Dynamic algorithms for multicast with intra-session network coding

The problem of multiple multicast sessions with intra-session network coding in time-varying networks is considered. The network-layer capacity region of input rates that can be stably supported is established. Dynamic algorithms for multicast routing, network coding, power allocation, session scheduling, and rate allocation across correlated sources, which achieve stability for rates within the capacity region, are presented. This work builds on the back-pressure approach introduced by Tassiulas et al., extending it to network coding and correlated sources. In the proposed algorithms, decisions on routing, network coding, and scheduling between different sessions at a node are made locally at each node based on virtual queues for different sinks. For correlated sources, the sinks locally determine and control transmission rates across the sources. The proposed approach yields a completely distributed algorithm for wired networks. In the wireless case, power control among different transmitters is centralized while routing, network coding, and scheduling between different sessions at a given node are distributed

Performance Modelling and Optimisation of Multi-hop Networks

A major challenge in the design of large-scale networks is to predict and optimise the total time and energy consumption required to deliver a packet from a source node to a destination node. Examples of such complex networks include wireless ad hoc and sensor networks which need to deal with the effects of node mobility, routing inaccuracies, higher packet loss rates, limited or time-varying effective bandwidth, energy constraints, and the computational limitations of the nodes. They also include more reliable communication environments, such as wired networks, that are susceptible to random failures, security threats and malicious behaviours which compromise their quality of service (QoS) guarantees. In such networks, packets traverse a number of hops that cannot be determined in advance and encounter non-homogeneous network conditions that have been largely ignored in the literature. This thesis examines analytical properties of packet travel in large networks and investigates the implications of some packet coding techniques on both QoS and resource utilisation. Specifically, we use a mixed jump and diffusion model to represent packet traversal through large networks. The model accounts for network non-homogeneity regarding routing and the loss rate that a packet experiences as it passes successive segments of a source to destination route. A mixed analytical-numerical method is developed to compute the average packet travel time and the energy it consumes. The model is able to capture the effects of increased loss rate in areas remote from the source and destination, variable rate of advancement towards destination over the route, as well as of defending against malicious packets within a certain distance from the destination. We then consider sending multiple coded packets that follow independent paths to the destination node so as to mitigate the effects of losses and routing inaccuracies. We study a homogeneous medium and obtain the time-dependent properties of the packet’s travel process, allowing us to compare the merits and limitations of coding, both in terms of delivery times and energy efficiency. Finally, we propose models that can assist in the analysis and optimisation of the performance of inter-flow network coding (NC). We analyse two queueing models for a router that carries out NC, in addition to its standard packet routing function. The approach is extended to the study of multiple hops, which leads to an optimisation problem that characterises the optimal time that packets should be held back in a router, waiting for coding opportunities to arise, so that the total packet end-to-end delay is minimised

Distributed minimum cost multicasting with lossless source coding and network coding

In this paper, we consider minimum cost lossless source coding for multiple multicast sessions. Each session comprises a set of correlated sources whose information is demanded by a set of sink nodes. We propose a distributed end-to-end algorithm which operates over given multicast trees, and a back-pressure algorithm which optimizes routing and coding over the whole network. Unlike other existing algorithms, the source rates need not be centrally coordinated; the sinks control transmission rates across the sources. With random network coding, the proposed approach yields completely distributed and optimal algorithms for intra-session network coding. We prove the convergence of our proposed algorithms. Some practical considerations are also discussed. Experimental results are provided to complement our theoretical analysis

Opportunistic routing and network coding in multi-hop wireless mesh networks

The rapid advancements in communication and networking technologies boost the capacity of wireless networks. Multi-hop wireless networks are extremely exciting and rapidly developing areas and have been receiving an increasing amount of attention by researchers. Due to the limited transmission range of the nodes, end-to-end nodes may situate beyond direct radio transmission ranges. Intermediate nodes are required to forward data in order to enable the communication between nodes that are far apart. Routing in such networks is a critical issue. Opportunistic routing has been proposed to increase the network performance by utilizing the broadcast nature of wireless media. Unlike traditional routing, the forwarder in opportunistic routing broadcasts date packets before the selection of the next hop. Therefore, opportunistic routing can consider multiple downstream nodes as potential candidate nodes to forward data packets instead of using a dedicated next hop. Instead of simply forwarding received packets, network coding allows intermediate nodes to combine all received packets into one or more coded packets. It can further improve network throughput by increasing the transmission robustness and efficiency. In this dissertation, we will study the fundamental components, related issues and associated challenges about opportunistic routing and network coding in multi-hop wireless networks. Firstly, we focus on the performance analysis of opportunistic routing by the Discrete Time Markov Chain (DTMC). Our study demonstrates how to map packet transmissions in the network with state transitions in a Markov chain. We will consider pipelined data transfer and evaluate opportunistic routing in different wireless networks in terms of expected number of transmissions and time slots. Secondly, we will propose a regional forwarding schedule to optimize the coordination of opportunistic routing. In our coordination algorithm, the forwarding schedule is limited to the range of the transmitting node rather than among the entire set of forwarders. With such an algorithm, our proposal can increase the throughput by deeper pipelined transmissions. Thirdly, we will propose a mechanism to support TCP with opportunistic routing and network coding, which are rarely incorporated with TCP because the frequent occurrences of out-of-order arrivals in opportunistic routing and long decoding delay in network coding overpower TCP congestion control. Our solution completes the control feedback loop of TCP by creating a bridge between the sender and the receiver. The simulation result shows that our protocol significantly outperforms TCP/IP in terms of network throughput in different topologies of wireless networks

Mobile Ad-Hoc Networks

Being infrastructure-less and without central administration control, wireless ad-hoc networking is playing a more and more important role in extending the coverage of traditional wireless infrastructure (cellular networks, wireless LAN, etc). This book includes state-of-the-art techniques and solutions for wireless ad-hoc networks. It focuses on the following topics in ad-hoc networks: quality-of-service and video communication, routing protocol and cross-layer design. A few interesting problems about security and delay-tolerant networks are also discussed. This book is targeted to provide network engineers and researchers with design guidelines for large scale wireless ad hoc networks

Network coding meets multimedia: a review

While every network node only relays messages in a traditional communication system, the recent network coding (NC) paradigm proposes to implement simple in-network processing with packet combinations in the nodes. NC extends the concept of "encoding" a message beyond source coding (for compression) and channel coding (for protection against errors and losses). It has been shown to increase network throughput compared to traditional networks implementation, to reduce delay and to provide robustness to transmission errors and network dynamics. These features are so appealing for multimedia applications that they have spurred a large research effort towards the development of multimedia-specific NC techniques. This paper reviews the recent work in NC for multimedia applications and focuses on the techniques that fill the gap between NC theory and practical applications. It outlines the benefits of NC and presents the open challenges in this area. The paper initially focuses on multimedia-specific aspects of network coding, in particular delay, in-network error control, and mediaspecific error control. These aspects permit to handle varying network conditions as well as client heterogeneity, which are critical to the design and deployment of multimedia systems. After introducing these general concepts, the paper reviews in detail two applications that lend themselves naturally to NC via the cooperation and broadcast models, namely peer-to-peer multimedia streaming and wireless networkin