System Performance of Uplink Multi-User MIMO in LTE

In LTE Rel-8, mobile stations are equipped with only one transmit antenna while the base stations can employ multiple receive antennas. As a result, multi-user MIMO can be used in the uplink to enhance system capacity. This paper describes multi-user MIMO in the uplink for LTE and presents system-level simulation results under indoor hotspot, micro-cell, and macro-cell deployment scenarios. Two user pairing strategies, random and orthogonal pairing, are compared. Our results show that random pairing performs as well as orthogonal pairing under realistic implementation constraints. With four receive antennas at the base station, uplink MU-MIMO can increase cell capacity by approximately 30% in indoor hotspot, and 10% in micro-cell and macro-cell deployment. Corresponding improvements in user throughput are also observed, including a gain of between 9-28% in cell edge user throughput.