M元扩频OFDM水声通信新方法

New Spread Spectrum OFDM Method for Underwater Acoustic Communication (UAC)

扩频水声通信能够抗信道衰落、多径干扰,具有传输距离远、可靠性高、被截获性低的优点。然而,水声通信可用带宽很窄,导致其数据率低。文章在伪随机序列扩频水声通信和OFDM水声通信研究及湖上成功实验的基础上,提出了一种基于M元伪随机序列组和OFDM技术的新型扩频OFDM(MSS-OFDM)水声通信方法。该方法能使得扩频水声通信数据率提高2.(log2M).(log2Q)倍。从理论上分析了M元扩频OFDM在高斯白噪声信道(AWGN)下的误码率性能,并通过仿真验证了其较强的稳健性。利用湖试测量得到的多径信道参数模型,分析比较了OFDM、SS-OFDM以及MSS-OFDM的水声通信误码率性能,结果表明:M元扩频OFDM具有双重抗多径干扰的优点,即使在没有保护间隔的情况下,也能获得较好的通信效果;由于采用了伪随机序列组,该方法也可用于水声网络通信。

Aim. The full paper starts with a review of relevant papers^[1-7] concerning raising data rate and lowering bit error rate （BER） of spread spectrum UAC. We now propose a new method, called by us MSS-OFDM（M-ary Spread Spectrum OFDM）, that is, we believe, better. In the full paper, we explain our new method in detail; in this abstract, we just list the three topics of explanation and add some pertinent remarks. The first topic is： spread spectrum OFDM. The second topic is： MSS-OFDM. In topic 2, thinking again and again over our successful lake tests respectively of spread spectrum UAC and OFDM UAC, we give the outline of MSS-OFDM. Also in topic 2, we implement the parallel transmission of spread spectrum by using OFDM in our MSS-OFDM method. Still in topic 2, eq. （6） in the full paper can be used to calculate the data rate, which is raised by our MSS-OFDM method. Topic 3 is ： the performance analysis of BER. In topic 3, the BER equation of MSS-OFDM in AWGN （additive white Gaussian noise） channel is derived by us as eq. （9） in the full paper. Also in topic 3, computer simulation results agree fairly well with those computed with eq. （9）. Still in topic 3, computer simulation results using multi-path channel model based on lake test data show preliminarily that MSS-OFDM has double anti-muhipath capability. Finally, to sum up, MSS-OFDM can significantly improve the data rate of spread spectrum UAC with a robust BER performance even without cycle prefix.