Phase-Noise Mitigation at 60 GHz with a Novel Hybrid MIMO Architecture

Hybrid MIMO architectures provide a simple and effective way to implement millimeter-wave multi-user MIMO, which can deliver extremely high throughput by combining spatial multiplexing and a large bandwidth. Despite both theoretical and practical results being already available, the performance of these systems when including non-idealities is still being analyzed. In this paper we focus on phase noise originating from the multiple PLLs that causes two main problems: symbol rotation and inter-user interference. Although symbol rotation can be mitigated with conventional receiver phase noise tracking schemes, these schemes need to be jointly designed with the transmitted frame, which needs to support multi-user precoding. We analyze different receiver mitigation schemes based either on known training sequences or using blind estimation. Moreover, we propose a novel hybrid base station architecture which feeds back partial information of the status of the transmitter PLLs. Using the PLL status information, baseband compensation can be used to minimize inter-user interference improving the receiver EVM by around 5\,dB.