Research On Power Efficient Algorithm For OFDM Systems With Nonlinear Distortion

With the explosive development of wireless communication technology, more and more portable devices appear in everyday life.The power consumption of these devices is gradually becoming a great concern in the world. Since Orthogonal Frequency DivisionMultiplexing technology can not only improving the spectrum utilization,but also has better performance in frequency selective fading channel, which makes it becomes the core technology of next generation mobile communication system.The energy saving for OFDM systems is of great significance for green communication industry. For the high peak to average ratio of OFDM signal and the nonlinear characteristics of nonlinear high power amplifier will inevitably produce nonlinear distortion in OFDM systems. This paper mainly research on power efficient algorithm for OFDM systems with nonlinear distortion.The research in this paper is sponsored by Huawei Technology Foundation "Research on Green Wireless Networks Technology based on Cognitive Radio ". Thepaper first mainly introduce the research related to OFDM system, the nonlinear HPA characteristic and mathematicalmodel and the related research of OFDM system performance with nonlinear distortion.For the existing technologies generally reduce the nonlinear distortion while do not take into account of the efficiency andenergy consumption of the nonlinear HPA, the paperpropose an energy-saving method based on improving the average efficiency of the nonlinear HPA while meeting the bit error rate(BER) requirement of OFDM systemThe energy-saving model is derived by a third-order memoryless polynomial model of nonlinear HPA while combining the system requirement. Moreover, a practical nonlinear HPA transistor (MRF21050), with which average efficiency-input power model is applied to minimize the energy per bit by obtaining the optimal input power and modulation scheme. Numerical results show that the proposed method can save up to50%energy consumption than the adaptive power back off algorithm over both AWGN channel and large-scale fading channel.In order to solve the resource allocation problem of minimizing the transmit power while satisfying the target data rate constraint and BER requirement in OFDM systems with nonlinear distortion, the paper propose a joint bit and power allocation algorithm based on the SINR(Signal-to-Interference Ratio) with different nonlinear distortion power on each subcarrier. The transmit power minimization model in OFDM systems with nonlinear distortion is firstly derived by a third-order memoryless polynomial model of non-linear HPA while combining the system requirement. Then a suboptimal joint bit and power allocation algorithm is proposed to solve the optimization problem. Numerical results show thatit makes the loss of the power for0.6dB at most and the running time reduction by42%while compared with the optimal algorithm, and it is proved to be a practical and fast resource allocation algorithm in OFDM systems with nonlinear distortion.