Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Patent
1997-07-17
2000-06-06
Kuntz, Curtis A.
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
455 14, 455523, 455524, H04Q 720
Patent
active
060730196
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to apparatus for and a method of effecting call handover in a radio telephone system in which a mobile radio moves with respect to cables which are leaky or lossy cables radiating radio fields detected by the mobile radio.
Call handover occurs when the mobile radio transfers communication from one cable to another cable. An example of such a known system is in an underground railway. Each railway station is equipped with a radio base station serving that particular railway station. Also, each base station serves an adjacent length of tunnel bore by means of a cable which extends from the base station along the tunnel bore both towards the preceding station and towards the succeeding station, in relation to the direction of travel of trains through the tunnel bore. The train carries the mobile radio, the front of the train being fitted with an antenna which makes radio communication with the cable extending along the tunnel bore. In proceeding from one railway station to the next railway station, the mobile radio must therefore transfer its communication (ie effect call handover) from one cable to another cable, this taking place approximately half-way between the railway stations where one cable ends and the next begins.
In known systems, call handover relies upon the detection by the mobile radio of the reduction of radio field as the mobile radio reaches the end of the cable. This triggers the mobile radio to search for a new channel available at the base station located at the railway station towards which the train is travelling. During call handover, an existing call will be uninterrupted only if the mobile radio can continue to communicate with the cable about to terminate. Call handover typically takes a quarter of a second or slightly more, which at 110 km per hour corresponds to a distance travelled of about 30 meters. The length of train tends to shield the antenna after the front of the train has moved 10 meters or more from the end of the cable, so there will be a partial loss of call. The invention aims to provide an apparatus and a method which overcomes this problem.
SUMMARY OF THE INVENTION
According to one aspect of the invention there is provided radio telephone apparatus comprising a first cable for radiating a first radio field, a second cable for radiating a second radio field, and an attenuator for incorporation in the first cable adjacent an end thereof so that in use when a mobile radio effects call handover from the first radio field to the second radio field the reduction in strength of the first radio field resulting from the attenuator causes the mobile radio to initiate call handover and to complete call handover before the strength of the first radio field diminishes to an unusable level.
According to another aspect the invention provides radio telephone apparatus comprising a first base station, a first radiating cable extending from the first base station to a remote end, a second base station, a second radiating cable extending from the second base station and terminating in a remote end, the two remote ends being located in a transition area where a mobile radio effects call handover from the first base station to the second base station, an attenuator being incorporated in the first radiating cable adjacent the end thereof to cause the mobile radio to sense the diminution in radiated signal caused by the attenuator and thereby to commence call handover from the first base station to the second base station.
According to a yet further aspect the invention provides a method of effecting call handover of a mobile radio from a first radiating cable to a second radiating cable in a radio telephone system, comprising using an attenuator near the end of the first cable to cause a marked decrease in the strength of signal radiated by the first cable and sensing the decrease at the mobile radio to prompt the mobile radio to initiate call handover from the first cable to the second cable and to maintain communication with the f
REFERENCES:
patent: 4006315 (1977-02-01), Halstead
patent: 5420883 (1995-05-01), Swensen et al.
patent: 5496003 (1996-03-01), Bernard
patent: 5603080 (1997-02-01), Kallander et al.
patent: 5913168 (1999-06-01), Morau et al.
Patent Abstracts of Japan, vol. 011, No. 292, JP 62 091026.
Patent Abstracts of Japan, vol. 016, No. 392, JP 04 127726.
Patent Abstracts of Japan, vol. 009, No. 140, JP 60 022834.
Patent Abstracts of Japan, vol. 012, No. 111, JP 62 242427.
Kuntz Curtis A.
Nokia Telecommunications Oy
Tieu Binh K.
LandOfFree
Radio telephone call handover does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Radio telephone call handover, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Radio telephone call handover will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2222292