改进型正交多用户降噪差分混沌键控通信系统

针对差分混沌移位键控(differential chaos shift keying, DCSK)系统传输速率低和误码率(bit error rate, BER)性能差的缺点，提出一种改进型正交多用户降噪DCSK(improved orthogonal multiuser noise reduction DCSK, IOMU-NR-DCSK)通信系统。发送端将长为R的混沌序列复制P次作为参考信号，然后再扩展两路，通过希尔伯特变换使每路多传输N bit用户信息，并结合正交调制传输经Walsh码调制后的信息信号。接收端利用滑动平均滤波器对信号进行平均操作来降低噪声方差。在加性高斯白噪声(additive white Gaussian noise, AWGN)信道和多径Rayleigh衰落信道下推导了IOMU-NR-DCSK系统的BER公式并进行仿真分析。结果表明，在相同条件下该系统的数据传输速率比多用户DCSK(multiuser DCSK based on Hilbert transform, HMU-DCSK)系统提升了约50%,BER性能提高了近2 dB。

Improved orthogonal multiuser noise reduction differential chaos shift keying communication system

The major drawbacks of differential chaos shift keying (DCSK) system are related to low transmission rate and poor bit error rate (BER) performance. Therefore, an improved orthogonal multiuser noise reduction DCSK (IOMU-NR-DCSK) communication system is proposed to improve the performance of the DCSK system. At the transmitter, the reference signal is obtained by duplicating R-length chaotic sequence P times, and then expanded to two channels. Each channel additionally transmits N bit users' information by using the Hilbert transform. The information signals modulated by Walsh codes are transmitted through orthogonal modulation. At the demodulator, a moving average filter is used to measure the mean of the signal by reducing the noise variance. The BER formula for the IOMU-NR-DCSK system is derived under the additive white Gaussian noise (AWGN) channel and the multipath Rayleigh fading channel, and simulation is used for verification. Compared with the multiuser DCSK based on Hilbert transform (HMU-DCSK) system, the results show that the data transmission rate of the proposed system increases by about 50% and BER performance improves by nearly 2 dB.