Power control, dynamic subchannel allocation and adaptive modulation for multiuser OFDM systems

A new scheme to control the transmission power, allocate subcarriers, and choose modulation schemes for each mobile terminal in a multiuser OFDM system is proposed in this paper. This scheme will make OFDM systems more flexible and more robust to the channel variation along time. We divide the problem into two stages. In the first stage, we maximize the minimum signal-to-noise ratio (SNR) of subchannels subject two constraints. The total system performance can be maintained to an acceptable level in this stage. In the second stage, based on the result of the first stage, we choose the modulation schemes of subchannels of each mobile terminal in the hope that the total transmission rate can be maximized and the performance requirement of each mobile terminal can be satisfied. Simulations are conducted under a different total number of mobile terminals and a different SER (symbol error rate) requirements. Simulation results show that the proposed scheme works well under the simulated environments.