Analysis of perfect and practical multiuser diversity on MIMO-OFDM system

In order to provide the instruction in theory to design the practical multiuser MIMO-OFDM system, the performance gain concerning multiuser diversity with the perfect feedback is studied. A quantization feedback scheme is proposed by quantized values indicating the modulation level instead of the full values of the SNRs when a finite set of M-ary quadrature amplitude modulation (M-QAM) constellations are adopted. The closed-form expressions of the average transmission rate and the average bit-errors ratio (BER) are deduced. The optimal quantization thresholds maximize the average transmission rate subject to the average BER constraint. To obtain a certain degree of fairness among the user. A fair subcarrier-assigning strategy is considered. Simulation results are used to evaluate the gain of multiuser diversity to the spectrum efficiency in two case of the perfect feedback and the proposed quantization feedback.