Hybrid Precoding for Device-to-Device Communication at MmWave Frequencies

One of the most important challenges in 5G Deviceto-Device (D2D) networks is the interference management. In order to cope with this problem, D2D communication is proposed to operate at Millimeter Wave (mmWave) frequencies which have relatively low Multi-User Interference (MUI). However, mmWave systems main challenge is to realize sufficient operating link quality; this is resolved by deploying directional beamforming with large antenna arrays at both sides of the D2D pair. In addition, to overcome the issue of high cost and power consumption of high-bandwidth mixed-signal devices, mmWave precoding is divided in the analog and digital domains. In this paper, a hybrid precoding technique is proposed to overcome the hardware constraints on the analog-only beamforming as well as to approach the performance of the complicated digital solutions. This technique allows multiple concurrent D2D links, improving by this the network capacity and spectrum efficiency. Simulations results done using MATLAB show that the proposed algorithm approaches the rates achieved by unconstrained digital beamforming solutions, and proves the efficiency of D2D at mmWave.