On the packet delay in wireless local area networks with access port diversity and power control

Wireless local area networks have attracted considerable interest. To enhance the user capacity of such wireless packet communication systems, an architecture where terminals share a common radio channel and several access ports has been proposed in the literature. In this paper we will investigate the performance of such systems, considering several scenarios. Firstly access ports may only receive packets from nearby terminals. Secondly, all access ports may receive packets from any terminal. We distinguish between a highly mobile case, where terminals are assumed to be in a different position in every timeslot, and a stationary case, in which the terminals are at the same place all the time. Our results for slotted ALOHA packet access show that the delay performance of a mobile system is much better than a stationary system, due to the fact that in the mobile case all terminals get in a 'good' position every now and then. Access port diversity slightly improves the performance of a stationary system. A clear difference between the mobile system and the stationary system is that the stationary system is 'unfair', in the sense that distant terminals have considerably worse performance than nearby terminals. We show that by using power control this problem can be solved. The delay performance of the mobile system can also be improved considerably, by using another power control algorithm.