A Hardware-Efficient Analog Network Structure for Hybrid Precoding in Millimeter Wave Systems

TL;DR

This paper introduces a hardware-efficient hybrid precoding structure for millimeter wave systems that uses fixed phase shifters and switch networks to reduce hardware complexity while maintaining spectral efficiency.

Contribution

It proposes a novel fixed phase shifter implementation and a switch network for adaptive connections, reducing the number of phase shifters and switches needed.

Findings

Achieves higher hardware efficiency with fewer phase shifters.

Group-connected mapping balances spectral efficiency and hardware complexity.

Outperforms existing hybrid precoding methods in simulations.

Abstract

Hybrid precoding has been recently proposed as a cost-effective transceiver solution for millimeter wave (mm-wave) systems. While the number of radio frequency (RF) chains has been effectively reduced in existing works, a large number of high-precision phase shifters are still needed. Practical phase shifters are with coarsely quantized phases, and their number should be reduced to a minimum due to cost and power consideration. In this paper, we propose a novel hardware-efficient implementation for hybrid precoding, called the fixed phase shifter (FPS) implementation. It only requires a small number of phase shifters with quantized and fixed phases. To enhance the spectral efficiency, a switch network is put forward to provide dynamic connections from phase shifters to antennas, which is adaptive to the channel states. An effective alternating minimization (AltMin) algorithm is developed with closed-form solutions in each iteration to determine the hybrid precoder and the states of switches. Moreover, to further reduce the hardware complexity, a group-connected mapping strategy is proposed to reduce the number of switches. Simulation results show that the FPS fully-connected hybrid precoder achieves higher hardware efficiency with much fewer phase shifters than existing proposals. Furthermore, the group-connected mapping achieves a good balance between spectral efficiency and hardware complexity.