CSMA/CCA: a modified CSMA/CA protocol mitigating the fairness problem for IEEE 802.11 DCF

Using a distributed coordination function (DCF), the CSMA/CA protocol reduces collisions and improves the overall throughput in the IEEE 802.11 WLAN. To mitigate fairness issues arising with CSMA/CA, we develop a modified version that we term CSMA/CCA (CSMA with copying collision avoidance). A station in CSMA/CCA contends for the shared wireless medium by employing a binary exponential backoff similar to CSMA/CA. Different from CSMA/CA, CSMA/CCA copies the contention window (CW) size piggybacked in the MAC header of an overheard data frame within its basic service set (BSS), and updates its backoff counter according to the new CW size. Simulations illustrate that CSMA/CCA improves fairness relative to CSMA/CA and offers considerable advantages for deployment in the 802.11 standard based WLANs.