Diversity-Multiplexing Tradeoff for Opportunistic Access Systems

This letter examines the diversity-multiplexing tradeoff (DMT) for the opportunistic access system (OAS) with a delay-constrained traffic. In particular, the OAS adopts a random access framework: The transmitter first performs channel probing (CP) slot by slot, and in each time slot, it tries to access one of the candidate channels; when the CP is successful, it will decide to transmit or give up for another round of CP, based on the obtained channel state information (CSI). Under the above model, the outage probability of the OAS is derived for both the cases with zero and perfect CSI at the transmitter, respectively. Then, the DMT of the considered system is obtained under both the finite and infinite signal-to-noise ratio (SNR) regimes. It is shown by analysis that multi-round CP together with perfect transmitter side CSI can significantly improve the system performance.