  Millimeter wave (mmW) communications at the 60 GHz unlicensed band is seen as
a promising approach for boosting the capacity of wireless local area networks
(WLANs). If properly integrated into legacy IEEE 802.11 standards, mmW
communications can offer substantial gains by offloading traffic from congested
sub-6 GHz unlicensed bands to the 60 GHz mmW frequency band. In this paper, a
novel medium access control (MAC) is proposed to dynamically manage the WLAN
traffic over the unlicensed mmW and sub-6 GHz bands. The proposed protocol
leverages the capability of advanced multi-band wireless stations (STAs) to
perform fast session transfers (FST) to the mmW band, while considering the
intermittent channel at the 60 GHz band and the level of congestion observed
over the sub-6 GHz bands. The performance of the proposed scheme is
analytically studied via a new Markov chain model and the probability of
transmissions over the mmW and sub-6 GHz bands, as well as the aggregated
saturation throughput are derived. In addition, analytical results are
validated by simulation results. Simulation results show that the proposed
integrated mmW-sub 6 GHz MAC protocol yields significant performance gains, in
terms of maximizing the saturation throughput and minimizing the delay
experienced by the STAs. The results also shed light on the tradeoffs between
the achievable gains and the overhead introduced by the FST procedure.
