Multiuser Resource Allocation Algorithms for Downlink OFDMA-based MIMO Network

Abstract—The problem of simultaneous multiuser resource (subcarriers-and-bits) allocation algorithm in OFDMA-based multiple input-multiple output (MIMO) system has recently attracted significant interest. In this paper, we employ adaptive modulation technique and advanced use of multiple antennas at both the transmitter and receiver to develop four resource allocation schemes. The first scheme assigns subcarrier to the user with best channel gain and employs spatial multiplexing (SM) on the MIMO system to further enhance the throughput. The space-division multiple-access (SDMA) scheme assigns single subcarrier simultaneously to the terminals with pairwise “nearly orthogonal” spatial signatures. In the third scheme, we propose to design the transmit beamformers based on the zero-forcing (ZF) criterion such that the multiuser interference (MUI) is completely removed. Specifically, we propose a low-complexity iterated terminals-selection algorithm in conjunction with   the ZF criterion such that the selected ZF (SZF) scheme can be exploited to achieve throughput multiplication. Alternatively, we propose a least-squares (LS) based multiuser resource allocation algorithm to cope with the over-determined system such that all users are allowed to share single subcarrier.