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Wireless Communications and Mobile Computing
Volume 2017, Article ID 9171068, 13 pages
https://doi.org/10.1155/2017/9171068
Research Article

Iterative Multiuser Equalization for Subconnected Hybrid mmWave Massive MIMO Architecture

1Instituto de Telecomunicações (IT) and DETI, Universidade de Aveiro, Aveiro, Portugal
2Instituto de Telecomunicações (IT) and Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Caparica, Portugal

Correspondence should be addressed to R. Magueta; tp.au@mlr

Received 1 August 2017; Accepted 3 December 2017; Published 20 December 2017

Academic Editor: Patrick Seeling

Copyright © 2017 R. Magueta et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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 pure-analog 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.