GB2332823A

GB2332823A - Sequential selection of control channels for call attempt

Info

Publication number: GB2332823A
Application number: GB9727323A
Authority: GB
Inventors: Gil-Jae Park
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 1997-12-29
Filing date: 1997-12-29
Publication date: 1999-06-30
Also published as: KR19990062532A; GB9727323D0

Abstract

A mobile radio terminal detects 333 a plurality of control channels having a received field strength above a predetermined limit e.g. -90dBm and when attempting a call, tunes to the detected control channels in sequence, starting with the channel having the greatest received field strength. Thus, if the associated base station is busy, the terminal tunes to the next control channel 342 until either the call is successful 339 or all the channels have been tried unsuccessfully. If all the channels have failed, a busy tone is generated 343 until an end key on the terminal is operated. The terminal then returns to stand-by mode. The field strength of at least 30 channels may be checked 332 and preferably, at least three control channels exceeding the predetermined limit are detected. The received field strength information may be updated 335 during checking for call requests.

Description

RE-CALLING IN MOBILE RADIO TERMINAL EOUIPMENT BACKGROUND OF THE INVENTION This invention relates to re-calling in a mobile radio terminal equipment in a mobile communication system.

Usually, mobile radio terminal equipment, which continually check control channels in standby mode, tune to the channel having the greatest received field strength when a call is requested by the user. This operation is periodically repeated, thus information on the channel having the greatest received field strength is continually updated.

The terminal equipment waits for a paging signal or performs a call request through this channel. In this case, the tuned channel is a channel of the base station located closest to the terminal equipment.

As illustrated, if the mobile radio terminal equipment requests a call and the relevant base station is not busy, the call is connected, allowing a normal conversation.

However, if the base station is busy, the call fails and the terminal equipment begins automatically re-calling at predetermined intervals for a predetermined period of time.

The following is a detailed description of the configuration of such mobile radio terminal equipment and its automatic re-calling method.

FIG. 1 is a schematic block diagram of conventional mobile radio terminal equipment. As illustrated, a controller 111 controls the overall operation of the mobile radio terminal. A first memory 112 stores program and initial service data. An electrically erasable programmable read only memory (EEPROM) is used for the first memory 112. A second memory 113 temporarily stores data generated during the operation of the mobile radio terminal. The second memory 113 is implemented using random access memory (RAM).

A key input unit 114 is used to input data for dialling and setting the various modes of the mobile radio terminal and to send the data to controller 111. A logic circuit transmits and receives the data for controlling the operation of the controller 111 and the mobile radio terminal equipment, generating control data for controlling the operation of each component of the terminal equipment.

A data processor 116 transmits and receives data to and from controller 111. Specifically, data processor 116 processes the signal with the received data, RXD, which is output from a radio frequency (RF) receiver 120, before applying it to the controller 111. The data processor 116 also processes the signal with the transmitting data, TXD, which is output from the controller 111, before sending it to an RF transmitter 121.

The RF receiver 120 includes a low noise amplifier, a mixer, an intermediate frequency amplifier and a demodulator. The RF transmitter 121 includes a modulator, a power amplifier and an output (or power) controller. The data processor 116 can be a digital signal processor. A duplexer 122 connected to an antenna separates the RF signal to be transmitted from the received RF signal. The RF receiver 120, which is connected to duplexer 122, performs frequency conversion and demodulation of the received RF signal before outputting it.

The received voice signal, RXA, output from the RF receiver 120, is sent to a voice processor 117. The received data, RXD, is sent to the data processor 116. The voice processor 117 generates an audio signal corresponding to the received voice signal, RXA and generates the voice signal, TXA, to be transmitted. The RF transmitter 121 receives the transmitting voice signal, TXA, from voice processor 117 and transmitting data, TXD, from data processor 116 and modulates them for transmission before sending them to the duplexer 122.

A frequency synthesizer 119 generates synthesized frequency signals for assigning the receiving channel for the RF receiver 120 and the transmitting channel for the RF transmitter 121 in response to the control data from the logic circuit 115. A display unit 134 shows the operating state of the mobile radio terminal. The voice processor 117 is connected to a microphone 130 and a speaker 132.

FIG. 2 is a flow chart of a conventional re-calling method of a mobile radio terminal. Once the power to the terminal equipment is turned on, controller 111 goes to stand-by mode (step 211). The control channels are checked to find the channel having the greatest receiving field strength (step 212). The terminal equipment tunes to the channel having the greatest receiving field strength (step 213) and then the data regarding the receiving field strength is updated (step 214). The controller 111 checks if there are any call requests (step 215). If there is a call request at step 215, calling is attempted in response to the call request (step 216).

Whether or not the base station at the serving site is busy is checked (step 217): the value of the bit indicative of the busy state is "1". If the base station is not busy (i.e. the busy state bit is "0"), the call can be successfully completed (step 218) and talk mode is activated (step 219). If the base station is busy, a busy tone is generated and output via the speaker 132 (step 220). The controller 111 checks if an end key is entered (step 221). If the entry of the end key is detected at step 221, the busy tone is stopped and the procedure terminates.

Then the mobile radio terminal equipment goes into the stand-by mode.

As illustrated, conventional mobile radio terminal equipment repeatedly attempts re-calling only to its home base station. Consequently, repeated re-calling attempts end in failure when the home base station is continually busy. This decreases the call completion rate regardless of the performance of the terminal equipment.

SUMMARY OF THE INVENTION An objective of the present invention is to provide an improved call connection attempt procedure to allow an increase in the call completion rate.

Accordingly, the present invention provides a mobile radio terminal comprising: means for detecting a plurality of control channels having a received field strength which exceeds a predetermined limit; and means for sequentially tuning to the detected control channels beginning with the channel having the greatest received field strength, when attempting a call.

Preferably, the terminal further comprises means for generating a busy tone when call attempts using all the control channels end in failure.

Preferably, the means for generating the busy tone is adapted to stop the busy tone when an end key of the terminal is operated.

Preferably, the means for detecting the plurality of control channels is adapted to detect at least three control channels.

Preferably, the predetermined limit is -9OdBm.

The present invention also provides a method of operating a mobile radio terminal comprising: detecting a plurality of control channels having a received field strength which exceeds a predetermined limit; and sequentially tuning to the detected control channels beginning with the channel having the greatest received field strength, when attempting a call.

Preferably, the method comprises: tuning to the channel having the greatest receiving field strength amongst the detected control channels; and sequentially tuning to the next of the detected control channels and re-calling if the base station is busy when a call is attempted in response to a call request.

The method may further comprise updating the received field strength information whilst checking for call requests.

Preferably, the method further comprises generating a busy tone if call attempts using all the detected control channels end in failure.

The method may further comprise stopping the busy tone when an end key of the terminal is operated.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will now be described by way of example with reference to the accompanying drawings in which: FIG. 1 is a schematic block diagram of a conventional mobile radio terminal equipment; FIG. 2 is a flow chart of a conventional re-calling method of the mobile radio terminal equipment; and FIG. 3 is a flow chart of the automatic re-calling method according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in FIG. 3, once the mobile radio terminal equipment is turned on, the controller 111 goes into standby mode (step 331). Control channels are checked and one or more control channels (e.g. three; variable N in FIG. 3), where the received field strength exceeds a predetermined limit (e.g. -9OdBm), are detected (step 332). At least 30 channels are checked. The variables describing the detected control channels are stored (step 333). The channel having the greatest receiving field strength among the multiple control channels stored is tuned to (step 334).

Next, the data regarding the receiving field strength is updated (step 335). The controller 111 then checks for call requests (step 336). If there is a call request at step 336, calling is attempted in response to the call request (step 337). Whether or not the base station at the service site is busy is checked (step 338): again the value of the bit indicative of a busy state is '1'. If the base station is not busy, the call can be successfully completed (step 339) and talk mode is activated (step 340). If the base station is busy, the variable, N, is checked to determine whether it exceeds 3 (step 341). If variable N does not exceed 3, the next channel is tuned to (step 342). The procedure then returns to step 337 to sequentially recalling using the stored control channels.

The above process is repeated until the variable, N, becomes 4. If the variable, N, is 4, that is, all the recalling attempts to tune to the control channels end in failure, a busy tone is generated and output via the speaker 132 (step 343). The controller 111 checks if the end key is input (step 344). If the input of the end key is detected, the busy tone is stopped and the operation terminates. The mobile radio terminal equipment returns to the stand-by mode.

As illustrated, the present invention provides a procedure allowing terminal equipment to try re-calling alternative adjacent base stations when the terminal equipment fails to complete the call due to the busy state of the closest a base station in the mobile communication system, thus increasing the call completion rate.

Claims

CLAIMS 1. A mobile radio terminal comprising: means for detecting a plurality of control channels having a received field strength which exceeds a predetermined limit; and means for sequentially tuning to the detected control channels beginning with the channel having the greatest received field strength, when attempting a call.
2. A mobile radio terminal according to claim 1 further comprising means for generating a busy tone when call attempts using all the control channels end in failure.
3. A mobile radio terminal according to claim 2 in which the means for generating the busy tone is adapted to stop the busy tone when an end key of the terminal is operated.
4. A mobile radio terminal according to any preceding claim in which the means for detecting the plurality of control channels is adapted to detect at least three control channels.
5. A mobile radio terminal according to any preceding claim in which the predetermined limit is -9OdBm.
6. A method of operating a mobile radio terminal comprising: detecting a plurality of control channels having a received field strength which exceeds a predetermined limit; and sequentially tuning to the detected control channels beginning with the channel having the greatest received field strength, when attempting a call.
7. A method of operating a mobile radio terminal according to claim 6 comprising: tuning to the channel having the greatest receiving field strength amongst the detected control channels; and sequentially tuning to the next of the detected control channels and re-calling if the base station is busy when a call is attempted in response to a call request.
8. A method of operating a mobile radio terminal according to claim 7 further comprising updating the received field strength information whilst checking for call requests.
9. A method of operating a mobile radio terminal according to any one of claims 6-8 further comprising generating a busy tone if call attempts using all the detected control channels end in failure.
10. A method of operating a mobile radio terminal according to claim 9 further comprising stopping the busy tone when an end key of the terminal is operated.
11. A mobile radio terminal substantially as described with reference to FIG. 3 of the accompanying drawings.
12. A method of operating a mobile radio terminal, the method being substantially as described with reference to and/or as illustrated in FIG. 3 of the accompanying drawings.