AN INTERFERENCE AND BEAM SQUINT AWARE HYBRID MASSIVE MIMO FOR SPATIAL WIDEBAND BDMA CHANNELS

2022-2-10
Özen, Hakan
This study investigates interference and beam squint aware analog beamformer design for massive multiple-input multiple-output (MIMO) systems for spatial wideband beam division multiple access (BDMA) channels. Single carrier frequency domain equalization (SC-FDE) is employed in uplink frequency selective channels. We first design interference and beam squint aware (BSA) narrowband generalized eigenbeamformer (BSA NB GEB) based on a phase shifter (PS) network using slowly varying long-term channel statistics. We show that the proposed BSA NB GEB, which has a strong interference suppression capability, maximizes the mutual information in reduced dimension under interference and spatial wideband effect. On the other hand, we find a hypothetical interference and beam squint aware optimal wideband generalized eigenbeamformer (WB GEB), which is designed for each frequency bin separately. In order to realize WB GEB physically, we propose an interference aware least square (LS) sense optimal true-time-delay (TTD) network aided analog beamformer as an effective approximation of WB GEB. Additionally, we design an interference unaware TTD network-based analog beamformer (WB DFT via TTD) extending conventional NB DFT analog beamformer. Constant-modulus phase-only approximations of the proposed GEBs are found by phase extraction with alternating minimization-based methods for fully connected array structure. Computational complexities of the proposed designs are presented. Iterative block decision feedback equalization (IB-DFE) method is employed in digital beamformer based on minimum mean square error (MMSE) criterion. Simulation results show the superiority of the proposed designs over existing state-of-the-art approaches in terms of beam pattern, outage capacity, spectral efficiency, and bit-error-rate (BER).

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Citation Formats
H. Özen, “AN INTERFERENCE AND BEAM SQUINT AWARE HYBRID MASSIVE MIMO FOR SPATIAL WIDEBAND BDMA CHANNELS,” M.S. - Master of Science, Middle East Technical University, 2022.