吴群, 周晓, 王成优. OFDM系统中基于最优阈值ACE的PAPR抑制[J]. 工程科学学报, 2023, 45(1): 150-157. DOI: 10.13374/j.issn2095-9389.2021.06.15.001
引用本文: 吴群, 周晓, 王成优. OFDM系统中基于最优阈值ACE的PAPR抑制[J]. 工程科学学报, 2023, 45(1): 150-157. DOI: 10.13374/j.issn2095-9389.2021.06.15.001
WU Qun, ZHOU Xiao, WANG Cheng-you. PAPR reduction based on optimal threshold ACE in OFDM system[J]. Chinese Journal of Engineering, 2023, 45(1): 150-157. DOI: 10.13374/j.issn2095-9389.2021.06.15.001
Citation: WU Qun, ZHOU Xiao, WANG Cheng-you. PAPR reduction based on optimal threshold ACE in OFDM system[J]. Chinese Journal of Engineering, 2023, 45(1): 150-157. DOI: 10.13374/j.issn2095-9389.2021.06.15.001

OFDM系统中基于最优阈值ACE的PAPR抑制

PAPR reduction based on optimal threshold ACE in OFDM system

  • 摘要: 动态星座图扩展(Active constellation extension, ACE)是一种能够有效降低正交频分复用(Orthogonal frequency division multiplexing, OFDM)系统峰均功率比(Peak-to-average power ratio, PAPR)的方法,为解决现有ACE算法因选择固定限幅阈值而限制降低PAPR效果的问题,提出一种最优阈值ACE(Optimal threshold ACE, OTACE)算法,该算法能在每次迭代时根据信号功率求得最合适的限幅阈值,从而增强抑制PAPR的效果。通过数据拟合得到合适的迭代次数,在此基础上对OTACE算法抑制PAPR的效果进行了仿真分析,仿真结果表明,与凸集映射(Projection onto convex sets, POCS)和智能梯度投影(Smart gradient projection, SGP)算法相比,OTACE分别能提高5 dB和3 dB左右的PAPR增益。在广电1、广电6和巴西A三种信道下,分别在多普勒频移为20 Hz和60 Hz时测试OTACE算法对系统误码率(Bit error rate, BER)的影响。实验结果显示,采用OTACE可提高系统的BER性能,并且与POCS相比,OTACE可提高1 dB左右的信噪比(Signal-to-noise ratio, SNR)增益;与SGP相比,OTACE在高SNR时有明显的优势。

     

    Abstract: Orthogonal frequency division multiplexing (OFDM) technology, which can divide the frequency selective fading channel into multiple flat fading sub-channels, is widely used in wireless communication systems because of its robustness to frequency selectivity in wireless channels and the ability to mitigate multipath fading that causes inter-symbol interference. Therefore, it has become one of the key technologies of 5G mobile communication. However, it has a serious shortcoming, i.e., the high peak-to-average power ratio (PAPR), especially when the number of subcarriers is large. High PAPR will make the high-power amplifier work in its nonlinear region, leading to inter-modulation interference among subcarriers and out-of-band interference of OFDM signals. Active constellation extension (ACE) reduces the PAPR of OFDM signals effectively by extending external constellation points outwards. Most of the ACE algorithms currently used set a fixed threshold to limit the amplitude of the OFDM signal during the iteration. As the statistical characteristics of OFDM signals will change after each iteration, the same threshold will reduce the ability of the method to suppress the PAPR of OFDM systems. To solve this problem, an optimal threshold ACE (OTACE) method is proposed, which can determine an appropriate threshold according to the signal power at each iteration to enhance the performance of PAPR reduction. The appropriate number of iterations is obtained by data fitting, and on this basis, the impact of the OTACE algorithm in suppressing the PAPR is simulated and analyzed. The simulation results demonstrate that compared with POCS and SGP, OTACE can increase the performance to reduce PAPR by approximately 5 dB and 3 dB gains, respectively. Under the CDT 1, CDT 6, and Brazil A channels, the impact of the OTACE algorithm on the bit error rate (BER) is tested when the Doppler frequency shift is 20 Hz and 60 Hz, respectively. The experimental results show that the OTACE can achieve better BER performance. Compared with POCS, OTACE has about 1 dB signal-to-noise ratio (SNR) gain in BER performance. OTACE has obvious advantages over SGP at a high SNR.

     

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