Due to the power consumption issue of user equipment (UE), Single-Carrier FDMA (SC-FDMA) has been selected as the uplink multiple access scheme of 3GPP Long Term Evolution (LTE). Similar to OFDMA downlink, SC-FDMA enables multiple UEs to be served simultaneously in uplink as well. However, the single carrier characteristic requires that all the allocated subcarriers to a UE must be contiguous in frequency with each time slot. Moreover, a UE should adopt the same modulation and coding scheme at all allocated subcarriers. These two constraints do limit the scheduling flexibility. In this paper, we formulate the UL scheduling problem with proportional fairness support by taking two constraints into consideration. Since this optimization had been proven to be an NP-hard problem, we further develop one heuristic algorithm. We demonstrate that competitive performance can be achieved in terms of system throughput, which is evaluated by using 3GPP LTE system model simulations.

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.

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