An analysis of a modified point coordination function in IEEE 802.11

Since the point coordination function (PCF) in the IEEE 802.11 is based on a centralized polling protocol, some bandwidth is wasted due to the polling overheads and also due to packets that are issued in case a polled station does not have any data to transmit. In order to reduce this waste and increase the channel utilization, we have proposed a modified version of the standard PCF. The modified PCF uses a distributed polling protocol (DPP) as the access mechanism for the uplink transmission of real-time traffic. The transmission period in the modified PCF consists of a distributed polling protocol period (DPPP) which is controlled by the DPP and the real-time traffic downlink period (KTDP). Our proposal further includes a technique for dealing with the hidden station problem for use together with the proposed modification. In this paper, an analysis is done to compare the performance of the modified PCF with the standard PCF in terms of number of supportable stations in a contention-free period (CFP) and the channel efficiency. The analytical results show that the modified PCF can support a much higher number of stations than the standard PCF. In addition, the channel efficiency of the modified PCF is better under the assumption that there is no hidden station in the system. The results imply that the channel utilization of the modified PCF is better than the standard PCF.