Weikai Xu

A NOVEL DIFFERENTIAL CHAOS SHIFT KEYING MODULATION SCHEME

In binary Differential Chaos Shift Keying (DCSK), the reference and information bearing chaotic wavelets are transmitted in two consecutive time slots. This TDMA approach provides two independent c...

Performance of DCSK Cooperative Communication Systems Over Multipath Fading Channels

A differential chaos shift keying cooperative communication (DCSK-CC) system with two users is proposed in this paper, which has an orthogonal subchannel in broadcast phase and cooperative phase through orthogonal Walsh code sequences as its multiaccess scheme. The single relay cooperative network with decode-and-forward relay is investigated in the proposed system according to two cooperation protocols, namely, conventional cooperation and space-time cooperation. Unlike conventional CDMA cooperative communication (CDMA-CC) systems, quite surprisingly power control devices that consume more energy to mitigate near-far effects can be avoided in the proposed system, which is of great importance to energy-constrained networks such as wireless sensor networks. Simulation results demonstrate that, through a conventional cooperation mechanism, the proposed system has a prominent advantage of good bit-error-probability (BEP) performance over the CDMA-CC systems that have a single path correlation receiver, at the same data rate with a high SNR range over multipath Rayleigh fading channels. Meanwhile, it is found that conventional cooperation is a better cooperation strategy relative to space-time cooperation in the proposed system. In addition, a lower bound of BEP performance is derived and verified by simulations over independent three-ray Rayleigh fading channels.

Promising performance of a frequency-modulated differential chaos shift keying ultra-wideband system under indoor environments

In this study, the performance of the frequency-modulated differential chaos shift keying (FM-DCSK) ultra-wideband (UWB) system is evaluated through two important system parameters, the guard interval and the integration interval of the integrator, over indoor communication channels. It is found that the existing FM-DCSK UWB system suffers severe performance degradation in the IEEE 802.15.4a low-rate application. To resolve this problem, a new optimising scheme for the integration interval is presented. Simulation results show that the performance of the proposed scheme is significantly improved and becomes insensitive to the data rate. In addition, some notable advantages are evident in the proposed system, such as moderate multiple-access capability and feasible cross-layer optimisation.

Performance analysis of the CS-DCSK/BPSK communication system

As a spread spectrum communication system, code-shifted differential chaos shift keying (CS-DCSK) is required to provide reasonable bit error performance in a coexisting scenario where the conventional communication system is an interferer. Meantime, the bit error performance of the conventional communication system should not deteriorate dramatically in the presence of a CS-DCSK signal, which is as an interferer. This paper studies the performances of the CS-DCSK/BPSK coexisting system. By comparisons on the bit error rate (BER) of two coexisting systems, i.e, CS-DCSK/BPSK and DCSK/BPSK systems, in different channel environments at the same interference signal ratio, it reveals that CS-DCSK/BPSK has better performances than DCSK/BPSK. The BER expression of the CS-DCSK sub-system is derived in the presence of BPSK interference signals when two sub-systems are synchronized. Also derived is the BER expression of the BPSK sub-system in the presence of CS-DCSK signals when two sub-systems are asynchronized and synchronized, respectively. For the synchronization case, the BER expression of the BPSK sub-system is independent of the strengths of CS-DCSK signals. As a new interferer, CS-DCSK has less effect on the conventional communication system. It is shown that numerical simulations are in good agreement with the analytic results.

A NEW DATA RATE ADAPTION COMMUNICATIONS SCHEME FOR CODE-SHIFTED DIFFERENTIAL CHAOS SHIFT KEYING MODULATION

National Natural Science Foundation of China [61001073, 60972053]; RD Project of (CSTC) Chongqing Science & Technology Commission [2010AC3060]; Hungarian Scientific Research Fund (OTKA) [K-84045]

Design and simulation of a cooperative communication system based on DCSK/FM-DCSK

Frequency modulated differential chaos shift keying (DCSK/FM-DCSK), a joint modulation and spread spectrum technique, is a promising modulation technique for low-cost and low-complexity wireless transmission applications. The noise performance of DCSK/FM-DCSK is superior to most conventional modulation schems in multipath-channel environment. Cooperative communication, on the other hand, is receiving increasing attention due to its efficiency in sharing single-antenna mobiles or network nodes with other antennas to achieve combating fading via transmitting diversity. By combining these two aspects of advatages, a novel chaotic communication system is proposed in this paper, aiming to achieve combating multipath and fading effects. Simulation results show that significant performance improvement can be achieved by the proposed system in comparison with non-cooperative systems. It is found that the choice of some key parameters, such as the spread spectrum factor and the relay selective strategy, affect the system performance prominently. It reveals that the combination of the DCSK/FM-DCSK framework with a cooperative strategy is of great practical value for certain wireless communication networks.

Design and Analysis of a DCSK-ARQ/CARQ System Over Multipath Fading Channels

Chaotic modulation has attracted much attention in the past two decades for low-power and low-cost wireless communication applications due to its excellent anti-fading capability. In this paper, we propose a new differential chaos shift keying (DCSK)-based system equipped with a novel automatic repeat request/cooperative automatic repeat request (ARQ/CARQ) technique, called as DCSK-ARQ/CARQ system. We also modify the receiver to implement the DCSK-ARQ/CARQ system. To conduct a more insightful study, we analyze the error performance and throughput of the proposed system over multipath Nakagami- m fading channels. Both the theoretical analyses and simulated results indicate that the DCSK-ARQ/CARQ system is remarkably superior to the existing DCSK non-cooperative/cooperative communication (DCSK-NC/CC) system. Moreover, the impact of various critical parameters on the system performance is discussed and optimized so as to facilitate the practical wireless applications.

Multilevel code-shifted differential-chaos-shift-keying system

The M-ary differential-chaos-shift-keying (M-ary DCSK) system offers a good noise performance over an additive white Gaussian noise (AWGN) channel in the category of non-coherent detection chaotic systems. However, the way that the M-ary DCSK system utilises the available Walsh codes results in a relatively low bandwidth efficiency (BE). Moreover, the number of delay elements required at the transmitter and receiver increases exponentially with the number of bits per symbol. To overcome the aforementioned problems, the authors propose a multilevel code-shifted DCSK (MCS-DCSK) system in this study. In the proposed MCS-DCSK system, the reference chaotic signal and the information-bearing chaotic signals are orthogonal and are transmitted in the same time slot. They show that the MCS-DCSK system significantly outperforms the M-ary DCSK system in terms of BE and complexity. They also derive analytical bit-error-rate expressions for the MCS-DCSK system over additive white Gaussian noise and multipath fading channels, and verify them with simulation results.

Carrier Index Differential Chaos Shift Keying Modulation

A new carrier index differential chaos shift keying (DCSK) modulation method combining index modulation (IM) with multicarrier DCSK (MC-DCSK) is proposed. Two schemes employing two different index selectors and detectors to implement IM and demodulation are introduced. The new designed index selectors are one-to-one mappings between the index symbols and the carrier activation patterns, which can avoid the disaster caused by the previous designed selectors. Analytical bit error rate expressions of the two systems are derived over the additive white Gaussian noise as well as multipath Rayleigh fading channels. Simulation results verify the superiority of one scheme in energy efficiency and another scheme in spectral efficiency, respectively, compared with MC-DCSK.

Performances of CS-DCSK UWB Communication System in the Presence of Narrow Band Interferers

This paper evaluates the bit error rate (BER) performance of a code-shifted differential chaos shift keying (CS-DCSK) ultra-wide bandwidth (UWB) system over indoor communication channels under the impact of both single and multiple narrow band interference (NBI) signals. We analyze the BERs both in single NB interferer and multiple NB interferes. The analytic results and simulation results show that NBI signal has a noticeable impact on the performance of UWB systems which are independent of the carrier frequency.