Power control, adaptive modulation and subchannel allocation for multiuser downlink OFDM

A scheme to control transmission power, allocate subcarriers, and choose modulation schemes for each mobile terminal (MT) in a multiuser downlink OFDM system is investigated in this work. This proposed scheme attempts to make OFDM systems more flexible and robust to channel variations. The problem is decomposed into two stages. In the first stage, the min-max criterion is used to control the transmission power among different MTs in different allocated subchannels. Then, in the second stage, we choose modulation schemes for allocated subchannels of each MT with an objective to maximize the total transmission rate while satisfying the performance requirement of each MT. Simulations are conducted to demonstrate the performance of the proposed scheme under a varying number of MTs and a range of symbol error rates (SERs).