Access point cooperation for collision-free polling between distributed real-time networks

In WLANs, collision-free communication is desired for real-time wireless video transmission (WVT) systems. A polling-based access scheme enables quality of service (QoS) and priority control over legacy WLAN stations (STAs). However, when multiple moving basic service sets (BSSs) are operating nearby in a polling-based access scheme, signal collisions between BSSs occur, and system performance of the WVT system degrades. Furthermore, the BSSs movements cause difficulties in arranging an access controller (AC) that manages the polling periods of multiple BSSs to avoid the signal collisions. This paper describes an adaptive access point (AP) cooperation scheme where each AP autonomously controls its polling period according to dynamic channel conditions. A network simulation using OPNET® demonstrates that the proposed scheme can enable the coexistence of up to five APs with a packet loss rate (PLR) of less than 10-6 and a delay of less than 50 ms for real-time communications.