Telecommunications – Transmitter and receiver at separate stations – Single message via plural carrier wave transmission
Patent
1993-06-03
1994-12-20
Kuntz, Curtis
Telecommunications
Transmitter and receiver at separate stations
Single message via plural carrier wave transmission
455 341, 379 58, H04B 7005
Patent
active
053752538
DESCRIPTION:
BRIEF SUMMARY
SUMMARY OF THE INVENTION
The invention relates to a call control method for a radio system, wherein a half-duplex type mobile subscriber radio station is commanded so as to clear a call on a radio channel of a base station, by transmitting a disconnect signal to the mobile subscriber radio station over the radio channel, the mobile subscriber radio station leaving the radio channel on receiving the disconnect signal.
BACKGROUND OF THE INVENTION
A half-duplex type transceiver transmits and receives on the same radio channel and is not able to receive while its own transmitter is in operation. This property of the half-duplex mobile radio may result in a situation in which the transmitter of the mobile radio is in operation when the call terminates during a call disconnect signal transmitted from the mobile exchange, and does not receive the disconnect signal but remains on the traffic channel even though the mobile exchange has cleared the call and released the traffic channel. The same channel can be allocated to a new call immediately after the release, and so the mobile radio remaining on the traffic channel after a preceding call may undesirably participate in the new call or at least hear the beginning of the call.
Previously, attempts have been made to solve this problem by transmitting special selective disconnect messages on the traffic channel in the beginning of the call, which messages command the mobile radios not associated with the current call to leave the channel. If the transmitter of the mobile radio remaining on the channel after the preceding call is still or again in operation even when such disconnect messages are being transmitted, the mobile radio does not receive the messages and will not leave the channel. Such disconnect messages can be transmitted continuously during the call, in which case they, however, deteriorate the call quality, causing short breaks.
SUMMARY OF THE INVENTION
The object of the invention is to avoid the above-mentioned problems of the prior art.
This is achieved by means of a call control method according to the invention, wherein the field intensity received by the base station on the radio channel is measured immediately after the transmission of the disconnect signal, and the radio channel is released for the next call only when the measured field intensity falls below a predetermined threshold value.
After the disconnect signal has been transmitted by the mobile exchange on the traffic channel, the base station immediately measures the field intensity on the channel. If the measured value is high enough, it is assumed that the transmitter of the mobile radio is in operation, and the channel is not released for the next call. After the carrier signal of the mobile radio has disappeared from the channel, which is detected as a decrease in the measured field intensity below a predetermined threshold value, a new disconnect signal is first transmitted and the channel is released for the next call. By the procedure according to the invention, the mobile radio cannot remain on the channel when the next call begins, and so no additional disconnect messages need to be transmitted during the call.
BRIEF DESCRIPTION OF THE DRAWINGS
In the following, the invention will be described in greater detail by means of illustrating embodiments with reference to the attached drawings, in which: FIG. 1 illustrates a radio system in which the invention is applicable; and FIGS. 2A and 2B are flow charts illustrating practices of the method of the present invention.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION
The radio system shown in the FIG. 1 comprises at least one fixed transceiver equipment BS, which will be referred to as a base station in this connection. The base station usually has several radio channels for communication purposes (pairs of transmitting and receiving frequencies), a separate transceiver unit being assigned for each radio channel. At least one radio channel is a so-called control channel for control signalling between the
REFERENCES:
patent: 4633509 (1986-12-01), Scheinert
patent: 5148548 (1992-09-01), Meche et al.
patent: 5218630 (1993-06-01), Patsiokas et al.
Kuntz Curtis
Lin Mary M.
Nokia Telecommunications Oy
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