Wavelet Packet Multicarrier-Frequency Hopping Communication System With Multiocode

Wavelet packet modulation(WPM),as one of the multi-carrier modulation new technique,with characteristics of good flexibility,high security and multi-rate transmission,it has an excellent anti inter carrier interference(ICI)and anti inter symbol interference(ISI)by utilizing self-orthogonal translation and mutual orthogonality of wavelet packet basis functions.This thesis studies the theoretical knowledge of wavelet transform and wavelet packet transform,the advantages and disadvantages of the traditional multi-carrier communication system(OFDM)based on the Fourier transform and the new multi-carrier communication(WPM)based on wavelet packet transform also are analyzed and summarized in terms of bandwidth efficiency and anti-jamming capability.Since frequncy hopping(FH)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 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 main work and research results of the thesis as follow:1.Mixing the wavelet packet modulation technique,MQAM,and frequency hopping technique in a reasonable way,a wavelet packet modulation-frequency hopping system based on MQAM(MQAM-WPM-FH)was investigated.The bit error rate(BER)performance of the MQAM-WPM-FH system was derived in additive white Gaussian noise(AWGN)by using the relationship between M-ary amplitude shift keying(MASK)and MQAM.The effects of the length of the wavelet filters and wavelet packet tree on the system were analysized.Theoretical and simulations results show that the WPM-FH system has better spectrum utilization and BER performance than the MQAM-OFDM-FH,and significant multiple access interference(MAI)reduction of MQAM-WPM-FH can be achieved for a fixed system bandwidth by increasing the number of modulation QAM constellation points M and the length L of the filters using in WPM;Though different wavelet packet trees have only a small effect on the BER performance of the system,the system has better security because of the diversity of WPM.2.Combintion multicode(MCD)with wavelet packet modulation(WPM)technology and frequency hopping(FH)technology together,an efficient communication system is studied,namely wavelet packet based multicode multicarrier frequency hopping(WP-MCD/MC-FH)system.The bit error rate(BER)performance of the system was derived over Nakagami-m fading channel and the relationship between the number of users,the length of the wavelet filters,different wavelet packet families,the number of hopping points.Theoretical analysis and simulation results show that the BER performance of the system can effectively improved by increasing the length of wavelet packet filters;the system can not only provide better system security,but also significant multiple access interference(MAI)reduction can be achieved,while different wavelet packet families have small effect on the system performance.