Adaptive modulation, power allocation and control for OFDM wireless networks

Orthogonal frequency division multiplexing (OFDM) is a promising multiplexing technique for high data rate transmission over wireless radio channels. In this paper, we consider a low mobility, wireless OFDM cellular system. Since a cellular system uses a frequency reuse concept to enhance the efficiency of spectral utilization, it introduces so called cochannel interference (CCI) which is one of the major sources of performance degradation. To mitigate the effect of CCI while satisfying required quality of service, the power level of each subchannel of the OFDM system should be allocated to and controlled at an optimal value such that the system throughput can be maximized by employing adaptive modulation. Due to the effect of the CCI in the multi-cell OFDM system, the optimal values of power levels are very difficult to find. A new distributed suboptimal power allocation algorithm for the multi-cell OFDM system is proposed to increase the system throughput. Numerical results show the advantages of the proposed algorithm over those of the equal power allocation algorithm in various channel conditions.