Research On Performance Of Wavelet Packet Frequency Hopping System

Wavelet packet modulation(WPM), as one of the multi-carrier modulation technique, with characteristics of good flexibility, high security and multi-rate transmission, utilizing self-orthogonal translation and mutual orthogonality of wavelet packet basis functions, so the WPM system has an excellent anti inter carrier interference and anti inter symbol interference. Howere, the problem of high peak to average power ratio(PAPR) exists in WPM system as well as in other multi-carrier modulation techniques. And the performance of WPM system can be enhanced by reducing the PAPR. As a key part of wireless communication system, the design and improvement for multi-carrier modulation technique is of great significant. In order to make further improvement of anti-jamming and fading resistance for the wireless communication system, the performance of frequency hopping system based on wavelet packet modulation is studied in this paper under different channel enviroment. The contribution of the paper is mainly as follows:1. On the basis of analyzing the structures and characteristics of wavelet packet modulation, combing the the features of WPM system with the principle of selected mapping(SLM) algorithm. The method that based on Riemann sequence is discussed to cut down the PAPR in wavelet packet modulation system. According to the characteristics of hierarchical modulation in Wavelet Packet Modulation system, the main idea of the algorithm is to achieve multi-level transmission scrambling sequence with Riemann sequence's hierarchical disrupting, which can weak the autocorrelation of transmission sequence, so that the Peak-to-Average Power Ratio in the system is reduced. The simulation results show that the algorithm helps to improve the WPM system PAPR with a lower complexity, and save the bandwidth at the same time.2. Frequncy hopping communications can provide reliable transmission with advantages of frequency hopping, concealed, narrowband anti-interference and easiness combination with other modulation techniques, etc. In this thesis, a new type of communication system is investigated through mixing the wavelet packet modulation technique and frequency hopping technique in a reasonable way, i.e. wavelet packet modulation-frequency hopping system (WPM-FH). The performance of system bit error rate(BER) is analyzed and deduced respectively over AWGN channel and Rayleigh fading channel by means of characteristic functions. The number of users, the number of frequency points and the number of sub carriers are mainly considered that has some relationship with the system BER. The theory analysis and simulation results indicate that the system keeps the advantages of wavelet packet modulation technique as well as improves the spectrum efficient. What's more, the system has a better ability of resistance to multipath fading and anti-interference under this scheme, so the performance of the communication system is improved well.