Simon S. F. Hau

A multiple-access technique for differential chaos-shift keying

A multiple-access technique for use with differential chaos shift keying is proposed and analyzed in this paper. A simple one-dimensional iterative map is used to generate the chaotic signals for all users and the average data rates for the users are identical. Bit-error rates are derived numerically for different numbers of users and computer simulations are performed to verify the results.

A multiple access technique for differential chaos shift keying

Various chaos-based digital communications techniques have been proposed recently. Among them, differential chaos shift keying (DCSK) allows the receiving end to decode the signal using noncoherent detection. This paper proposes and analyses a multiple access scheme for DCSK. A simple 1-dimensional iterative map has been used to generate the chaotic signals for all users. Bit error probabilities have been derived numerically for different numbers of users and computer simulations have been performed to verify the results.

Return-map-based approaches for noncoherent detection in chaotic digital communications

In this work, simple noncoherent detection methods for chaos-shift-keying (CSK) modulation are proposed. By exploiting some deterministic property of the two chaotic maps, the proposed methods recover the digital message through simple decision algorithms. Specifically, the proposed methods exploit the difference in the return maps of the signals representing the digital symbols. Two specific algorithms are discussed, namely a regression-based algorithm and a probability-based algorithm. Simple tent maps are used for illustration. The bit-error-rate under additive white Gaussian noise is studied by computer simulations.

Anti-jamming performance of chaotic digital communication systems

Among the various modulation schemes proposed for chaos-based digital communications, chaos-shift keying (CSK) and differential chaos-shift keying (DCSK) have been most thoroughly analyzed and considered for practical implementation. One important aspect of performance of any communication system is the ability to resist jamming. This area of study, however, is not available in the literature. In this paper, an analysis of antijamming performance of the coherent CSK and noncoherent DCSK systems is presented. The study includes performance analysis for the two types of systems in terms of the bit error probability under different levels of noise power, jamming power, jamming frequency and spreading factor. Computer simulations are used to verify the analytical results.

Application of complex-network theories to the design of short-length low-density-paritycheck codes

Study of complex networks has been conducted across many fields of science, including computer networks, biological networks and social networks. Characteristics of different types of complex networks such as random networks, regular-coupled networks, small-world networks and scale-free networks have been discovered by researchers. Application of such network properties to solve engineering problems, however, is still at the infancy stage. In this study, we make one of the first attempts in applying complex network theories to communications engineering. In particular, inspired by the shortest-average-path-length property of scale-free networks, we design short-length low-density-parity-check (LDPC) codes with an aim to shortening the average distance between any two variable nodes. We will also compare the error performance, both theoretically and by simulations, of the proposed codes with those of other well-known LDPC codes.

Performance analysis of serial cooperative communications with decode-and-forward relaying and blind-EGC reception under nakagami fading channels

We analyze a serial cooperative transmission system with DF relaying over Nakagami fading channels. We consider a system in which the simple receivers will not estimate the amplitude of the received signals. Hence, signals are combined with equal gain before decoding. Moreover, the relays use a simple protocol when relaying the messages - they re-transmit the message if they can decode the received message correctly; otherwise, they do not transmit anything and remain idle. We will derive an exact expression for the asymptotic symbol error rate of the system and evaluate the diversity properties.

Error rate and diversity order of multinode cooperative communications in dissimilar nakagami fading channels

Cooperative communications has been recognised as an effective technique to combat multi-path fading impairment and to provide additional diversity advantage for small-size and low-power-consumption mobile terminals. A class of decode-and-forward (DF) relaying serial cooperative communications, in which each node is assumed to be able to determine whether the received signals can be successfully decoded or not, has recently been proposed and analysed over Rayleigh fading channels. Since the Nakagami fading channels represent a wide variety of realistic channels, such serial cooperative networks should be investigated over such channels before putting into real applications. In this paper, we analyse the performance of such serial cooperative transmission systems thoroughly over dissimilar Nakagami fading channels. We derive a closed-form symbol-error-rate expression for the case of M-ary phase shift keying (PSK) modulation. Moreover, we evaluate the system diversity property and investigate the achievable diversity order under two specific channel conditions. Finally, we perform simulations to verify the theoretical findings.

On the estimation of bulk delay and length of dispersive region in echo cancellation

In this paper, the starting and ending position indices for far-end echo are estimated. A search algorithm is proposed to determine the position index using the centroid of the dispersive region as the initial starting point. Block processing algorithms are proposed for the smoothing of the estimated dispersive length. The results show that improvement can be obtained by increasing the block length. Further improvement can be obtained by using the instantaneous block LMS weight updating in the coefficient of echo canceller.<<ETX>>

Channal Impulse Response: Measurements and Interpretations

This paper presents a selection of results obtained during an impulse responsemeasurement campaign undertaken in Hong Kong at 1.8 GHz. The chanel probingsignal bandwidth of 60 MHz was generated by a pseudorandom sequence clockedat 30 MHz. The results of the channel impulse response measurements in theHung Hom district of Kowloon, Hong Kong are presented. The measured resultsare analyzed for CIR parameters like delay spread, average delay and thesignificant number of paths. An attempt is made to relate the measured datawith the geometry of the environmental features that surround the transmitterand the receiver.

Mobile radio channel impulse response: measurements and interpretations

An impulse response measurement campaign was undertaken at 1.8 GHz in Hong Kong. This paper presents a selection of measurement results. A pseudorandom sequence clocked at 30 MHz occupying an RF bandwidth of 60 MHz was used as a probing signal. The results taken at a selected location are analyzed for CIR parameters like delay spread, average delay and significant number of paths. An attempt has been made to relate the measured data to the geometry of environmental features surrounding the transmitter and the receiver.