The use of WDM for timing synchronization in rayleigh fading channel

Pao Yue-kong Library Electronic Theses Database

The use of WDM for timing synchronization in rayleigh fading channel

 

Author: Chan, Ching-yuen
Title: The use of WDM for timing synchronization in rayleigh fading channel
Degree: M.Sc.
Year: 1997
Subject: Radio -- Transmitters and transmission
Radio wave propagation
Hong Kong Polytechnic University -- Dissertations
Department: Multi-disciplinary Studies
Pages: vii, 114, [32] leaves : ill. ; 30 cm
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b1398623
URI: http://theses.lib.polyu.edu.hk/handle/200/1486
Abstract: This paper uses computer simulation, to analyze and evaluate the performance of a timing recovery method called Wave Different Method (WDM) with π/4 DQPSK modulation techniques in mobile channel which responses over urban areas for narrow-band radio transmissions at various vehicle speeds. In the simulation process, the mobile radio channel is modeled as Rayleigh. To obtain Rayleigh fading channel, the two independent Gaussian noise sources are connected to two identical low-pass shaping filters and the outputs of each are added together. The channel is then verified by the level crossing rate and cumulative distribution. This paper investigates the effect of various vehicle speed on fading channel. Such effect is measured by the bit error rates (BER) which are obtained from the communication system model. For communication system model, the data rate 24.3k Baud operated at the carrier frequency of 850 MHZ is used. It is specified by the U.S Digital Cellular Standard IS-54. However, in actual communication channel, the presence of phase jitter and other disturbances such as noise will result in symbol timing error. Thus, additive Gaussian noise (AWGN) , intersymbol interference (ISI) and jitter are also simulated. In fact, this paper put special emphasis on how to overcome the AWGN, ISI and jitter by using WDM timing recovery technique; how to optimum difference parameters in the algorithm and minimize the effect of gaussian noise by varying those parameters. Simulation of the WDM tracking algorithm is carried out both in noiseless and noisy channel and the tracking performance and degradation are evaluated. The WDM which has been implemented as part of CCITT V.22 bis for 2400 bps full-duplex voice band modem [1], is now used in mobile channel with π/4 DQPSK modulation for timing synchronization. Simulation results show that the WDM timing recovery technique can minimize the effect of gaussian noise and jitter by varying parameters. (e.g. α and δ ). For example , with α between 0.005 and 0.015, step-size δ between 0.0001 Tb and 0.001Tb, the performance for jitter tracking is satisfactory.

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