Covariance Matrix Reconstruction for DOA Estimation in Hybrid Massive MIMO Systems

Abstract

Multiple signal classification (MUSIC) has been widely applied in multiple-input multiple-output (MIMO) receivers for direction-of-arrival (DOA) estimation. To reduce the cost of radio frequency (RF) chains operating at millimeterwave bands, hybrid analog-digital structure has been adopted in massive MIMO transceivers. In this situation, the received signals at the antennas are unavailable to the digital receiver, and as a consequence, the spatial covariance matrix (SCM), which is essential in MUSIC algorithm, cannot be obtained using traditional sample average approach. Based on our previous work, we propose a novel algorithm for SCM reconstruction in hybrid massive MIMO systems with multiple RF chains. By switching the analog beamformers to a group of predetermined DOAs, SCM can be reconstructed through the solutions of a set of linear equations. In addition, based on insightful analysis on that linear equations, a low-complexity algorithm, as well as a careful selection of the predetermined DOAs, will be also presented in this paper. Simulation results show that the proposed algorithms can reconstruct the SCM accurately so that MUSIC algorithm can be well used for DOA estimation in hybrid massive MIMO systems with multiple RF chains.

Fast Reconstruction and Iterative Updating of Spatial Covariance Matrix for DOA Estimation in Hybrid Massive MIMO

“…To address this issue, we have developed an algorithm in [15] for SCM reconstruction in massive MIMO with single RF chain. As only one RF chain is considered in [15], the procedure for SCM reconstruction requires a long time duration because the predetermined DOAs has to be swept sequentially. In this paper, we will introduce a fast beam sweeping algorithm in Section III so that the SCM can be reconstructed much faster.…”

“…as a group of predetermined DOA angles. For the single RF chain case as in [15], the analog beamformers switch the beam directions to the predetermined DOAs in (8) sequentially. Then, by collecting the received power on each predetermined DOA, the SCM can be reconstructed through solving a set of linear equations.…”

“…In above, we only consider the n-th RF chain. In fact, the procedure from (15) to (22) can be also conducted for all the other RF chains simultaneously. In other words, the beam sweepings over Θ n 's with n = 0, 1, • • • , N − 1 can be conducted in a parallel manner.…”

“…To utilize the high resolution property of MUSIC algorithm, we have developed a beam sweeping algorithm for SCM reconstruction in massive MIMO system with single RF chain [15]. Based on our previous works in [15], we will propose a fast beam sweeping algorithm in this paper for SCM reconstruction in hybrid massive MIMO systems with multiple RF chains. In the presence of multiple RF chains, the predetermined DOA required in [15] are divided into several sub-groups, with each sub-group corresponding to one RF chain.…”

“…Based on our previous works in [15], we will propose a fast beam sweeping algorithm in this paper for SCM reconstruction in hybrid massive MIMO systems with multiple RF chains. In the presence of multiple RF chains, the predetermined DOA required in [15] are divided into several sub-groups, with each sub-group corresponding to one RF chain. Then, by beam sweeping simultaneously on all RF chains, the predetermined DOAs can be swept in a parallel manner, so that the SCM can be reconstructed much faster than our previous works.…”