Research On Adaptive Differential Chaos Shift Keying Modulation Technology

Chaotic signal has good characteristics such as wide spectrum,low power consumption and so on,so chaotic modulation with chaotic signal as carrier can be used as a kind of candidate modulation technology in Ultra-Wideband(UWB)communication.Chaotic UWB technology has considerable prospects in powerconstrained systems,e.g.Wireless Body Area Networks(WBANs).Therefore,it is of great significance to study chaotic UWB communication.This paper aims to improve the communication performance of digital chaotic modulation,including improving reliability and spectrum efficiency.The specific research is as follows:1.In order to improve the communication rate,some scholars adopt multi-user multi-ary chaos shift keying scheme.Although the rate is improved,the multi-level scheme is adopted to realize the multi-ary scheme,which results in weak anti-noise performance.Therefore,a multi-user multi-ary chaotic communication scheme based on phase shift keying is proposed in this paper,which is called Multi-user Multi-phase Differential Chaos Shift Keying(MUMP-DCSK)for short.Firstly,the principle block diagram of MUMP-DCSK transceiver is given.Then the Gaussian approximation method is used to derive the theoretical error rate of MUMP-DCSK under AWGN channel.Finally,the influence of each parameter on bit error rate performance is analyzed,and compared with the existing chaotic modulation schemes,it is found that MUMP-DCSK has better reliability.2.Although the above method improves the communication reliability,the fixed modulation method can't effectively utilize channel information in a complex channel,such as WBAN channel,and therefore a combination of adaptive technology and DCSK is proposed.Firstly,Starting from the theoretical bit error rate formulas of C-MDCSK(Circle-M-ary-DCSK)and S-M-DCSK(Square-M-ary-DCSK),the relations between the modulation order and the target bit error rate and the signal-to-noise ratio are obtained,and the corresponding modulation order values and the assigned power values under the maximum spectrum efficiency objective function and transmission power constraints are solved.Secondly,the adaptive coded chaotic modulation is proposed.In view of the importance of SNR estimation in adaptive coded modulation,the SNR estimation algorithm based on the data-aided estimation of C-M-DCSK and S-M-DCSK is derived by using the maximum likelihood estimation algorithm.Thirdly,the models of FM C-M-DCSK and FM S-M-DCSK UWB systems are given,and the simulations of various coded modulation combinations are carried out under the IEEE 802.15.6 standard channel to select a reasonable number of transmission modes.Finally,the selected transmission modes are switched reasonably to maximize the spectral efficiency.The experimental results show that compared with the fixed transmission mode,the adaptive coded chaotic modulation system improves the spectral efficiency.