A New ACK Policy To Mitigate the Effects of Coexisting IEEE 802.11/802.11e Devices

In IEEE 802.11 wireless networks, EDCA users´ performance may be degraded because of the existence of legacy users and therefore would get a lower priority service. Such effects are mainly due to the fact that EDCA users are controlled by different contention parameters that are distributed in the beacon frames, but there is no control over legacy users as their contention parameters are PHY dependent, i.e. they have constant values. In this paper, we discuss different aspects of the legacy DCF and EDCA users coexistence. Also, we propose a simple distributed management scheme (called NZ-ACK) to mitigate the influence of legacy DCF on EDCA performance in networks consisting of both types of users without any modifications to legacy users. Finally, we use Opnet simulation to evaluate the performance of NZ-ACK. Results show that NZ-ACK outperforms 802.11 in terms of maintaining the priority of service and delay bounds of EDCA users while providing acceptable throughput for legacy users.