Full-Duplex mmWave Massive MIMO Systems with A Joint Self-Interference Cancellation Design Based on Zero-Space Projection and Angular Excluding

With the continuous growth of capacity demand, millimeter-wave (mmWave) massive multiple-input multiple-output (MIMO) systems have been considered as one of the primary research focuses of sixth generation (6G) wireless communication networks. Full-duplex (FD) technology can further improve the performance of mmWave massive MIMO systems. However, the strong self-interference (SI) severely limits the FD performance. In this paper, a hybrid beamforming (HBF) scheme with joint self-interference cancellation (SIC) is proposed for point-to-point FD systems. The transmit/receive radio frequency (RF) beamformers are constructed according to the angle-of-departure (AOD)/angle-of-arrival (AOA) information. A SIC part is added to the combiner to suppress the residual SI, which can be obtained with the zero-space projection of the equivalent SI channel. Then, by fixing the analog parts, the problem reduces to the optimization of low dimensional digital processors, which can be solved by the minimization of minimum mean squared error (MMSE) algorithm. It's shown that with the increase of the antenna array size, the achievable rate capacity of the proposed FD mmWave massive MIMO systems with joint SIC design is about twice that of the half-duplex (HD) systems. Moreover, as the ratio of the number of RF chains to data streams increases, the ratio of this rate capacity is higher and much closer to 2.