Network-coded cooperative communications (NC-CC) refers to the use of network coding (NC) in cooperative communications (CC). Prior studies have shown that NC has the potential to improve the performance of CC when there are multiple sessions in the wireless network. These studies were done for the case when multiple sessions are sharing a single relay node. However, how NC-CC behaves when multiple relay nodes are employed remains an open problem. In this paper, we explore this problem by analyzing the achievable rate of each session in this setting. We develop closed form formulas for the mutual information and the achievable data rate for each session. We show that prior results for a single relay is a special case of our result. Based on these findings, we then study a network optimization problem that requires joint optimization of session grouping, relay node grouping, and matching of session/relay groups. We show that this problem is NP-hard, and present a polynomial time heuristic algorithm to solve this problem. Using simulation results, we show this algorithm is highly competitive and can produce results that are near to optimality.
['Sushant Sharma', 'Yi Shi', 'Y. Thomas Hou', 'Sastry Kompella', 'Scott F. Midkiff']
Network-coded cooperative communications with multiple relay nodes: Achievable rate and network optimization