Wireless Inter-Session Network Coding - An Approach Using Virtual Multicasts

Abstract

Abstract-This paper addresses the problem of inter-session network coding to maximize throughput for multiple communication sessions in wireless networks. We introduce virtual multicast connections which can extract packets from original sessions and code them together. Random linear network codes can be used for these virtual multicasts. The problem can be stated as a flowbased convex optimization problem with side constraints. The proposed formulation provides a rate region which is at least as large as the region without inter-session network coding. We show the benefits of our technique for several scenarios by means of simulation. The optimal solution for inter-session network coding might require nonlinear encoding functions [6] and even deciding a linear inter-session coding problem can be NP-complete [7]. Nonetheless, suboptimal linear coding schemes have been proposed both for wireline and wireless networks. Previous work on inter-session coding for wireline networks has focused on a graph-theoretic characterization of network codes [8], [9]. For example, in [10], the authors present an approach to translate the solution for the well-known butterfly network to larger networks. In [11] inter-session network coding is combined with multiple description coding. Recent work [12] presented an interference alignment approach to perform intersession coding. I. INTRODUCTIONWe focus on wireless networks, where the most prominent technique is the COPE protocol [13] which exploits the broadcast nature of the wireless medium. As shown in Fig. 1a, the number of transmissions can be reduced compared to routing if packets from different sessions are combined. This technique is called reverse carpooling in [14] due to the fact that the combined information has to travel in opposite directions. The interplay of the COPE protocol with medium access has been analyzed in [15] and approaches to model its performance were proposed in [16], [17]. COPE has been successfully implemented and shows gains especially when the reverse carpooling situation occurs.

Minimum-Energy Wireless Real-Time Multicast by Joint Network Coding and Scheduling Optimization

“…Since the parameter , the initial values, and the step size have significant impacts on performance of the proposed algorithm, how to set the most suitable parameters and update them online needs more research. Finally, we would like to point out that recent studies have shown that intersession NC can achieve better throughput performance than intrasession NC [19,20]. Therefore, how to integrate intersession NC into the optimization framework is another worthy research direction in the future.…”

Distributed Rate Allocation in <newline/>Inter-Session Network Coding

“…It has been shown that linear network coding is not sufficient for achieving the capacity bound [8]; however, significant throughput gains can still be obtained with linear inter-session network coding as shown in [9], which describes an implementation of opportunistic network coding for multiple unicast flows over wireless networks. Recently, several inter-session network coding algorithms have been proposed, mainly for data delivery in wireless networks [10], [11], [12], [13], [14]. Some of the works extend the COPE architecture [9] by considering application-specific features when designing the network codes.…”

“…The key idea is to regard packets as members of flows and not as independent entities as in [9], [10], [12]. A different approach for finding the feasible rate region is built on virtual multicasts [14]. The flow-based problem formulation stated in [14] provides a rate region which is at least as large as the rate region that can be achieved without inter-session network coding.…”

R 2 NC: robust inter‐session network coding in lossy wireless networks

“…The theoretical analysis and practical experiments have proved that NC can provide the performance improvements in throughput and energy efficiency [2, 3]. Since then, significant research on network coding has been done [4–6]. It's generally considered that NC can be classified into two categories, inter‐session NC (IRNC) and intra‐session NC (IANC) [7, 8], based on the structure of transmission sessions.…”