Performance of multiuser MIMO and network coordination in downlink cellular networks

We consider a wireless network with multiple cells where base stations with multiple antennas transmit to multiple users, each with multiple antennas. Using single-user (SU) MIMO as a baseline, we evaluate the system throughput performance of multiuser (MU) MIMO with generalized zero-forcing beamforming under a multiuser proportional fair scheduling metric. We consider network MIMO extensions of this technique by coordinating transmission among clusters of spatially distributed bases. By significantly mitigating intercell interference, network MIMO provides a tradeoff between improved performance and increased backhaul complexity that depends on the coordination cluster size. We describe a general technique for simulating cellular networks that is applicable to next-generation packet-based cellular standards, and we evaluate the performance of MU and network MIMO in heavily loaded networks. Compared to the SU MIMO baseline, median system throughput can be doubled by coordinating MU MIMO transmission among clusters of 3 adjacent cells.