LAUSR

A millimeter wave (mmWave) and sub-6 GHz ($\mu$Wave) dual-mode network can take advantages of the signals over both bands. The user scheduling in the medium access layer and the transmit precoding in the physical layer are coupled and should be optimized jointly. This work investigates the joint cross-layer optimization problems for two dual-mode systems: the full dual transmission system in which each user equipment can be scheduled over both frequency bands and the half dual transmission system in which each user equipment can only be scheduled over one band. A concave expression is adopted to lower-bound the achievable rate of each user equipment with perfect and imperfect channel estimation. Based on the lower bound, effective algorithms are proposed to solve the joint cross-layer optimization problems. The proposed algorithms can also be used for other dual-mode networks. Simulations show superiority of joint transmit precoding for the two frequency bands signals. Moreover, the full dual transmission system outperforms the half dual transmission system in terms of the minimum rate. The rate degradation of the half dual transmission system is insignificant while its implementation complexity is much lower than the full dual transmission system.