Sub-channel allocation in multi-user MIMO-OFDMA communication system

Orthogonal frequency division multiple access (OFDMA) has been used for broadband wireless multiple access. The performance of OFDMA system can be improved by using multiple antennas with space time coding to get transmit and receive diversity. Channel information estimated at receiver for space time decoding can be used for sub-channels allocation at transmitter. In this paper, we propose a method to allocate the sub-carriers of mobile user at base station based on sub-channels gain. Data of each user is modulated on a set of sub-carriers in order to get maximum sub-channel gain. The simulation results show that system with proposed sub-channel allocation is always better than system without allocation. Compare to SISO system, BER performance of sub-channel allocated system can improve 7.9 dB SNR and 13.7 dB SNR with MISO and MIMO, respectively.