Research And Implementation Of HF Data Transmission System At Extreme Low Rate

The HF extreme low rate communication, under the conditions of very strong noise, is a emergency communication, which is used to transmit very simple information when normal communications are halted in battlefield.The date transmission scheme is based on DS_BPSK, works under the conditions of SNR = ?10 dB~?20dB. According to SNR,there are four data transmission velocities to be chosen. BCH coding and helix interleaving are used to correct random and burst errors, raised cosine pulse shape filter is adopted to restrict the signal’s spectrum to the voice bandwidth and avoid intersymbol interference. It is a difficult problem how to suppress high power narrow-band interference in the HF extreme low rate communication system. The predigested LMS algorithm can suppress high power narrow-band interference effectively in frequency domain in the HF extreme low rate spread spectrum communication system. This is introduced in the segment of key technique and the simulation result in MATLAB is given. Correlation-FFT technique is employed to realize acquisition under the condition of extreme low SNR and the big frequency differences between the emitter and the receiver. Soft decision scheme is used to realize exact synchronization, which reduces the probability of false synchronization and leak synchronization.Finally, the receiveing transmission system is realized on SEED-DEC6713 audio frequency hardware platform made by seed electronic technology corporation which contains TMS320C6713 which is a float-point DSP. Also the data transmission system is tested by HF channel simulator. The system can work under the condition which contains white gauss noise and high power narrow-band interference.