Hybrid precoding based on adaptive RF-chain-to-antenna connection for millimeter wave MIMO systems

Abstract

Hybrid precoding has recently received significant attentions as a promising alternative to fully digital precoding. The existing hybrid precoding architectures can be classified into two categories: fully-connected (FC) and partially-connected (PC) phase shifter (PS) network structures (FC-PS and PC-PS structures). However, the FC-PS structure involves a large number of PSs which leads to a prohibitive power consumption, and the PC-PS structure suffers from a severe spectral efficiency loss in spite of low power consumption. This paper considers a novel adaptive RF-chain-to-antenna connection based on switch network (AC-S) hybrid precoding architecture, which consists of a digital precoder, an analog switch network and an analog PS network. The advantage of the proposed architecture lies in achieving a satisfactory spectral efficiency while maintaining a relatively low power consumption due to the adaptive connection from a radio frequency (RF) chain to all antennas via a switch network. Based on the aforementioned architecture, an effective hybrid precoding algorithm is presented. In the proposed algorithm, the analog PS precoding matrix, the analog switch precoding matrix and the digital precoding matrix are optimized via a block coordinate descent method, and a stable solution can be obtained by several iterations. Simulation results demonstrate that the proposed algorithm with the AC-S structure not only obtains considerably better spectral efficiency than the PC-PS structure but also offers a lower power consumption than the FC-PS structure.