# Iterative Analog-Digital Multi-User Equalizer for Wideband Millimeter Wave Massive MIMO Systems
); [EMAIL_ADDRESS] (A.S.); [EMAIL_ADDRESS] (A.G.)  
[PERSON] 1  
1 Departamento de Eletrionica, Telecomunicacoes e Informatica (DETI), Instituto de Telecomunicacoes (IT), University of Aveiro, 3810-193 Aveiro, Portugal; [EMAIL_ADDRESS] (D.C.); [EMAIL_ADDRESS] (P.P. ); [EMAIL_ADDRESS] (A.S.); [EMAIL_ADDRESS] (A.G.)  
[PERSON] 1  
1 Departamento de Eletrionica, Telecomunicacoes e Informatica (DETI), Instituto de Telecomunicacoes (IT), University of Aveiro, 3810-193 Aveiro, Portugal; [EMAIL_ADDRESS] (D.C.); [EMAIL_ADDRESS] (P.P. ); [EMAIL_ADDRESS] (A.S.); [EMAIL_ADDRESS] (A.G.)  
[PERSON] 1  
1 Departamento de Eletrionica, Telecomunicacoes e Informatica (DETI), Instituto de Telecomunicacoes (IT), University of Aveiro, 3810-193 Aveiro, Portugal; [EMAIL_ADDRESS] (D.C.); [EMAIL_ADDRESS] (P.P. ); [EMAIL_ADDRESS] (A.S.); [EMAIL_ADDRESS] (A.G.)  
[PERSON] 1  
1 Departamento de Eletrionica, Telecomunicacoes e Informatica (DETI), Instituto de Telecomunicacoes (IT), University of Aveiro, 3810-193 Aveiro, Portugal; [EMAIL_ADDRESS] (D.C.); [EMAIL_ADDRESS] (P.P. ); [EMAIL_ADDRESS] (A.S.); [EMAIL_ADDRESS] (A.G.)  
[PERSON] 1  
1 Departamento de Eletrionica, Telecomunicacoes e Informatica (DETI), Instituto de Telecomunicacoes (IT), University of Aveiro, 3810-193 Aveiro, Portugal; [EMAIL_ADDRESS] (D.C.); [EMAIL_ADDRESS] (P.P. ); [EMAIL_ADDRESS] (A.S.); [EMAIL_ADDRESS] (A.G.)  
[PERSON] 1  
1 Departamento de Eletrionica, Telecomunicacoes e Informatica (DETI), Instituto de Telecomunicacoes (IT), University of Aveiro, 3810-193 Aveiro, Portugal; [EMAIL_ADDRESS] (D.C.); [EMAIL_ADDRESS] (P.P. ); [EMAIL_ADDRESS] (A.S.); [EMAIL_ADDRESS] (A.G.)  
[PERSON] 1  
1 Departamento de Eletrionica, Telecomunicacoes e Informatica (DETI), Instituto de Telecomunicacoes (IT), University of Aveiro, 3810-193 Aveiro, Portugal; [EMAIL_ADDRESS] (D.C.); [EMAIL_ADDRESS] (P.P. ); [EMAIL_ADDRESS] (A.S.); [EMAIL_ADDRESS] (A.G.)  
[PERSON] 1  
1 Departamento de Eletrionica, Telecomunicacoes e Informatica (DETI), Instituto de Telecomunicacoes (IT), University of Aveiro, 3810-193 Aveiro, Portugal; [EMAIL_ADDRESS] (D.C.); [EMAIL_ADDRESS] (P.P. ); asilva@av.it (A.S.); [EMAIL_ADDRESS] (A.G.)  
[PERSON] 1  
1 Departamento de Eletrionica, Telecomunicacoes e Informatica (DETI), Instituto de Telecomunicacoes (IT), University of Aveiro, 3810-193 Aveiro, Portugal; dcastanheira@av. or power amplifiers for mmWave make it impractical to have one dedicated radio frequency (RF) chain for each transmit and receive antenna [7]. Therefore, the design of new beamforming techniques, different from those adopted for the sub-6 GHz band, is a necessity [8]. A simple approach is the use of fully analog beamforming techniques using only phase shifters to overcome the hardware limitations, allowing low complexity implementations [3]. However, the performance of only analog beamforming techniques is limited, and it is typically only used for single-stream transmission [9]. To overcome the performance limitations, some hybrid analog-digital architectures were proposed in [9], where part of the signal processing is performed in the analog domain, and a reduced-complexity processing is left to the digital domain. Concerning the modulation scheme, orthogonal frequency division multiplexing (OFDM) is widely employed in current standards. However, OFDM is subject to high amplitude signal fluctuations due to nonlinear distortions caused by the power amplifiers and which degrade the performance of the system. The single-carrier frequency-division multiple access (SC-FDMA) is an interesting approach to deal with this problem, but the major drawback is the residual interference. It is well known that linear equalizers are not the most efficient way to deal with this issue, and nonlinear/iterative equalizers, namely those based on iterative block decision feedback equalization (IB-DFE) principle, have been shown to present better performance [10].