Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Patent
1997-08-06
1999-10-26
Bost, Dwayne D.
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
455422, 455447, 455562, H04Q 720
Patent
active
059743263
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to channel allocation in a radio telephone system having base stations with which mobile radios are in radio communication.
2. Description of the Related Art
The invention addresses a limitation in conventional channel allocation whereby radio channels cannot be re-used by adjacent base stations due to the interfering radio coverage zones, even when mobile radios are not operating in those zones. There are radio systems where a proportion of the mobile radios are always located in such isolated areas that the channels used by them can be re-used in neighbouring areas. For instance, at in an underground railway system (where radio base stations are located at each railway station) there can be such radio isolation at the railway stations. However, this isolation does not exist in tunnels interconnecting the railway stations because in the tunnels the radiating cables of the two adjacent base stations meet. If it is necessary to allocate a channel for use in a tunnel it is important that this channel is not re-used on the adjacent cable since this would cause interference and malfunction of the mobile radio roaming technique. Therefore, the use of the channel for a call in a tunnel would normally preclude its re-use at the next railway station even though the mobile radio user may only require radio coverage within the railway station area. This is wasteful of radio channels and the aim of the invention is to improve the efficiency of channel allocation.
BRIEF SUMMARY OF THE INVENTION
According to one aspect of the invention there is provided a radio telephone system comprising at least a first base station A having two antennas for communicating with a mobile radio in areas .alpha. and .beta. respectively and a second base station B having two antennas for communicating with a mobile radio in areas .gamma. and .delta. respectively, wherein a first set of channels is allocated to the first base station A, the first set of channels including a channel C.alpha. for serving area a and a channel C.beta. for serving area .beta., and a second set of channels is allocated to the second base station B, the second set of channels including a channel C.gamma. for serving area .gamma. and a channel C.delta. for serving area .delta., areas .beta. and .delta. being in radio interference over an interference zone, characterised in that channel C.delta. is additionally allocated to the first base station A to serve area .alpha. and the first base station A has first discriminating means which are operative to detect a call on channel C.delta. in area .alpha. and to prevent the channel thus occupied being directed to the antenna serving area .beta., and wherein channel C.beta. is additionally allocated to the second base station to serve area .gamma. and the second base station has second discriminating means which are operative to detect a call on channel C.beta. in area .gamma. and prevent the channel thus occupied being directed to the antenna serving area .delta.. The antennas are preferably lossy or leaky cables, eg coaxial cables.
For example, in an underground railway system, the two base stations A and B are located at adjacent railway stations, area .alpha. serving one railway station and area .gamma. serving another railway station B. Areas .beta. and .delta. are the lengths of tunnel interconnecting the railway stations. A train carrying an antenna makes train calls by communicating with radio fields set up by the cables serving areas .beta. and .delta., ie the tunnels. A person carrying a mobile radio makes station calls by communicating with the radio fields set up by cables serving areas .alpha. and .gamma..
By recourse to the invention channel allocation can be shown by the following table:
______________________________________ Base Station A
Base Station B
______________________________________
Station Call Channels
C.alpha., C.delta.
C.gamma., C.beta.
Train Call Channels
C.beta.,
C.delta.
__________________
REFERENCES:
patent: 5212830 (1993-05-01), Miller
patent: 5432780 (1995-07-01), Smith et al.
patent: 5491833 (1996-02-01), Hamabe
patent: 5649292 (1997-07-01), Doner
patent: 5722043 (1998-02-01), Rappaport et al.
patent: 5724666 (1998-03-01), Dent
patent: 5742911 (1998-04-01), Dumbrill et al.
patent: 5787344 (1998-07-01), Scheinert
patent: 5812956 (1998-09-01), Pregont
patent: 5835859 (1998-11-01), Doner
39.sup.TH VEHICULAR TECHNOLOGY CONFERENCE, May 1-3, 1989, "Radio in the London Underground", Martin et al., pp. 375-382, vol. 1, IEEE.
Bost Dwayne D.
Maung Nay A.
Nokia Telecommunications Oy
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