Integrating retransmission diversity with real-time scheduling over wireless links
A cross-layer optimization combining retransmission diversity with multi-user diversity is investigated for wireless communications. To this end, a joint design of adaptive modulation and coding with retransmission-based automatic repeat request protocol is first outlined. This design is then employed to devise multi-user scheduling schemes which can optimally capture the available multiuser and retransmission diversities. In addition, the proposed on-line scheduling algorithms can operate even when the underlying fading channel distribution is unknown a priori, while asymptotically converging to the offline benchmark with guarantees on prescribed fairness and rate requirements. Numerical results are provided to verify the merits of our novel schemes for multi-user transmissions over Nakagami block fading channels.