IEEE VTS NSW CHAPTER DISTINGUISHED LECTURE: Omnidirectional Precoding for Massive MIMO with Uniform Rectangular Array

#Massive #MIMO

Abstract: In the public channels, it is desirable to transmit the common signals omnidirectionally to ensure cell-wide coverage. In this talk, we first develop low-cost closed-form omnidirectional precoding designs for a massive multiple-input multiple-output (MIMO) system equipped with a uniform rectangular array (URA). In particular, we derive an optimal solution based on the complementary set (CS) or the complete complementary codes (CCC). We prove that the precoding vectors based on the CS or CCC sequences can generate a perfectly flat radiation-power pattern. Since both CS and CCC sequences are binary and constant-modulus, the proposed schemes are well suited to be implemented in the radio frequency (RF) analog domain with low hardware cost and suppressed peak-to-average power ratio (PAPR). The design of the proposed closed-form schemes relies on the existence of the corresponding CS or CCC for a given URA configuration. To overcome the limitations, we further develop an iterative rank-reduction algorithm. It is shown that the proposed algorithm can always obtain three precoding vectors to generate a perfectly flat radiation-power pattern for any URA configuration. By further imposing the constant-modulus constraints for every entries of the precoding matrix, we propose a Newton’s method, which can always obtain a rank-4 omnidirectional precoding matrix for a general URA. The proposed numerical optimzation based schemes complement well the CS- and CCC-based schemes. Overall, this work provides a unified approach to omnidirectional precoding for massive MIMO equipped with URA.