Cross-Layer Theoretical Analysis of NC-aided Cooperative ARQ Protocols in Correlated Shadowed Environments

In this paper, we propose a cross-layer analytical model for the study of network coding (NC)-based Automatic Repeat reQuest (ARQ) medium access control (MAC) protocols in correlated slow-faded (shadowed) environments, where two end nodes are assisted by a cluster of relays to exchange data packets. The goal of our work is threefold: 1) to provide general physical-layer theoretical expressions for estimating crucial network parameters (i.e., network outage probability and expected size of the active relay set), applicable in two-way communications; 2) to demonstrate how these expressions are incorporated into theoretical models of the upper layers (i.e., MAC); and 3) to study the performance of a recently proposed NC-aided cooperative ARQ (NCCARQ) MAC protocol under correlated shadowing conditions. Extensive Monte Carlo experiments have been carried out to validate the efficiency of the developed analytical model and to investigate the realistic performance of NCCARQ. Our results indicate that the number of active relays is independent of the shadowing correlation in the wireless links and reveal intriguing tradeoffs between throughput and energy efficiency, highlighting the importance of cross-layer approaches for the assessment of cooperative MAC protocols

Effect of Realistic Channel Conditions on the Energy Efficiency of Network Coding-aided Cooperative MAC Protocols

International audienceThe 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