Abstract: This paper proposes a PAPR reduction algorithm for OFDM systems with adaptive modulation, which is based on the fact that an OFDM symbol has different PAPR when its modulation type is changed, and designs an OFDM system. A group of modulation type is set to be the candidate and the OFDM symbol’s modulation type is changed according to the group. The one with the minimal peak power is selected as the output signal. In receiver, the information bit can be demodulated after the modulation type detection. As there is no side information which should be strictly protected, the system is more reliable and robust. Simulation results show that it is effective for PAPR reduction with adaptive modulation in OFDM systems, and the proposed algorithm’s system has better bit error ratio performances than previously algorithms as a whole.

Key words: orthogonal frequency division multiplexing, peak to average power ratio, adaptive modulation, select mapping, modulation type recognition

摘要： 根据相同的信息比特采用不同调制样式时所得的正交频分复用（OFDM）信号的峰均功率比（PAPR）不同，提出了一种利用自适应调制进行OFDM系统PAPR抑制的算法，并设计了利用该算法的OFDM系统。算法通过设定一个可选调制样式集合，改变发端信息比特的调制样式，选择具有最小PAPR值的OFDM信号作为传输的OFDM信号，从而使整个系统的PAPR得到抑制。在接收端，通过对OFDM符号的调制样式进行识别，完成对调制信息解调。由于算法不需要传输需严格保护的边带信息，系统具有较强的可靠性和抗干扰能力。仿真结果表明，利用自适应调制可有效地进行OFDM系统PAPR抑制；同已有算法相比，在多径信道下，利用该算法的OFDM系统的误码率性能总体上较好。

关键词: 正交频分复用, 峰均功率比, 自适应调制, 选择映射, 调制样式识别