Millimeter Wave MIMO With Lens Antenna Array: A New Path Division Multiplexing Paradigm
Millimeter wave (mmWave) communication is a promising technology for future wireless systems, while one practical challenge is to achieve its large antenna gains with only limited radio frequency (RF) chains for cost effective implementation. To this end, we study in this paper a new lens antenna array enabled mmWave multiple input multiple output (MIMO) communication system. We first show that the array response of lens antenna arrays follows a "sinc" function, where the antenna element with the peak response is determined by the angle of arrival (AoA)/departure (AoD) of the received/transmitted signal. By exploiting this unique property along with the multi path sparsity of mmWave channels, we propose a novel low cost and capacity achieving spatial multiplexing scheme for both narrow band and wide band mmWave communications, termed path division multiplexing (PDM) where parallel data streams are transmitted over different propagation paths with simple per path processing. We further propose a simple path grouping technique with group based small scale MIMO processing to effectively mitigate the inter stream interference due to similar AoAs/AoDs. Numerical results are provided to compare the performance of the proposed mmWave lens MIMO against the conventional MIMO with uniform planar arrays (UPAs) and hybrid analog/digital processing. It is shown that the proposed design achieves significant throughput gains as well as complexity and cost reductions, thus leading to a promising new paradigm for mmWave MIMO communications.
IEEE Transactions on Communications