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为了有效抑制正交频分复用(OFDM)系统中信号的峰均比(PAPR),提出了一种基于平方根Better-Than奈奎斯特脉冲的改进预编码方案,通过仿真在60GHz光载无线通信(RoF)系统中实现5Gb/s四阶正交振幅调制(4QAM)OFDM预编码信号的发射、传输与接收。仿真结果显示,与基于平方根升余弦脉冲的预编码算法相比,改进算法将进一步获得0.3dB左右的PAPR抑制增益。从平衡传输效率与PAPR抑制性能的角度考虑,由预编码引入的冗余度上限取20%为宜。采用改进的预编码算法,信号的峰均比最大值具有不随OFDM系统子载波数增加而明显增加的特性。无论是在背对背或传输情况下,系统的接收灵敏度均随改进型预编码算法的引入获得约0.4dBm的改善。如需进一步改进系统误码率特性,可考虑采用高阶调制格式。综合考虑,改进型预编码方案将有效改善传统OFDM-RoF系统的性能并适用于未来的实际应用。
In order to effectively suppress the PAPR of OFDM signals, an improved precoding scheme based on the square root Better-Than Nyquist pulses is proposed, Communication (RoF) system to achieve 5Gb / s fourth-order Quadrature Amplitude Modulation (4QAM) OFDM precoded signal transmission, transmission and reception. The simulation results show that compared with the pre-coding algorithm based on the square root raised cosine pulse, the improved algorithm will further achieve PAPR suppression gain of about 0.3dB. From the perspective of balanced transmission efficiency and PAPR suppression performance, the upper limit of redundancy introduced by precoding is preferably 20%. With the improved precoding algorithm, the peak-to-average ratio of the signal is not significantly increased with the increase of the number of OFDM subcarriers. Receiving system sensitivity improves with about 0.4dBm with the introduction of improved precoding algorithms, either back-to-back or transmitted. If you want to further improve the system BER characteristics, consider the use of high-end modulation format. Taken together, the improved precoding scheme will effectively improve the performance of the traditional OFDM-RoF system and suitable for future practical applications.