Study On Adaptive Frequency Hopping System Based On Periodic NHZ Hopping Code

Band congestion problem is the serious problem in the modern civilian communications.In the frequency-hopping communication,it solves the overcrowding problem that the realization of multi-user shared frequency band. However,with network capacity increasing,near-far effect is more and more serious.In order to meet network performance requirements,it must deal with the issue of multiple access interference in the frequency -hopping communication.It is a self-interference system for Frequency-hopping communication system and interference between the users is more serious.If it happens one collision for 500 jumps,the bit error probability(BER) is 10^-3.It affects the quality of communication and even disrupts the communication for a large amount of information lossing.In the frequency-hopping communications,in order to overcome the multiple access interference(MAI),there has been a number of ways.One way is to research and design practical hopping code with a hamming cross-correlation as low as possible.Other way is to improve the system by technology of eliminate or reduce interference,which includes Adaptive Frequency Hopping(AFH), Correlated Hopping Enhanced Spread Spectrum(CHESS) and so on.This thesis combines of these two ways to improve the performance of anti-MAI.First of all,a No-Hit-Zone(NHZ) hopping code with a low cross-correlation is choosed that only occurrs the frequency collision at a particular displacement of cycle and will not collisions in other displacement of cycle.Then, according to the characteristics of No-Hit-Zone(NHZ) hopping code,we propose the No-Hit-Zone hopping communication system depends on the adaptive frequency hopping thinking.A new adaptive frequency hopping communication system using for NHZ hopping code was studied.The purpose is to do the best to reduce the multiple access interference of system. In this thesis,the author builds the adaptive frequency hopping communication system simulation platform with SIMULINK tool.In the user-defined modules of the adaptive frequency hopping communication system simulation platform,Matlab language is used as the programming tool.In the worse case and normal case,the author does a simulation study with the asynchronous adaptive frequency hopping communication system using for NHZ hopping code and the asynchronous non-adaption frequency hopping communication system using for NHZ hopping code.Simulation results prove that the system that substitutes the period hit frequency of the No-Hit-Zone(NHZ) hopping sequences is better than traditional system.Both in the number of bad channels or the bit error rate,it decreases the Multi-Access interference and improves the integral bit error rate performance of the system.