Network Coding in Uplink Cellular Systems

Abstract: Ever since its introduction, network coding has attracted a lot of interest from the research community. This interest is a result of two main factors: the simplicity of application of network coding and the possibility to apply it to a plethora of applications. Research in network coding started on wired networks for different types of traffic, mainly focusing on code design, content distribution and network security. However, researchers soon came to realize that the inherent properties of the wireless medium render it a fertile ground for the application of network coding. This has resulted in tremendous research efforts on wireless applications of network coding for wireless systems, both academically and industrially, with the majority of these works targeting bidirectional traffic scenarios. In this work, we focus on practical implementation issues for network coding when applied to uplink cellular traffic. We provide our own relaying scheme based on decode-and-forward relays and network coding with a specially designed method of decoding at the receiver. We complement this method with user grouping, relay selection diversity and time division among the transmitting nodes in order to achieve the gains promised by network coding in terms of throughput increase, while halving the power usage at the relay nodes. We show that these complements are necessary in order to translate the decrease in the number of transmissions offered by network coding into capacity gains; otherwise, random application of network coding would provide a worse performance compared to direct transmission or decode-and-forward relaying.