This dissertation will present several novel techniques that use cooperation and diversity to improve the performance of multihop Wireless Sensor Networks, as measured by throughput, delay, and reliability, beyond what is achievable with conventional error control technology. We will investigate the applicability of these new technologies to Wireless Body Area Networks (WBANs) an important emerging class of wireless sensor networks. WBANs, which promise significant improvement in the reliability of monitoring and treating people's health, comprise a number of sensors and actuators that may either be implanted in vivo or mounted on the surface of the human body, and which are capable of wireless communication to one or more external nodes that are in close proximity to the human body. Our focus in this research is on enhancing the performance of WBANs, especially for emerging real-time in vivo traffic such as streaming real-time video during surgery. Because of the nature of this time-sensitive application, retransmissions may not be possible. Furthermore, achieving minimal energy consumption, with the required level of reliability is critical for the proper functioning of many wireless sensor and body area networks. Additionally, regardless of the traffic characteristics, the techniques we introduce strive to realize reliable wireless sensor networks using (occasionally) unreliable components (wireless sensor nodes). To improve the performance of wireless sensor networks, we introduce a novel technology Cooperative Network Coding, a technology that synergistically integrates the prior art of Network Coding with Cooperative Communications. With the additional goal of further minimizing the energy consumed by the network, another novel technology Cooperative Diversity Coding was introduced and is used to create protection packets at the source node. For representative applications, optimized Cooperative Diversity Coding or Cooperative Network Coding achieves ≥ 25% energy savings compared to the baseline Cooperative Network Coding scheme. Cooperative Diversity Coding requires lees computational complexity at the source node compared to Cooperative Network Coding. To improve the performance and increase the robustness and reliability of WBANs, two efficient feedforward error-control technologies, Cooperative Network Coding (CDC) and Temporal Diversity Coding (TDC), are proposed. Temporal Diversity Coding applies Diversity Coding in time to improve the WBAN's performance. By implementing this novel technique, it is possible to achieve significant improvement (50%) in throughput compared to extant WBANs. An example of an implementation of in vivo real-time application, where TDC can improve the communications performance, is the MARVEL (Miniature Anchored Robotic Videoscope for Expedited Laparoscopy) research platform developed at USF. The MARVEL research platform requires high bit rates (100 Mbps) for high-definition transmission. Orthogonal Frequency Division Multiplexing (OFDM), a widely used technology in fourth generation wireless networks (4G) that achieves high transmission rates over dispersive channels by transmitting serial information through multiple parallel carriers. Combining Diversity Coding with OFDM (DC-OFDM) promises high reliability communications while preserving high transmission rates. Most of the carriers transport original information while the remaining (few) carriers transport diversity coded (protection) information. The impact of DC-OFDM can extend far beyond in vivo video medical devices and other special purpose wireless systems and may find significant application in a broad range of ex vivo wireless systems, such as LTE, 802.11, 802.16.

Network coding refers to the implementation of coding methods to utilize network connections more efficiently. Network coding is commonly researched in the information theory field, but very little research is being done on the physical implementation thereof. One exception is COPE where network coding is implemented in wireless networks for unicast transmission sessions. In this dissertation, we discuss the physical arrangement of wireless nodes to form topologies suitable for the implementation of network coding. We implement linear network coding in wireless ad hoc networks for multicast transmission sessions. We calculate the areas in which each wireless node must be located for a specific network coding suitable topology to be formed. The identified topologies are simulated in OPNET Modeler and then implemented on a six node testbed, to analyse the effect of implementing network coding in these topologies. We provide results indicating the trade-off between reduced network load and higher end-to-end delay when our developed network coding algorithm is active in the respective topologies. The results indicate that the developed network coding scheme will produce better overall performance when implemented in sensor networks or highly congested ad hoc networks. / Thesis (M.Ing. (Computer and Electronical Engineering))--North-West University, Potchefstroom Campus, 2011.

Network coding refers to the implementation of coding methods to utilize network connections more efficiently. Network coding is commonly researched in the information theory field, but very little research is being done on the physical implementation thereof. One exception is COPE where network coding is implemented in wireless networks for unicast transmission sessions. In this dissertation, we discuss the physical arrangement of wireless nodes to form topologies suitable for the implementation of network coding. We implement linear network coding in wireless ad hoc networks for multicast transmission sessions. We calculate the areas in which each wireless node must be located for a specific network coding suitable topology to be formed. The identified topologies are simulated in OPNET Modeler and then implemented on a six node testbed, to analyse the effect of implementing network coding in these topologies. We provide results indicating the trade-off between reduced network load and higher end-to-end delay when our developed network coding algorithm is active in the respective topologies. The results indicate that the developed network coding scheme will produce better overall performance when implemented in sensor networks or highly congested ad hoc networks. / Thesis (M.Ing. (Computer and Electronical Engineering))--North-West University, Potchefstroom Campus, 2011.

Wireless sensor network plays a significant role in the design of future Smart Grid, mainly for the purpose of environment monitoring, data acquisition and remote control. Sensors deployed on the utility poles on the power transmission line are used to collect environment information and send them to the substations for analysis and management. However, the transmission is suffered from erasures and errors along the transmission channels. In this thesis, we consider a line network model proposed in [1] and [2]. We first analyze several different erasure codes in terms of overhead and encoding/decoding costs, followed by proposing two different coding schemes for our line network. To deal with both erasures and errors, we combine the erasure codes and the traditional error control codes, where an RS code is used as an outer codes in addition to the erasure codes. Furthermore, an adaptive RS coding scheme is proposed to improve the overall coding efficiency over all SNR regions. In the end, we apply network coding with error correction of network errors and erasures and examine our model from the mathematical perspective. / Graduate

This research investigates cross-layer design in multi-hop wireless networks with random access. Due to the complexity of the problem, we study cross-layer design with a simple slotted ALOHA medium access control (MAC) protocol without considering any network dynamics. Firstly, we study the optimal joint configuration of routing and MAC parameters in slotted ALOHA based wireless networks under a signal to interference plus noise ratio based physical interference model. We formulate a joint routing and MAC (JRM) optimization problem under a saturation assumption to determine the optimal max-min throughput of the flows and the optimal configuration of routing and MAC parameters. The JRM optimization problem is a complex non-convex problem. We solve it by an iterated optimal search (IOS) technique and validate our model via simulation. Via numerical and simulation results, we show that JRM design provides a significant throughput gain over a default configuration in a slotted ALOHA based wireless network. Next, we study the optimal joint configuration of routing, MAC, and network coding in wireless mesh networks using an XOR-like network coding without opportunistic listening. We reformulate the JRM optimization problem to include the simple network coding and obtain a more complex non-convex problem. Similar to the JRM problem, we solve it by the IOS technique and validate our model via simulation. Numerical and simulation results for different networks illustrate that (i) the jointly optimized configuration provides a remarkable throughput gain with respect to a default configuration in a slotted ALOHA system with network coding and (ii) the throughput gain obtained by the simple network coding is significant, especially at low transmission power, i.e., the gain obtained by jointly optimizing routing, MAC, and network coding is significant even when compared to an optimized network without network coding. We then show that, in a mesh network, a significant fraction of the throughput gain for network coding can be obtained by limiting network coding to nodes directly adjacent to the gateway. Next, we propose simple heuristics to configure slotted ALOHA based wireless networks without and with network coding. These heuristics are extensively evaluated via simulation and found to be very efficient. We also formulate problems to jointly configure not only the routing and MAC parameters but also the transmission rate parameters in multi-rate slotted ALOHA systems without and with network coding. We compare the performance of multi-rate and single rate systems via numerical results. We model the energy consumption in terms of slotted ALOHA system parameters. We found out that the energy consumption for various cross-layer systems, i.e., single rate and multi-rate slotted ALOHA systems without and with network coding, are very close.

Nous considérons les Réseaux Sociaux Mobiles Tolérant le Délai (DTMSN), constitués de nœuds sans-fil avec une connectivité intermittente, et groupés en communautés sociales. Cette thèse traite de l’analyse et de la conception de stratégies de transfert de l’information dans les DTMSN. Elle est principalement dédiée à l’étude de codage réseau inter-session (ISNC) dans ce but. Le codage réseau est une généralisation du routage et ISNC est connu comme un problème d’optimisation difficile en général, spécifiquement parce qu’il peut vite devenir nuisible si non conçu avec soin. Le premier chapitre répond théoriquement au problème d’optimisation du routage (sans ISNC) dans les DTMSN. Nous généralisons les résultants existants pour les topologies homogènes. Le deuxième chapitre conçoit et modélise un contrôle de ISNC par paire, qui englobe conjointement le contrôle du routage et du codage, avec une contrainte d’énergie. Pour s’attaquer de façon heuristique à l’optimisation de ce contrôle, le troisième chapitre présente une étude expérimentale visant à identifier quand ISNC est bénéfique ou nuisible, en fonction du nombre maximum de copies par paquet, de la charge du réseau, de la taille de buffer des nœuds relais et de la gestion de buffer. Le quatrième chapitre présente la conception de critères décentralisés de codage, pour déclencher en ligne le mélange de sessions si ISNC peut être bénéfique. Nous testons ces critères sur des topologies simples et sur des traces réelles, en expliquant les limites de notre approche. / We consider Delay Tolerant Mobile Social Networks (DTMSN), made of wireless nodes with intermittent connections and clustered into social communities. This thesis deals with the analysis and design of information transfer strategies in DTMSN. It is mostly dedicated to investigate the use of Inter-Session Network Coding (ISNC) towards this goal. Network coding is a generalization of routing and ISNC is known as a difficult optimization problem in general, specifically because it can easily get detrimental, compared to no coding, if not designed carefully. The first part of this thesis addresses theoretically the optimization problem of the (non-ISNC) routing policy in DTMSNs. We generalize the existing results for homogeneous topologies. The second part of the thesis designs and models a parameterized pairwise ISNC control policy that encompasses both routing and coding controls with an energy constraint. In order to tackle heuristically the optimization problem, the third chapter presents an experimental study of pairwise ISNC to investigate when it can be beneficial or detrimental. We examine the impact on ISNC performance of a number of parameters, such as the constraint on the maximum number of copies per packet, the network load, the buffer size of the relay nodes and the buffer management policies. The fourth chapter addresses the design of decentralized coding criteria allowing to trigger online session mixing if ISNC may be beneficial. We test these coding criteria on both toy topologies and real-world traces, pointing out and explaining the limits of our approach.

La popularité des plateformes mobiles telles que smartphones et tablettes génère un volume croissant de données à transférer. La principale raison de cette croissance est l'accès simplifié aux contenus vidéo sur ces plateformes. La future génération (5G) de téléphonie mobile est en cours de développement et a pour objectif d'offrir une bande passante suffisante pour de tels volumes de données. Néanmoins, un déploiement en masse de la 5G n'est pas envisagé avant 2020. De plus, la croissance est telle qu'il sera forcément intéressant de développer des solutions alternatives et complémentaires capables de délester le réseau cellulaire. L'exemple actuel le plus représentatif est le délestage de données cellulaires vers des réseaux d'accès WiFi par les principaux opérateurs mobiles. Dans ce contexte, nous proposons de déployer un nouveau réseau de contenus qui s'appuie sur les réseaux de transports publics urbains. Cette solution déploie des bornes sans-fil dans les bus et sur certaines stations de bus pour offrir du contenu aux passagers des bus. Les bus enregistrent et transportent les données, et se comportent donc comme des mules qui peuvent s'échanger des données dans certaines stations de bus. L'ensemble des bus créé un réseau de transport de données tolérantes au délai telles que de la vidéo à la demande. La création d'un tel réseau soulève de nombreuses questions. Les questions traitées dans les trois parties de cette thèse sont les suivantes: (i) le choix des stations de bus sur lesquelles une borne sans-fil doit être déployée, (ii) le choix du protocole de routage des données, (iii) la gestion efficace de la contention dans les stations et enfin (iv) la réduction du coût d'une telle infrastructure. La première partie de la thèse présente notre réseau de contenu dont l'objectif principal est de transporter de larges volumes de données. Nous montrons pour cela qu'il suffit de déployer des bornes sans-fil aux terminus des lignes de bus. Ce résultat provient de l'analyse des réseaux de transports publics des villes de Toulouse, Helsinki et Paris. Connaissant les horaires et la topologie de ces réseaux de transports, nous proposons de pré-calculer les routes pour transmettre les données dans ce réseau. Nous montrons que ce routage statique permet de réduire drastiquement le nombre de réplications de messages quand on le compare à un routage épidémique. La seconde contribution de cette thèse s'intéresse à l'échange des messages au niveau des bornes sans-fil déployées aux terminus des lignes de bus. En effet, les protocoles d'accès actuels partagent équitablement la bande passante entre les bus et le point d'accès. Dans notre cas, il en résulte une congestion importante que nous proposons de résoudre en introduisant un codage réseau XOR de proche en proche. Les flux qui se croisent sont alors combinés par la borne. Les bus transportent des paquets codés qui seront décodés au prochain saut par la borne suivante. Une analyse théorique de ce mode de communication montre que la probabilité de réception des messages peut-être augmentée au maximum de 50% et la surcharge diminuée au maximum de 50%. Pour les 3 villes européennes considérées, nous montrons par simulation que ce protocole permet d'augmenter de 35% à 48% le nombre de messages reçus. La dernière partie de cette thèse a pour objectif de réduire le coût de déploiement d'une telle architecture. Elle classifie les terminus des lignes de bus en trois ensembles qui sont équipés par des bornes sans fil de nature différentes. Les résultats de simulation montrent que pour les trois villes il est possible de garantir la connectivité de bout-en-bout tout en réduisant les coûts de déploiement d'un facteur 3. Cette architecture, dénommée 3-tier, transporte 30% plus de messages que le déploiement basique proposé en première partie. Nous montrons qu'il est possible de décharger un grand volume de données avec notre architecture. Par exemple, pour Paris, notre architecture permet de / Mobile data traffic is increasing at an exponential rate with the proliferation of mobile devices and easy access to large contents such as video. Traffic demand is expected to soar in the next 5 years and a new generation of mobile networks (5G) is currently being developed to address the looming bandwidth crunch. However, significant 5G deployments are not expected until 2020 or even beyond. As such, any solution that offloads cellular traffic to other available networks is of high interest, the main example being the successful offloading of cellular traffic onto WiFi. In this context, we propose to leverage public transportation networks (PTNs) created by regular bus lines in urban centers to create another offloading option for delay tolerant data such as video on demand. This PhD proposes a novel content delivery infrastructure where wireless access points (APs) are installed on both bus stops and buses. Buses act as data mules, creating a delay tolerant network capable of carrying content users can access while commuting using public transportation. Building such a network raises several core challenges such as: (i) selecting the bus stops on which it is best to install APs, (ii) efficiently routing the data, (iii) relieving congestion points in major hubs and (iv) minimizing the cost of the full architecture. These challenges are addressed in the three parts of this thesis. The first part of the thesis presents our content delivery infrastructure whose primary aim is to carry large volumes of data. We show that it is beneficial to install APs at the end stations of bus lines by analyzing the publicly available time tables of PTN providers of different cities. Knowing the underlying topology and schedule of PTNs, we propose to pre-calculate static routes between stations. This leads to a dramatic decrease in message replications and transfers compared to the state-of-the-art Epidemic delay tolerant protocol. Simulation results for three cities demonstrate that our routing policy increases by 4 to 8 times the number of delivered messages while reducing the overhead ratio. The second part of the thesis addresses the problem of relieving congestion at stations where several bus lines converge and have to exchange data through the AP. The solution proposed leverages XOR network coding where encoding and decoding are performed hop-by-hop for flows crossing at an AP. We conduct a theoretical analysis of the delivery probability and overhead ratio for a general setting. This analysis indicates that the maximum delivery probability is increased by 50% while the overhead ratio is reduced by 50%, if such network coding is applied. Simulations of this general setting corroborate these points, showing, in addition, that the average delay is reduced as well. Introducing our XOR network coding to our content delivery infrastructure using real bus timetables, we demonstrate a 35% - 48% improvement in the number of messages delivered. The third part of the thesis proposes a cost-effective architecture. It classifies PTN bus stops into three categories, each equipped with different types of wireless APs, allowing for a fine-grained cost control. Simulation results demonstrate the viability of our design choices. In particular, the 3-Tier architecture is shown to guarantee end-to-end connectivity and reduce the deployment cost by a factor of 3 while delivering 30% more packets than a baseline architecture. It can offload a large amount of mobile data, as for instance 4.7 terabytes within 12 hours in the Paris topology.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-05-30T14:18:27Z No. of bitstreams: 1 luamoloisefernandesdasilveira.pdf: 589211 bytes, checksum: e51494b1c23ff74fa1fc26264147a6a1 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-05-30T15:36:08Z (GMT) No. of bitstreams: 1 luamoloisefernandesdasilveira.pdf: 589211 bytes, checksum: e51494b1c23ff74fa1fc26264147a6a1 (MD5) / Made available in DSpace on 2017-05-30T15:36:08Z (GMT). No. of bitstreams: 1 luamoloisefernandesdasilveira.pdf: 589211 bytes, checksum: e51494b1c23ff74fa1fc26264147a6a1 (MD5) Previous issue date: 2016-08-19 / Recentemente, Power Line Communication (PLC) tem atraído o interesse de pesquisadores de todo mundo. Contudo, sistemas PLC enfrentam diversos desafios em termos da degradação da qualidade de comunicação de dados. Para superar tais problemas, propomos o CodePLC, um protocolo MAC para PLC que utiliza network coding. Utilizamos um nó intermediário para intermediar a comunicação, armazenar e repassar uma combinação linear de pacotes PLC. Avaliamos o desempenho do CodePLC através da simulação de uma topologia comum em um sistema PLC baseado no esquema Orthogonal Frequency Division Multiplexing whith Time Domain Multiple Access (TDMA-OFDM), sob uma ampla gama de cenários. Em suma, os resultados mostram que, para transmissões do tipo broadcast, o uso de network coding melhora desempenho geral do sistema PLC baseado no TDMA-ODFM. De fato, quando comparado a um sistema que utiliza uma camada MAC PLC multihop stop&wait tradicional, podemos observar um pico de aumento de 110% no valor de pico do goodput. Além disso, nosso protocolo reduz em até 71,4% a ocupação dos buffers da rede. Finalmente, CodePLC pode reduz a latência média em até quatro vezes. / Recently, power line communication (PLC) has attracted interest of worldwide researchers. However, PLC systems face several challenges which degrade data communication quality. To overcome such issues, we propose CodePLC, a network coding PLC MAC protocol. We use a single relay node to intermediate communication, storing and forwarding linear combinations of PLC data packets. We evaluate CodePLC performance through simulations of a common topology for a PLC system based in Orthogonal Frequency Division Multiplexing whith Time Domain Multiple Access (TDMA-OFDM) under a wide range of scenarios. In summary, our results show that in a broadcast like transmission, the use of network coding enhances overall system performance. In fact, when compared to a traditional PLC system using multihop stop&wait MAC layer protocol, we have observed an peak of 110% goodput increase. Moreover, our protocol reduces in 71,4% network occupancy buffers. Finally, CodePLC reduces mean latency by four times.

Existing VoD solutions often rely on unicast to distribute content, which leads to a higher load on the VoD server as more nodes become interested in the content. In such case, P2P is an alternative way of distributing content since it makes better use of available resources in the network. In this report, several P2P structures are evaluated from an operators point of view. We believe BitTorrent is the most adequate protocol for a P2P solution in IPTV environments. Two BitTorrent clients have been implemented on an IP-STB as proof of concept to find out whether P2P is suited for IPTV environments. Several tests were conducted to evaluate the performance of both clients and to see if they were able to reach a sufficient throughput on the IP-STB. Based upon the tests and the overall impressions, we are convinced that this particular P2P protocol is well suited for IPTV environments. Hopefully, a client developed from scratch for the IP-STB will offer even greater characteristics. Further, we have studied how to share recorded content among IP-STBs. Such a design would probably have many similarities to BitTorrent since a central node needs to keep track of content; the IP-STBs take care of the rest. The report also brings up whether BitTorrent is suitable for streaming. We believe that the necessary changes required to obtain such functionality will disrupt the strengths of BitTorrent. Some alternative solutions are presented where BitTorrent has been extended with additional modules, such as a server.

The promise of Internet of Things (IoT) and mass connectivity has brought many applications and along with them many new challenges to be solved. Recognizing sensor networks as one of the main applications of IoT, this dissertation focuses on solutions for IoT challenges in both single-hop and multi-hop communications. In single-hop communications, the new IEEE 802.11ah and its Group Synchronized Distribution Coordination Function (GS-DCF) is studied. GS-DCF categorized nodes in multiple groups to solve the channel contention issue of dense networks. An RSS-Based grouping strategy is proposed for the hidden terminal problem that can arise in infrastructure-based single hop communications. For multi-hop communications, Physical Layer Network Coding (PNC) is studied as a robust solution for multi-hop packet exchange in linear networks. Focusing on practical and implementation issues of PNC systems, different challenges have been addressed and a Software Defined Radio (SDR) PNC system based on USRP devices is proposed and implemented. Finally, extensive simulation and experimental results are presented to evaluate the performance of the proposed algorithms in comparison with currently used methods. / Graduate