Sequentially ordered backoff: Towards implicit resource reservation for wireless LANs

In this paper, we present SOBO, a novel hybrid MAC protocol using sequentially ordered backoff in wireless LANs. SOBO eliminates packet collisions and wasted idle backoff slots by introducing implicit resource reservation into 802.11 DCF. In SOBO, the AP divides time into repeating cycles by beacon frames. Exploiting the implicit information of successful transmission order in every cycle, sequentially ordered backoff in a distributed manner during reservation period is achieved without extra control packets. In addition, we propose a novel scheme to estimate the number of contention stations, and design an adaptive contention window algorithm. We also analyze the robustness of SOBO against message losses in realistic networks with channel errors. The performance of SOBO is verified via extensive simulations with different scenarios. Our simulation results show that SOBO achieves a significant increase in network throughput compared to the legacy 802.11 DCF.