Two-Transmitter Two-Receiver Cooperative MAC Protocol: Cross-Layer Design and Performance Analysis

Cooperative diversity is a promising and practical technique for realizing spatial diversity through a virtual antenna array formed by multiple distributed antennas of different nodes. In this paper, we propose and evaluate a novel cooperative cross-layer medium access control (CC-MAC) protocol, which combines space-time coding and adaptive modulation at the physical layer and employs truncated automatic repeat request (ARQ) at the data-link layer. The transmitter's partner is selected in the previous hop, and the receiver invites a partner to participate in data reception in the current hop, and in this situation, a two-transmitter two-receiver model is constructed. Because distributed space-time coding is applied at the transmitting set (transmitter and its partner), cooperative diversity and coding gain can be obtained. Based on the instantaneous channel state measured at the receiver, an adaptive modulation scheme is adopted to improve the link throughput at the physical layer. In addition, the truncated ARQ scheme is employed to further enhance the throughput performance at the data-link layer. Furthermore, under different system models with or without the truncated ARQ scheme, performances of the average packet error rate (PER) and symbol error rate (SER) with multiple phase shift keying (M-PSK) modulation and multiple quadrature amplitude modulation (M-QAM) over Rayleigh fading channel are analyzed. Simulation results verify the correctness of the performance analysis and show that CC-MAC can significantly improve system throughput and energy efficiency compared with other transmission schemes.