A study of parametric influence on GSM frequency hopping network

Pao Yue-kong Library Electronic Theses Database

A study of parametric influence on GSM frequency hopping network

 

Author: Ng, Kam-ming
Title: A study of parametric influence on GSM frequency hopping network
Year: 2001
Subject: Personal communication service systems
Hong Kong Polytechnic University -- Dissertations
Department: Multi-disciplinary Studies
Dept. of Electronic Engineering
Pages: iv, 69, [19] leaves : ill. ; 30 cm
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b1599576
URI: http://theses.lib.polyu.edu.hk/handle/200/99
Abstract: Global System for Mobile Communications (GSM) is the European standard for 2nd generation digital mobile telephone system. Now GSM becomes the most popular system around the world. The frequency band used in GSM is 890 - 910MHz (uplink) and 935 - 960MHz (downlink). There are 124 carrier frequencies spaced 200kHZ apart, using FDMA technique. Each of these carrier frequencies is further divided into 8 time slots using TDMA technique. The fundamental unit of time in this TDMA scheme is call burst and it lasts approximately 0.557ms. The modulation used in GAM is Gaussian Minimum Shift Keying (GMSK), with a BT value of 0.3 at a gross rate of 270.833kbps. Since GSM is designed on FDMA/TDMA basis. That means a particular time slot on a particular frequency is dedicated to a single user. The quality of the call is subject to the sensitivity of fading and interference. Frequency Hopping (FH) can be employed to minimize interference from other signals. Random Frequency Hopping (FH) on GSM can make transmission less sensitive to fading and interference. Since mobile radio channels are frequency selective, FH will spread sequential information over a wider frequency domain, and some frequency diversity gain is obtained. Without FH, strong signal from neighbouring cells (of co-channel or adjacent channel) will affect the C/I ratio and make the transmission quality worse. Under FH, signals will interfere with the carrier at different time slots, hence signal diversity gain is obtained. In this dissertation we present a performance evaluation of a frequency hopping GSM system that is based on simulation of frequency hopping GSM network together with features of DTX and downlink power control. We have evaluated the system performance in terms of congestion, call drop rate and received quality distribution. We show that frequency hopping could be successfully implemented in GSM network with significant improvement in received quality.

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