Frequency-domain contention and polling MAC protocols in IEEE 802.11 wireless networks: A survey

Shifting from the time domain to the frequency domain is an interesting recent direction that has been exploited to improve the performance of wireless networks. It is shown that the frequency-domain based proposals are of obvious benefits especially for higher rates and densities which are important attributes of the next-generation wireless networks. In this survey paper, we provide an overview of the concept of frequency-domain based contention and polling MAC protocols, and we show how these schemes could enhance the performance of wireless networks. We also attempt to provide a comprehensive survey of such schemes including related proposals for the next-generation IEEE 802.11ax wireless networks. In addition, we compare the surveyed protocols based on factors like the evaluation methods, the number of contention rounds, the conveyed signals, and the purpose of each protocol. We further address different challenges and issues of frequency-domain schemes including the hidden terminal problem, the number of subcarriers, TDMA-like transmissions, coexistence, the number of antennas, machine to machine networks, overlapping networks, and synchronization. Finally, we highlight different possible directions for future work.