How to approach zero-forcing under RF chain limitations in large mmWave multiuser systems?

摘要: High cost of millimeter wave (mmWave) hardware precludes the possibility to support each antenna element with a dedicated radio frequency (RF) chain in large-scale mmWave systems. It thus makes conventional baseband precoding, such as zero-forcing (ZF) which is deemed virtually optimal large array regime, impractical. In this paper, we consider RF limitations present multiuser systems and propose approach desirable yet infeasible ZF precoding by essentially steering beam towards user's strongest path, termed MUBS, through analog processing at domain. Rates achieved both proposed MUBS are then derived closed form. We further study rate loss relative upper bound imposed find that gap converges finite limit transmit number N t goes large. Since achievable grows without increases, scheme promises achieve most rates . Numerical results also provided validate performance scheme.