Guofa Cai

Design and Performance Analysis of a New Multiresolution

A new multiresolution M-ary differential chaos shift keying (DCSK) modulation scheme is proposed in this paper. It is a promising technique for providing a different quality of service for transmitted bits within a symbol according to their different bit error rate (BER) requirements based on the principle of nonuniformly spaced constellations. The new system not only is simple but also provides better antimultipath fading performance against various spreading factors, inheriting the advantages of the conventional DCSK system. Furthermore, the proposed scheme and its multicarrier version further increase spectral efficiency and use lower energy consumption at the same bandwidth as compared with the conventional DCSK and its multicarrier system. Explicit BER expressions of the new system are derived and analyzed over additive white Gaussian noise and multipath Rayleigh fading channels. All simulation results verify the prominent advantages of the new scheme and the accuracy of the new analytical approach.

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Although the performance of a differential chaos shift keying (DCSK) system can be improved by designing appropriate channel codes, it is still a great challenge to do so for various channel models through transmitter and receiver designs, particularly with short frame length transmissions. Alternatively, to bypass the difficult task of designing a good channel code, an iterative receiver (IR) DCSK system is proposed in this paper. A soft demapper suitable for non-coherent

-Ary Differential Chaos Shift Keying Communication System

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Iterative Receiver for

-ary DCSK system is presented, which can work either with or without fading amplitude information. Bit error rate (BER) performance shows its advantages over the non-IR DCSK system in different channel models. The achievable rate curves also indicate that gains relative to non-iterative DCSK system can be achieved with the iterative receiver.

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In this article the capacity expression is derived for M-ary Differential Chaos Shift Keying (M-DCSK) modulation over additive white Gaussian noise (AWGN) channel. Then the capacity bound curves of M-DCSK are provided by Monte Carlo method. Theoretical analysis and simulation results show that the high dimension DCSK modulation has more obvious capacity advantage than the conventional modulations. So they are appropriate for the power-limited communication systems.

-ary DCSK Systems

In this paper, a square-constellation-based M-ary differential chaos-shift-keying (M-DCSK) communication system framework is proposed. The symbol-error-rate expression of the proposed system is derived over additive white Gaussian noise as well as multipath Rayleigh fading channels. Moreover, the peak-to-average-power-ratio (PAPR) performance is carefully analyzed for the newly proposed system. Based on the square-constellation-based M-DCSK framework, a simple least-square estimator is designed to demodulate the information exploiting pilot-assistant symbols. Analytical and simulated results show that the proposed system benefits from a lower energy consumption, but suffers from a higher PAPR compared with the circle-constellation-based M-DCSK system.

Channel capacity of M-ary Differential Chaos Shift Keying modulation over AWGN channel

In this article, an iterative demodulation and decoding receiver for M-ary differential chaos shift keying (DSCK) modulation is proposed over Additive White Gaussian Noise (AWGN) channel. The Log-Likelihood Ratios (LLRs) of coherent DCSK demodulator and decoder are derived assuming that its perfect carrier synchronization happened. The simulation results show that the performance of our proposed iterative receiver outperform that of the noniterative receiver over AWGN channel due to extrinsic information exchanged between demodulator and decoder. Further-more, Extrinsic Information Transfer chart is used to investigate the convergence behavior of our proposed receiver.

A Square-Constellation-Based

In this paper, we deal with the problem of maximum likelihood (ML) estimation of the signal-to-noise ratio (SNR) parameter for frequency modulated differential chaos shift key (FM-DCSK) system over multipath Rayleigh fading channels. The ML estimators are derived for various scenarios including data-aided (DA), non-data aided (NDA) and joint DA-NDA estimation by using both the data and pilot symbols. For comparison purposes, the Cramér- Rao lower bounds (CRLBs) for the SNR estimators are derived. The performance of the estimators is evaluated by simulations and comparing with CRLBs in terms of the mean-square-error. Simulated results show that for a large spreading factor the proposed scheme performs well over a wide SNR range in comparisons with CRLBs.

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Capacity bounds are calculated for the differential chaos shift keying (DCSK) system with non-coherent detectors, including differentially coherent detector and energy detector, over additive white Gaussian noise (AWGN) and Rayleigh fading channels. Through theoretical analysis and numerical simulations, it is found that the capacity characteristics of the non-coherent DCSK system are significantly different from those of the coherent case. It is shown that there are different capacity bounds corresponding to different spreading factor values. Optimal code rates are found, which minimise the required bit signal-to-noise ratio for a reliable communication system, and they are increasing with the increase of the spreading factor value over an AWGN channel while decreasing over a Rayleigh fading channel. As compared with the AWGN channel, the performance over a Rayleigh fading channel is much more sensitive to the code rate. The new results are useful as benchmark for designing capacity-approaching codes for the non-coherent DCSK system.

-Ary DCSK Communication System

In this paper, an adaptive retransmission mechanism of single-input frequency-modulated differential chaos shift keying Ultra-wideband (SIMO FM-DCSK UWB) system with automatic repeat request (ARQ) protocol has been investigated, in which scheme adaptive unit delay (Td) is used to control transmission. Unlike the previous work based on optimal assignment of number of pulses per symbol or frame duration, the adaptive unit delay (Td) will not change the data rate or bandwidth, only can change the position of the pulses. Through simulation it is shown that bit error rate (BER) and throughput performances of the proposed scheme are better than normal retransmission mechanism when it is applied to two-user or multi-user systems over indoor channel, it reflects that our proposed scheme can enhance performance of chaotic UWB systems.