猝发混合扩频水声隐蔽通信技术

针对常规的连续载波调制扩频通信方式容易通过能量检测的方法被截获的问题,提出了一种猝发的混合扩频水声隐蔽通信方式,该方法通过在时间上随机的发送脉冲混合调制扩频信号来降低截获概率,而且可以比较灵活的通过调整平均占空比来满足不同隐蔽性的要求,但是该隐蔽性是以牺牲通信速率为代价的。猝发信号中混合了二进制相位键控(BPSK)、循环移位键控(CSK)和多进制频移键控(MFSK)扩频调制方式,采用自同步和时频二维搜索算法实现码元和载波同步。通过仿真分析了猝发通信系统的隐蔽性能和多途信道下的误码性能,并且通过了南海海试验证了算法的性能,在5 km的通信距离上,4 kHz的带宽内,单个脉冲信号的通信速率可以达到317 bps,误码率达到10-3以下。 

Burst mode spread spectrum technology for covert underwater acoustic communication

Considering that conventional continuous spread spectrum communication can be intercepted by an energy detector, a burst mode hybrid spread spectrum technology for covert acoustic communications is proposed in this paper. This method randomly transmits pulse hybrid spread spectrum modulation signal in time to reduce the probability of interception. Different interception probabilities can be achieved by adjusting the average duty cycle. However, the data rate is sacrificed. Burst hybrid signal consists of BPSK, CSK, and MFSK spread spectrum modulated schemes. Self-synchronization and time-frequency two-dimensional search algorithm are used to synchronize the chip and carrier. The interception probability and bit-error-rate (BER) performance over multipath channel are analyzed in the simulation and validated by South Sea experiments. The experiment results showed that the data rate of one pulse can be up to 317 bps with BER under 10-3 in the distance of 5 km, over the bandwidth of 4 kHz.