Canonical space-time coordinates for multiuser wireless communications

We propose a space-time multiuser detection scheme for wireless communications that projects the received signal onto a fixed set of basis signals. The basis signals are dictated by a canonical characterization of channel propagation dynamics in terms of discrete multipath delays, Doppler shifts, and directions of arrival. They capture the essential degrees of freedom in the received signal. The canonical space-time coordinates induced by the underlying basis provide a natural framework for multi-access interference (MAI) suppression and diversity processing. The signal of the desired user is concentrated in a subset of coordinates, while the interference generally occupies the entire space-time coordinate system. It is demonstrated that MAI suppression can be improved by incorporating a subset of coordinates where the desired user is absent.