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文章通过对Logistic映射产生的混沌序列的特性进行定量分析,证明了Logistic映射序列在MC-CDMA系统中能够实现扩频通信的适应性;随后在分析影响MC-CDMA系统信噪比及误码率主要因素的基础上,在MC-CDMA下行链路基于BPSK调制方式,选择m序列、Gold序列、Logistic映射混沌序列分别作为扩频序列进行了实验仿真,揭示了系统误码率随序列长度、用户数、子载波数、信噪比的变化关系。在用户数和序列长度一定的情况下,信噪比在8dB之前,使用三种序列系统的误码率几乎相同,在信噪比为12dB之后Logistic序列误码性能明显优于其它两序列。而在序列长度和系统信噪比一定的情况下,在8个用户之前采用不同扩频序列系统误码率区分不明显,而在8个用户之后,随着用户数的增多,Logistic序列与其它两序列的误码率区分更加清楚。
By quantitatively analyzing the characteristics of chaotic sequences generated by Logistic maps, the article proves the adaptability of Logistic mapping sequence in spread spectrum communication in MC-CDMA systems. Then, after analyzing the influence of signal-to-noise ratio and bit error rate Based on the main factors, based on the BPSK modulation scheme of MC-CDMA downlink, m sequences, Gold sequences and Logistic mapping chaotic sequences are respectively used as the spreading sequences to simulate the experiments. The results show that the system error rate varies with the sequence length, Number, number of subcarriers, signal to noise ratio changes. With a certain number of users and a certain sequence length, the bit error rates of the three sequence systems are almost the same before SNR is 8dB, and Logistic sequence error performance is obviously better than the other two sequences after SNR is 12dB. In the case of certain sequence length and system SNR, the bit error rate of systems using different spreading sequences before 8 users is not obvious, but after 8 users, with the increase of number of users, Logistic sequence and other The bit error rate of two sequences is more clearly distinguished.