Practical Network Coding for Multi-source Scenarios

Network coding (NC) and erasure coding (EC) share a common principle of encoding incoming data packets at network intermediate nodes so that destination nodes can reconstruct the original data packets using a sufficient number of encoded data packets collected at the destinations. While NC in general reduces the number of packets sent through the network, EC introduces redundancy into the packet streams to recover from lost packets. Many research papers in NC assume loss-free packet transmission, and to address this issue, end-to-end packet loss recovery through EC has been proposed. In this paper, we investigate hop-by-hop packet loss recovery through EC so as to avoid the accumulation of lost packets throughout the network using flow oriented EC. Specifically, we explore combined NC and EC at intermediate nodes in the networks to allow for improved packet loss recovery compared to end-to-end EC. Different implementations trading the packet processing complexity at the intermediate and destination nodes are considered. This paper first examines the effects of data loss in NC and then the improvements achievable with the proposed method are presented.

Network coding is a technology with great potentiality in improving wireless multi-hop network throughput. And some routings combined with network coding have been proposed for wireless multi-hop network. In the routings combined with network coding, network coding condition is used to find network coding opportunities, which is very important to the performance improving of routings combined with network coding. However, the network coding conditions defined by existing routings combined with network coding unilaterally focus on the growth of network coding opportunities, which results in the increasing of cost and delay in routing discovery. Moreover, the more flows participating network coding, the higher probability of decoding failure, which degrade the network coding gain. In this paper, low complexity network coding condition (LCNC) is proposed. LCNC only detects two-flows network coding opportunity, and ensures the destination make successful decoding. In addition, the actual network coding gain is designed through analysis of link quality. Network coding opportunity will be ignored in case the actual network coding gain is negative. Based on LCNC, a low complexity network coding aware routing (LNCR) is designed aiming wireless multi-hop network. Simulation results demonstrate that LNCR obtain a balance between network coding gain and routing discovery cost, and can obtain higher network throughput when the network load is high compared with the classical network coding aware routings.

In this paper we are interested in improving the performance of constructive network coding schemes for video transmission over packet lossy networks. A novel unequal packet loss protection scheme R2NC based on low-triangular global coding matrix with ladder-shaped partition will be presented, which combines redundant and random network coding for robust H.264/SVC video transmission. Firstly, the error-correcting capabilities of redundant network coding make our scheme resilient to loss. Secondly, the implementation of random network coding at the intermediate nodes with multiple input links can reduce the cost of network bandwidth, thus reducing the end to end delay for video transmission. Thirdly, the low-triangular global coding matrix with ladder-shaped partition is maintained throughout R2NC process to provide unequal erasure protection for H.264/SVC priority layers. The redundant network coding avoids the retransmission of lost packets and improves error correcting capabilities of lost packets. Based only on the knowledge of the loss rates on the output links, the source node and intermediate nodes can make decisions for redundant network coding and random network coding (i.e., how much redundancy to add at this node). However, the redundancy caused by redundant network coding makes the network load increases, in order to improve network throughput, we perform random network coding at the intermediate nodes. Our approach is grounded on the overall distortion of reconstructed video minimization by optimizing the amount of redundancy assigned to each layer. Experimental results are shown to demonstrate the significant improvement of H.264/SVC video reconstruction quality with R2NC over packet lossy networks.

The reliability of a probabilistic communication network is considered. A probabilistic communication network is a network in which each branch is given a probability that the specific branch can perform its purpose successfully. This probability is called the reliability of this branch. The idea of the overall reliability of the simultaneous communication among all (or part of) the stations of a given network is introduced, rather than the pairwise reliability between any two stations as was discussed in previous works along this line. The overall reliability of a communication network is defined as the probability that simultaneous communication can be secured among all the stations; two formulas are given to enumerate it in terms of the branch reliabilities. An approximation is developed to calculate the overall reliability through the incidence matrix of the network when all the branch reliabilities are very small. Also, a criterion to compare relative importance of the roles played by all the branches is established by defining a quantity load for each branch. Two efficient algorithms are derived to find a most reliable subnetwork with no redundant branches. In addition, an exhausting method is furnished for the case of seeking simultaneous communication among only part of the terminals of the network.

Connectivity, losses, and buffering are factors that directly affect the performance of network coding. These factors affect the ability of intermediate nodes to generate useful encodings; these are encodings that contribute in propagating and recovering data at receiver node(s). It has been shown that in particular scenarios network coding performance can be improved by simply increasing the generation size (k); however, this leads to increasing transmission overhead, encoding complexity and (more importantly) buffer sizes at intermediate nodes. In this paper, we propose a new network coding approach where we employ Multi-Generation Mixing (MGM). MGM eliminates the need to increasing buffer sizes while improving the performance of network coding. Under MGM, we define a mixing set of size m generations that can be network coded (mixed) together. Within each MGM mixing set, a new set of generation packets are mixed with previously transmitted (network coded) generations. This generalized approach provides a great deal of resilience against losses when compared with traditional generation-based network coding. Our analysis of the performance of MGM-based network coding demonstrates significant reduction in required overhead for a given recovery performance at the receivers. We also illustrate the performance of MGM using extensive simulations that provide a useful insight into the viability of MGM-based network coding.

In a classical network, data streams originating from a source and intended to a desired destination are routed through intermediate nodes before reaching their final destination. By contrast, Network Coding (NC) manipulates at an intermediate node those data streams by combining the data from the streams before forwarding it to the destination. This paper describes the advances of NC in wireless communication for IMT-Advanced and beyond. A short overview of NC in wireless communications is given first. Afterward, the application of NC to broadcasting is described. Thereafter, NC methods in uplink wireless communications, such as User Grouping (UG) and Relay Selection (RS) are described. Further, the advantage of non-binary over binary network NC is shown in a multi-user multi-relay scenario. Finally the performance of NC is analyzed. In particular, in the uplink Multiple Access Relay Channel (MARC) scenario, the joint UG and RS methods lift the system capacity by 70%. The non-binary NC improves the SNR up to 4 dB. Finally the efficient broadcast method yields up to 22% overhead reduction compared to ARQ.

Chapter 1 - An Introduction to Network Coding

Recently, Network coding has been proved to be the breakthrough in the research field of network and communication. It is an effective technique to increase network capacity and improve the robustness and reliability of networks. In this paper, there is application of network coding in wireless network. In order to improve the reliability and the throughput of wireless network, we do extensive research on network coding incorporated with the multicast communication in WLAN, the routing optimization in multi-hop network and the retransmission efficiency for wireless broadcast system, and focus on the protocol design and the theory for the performance analysis. On the basis of introduction on basic idea and method of network coding, we proposes a new physical layer network coding scheme for two-way relay channel model based on a belief propagation approach. Then we make performance analysis through numerical simulation.

Network coding is a promising technology to improve throughput and reliability. However, the benefit of network coding is restricted and affected by network topology, especially in peer-to-peer system. Precise topology awareness can be helpful to improve system performance of network coding in terms of throughput and reliability. In this paper, we propose an innovative scheme TANCF (Topology Awareness based on Network Coding with Feedback), to detect the path in hierarchical P2P network based on the feedback from the intermediate nodes and the receiver nodes of network coding system. It is a first attempt to use network coding with feedback to reveal the network connectivity and to construct the network topology. In the TANCF scheme, the path matrix of network can be obtained by the feedback from intermediate nodes and receiver nodes, which has a close relationship with the adjacency matrix of topology, so that it can be used to construct the network topology that lead to optimize the parameters of network coding. Through the matrix analysis and simulation experiment, it can be proved that TANCF scheme can obtain the path matrix correctly with a high probability.

Emerging wireless multicast applications simultaneously impose two requirements to the underlying communication networks: to provide sufficient bandwidth and to support a variety of quality-of-service (QoS) sensitivities. For the first requirement, network coding has been proposed recently as an effective way of improving bandwidth utilization. However, almost all previous works about network coding focus on the throughput gain without considering the QoS requirements. Optimal network code construction in wireless multicast under different QoS constraints remains as a significant challenge. In this research, we study the QoS-driven network coding problem. We use large deviation principle to establish the relationship among source rate, link condition, QoS requirement, and network code. Using this relationship, under given QoS requirements, we solve the optimal network code construction problem. The proposed network code supports maximal source rate without violating the QoS requirements. These results constitute the foundations for future designing and implementing network coding based wireless multicast protocols.

This paper considers the interplay between rate adaptation and inter-session network coding gains in wireless mesh or ad hoc networks. Inter-session network coding opportunities at relay nodes depend on packets being overheard by surrounding nodes ? The more packets nodes overhear, the more opportunities relays have to combine packets, resulting in a potential increase in network throughput. Thus, by adapting its transmission rate, a node can increase the range over which its packets are overheard, enabling additional opportunities for coding and increased overall throughput. This paper considers inter-session coding, restricted to a single relay (bottleneck) node, or star network topology. Even for such simple topologies the optimal joint rate adaptation and network coding policy is known to be NP-hard. Optimal rate vector selection is a combinatorial optimization problem, which is NP-hard, and finding optimal coding scheme turns out to be a clique partitioning problem which is also NP-hard. So, we provide heuristics to find a suboptimal rate vector and coding scheme. Additionally, we provide a linear programming formulation for network coding when only pairwise intersession coding is allowed. We evaluate the averaged throughput in two different scenarios, in which relays have different access opportunities, giving some intuition on the impact of rate adaptation in lightly and heavily loaded systems. The gains of joint rate adaptation and network coding are marginal when the relay has a higher access opportunity than other nodes, or when the MAC operates ideally it ranges from 9% to 19% as compared to a network without network coding and 4% over a network using regular network coding. While, when the relay has equal access opportunity as other source nodes, which is more typical of todays MAC protocols under heavy loads, the gain ranges from 40% to 62% as compared to the standard relaying case and is upto around 20% as compared to a network with regular pairwise network coding. This can further be increased to a gain of 40% to 120% by replacing pairwise coding with sub-optimal general network coding scheme.

Network coding is a promising enhancement of routing to improve network throughput and provide high reliability. It allows a node to generate output messages by encoding its received messages. Peer-to-peer networks are a perfect place to apply network coding due to two reasons: the topology of a peer-to-peer network is constructed arbitrarily, thus it is easy to tailor the topology to facilitate network coding; the nodes in a peer-to-peer network are end hosts which can perform more complex operations such as decoding and encoding than simply storing and forwarding messages. In this paper, we propose a scheme to apply network coding to peer-to-peer file sharing which employs a peer-to-peer network to distribute files resided in a web server or a file server. The scheme exploits a special type of network topology called combination network. It was proved that combination networks can achieve unbounded network coding gain measured by the ratio of network throughput with network coding to that without network coding. Our scheme encodes a file into multiple messages and divides peers into multiple groups with each group responsible for relaying one of the messages. The encoding scheme is designed to satisfy the property that any subset of the messages can be used to decode the original file as long as the size of the subset is sufficiently large. To meet this requirement, we first define a deterministic linear network coding scheme which satisfies the desired property, then we connect peers in the same group to flood the corresponding message, and connect peers in different groups to distribute messages for decoding. Moreover, the scheme can be readily extended to support link heterogeneity and topology awareness to further improve system performance in terms of throughput, reliability and link stress. Our simulation results show that the new scheme can achieve 15%–20% higher throughput than another peer-to-peer multicast system, Narada, which does not employ network coding. In addition, it achieves good reliability and robustness to link failure or churn.

With more and more multimedia applications on the Internet, such as IPTV, bandwidth becomes a vital bottleneck for the booming of large scale Internet based multimedia applications. Network coding is recently proposed to take advantage to use network bandwidth efficiently. In this paper, we focus on massive multimedia data, e.g. IPTV programs, transportation in peer-to-peer networks with network coding. By through study of networking coding, we pointed out that the prerequisites of bandwidth saving of network coding are: I) one information source with a number of concurrent receivers, or 2) information pieces cached at intermediate nodes. We further proof that network coding can not gain bandwidth saving at immediate connections to a receiver end; As a result, we propose a novel model for IPTV data transportation in unstructured peer-to-peer networks with network coding. Our preliminary simulations show that the proposed architecture works very well.

We propose a network information flow strategy of optimal multicast with erasure correction coding (OMEC), in which erasure correction is a means of utilizing diversities rather than combating packet losses. An information source is first encoded by an erasure correction code and then optimally multicast by a server to sinks. The OMEC scheme has the following characteristics: (1) It is at least as good as optimal routing and, for some cases, can realize a network throughput arbitrarily larger than that achievable by pure routing. (2) For most scenarios, the approach yields a throughput comparable with the optimal throughput achievable with network coding. In fact, for most examples in the literature for which network coding makes high throughput gains compared to pure routing, OMEC performs close to the optimal. (3) Unlike general network coding, intermediate nodes are only required to route information. This makes OMEC compatible with currently deployed network structures. (4) Surprisingly, unlike pure optimal routing, OMEC can be efficiently computed in polynomial time. While OMEC is, in general, suboptimal compared to full fledged network coding, it enjoys most of the computational and throughput benefits associated with network coding over pure routing, without requiring any changes to existing hardware infrastructures or protocol stacks

Network coding (NC) is a promising technique recently proposed to improve network performance in terms of maximum throughput, minimum delivery delay, and energy consumption. The original proposal highlighted the advantages of NC for multicast communications in wire-line networks. Recently, network coding has been considered as an efficient approach to improve performance in wireless networks, mainly in terms of data reliability and lower energy consumption, especially for broadcast communications. The basic idea of NC is to remove the typical requirement that different information flows have to be processed and transmitted independently through the network. When NC is applied, intermediate nodes in the network do not simply relay the received packets, but they combine several received packets before transmission. As a consequence, the output flow at a given node is obtained as a linear combination of its input flows. This chapter deals with the application of network coding principle at different communications layers of the protocol stack, specifically, the Medium Access Control (MAC) and physical (PHY) Layers for wireless communication networks.