Low-Complexity and High-Resolution DOA Estimation for Hybrid Analog and\n Digital Massive MIMO Receive Array

Abstract

A large-scale fully-digital receive antenna array can provide very\nhigh-resolution direction of arrival (DOA) estimation, but resulting in a\nsignificantly high RF-chain circuit cost. Thus, a hybrid analog and digital\n(HAD) structure is preferred. Two phase alignment (PA) methods, HAD PA (HADPA)\nand hybrid digital and analog PA (HDAPA), are proposed to estimate DOA based on\nthe parametric method. Compared to analog phase alignment (APA), they can\nsignificantly reduce the complexity in the PA phases. Subsequently, a fast root\nmultiple signal classification HDAPA (Root-MUSIC-HDAPA) method is proposed\nspecially for this hybrid structure to implement an approximately analytical\nsolution. Due to the HAD structure, there exists the effect of\ndirection-finding ambiguity. A smart strategy of maximizing the average receive\npower is adopted to delete those spurious solutions and preserve the true\noptimal solution by linear searching over a set of limited finite candidate\ndirections. This results in a significant reduction in computational\ncomplexity. Eventually, the Cramer-Rao lower bound (CRLB) of finding emitter\ndirection using the HAD structure is derived. Simulation results show that our\nproposed methods, Root-MUSIC-HDAPA and HDAPA, can achieve the hybrid CRLB with\ntheir complexities being significantly lower than those of pure linear\nsearching-based methods, such as APA.\n