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Tesi sul tema "Wireless networks"
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1
Gaddam, Nishanth. "Network coding in wireless networks". [Ames, Iowa : Iowa State University], 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1468982.
Testo completo
2
Jiang, Shu. "Efficient network camouflaging in wireless networks". Texas A&M University, 2005. http://hdl.handle.net/1969.1/3067.
Testo completoAbstract (sommario):
Camouflaging is about making something invisible or less visible. Network
camouflaging is about hiding certain traffic information (e.g. traffic pattern, traffic
flow identity, etc.) from internal and external eavesdroppers such that important
information cannot be deduced from it for malicious use. It is one of the most challenging
security requirements to meet in computer networks. Existing camouflaging
techniques such as traffic padding, MIX-net, etc., incur significant performance degradation
when protected networks are wireless networks, such as sensor networks and
mobile ad hoc networks. The reason is that wireless networks are typically subject to
resource constraints (e.g. bandwidth, power supply) and possess some unique characteristics
(e.g. broadcast, node mobility) that traditional wired networks do not
possess. This necessitates developing new techniques that take account of properties
of wireless networks and are able to achieve a good balance between performance and
security.
In this three-part dissertation we investigate techniques for providing network
camouflaging services in wireless networks. In the first part, we address a specific
problem in a hierarchical multi-task sensor network, i.e. hiding the links between
observable traffic patterns and user interests. To solve the problem, a temporally constant traffic pattern, called cover traffic pattern, is needed. We describe two traf-
fic padding schemes that implement the cover traffic pattern and provide algorithms
for achieving the optimal energy efficiencies with each scheme. In the second part,
we explore the design of a MIX-net based anonymity system in mobile ad hoc networks.
The objective is to hide the source-destination relationship with respect to
each connection. We survey existing MIX route determination algorithms that do
not account for dynamic network topology changes, which may result in high packet
loss rate and large packet latency. We then introduce adaptive algorithms to overcome
this problem. In the third part, we explore the notion of providing anonymity
support at MAC layer in wireless networks, which employs the broadcast property
of wireless transmission. We design an IEEE 802.11-compliant MAC protocol that
provides receiver anonymity for unicast frames and offers better reliability than pure
broadcast protocol.
3
Kim, MinJi Ph D. Massachusetts Institute of Technology. "Network coding for robust wireless networks". Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/71276.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student submitted PDF version of thesis.
Includes bibliographical references (p. 157-167).
Wireless networks and communications promise to allow improved access to services and information, ubiquitous connectivity, and mobility. However, current wireless networks are not well-equipped to meet the high bandwidth and strict delay requirements of future applications. Wireless networks suffer from frequent losses and low throughput. We aim to provide designs for robust wireless networks. This dissertation presents protocols and algorithms that significantly improve wireless network performance and effectively overcome interference, erasures, and attacks. The key idea behind this dissertation is in understanding that wireless networks are fundamentally different from wired networks, and recognizing that directly applying techniques from wired networks to wireless networks limits performance. The key ingredient underlying our algorithms and protocols is network coding. By recognizing the algebraic nature of information, network coding breaks the convention of routing networks, and allows mixing of information in the intermediate nodes and routers. This mixing has been shown to have numerous performance benefits, e.g. increase in throughput and robustness against losses and failures. We present three protocols and algorithms, each using network coding to harness a different characteristic of the wireless medium. We address the problem of interference, erasures, and attacks in wireless networks with the following network coded designs. -- Algebraic NC exploits strategic interference to provide a distributed, randomized code construction for multi-user wireless networks. Network coding framework simplifies the multi-user wireless network model, and allows us to describe the multi-user wireless networks in an algebraic framework. This algebraic framework provides a randomized, distributed code construction, which we show achieves capacity for multicast connections as well as a certain set of non-multicast connections. -- TCP/NC efficiently and reliably delivers data over unreliable lossy wireless networks. TCP, which was designed for reliable transmission over wired networks, often experiences severe performance degradation in wireless networks. TCP/NC combines network coding's erasure correction capabilities with TCP's congestion control mechanism and reliability. We show that TCP/NC achieves significantly higher throughput than TCP in lossy networks; therefore, TCP/NC is well suited for reliable communication in lossy wireless networks. -- Algebraic Watchdog takes advantage of the broadcast nature of wireless networks to provide a secure global self-checking network. Algebraic Watchdog allows nodes to detect malicious behaviors probabilistically, and police their neighbors locally using overheard messages. Unlike traditional detection protocols which are receiver-based, this protocol gives the senders an active role in checking the nodes downstream. We provide a trellis-based inference algorithm and protocol for detection, and analyze its performance. The main contribution of this dissertation is in providing algorithms and designs for robust wireless networks using network coding. We present how network coding can be applied to overcome the challenges of operating in wireless networks. We present both analytical and simulation results to support that network coded designs, if designed with care, can bring forth significant gains, not only in terms of throughput but also in terms of reliability, security, and robustness.
by MinJi Kim.
Ph.D.
4
Attar, Hani Hasan. "Cooperative Network Coding for wireless networks". Thesis, University of Strathclyde, 2011. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=16782.
Testo completo
5
Nerini, Matteo. "Network Slicing for IEEE 802.11 Wireless Networks". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/21149/.
Testo completoAbstract (sommario):
Future networks will pave the way for a myriad of applications with different requirements. In such a context, the today’s one-size-fits-all approach will not be able to efficiently address the different demands that verticals impose in terms of QoS and involved data volumes. To this end, network slicing is a new network paradigm which may provide the needed flexibility. It allows to offer multiple logical networks over a common infrastructure, tailored to the services which run on the network.
In today’s Wi-Fi networks, all the users are connected to the same wireless channel, which allows service differentiation only at the traffic level. Thus, in this study, we propose a standard-compliant network slicing approach for the radio access segment of Wi-Fi, often neglected by the literature on network slicing.
We present two algorithms to realize network slicing at the access level. The first assigns resources according to the requirements of the slices in a static way. On the other hand, the second, more advanced, dynamically configures the slices according to the network conditions and relevant KPIs. These techniques can be applied to the IEEE 802.11 standard and, in general, to all the protocols that use Carrier Sensing Multiple Access (CSMA) as channel access technique.
The proposed algorithms were validated through extensive simulations, conducted with ns-3 network simulator and accompanied by theoretical calculations. Particular attention, often neglected in similar simulation-based works, has been paid to the electromagnetic properties of the spectrum, which play a fundamental role in radio communications.
From the conducted simulations, we found that our slicing approaches largely outperform the today’s Wi-Fi access technique. They allow to reach higher goodput (i.e. a lower error probability) and lower latency, when needed. At the same time, tailored slicing saves energy to low-power devices and increases the spectrum efficiency.
6
Tan, Hailun Computer Science & Engineering Faculty of Engineering UNSW. "Secure network programming in wireless sensor networks". Awarded By:University of New South Wales. Computer Science & Engineering, 2010. http://handle.unsw.edu.au/1959.4/44835.
Testo completoAbstract (sommario):
Network programming is one of the most important applications in Wireless Sensor Networks as It provides an efficient way to update program Images running on sensor nodes without physical access to them. Securing these updates, however, remains a challenging and important issue, given the open deployment environment of sensor nodes. Though several security schemes have been proposed to impose the authenticity and Integrity protection on network programming applications, they are either energy Inefficient as they tend to use digital signature or lacks the data confidentiality. In addition, due to the absence of secure memory management in the current sensor hardware, the attacker could inject malicious code into the program flash by exploiting buffer overflow In the memory despite the secure code dissemination. The contribution of this thesis Is to provide two software-based security protocols and one hardware-based remote attestation protocol for network programming application. Our first protocol deploys multiple one-way key chains for a multi-hop sensor network. The scheme Is shown to be lower In computational, power consumption and communication costs yet still able to secure multi??hop propagation of program images. Our second protocol utilizes an Iterative hash structure to the data packets in network programming application, ensuring the data confidentiality and authenticity. In addition, we Integrated confidentiality and DoS-attack-resistance in a multi??hop code dissemination protocol. Our final solution is a hardware-based remote attestation protocol for verification of running codes on sensor nodes. An additional piece of tamper-proof hardware, Trusted Platform Module (TPM), is imposed into the sensor nodes. It secures the sensitive information (e.g., the session key) from attackers and monitors any platform environment changes with the Internal registers. With these features of TPM, the code Injection attack could be detected and removed when the contaminated nodes are challenged in our remote attestation protocol. We implement the first two software-based protocols with Deluge as the reference network programming protocol in TinyOS, evaluate them with the extensive simulation using TOSSIM and validate the simulation results with experiments using Tmote. We implement the remote attestation protocol on Fleck, a sensor platform developed by CSIRO that Integrates an Atmel TPM chip.
7
Hildebrand, Matthias. "Optimized network access in heterogeneous wireless networks". Kassel : Kassel Univ. Press, 2005. http://deposit.d-nb.de/cgi-bin/dokserv?idn=977677540.
Testo completo
8
Shi, Xiaomeng Ph D. Massachusetts Institute of Technology. "Energy aware network coding in wireless networks". Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/78533.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 97-104).
Energy is one of the most important considerations in designing reliable low-power wireless communication networks. We focus on the problem of energy aware network coding. In particular, we investigate practical energy efficient network code design for wireless body area networks (WBAN). We first consider converge-cast in a star-shaped topology, in which a central base station (BS), or hub, manages and communicates directly with a set of nodes. We then consider a wireless-relay channel, in which a relay node assists in the transmission of data from a source to a destination. This wireless relay channel can be seen as a simplified extended star network, where nodes have relay capabilities. The objective is to investigate the use of network coding in these scenarios, with the goal of achieving reliability under low-energy and lower-power constraints. More specifically, in a star network, we propose a simple network layer protocol, study the mean energy to complete uploads of given packets from the nodes to the BS using a Markov chain model, and show through numerical examples that when reception energy is taken into account, the incorporation of network coding offers reductions in energy use. The amount of achievable gains depends on the number of nodes in the network, the degree of asymmetry in channel conditions experienced by different nodes, and the relative difference between transmitting and receiving power at the nodes. We also demonstrate the compatibility of the proposed scheme with the IEEE 802.15.6 WBAN standard by describing ways of incorporating network coding into systems compliant to the standard. For a wireless relay channel, we explore the strategic use of network coding according to both throughput and energy metrics. In the relay channel, a single source communicates to a single sink through the aid of a half-duplex relay. The fluid flow model is used to describe the case where both the source and the relay are coding, and Markov chain models are proposed to describe packet evolution if only the source or only the relay is coding. Although we do not attempt to explicitly categorize the optimal network coding strategies in the relay channel under different system parameters, we provide a framework for deciding whether and where to code, taking into account of throughput maximization and energy depletion constraints.
by Xiaomeng Shi.
Ph.D.
9
Rastogi, Preeti. "Assessing Wireless Network Dependability Using Neural Networks". Ohio University / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1129134364.
Testo completo
10
Taiwo, Olugbenga Adekunle. "Network access selection in heterogeneous wireless networks". Master's thesis, University of Cape Town, 2013. http://hdl.handle.net/11427/16832.
Testo completoAbstract (sommario):
In heterogeneous wireless networks (HWNs), both single-homed and multi-homed terminals are supported to provide connectivity to users. A multiservice single-homed multi-mode terminal can support multiple types of services, such as voice call, file download and video streaming simultaneously on any one of the available radio access technologies (RATs) such as Wireless Local Area Network (WLAN), and Long Term Evolution (LTE). Consequently, a single-homed multi-mode terminal having multiple on-going calls may need to perform a vertical handover from one RAT to another. One of the major issues in HWNs is how to select the most suitable RAT for multiple handoff calls, and the selection of a suitable RAT for multiple-calls from a single-homed multi-mode terminal in HWNs is a group decision problem. This is because a single-homed multi-mode terminal can connect to only one RAT at a time, and therefore multiple handoff calls from the terminal have to be handed over to the same RAT. In making group decision for multiple-calls, the quality of service (QoS) requirements for individual calls needs to be considered. Thus, the RAT that most satisfies the QoS requirements of individual calls is selected as the most suitable RAT for the multiple-calls. Whereas most research efforts in HWNs have concentrated on developing vertical handoff decision schemes for a single call from a multi-mode terminal, not much has been reported in the literature on RAT-selection for multiple-calls from a single-homed multi-mode terminal in next generation wireless networks (NGWNs). In addition, not much has been done to investigate the sensitivity of RAT-selection criteria for multiple-calls in NGWNs. Therefore, this dissertation addresses these issues by focusing on following two main aspects: (1) comparative analysis of four candidate multi-criteria group decision-making (MCGDM) schemes that could be adapted for making RAT-selection decisions for multiple-calls, and (2) development of a new RAT-selection scheme named the consensus RAT-selection model. In comparative analysis of the candidate RAT-selection schemes, four MCGDM schemes namely: distance to the ideal alternative-group decision making (DIA-GDM), multiplicative exponent weighting-group decision making (MEW-GDM), simply additive weighting-group decision making (SAW-GDM), technique for order preference by similarity to Ideal solution-group decision making (TOPSIS-GDM) are considered. The performance of the multiple-calls RAT-selection schemes is evaluated using the MATLAB simulation tool. The results show that DIA-GDM and TOPSIS-GDM schemes are more suitable for multiple handoff calls than SAW-GDM and MEW-GDM schemes. This is because they are consistent and less-sensitive in making RAT-selection decision than the other two schemes, with regards to RAT-selection criteria (service price, data rate, security, battery power consumption and network delay) in HWNs. In addition, the newly developed RAT-selection scheme incorporates RAT-consensus level for improving RAT-selection decisions for multiple-calls. Numerical results conducted in MATLAB validate the effectiveness and performance of the newly proposed RAT-selection scheme for multiple-calls in HWNs.
11
Lim, Tiong Hoo. "Dependable network protocols in wireless sensor networks". Thesis, University of York, 2013. http://etheses.whiterose.ac.uk/4903/.
Testo completoAbstract (sommario):
This thesis is concerned with the dependability of Wireless Sensor Networks (WSNs). We propose an approach, inspired by the immune system, that allows individual nodes to detect, diagnose and recover from different failures by switching between different protocols using a multi-modal switching mechanism. A causal link between different failures in WSN is identified. Existing fault tolerance in WSNs approaches are examined. From the survey, it is identified that various attempts have been made to improve the fault tolerance of the communication protocol especially in the routing protocols. Although tests have been performed to evaluate the communication protocols prior to deployment, failures in WSNs are still being reported when deployed in real environments. A Systematic Protocol Evaluation Technique (SPET) is proposed and applied to evaluate the dependability of the proposed multi-modal protocol and reduce the uncertainties in the experiment and to demonstrate the confidence in the measurements taken from experiments.
12
Sheng, Zhengguo. "Cooperative wireless networks". Thesis, Imperial College London, 2011. http://hdl.handle.net/10044/1/6941.
Testo completoAbstract (sommario):
In the last few years, there have been a lot of interests in wireless ad-hoc networks as they have remarkable commercial and military applications. Such wireless networks have the benefit of avoiding a wired infrastructure. However, signal fading is a severe problem for wireless communications particularly for the multi-hop transmissions in the ad-hoc networks. Cooperative communication has been proposed as an effective way to improve the quality of wireless links. The key idea is to have multiple wireless devices at different locations cooperatively share their antenna resources and aid each other’s transmission. In this thesis, we develop effective algorithms for cooperative wireless ad-hoc networks, and the performance of cooperative communication is measured based on various criteria, such as cooperative region, power ratio and end-to-end performance. For example, the proposed interference subtraction and supplementary cooperation algorithms can significantly improve network throughput of a multi-hop routing. Comprehensive simulations are carried out for all the proposed algorithms and performance analysis, providing quantitative evidence and comparison over other schemes. In our view, the new cooperative communication algorithms proposed in this research enable wireless ad-hoc networks to improve radio unreliability and meet future application requirements of high-speed and high-quality services with high energy efficiency. The acquired new insights on the network performance of the proposed algorithms can also provide precise guidelines for efficient designs of practical and reliable communications systems. Hence these results will potentially have a broad impact across a range of related areas, including wireless communications, network protocols, radio transceiver design and information theory.
13
Gambetti, Claudio <1978>. "Wireless heterogeneous networks". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2007. http://amsdottorato.unibo.it/394/1/Tesi_Gambetti_finale.pdf.
Testo completo
14
Gambetti, Claudio <1978>. "Wireless heterogeneous networks". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2007. http://amsdottorato.unibo.it/394/.
Testo completo
15
Buratti, Chiara <1976>. "Wireless ambient networks". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amsdottorato.unibo.it/2118/1/chiara_buratti_tesi.pdf.
Testo completo
16
Buratti, Chiara <1976>. "Wireless ambient networks". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amsdottorato.unibo.it/2118/.
Testo completo
17
Sharma, Sushant. "Cooperation in Wireless Networks". Diss., Virginia Tech, 2010. http://hdl.handle.net/10919/30219.
Testo completoAbstract (sommario):
Spatial diversity, in the form of employing multiple antennas (i.e., MIMO), has proved to be very effective in increasing network capacity and reliability. However, equipping a wireless node with multiple antennas may not be practical, as the footprint of multiple antennas may not fit on a wireless node (particularly on handheld wireless devices). In order to achieve spatial diversity without requiring multiple antennas on the same node, the so-called cooperative communications (CC) has been introduced. Under CC, each node is equipped with only a single antenna and spatial diversity is achieved by exploiting the antennas on other nodes in the network through cooperative relaying.
The goal of this dissertation is to maximize throughput at network level through CC at the physical layer. A number of problems are explored in this investigation. The main contributions of this dissertation can be summarized as follows.
1. Optimal Relay Assignment. We first consider a simple CC model where each source-destination pair may employ only a single relay. For this three-node model, the choice of a relay node (among a set of available relay nodes) for a given session is critical in the overall network performance. We study the relay node assignment problem in a cooperative ad hoc network environment, where multiple source-destination pairs compete for the same pool of relay nodes in the network. Our objective is to assign the available relay nodes to different source-destination pairs so as to maximize the minimum data rate among all pairs. We present an optimal polynomial time algorithm, called ORA, that solves this problem. A novel idea in this algorithm is a "linear marking" mechanism, which maintains linear complexity at each iteration. We offer a formal proof of optimality for ORA and use numerical results to demonstrate its capability.
2. Incorporating Network Coding. It has been shown that network coding (NC) can reduce the time-slot overhead when multiple session share the same relay node in CC. Such an approach is called network-coded CC (or NC-CC). Most of the existing works have mainly focused on the benefits of this approach. The potential adverse effect under NC-CC remains unknown. We explore this important problem by introducing the concept of network coding noise (NC noise). We show that due to NC noise, NC may not be always beneficial to CC. We substantiate this important finding in two important scenarios: analog network coding (ANC) in amplify-and-forward (AF) CC, and digital network coding (DNC) in decode-and-forward (DF) CC. We analyze the origin of NC noise via a careful study of signal aggregation at a relay node and signal extraction at a destination node. We derive a closed-form expression for NC noise at each destination node and show that the existence of NC noise could diminish the advantage of NC in CC. Our results shed new light on how to use NC in CC effectively.
3. Session Grouping and Relay Node Selection. When there are multiple sessions in the network, it may be necessary to combine sessions into different groups, and then have each group select the most beneficial relay node for NC-CC. We study this joint grouping and relay node selection problem for NC-CC. By studying matching problems in hypergraphs, we show that this problem is NP-hard. We then propose a distributed and online algorithm to solve this problem. The key idea in our algorithm is to have each neighboring relay node of a newly joined session determine and offer the best group for this session from the groups that it is currently serving; and then to have the source node of this newly joined session select the best group among all received offers. We show that our distributed algorithm has polynomial complexity. Using extensive numerical results, we show that our distributed algorithm is near-optimal and adapts well to online network dynamics.
4. Grouping and Matching for Multi-Relay Cooperation. Existing models of NC-CC consider only single relay node for each session group. We investigate how NC-CC behaves when multiple relay nodes are employed. For a given session, we develop closed form formulas for the mutual information and achievable rate under multi-relay NC-CC. In multi-relay NC-CC, the achievable rate of a session depends on the other sessions in its group as well as the set of relay nodes used for NC-CC. Therefore, we study NC-CC via joint optimization of grouping and matching of session and relay groups in an ad hoc network. Although we show that the joint problem is NP-hard, we develop an efficient polynomial time algorithm for grouping and matching (called G²M). G²M first builds beneficial relay groups for individual sessions. This is followed by multiple iterations during which sessions are combined with other sessions to form larger and better session groups (while corresponding relay groups are merged and updated accordingly). Using extensive numerical results, we show the efficiency and near optimality of our G²M algorithm.Ph. D.
18
Shen, Fangyang Sun Min-Te. "Improving system performance for wireless networks". Auburn, Ala, 2008. http://hdl.handle.net/10415/1544.
Testo completo
19
Amusa, Ebenezer Olukayode. "An enhanced cross-layer routing protocol for wireless mesh networks based on received signal strength". Thesis, University of Bedfordshire, 2010. http://hdl.handle.net/10547/143534.
Testo completoAbstract (sommario):
The research work presents an enhanced cross-layer routing solution for Wireless Mesh Networks (WMN) based on Received Signal Strength. WMN is an emerging technology with varied applications due to inherent advantages ranging from self-organisation to auto-con guration. Routing in WMN is fundamen- tally achieved by hop counts which have been proven to be de cient in terms of network performance. The realistic need to enhance the link quality metric to improve network performance has been a growing concern in recent times. The cross-Layer routing approach is one of the identi ed methods of improving routing process in Wireless technology. This work presents an RSSI-aware routing metric implemented on Optimized Link-State Routing (OLSR) for WMN. The embedded Received Signal Strength Information (RSSI) from the mesh nodes on the network is extracted, processed, transformed and incorporated into the routing process. This is to estimate efficiently the link quality for network path selections to improved network performance. The measured RSSI data is filtered by an Exponentially Weighted Moving Average (EWMA) filter. This novel routing metric method is called RSSI-aware ETT (rETT). The performance of rETT is then optimised and the results compared with the fundamental hop count metric and the link quality metric by Expected Transmission Counts (ETX). The results reveal some characteristics of RSSI samples and link conditions through the analysis of the statistical data. The divergence or variability of the samples is a function of interference and multi-path e effect on the link. The implementation results show that the routing metric with rETT is more intelligent at choosing better network paths for the packets than hop count and ETX estimations. rETT improvement on network throughput is more than double (120%) compared to hop counts and 21% improvement compared to ETX. Also, an improvement of 33% was achieved in network delay compared to hop counts and 28% better than ETX. This work brings another perspective into link-quality metric solutions for WMN by using RSSI to drive the metric of the wireless routing protocol. It was carried out on test-beds and the results obtained are more realistic and practical. The proposed metric has shown improvement in performance over the classical hop counts metric and ETX link quality metric.
20
Sevgi, Cuneyt. "Network Dimensioning In Randomly Deployed Wireless Sensor Networks". Phd thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/2/12611213/index.pdf.
Testo completoAbstract (sommario):
In this study, we considered a heterogeneous, clustered WSN, which consists of two
types of nodes (clusterheads and sensor nodes) deployed randomly over a sensing field.
We investigated two cases based on how clusterheads can reach the sink: direct and
multi-hop communication cases. Network dimensioning problems in randomly deployed
WSNs are among the most challenging ones as the attributes of these networks are
mostly non-deterministic. We focused on a number of network dimensioning problems
based on the connected coverage concept, which is the degree of coverage achieved by
only the connected devices. To evaluate connected coverage, we introduced the term
cluster size, which is the expected value of the area covered by a clusterhead together
with sensor nodes connected to it. We derived formulas for the cluster size and validated
them by computer simulations. By using the cluster size formulas, we proposed
a method to dimension a WSN for given targeted connected coverage.
Furthermore, we formulated cost optimization problems for direct and multi-hop
communication cases. These formulations utilize not only cluster size formulas but also
the well-connectivity concept. We suggested some search heuristics to solve these optimization
problems. Additionally, we justified that, in practical cases, node heterogeneity
can provide lower cost solutions. We also investigated the lifetime of WSNs and for
mulated a cost optimization problem with connected coverage and lifetime constraints.
By solving this optimization problem, one can determine the number of nodes of each
type and the initial energies of each type of node that leads to lowest cost solution while
satisfying the minimum connected coverage and minimum lifetime requirements.
21
Chaltseva, Anna. "Network state estimation in wireless multi-hop networks". Licentiate thesis, Luleå tekniska universitet, Datavetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-26357.
Testo completoAbstract (sommario):
Multi-hop wireless networks in general and those built upon IEEE 802.11 standard in particular are known for their highly dynamic and unstable performance. The commonly accepted way for improving the situation is to jointly optimize the performance of protocols across different communications layers. Being able to characterize a state of the network is essential to enable the cross-layer optimization. This licentiate thesis investigates methods for passive characterization of network state at medium access control and transport layers based on information accessible from the corresponding layers below.Firstly, the thesis investigates a possibility for characterizing traffic intensity relying solely on the statistics of measurements from the physical layer. An advantage of this method is that it does not require decoding of the captured packets, by this accounting for the effect from long-range interferences introduced by transmissions at the border of the communication range of a receiver.Secondly, a question of predicting TCP throughput over a multi-hop wireless path is addressed. The proposed predictor is a practically usable function of statistically significant parameters at transport, medium access control and physical communication layers. The presented model is able to predict the TCP throughput with 99% accuracy, which provides an essential input for various cross-layer optimization processes.Finally, during the course of the experimental work the issues of accuracy of simulation-based modeling of communication processes were investigated. The thesis is concluded by presenting a comparative study of the performance characteristics measured in a single channel multi-hop wireless network test-bed and the corresponding measurements obtained from popular network simulators ns-2 and ns-3 when configured with identical settings. The thesis presents the evaluation of the mismatch between the results obtained in the test-bed and the simulators with their standard empirical radio models.Godkänd; 2012; 20111215 (anncha); LICENTIATSEMINARIUM Ämnesområde: Datorkommunikation/Computer Networking Examinator: Docent Evgeny Osipov, Institutionen för system- och rymdteknik, Luleå tekniska universitet Diskutant: Universitetslektor Olov Schelén, Luleå tekniska universitet samt Xarepo AB, Luleå Tid: Måndag den 20 februari 2012 kl 10.00 Plats: A1514 Demostudion, Luleå tekniska universitet
22
Yuan, Fenghua. "Lightweight network management design for wireless sensor networks". Online access for everyone, 2007. http://www.dissertations.wsu.edu/Thesis/Fall2007/F_Yuan_081307.pdf.
Testo completo
23
Vu, Xuan Thang. "Joint Network / Channel Decoding over Noisy Wireless Networks". Phd thesis, Université Paris Sud - Paris XI, 2014. http://tel.archives-ouvertes.fr/tel-01060330.
Testo completoAbstract (sommario):
Network coding (NC) has gained much research attention as a potential candidate to solve the demand for higher spectral e ciency of modern wireless communications. Many research papers have investigated the performance of NC-aided networks such as throughput and outage capacity. However, the analysis of NC in practical systems where NC is combined with other techniques such as channel coding is still immature to fully understand its potential performance. In this thesis, we aim to design high performance receivers and analyze its performance for network-coded cooperative networks in practical scenarios. Firstly, we propose two Iterative Network/Channel Decoding (INCD) algorithms for the Multiple-Access Relay Channel (MARC) with two notable relaying schemes named Decode-and-Forward (DF) and Demodulate-and-Forward (DMF). The INCD algorithm operates based on turbo-like decoding methods and reduces the impact of the error propagation problem with the aid of a channel-aware receiver design. Both perfect Channel State Information (CSI) and imperfect CSI at the receiver side are investigated. We propose a practical method that forwards the quantized version of the relay decoding errors to the destination. It is shown that the proposed algorithms achieve full diversity gain and signi cantle outperforms solutions which do not take care of error propagation. We also show that the number of pilot symbols a ects only the coding gain but has a negligible impact on the diversity order, while the quantization level a cts both the diversity and coding gain. Secondly, we propose a Near Optimal Joint Network/Channel Decoding (NOJNCD) algorithm for the MARC that allows to analyze the system Bit Error Rate (BER). The NOJNCD algorithm performs network decoding and channel decoding in one decoding step of the super code, which comprises of all trellis states of individual code at the sources via NC. Furthermore, NC combined with Relay Selection (RS) is considered and the achievable diversity order is studied with the aid of outage analysis. We analytically show that Single Relay Selection (SRS) always achieves a diversity order two and Multiple Relay Selection (MRS) can achieve full diversity gain only when the number of selected relays exceeds the number of the sources. Last but not least, we propose a so-called partial relaying protocol to improve the spectral e ciency for channel coding assisted relay networks. Closed-form expression of the BER and the system diversity order are computed for partial relaying. We show, by analysis and simulations, that with a proper Convolutional Code (CC), partial relaying can achieve full diversity gain and same coding gain as the classical (full) relaying protocol in nite signal-to-noise ratio region while it obtains a better spectrum usage. Moreover, we propose a new protocol based on partial relaying in opportunistic relaying cooperative networks and show that this protocol signi cantly outperforms the NC-based cooperation in some circumstances.
24
Ahmed, Ebad. "Delay gains from network coding in wireless networks". Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/41253.
Testo completoAbstract (sommario):
Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2007.Includes bibliographical references (p. 73-77).
We consider a single-hop cellular wireless system with a single source (base station) broadcasting a stream of incoming files to multiple receivers over stochastic time-varying channels with non-zero erasure probabilities. The base station charges a price per receiver per file with the aim of maximizing its profit. Customers who wish to transmit files to the receivers decide to enter the system based on the price, the queuing delay, and the utility derived from the transaction. We look at network coding and scheduling as possible strategies for file transmission, and obtain approximate characterizations of the optimal customer admission rate, optimal price and the optimal base-station profit as functions of the first and second moments of the service time processes under mild assumptions. We show that network coding leads to significant gains in the base station profits as compared to scheduling, and also demonstrate that the optimal network coding window size is highly insensitive to the number of receivers, which suggests that pricing and coding decisions can be decoupled. We also investigate the behavior of network coding in the case where the number of receivers is sufficiently large, and derive scaling laws for the asymptotic gains from network coding. We subsequently propose a way to extend our analysis of single-source, multiple-receiver systems to multiple-source, multiple-receiver systems in general network topologies and obtain explicit characterizations of the file download completion time under network coding and scheduling, also taking into account the effects of collisions and interference among concurrent packet transmissions by two or more sources.
(cont.) Our formulation allows us to model multi-hop networks as a series of single-hop multiple-source, multiple-receiver systems, which provides a great deal of insight into the workings of larger and denser multi-hop networks such as overlay networks and peer-to-peer systems, and appears to be a promising application of network coding in such networks in the future.
by Ebad Ahmed.
M.Eng.
25
Fang, Dong. "Physical-layer network coding for cooperative wireless networks". Thesis, University of York, 2014. http://etheses.whiterose.ac.uk/6550/.
Testo completoAbstract (sommario):
As a newly-emerged paradigm in the networking techniques, physical-layer network coding (PNC) [1, 5] takes advantage of the superimposition of the electromagnetic waves, and embraces the interference which was typically deemed as harmful, by performing exclusive-or mapping. Therefore, the spectral efficiency is utilized, which in turn boosts the network throughput. In the classical 2-way relay channel (2-WRC), PNC only spends two channel uses for the bi-directional data exchange. However, one challenge for such a paradigm is that the singular fading states in the uplink of 2-WRC, might result in ambiguity for decoding the network coded symbol. One major focus of this thesis is to address the fading issue for PNC in the 2-WRC. Another fundamental challenge for PNC is to extend the PNC from the 2-WRC to a multi-user network such as the multi-way relay channel (M-WRC) or the hierarchical wireless network (HWN). To tackle these two fundamental challenges of PNC, several solutions are proposed in this thesis, which are summarized as follows: First, we introduce two efficient fading correction strategies, i.e., the rotationally-invariant coded modulation and the soft-bit correction. Second, a novel multilevel coded linear PNC scheme with extended mapping for the Rayleigh fading 2-WRC is proposed. Third, we design a new type of linear PNC for the Rayleigh fading 2-WRC, based on rings. We refer to such design as linear PNC over the hybrid finite ring. Fourth, we redesign PNC for the HWN, which facilitates the multi-user data exchange. To combat the co-channel interference introduced by multi-user data exchange, two efficient interference exploitation strategies based on network coding are proposed: 1) PNC with joint decoding; and 2) analogue network coding with interference-aware maximum likelihood detection. Finally, we propose a multilevel coded LPNC for the data exchange in the M-WRC.
26
Susanto, Misfa. "Network Coding for Multihop Wireless Networks: Joint Random Linear Network Coding and Forward Error Correction with Interleaving for Multihop Wireless Networks". Thesis, University of Bradford, 2015. http://hdl.handle.net/10454/14864.
Testo completoAbstract (sommario):
Optimising the throughput performance for wireless networks is one of the challenging tasks in the objectives of communication engineering, since wireless channels are prone to errors due to path losses, random noise, and fading phenomena. The transmission errors will be worse in a multihop scenario due to its accumulative effects. Network Coding (NC) is an elegant technique to improve the throughput performance of a communication network. There is the fact that the bit error rates over one modulation symbol of 16- and higher order- Quadrature Amplitude Modulation (QAM) scheme follow a certain pattern. The Scattered Random Network Coding (SRNC) system was proposed in the literature to exploit the error pattern of 16-QAM by using bit-scattering to improve the throughput of multihop network to which is being applied the Random Linear Network Coding (RLNC). This thesis aims to improve further the SRNC system by using Forward Error Correction (FEC) code; the proposed system is called Joint RLNC and FEC with interleaving. The first proposed system (System-I) uses Convolutional Code (CC) FEC. The performances analysis of System-I with various CC rates of 1/2, 1/3, 1/4, 1/6, and 1/8 was carried out using the developed simulation tools in MATLAB and compared to two benchmark systems: SRNC system (System-II) and RLNC system (System- III). The second proposed system (System-IV) uses Reed-Solomon (RS) FEC code. Performance evaluation of System IV was carried out and compared to three systems; System-I with 1/2 CC rate, System-II, and System-III. All simulations were carried out over three possible channel environments: 1) AWGN channel, 2) a Rayleigh fading channel, and 3) a Rician fading channel, where both fading channels are in series with the AWGN channel. The simulation results show that the proposed system improves the SRNC system. How much improvement gain can be achieved depends on the FEC type used and the channel environment.
27
Dai, Lillian Lei 1978. "Proactive mobile wireless networks : an infrastructureless wireless network architecture for delay-sensitive applications". Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/44409.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2008.Includes bibliographical references (p. 197-213).
Infrastructureless wireless networks are an important class of wireless networks that is best suited for scenarios where there is temporary and localized telecommunication demand. Such networks consist of wireless devices that can form a network autonomously without the need for pre-deployed telecommunication infrastructures such as base-stations and access points. Over the past several decades, significant research and development efforts have been devoted to a particular type of infrastructureless wireless networks called mobile ad hoc wireless networks (MANETs). In addition to autonomous network formation, wireless devices in MANETs have routing capabilities and help one another to forward information in a multihop fashion. The applications envisioned for MANETs include communication during disaster relief, search and rescue, and small tactical unit operations where the existing telecommunication infrastructures may be destroyed or are unavailable. While significant strides have been made in all aspects of MANET networking, adoption of such technology has been limited to date despite its potential. We believe that this lack of adoption is due to a fundamental mismatch between application demands and the MANET network architecture. While the flexibility of anytime and anywhere communication offered by MANETs is appealing, these networks are not designed to provide assured service for delay-sensitive applications such as communication during a search and rescue mission or in a battlefield. In fact, MANETs may be frequently disconnected due to mobility and/or device failure. Such disconnections may persist for an unacceptable length of time, during which, there may be loss of critical time-sensitive information and degraded network performance due to mismatches to routing and transport layer protocols.
(cont.) To provide service assurance in these scenarios, it is insufficient to limit technical improvements to the traditional networking layers (such as power control, coding, or routing) since network disconnections may still occur. We argue that a Proactive Wireless Network Architecture is needed - one that proactively maintains network connectivity in order to provide assured message delivery for applications with high quality of service (QoS) demands. The two key features of a proactive wireless network are: (1) Network disconnection prediction via localization, trajectory prediction, and large-scale channel estimation and (2) Network topology control via the adaptive deployment of additional wireless devices, called helper nodes, and by proactively controlling their movements toward regions of predicted disconnections prior to the occurrence of such disconnections. Hence, unlike MANETs, proactive wireless networks are designed to anticipate and respond to network disconnection events via active connectivity maintenance with helper nodes, thereby preventing network disruptions and message loss. In this dissertation, we present the proposed proactive wireless network architecture, quantify operating scenarios where the proposed network architecture is a sensible choice, and present system-level performance analyses under various helper node deployment schemes.
by Lillian Lei Dai.
Ph.D.
28
Yazar, Dogan. "RESTful Wireless Sensor Networks". Thesis, Uppsala University, Department of Information Technology, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-110353.
Testo completoAbstract (sommario):
Sensor networks have diverse structures and generally employ proprietary protocols to gather useful information about the physical world. This diversity generates problems to interact with these sensors since custom APIs are needed which are tedious, error prone and have steep learning curve. In this thesis, I present RESThing, a lightweight REST framework for wireless sensor networks to ease the process of interacting with these sensors by making them accessible over the Web. I evaluate the system and show that it is feasible to support widely used and standard Web protocols in wireless sensor networks. Being able to integrate these tiny devices seamlessly into the global information medium, we can achieve the Web of Things.
29
Tasdelen, Yakup. "Wireless Networks Performance Study". Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605234/index.pdf.
Testo completoAbstract (sommario):
This thesis evaluates the performance of the 802.11 wireless network. The newly defined DCF+ protocol performance is studied and compared with the DCF protocol under different traffic conditions. A service differentiation mechanism is also applied to both protocols for basic access mechanism and the efficiency of the protocols is examined. As an additional work, the same study is performed for RTS/CTS access scheme and efficiency of the protocols is examined
As a result of this study, it is shown that the DCF+ protocol provides performance enhancement to the DCF protocol under different traffic conditions but fails to provide service differentiation because of its structure.
30
Seddigh, Mahtab. "Broadcasting in wireless networks". Thesis, University of Ottawa (Canada), 2001. http://hdl.handle.net/10393/9234.
Testo completoAbstract (sommario):
This work examines the problem of providing reliable broadcast delivery of messages with minimal communication overhead in wireless networks. We consider two types of communication for broadcasting: one-to-all (the classical form of broadcasting where each node forwards the message to all its neighbours with one transmission) and one-to-one (each transmission forwards the message to only one neighbour at a time). We propose to reduce the communication overhead involved in both these forms of broadcasting by applying the concept of internal nodes. We simulate and analyze the performance of a family of three algorithms we propose for the one-to-all model using internal nodes. Neighbour elimination is used to reduce redundant rebroadcasts, and reliability is almost guaranteed with the introduction of RANA (Retransmission after negative acknowledgement). For the one-to-one model, in addition to applying the internal nodes concept, three additional algorithms P-broadcast, IP-broadcast and PI-broadcast are proposed based on the concept of planar subgraphs such as RNG (relative neighbourhood graphs). We compare the relative performance of these proposed approaches against those presented in literature. (Abstract shortened by UMI.)
31
Abdalla, Taha. "Scalable Wireless Mesh Networks". University of the Western Cape, 2016. http://hdl.handle.net/11394/5868.
Testo completoAbstract (sommario):
Magister Scientiae - MSc (Computer Science)Wireless Mesh Networks (WMNs) are wireless multi-hop networks built on wireless nodes that operate in an Independent Basic Set Identifier (IBSS) mode of the IEEE 208.11 wireless standard. IBSS is well known as an ad hoc mode which is found to build ad hoc wireless networks with the aid of routing protocols crafted to work in this mode. Ad hoc wireless mesh networks are always described as self-healing, self-configuring, easy to build, etc. However, these features do come at a cost because a WMN suffers performance degradation and scalability issues, which mainly come from the underlying IBSS mode that is used to form the physical network. Furthermore this is exacerbated by routing protocols in the upper layers which are intended to form a flat network architecture. Partitioning or clustering the flat network into smaller units has been proven to be a viable mechanism to counter the scalability problem in the communication network. The wired network for instance, presents a segmented, hierarchical architecture, where end user devices are organized in virtual local area networks (VLANs) using Ethernet switches and then Routers aggregate multiple VLANs. This thesis develops and evaluates a heterogeneous, clustering architecture to enhance WMN scalability and management. In the proposed architecture, the clustering is separated from the routing, where the clustering is done at the physical layer. At the routing level, each cluster is configured as a WMN using layer 2 routing for intra-cluster routing, and layer 3 routing for inter-domain routing between clusters. Prototypes for the proposed architecture have been built in a laboratory testbed. The proposed architecture reported better scalability and performance results compared to the traditional flat architecture.
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Theodorou, Pavlos. "ATM optical wireless networks". Thesis, Northumbria University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248929.
Testo completo
33
Mohd, Sultan Juwita. "Hybrid wireless broadband networks". Thesis, Lancaster University, 2016. http://eprints.lancs.ac.uk/78762/.
Testo completoAbstract (sommario):
A hybrid system is an integration of two or more different systems, particularly in this thesis referring to wireless broadband networks. However, to provide end-to-end quality of service (QoS) in a hybrid system is a challenging task due to different protocol in each system. In this thesis, we aim to improve the overall performance of hybrid networks in a disaster management by addressing the challenges as well as the problems in a homogeneous network. Such an approach allows more efficient multi-parameter optimization and significant improvements in the overall system performance. More specifically, we introduce two novel algorithms. The first is the novel end-to-end QoS algorithm for hybrid wireless broadband networks. We proposed the end-to-end QoS maps based on particular chosen parameters and analyse the simulation results. The QoS maps are applied to a few scenarios, and the performance evaluation of the constructed network is presented. Based on the results obtained by software simulation tools, the performance validation shows that the hybrid network has specific advantages and constraints in terms of number of users, preference, coverage and applications. The second algorithm presented is the novel in users’ application algorithm, the purpose of which is to optimize bandwidth for first responders applied in the PPDR project under grant agreement EU FP7 SEC PPDR-TC. This algorithm is responsible for incorporating more users and different levels of background load to a hybrid network. The proposed method analyses both positive and negative outcomes based on the results obtained. This algorithm has been presented in the PPDR project.
34
Rehman, Shafqat Ur. "Benchmarking in wireless networks". Nice, 2012. http://www.theses.fr/2012NICE4003.
Testo completoAbstract (sommario):
L’objectif principal de cette thèse est d’obtenir une comparaison réaliste et équitable des performances des protocoles et des applications pour les réseaux sans fil. Dans la communauté réseau, la simulation est l’approche prédominante pour l’évaluation comparative des protocoles, cependant, elle manque de réalisme car elle utilise le plus souvent des modèles simplifiés des couches de communication. D’un autre côté, les expérimentations sans fil effectuées dans le monde réel sont réalistes mais elles compliquent fortement la comparaison équitable des protocoles. En effet, la comparaison équitable des protocoles dépend de l’interprétation correcte des résultats et de la « répétabilité » de l’expérimentation. L’interprétation correcte des résultats est un problème majeur pour les expérimentations sans fil car il n’est pas facile de tenir compte de l’ensemble des paramètres qui peuvent avoir un impact sur les performances des protocoles en particulier, les conditions du canal, les paramètres de configuration des outils de mesure. Avec les expérimentations sans fil, la « répétabilité » des résultats est quasiment impossible à obtenir en raison du caractère aléatoire du canal de transmission. Quant à la « comparaison équitable » des protocoles, elle est complexe à obtenir et nécessite une méthodologie standard. Dans cette thèse, nous proposons une méthodologie d’expérimentation dont l’objectif est d’assurer une interprétation correcte des résultats expérimentaux. Cette méthodologie est composée des étapes suivantes : caractérisation de canal pour déterminer les conditions exactes de canal, calibrage des outils de mesure, spécification de la configuration du scénario à l’aide d’outils simples. Dans les expérimentations sans fil, les ondes radio sont affectées par des phénomènes multiples et complexes comme l’atténuation en fonction de la distance, les réflexions sur le sol ou les murs qui peuvent provoquer l’évanouissement du signal. De plus, le déplacement d’objet ou de personnes entre émetteurs et récepteurs et à la proximité d’autres réseaux sans fil peuvent introduire des interférences que l’on ne peut pas ignorer. D’autres part, les expérimentateur peuvent facilement faire des erreurs si les outils et les logiciels utilisés sont mal configurés. Pour cela, il est important de spécifier de manière précise et détaillée le scénario d’expérimentation. Cette spécification doit inclure la séquence des étapes et la description des tâches à effectuer à chaque étape de l’expérimentation. Les tâches comprennent la génération de trafic, la capture des paquets (e. G. à l’aide de sondes), la capture de traces RF (e. G. Avec un analyseur de spectre) et la collecte d’autres mesures, comme la charge CPU des machines utilisées. Pour interpréter correctement les résultats, comme ces informations peuvent être très volumineuses, elles doivent être organisées et présentées de manière efficace. Dans cet objectif, nous proposons l’établissement d’un rapport détaillé appelé FDR (« Full Disclosure Report »). Comme la « répétabilité » des expérimentations sans fil est impossible à obtenir dans un environnement non contrôlé, notre objectif est de pouvoir répéter des résultats statistiques. Ces derniers sont obtenus en regroupant les résultats d’expérimentations multiples qui ont eu lieu avec des conditions d’environnement similaire. Etant donné que les expérimentations sans fil sont fastidieuses à réaliser et sujettes aux erreurs humaines, nous avons développé une boîte à outils permettant de faciliter le benchmark. Ces outils permettent de décrire les scénarios, gérer la planification d’un grand nombre d’expérimentations et traiter l’énorme quantité de traces qui en résultent, sauvegarder les métadonnées et leur provenance (enregistrement chronologique des étapes de mesure et d’analyse), ainsi que les résultats d’expérimentation. Enfin, nous illustrons et validons notre méthodologie de benchmark avec deux cas d’étudeThe objective of this thesis is to enable realistic yet fair comparison of the performance of protocols and applications in wireless networks. Simulation is the predominant approach for comparable evaluation of networking protocols however it lacks realism and can lead to misleading results. Real-world experiments guarantee realism but complicate fair comparison. Fair comparison depends on correct interpretation of the results and repeatability of the experiment. Correct interpretation of results is an issue in wireless experiments because it is not easy to record all the factors (e. G. Channel condition s, calibration settings tools and test scenario configurations) that can influence the network performance. Repeatability of experiments is almost impossible because of channel randomness. In wireless experiments, “realism” can be taken of granted but “fair comparison” requires a lot of hard work and is impossible without a standard methodology. Therefore, we design a workable experimentation methodology which tackles the aforementioned issues as follows. To ensure correct interpretation of the results, we need to accomplish the following : channel characterization to determine the exact channel conditions, calibration of tools to avoid pitfalls, a simple mechanism to specify scenario configurations. Channel conditions such as path loss, fading an interference are a direct result of radio propagation, movement of objects and co-existing Wi-Fi networks/devices in the environment respectively. Pitfalls mainly result from imperfections / bugs or wrong configurations of a tool. Scenario description consists of a precise specification of the sequence of steps and tasks to be performed at each step. Tasks include traffic generation, packet trace capture (using a sniffer). RF traces capture (using spectrum analyzer) and System/network workload collection. Correct interpretation of results requires that all this information be organized and presented in an easily digestible way to the reviewer. We propose Full disclosure report (FDR) for this purpose. Repeatable experimentation requires additional work. As repeatability is impractical in the wild wireless environment, we propose statistical repeatability of results where experiments are clustered based on the similarity of networking conditions (channel conditions, station workload, network traffic load) and scenario configurations. The, it is possible to make a comparison based on the similarity of conditions. Providing tools to allow a user-friendly mechanism to apply the methodology is also equally important. We need tools to easily describe scenarios, manage scheduling and large number of runs (possibly hundreds or thousands) of them. We also need tools to manage huge amount of packet trace data, metadata and provenance (chronological record of measurement and analysis steps) of results (figures, tables, graphs etc. ). Therefore, in addition to the methodology, we developed a toolbox for a wireless experimentation and carried out of two case studies to validate the methodology. In short, we present a holistic view of benchmarking in wireless networks, formulate a methodology complemented by tools and case studies to help drive future efforts on benchmarking of protocols and applications in wireless networks
35
Barreto, Luís Manuel Cerqueira. "Wireless networks congestion control". Doctoral thesis, Universidade de Aveiro, 2012. http://hdl.handle.net/10773/9001.
Testo completoAbstract (sommario):
Doutoramento em Engenharia ElectrotécnicaCongestion control in wireless networks is an important and open issue. Previous research has proven the poor performance of the Transport Control Protocol (TCP) in such networks. The factors that contribute to the poor performance of TCP in wireless environments concern its unsuitability to identify/detect and react properly to network events, its TCP window based ow control algorithm that is not suitable for the wireless channel, and the congestion collapse due to mobility. New rate based mechanisms have been proposed to mitigate TCP performance in wired and wireless networks. However, these mechanisms also present poor performance, as they lack of suitable bandwidth estimation techniques for multi-hop wireless networks. It is thus important to improve congestion control performance in wireless networks, incorporating components that are suitable for wireless environments. A congestion control scheme which provides an e - cient and fair sharing of the underlying network capacity and available bandwidth among multiple competing applications is crucial to the definition of new e cient and fair congestion control schemes on wireless multi-hop networks. The Thesis is divided in three parts. First, we present a performance evaluation study of several congestion control protocols against TCP, in wireless mesh and ad-hoc networks. The obtained results show that rate based congestion control protocols need an eficient and accurate underlying available bandwidth estimation technique. The second part of the Thesis presents a new link capacity and available bandwidth estimation mechanism denoted as rt-Winf (real time wireless inference). The estimation is performed in real-time and without the need to intrusively inject packets in the network. Simulation results show that rt-Winf obtains the available bandwidth and capacity estimation with accuracy and without introducing overhead trafic in the network. The third part of the Thesis proposes the development of new congestion control mechanisms to address the congestion control problems of wireless networks. These congestion control mechanisms use cross layer information, obtained by rt-Winf, to accurately and eficiently estimate the available bandwidth and the path capacity over a wireless network path. Evaluation of these new proposed mechanisms, through ns-2 simulations, shows that the cooperation between rt-Winf and the congestion control algorithms is able to significantly increase congestion control eficiency and network performance.
O controlo de congestionamento continua a ser extremamente importante quando se investiga o desempenho das redes sem fios. Trabalhos anteriores mostram o mau desempenho do Transport Control Proto- col (TCP) em redes sem fios. Os fatores que contribuem para um pior desempenho do TCP nesse tipo de redes s~ao: a sua falta de capacidade para identificar/detetar e reagir adequadamente a eventos da rede; a utilização de um algoritmo de controlo de uxo que não é adequado para o canal sem fios; e o colapso de congestionamento devido á mobilidade. Para colmatar este problemas foram propostos novos mecanismos de controlo de congestionamento baseados na taxa de transmissão. No entanto, estes mecanismos também apresentam um pior desempenho em redes sem fios, já que não utilizam mecanismos adequados para a avaliação da largura de banda disponível. Assim, é importante para melhorar o desempenho do controlo de congestionamento em redes sem fios, incluir componentes que são adequados para esse tipo de ambientes. Um esquema de controlo de congestionamento que permita uma partilha eficiente e justa da capacidade da rede e da largura de banda disponível entre múltiplas aplicações concorrentes é crucial para a definição de novos, eficientes e justos mecanismos de controlo congestionamento para as redes sem fios. A Tese está dividida em três partes. Primeiro, apresentamos um estudo sobre a avaliação de desempenho de vários protocolos de controlo de congestionamento relativamente ao TCP, em redes sem fios em malha e ad-hoc. Os resultados obtidos mostram que os protocolos baseados na taxa de transmissão precisam de uma técnica de avaliação da largura de banda disponível que seja eficiente e precisa . A segunda parte da Tese apresenta um novo mecanismo de avaliação da capacidade da ligação e da largura de banda disponível, designada por rt-Winf (real time wireless inference). A avaliação é realizada em tempo real e sem a necessidade de inserir tráfego na rede. Os resultados obtidos através de simulação e emulação mostram que o rt-Winf obtém com precisão a largura de banda disponível e a capacidade da ligação sem sobrecarregar a rede. A terceira parte da Tese propõe novos mecanismos de controlo de congestionamento em redes sem fios. Estes mecanismos de controlo de congestionamento apresentam um conjunto de caracter ísticas novas para melhorar o seu desempenho, de entre as quais se destaca a utilização da informação de largura de banda disponível obtida pelo rt-Winf. Os resultados da avaliação destes mecanismos, utilizando o simulador ns-2, permitem concluir que a cooperação entre o rt-Winf e os algoritmos de controlo de congestionamento aumenta significativamente o desempenho da rede.
36
Gao, Zihao. "Wireless Powered Communication Networks". Thesis, The University of Sydney, 2017. http://hdl.handle.net/2123/17169.
Testo completoAbstract (sommario):
The limited life time of batteries is a crucial issue in energy-constrained wireless communications. Recently, the radio frequency (RF) wireless energy transfer (WET) technique has been developed as a new practical method to extend the life time of wireless communication networks. Inspired by this, wireless-powered communication network (WPCN) has attracted much attention. Therefore, in this thesis, we consider practical WET and wireless-powered information transmission in WPCNs. First we investigate a WPCN with two nodes, in which an access point (AP) exchanges information with a wireless-powered user. The user is assumed to have no embedded energy supply and needs to harvest energy from RF signals broadcast by the AP. Differing from existing work that focuses on the design of wireless-powered communication with one-way information flow, we deal with a more general scenario where both the AP and the user have information to transmit. Considering that the AP and user can work in either half-duplex or full-duplex mode as well as having two practical receiver architectures at the user side, we propose five elementary communication protocols for the considered system. Moreover, we define the concept of a throughput region to characterize the tradeoff between the uplink and downlink throughput in all proposed protocols. Numerical simulations are finally performed to compare the throughput regions of the proposed five elementary protocols. To further the study on WPCN, we investigate a wireless-powered two-way relay system, in which two wireless-powered sources exchange information through a multi-antenna relay. Both sources are assumed to have no embedded energy supply and thus first need to harvest energy from the radio frequency signals broadcast by the relay before exchanging their information via the relay. We aim to maximize the sum throughput of both sources by jointly optimizing the time switching duration, the energy beamforming vector and the precoding matrix at the relay. The formulated problem is non-convex and hard to solve in its original form. Motivated by this, we simplify the problem by reducing the number of variables and by decomposing the precoding matrix into a transmit vector and a receive vector. We then propose a bisection search, a 1-D search and an iterative algorithm to optimize each variable. Numerical results show that our proposed scheme can achieve higher throughput than the conventional scheme without optimization on the beamforming vector and precoding matrix at the relay. Due to the high attenuation of RF energy over a long distance, RF based wireless-powered communication is usually designed for low-power scenarios, e.g., wireless-powered sensor networks. Recently, magnetic induction (MI) based WET has been proposed to wirelessly transfer a large amount of energy. Inspired by this, we investigate MI based WET in WPCN. Specifically, we study a MI based wireless-powered relaying network, in which a MI source transmits information to a MI destination, with the help of a MI based wireless powered relay. We propose four active relaying schemes, which consider different relaying modes and different energy harvesting receiver architectures at the relay. We then aim to maximize the end-to-end throughput of each scheme by using a bisection search, a water-filling algorithm, a Lagrange multiplier, quasi-convex programming and an iterative algorithm. We compare the proposed active relaying schemes with passive relaying. Numerical results show that the proposed relaying schemes with a decode-and-forward relaying mode significantly improve the throughput over passive relaying.
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Decarli, Nicolò <1985>. "Context-aware wireless networks". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amsdottorato.unibo.it/5613/1/decarli_nicolo_tesi.pdf.
Testo completoAbstract (sommario):
This thesis investigates context-aware wireless networks, capable to adapt their behavior to the context and the application, thanks to the ability of combining communication, sensing and localization. Problems of signals demodulation, parameters estimation and localization are addressed exploiting analytical methods, simulations and experimentation, for the derivation of the fundamental limits, the performance characterization of the proposed schemes and the experimental validation.
Ultrawide-bandwidth (UWB) signals are in certain cases considered and non-coherent receivers, allowing the exploitation of the multipath channel diversity without adopting complex architectures, investigated. Closed-form expressions for the achievable bit error probability of novel proposed architectures are derived.
The problem of time delay estimation (TDE), enabling network localization thanks to ranging measurement, is addressed from a theoretical point of view. New fundamental bounds on TDE are derived in the case the received signal is partially known or unknown at receiver side, as often occurs due to propagation or due to the adoption of low-complexity estimators. Practical estimators, such as energy-based estimators, are revised and their performance compared with the new bounds.
The localization issue is addressed with experimentation for the characterization of cooperative networks. Practical algorithms able to improve the accuracy in non-line-of-sight (NLOS) channel conditions are evaluated on measured data. With the purpose of enhancing the localization coverage in NLOS conditions, non-regenerative relaying techniques for localization are introduced and ad hoc position estimators are devised.
An example of context-aware network is given with the study of the UWB-RFID system for detecting and locating semi-passive tags. In particular a deep investigation involving low-complexity receivers capable to deal with problems of multi-tag interference, synchronization mismatches and clock drift is presented. Finally, theoretical bounds on the localization accuracy of this and others passive localization networks (e.g., radar) are derived, also accounting for different configurations such as in monostatic and multistatic networks.
38
Decarli, Nicolò <1985>. "Context-aware wireless networks". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amsdottorato.unibo.it/5613/.
Testo completoAbstract (sommario):
This thesis investigates context-aware wireless networks, capable to adapt their behavior to the context and the application, thanks to the ability of combining communication, sensing and localization. Problems of signals demodulation, parameters estimation and localization are addressed exploiting analytical methods, simulations and experimentation, for the derivation of the fundamental limits, the performance characterization of the proposed schemes and the experimental validation.
Ultrawide-bandwidth (UWB) signals are in certain cases considered and non-coherent receivers, allowing the exploitation of the multipath channel diversity without adopting complex architectures, investigated. Closed-form expressions for the achievable bit error probability of novel proposed architectures are derived.
The problem of time delay estimation (TDE), enabling network localization thanks to ranging measurement, is addressed from a theoretical point of view. New fundamental bounds on TDE are derived in the case the received signal is partially known or unknown at receiver side, as often occurs due to propagation or due to the adoption of low-complexity estimators. Practical estimators, such as energy-based estimators, are revised and their performance compared with the new bounds.
The localization issue is addressed with experimentation for the characterization of cooperative networks. Practical algorithms able to improve the accuracy in non-line-of-sight (NLOS) channel conditions are evaluated on measured data. With the purpose of enhancing the localization coverage in NLOS conditions, non-regenerative relaying techniques for localization are introduced and ad hoc position estimators are devised.
An example of context-aware network is given with the study of the UWB-RFID system for detecting and locating semi-passive tags. In particular a deep investigation involving low-complexity receivers capable to deal with problems of multi-tag interference, synchronization mismatches and clock drift is presented. Finally, theoretical bounds on the localization accuracy of this and others passive localization networks (e.g., radar) are derived, also accounting for different configurations such as in monostatic and multistatic networks.
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Antonopoulos, Angelos. "Network coding-aided MAC protocols for cooperative wireless networks". Doctoral thesis, Universitat Politècnica de Catalunya, 2012. http://hdl.handle.net/10803/97094.
Testo completoAbstract (sommario):
The introduction of third generation (3G) technologies has caused a vast proliferation of wireless devices and networks, generating an increasing demand for high level Quality of Service (QoS). The wide spread of mobile applications has further reinforced the user need for communication, motivating at the same time the concepts of user cooperation and data dissemination. However, this trend towards continuous exchange of information and ubiquitous connectivity is inherently restricted by the energy-greedy functionalities of high-end devices. These limitations, along with the pressure exerted on the Information and Communications Technology (ICT) industry towards energy awareness, have induced the design of novel energy efficient schemes and algorithms. In this context, the Medium Access Control (MAC) layer plays a key role, since it is mainly responsible for the channel access regulation, the transmission scheduling and the resource allocation, thus constituting an appropriate point to effectively address energy efficiency issues that arise due to the users overcrowding.
This dissertation provides a contribution to the design, analysis and evaluation of novel MAC protocols for cooperative wireless networks. In our attempt to design energy efficient MAC schemes, we were extensively assisted by the introduction of new techniques, such as Network Coding (NC), that intrinsically bring considerable gains in system performance. The main thesis contributions are divided into two parts. The first part presents NCCARQ, a novel NC-aided Cooperative Automatic Repeat reQuest (ARQ) MAC protocol for wireless networks. NCCARQ introduces a new access paradigm for cooperative ARQ schemes, exploiting NC benefits in bidirectional communication among wireless users. The NCCARQ performance in terms of QoS and energy efficiency is assessed by means of analytical probabilistic models and extensive computer-based simulations, revealing the significant gains we can achieve compared to standardized MAC solutions. In addition, the impact of realistic wireless channel conditions on the MAC protocol operation further motivated us to study the NCCARQ performance in wireless links affected by correlated shadowing, showing that the channel correlation may adversely affect the distributed cooperation benefits.
The second part of the thesis is dedicated to the investigation of MAC issues in wireless data dissemination scenarios. In particular, the existence of multiple source nodes in such scenarios generates conflicting situations, considering the selfish behavior of the wireless devices that want to maximize their battery lifetime. Bearing in mind the energy efficiency importance, we propose game theoretic medium access strategies, applying energy-based utility functions which inherently imply energy awareness. In addition, Random Linear NC (RLNC) techniques are adopted to eliminate the need of exchanging excessive control packets, while Analog NC (ANC) is employed to efface the impact of collisions throughout the communication.
During the elaboration of this thesis, two general key conclusions have been extracted. First, there is a fundamental requirement for implementation of new MAC protocols in order to effectively deal with state-of-the-art techniques (e.g., NC), recently introduced to enhance both the performance and the energy efficiency of the network. Second, we highlight the importance of designing novel energy efficient MAC protocols, taking into account that traditional approaches - designed mainly to assist the collision avoidance in wireless networks - tend to be obsolete.La presente tesis doctoral contribuye al diseño, análisis y evaluación de nuevos protocolos MAC cooperativos para redes inalámbricas. La introducción de nuevas técnicas, tales como la codificación de red (NC), que intrínsecamente llevan un considerable aumento en el rendimiento del sistema, nos ayudó ampliamente durante el diseño de protocolos MAC energéticamente eficientes. Las principales contribuciones de esta tesis se dividen en dos partes. La primera parte presenta el NCCARQ, un protocolo cooperativo de retransmisión automática (ARQ), asistido por NC para redes inalámbricas. La segunda parte de la tesis se centra en el diseño de protocolos de capa MAC en escenarios inalámbricos de difusión de datos. Teniendo en cuenta la importancia de la eficiencia energética, se proponen técnicas de acceso al medio basadas en teoría de juegos dónde las funciones objetivo están motivadas por el consumo energético. Las soluciones propuestas son evaluadas por medio de modelos analíticos y simulaciones por ordenador.
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She, Huimin. "Network-Calculus-based Performance Analysis for Wireless Sensor Networks". Licentiate thesis, KTH, Electronic, Computer and Software Systems, ECS, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-10686.
Testo completoAbstract (sommario):
Recently, wireless sensor network (WSN) has become a promising technologywith a wide range of applications such as supply chain monitoringand environment surveillance. It is typically composed of multiple tiny devicesequipped with limited sensing, computing and wireless communicationcapabilities. Design of such networks presents several technique challengeswhile dealing with various requirements and diverse constraints. Performanceanalysis techniques are required to provide insight on design parametersand system behaviors.
Based on network calculus, we present a deterministic analysis methodfor evaluating the worst-case delay and buffer cost of sensor networks. Tothis end, three general traffic flow operators are proposed and their delayand buffer bounds are derived. These operators can be used in combinationto model any complex traffic flowing scenarios. Furthermore, the methodintegrates a variable duty cycle to allow the sensor nodes to operate at lowrates thus saving power. In an attempt to balance traffic load and improveresource utilization and performance, traffic splitting mechanisms areintroduced for mesh sensor networks. Based on network calculus, the delayand buffer bounds are derived in non-splitting and splitting scenarios.In addition, analysis of traffic splitting mechanisms are extended to sensornetworks with general topologies. To provide reliable data delivery in sensornetworks, retransmission has been adopted as one of the most popularschemes. We propose an analytical method to evaluate the maximum datatransmission delay and energy consumption of two types of retransmissionschemes: hop-by-hop retransmission and end-to-end retransmission.
We perform a case study of using sensor networks for a fresh food trackingsystem. Several experiments are carried out in the Omnet++ simulationenvironment. In order to validate the tightness of the two bounds obtainedby the analysis method, the simulation results and analytical results arecompared in the chain and mesh scenarios with various input traffic loads.From the results, we show that the analytic bounds are correct and tight.Therefore, network calculus is useful and accurate for performance analysisof wireless sensor network.
Ipack VINN Excellence Center
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Hildebrand, Matthias [Verfasser]. "Optimized network access in heterogeneous wireless networks / Matthias Hildebrand". Kassel : Kassel Univ. Press, 2005. http://d-nb.info/977677540/34.
Testo completo
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Samarasinghe, Kasun. "Network Coding with Limited Overhearing in Wireless Sensor Networks". Thesis, KTH, Kommunikationsnät, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-53518.
Testo completoAbstract (sommario):
Network Coding as a recently emerged concept in Communication Networks Research, has attracted a lot of attention in networking research community. Previous research on applying Network Coding in Wireless Sensor Networks, do not consider most crucial constraints inherent to sensor networks. Especially most of them assume overhearing of neighboring transmissions for free, which is unrealistic in practical sensor network environments where nodes have limited energy. Therefore these applications fail to make an impact on real world sensor network deployments. In some sensor networking scenarios it is possible to manipulate overhearing in a controlled manner. In this research we apply network coding in to improve throughput of a Time Division Multiple Access(TDMA) based Medium Access Control(MAC) protocol called GINMAC , manipulating overhearing appropriately. Our results show that network coding can improve the throughput while trading owith other network performance characteristics like reliability and power consumption.
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Brännström, Robert. "Network-layer mobility in wireless ad hoc access networks". Licentiate thesis, Luleå tekniska universitet, Datavetenskap, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-17093.
Testo completoAbstract (sommario):
This thesis proposes and discusses solutions to enable network-layer mobility in wireless ad hoc access networks. The deployment of wireless access networks has made them ubiquitous and current research strives to make them pervasive. Users having wireless access to wired IP networks and the Internet are driving the demand for mobile and heterogeneous solutions. To enable all kinds of mobility in heterogeneous All-IP networks there are many issues to be solved. This thesis focuses on network-layer mobility and connectivity of wireless multi-hop ad hoc networks to the Internet. In a wireless environment with overlapping service areas, mobile hosts need to select which gateway(s) to use to access the wireless infrastructure. The signal-to-noise ratio of an access point, which is part of a wireless LAN, does not reflect the number of attached hosts or the traffic between them. The throughput of the access point could be low while the signal is strong. At the same time an access point with weaker signal could allow higher throughput. In ad hoc routing, hop count is the most common metric and the selection of a route to a gateway is affected by the same utilization problem. This could lead to a situation where a short route is used by more hosts and performing worse than a longer route serving fewer hosts. This thesis proposes and discusses solutions to calculating network-layer metrics and using them in gateway selection and handover decisions. To enable connectivity of a mobile ad hoc network (MANET) to the Internet, a gateway must support the wired single-hop and wireless multi-hop approaches. To deploy network-layer mobility in a MANET, the Mobile IP protocol needs to be adapted for the multi-hop environment. A MANET enables connectivity to more than one gateway at a time and combined with multihoming it provides seamless handover between subnets. The gateway selection and handover decisions are complicated by the multihoming capabilities. This thesis proposes and discusses solutions to deploying multihomed mobility into MANETs and thereby handling multi-hop gateway discovery, registration of multiple gateways and tunneling to selected gateway(s). Traffic patterns in wired LANs generally follow the 80/20 ratio of Internet destined vs. local traffic. The same traffic patterns generally hold true for wireless hosts. Therefore it is important to maintain the route to the gateway for the Internet destined traffic. This thesis proposes and discusses a solution to maintaining gateway connectivity in MANETs by installing routes to gateways using advertisements. Deciding the locality of a peer and setting up the forwarding route differs between single-hop and multi-hop networks. In single-hop networks a source matches the destination prefix with its own to decide what forwarding policy to use. Local traffic is sent directly to the destination with the link- layer protocol while global traffic is forwarded to a default gateway. In multi-hop networks the ad hoc routing protocol finds the route to a destination either proactively or on-demand. This thesis proposes and discusses a solution to deciding on the mobile host destination locality in a MANET.Godkänd; 2005; 20060916 (ysko)
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Brännström, Robert. "Network-layer mobility in wireless ad hoc access networks/". Luleå : Luleå tekniska universitet, 2005. http://epubl.ltu.se/1402-1757/2005/68/.
Testo completo
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Al-Hoqani, Noura Y. S. "In-network database query processing for wireless sensor networks". Thesis, Loughborough University, 2018. https://dspace.lboro.ac.uk/2134/36226.
Testo completoAbstract (sommario):
In the past research, smart sensor devices have become mature enough for large, distributed networks of such sensors to start to be deployed. Such networks can include tens or hundreds of independent nodes that can perform their functions without human interactions such as recharging of batteries, the configuration of network routes and others. Each of the sensors in the wireless sensor network is considered as microsystem, which consists of memory, processor, transducers and low bandwidth as well as a low range radio transceiver. This study investigates an adaptive sampling strategy for WSS aimed at reducing the number of data samples by sensing data only when a significant change in these processes is detected. This detection strategy is based on an extension to Holt's Method and statistical model. To investigate this strategy, the water consumption in a household is used as a case study. A query distribution approach is proposed, which is presented in detail in chapter 5. Our developed wireless sensor query engine is programmed on Sensinode testbed cc2430. The implemented model used on the wireless sensor platform and the architecture of the model is presented in chapters six, seven, and eight. This thesis presents a contribution by designing the experimental simulation setup and by developing the required database interface GUI sensing system, which enables the end user to send the inquiries to the sensor s network whenever needed, the On-Demand Query Sensing system ODQS is enhanced with a probabilistic model for the purpose of sensing only when the system is insufficient to answer the user queries. Moreover, a dynamic aggregation methodology is integrated so as to make the system more adaptive to query message costs. Dynamic on-demand approach for aggregated queries is implemented, based in a wireless sensor network by integrating the dynamic programming technique for the most optimal query decision, the optimality factor in our experiment is the query cost. In-network query processing of wireless sensor networks is discussed in detail in order to develop a more energy efficient approach to query processing. Initially, a survey of the research on existing WSN query processing approaches is presented. Building on this background, novel primary achievements includes an adaptive sampling mechanism and a dynamic query optimiser. These new approaches are extremely helpful when existing statistics are not sufficient to generate an optimal plan. There are two distinct aspects in query processing optimisation; query dynamic adaptive plans, which focus on improving the initial execution of a query, and dynamic adaptive statistics, which provide the best query execution plan to improve subsequent executions of the aggregation of on-demand queries requested by multiple end-users. In-network query processing is attractive to researchers developing user-friendly sensing systems. Since the sensors are a limited resource and battery powered devices, more robust features are recommended to limit the communication access to the sensor nodes in order to maximise the sensor lifetime. For this reason, a new architecture that combines a probability modelling technique with dynamic programming (DP) query processing to optimise the communication cost of queries is proposed. In this thesis, a dynamic technique to enhance the query engine for the interactive sensing system interface is developed. The probability technique is responsible for reducing communication costs for each query executed outside the wireless sensor networks. As remote sensors have limited resources and rely on battery power, control strategies should limit communication access to sensor nodes to maximise battery life. We propose an energy-efficient data acquisition system to extend the battery life of nodes in wireless sensor networks. The system considers a graph-based network structure, evaluates multiple query execution plans, and selects the best plan with the lowest cost obtained from an energy consumption model. Also, a genetic algorithm is used to analyse the performance of the approach. Experimental testing are provided to demonstrate the proposed on-demand sensing system capabilities to successfully predict the query answer injected by the on-demand sensing system end-user based-on a sensor network architecture and input query statement attributes and the query engine ability to determine the best and close to the optimal execution plan, given specific constraints of these query attributes . As a result of the above, the thesis contributes to the state-of-art in a network distributed wireless sensor network query design, implementation, analysis, evaluation, performance and optimisation.
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Qi, Bing Biaz Saad. "Routing metrics for multi-hop wireless MESH networks". Auburn, Ala., 2009. http://hdl.handle.net/10415/1705.
Testo completo
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Gaur, Amit. "Secured Communication in Wireless Sensor Network (WSN) and Authentic Associations in Wireless Mesh Networks". University of Cincinnati / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1282053086.
Testo completo
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Spinden, David, Jeffrey Jasper e Kurt Kosbar. "Comparison of Wireless Ad-Hoc Sensor Networks". International Foundation for Telemetering, 2004. http://hdl.handle.net/10150/605786.
Testo completoAbstract (sommario):
International Telemetering Conference Proceedings / October 18-21, 2004 / Town & Country Resort, San Diego, CaliforniaThere are a number of telemetry applications where it would be helpful to have networks of sensors that could autonomously discover their connectivity, and dynamically reconfigure themselves during use. A number of research groups have developed wireless ad-hoc sensor network systems. This paper reviews the state-of-the-art in wireless ad-hoc networks, examining the features, assumptions, limitations and unique attributes of some of the more popular solutions to this problem.
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Ould-Ahmed-Vall, ElMoustapha. "Algorithms for Self-Organizing Wireless Sensor Networks". Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/14473.
Testo completoAbstract (sommario):
The unique characteristics of sensor networks pose numerous challenges that have to be overcome to enable their efficient use. In particular, sensor networks are energy constrained because of their reliance on battery power. They can be composed of a large number of unreliable nodes. These characteristics render node collaboration essential to the accomplishment of the network task and justify the development of new algorithms to provide services such as routing, fault tolerance and naming.
This work increases the knowledge on the growing field of sensor network algorithms by contributing a new evaluation tool and two new algorithms.
A new sensor network simulator that can be used to evaluate sensor network algorithms is discussed. It incorporates models for the different functional units composing a sensor node and characterizes the energy consumption of each. It is designed in a modular and efficient way favoring the ease of use and extension. It allows the user to choose from different implementations of energy models, accuracy models and types of sensors.
The second contribution of this thesis is a distributed algorithm to solve the unique ID assignment problem in sensor networks. Our solution starts by assigning long unique IDs and organizing nodes in a tree structure. This tree structure is used to compute the size of the network. Then, unique IDs are assigned using the minimum length. Globally unique IDs are useful in providing many network functions, e.g. node maintenance and security. Theoretical and simulation analysis of the ID assignment algorithm demonstrate that a high percentage of nodes are assigned unique IDs at the termination of the algorithm when the algorithm parameters are set properly. Furthermore, the algorithm terminates in a short time that scales well with the network size.
The third contribution of this thesis is a general fault-tolerant event detection scheme that allows nodes to detect erroneous local decisions based on the local decisions reported by their neighbors. It can handle cases where nodes have different and dynamic accuracy levels. We prove analytically that the derived fault-tolerant estimator is optimal under the maximum a posteriori criterion. An equivalent weighted voting scheme is derived.
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Chen, Xiang. "Resource management in wireless networks". [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0011549.
Testo completo