Cross-layer design of multi-hop wireless networks

MULTI -hop wireless networks are usually defined as a collection of nodes equipped with radio transmitters, which not only have the capability to communicate each other in a multi-hop fashion, but also to route each others’ data packets. The distributed nature of such networks makes them suitable for a variety of applications where there are no assumed reliable central entities, or controllers, and may significantly improve the scalability issues of conventional single-hop wireless networks. This Ph.D. dissertation mainly investigates two aspects of the research issues related to the efficient multi-hop wireless networks design, namely: (a) network protocols and (b) network management, both in cross-layer design paradigms to ensure the notion of service quality, such as quality of service (QoS) in wireless mesh networks (WMNs) for backhaul applications and quality of information (QoI) in wireless sensor networks (WSNs) for sensing tasks. Throughout the presentation of this Ph.D. dissertation, different network settings are used as illustrative examples, however the proposed algorithms, methodologies, protocols, and models are not restricted in the considered networks, but rather have wide applicability. First, this dissertation proposes a cross-layer design framework integrating a distributed proportional-fair scheduler and a QoS routing algorithm, while using WMNs as an illustrative example. The proposed approach has significant performance gain compared with other network protocols. Second, this dissertation proposes a generic admission control methodology for any packet network, wired and wireless, by modeling the network as a black box, and using a generic mathematical 0. Abstract 3 function and Taylor expansion to capture the admission impact. Third, this dissertation further enhances the previous designs by proposing a negotiation process, to bridge the applications’ service quality demands and the resource management, while using WSNs as an illustrative example. This approach allows the negotiation among different service classes and WSN resource allocations to reach the optimal operational status. Finally, the guarantees of the service quality are extended to the environment of multiple, disconnected, mobile subnetworks, where the question of how to maintain communications using dynamically controlled, unmanned data ferries is investigated

Cascading Tournament Algorithm: Low Power, High Capacity Medium Sharing for Wireless Sensor Networks

Existing Medium Access Control protocols for Wireless Sensor Networks reduce the radio activity to improve network lifetime, at the expense of a reduced network capacity. Those protocols are ill-suited for energy constrained sensor networks that must support spatially and temporally heterogeneous traffic loads. This paper proposes a novel multi-ressource allocation algorithm and describes its implementation as a medium access control protocol for Wireless Sensor Networks. The algorithm, named Cascading Tournament (CT), is a localized, dynamic, joint contention/allocation algorithm. It relies on cascading iterations of tournaments to allocate a multiplicity of ressources to a multiplicity of winners. CT-MAC is an implementation of CT as a medium access protocol. By allocating multiple logicals channels allocation at each competition, CT-MAC improves the network capacity at a given duty-cycle or decreases the energy expenditure of the MAC layer at a given network capacity. Extensive simulations highlight the benefits of CT-MAC in both single-hop and multiple-hop scenarios through the computation of relevant performance metrics: power consumption, network capacity, delay and retransmissions. CT-MAC offers an unprecedented trade-off between network capacity, energy efficiency and delay and stands out as a solid candidate for energy constrained sensor networks that must support heterogeneous traffic loads. Our simulations show that CT-MAC significantly outperforms the state-of-the-art SCP-MAC protocol.Les protocoles d'accès au medium radio existants pour réseaux de capteurs sans-fil réduisent l'activité de la radio afin d'améliorer la durée de vie du réseau, et ce, au prix d'une diminution de la capacité du réseau. Ces protocoles sont peu adaptés pour les réseaux de capteurs contraints en énergie qui doivent supporter des trafics spatialement et temporellement hétérogènes. Ce rapport propose un algorithme d'allocation multi-ressources et décrit son implémentation sous forme de protocole de contrôle d'accès (MAC) au canal radio pour réseaux de capteurs. L'algorithme, appelé Cascading Tour- nament (CT), est un algorithme combiné de gestion de la contention/allocation localisé, dynamique et localisé. Il se repose sur des itérations de tournois en cascade pour allouer une pluralité de ressources à une pluralité de vainqueurs. CT-MAC est une implémentation de CT en tant que protocole MAC. En al- louant plusieurs canaux logiques à chaque compétition, CT-MAC améliore la capacité du réseau pour un cycle d'endormissement donné ou diminue la con- sommation énergétique de la couche MAC pour une capacité du réseau donnée. Une étude complète par simulation montre l'intérêt de CT-MAC dans des scé- narios de voisinage unique et multi-sauts. Ces simulations ont permis le calcul de métriques de performances pertinentes: consommation énergétique, capacité du réseau, délai et retransmissions. CT-MAC offre un compromis entre capacité du réseau et efficacité énergétique qui n'a pas de précédent. Il se présente donc comme un candidat sérieux pour les réseaux de capteurs contraints en énergie qui doivent supporter des trafics hétérogènes. Nos simulations ont montré que CT-MAC surpasse le protocole de l'état de l'art SCP-MAC

Transmission scheduling for wireless mesh networks with temporal reuse

Link-assigned transmission schedules with timeslot reuse by multiple links in both the space and time domains are investigated in this study for stationary multihop wireless mesh networks with both rate and power adaptivity. Specifically, cross-layer optimised schedules with proportionally fair end-to-end flow rates and network coding capability are constructed for networks operating under the physical interference model with single-path minimum hop routing. Extending transmission rights in a link-assigned schedule allows for network coding and temporal reuse, which increases timeslot usage efficiency when a scheduled link experiences packet depletion. The schedules that suffer from packet depletion are characterised, and a generic temporal reuse-aware achievable rate region is derived. Extensive computational experiments show improved schedule capacity, quality of service, power efficiency and benefit from network coding accrued with schedules optimised in the proposed temporal reuseaware convex rate region.http://jwcn.eurasipjournals.com/content/2011/1/8

A congestion control scheme for wireless sensor networks

In wireless sensor networks (WSN), nodes have very limited power due to hardware constraints. Packet losses and retransmissions resulting from congestion cost precious energy and shorten the lifetime of sensor nodes. This problem motivates the need for congestion control mechanisms in WSN. In this thesis, an observation of multiple non-empty queues in sensor networks is first reported. Other aspects affected by congestion like queue length, delay and packet loss are also studied. The simulation results show that the number of occupied queues along a path can be used to detect congestion. Based on the above result, a congestion control scheme for the transport layer is proposed in this thesis. It is composed of three parts: (i) congestion detection by tracking the number of non-empty queues; (ii) On-demand midway non-binary explicit congestion notification (CN) feedback; and (iii) Adaptive rate control based on additive increase and multiplicative decrease (AIMD). This scheme has been implemented in ns2. Extensive simulations have been conducted to evaluate it. Results show that it works well in mitigating and avoiding congestion and achieves good performance in terms of energy dissipation, latency and transmission effciency

Distributed Trust Management in Autonomic Networks

The management of autonomic networks has gained more and more attentions because of their wide applications and control difficulties. Autonomic networks are decentralized and self-organized. Without global knowledge on the states of autonomic networks, it is difficult to predict behaviors of such networks and thus to conduct proper network management and control. This dissertation is the starting point of my effort to theoretically understand the complex characteristics of autonomic networks. In particular, I focus on a specific application: distributed trust management. We view trust among users as a set of relations established on the basis of trust credentials and required by specified policies. Two important components of a distributed trust management system are studied in this work: trust credential distribution and trust evaluation. In autonomic networks, trust credentials are distributed throughout the network. Given the mobility and dynamics of the networks, it is important to properly distribute trust credentials such that users are able to efficiently obtain required credentials and update existing credentials. I present a trust credential distribution scheme based on network coding. After obtaining credentials in need, policies are required for users to evaluate trustworthiness of targets in a distributed way. In this dissertation, I model distributed trust evaluation as an estimation problem and trust evaluation policies based on local interactions are studied. I investigate the convergence of both deterministic and stochastic voting rules and prove their effectiveness with the present of misbehaving users. Autonomic networks rely on collaboration among users. The conflict between the benefit from collaboration and the required cost for collaboration naturally leads to game-theoretic studies. I study collaboration based on cooperative games with communication constraints and give the conditions under which users are willing to collaborate. The results in this dissertation show that a well-designed trust management system is helpful to enforce collaboration. Besides collaboration, I show that trust can be used to the utility optimization problems as well. The effect of trust values is that in the routing and scheduling problems the trustworthiness of the node will be automatically considered and used. For example, packets will not be routed frequently to suspicious nodes

Service quality assurance for the IPTV networks

The objective of the proposed research is to design and evaluate end-to-end solutions to support the Quality of Experience (QoE) for the Internet Protocol Television (IPTV) service. IPTV is a system that integrates voice, video, and data delivery into a single Internet Protocol (IP) framework to enable interactive broadcasting services at the subscribers. It promises significant advantages for both service providers and subscribers. For instance, unlike conventional broadcasting systems, IPTV broadcasts will not be restricted by the limited number of channels in the broadcast/radio spectrum. Furthermore, IPTV will provide its subscribers with the opportunity to access and interact with a wide variety of high-quality on-demand video content over the Internet. However, these advantages come at the expense of stricter quality of service (QoS) requirements than traditional Internet applications. Since IPTV is considered as a real-time broadcast service over the Internet, the success of the IPTV service depends on the QoE perceived by the end-users. The characteristics of the video traffic as well as the high-quality requirements of the IPTV broadcast impose strict requirements on transmission delay. IPTV framework has to provide mechanisms to satisfy the stringent delay, jitter, and packet loss requirements of the IPTV service over lossy transmission channels with varying characteristics. The proposed research focuses on error recovery and channel change latency problems in IPTV networks. Our specific aim is to develop a content delivery framework that integrates content features, IPTV application requirements, and network characteristics in such a way that the network resource utilization can be optimized for the given constraints on the user perceived service quality. To achieve the desired QoE levels, the proposed research focuses on the design of resource optimal server-based and peer-assisted delivery techniques. First, by analyzing the tradeoffs on the use of proactive and reactive repair techniques, a solution that optimizes the error recovery overhead is proposed. Further analysis on the proposed solution is performed by also focusing on the use of multicast error recovery techniques. By investigating the tradeoffs on the use of network-assisted and client-based channel change solutions, distributed content delivery frameworks are proposed to optimize the error recovery performance. Next, bandwidth and latency tradeoffs associated with the use of concurrent delivery streams to support the IPTV channel change are analyzed, and the results are used to develop a resource-optimal channel change framework that greatly improves the latency performance in the network. For both problems studied in this research, scalability concerns for the IPTV service are addressed by properly integrating peer-based delivery techniques into server-based solutions.Ph.D