Stability Analysis for Bidirectional MABC-DF Relay Networks With Bursty Traffic

In this paper, we investigate a useful inner bound for the stability region of a multiple-access broadcast decode-and-forward (MABC-DF) bidirectional relay channel, where two sources exchange bursty traffic with the assistance of a shared decode-and-forward (DF) relay in two time slots. In contrast to previously reported information-theoretic work, where sources are assumed to be always active, here, we take into account the burstiness of the transmission, and we study an MABC-DF bidirectional relay channel without channel state information (CSI) at the transmitters. A dominant stochastic system that decouples the interaction between the different distributed queues and enables the derivation of a useful inner bound on the stability region of the original MABC-DF system is introduced. We demonstrate that the bursty nature of the transmission modifies the conventional MABC-DF protocol and allows the sources to communicate with each other in two more ways: 1) a direct link or 2) a noninterference DF relaying link. Another outcome is that the investigated stability inner bound depends on the fraction of the time between the two phases of the MABC-DF protocol. The optimal time fraction that maximizes this inner bound for both sources is derived in closed form.