A proposal of WLAN control scheme using separated channel

In WLAN systems, distributed coordination function (DCF) is used to avoid transmission collision. When an error occurs, the transmitter extends its contention window for the next retransmission to avoid more errors. But this may cause an unfairness problem; in noisy conditions MTs may find it difficult to get transmission opportunities, especially in a heterogeneous network with a large number of WLAN access points (AP). In this paper, a new control scheme with separate control channel for WLAN is proposed. When a receiver detects a transmission error, it replies special signal via the control channel to abort transmission of corrupted data. This way the transmission of corrupted data can be reduced. Thus the it is no longer necessary to change contention window size and all MTs have the same probability to get transmission opportunities. The simulation results show that by using this technique, the average throughput of MTs whose packet error rates (PER) are larger than 0.3 can be at least 2 times compared with conventional scheme.