Understanding the FICA MAC protocol in high data rate WLANs

Recently wireless radios and hardware technologies have been developed that allow operation on very wide channels and that can support very high physical layer data rates (1Gbps and up). However, it is proven that the conventional 802.11 CSMA/CA MAC protocol causes a drastic under-utilization of such high-speed channels. In order to improve channel utilization, a new scheme, called, Fine-Grained Channel Access (FICA), has been recently put forward. While the FICA approach appears more promising than the other proposed schemes for high data rate WLANs, it has not been studied extensively before. Hence, in this paper, we focus on the FICA MAC protocol, and we study this protocol thoroughly in different traffic scenarios and network topologies. We identify, for the first time, some of the serious problems that can arise with the FICA MAC protocol. We call these problems deafness, muteness and a form of hidden terminal problem. We quantify the impact of these problems on the performance of FICA via extensive simulations. Our results show that under some typical scenarios, FICA can perform even worse than the conventional 802.11 DCF, in terms of channel utilization, per-user-throughput or fairness. The insights obtained in this paper motivates the need for addressing FICA's problems and paves the path for future development of better new MAC protocols for high data rate WLANs.