Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Patent
1997-01-14
1999-09-28
Le, Thanh Cong
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
455451, 455452, 455 62, H04B 726
Patent
active
059603542
DESCRIPTION:
BRIEF SUMMARY
This application is the national phase of international application PCT/FI96/00272, filed May 15, 1996 which designated the U.S.
SUMMARY OF THE INVENTION
1. Field of the Invention
The invention relates to a cellular mobile telephone network with at least two frequency bands and in which at least some mobile stations may use whichever frequency band for communication, and in which the control channel associated with a traffic channel may be dedicated so that the network may send control information individually to the mobile station.
2. Background Information
According to the standard, e.g., a frequency band in a GSM mobile communications network comprises two sub-bands 25 MHz wide each, with frequency ranges 890-915 MHz in the uplink direction, i.e., from the mobile station to the base station, and 935-960 MHz in the downlink direction, i.e., from the base station to the mobile station. While the GSM network specification was being drawn up, another band with a higher frequency was also included therein. It comprises 75 MHz sub-bands, with a frequency range 1710-1785 MHz in the uplink direction and 1805-1880 MHz in the downlink direction. The system operating in the 1800 MHz frequency range is called the DCS system (DCS, Digital Cellular System) and its specification is a part of the GSM specification. Propagation properties of radio waves of the bands are different: on DCS frequencies free space attenuation is greater than on GSM frequencies. A natural cause of this is that GSM frequencies are well suited for covering an extensive cell, whereas DCS frequencies are suited for covering small cells.
Except for the frequency differences, the systems are essentially similar, e.g. the air interface is the same. Even at present, the GSM network is in some countries, especially in urban areas with high traffic density, on the upper limits of its capacity, and hence the GSM band frequencies available to the operator are no longer sufficient to ensure service to all subscribers. Channel capacity has been increased by spreading the frequency band, so-called extended-GSM, but decisively more capacity will be obtained by taking into use another frequency band, i.e., transfer to multiband operation. This provides additional capacity to sites with high traffic density where the GSM band frequencies available to the operator no longer suffice to ensure service to all subscribers.
Both GSM and DCS frequency bands may be used either in separate networks or as a combined network under common network control. In the latter case, mobile stations able to operate on both frequency bands may be used. Such mobile stations are called multiband mobile terminals. Multiband mobile terminals are of two types.
A mobile terminal of the first type meets the requirements specified for both bands and may thus operate, e.g., on either a GSM or a DCS band by registering into the respective network. This type of mobile station does not, however, support handover between bands of operation, channel assignment, cell selection or cell re-selection between the bands of operation. The mobile station does not therefore require any network support to work on more than one band, and it uses the channels of that particular band only.
A mobile terminal of the second type continuously uses the channels of both bands, and hence not only meets the requirements specified for both bands, but some additional requirements, too. The additional features compared with a mobile station of the first type are that it is able to perform handover, channel assignment, cell selection and cell re-selection between the bands of operation. Thus, the network has to support these operations.
In this application a case will be described where the network supports mobile stations of the second type, i.e., telephones that are able to operate on both bands. The coverage areas of both GSM and DCS networks are at least partially overlapping.
A feature typical of a multiband mobile terminal of the second type, later referred to as a multiband mobile station, is the above mentio
REFERENCES:
patent: 5373547 (1994-12-01), Patsiokas et al.
patent: 5428816 (1995-06-01), Barnett et al.
patent: 5666650 (1997-09-01), Turcotte
Patent Abstract of Japan, JP 7038943 A (NTT Idou Tsuushinmou KK), Feb. 7, 1995.
Cong Le Thanh
Nokia Telecommunications Oy
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