A performance investigation of the modified PCF under hidden station problem

A modified version of the point coordination function (PCF) in the IEEE 802.11 standard, called the modified PCF, has been introduced to improve the channel utilization over the standard PCF. The modified PCF is a hybrid scheme incorporating polling and channel sensing. Therefore, a collision might occur in the channel if some stations cannot sense the change of channel status in case there is a station transmitting a packet, the so-called hidden station problem. We present an investigation into the effect of the hidden station problem on the performance of the modified PCF and propose a new collision resolution technique, which presumes a hidden station and then drops the station into a list of hidden stations. Simulation results show that the hidden station problem increases the overall delay of the system in the uplink. However, using the proposed collision resolution technique, the delay can be effectively reduced.