正交M-ary/DS扩频及其在水声远程通信中的应用

在水声通信中,扩频通信具有可靠性高、抗多径能力强等特点,适合于远程或低信噪比情况下的通信;但另一方面,由于其带宽利用率低加之水声信道带宽有限,通信系统的数据率将受到很大的限制。为了提高数据率,提出了一种正交M-ary/DS扩频方法,该方法将正交直接序列(DS)扩频与并行M-ary扩频结合在一起,能够显著提高水声通信系统的数据率与带宽利用率。经过湖上实验验证,该方法在25 km距离约0 dB的接收信噪比下,采用63、127长度G o ld序列并通过RAKE接收,分别实现了对480个符号的无误码传输,数据率为381.0 b its/s与220.5 b its/s,其带宽利用率与使用相同序列的直接序列扩频相比提高了约一个数量级。

Improving Bit Rate of Long-Range Underwater Communication with Orthogonal M-ary/DS Spread Spectrum

Purpose.Spread spectrum is suitable for long-range or low-SNR underwater acoustic communication.But the low bandwidth efficiency of spread spectrum and limited underwater channel bandwidth cause low bit rates.So we propose the method of orthogonal M-ary/DS spread spectrum to improve bandwidth efficiency and bit rates;this method is a combination of orthogonal direct sequence(DS) spread spectrum and parallel M-ary spread spectrum.In the full paper,we explain in detail the above-mentioned method;in this abstract,we just list the two topics of our explanation:(A) introduction to orthogonal M-ary/DS spread spectrum; on the basis of well-known principles,we construct Figs.1 and 2 in the full paper,which we believe can be very useful for understanding our method;(B) introduction to RAKE receiver.Experimental results in a lake,shown in Figs.5,6,and 7 in the full paper,show that,by use of Gold sequences of 63 and 127 lengths,the orthogonal M-ary/DS spread spectrum system achieved error-free communication of 480 symbols at 25 km and 0 dB SNR with RAKE receiver;the bit rates were up to 381.0 bits/s and 220.5 bits/s.In comparison with direct sequence spread spectrum using same sequences,the bandwidth efficiency of the new method increases by about an order of magnitude.