An Iterative Resource Allocation and Precoder Design for Wideband mmWave MIMO-OFDM System With Large-Scale Users

For the scenario of large-scale users in millimeter wave (mmWave) multi-user multiple-input multiple-output (MU-MIMO)-orthogonal frequency division multiplexing (OFDM) systems, power allocation on each subcarrier (SC), association between SCs and users (SC-UE association) and precoder design are mutually dependent due to the hybrid MIMO-OFDM structure. This interdependence suggests that these factors should be jointly considered and optimized to make full use of both spatial and frequency diversity. In this paper, an iterative optimization framework is proposed for optimizing both the sum rate and the minimum user rate considering the beam squint effect. The optimization framework first performs a coarse SC-UE association based on an SC-level channel clustering, and then alternatively optimizes the hybrid analog and digital (HAD) precoder and SC-UE association in an iterative manner. The SC-UE association problems are solved by the greedy algorithm and heuristic method for sum rate and minimum rate optimization problems, respectively. The computational complexities of the proposed methods are evaluated and compared with several existing benchmarks. Numerical simulations show that the proposed methods outperform the corresponding benchmarks, while hold comparable running times by contrast due to its fast convergence rate.