3D Angular-Based Hybrid Precoding and User Grouping for Uniform Rectangular Arrays in Massive MU-MIMO Systems

Abstract

This paper proposes a new user grouping algorithm and three-dimensional (3D) angular-based hybrid precoding (AB-HP) scheme for massive multi-user multiple-input multiple-output (MU-MIMO) systems using uniform rectangular arrays (URA). At first, the users clustered in multiple spots are efficiently grouped according to the proposed user grouping algorithm, which only utilizes the user angle-of-departure (AoD) information and does not require prior knowledge of the number of user groups. By employing the AoD support of the user groups, the RF-beamformer of AB-HP is designed to reduce the inter-group interference, the channel state information (CSI) overhead, and the number of RF chains. Then, the digital baseband precoder of AB-HP is constructed via regularized zero-forcing (RZF) using the effective channel seen from baseband to simultaneously serve the users clustered in multiple groups, by considering three approaches: joint-group-processing (JGP), per-group-processing (PGP) and common-group-processing (CGP). For each approach, the signal-to-interference-plus-noise ratio (SINR) expressions as well as their tight deterministic approximations are derived. To further reduce the number of RF chains, we also propose a new transfer block design, which reduces the number of RF chains down to the number of independent data streams without penalizing the sum-rate performance. Illustrative results reveal that the proposed AB-HP schemes with the relaxed CSI estimation overhead and reduced hardware cost/complexity can closely approach to the sum-rate performance of the single-stage fully-digital precoding (FDP). Furthermore, AB-HP has considerably higher energy efficiency performance compared to FDP due to the reduced number of RF chains. We show through simulation that the proposed AB-HP can offer significantly better performance than existing HP techniques. The computational complexity of AB-HP is also analyzed.INDEX TERMS Massive MIMO, 3D hybrid precoding, user grouping, angle of departure (AoD), uniform rectangular array (URA), RF chain reduction.

Full-Duplex mmWave Massive MIMO Systems: A Joint Hybrid Precoding/Combining and Self-Interference Cancellation Design

“…In [41], a two-stage angular-based hybrid-precoding (HP) technique is proposed for the downlink massive MIMO systems, where the CSI overhead is greatly reduced by designing the RF-stage via AoD parameters. The numerical results in [41] show that the angular-based HP significantly enhances the energy efficiency compared to the single-stage fully-digital precoding (FDP) by means of the reduced number of RF chains. Moreover, the angular-based HP improves the sum-rate capacity with respect to its two-stage HP counterparts as eigen-beamforming based HP [40], block-diagonalization based HP [39], non-orthogonal angle space based HP [35].…”

“…Therefore, the hybrid architectures in [39]- [45] can address two interesting challenges in the massive MIMO systems: (i) the reduced number of RF chains for low power consumption and the hardware cost/complexity, (ii) the low CSI overhead for shorter training sequence. In [41], a two-stage angular-based hybrid-precoding (HP) technique is proposed for the downlink massive MIMO systems, where the CSI overhead is greatly reduced by designing the RF-stage via AoD parameters. The numerical results in [41] show that the angular-based HP significantly enhances the energy efficiency compared to the single-stage fully-digital precoding (FDP) by means of the reduced number of RF chains.…”

“…. Furthermore, the quantized angle-pairs defined in (19) produces the minimum number of angle-pairs in order to cover the complete 3D angular support [41]. It also reduces the number of RF chain utilization, while exploiting all degrees of freedom provided by the intended channel (i.e., Span (F t,i ) ⊂ Span (Φ t,i ) and Span (F r,j ) ⊂ Span (Φ r,j )).…”

Non-Coaxial OAM: Precoding Design, Misaligned Parameter Estimation and Capacity Compensation

“…The proposed capacity compensation pre-processing scheme is designed based on the concentric UCA array structure and the LOS channel characteristics. It is based on the same idea as the angular domain precoding scheme for massive MIMO systems proposed in [37], [38]. The system performance can be ensured by exploiting the specific channel structure without requiring full CSI, leading to a reduced requirement on channel measuring and CSI estimation.…”

Study of 5G-NR-MIMO Links in the Presence of an Interferer

“…In addition, the demands in the real world of next-generation mobile technology for high mobility, low latency, spectrum efficiency, peak data rates, and ultra multi-user experience, with emphasis on multiple users and sharing radio access, are increasing and have expanded the research field. There are a number of threshold conditions that must be met in order to operate multi-user access techniques such as Orthogonal Multiple Access (OMA)/Non-OMA (NOMA) techniques [7][8][9], or Multi-User (MU)-Multiple Input, Multiple Output (MIMO) [10][11][12]. The first condition is the ability to decoding a specific stream transmission, from spatial-multiplexing streams, under a random Signal Interference Noise Ratio (SINR) with random interference signals.…”