Research On Multiple Access Technology Under Interference Environment

With the development of wireless communication,the requirement for communication reliability is increasing,and anti-interference technology constantly becomes more and more important.Anti-interference technology focuses on not only reducing the internal interference,but also on resisting external interference from the environment or malicious users.The communication system needs to resist many kinds of external interference,among which the malicious interference is the most complex,and its influence is even worse because of the intelligence(intellectualization)of signal detection and interference decision.At the same time,the number of electronic devices in the communication environment is increasing rapidly.Therefore,it is necessary to study the technology that can improve the capacity of the communication system under interference environment.Direct sequence spread spectrum(DSSS)technology is widely implied in anti-interference systems due to its excellent anti-interception and anti-narrowband interference performance.Code-hopping multiple access(CHMA)is a technology that can further improve the performance of the CDMA system,where the address codes hop over time.This thesis mainly studies CHMA technology,which bases on DSSS and CDMA.This technology not only maintains the anti-interference performance of DSSS,but also improves its access capability.Firstly,this thesis proposes a series of schemes to improve the bit error performance of CHMA.Since the access collision has a serious impact on the system,this thesis designs a low-collision multi-user code-hopping pattern.Subsequently,by studying the structure of address codes,the performance of CHMA is further improved.Secondly,this thesis studies the performance of CHMA in complex channels,and designs a series of schemes to make the system adapt to the environment.In this thesis,a collision and interference detection algorithm is designed.Subsequently,this thesis proposes adaptive algorithms based on Q-learning,which updates code-hopping patterns by detecting multipath channels and interference.Finally,this thesis summarizes the related work and gives an outlook on the future research.