Research On Generalized Multi-carrier Communication Technology

Underwater acoustic communication is a rapidly developing scientific research field.With the continuous deepening of ocean exploration,people's demand for high-speed underwater acoustic communication systems is increasing.How to realize high-speed,high-capacity and high-reliability communication is the hotspot of underwater acoustic communication research.There are serious frequency selective fading,multipath effects,limited available bandwidth and Doppler spread in the underwater acoustic channel.Realizing high-speed communication in a complex underwater acoustic environment has become a problem to be solved in underwater communication.The frequency division of the traditional multi-carrier system is large,and the frequency band spacing is fixed,resulting in low bandwidth utilization and limiting the transmission speed of underwater communication.To solve this problem,a generalized multi-carrier communication system is proposed in this paper.Firstly,in the system channel pre-estimation is performed and then select different frequency band spacing subcarriers according to different channel communication quality.The division of sub-carriers in the system is more flexible.It can make full use of the limited bandwidth of underwater acoustic channels and improve the transmission rate of transmission information.The main research work in this paper is:(1)An instantaneous stationary signal frequency detection method Integral gain filter is proposed.The frequency of the filter is matched with the frequency of the stationary signal to achieve amplification of the stationary signal energy at a specific frequency.At the same time,random noise and interference noise are suppressed,and weak signal detection with a smaller frequency interval is realized.Based on this frequency detection method,the generalized multi-carrier system can divide sub-carriers with smaller intervals to provide technical support for high-speed communication within a limited bandwidth.(2)A generalized chirplet transform algorithm is proposed.A Frequency-Modulated signal that is insensitive to the Doppler effect is used as a subcarrier of the generalized multi-carrier system.At the receiving end of the system,an exponential function is used to weight-fit the frequency curve of the signal in the time-frequency domain,and the FM signal is changed into a stationary signal,and the target signal is obtained through the Integral gain filter.(3)A generalized multi-carrier communication system is proposed.The system first maps the bit stream of the signal to a coordinate axis,establishes a one-to-one mapping relationship between data and frequency,and forms each sub-carrier through frequency mapping coding.These sub-carriers are orthogonal to each other.At the receiving end,the received signal frequency is demodulated using an the Integral gain filter to obtain the correct target signal.(4)In this paper,the generalized multi-carrier communication system is simulated and verified by sea trials.Experiments show that,within a certain distance,a generalized multi-carrier communication system can achieve reliable high-speed communication.