Bridging inter-flow and intra-flow Network Coding for video applications: Testbed description and performance evaluation

Abstract

Network Coding (NC) for Wireless Mesh Network (WMN) has received a lot of attention from the research community in recent years due to its ability to provide higher throughput, reliability, and efficiency in the use of the available wireless spectrum. NC has had two main research lines focused on inter-flow and intra-flow coding. However, these two domains have historically been studied separately. This paper proposes a testbed implementation of CORE, the first protocol to bridge both approaches such that the structure of intra-flow coding can be exploited during inter-flow coding to both enhance reliability, common of the former, while maintaining an efficient spectrum usage, typical of the latter. This paper uses the intuition provided in [1] to propose a practical implementation of the protocol leveraging Random Linear Network Coding (RLNC) for intra-flow coding, a credit based packet transmission approach to decide how much and when to send redundancy in the network, and a minimalistic feedback mechanism to guarantee delivery of generations of the different flows. Given the delay constraints of video applications, we proposed a simple yet effective coding mechanism, Block Coding On The Fly (BCFly), that allows a block encoder to be fed on-the-fly, thus reducing the delay to accumulate enough packets that is introduced by typical generation based NC techniques. Our measurements and comparison to forwarding and COPE show that CORE not only outperforms these schemes even for small packet losses, but that the gains can be of five fold and two orders of magnitude, respectively, for higher packet losses.