Study On Joint Frequency And Phase Modulation Technique In Long Range Underwater Acoustic Communication

Narrow available bandwidth, strong multipath disturbance and serious fading in the long-range underwater acoustic channel are main obstacles in the high speed reliable underwater acoustic communication. So this is a difficulty in the world that how to make the communication performance well in such underwater environment. Joint frequency and phase modulation (JFPM) utilize frequency and phase information to realize higher efficiency in the frequency and power. Self-Differential JFDM modulation (SD-JFPM) applying to this channel is presented by deeply investigating in the theory of JFDM, later with the lake experiments. It is resulted the method is available and the principle is feasible since that there are many advantages in the technique of SD-JFPM such as high utilization of bandwidth, far communication distance, better resistance to multipath disturbance, which can meet well in the high speed middle and long range underwater acoustic channel. Research work and achievements that had done in the thesis are summarized as follows.1. A method of Self-Differential Joint Frequency and Phase Modulation is presented for the long-range underwater acoustic communication, based on the study of JFPM technique. It is showed that the method of SD-JFPM resists much more effectively than JFPM the multipath influence in a fading channel. So SD-JFPM is more suitable in application of long-range underwater acoustic communication.2. A phase demodulation method based on the spectrum and energy detection is put forward, which can overcome the influence of the synchronous deviation, Doppler, and multipath effect. Simulation results illustrate that the phase information can be accurately demodulated by this method when the SNR equals to OdB with the Doppler coefficient 0.0022, and the synchronous deviation is 10% of the symbol interval.3. A frequency demodulation method based on phase compensation is proposed for SD-JFPM. In this method, the estimation of modulated phase is utilized for phase compensation, and then the frequency is demodulated by frequency estimation. Experimental results make it clear that the BER of frequency demodulation is decreased from 4.1% to 0.65% by using phase compensation when the communica-...