Theory And Method Of Wireless Communication Based On Hybrid System

Chaos is a kind of stochastic behavior of deterministic system,which h as the charanterist-ics of wide bandwidth,sensitive initial value and good confidentiality.It has been widely used in secure communication based on chaotic synchronization.However,there are still many problems when chaos is used in wireless communication.1)The traditional commnunication mode base on chaotic carrier has low frequency band,which is not suitable for high-frequency wireless transmission,and cannot be compatible with the traditional communication equipment based on sinusoidal carrier.2)Most of the existing chaotic systems have broadband characteristics.For wireless communications with valuable spectrum resourtces,how to improve the spectral efficiency is a problem to be solved.3)Inter-symbol interference(ISI)caused by multipath propagation greatly reduces the quality of wireless communication in complex wireless channels.In summary,there are still many challenges m the application of chaos to wireless communication systems,and it is still in the stage of solving practical problems.With the emergence of syraboeic dynamic modulation in incoherent chaotic communication,scholars have studiedd the hybrid systen proposed by Corron et al,and found new characteristics of chaos in wireless communication field:1)In atlditive white Gaussian noise channel,chaos has been proved to the best coherent communication waveform.It has a very simple matched fiter to maximize the outpht signal-to-noise ratio;2)In wireless channels,it has been proved that multipath propagation does not affect the Lyapunov exponential spectrum of chaotic signals;3)Using the shift mapping property of the chaotic signal,the intersymbol interference generated by multipath tapped fading channels can be suppressed;4)The chaotic signals and symbol sequences passing through the wireless channel aretopologically conjugate,and the BER performance of the system can be improved by judging the optimal threshold symbols.The above research lays a foundation for the application of chaos in wireless cnmtnunicatiSion,It shows that this hybrid system can be used to build a reliable and efficient wireless communication system.Although symbolic dynamic modulation has greatly improved the BER performance and bandwidth utilization of traditional coherent chaotic communication and non-coherent keying communication,and simplified the hardware implementation difficulty,there are still many theoretical and practical difficulties to be solved in wireless communication based on this hybrid system:how to be compatible with traditional wireless communication systems,how to use chaotic characteristics to improve radio spectrum utilization and reduce communication error rate,etc.Based on the hybrid system,this paper designs an efficient and practical chaotic wireless communication system,studies non-orthogonal chaotic coding and decoding algorithm and chaos division multiple access technology.Main tasks:(1)chaotic wireless communication system design.The basic framework of chaotic wireless communication system is introduced,and its information coding method,matched filtering method and information decoding method are studied;To compatible with the traditional wireless communication system,the system realization method based on software radio,baseband chaotic waveforms is put forward on the cosine carrier of thought,design based on finite impulse response(FIR)filter information coding and matched filtering process,and use of rice university research and development of WRAP software radio platform,seting a mixed system of wireless communication system experiment platform.(2)efficient encoding and decoding technology based on chaotic basis function.By analyzing the orthogonality of the basis function of the hybrid system,an orthogonal filter is proposed to distinguish the multichannel signals.At the sending end,different chaotic basis functions are used to shape and filter the multi-channel signals,and then the non-orthogonal sum value is sent.At the receiving end,the corresponding matched filter set and orthogonal filter set are used for filtering and information decoding.Then,the bit error rate,throughout and throughoutper frequency of the proposed method are theoretically analyzed and experimentally verified.(3)Chaos division multiple access technology based on chaotic basis function.By extending each signal in the efficient coding algorithm to each user,the concept of chaos multiple access is proposed.By analyzing the frequency band widths of chaotic signals with different number of users,it is proved that chaos division multiple access has higher frequency band utilization ratio than traditional code division multiple access,time division multiple access and frequency division multiple access.The performance of the proposed chaotic multiple access technology is analyzed and simulated.