GB2420252A

GB2420252A - Communication channel release after period of non-use (hang time) where period (hang time) is variable

Info

Publication number: GB2420252A
Application number: GB0425145A
Authority: GB
Inventors: Malcolm J Young; Grant Michael Emberson
Original assignee: Motorola Inc
Current assignee: Motorola Solutions Inc
Priority date: 2004-11-15
Filing date: 2004-11-15
Publication date: 2006-05-17
Anticipated expiration: 2024-11-15
Also published as: GB0425145D0; GB2420252B

Abstract

A method of operation in a message trunked mode of a trunked communication system (100) comprising a plurality of user terminals (MS 3, MS 5, MS 7) and a controller (17), including the following steps carried out by the controller: <SL> <LI>(i) allocating a communication channel when a first one (MS 3) of the user terminals has requested initiation of a call; <LI>(ii) applying a hang time upon detection that a participant in a call has finished communicating (e.g. speaking) and keeping the channel allocated to the call during the hang time; <LI>(iii) determining if one of the user terminals participating in the call requests during the hang time to continue (e.g. to continue a conversation in) the call; and <LI>(iv) clearing the communication channel if no call continuation request from one of the participating user terminals has been detected and/or granted when the hang time has expired; wherein the controller (17) is operable to apply variable hang times during operation of the system. </SL> Also described are a system and controller for operation of the method.

Description

TITLE: METHOD, SYSTEM ND CONTROLLER FOR USE IN

COMMUNICATIONS

FIELD OF THE INVENTION

The present invention relates to a method, system and controller for use in communications. In particular, it relates to trunked systems including push-to-talk terminals for use in communications, particularly speech communications, and the control of channel use in such systems.

BACKGROUND OF THE INVENTION

In trunked radio communication systems, there is a set of radio traffic channels that can be used for communication between system users. There are not enough channels for each user to have his/her own dedicated traffic channel, so the channels are effectively kept in a pool, or trunked, and are allocated on a request-by- request basis. Once the pool of traffic channels has been emptied then new call requests will have to wait until another current call ends so that a traffic channel becomes available for a new call. There are different algorithms that can be employed by the system controller in order to try to give each user a reasonable access to the shared traffic channel resources. Message trunking' is one such algorithm.

Basically, in message trunking, the radio traffic channel allocated for a particular call remains allocated after someone has stopped speaking, so that if a person needs to reply to a message then the traffic channel will be immediately available. In contrast, if the traffic channel is deallocated when the talker finishes speaking then another call request may obtain use of this free (available) traffic channel; when the person attempts to reply in this case then no channels will be available and the reply will encounter a delay.

This latter mode of operation is called transmission trunking'.

For message trunking, the traffic channel is kept active by a system controller (usually a processor in the system infrastructure) for a period that is termed a hang time' . The hang time runs from when the previous speaker in the call finished speaking. If no-one replies before the hang time expires then the traffic channel will be de-allocated by the system controller.

In a press-to-talk communication system, a voice I.....

* communication call is initiated by a user by operation of a press-totalk switch, or PTT', included on or in the user's communication terminal, e.g. mobile station.

At the start of a new call, the first PTT operation by the user who is the call initiator causes the call to be established and the traffic channel to be assigned (connection to be established) . In message trunked systems, as noted earlier, the traffic channel is kept active after the call initiator has finished speaking.

Therefore subsequent PTT operations in such a system merely request for the user to have permission to speak; the traffic channel, i.e. call connection, is still active from the original call set-up.

In the prior art, the hang time used in message

trunked systems is selectable at system set up but is fixed during system operation. If the hang time selected is too long then, when the participants in a call have finished their conversation, the traffic channel is left allocated to the participants for longer than necessary and traffic channel resources are unnecessarily wasted.

On the other hand, if the hang time selected is too short the call can be cleared down before the participants have finished their conversation.

SUMMARY O THE INVENTION

S S... I...

** 15 The present inventors have appreciated that use of a variable hang time can be beneficial since different *.S...

* hang times will suit different users.

IS....

* According to the present invention in a first aspect there is provided a method of operation in a message trunked mode of a trunked communication system I.....

* comprising a plurality of user terminals and a controller device, including the following steps carried out by the controller device: (i) allocating a communication channel when a calling one of the user terminals has initiated a call; (ii) applying a hang time upon detection or indication that a participant in a call has finished communicating (e.g. speaking) and keeping the channel allocated to the call during the hang time; (iii) determining if one of the user terminals participating in the call requests during the hang time to continue the call (e.g. by further speaking); and (iv) clearing the communication channel if no call continuation request from one of the terminals has been detected when the hang time has expired; wherein the controller device is operable to apply variable hang times during operation of the system.

In the method according to the first aspect of the invention each of the user terminals may include a push to talk switch, PTT', and requests by the user terminals to initiate or continue a call may be by operation by the relevant user of the PTT included on S...

the user's terminal.

15 In the method according to the first aspect of the invention, the controller may apply a first hang time in respect of a request by a terminal which is the first terminal to request continuation of a call which has 5.:.5 been initiated by the calling terminal and a second :" 20 shorter hang time in respect of a subsequent call continuation requests.

Alternatively, or in addition, the hang time may be determined and varied dynamically by the controller. For example, the hang time may be varied according to the parties involved in the call, and/or according to the call type being made and/or according to statistical historical data relating to previous calls in the system and/or according to a user's previous interaction with the system. The hang time may thereby be varied with the aim of optimising traffic channel usage in the system.

In this specification a call' is a communication

between two radio terminals. The communication may to transfer speech information or data (text) or picture or video information or a combination of these types of information. As suggested earlier, various call types are possible. Where the call comprises speech communication the call could be a group call or a private (individual or point to point') call. Where the call comprises a data communication the call could be to transfer packet data or circuit mode data.

For different types of call involving data communication, an appropriate hang time can be derived from the service that is being requested. Users will 0** expect either fast, slow or no response depending on the service. The hang time can be set accordingly.

*:m.. In accordance with the present invention in a second aspect there is provided a communication system comprising a plurality of user terminals each having a push to talk (PTT) switch to permit a speech i:": 20 communication by the user to take place, and a controller operable to apply the following steps within the system: (i) allocating a communication channel when a calling one of the user terminals has initiated a call; (ii) applying a hang time upon detection that a participant in a call has finished communicating and keeping the channel allocated to the call during the hang time; (iii) determining if one of the user terminals participating in the call requests during the hang time to continue the call; and (iv) clearing the communication channel if no call continuation request from one of the terminals has been detected when the hang time has expired; wherein the controller device is operable to apply variable hang times during operation of the system.

In the system according to the second aspect of the invention, the system may comprise a trunked radio system selected from TETRA, APCO 25, PTT over cellular, PTT over internet, and other PTT operated systems. The user terminals may typically comprise radio communication terminals which are mobile stations although they could also comprise fixed terminals including for example computers or digital speech 5Sf S terminals.

" 15 In accordance with a third aspect of the present invention there is provided a controller for use in a communication system comprising a plurality of user terminals each having a push to talk (PTT) switch to permit a communication by the user to take place, the controller being operable to apply the following steps within the system: (I) allocating a communication channel when a first one of the user terminals has initiated a call; (ii) applying a hang time upon detection or indication that a participant in a call has finished communicating and keeping the channel allocated to the call during the hang time; (iii) determining if one of the user terminals participating in the call requests during the hang time to continue the call; and (iv) clearing the communication channel if no call continuation request from one of the other terminals has been detected when the hang time has expired; wherein the controller device is operable to apply variable hang times during operation of the system.

The controller in each of the aspects of the invention referred to above may be a controller similar to those used to apply hang times in the prior art, but operable to apply a variable hang time as described above. Thus, the controller may comprise one or more control signal processors and may be incorporated in a fixed control site in an infrastructure of the system.

Such processor(s) may comprise a suitably programmed microprocessor operating as a digital signal processor/computing device.

By the invention, the hang time can be varied to improve or optimise the usage of traffic channels within * the trunked system. This can result in considerable economic benefit to the operator of the system, :: 20 particularly if the operator derives revenue based on the number of calls per minute made in the system.

The present inventors have appreciated that different hang times may suit different users or users in different situations, e.g. different call types, so the invention, particularly the embodiments wherein the hang time is determined and varied dynamically by the controller based on recorded data relating to previous use of the system or by a user, helps to satisfy users as well as the system operator.

Embodiments of the invention will now be described with reference to the accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing an arrangement of operational units within a trunked mobile communications system embodying the invention.

FIG. 2 is a schematic diagram showing in more detail a controller included in the system of FIG. 1.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

FIG. 1 is a schematic diagram showing an arrangement of operational units within a trunked mobile communications system embodying the invention. The S..

system 1 includes a first MS (mobile station such a portable or mobile radio, mobile telephone or mobile or portable computer terminal) indicated by reference numeral 3, a second MS 5 and a third MS 7. In practice, a system is likely to include many terminals including :": 20 fixed terminals as well as MS5, but the MS5 shown can be considered as representative of the user terminals of the system. The MSs 3, 5 and 7 include respectively PTT switches 9, 11 and 13 to initiate user speech communications. Although the switches 9, 11 and 13 are indicated as conventional mechanical switches they could be any of the switches known in the art including software switches or buttons operated by click of a mouse or voice activated switches. Communications between the MSs 3, 5 and 7 are sent by wireless via a BTS (base transceiver station) 15. The BTS 15 is part of an infrastructure 17 providing connectivity between MSs operating in the system 1 and management and control of operation of the system 1. The infrastructure 17 includes (together with other items not shown) a controller 19 which is operably connected to the BTS 15 and controls operations within the system 1 of the BTS and MSs 3, 5 and 7 and other devices (not shown) Although the controller 17 is shown in FIG. 1 as being separate from the BTS 1 it could be included in the BTS 1.

The system 1 operates in message trunked mode. When a call is to be made by the MS 3 to the MS 5 and MS 7, a call set up request is established by the user of the MS 1 by entering the details of the called MSs 3 and 5 and I...

by pressing a button or key to operate the PTT switch 9.

SS

This action causes the MS3 to send a wireless signal to the BTS 15 which the BTS 15 passes to the controller 17.

The controller 17 interprets the signal as a call set up * request. The controller 17 in response checks the s's.' validity of the request and then makes a communication :: 20 channel available and, via the BTS 15, establishes a link between the MS3 and the MSs 5 and 7. The MS 1 (or alternatively the BTS 15) detects when the user finishes speaking and passes a corresponding signal to the controller 17.

The controller 17 is shown in more detail in FIG. 2. The input signals referred to above are applied to a processor 19 coupled to a memory 21. The processor 19 extracts information from the input signal it obtains when the call is being established, such as the identity of the requesting user or user terminal and the call type being requested. If appropriate, the processor 19 issues a signal indicating that the call set request is granted. This is passed back to the requesting MS 3 via the MS 15. The processor 19 also issues an instruction signal causing the BTS 15 to provide a link between the MS 3 and the MSs 5 and 7 on a suitable channel. When the processor 19 receives a signal to indicate that the user of the MS 1 has finished communicating (e.g. speaking) the processor 19 starts a hang timer 23 running. The processor 19 determines and sets a hang time to be observed by the hang timer 23 based on the information extracted from the call set up request with reference to data held in the memory 21 such as historical use data referred to earlier. If a signal requesting continuation *e** of the call is sent by one of the MSs 3, 5, 7 it is received by the processor 19. If the request is granted, an output signal is sent from the processor 19 via the BTS 15 to the requesting MS indicating that the * requested continuation is granted. A detector 25 watches for output signals from the processor 19 to indicate that a call continuation request has been granted. The detector 25 also watches for expiry of the hang time running in the hang timer 23. If a call continuation request is made and granted before expiry of the hang time, this is detected by the detector 25 and an output signal is sent from the detector 25 to clear the hang timer 23. However, if the detector 25 detects expiry of the hang time running in the hang timer 23 before such a call continuation request is granted, the detector 25 issues an expiry signal and passes this to the processor 19. The processor 19 thereby issues a channel clear down signal causing the communication channel currently used for the call to be cleared down and to be available to another call.

Where the call continuation request is granted by the processor 19 the user of the relevant MS begins communicating, e.g. speaking, to continue the call. The end of his/her message is detected and the cycle is repeated, except that in this case the processor 19 can select a different hang time to run in the hang timer.

At the end of each cycle the memory holding historical data is updated to reflect the transmissions which have just been made.

In order to appreciate the potential benefit to be obtained using a variable hang time in embodiments of s.. the invention, consider a group call of 20 seconds S...

duration made to five different sites and having a fixed hang time of 1 second as in the prior art. If the system controller can determine that the hang time can be * reduced by lOOms without impairing user satisfaction, this will provide a significant channel occupancy saving. In a trunked system that is shared by many calls including point-to-point calls as well as point-to- multipoint calls, then the saving is equivalent to another group call or potentially five single site calls. In terms of billings by the system operator against system capacity used, this is equivalent to a gain of 2. 5%. In other words the improvement provided by the variable hang time could provide a gain of 2.5% in the revenue earned from the use of the system.

Claims

1. A method of operation in a message trunked mode of a trunked communication system comprising a plurality of user terminals and a controller, including the following steps carried out by the controller: (i) allocating a communication channel when a calling one of the user terminals has requested initiation of a call; (ii) applying a hang time upon detection or indication that a participant in a call has finished S...

communicating and keeping the channel allocated to the S...

call during the hang time; (iii) determining if one of the user terminals participating in the call requests during the hang time * to continue the call; and (iv) clearing the communication channel if no call *SIS.S * * 20 continuation request from one of the participating user terminals has been detected and/or granted when the hang time has expired; wherein the controller is operable to apply variable hang times during operation of the system.

2. A method according to claim 1 wherein each of the user terminals includes a push to talk switch, PTT', and requests by the user terminals to initiate or continue a call are by operation of the PTT included on the relevant user terminal.

3. A method according to claim 1 or claim 2 wherein the controller is operable to apply a first hang time in respect of a message by the first terminal to allow continuation of a call begun by the first terminal and applies a second shorter hang time in respect of one or more subsequent messages by another or other terminals.

4. A method according to claim 1, claim 2 or claim 3 wherein the hang time is determined dynamically by the controller.

5. A method according to claim 4 wherein the hang time is varied according to the parties involved in the call.

6. A method according to claim 4 or claim 5 wherein the hang time is varied according to the call type being made.

7. A method according to any one of claims 4 to 6 I...

wherein the hang time is varied according to statistical historical data relating previous calls in the system.

8. A method according to any one of claims 4 to 6 wherein the hang time is varied according to statistical * historical data relating to a user's previous usage of the system. S....

* * 20

9. A method according to any one of claims 4 to 8 wherein the hang time is varied with the aim of optimising traffic channel usage in the system.

10. A communication system comprising a plurality of user terminals each having a push to talk (PTT) switch to permit a communication by the user to take place, and a controller operable to apply the following steps within the system: (i) allocating a communication channel when a first one of the user terminals has requested initiation of a call; (ii) applying a hang time upon detection that a participant in a call has finished communicating and keeping the channel allocated to the call during the hang time; (iii) determining if one of the user terminals participating in the call requests during the hang time to continue the call; and (iv) clearing the communication channel if no call continuation request from one of the participating user terminals has been detected and/or granted when the hang time has expired; wherein the controller is operable to apply variable hang times during operation of the system.

11. A system according to claim 10 wherein each of the user terminals includes a push to talk switch, PTT', operable to allow signals to be generated which represent requests by the user terminals to initiate or continue a call. * *

12. A system according to claim 10 or claim 11 wherein * * 20 the system comprises a trunked radio system selected from TETRA, APCO 25, PTT over cellular, PTT over internet, and other PTT operated systems.

13. A system according to any one of claims 10 to 12 wherein one or more of the user terminals comprises a mobile radio station.

14. A system according to any one of claims 10 to 13 wherein one or more of the user terminals comprises a fixed terminal.

15. A system according to claim 14 wherein the fixed terminal comprises a computer or a digital speech processor.

16. A controller for use in a communication system comprising a plurality of user terminals and a controller, the controller being operable to apply the following steps within the system: (i) allocating a communication channel when a first one of the user terminals has requested initiation of a call; (ii) applying a hang time upon detection that a participant in a call has finished communicating and keeping the channel allocated to the call during the hang time; (iii) determining if one of the user terminals participating in the call requests during the hang time to continue the call; and (iv) clearing the communication channel if no call continuation request from one of the participating user terminals has been detected and/or granted when the hang * * time has expired; wherein the controller is operable to apply variable * 20 hang times during operation of the system.

17. A method according to any one of claims 1 to 9 and substantially as herein described with reference to the accompanying drawings.

18. A system according to any one of claims 10 to 15 and substantially as herein described with reference to the accompanying drawings.

19. A controller according to claim 16 and substantially as herein described with reference to the accompanying drawings.