Hybrid RF-Baseband Baseband Precoding for Cooperative Multiuser Massive MIMO Systems With Limited RF Chains
Abstract: Massive multiple-input input multiple multiple-output output (massive MIMO) has been studied to improve the throughput in cellular communication systems via spatial degrees of freedom and array gain. However, in massive MIMO systems, due to the hardware cost considerations, it is infeasible to install a radio frequency (RF) chain for each antenna. To deploy massive MIMO within reasonable hardware cost, hybrid precoding is proposed in which the signal is processed by a lowlow dimensional digital baseband precoder and a high high-dimensional nal analog RF precoder. On the other hand, cooperative transmission is another way to enhance system throughput, in which base stations (BSs) can jointly transmit to a user. In this paper, we first investigate the hybrid precoder design for cooperative multiuser tiuser massive MIMO systems. We propose hybrid precoding algorithms for two performance metrics: weighted sum rate and max max-min min fairness. We also propose a low complexity user pairing for both precoder designs. Numerical results show that the proposed hybri hybrid d precoding algorithms outperform existing hybrid precoding algorithms for non non-cooperative cooperative transmissions, and perform closely compared with existing digital precoding algorithms for cooperative transmissions, when the number of users does not exceed the to total tal number of RF chains of the BSs in cooperative (i.e., the largest possible channel rank). In summary, this paper provides a hybrid precoder design guideline for existing and