  Hybrid precoders and combiners are designed for cooperative cell-free
multi-user millimeter wave (mmWave) multiple-input multiple-output (MIMO)
cellular networks for low complexity interference mitigation. Initially, we
derive an optimal hybrid transmit beamformer (HTBF) for a broadcast scenario
considering both total and per access point (AP) power constraints. Next, an
optimal successive hybrid beamformer technique is proposed for unicast and
multicast scenarios which relies on the optimal minimum variance distortionless
response (MVDR). We demonstrate that it mitigates both the interuser and
intergroup interference, while successively ensuring orthogonality to the
previously scheduled users/user groups. Furthermore, it is shown theoretically
that the proposed schemes are capable of supporting a large number of users.
Subsequently, a Bayesian learning (BL) based method is conceived for jointly
designing the RF and baseband precoders/combiners for the various scenarios
considered. Furthermore, we also conceive the uplink counterpart of our HTBF
scheme, which is based on maximizing the signal-tointerference-plus noise ratio
(SINR) of each individual user. Finally, the efficacy of the proposed schemes
is characterized by our extensive simulation results in terms of cancelling the
interuser/intergroup interference, which improves the spectral efficiency.
