Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Patent
1998-03-31
2000-09-05
Bost, Dwayne D.
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
455449, H04Q 730
Patent
active
061156108
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to mobile radio systems. The invention will be described primarily in relation to cellular radio networks. However the invention is also applicable to other mobile radio systems, such as private mobile radio (PMR) systems.
2. Related Art
In a typical cellular radio network a number of radio base stations are located throughout the area in which radio coverage is required, in order to allow mobile units throughout that area to be in radio communication with the fixed part of the network via one of the radio base stations. The radio base stations comprise radio transceivers for establishing radio communication with nearby mobile units. Several radio channels are provided to allow simultaneous communication with several mobile units. These radio channels may for example be separate time slots in a time-division scheme, and/or different radio frequencies. The radio base stations are themselves physically connected by fixed links to a switching centre, and thereby a communications link can be activated between two mobile units via respective radio base stations, or between a mobile unit (again via a radio base station) and a fixed telephone network e.g. PSTN, or other cellular radio system, or other telecommunications network.
The radio base stations require control functions to establish radio communication with mobile units, and to carry out various other functions to determine which mobile units are within its area of coverage in order to direct incoming calls to the correct mobile unit, and to arrange handover of calls should a mobile unit move during the course of a call from the area served by one base station to that served by another. Such control functions include commands to the radio base stations to communicate with a mobile unit on one of its allocated channels, including instructions as to when to start and terminate the call, or to carry out handover processes.
In the GSM (Global System for Mobile radio) standard, these control functions of the radio base stations are functionally, and usually physically, separate from the transceivers they control. The control functions are performed by a "Base Site Controller" (BSC) controlling the radio transceivers of several radio base stations, (known in the GSM system as "Base Transceiver Sites" (BTS)), which may be some distance away. Because of the complexity involved, it is advantageous to concentrate the necessary equipment to perform the control functions in a small number of locations in this way, to provide ease of access for maintenance. The terminology used in the GSM standard is used herein for convenience, but is not limitative on the scope of the claims. In particular, it should be noted that the term "radio base station" embraces a base transceiver site unless the context clearly demands otherwise.
The connections between the base transceiver sites and the base site controller can be quite long, typically several tens of kilometers. The connections between the base transceiver sites and the base site controllers can make up a substantial part of the infrastructure of the cellular radio network. In many cases the fixed links from several base transceiver sites meet at some point, hereinafter referred to as a "branch point", intermediate between the base transceiver site and the base site controller or other switch, and continue from the branch point over a common trunk link, for the rest of the route to the base site controller or other switch.
Each base transceiver site has a number of radio channels available to it. The number of channels determines the maximum number of mobile units which can communicate with a base transceiver site simultaneously. In order that this maximum capacity can be achieved, the fixed physical link between the base transceiver site and the base site controller requires at least the same number of individual communication channels to be available to it. The term "channel", as used herein, refers to the resources (time slot, cable, carrier f
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Gannon Stephen M
Goetz Ian
Munday Peter R
Bost Dwayne D.
British Telecommunications public limited company
Redmon Joy K.
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