CCMA: Collision coordinated multiple access in wireless LAN

In wireless LANs, STAs access the media based on CSMA/CA. However, the efficiency degrades as the number of STAs increase. To address this issue, in this paper, we present a cross-layer design of distributed contention based MAC protocol, which significantly improves the uplink performance of WLANs. CCMA consists of two phases: 1) contention phase, in which the AP broadcast a polling frame, and then STAs which have pending frames transmit a contention physical signal simultaneously. The AP resolves the number of STAs participating in contention and responses a compound signal from which STAs could determine their transmission order; 2) contention free phase, in which STAs transmit their frames in the order determined from previous contention. In CCMA, STAs are scheduled to transmit their data frames immediately after their predecessors without backing off, thus reducing the channel access overhead and improving the efficiency. Numerical results show that CCMA outperforms the best performance of DCF from %8 to %72.