Application In Troposcatter Communication Of Single-Carrier Frequency Domain Equalization Technology

Large capacity troposcatter communication not only plays an important role in the military communications, but also has great potential in other aspects. With the increase of bandwidth and data transmission rate, the influence of delay time of multi-path of channel is becoming more and more prominent. The typical delay spread is withen a width from several symbols to dozens of symbols. In this range, the frequency selective fading appears to be more and more serious along with the delay’s increasing. In this case, the traditional time domain equalizer needs a lot of taps, which result in rather high complexity of its implementation and low convergence speed. The OFDM technique has some advantages such as good anti-fading capability, high spectrum efficiency and low complexity, but it also has some disadvantages such as high peak-to-average power ratio(PAPR) of its signal and its sensitivity to time offset and carrier synchronous, so that OFDM technique is not the best one for troposcatter communication whose transmission power is severe limited.Basing on the consideration of a large capacity troposcatter communication system, this thesis researches on SC-FDE technique so as to obtain an effective method to antagonize serious multi-path fading, moreover, it should has some advantages such as low PAPR, easy to realize and good performance.Firstly, the thesis introduces the principle and transmission characteristics of troposcatter communication channel, including radiate loss, multi-path fading (fast fading and slow fading), and available bandwidth; and builds up a troposcatter channel simulation model basing on theoretical analysis. Secondly, aiming at some key techniques of SC-FDE system, the author has finished some simulations, including code timing synchronization, channel estimation, and frequency domain equalization, FDE combined with diversity reception.In this thesis, a SC-FDE system MODEM scheme which can antagonize the multi-path-fading of more than20symbols is proposed according to characteristics of troposcatter communication, moreover its simulation and hardware implementation results are given, which should be the first time interiorly in China.Finally, with the help of SR5500channel simulator made in SPIRENT company, performance test for the SC-FDE MODEM under the condition of AWGN channel and troposcatter channel are performed. The test result indicates two conclusions as follow. Firstly, the BER performance of SC-FDE MODEM can effectively overcome serious multi-path fading(25symbols in the test). Secondly, the actual test result is in accord with the simulation result and theoretical analysis.The hardware realization and test result also show that SC-FDE technique is an effective and realizable in high data rate troposcatter communication. Furthermore, SC-FDE technology can combine with MIMO and space-time coding to further increase the data transmission rate and improve the performance of system, which would be impossible for time domain equalization. Therefore SC-FDE is a promising for applications of the high data rate troposcatter communication.