Multi-user MIMO scheduling in LTE-advanced uplink systems

Due to the facts of wireless data usage being increasing faster now than ever before and more multimedia content being generated by users and uploaded to the network, multi-user MIMO (MU-MIMO) technology would be crucial to improve the LTE-A uplink spectral efficiency for meeting the service demands. On the other side, adopting clustered SC-FDMA technology as the uplink multiple access scheme of LTE-A means that a User Equipment (UE) can be allocated more than one cluster which consists of contiguous RBs (this is the contiguity constraint). Moreover, all allocated RBs to a UE must use the same modulation and coding scheme (this is the robust rate constraint). The two constraints make MU-MIMO UL scheduling more complicated. In this paper, we formulate the MU-MIMO UL scheduling problem with taking two constraints into consideration. Since this optimization had been proven to be an NP-hard problem, we further develop two low-complexity heuristic algorithms. We demonstrate that competitive performance can be achieved in terms of system throughput and fairness index.