Downlink Packets Scheduling in enterprise WLAN

Enterprise WLAN consists of many APs connected to wired backbone network. Conventional DCF mechanism can not completely prevent conflicts between APs which cause large quantities of transmission failure and retransmission overhead. However, to keep compatible with 802.11-compliant clients, it is difficult to discard DCF. In this paper, we proposed a framework called DPS, which incorporates centralized scheduling with DCF. In DPS, downlink packets are not forwarded as soon as they arrived at APs. Instead, a central controller schedules their forwarding. APs still use DCF to send downlink packets according to the controller´s instructions. DPS preserves DCF and requires no modifications to 802.11-compliant clients. Under DPS framework, we proposed a scheduling algorithm, ensuring downlink packets be sent with high success rate. In this way, we can significantly reduce transmission failure and retransmission overhead. Experiment results indicated that DPS can significantly improve the performance of enterprise WLAN compared with DCF without any scheduling.