Opportunistic multichannel Aloha: distributed multiaccess control scheme for OFDMA wireless networks

The authors consider multiaccess control for the uplink in orthogonal-frequency-division-multiple-access wireless networks, where subcarriers are grouped into clusters. A multichannel random access, based on local channel state information (CSI), was investigated, and an opportunistic multichannel Aloha (OMC-Aloha) was proposed accordingly. A key step is to build a mapping from a user´s CSI to its transmission probability and subcarrier allocation. For the sake of comparison, the throughput of the optimal centralized scheduling was also characterized by using the Extreme-Value Theory of order statistics. The authors show that the OMC-Aloha is asymptotically order optimal, in the sense that the only performance loss compared to the optimal centralized scheduling is due to the contention inherent in random access. In addition, they examine the proportional fairness in heterogeneous systems