Performance comparison between GSM and PCN system design in underground subway

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Performance comparison between GSM and PCN system design in underground subway

 

Author: Chan, Kin-ngai
Title: Performance comparison between GSM and PCN system design in underground subway
Degree: M.Sc.
Year: 1998
Subject: Mobile communication systems
Global system for mobile communications
Personal communication service systems
Cellular telephones
Hong Kong Polytechnic University -- Dissertations
Department: Multi-disciplinary Studies
Dept. of Electronic Engineering
Pages: [7], 117, [3] leaves : ill. ; 30 cm
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b1436948
URI: http://theses.lib.polyu.edu.hk/handle/200/1560
Abstract: Hong Kong is an international metropolis and one of the elements which makes this place successful is the well organized and advanced telecommunication networks. Today, mobile cellular telecommunication becomes an essential communication tool to Hong Kong people such that they can be reached at any time and any place. Therefore, the demand of the cellular network coverage is not only restricted to roads, highways or indoor environments, but also to the underground subways. The users also expect to roam freely as they ride on the trains in the tunnels. The methodology used in the subway is to implement the traditional fiber optic micro-cell architecture in order to provide coverage inside the stations and the long tunnels. A microcell is a region served by a base station, just like normal cellular network, but it is smaller in area by one to two orders of magnitude. The optical fiber is used to carried the converted radio frequency signal between base station and the subway stations. The Radio Frequency (RF) signal from the base station is converted to optical signal, transmitted to the serving station, converted back to RF signal, amplified and transmitted through leaky cable to the mobile units. For the RF signal received from the mobile units back to the base station, the process is just reversed. The current Global System for Mobile Communication (GSM) system design in subway tunnel introduces the handover position in the middle of the tunnel between two stations. Usually, the signal in the serving subway station received by the mobile units will be around -78dBm to -88dBm along the tunnel only. However, based on this design, occasionally, the signal strength will be less than -90dBm inside the tunnel. Since the signal is weak but the train speed is high and the GSM handover mechanism delays the handover decision, this design will create call drop possibilities during handover and the number of call drops will be expected to be much larger in Personal Communications Network (PCN). Therefore, the system design in the subway tunnel between two stations must be carefully considered. A new system design for PCN is to extend the serving cell signal to be close to the neighbour cell such that both cell signals are strong enough to provide a smooth handover when the mobile is approaching the next station. This kind of design is called 'S' shape design. Moreover, this design may accommodate more carriers to cater for particular operator's increasing capacity and still provides enough signal strength to the mobiles.

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