Design Of Rate-Adaptive Laser Wireless Communication System

Compared with optical fiber communication and microwave communication,the laser wireless communication has the advantages of strong confidentiality and flexible networking.It has significant advantages and high research value in the application scenarios where it is not convenient to lay optical fiber such as river crossing or seas crossing.At present,laser wireless communication technology has been developed rapidly,and related products can be used in satellite communication,military applications and other scenarios.However,there are still some technical difficulties for the miniaturized industrial optical terminal equipment.Two of the most important problems are: how to realize the rapid acquisition and alignment of the optical path in the process of system construction,and how to ensure the continuous stability of communication under the influence of turbulence in the atmospheric channel quality.In order to solve the above problems,this paper designs a set of hardware equipment of point-to-point laser wireless communication terminal with FPGA as the control core,and makes innovation and improvement in software algorithm.On the one hand,a fast raster scanning algorithm is proposed to solve the problem of fast alignment of optical path;on the other hand,an adaptive adjustment algorithm of communication rate is designed by means of error rate detection of atmospheric channel,which enables the system communication rate can be adaptively adjusted according to the channel quality,so as to realize uninterrupted communication.This paper mainly includes the following aspects:1.A high-precision optical power data monitoring circuit is designed,and a fast grating scanning method for capturing and aligning is proposed.The system can realize the optical power data detection with the range of-50 dbm ? 0dbm and the accuracy of 0.1dbm.The driving control circuit of the two-dimensional electric platform is built,and the comparison experiment shows that the fast grating scanning method has better effect than the traditional scanning method in capturing alignment,the alignment speed is increased by 10.1% ? 29.8%,and the average alignment power value is increased by 3.1dbm.2.A multi rate compatible point-to-point laser wireless communication system based on Ethernet is designed.Based on the physical chip and IP core of data link layer,the Ethernet data interaction circuit is designed.The system can interact with 10 Mbps,100Mbps and 1000 Mbps three speed Ethernet adaptively.The multi rate compatible laser transmitting circuit and receiving circuit are designed,which can realize any rate communication within 50 Mbps ?622Mbps.3.Taking the error rate of communication as the criterion of atmospheric channel quality,an adaptive adjustment algorithm of laser communication rate is designed.A special pseudorandom sequence is inserted into the transmitter to change the format of the transmitted data frame.The receiver extracts the sequence and detects the error code and sets the decision threshold at the level of the error rate.The adaptive switching of the communication rates of50 Mbps,100Mbps,200 Mbps and 622 Mbps is realized.The system can automatically adjust the communication rate to the optimal value according to the algorithm,so as to ensure the uninterrupted communication and the highest utilization of channel bandwidth.