A new TDD scheme and interference-aware precoding for device-to-device underlay massive MIMO

In device-to-device (D2D) underlay cellular networks with downlink spectrum sharing, massive MIMO seems promising as the large number of antennas at the base station (BS) can be utilized to suppress interference. However, the channel state information (CSI) from the BS to D2D receivers is required to obtain this advantage. In this paper, we first propose a novel time division duplex (TDD) scheme for D2D users to acquire this CSI, without additional pilot overhead. Moreover, we propose an interference-aware MMSE precoder utilizing the acquired CSI from the BS to not only cellular users but also D2D users to suppress the cellular-to-D2D interference. Simulation results show that our proposed TDD scheme and precoder can significantly improve the achievable sum spectral efficiency (SE) and D2D SE, compared to the classical MMSE precoder. Compared with the interference-aware ZF precoder, whose performance severely degrades for large user numbers, our proposed interference-aware MMSE precoder can always guarantees a high and stable performance in terms of achievable SE.