Research On Trellis-Coded Chaotic Shift Keying Communications

During the last decade,the study of digital chaotic shift keying communication schemes has been carried out extensively in the literature.Due to the inherent wideband and non-periodic characteristics of chaotic signal,the schemes offer excellent system performance when the communication channel suffers deep frequency-selective fading as compared to traditional narrow-band modulations.This advantage makes chaotic communications suitable for applications where the most system parameter is the sensitive to multipath environment,such as WLAN(Wireless Local Area Network),mobile communications and indoor radio.Being aware that the performance of chaotic modulation in AWGN(Additive White-Gaussian-Noise)is not as satisfactory as over a multipath channel,the article is performed mainly on the exploration of efficient chaotic communication schemes with high anti-noise capability.And the main research fruits are as follows.First we establish the modeling of existing basic chaotic shift keying schemes:DCSK(Differential Chaos-shift-keying),FM-DCSK(Frequency modulated DCSK)and QCSK(Quadrature Chaos-shift-keying),FM-QCSK (Frequency modulated QCSK).On the basis of analysis and simulation results,an enhanced scheme for QCSK and FM-QCSK is proposed.The idea starts with the notion that "increase the effective energy rate",so,in the scheme,L symbols group as a frame and transmit after each chaotic reference signal.Then, considering the sameness of the symbols in a frame we design an optimizing algorithm called Quadrature Averaging-noise-reducing to further improve the performance of the proposed modulation scheme.Then trellis-coded modulation(TCM)is introduced into discussion.TCM combines modulation and coding schemes,that achieve error-performance improvements without expansion of signal bandwidth or reducing the data rate. As an elementary scheme of applying TCM,we proposed TCM-QCSK and TCM-FM-QCSK based on the existing QCSK scheme.The schemes achieve by utilization of a typical(2,1,3)convolutional code and the soft-decision Viterbi decoding algorithm.And the analytic BER performance of the proposed schemes is derived by using bound theory. To explore the senior application of trellis-code based chaotic shift keying, this work constructs 8-ary DCSK by expanding the signal set of QCSK into 8 signal constellations,and introduces TCM-8DCSK and TCM-FM-8DCSK schemes which can be considered as the chaotic counterpart of TCM-8PSK in conventional digital communications.We've deduced the theoretical noise performance of 8DCSK,and the TCM-8DCSK's coding gain is also given through calculating the free Euclid distance of the involved four-state(3,2,3) convolutional code.Theoretic analysis and simulation results show that TCM brings prominent performance enhancement to chaotic shift keying and holds the quondam bandwidth occupation and data rate.We conclude that trellis-code based chaotic shift keying is an efficient solution for chaotic communications.