Proportional-fair bit and power adaptation in multiuser OFDM systems

In this paper, we investigate efficient and linear bit and power allocation algorithms with proportional fairness among users in downlink OFDM transmission. The objective is to minimize the total transmit power while satisfying the rate requirement and BER constraint of each user. To relieve heavy computational burden, bit loading and power allocation is performed after subcarrier allocation. Proportional constraints are employed in terms of rate ratios to assure each user to achieve the target data rate. Comparison through computer simulation indicates that our approach results in an efficient assignment of transmit power in terms of the energy required of transmitting each bit of information. It is also shown that with proportional constraints the capacity is distributed more fairly and rationally among users.