Using reciprocal channel information in multiuser MIMO scheduling

Authors: Marios Kountouris, David Gesbert, Lars Pittman

Affiliation: EURECOM, Sophia-Antipolis

e-mail: marios.kountouris@eurecom.fr , david.gesbert@eurecom.fr

Abstract:

The design of multiuser MIMO systems hinges on the problem of the joint design of antenna combining schemes together with a properly matched scheduling protocol that may include some degree of spatial division multiple access (SDMA). The resolution of the problem should be done under constraint of reasonably low feedback of transmitter channel state information (CSIT) and complexity. Useful information relevant to the scheduler lies untapped in the long term statistical channel information, which is typically acquired either by channel reciprocity or by almost negligible per-slot feedback.

We show how statistical channel information can be efficiently combined with partial instantaneous CSIT to derive scheduling metrics for the downlink of multiuser MIMO systems. Based on the combined channels statistics and limited instantaneous feedback, we form a channel estimate for each user which is exploited for user selection as well as to design an improved transmission matrix. We show the capacity gain of this type of approach over opportunistic schemes in various settings.