Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Patent
1996-09-09
2000-05-09
Dolinar, Andrew M.
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
455560, 370328, H04Q 722
Patent
active
060615664
DESCRIPTION:
BRIEF SUMMARY
This application claims benefit of international application PCT/FI195/00122, filed Mar. 3, 1995.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a mobile communication system comprising at least mobile stations; base station systems, each comprising a base station controller and several base stations; mobile services switching centers, each comprising call control means and switch means for controlling and switching calls of mobile stations; and transcoder units, each comprising encoding and decoding means for decoding an encoded speech signal received from a mobile station, and for encoding a speech signal to be transmitted to a mobile station. For switching the calls, there are network connections that are allocated call-specifically between a base station, a base station controller and a mobile services switching centre, a speech signal being transmitted in transmission frames over said network connections, the base stations and the transcoder units comprising means for building, debuilding and synchronizing the transmission frames, the uplink transmission frames transmitted by the base station to the transcoder unit containing synchronizing information on the basis of which the transcoder unit times the transmission of the downlink transmission frames to the base station.
2. Description of Related Art
In cellular or trunked radio systems, generally referred to as mobile communication systems, a mobile radio station, i.e. a mobile station communicates with a fixed network via a fixed radio station, i.e. a base station that is located in a cell. Mobile stations may freely move from one cell to another in the area of the system. A general principle of the mobile communication networks is always to direct telephone communication to the area in which a mobile station is currently located. In order to be able to route the incoming calls to the mobile station, the radio network maintains location registers, in which the location of the mobile station is known with an accuracy of one or more base stations. A mobile services switching center or a base station controller control switching of a call to the correct base station. A base station controller is used when the base stations are grouped into base station systems comprising several base stations having a common base station controller. A mobile services switching center controls telephone communication within its service area and connects the base station controllers to the outside world.
GSM (Global System for Mobile Communication) is a pan-European telecommunication system, which is becoming a world-wide standard. FIG. 1 presents, very briefly a few basic components of the GSM system. A mobile services switching center (MSC) is in charge of switching incoming and outgoing calls. It performs similar operations as in the exchange of a public switched telephone network. In addition, it also performs operations typical only of mobile telecommunication, such as subscriber location management. Mobile radio stations, i.e. mobile stations are switched to the center MSC by means of base station systems. A base station system comprises a base station controller BSC and base stations BTS. A base station controller BSC is used for controlling several base stations.
The GSM system is completely digital, and speech and data transmission also take place completely digitally, which enables a uniform high quality of speech. From the point of view of the network, the most limited resource is the radio frequency link needed on the radio path between the mobile stations and the base stations. In order to reduce the radio frequency band needed by the radio connection, speech encoding is employed in the speech transmission. The speech encoding is more efficient than the 64 bit/s transmission typically employed in telephone networks. A mobile station must naturally comprise a speech encoder and decoder for speech encoding. In the network, various speech encoding and rate adapting operations are concentrated in a transcoder unit TRCU (Transco
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patent: 5260987 (1993-11-01), Mauger
patent: 5418838 (1995-05-01), Havermans et al.
patent: 5475689 (1995-12-01), Kay et al.
patent: 5497396 (1996-03-01), Delprat
Patent Abstracts of Japan, vol. 12, No. 489, E-696,63-204928 (Nippon Telegr, & Teleph Corp.), Aug. 24, 1988.
Dolinar Andrew M.
Nokia Telecommunications Oy
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