X60: A Programmable Testbed for Wideband 60 GHz WLANs with Phased Arrays

This paper introduces X60, the first SDR-based testbed for 60 GHz WLANs, featuring fully programmable MAC/PHY/Network layers, multi-Gbps rates, and a user-configurable 12-element phased antenna array. Combined these features provide an unprecedented opportunity to re-examine the most important aspects of signal propagation and performance expected from practical 60 GHz systems. Leveraging the testbed's capabilities, we conduct an extensive measurement study, looking at different aspects of indoor 60 GHz links. We find that the presence of reflective surfaces and imperfect beams generated by practical phased arrays together can result in multiple NLoS paths supporting Gbps rates. Additionally, our comparison of different beam adaptation strategies reveals how beam steering even at one end of the link can often be sufficient to restore link quality. Finally, contrary to a common assumption in recent works, we find that a one-to-one MCS to SNR mapping is hard to obtain in typical indoor environments, and probing of more than one MCS index is often required to discover the optimal MCS for a given SNR.