Hybrid Beamforming Receivers for Millimeter-wave MIMO Communication

In future millimeter-wave communication systems, advanced multi-antenna techniques promise to open up new opportunities to increase data rates, throughput and network density. Examples of such techniques include various single-user or multi-user MIMO, adaptive interference cancellation, spatio-temporal equalization etc. While the underlying signal processing can be implemented using digital beamforming (DBF), the high power consumption associated with LO distribution circuits, data converters and the digital baseband processor makes DBF infeasible for high element count antenna arrays. RF-domain phased-arrays, on the other hand, can support a large number of antenna elements in a power efficient manner, but are limited in terms of algorithmic flexibility. Hybrid beamformers provide an effective compromise by performing the bulk of the spatial signal processing at RF and using a handful of downconversion chains to realize additional spatio-temporal processing in the digital domain. In this talk, two types of hybrid beamforming architectures, namely the partially-connected (or sub-array) type and the fully-connected type are introduced. Following a discussion of their advantages and disadvantages, we present our recent research on the design of fully-connected hybrid beamforming receivers. In particular, we will present transceiver design techniques that enable multi-stream MIMO reception, millimeter-wave carrier aggregation and adaptation of front-end beamforming weights that can enable autonomous interference suppression, spatial equalization etc.