Iterative Multiuser Equalization for Subconnected Hybrid mmWave Massive MIMO Architecture

Abstract

Millimeter waves and massive MIMO are a promising combination to achieve the multi-Gb/s required by future 5G wireless systems. However, fully digital architectures are not feasible due to hardware limitations, which means that there is a need to design signal processing techniques for hybrid analog-digital architectures. In this manuscript, we propose a hybrid iterative block multiuser equalizer for subconnected millimeter wave massive MIMO systems. The low complexity user-terminals employ pureanalog random precoders, each with a single RF chain. For the base station, a subconnected hybrid analog-digital equalizer is designed to remove multiuser interference. The hybrid equalizer is optimized using the average bit-error-rate as a metric. Due to the coupling between the RF chains in the optimization problem, the computation of the optimal solutions is too complex. To address this problem, we compute the analog part of the equalizer sequentially over the RF chains using a dictionary built from the array response vectors. The proposed subconnected hybrid iterative multiuser equalizer is compared with a recently proposed fully connected approach. The results show that the performance of the proposed scheme is close to the fully connected hybrid approach counterpart after just a few iterations.

Reduced Complexity Detection in MIMO Systems with SC-FDE Modulations and Iterative DFE Receivers

“…Moreover, it also can be considered as a technique that does not require the inversion of matrices, as Equal Gain Combiner (EGC) [21] and Maximum Ratio Combiner (MRC) [22]. An additional issue would be the extension of these techniques to hybrid analog/digital massive MIMO schemes where several antennas share a single RF chain, as in [23,24].…”

“…with I and D being diagonal matrices (I indicates an identity matrix). It can be shown that MM −1 and M −1 M correspond to: (23) and:…”

Multi-User Linear Equalizer and Precoder Scheme for Hybrid Sub-Connected Wideband Systems

“…In [27] two analog precoder schemes for high and low signal-to-noise ratio (SNR) condition were developed. For multi-user sub-connected narrowband architecture, some approaches were also proposed in [28][29][30][31][32]. In [28], the total achievable rate optimization problem with nonconvex constraints was decomposed into a series of sub-rate optimization problems for each sub-antenna array, and then a successive interference cancelation (SIC) based hybrid precoder was proposed.…”

“…A low-complexity hybrid precoding and combining design was discussed in [29], where a virtual path was performed to maximize the channel gain and then, based on the effective channel, a zero-forcing precoding was applied to manage the interference. The scheme proposed in [30] efficiently controlled the multi-user interference by sequentially computing the analog part of the equalizer over the RF chains, using a dictionary obtained from the array response vectors. In [31], the Gram-Schmidt (GS) based antenna selection (AS) algorithm was used to obtain an appropriate antenna subset for the overlapped, interlaced, and dynamic architectures.…”

Effect of Multi-Frequency Beam Alignment on Non-Line-of-Site Vehicle to Infrastructure Communication using CI Model (CI-NLOS-V2I)

“…Mobile communications employing Millimeter wave (mmWave) is seen as a promising frequency band for the mobile, vehicular wireless networking as it is expected to have large spectrum. It is foreseen that it will have excellent potential in reaching extremely high data rates, which will exceed by far traditional cellular systems operating at sub-6 GHz bands [1][2][3][4].…”