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Title: Multiuser equalizer for hybrid massive MIMO mmWave CE-OFDM systems
Author: Magueta, Roberto
Teodoro, Sara
Castanheira, Daniel
Silva, Adão
Dinis, Rui
Gameiro, Atílio
Keywords: CE-OFDM
Hybrid analog/digital architectures
Massive MIMO
mmWave communications
Nonlinear equalizer
Issue Date: 15-Aug-2019
Publisher: MDPI
Abstract: This paper considers a multiuser broadband uplink massive multiple input multiple output (MIMO) millimeter-wave (mmWave) system. The constant envelope orthogonal frequency division multiplexing (CE-OFDM) is adopted as a modulation technique to allow an efficient power amplification, fundamental for mmWave based systems. Furthermore, a hybrid architecture is considered at the user terminals (UTs) and base station (BS) to reduce the high cost and power consumption required by a full-digital architecture, which has a radio frequency (RF) chain per antenna. Both the design of the UT’s precoder and base station equalizer are considered in this work. With the aim of maximizing the beamforming gain between each UT and the BS, the precoder analog coefficients are computed as a function of the average angles of departure (AoD), which are assumed to be known at the UTs. At the BS, the analog part is derived by assuming a system with no multi-user interference. Then, a per carrier basis nonlinear/iterative multi-user equalizer, based on the iterative block decision feedback equalization (IB-DFE) principle is designed, to explicitly remove both the multi-user and residual inter carrier interferences, not tackled in the analog part. The equalizer design metric is the sum of the mean square error (MSE) of all subcarriers, whose minimization is shown to be equivalent to the minimization of a weighted error between the hybrid and the full digital equalizer matrices. The results show that the proposed hybrid multi-user equalizer has a performance close to the fully digital counterpart.
Peer review: yes
DOI: 10.3390/app9163363
ISSN: 2076-3417
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IT - Artigos

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