Effect of realistic channel conditions on the energy efficiency of network coding-aided cooperative MAC protocols

The emergence of heterogeneous networks (HetNets) as an enabling paradigm for ubiquitous wireless communication has further reinforced the concept of medium range cooperation among the end users. This trend, along with the need for bidirectional communication, has triggered the design of new Network Coding (NC)- aided Medium Access Control (MAC) protocols that benefit both the throughput and the energy efficiency in the system. However, the vast majority of MAC protocols are usually designed and analyzed under simplified channel models, ignoring the severe effect of realistic physical (PHY) layer conditions on the wireless communication. In this article, we focus on the impact of correlated long-term slow fading (shadowing) on the performance of distributed wireless systems. As a case study, we discuss in detail the performance of a cooperative NC-aided Automatic Repeat reQuest (ARQ) MAC protocol under correlated shadowing conditions. Our results reveal interesting trade-offs between throughput and energy efficiency, highlighting the importance of considering the slow fading effect in the design of cooperative MAC protocols.