An Empty-Queue Aware Cooperative Relay MAC Protocol with Vacation Queue Analysis

In this paper, by exploring the idle state of the cooperative relay terminal, an empty-queue aware cooperative time division multiple access (TDMA) media access control (MAC) protocol (EQ-CTDMA) is proposed for the Military Tactical Wireless Mobile Ad Hoc Networks (MTWMANs). The basic idea is that the relay introduces the active spatial diversity to the source on its vacations. A three-node delay model of EQ-CTDMA is established by the M/G/1 N-policy queue with multiple exhaustive vacations, which provides a way to balance the rate gain in the source S and the delay cost in the relay R by deriving a utilization optimization function with the delay sensitive traffic constraint. Furthermore, based on some reasonable assumptions, the three-node delay model can be extended to analyze the whole traffic queue network. Consequently, we propose a relay selection strategy regarding the average traffic queue length of each relay. Numerical results reveal that with proper tradeoff between delays and rate gains, EQ-CTDMA can significantly improve the utilization throughput in Rayleigh fading channels and in low signal-to-noise ratio (SNR).