| In the case of the loss of regular short-wave communications, the completion of a minimum short-wave communications is of great significance. Therefore, according to the characteristics of short-wave channel and low SNR channel conditions, a lower transmission rate but higher reliability of emergency communication system is designed in this paper.In this paper, a processing gain is brought by the multi-ary orthogonal codes spread spectrum technology, which reduces the signal to noise ratio requirement effectively; RS code channel coding which is compared with the BCH code combined with interleaving techniques has shown an obvious advantage; To solve the problem of excessive acquisition time, the sub-FFT technique is introduced in system significantly to increase capture speed; Multi-path estimation and RAKE receiver technology is added to improve the system of anti-multipath fading performance. In addition, the cyclic redundancy check code is used by the receiver for error detection information.The system design is verified through the MATLAB software simulation. The result indicates that the system can effectively overcome the low signal to noise ratio, fading, multipath and other short-wave channel interference, thus achieve a very low rate (50 bytes / min) and effective transmission of information. |
