historique et la pertinence des communications V2X, accompagnée d'un examen des diverses exigences des groupes de cas d'utilisation V2X. Ce travail préliminaire combine des connaissances issues d'organisations normatives et des dernières publications, offrant une vue d'ensemble complète du paysage historique de la communication véhiculaire.Ensuite, la thèse navigue dans le paysage contemporain, mettant l'accent sur l'application des technologies 5G aux différents cas d'utilisation V2X. Elle cartographie la relation entre les groupes de cas d'utilisation V2X et les technologies habilitantes tout en explorant l'architecture hiérarchique 5G V2X. Cette exploration fait le lien entre les exigences actuelles de communication, les normes existantes et les directions de recherche ouvertes ainsi que les défis imminents.Le cœur de la thèse tourne autour de l'exploration des implications des schémas NOMA et MCM dans les applications V2X de prochaine génération. La culmination de cette recherche se manifeste dans un paradigme de conception transversale axé sur l'amélioration des performances et de l'adaptabilité des systèmes de communication cellulaires véhiculaires à tout (C-V2X). En disséquant les mécanismes NOMA au sein des couches physique et de contrôle d'accès au support (PHY/MAC), cette étude démontre des améliorations substantielles des performances de débit par rapport aux systèmes d'accès multiple orthogonal (OMA) conventionnels.Les résultats de cette thèse aspirent à contribuer à des solutions avancées pour les futurs systèmes de transport autonomes et connectés, avec un accent spécifique sur l'amélioration des performances des couches physique et d'accès au support dans des scénarios V2X sophistiqués
The realm of intelligent transportation hinges upon robust vehicular communication infrastructure, vital for traffic management, road monitoring, Internet of Things (IoT) accessibility, and driver/passenger information. While the conventional IEEE802.11p standard has long dominated this domain, the advent of 5G and its successors marks a paradigm shift.This thesis represents a comprehensive exploration of 5G and beyond technologies specifically tailored to the unique demands of Vehicle-to-Everything (V2X) communication. The primary aim is a meticulous analysis of Non-Orthogonal Multiple Access (NOMA) technology and Multi-Carrier Modulation (MCM) schemes within the context of next-generation V2X applications. Central to this exploration is the pursuit of cross-layer PHY/MAC (Physical Layer/Medium Access Control) design strategies aimed at elevating performance benchmarks.The research journey begins with an introductory overview, delving into the historical context and relevance of V2X communications, accompanied by an examination of the diverse requirements across V2X use case groups. This foundational groundwork combines insights from normative organizations and the latest literature, providing a comprehensive overview of the historical landscape of vehicular communication.Subsequently, the thesis navigates the contemporary landscape, emphasizing the application of 5G enabling technologies to various V2X use cases. It maps the relationship between V2X Use Case Groups and Enabling Technologies while exploring the Hierarchical 5G V2X high-level architecture. This exploration bridges current communication requirements and existing standards with open research directions and impending challenges.The core of the thesis revolves around the exploration of NOMA and MCM schemes' implications within next-generation V2X applications. The culmination of this research manifests in a cross-layer design paradigm focusing on the enhancement of performance and adaptability within cellular vehicle-to-everything (C-V2X) communication systems. By dissecting NOMA mechanisms within the Physical/Medium Access Control (PHY/MAC) layers, this study demonstrates substantial throughput performance improvements compared to conventional Orthogonal Multiple Access (OMA) systems.The outcomes of this thesis aspire to contribute advanced solutions for future autonomous and connected transport systems, with a specific emphasis on the enhancement of physical and medium access layer performance within sophisticated V2X scenarios

Wireless Sensor Networks (WSNs) are wireless networks that have recently drawn significant research attention since they offer unique benefits and versatility with respect to sensing, allowing low-power and low-cost rapid deployment for many applications that do not need human supervision. WSNs are self-created and self-organized by the collection of a large number of sensor nodes interconnected by multi-hop wireless paths. The sensor nodes are network embedded systems with Integrated Chips (ICs) to allow signal processing and micro-sensing. Each wireless sensor node is a micro-electro-mechanical device and can only be equipped with a limited power reserve. While energy consumption occurs in sensing, data processing and communications, care should be exercised to make the most of the expendable power source for the node. Though considerable research is being done in the area of energy saving techniques for WSNs, most of the proposed techniques have focused on energy awareness at different network layers in WSNs. Furthermore, most of the proposed techniques are based on protocols for mobile ad hoc networks that do not look into the possibility of a cross-layer design strategy that can exploit the unique features of WSNs. There still exists the need for a universal protocol that can be applied to such networks in general. In this thesis, we focus such a research on optimizing the energy consumption by suggesting a novel cross-layer architecture at the network/data-link layer for sensor networks. We have developed a scheme for better and improved energy efficiency in WSNs by combining the ideas of energy-efficient cluster formation and medium access together. Our cross-layer scheme provides good performance in terms of WSN-lifetime, scalability and minimizing network-wide energy consumption. The scheme is based on a collaborative approach supported by formation of dynamic clusters functioning with a traffic aware MAC (medium access control) scheme. Our MAC scheme incorporates a self-learning, traffic adaptive algorithm for varying traffic conditions inherent to the WSNs. The design methodology and results in this thesis aim at producing a reliable and scalable energy-aware sensing network, in spite of node failures, minimizing energy consumption at the same time.
Master of Science

L’amélioration de l’accès et de la qualité des services de santé publique en Indonésie restent un grand défi. Les obstacles géographiques, la pénurie et la mauvaise répartition des spécialistes/médecins, en particulier dans les zones rurales, sont quelques-uns des défis à relever. En 2016, l’Indonésie a développé un système de télémédecine appelé "soins à domicile" pour surmonter ces défis. Ils ont créé un véhicule de santé mobile appelé "Dottoro ta" qui offre des services de santé 24 heures/jour à la communauté. Ce véhicule est équipé d’Electro- Cardio-Graphy (ECG), d’Ultra-Sono-Graphy (USG) et d’autres équipements médicaux standards. Lorsque les patients font appel à ce service, une équipe composée de médecins, d’infirmières et de chauffeurs se déplace vers l’emplacement du patient et lui prodigue un traitement approprié. Parallèlement, le développement des technologies de l’Internet des objets (IoT) offre une large opportunité d’améliorer ces services. L’IoT est un ensemble de dispositifs ou de capteurs connectés à Internet. Ici, Internet n’a pas besoin d’être une connexion globale; en effet, un réseau local (LAN) est également possible tant qu’il prend en charge les protocoles TCP/IP. La plupart des appareils IoT utilisent des connexions sans fil pour assurer la mobilité et la portabilité. Cependant, les dispositifs sans fil présentent des problèmes fondamentaux comme la consommation d’énergie, le bruit et les interférences des communications sans fil. L’IoT présente de nombreuses variantes de mise en oeuvre, notamment dans les secteurs de la santé. Aujourd’hui, les noeuds de capteurs se sont transformés en petits appareils discrets et puissants, qui peuvent être facilement intégrés dans des appareils portables tels que des montres intelligentes, des bracelets, des gants ou des boutons. Ainsi, l’IoT offre un moyen plus pratique de recueillir les données sur l’état de santé des patients à l’aide de capteurs portables, puis d’envoyer, d’analyser et de stocker les données dans le nuage. L’utilisation de l’IoT dans les secteurs de la santé est le domaine de la télémédecine, permet aux médecins et aux infirmières de récupérer des données en temps réel et d’effectuer immédiatement des diagnostics sur place, sans se préoccuper de l’installation. Cette démarche permet d’accélérer le diagnostic et aura un impact positif sur la santé du patient. En effet, le déploiement du système IoT dans le secteur de la santé présente plusieurs avantages par rapport aux systèmes filaires classiques, tels que la facilité d’utilisation, la réduction du risque d’infection, la réduction du risque d’échec, la réduction de l’inconfort des utilisateurs, l’augmentation de la mobilité, l’amélioration de l’efficacité des soins hospitaliers, et réduire les coûts d’installation. Cependant, fournir une transmission robuste sans fil est un défi dans le domaine de la santé, parce que les données de santé mises à jour en continu sont très importantes pour le traitement des patients. [....] etc
Improving access and quality of public health services in Indonesia is still a big challenge. Geographic obstacles, shortage, and maldistribution of specialist/doctors especially in rural areas are some of the challenges to be answered. In 2016, the city council of Makassar Indonesia has developed a telemedicine system called "home care" to overcome those challenges. They created mobile healthcare vehicle called "Dottoro ta" that gives healthcare services 24 hours/day to the community. This vehicle is equipped with ElectroCardioGraphy (ECG), UltraSonoGraphy (USG) and other standard medical equipment. When patients call this service, a team consisting of doctors, nurses and drivers will move to the patient's location and gives a proper treatment. Meanwhile, the development of Internet of Things (IoT) technologies offers a broad opportunity to improve these services. Changing this equipment with IoT devices will offer a lot of advantages. IoT is the recent technological term, which is a collection of devices or sensors that have connectivity to the internet. Here, the Internet does not have to be a global connection; indeed, a Local Area Network (LAN) is also possible as long as it supports TCP/IP protocols. Most IoT devices use wireless connections to ensure mobility and portability. However, wireless devices have some fundamental issues such as energy consumption, noise and interference of wireless communication. IoT has many variations for implementation including healthcare sectors. Today, sensor nodes have changed into small, unobtrusive and powerful devices, which can be easily accommodated into wearable devices such as smart watches, bracelets, gloves or buttons. Thus, it gives more convenient way to collect the health condition data of patients using wearable sensors and then send, analyzed and stored the data in the cloud. For example, by using heart rate sensors, the conditions of the patients such as heart attacks, anxiety and stress can be continuously monitored. Another potential of using IoT on health sectors is telemedicine field, enabling doctors/nurses to perform retrieval of data in real-time and immediately perform diagnostics on the spot, without preoccupied with the installation of conventional medical devices. This will speed up diagnosis and give a positive impact on the health of the patient. Indeed, deploying IoT system in the health sector has several advantages over conventional wired systems such as ease of use, reducing the risk of infection, reducing the risk of failure, reducing user discomfort, increasing mobility, improving the efficiency of hospital care, and lower installation costs. However, providing the robust transmission in the wireless communication is a challenge in the healthcare domain, because continuous updated health data is very important for the treatment of the patients. In this research activity, we propose a new cross layer protocol to overcome this problem. The proposal takes advantages of beacon power measurements in the node’s PHY layer to determine whether there is interference from the human body or not. This information is used by the MAC layer to decide the transmission of packets. Our results show that there are significant improvements of the PER while maintaining the throughput relatively the same as the conventional protocol. We analytically show the effect of body pathloss on 802.11ah network and its effects in terms of power consumption for the healthcare sensors. We compare the standard pathloss of 802.11ah with body pathloss. We see that body pathloss increase PER and decrease throughput because the body absorbs the electromagnetic signal. We also propose a novel cross-layer algorithm to counter the effect of body pathloss. The idea is to defer the data transmission if there is a high probability of body pathloss by detecting the received power of beacon

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2011.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 87-90).
A cross-layer design approach is proposed that can be used to optimize the cooperative use of multi-packet reception (MPR) and network coding. A simple and intuitive model is constructed for the behavior of an opportunistic network coding scheme called COPE proposed by Katti et. al., MPR, the 802.11 MAC, and their combination. The model is then applied to key small canonical topology components and their larger counterparts. The results obtained from this model match the available experimental results with fidelity. Using this model, fairness allocation by the 802.11 MAC is shown to significantly impede performance and cause non-monotonic saturation behaviors; hence, a new MAC approach is devised that not only substantially improves throughput by providing monotonic saturation but provides fairness to flows of information rather than to nodes. Using this improved MAC, it is shown that cooperation between network coding and MPR achieves super-additive gains of up to 6.3 times that of routing alone with the standard 802.11 MAC. Furthermore, the model is extended to analyze the improved MAC's asymptotic, delay, and throughput behaviors. Finally, it is shown that although network performance is reduced under substantial asymmetry or limited implementation of MPR to a central/bottleneck node, there are some important practical cases, even under these conditions, where MPR, network coding, and their combination provide significant gains.
by Jason M. Cloud.
S.M.

"Respecting a network architecture yields better guarantees of reliability, longevity, and modularity, but much better performance can be potentially achieved through wisely chosen violations to that architecture." In a nutshell, this is the message of a recent paper (see [1] in Chapter 1) outlining pros, cons, consequences and risks of cross-layer design, a currently widely adopted paradigm for wireless networks. The increasing attention and momentum that cross-layer design has recently gained is explained by its potential advantages, namely the network performance improvements that can be achieved, especially under stringent constraints in terms of hardware and computational power. A short definition of cross-layer design identifies this technique as a means of performing information exchange among different layers in the classic ISO/OSI protocol stack model, and of harvesting the potential design opportunities and performance improvements that follow. However, by breaking the modular structure of the ISO/OSI stack, one may encounter two orders of problems: first, unwanted interactions may be introduced; second, the generality of the architecture is lost. While a careful design phase can overcome the first problem, the second one requires stronger efforts. In fact, any cross-layer design is inherently specific to the type of network and scenario it is applied to, and limits the performance improvements to that specific type. Due to this loss of generality, the same protocol hardly offers the same results as applied to different types of networks. In this Thesis, we will show two relevant examples of successful cross-layer design applied to two very different kinds of wireless networks. The first example deals with ad hoc networks with multiple antennas and MIMO communications. Due to the specific scenario, it can be assumed that nodes have high throughput needs and can accept to, e.g., spend more energy in performing the processing required by MIMO signaling in order to achieve greater communication speed. The analysis of this scenario is focused on the design of a novel PHY-aware MAC protocol for MIMO ad hoc networks and on the analysis and optimization of its performance. A completely different point of view is required instead to handle wireless sensor networks (WSNs), the second type of wireless network considered in this Thesis. Peculiar to WSNs are the usually low communication speed, processing capabilities and energy supplies. Among others, these constraints do not allow complicated signal processing or the storage of a large amount of information. In turn this requires to limit the buffer of the nodes (the sensors hence have only a limited packet queue) and also to design protocols whose "state" can be summarized and efficiently held in the limited memory of the sensors. In the Thesis, we will provide an in-depth analysis of a geographic MAC/routing protocol for WSNs, and build upon it to yield a complete solution for channel access and packet forwarding. Part of this study is the design of an algorithm to route packets around connectivity holes, where geographic protocols alone fail. In the appendix, the same cross-layer design concepts are applied to wireless underwater networks, a particular instance of WSNs where communications take place over long delay, low rate acoustic channels, and incur strongly frequency-dependent channel effects. All results (analysis, simulations, comparisons with other solutions) show that cross-layer design is in fact very effective, and offers valuable opportunities to leverage specific features that can lead to performance improvements in each kind of wireless network.

Wireless sensor networks (WSN) are event based systems that rely on the collective effort of densely deployed sensor nodes continuously observing a physical phenomenon. The spatio-temporal correlation between the sensor observations and the cross-layer design advantages are significant and unique to the design of WSN. Due to the high density in the network topology, sensor observations are highly correlated in the space domain. Furthermore, the nature of the energy-radiating physical phenomenon constitutes the temporal correlation between each consecutive observation of a sensor node. This unique characteristic of WSN can be exploited through a cross-layer design of communication functionalities to improve energy efficiency of the network. In this thesis, several key elements are investigated to capture and exploit the correlation in the WSN for the realization of advanced efficient communication protocols. A theoretical framework is developed to capture the spatial and temporal correlations in WSN and to enable the development of efficient communication protocols. Based on this framework, spatial Correlation-based Collaborative Medium Access Control (CC-MAC) protocol is described, which exploits the spatial correlation in the WSN in order to achieve efficient medium access. Furthermore, the cross-layer module (XLM), which melts common protocol layer functionalities into a cross-layer module for resource-constrained sensor nodes, is developed. The cross-layer analysis of error control in WSN is then presented to enable a comprehensive comparison of error control schemes for WSN. Finally, the cross-layer packet size optimization framework is described.

Ce manuscrit est centré sur la conception, l'amélioration et l'évaluation des protocoles des couches RESEAU, MAC et PHY. En particulier, nous nous focalisons sur la conception de nouveaux protocoles distribués pour une utilisation optimale/améliorée des ressources radio disponibles. Par ailleurs, nous caractérisons les performances des réseaux ad hoc à accès aléatoire au canal en utilisant des paramètres de plusieurs couches avec aptitude de transfert d'information (data forwarding). La majeure partie de nos analyses se base sur le concept d'interaction entre les couches OSI (cross-layer). En effet, cette nouvelle et attractive approche est devenue en peu de temps omniprésente dans le domaine de recherche et développement et dans le domaine industriel. Les métriques de performances qui nous intéressent sont la stabilité des files d'attentes de transfert, le débit, le délai et la consommation d'énergie. Principalement, la compréhension de l'interaction entre les couches MAC/PHY et routage du standard IEEE 802.11e DCF/EDCF, d'une part, et l'interaction entre noeuds en terme d'interférences, d'autre part, constituent le coeur central de notre travail

In recent years, the development of a large variety of mobile computing devices has led to wide scale deployment and use of wireless ad hoc and sensor networks. Wireless Sensor Networks consist of battery powered, tiny and cheap "motes", having sensing and wireless communication capabilities. Although wireless motes have limited battery power, communication and computation capabilities, the range of their application is vast. In the first part of the dissertation, we have addressed the specific application of Biomedical Sensor Networks. To solve the problem of data routing in these networks, we have proposed the Adaptive Least Temperature Routing (ALTR) algorithm that reduces the average temperature rise of the nodes in the in-vivo network while routing data efficiently. For delay sensitive biomedical applications, we proposed the Hotspot Preventing Routing (HPR) algorithm which avoids the formation of hotspots (regions having very high temperature) in the network. HPR forwards the packets using the shortest path, bypassing the regions of high temperature and thus significantly reduces the average packet delivery delay, making it suitable for real-time applications of in-vivo networks. We also proposed another routing algorithm suitable for being used in a network of id-less biomedical sensor nodes, namely Routing Algorithm for networks of homogeneous and Id-less biomedical sensor Nodes (RAIN). Finally we developed Biocomm, a cross-layer MAC and Routing protocol co-design for Biomedical Sensor Networks, which optimizes the overall performance of an in-vivo network through cross-layer interactions. We performed extensive simulations to show that the proposed Biocomm protocol performs much better than the other existing MAC and Routing protocols in terms of preventing the formation of hotspots, reducing energy consumption of nodes and preventing network congestion when used in an in-vivo network. In the second part of the dissertation, we have addressed the problems of habitat-monitoring sensor networks, broadcast algorithms for sensor networks and the congestion problem in sensor networks as well as one non-sensor network application, namely, on-chip communication networks. Specifically, we have proposed a variation of HPR algorithm, called Hotspot Preventing Adaptive Routing (HPAR) algorithm, for efficient data routing in Networks On-Chip catering to their specific hotspot prevention issues. A protocol similar to ALTR has been shown to perform well in a sensor network deployed for habitat monitoring. We developed a reliable, low overhead broadcast algorithm for sensor networks namely Topology Adaptive Gossip (TAG) algorithm. To reduce the congestion problem in Wireless Sensor Networks, we proposed a tunable cross-layer Congestion Reducing Medium Access Control (CRMAC) protocol that utilizes buffer status information from the Network layer to give prioritized medium access to congested nodes in the MAC layer and thus preventing congestion and packet drops. CRMAC can also be easily tuned to satisfy different application-specific performance requirements. With the help of extensive simulation results we have shown how CRMAC can be adapted to perform well in different applications of Sensor Network like Emergency Situation that requires a high network throughput and low packet delivery latency or Long-term Monitoring application requiring energy conservation.
Ph.D.
School of Electrical Engineering and Computer Science
Engineering and Computer Science
Computer Science PhD

碩士
國立臺南大學
電機工程學系碩博士班
105
In the recent years, with high popularity of smart mobile devices, how to extend their battery life is always an important issue. With the rise of various Internet services and applications, the wireless network interface becomes the most power consumed part of mobile device. As a result, how to reduce the energy consumption of wireless access modules by designing an high efficient sleep scheduling and energy-saving resource allocation scheme is one of the most important research topics. In this paper, we design a cross-layer energy-saving sleep scheduling mechanism with carrier aggregation in Long-Term Evolution-Advanced (LTE-A)/LTE-A Pro uplink heterogeneous networks. The design considers the Medium Access Control (MAC) layer multi-user sleep scheduling (via the settings of DRX/DTX parameters) and the Physical layer power, carrier, and radio resource allocations at the same time. To the best of our knowledge, this is the first work to consider the cross-layer sleep scheduling and energy-saving resource allocation problem in LTE-A/LTE-A Pro carrier aggregation heterogeneous networks. In a heterogeneous network environment, to reduce the interference between the eNB and Smallcells, we assign different carrier to the eNB and the Smallcell as their primary carrier. In addition, the eNB configures and schedules the Almost Blank Subframes (ABS) when needed, thus the Smallcell can carrier aggregate more bands to provide more UEs to access the Internet in an energy-saving way. To more accurately model the energy consumption of the wireless module of the UE, we take the usage of the baseband and radio frequency modules and the allocation of transmit power into account. Last but not the least, the proposed method is compatible with the 3GPP LTE-A/ LTE-A Pro standard. The simulation results show better energy saving compared to other schemes.

碩士
國立臺南大學
電機工程學系碩博士班
104
In the recent years, with high popularity of smart mobile devices, how to extend their battery life is always an important issue. According to the experiment, for a 3G handheld device, the wireless interface consumes the largest proportion of the total power (up to 40%). In particular, the 4G and 5G wireless communications will provide higher data rate. As a result, the wireless interface in these devices will consume much more power than that in a 3G device. Specifically, emerging cloud computing and IoT applications also increase the operation time of wireless modems in a mobile device. In this case, how to maximize wireless interfaces’ energy efficiency and design effective energy-saving sleep scheduling mechanism become a critical issue. In this thesis, we design cross-layer energy-saving sleep scheduling mechanisms in LTE-A/B4G uplink by jointly considering system level energy consumption of wireless interfaces and QoS (Quality of Service) requirements of traffic flows. The design considers the Medium Access Control (MAC) Layer multi-user sleep scheduling (via the settings of DRX/DTX parameters) and the Physical Layer power and radio resource allocations at the same time. Furthermore, to maximize the energy efficiency, we also exploit the tolerable packet drop rate and delay bound of traffic flows. When the channel condition is bad for a mobile device, the packet data delivery can be postponed and wait for a better channel quality if its packet drop rate can be guaranteed. Last but not the least, the proposed method is compatible with the 3GPP LTE-A standard.

碩士
國立臺南大學
電機工程學系碩博士班
106
In the recent years, with the popularity of smart mobile devices, how to extend the battery life of the device has always been one of the most concerned research topics. According to experiments, the wireless communication interface of the 3G/4G mobile device accounts for the largest power consumption. Specifically, the longer time of various network services and applications occupy a mobile device, the more power consumption of the wireless communication interface induces. How to reduce the energy consumption of wireless access modules by designing a highly efficient sleep scheduling and energy-saving transmission method is one of the most important research issues. To alleviate this problem, we design a Dynamic Sleep Scheduling and Energy-Saving Resource Allocation (DS2ESRA) method in the LTE-A/B4G (Long Term Evolution-Advanced/Beyond 4G) uplink network, which jointly considers both the dynamic multi-user sleep scheduling of the Media Access Control (MAC) layer and the radio resource allocation of the physical (PHY) layer. The sleep scheduling are done via the settings of LTE-A DRX/DTX parameters, i.e., sleep period, on duration, offset, and inactivity timer, while the physical radio resource allocations involve the assignment of transmit power, radio resource, Modulation and Coding Scheme (MCS), and uplink data size in each subframe for each active UE. Considering the real situation of traffics, connection requests are joining and leaving the network over time. We have to design a dynamic sleep scheduling scheme which can schedule the sleep of new UEs without modifying the sleep parameters of other existing users. Thus, the control overhead, including computational time and message overhead, can be dramatically reduced. Furthermore, to maximize the energy efficiency of data streaming, we also exploit the tolerable packet drop rate and delay bound. When the channel condition is bad for a mobile device, the packet data delivery can be postponed and wait for a better channel quality if its packet drop rate can be guaranteed. Simulation results show that compared with other methods, DS2ESRA can achieve the best energy saving and minimal control overhead while guarantee the QoS of mobile devices.

碩士
國立臺南大學
電機工程學系碩博士班
103
In this article, a cross-layer design of sleep scheduling in 3GPP LTE/LTE-A wireless networks is discussed. The design jointly considers the Medium Access Control (MAC) layer multi-user sleep scheduling (via the settings of DRX/DTX parameters) and the physical layer power and radio resource allocations. The new approach enables UEs to gain longer battery life time and better utility of radio resource while guarantee the delay, packet drop rate, and maximum transmit power constraints. The design is validated through comparison with simulation results.

碩士
國立政治大學
資訊科學學系
96
Over the past decade, wireless network access and video streaming services have become more popular than ever. People are eager to have better quality of video streaming services over wireless network. However, IEEE 802.11 DCF and IEEE 802.11e EDCA are not specifically designed for video streaming. This leads to the problem of transmitting overdue video packets and thus degrades both the network performance and video quality. In this paper, we propose a hybrid design framework to improve the quality of video streaming. This framework consists of a MAC-centric cross-layer architecture to allow MAC-layer to retrieve video streaming packet information (slice type and transmission deadline), a retransmission mechanism of hybrid retransmission deadline and retry limit to save unnecessary packet waiting time, and a single-video multi-level queue to prioritize I/P/B slice delivery. Simulations show that the proposed methodology outperforms IEEE 802.11e, IEEE 802.11e Timebase and IEEE 802.11e MultiQ in packet loss rate, invalid packet ratio, lost and invalid packet ratio, delay time, jitter, and PSNR.

碩士
國立交通大學
電機學院IC設計產業專班
95
A procedure is for SoC verification process in wireless communication system. The most concern in wireless communication system is interactive between base stations and mobile stations. In other words, this is not enough for SoC verification to verify a single base station or mobile station, especially under the pressure of time-to-market and design complexity. Therefore, how to verify the interactive of wireless communication system fast and completely in the early process of design flow is the key point. This paper introduces an ESL tool, including HW/SW co-design, system architecture exploit, and co-simulation/verification, to establish a cross-layer multi-node environment for verifying the interactive and analyzing the system performance. The fundamental design concept is a system level design abstraction, so it can conveniently provide precise analysis results of a system performance in the early process of design flow.

IEEE 802.11n Wireless Local Area Networks (WLANs) employ Multiple-Input-Multiple-Output (MIMO), which significantly boosts the raw data rate at the Physical layer (PHY). But the potential of enhancing Medium Access Control (MAC) layer efficiencies by MIMO is still in its early stage and is the aim of the research in this thesis. Many existing works in this field mainly employ distributed MIMO spatial multiplexing/Multi-User Detection (MUD) technique and stream sharing to enable multiple simultaneous transmissions. Most works require synchronization among multiple transmissions, split the channel, and aim for single-hop networks. In this thesis, a novel Hybrid Carrier Sense (HCS) framework is proposed, mainly at the MAC layer to exploit the power of MIMO. HCS senses the channel availability jointly by the virtual carrier sense and physical carrier sense. HCS does not require synchronization among nodes; each node independently and locally determines when to start its transmission. HCS not only shares the channel, but also exploits the bi-directional handshakes of the wireless transmissions and increases the number of simultaneous stream transmissions. For a network with M antennas in each node, HCS can accommodate 2x(M-1) streams instead of M streams achieved by all other existing works. Moreover, HCS is aimed for multi-hop wireless ad hoc networks, in which the hidden terminal, exposed terminal, and deafness problems greatly degrade network performance. The HCS framework incorporates solutions to these problems. HCS is implemented in an NS2 network simulator and the performance evaluation shows that HCS significantly outperforms MIMO-enabled IEEE 802.11 (in which MIMO is only used for enhancing the raw data rate in the physical layer), resulting in higher aggregate throughput, packet delivery ratio and fairness in multi-hop wireless ad hoc networks. The HCS framework will be in wide use in the future generation of wireless networks and opens up more research possibilities. Some ideas in the HCS framework can be applied not only for MIMO, but also for many other techniques surveyed in this thesis; or we may combine them with HCS to further boost the network performance.
Thesis (Ph.D, Electrical & Computer Engineering) -- Queen's University, 2013-10-15 21:46:15.983

This thesis presents a cross-layer design and optimization for emerging wideband wireless networks supporting multimedia applications, considering the interactions of the wireless channel characteristics, the physical and link layer protocols, and the user-perceived Quality-of-Service (QoS). As wireless channels are error-prone and broadcast in nature, both the error control mechanisms and the Media Access Control (MAC) protocols are critical for resource utilization and QoS provisioning. How to analyze, design and optimize the high-rate wireless networks by considering the characteristics of the propagation channels and wideband communication technologies is an open, challenging issue. In this thesis, we consider two important wideband wireless systems, the Ultra-Wideband (UWB) and the Orthogonal Frequency-Division Multiplexing (OFDM) systems. First, we propose the packet-level channel models based on Finite State Markov Chains (FSMCs) for the two systems, which present the statistical properties of the propagation channels and the transmission systems. Second, by incorporating the proposed packet-level channel models, we develop analytical frameworks for quantifying the performance of the high-rate wireless networks, combining the channel fading, physical- and link-layer error-control mechanisms and MAC protocols. Third, to mitigate the impact of channel fading and impairments, a cross-layer joint error-control mechanism is proposed. In addition, we also investigate the impact of channel fading on the video streaming applications, and propose a simple admission control algorithm to ensure QoS. As considering the physical-layer characteristics is critical for ensuring QoS and efficiency of resource utilization, the packet-level channel models, cross-layer analytical frameworks, networking protocols and simulation methodologies proposed in this dissertation are essential for future proliferation of high-rate wireless networks.

As more and more wireless applications/services emerge in the market, the already heavily crowded radio spectrum becomes much scarcer. Meanwhile, however,as it is reported in the recent literature, there is a large amount of radio spectrum that is under-utilized. This motivates the concept of cognitive radio wireless networks that allow the unlicensed secondary-users (SUs) to dynamically use the vacant radio spectrum which is not being used by the licensed primary-users (PUs). In this dissertation, we investigate protocol design for both the synchronous and asynchronous cognitive radio networks with emphasis on the medium access control (MAC) layer. We propose various spectrum sharing schemes, opportunistic packet scheduling schemes, and spectrum sensing schemes in the MAC and physical (PHY) layers for different types of cognitive radio networks, allowing the SUs to opportunistically utilize the licensed spectrum while confining the level of interference to the range the PUs can tolerate. First, we propose the cross-layer based multi-channel MAC protocol, which integrates the cooperative spectrum sensing at PHY layer and the interweave-based spectrum access at MAC layer, for the synchronous cognitive radio networks. Second, we propose the channel-hopping based single-transceiver MAC protocol for the hardware-constrained synchronous cognitive radio networks, under which the SUs can identify and exploit the vacant channels by dynamically switching across the licensed channels with their distinct channel-hopping sequences. Third, we propose the opportunistic multi-channel MAC protocol with the two-threshold sequential spectrum sensing algorithm for asynchronous cognitive radio networks. Fourth, by combining the interweave and underlay spectrum sharing modes, we propose the adaptive spectrum sharing scheme for code division multiple access (CDMA) based cognitive MAC in the uplink communications over the asynchronous cognitive radio networks, where the PUs may have different types of channel usage patterns. Finally, we develop a packet scheduling scheme for the PU MAC protocol in the context of time division multiple access (TDMA)-based cognitive radio wireless networks, which is designed to operate friendly towards the SUs in terms of the vacant-channel probability. We also develop various analytical models, including the Markov chain models, M=GY =1 queuing models, cross-layer optimization models, etc., to rigorously analyze the performance of our proposed MAC protocols in terms of aggregate throughput, access delay, and packet drop rate for both the saturation network case and non-saturation network case. In addition, we conducted extensive simulations to validate our analytical models and evaluate our proposed MAC protocols/schemes. Both the numerical and simulation results show that our proposed MAC protocols/schemes can significantly improve the spectrum utilization efficiency of wireless networks.