PUSH-TO-TALK MOBILE COMMUNICATIONS SYSTEM, METHOD AND TERMINAL

The present invention relates to mobile communications systems, and in particular, but not exclusively, to the TETRA (TErrestrial Trunked RAdio) system.

In many mobile communications systems, particularly so-called private mobile radio systems for use, for example, by the emergency services, such as the TETRA system, a user wishing to transmit may have to press and hold down a so-called Push-To-Talk (PTT) key on their terminal (e.g. handset) in order to allow the user's speech to be transmitted over the air. For example, group calls made using TETRA radio equipment normally require a user to press and hold down a Push-To-Talk key when the user wishes to transmit over the air.

However, the Applicants have recognised that there may be situations where the need for a user to press and hold a push-to-talk key in order to transmit is impractical and/or undesirable, such as, for example, if the user is driving, or engaged in activity where he or she does not have a free hand to operate the terminal, and/or it is desired for a radio to be kept in transmission in order to, e.g., monitor ambient audio signals , etc ..

The Applicants believe therefore that it would be desirable for a terminal of a mobile communications system to be able to be operable to transmit without the need to press and hold down a push-to-talk key.

The Applicants have further recognised that in such an arrangement, it would be desirable for other users of the system to still be able to access and take over the communications channel that the terminal is transmitting

on, for example if circumstances or the situation so dictates .

According to a first aspect of the present invention, there is provided a communications terminal for a mobile communications system, comprising: ^{■ 1} means for transmitting a request to transmit together with an associated transmission priority setting; and means for, in response to the request to transmit being granted, transmitting on the allocated transmission channel without the need for a user to press or hold a key of the communications terminal.

According to a second aspect of the present invention, there is provided a method of operating a communications terminal of a mobile communications system, comprising: the communications terminal: transmitting a request to transmit together with an associated transmission priority setting; and in response to the request to transmit being granted, transmitting on the allocated transmission channel without the need for a user to press or hold a key of the communications terminal .

According to a third aspect of the present invention, there is provided a communications terminal of a communications system having a mode of operation in which the terminal will transmit without the need for a user to press or hold a key of the communications terminal and comprising means for associating its transmission in this mode of operation with a particular level of priority.

In the present invention, a mobile communications terminal can be arranged to transmit on an allocated transmission channel without the need for a user to press or hold a key (such as a push-to-talk key) . This

facilitates, for example, hands-free transmission using the terminal .

Moreover, in the present invention, the communications terminal can associate its transmissions in this mode of operation with a particular priority level, for example, by including the priority level in its initial transmission (call) request. This facilitates for example, allowing other communications terminals to take over the transmission channel allocated to the terminal operating the manner of the present invention, for example if they make a "higher priority" call request. This can avoid, for example, the terminal operating in the manner of the present invention occupying the transmission channel to the exclusion of all other users (which may, e.g., be undesirable, particularly if, for example, the terminal is left continuously transmitting for a relatively long period of time) .

Thus, the present invention provides an arrangement whereby a communications terminal can, in effect, be placed in a permanent transmitting state so that a user does not have to keep pressing a PTT button to keep the terminal transmitting. This may be useful where, e.g., a user requires hands-free "operation but needs to maintain radio contact. Moreover, other users can still use the radio channel or participate in the call, by making higher priority requests to that effect.

The operation of a communications terminal in the manner of the present invention can preferably be activated by the user of the terminal, for example by them making an appropriate (local or direct) input to the terminal, such as pressing a key or combination of keys, or giving a voice command to the terminal, etc.. In a preferred embodiment, such a local or direct input to the terminal can preferably be made via a detachable and/or removable control unit, that can,

e.g., and preferably, be coupled to the terminal either physically, e.g., via a cable, or via a short range radio connection (such as and preferably Bluetooth) and/or via a near-field wireless' connection (such as and preferably an inductive loop) .

In this case a user may couple the control unit to the terminal for the purpose of configuring and/or setting up the terminal to operate in the mode of operation of the present invention (for example using a key or keys of the control unit) , but then remove the control unit before the terminal is actually used (i.e. such that the terminal will be used without the control unit (controller) attached or coupled to it) . In this case, as will be discussed further below, the terminal once so-configured and setup via the control unit, preferably automatically operates in the manner of the present invention once it is powered up (e.g. by switching it on or by attaching a battery) and, preferably, remains in this mode of operation across power interruptions (e.g. when it is switched off), until it is set to stop such operation (e.g. via the control unit) .

In a particularly preferred embodiment, the mode of operation of the present invention can also or instead (and preferably also) be invoked remotely, by a remote user sending a command to the communications terminal, for example and preferably by over the air signalling, such as by sending a command message (e.g. a short message, such as an SDS message or a packet data message) to the communications terminal. Where a remote command message is used, then that message could and preferably does include the destination identity (group or individual) to which the terminal should address the "permanent transmit" call, and/or any other parameters needed to control aspects of the call, such as maximum transmit power and DMO frequency.

Accordingly, in a particularly preferred embodiment, a system infrastructure of the mobile communications system comprises means for transmitting an instruction (e.g., and preferably, over the air interface (of the communications system), and/or, e.g., and preferably, from a remote user) to the communications terminal to enter a mode of operation in which the terminal will transmit without the need for the user (of the terminal) to press or hold a key (e.g. push-to-talk button) of the terminal.

In response to the instruction to operate in the manner of the present invention, which, as discussed above, can be from a user of the terminal and/or from a remote user, the communications terminal preferably, again as discussed above, transmits an appropriate call request to the communications system and then, once it is assigned a transmission channel, proceeds to transmit on the channel without requiring the user to press- and hold down the push-to-talk button. The call request (request to transmit) can take any desired and suitable form. It preferably indicates that the terminal wishes to transmit in the manner of the present invention (i.e. to transmit on the channel without requiring the user to press or hold down a key (e.g. a push-to-talk button) of the terminal) . In a preferred embodiment, the request to transmit (the call request) has a particular, preferably predefined or predetermined, format for indicating this. Thus, in a preferred embodiment, the terminal will transmit a predetermined request to transmit (a request to transmit having a particular, preferably predetermined, form) together with the desired transmission priority setting, when it wishes to transmit in the manner of the present invention. The instruction to operate in the mode of the present invention preferably causes the terminal to set

up a call or to convert an ongoing call to operate in the manner of the present invention.

In a particularly preferred embodiment, once the terminal has been instructed to operate in the mode of the present invention, it will automatically request permission to transmit (a call request) (e.g. and preferably whenever a channel is available to do so) , and once permission to transmit (a channel) is granted, then transmit continuously until interrupted or instructed to stop.

Where the communications system can operate either via the communications system infrastructure (e.g. in a trunked mode) , or via a "direct" (terminal-to-terminal) mode of operation, as is the case for a TETRA system, then the operation in the manner of the present invention can preferably be set up and carried out in either and both modes of operation. For example, the call requests could be transmitted in the required format for, e.g., voice and data trunked mode operation, or direct mode operation, as appropriate.

The priority setting that is associated with the call can be set as desired. It is preferably a selected, preferably predetermined, priority setting. In a preferred embodiment, the initiating entity (local or remote user) can set the priority for the call. Most preferably the call in the manner of the present invention is associated with a relatively low priority, as that will then help to avoid the call "hogging" the transmission channel. As discussed above, in a particularly preferred embodiment, the call of the present invention can be interrupted by another user making a higher priority request to transmit or participate in the call.

This can be achieved in any suitable manner,. For example, in a TETRA system, as a transmitting terminal can still in any event receive downlink signalling, the

terminal can be commanded to stop transmitting by the system infrastructure to allow a higher priority speaker in the present call, or a user wishing to make a different, higher priority call, to take over the channel .

In a particularly preferred embodiment, if a terminal operating in the manner of the present invention has its call interrupted, it preferably monitors the channel and determines when the channel becomes free again (is not occupied by other transmissions) and then resumes its "hands-free" transmission on the channel, for example, and if necessary, by retransmitting a call request on or for the channel. In this way, the terminal will, in effect, only relinquish the channel temporarily, whilst the interrupting call is in progress. Thus, after an interruption, the terminal preferably reattempts transmission in the manner of the present invention.

Thus in a preferred embodiment, the communications terminal, if the transmission is interrupted by another transmission, will automatically attempt to resume and/or re-establish (and will resume or re-establish) its transmission after the interruption has finished. In such arrangements, when the communications terminal is interrupted, for example by a higher priority call, the existing, "non-PTT" call in the manner of the present invention, could, for example, continue but with the system allowing the other user to transmit, or, for example, the "non-PTT" call could be cleared down and then set up again once the "interruption" has finished.

The call of the present invention may also be cleared and set up again if the terminal determines or observes that one or more parameters of the call need to be adjusted or changed. For example, the destination

address of the call and/or the call mode may have to be changed.

Preferably, in such arrangements, the terminal obtains, preferably automatically, information to change or adjust the one or more parameters of the call as required, e.g. from the system infrastructure and/or from data stored in the terminal itself.

Thus in a particularly preferred embodiment, when it is determined or observed by the terminal that one or more parameters of the call need to be adjusted or changed, the existing "non-PTT" call in the manner of the present invention is cleared, the call parameter then changed or adjusted (e.g. and preferably using information automatically obtained by the terminal) and the call set up once again using the new, modified call parameter or parameters .

In a particularly preferred embodiment the terminal will remain in the mode of operation of the present invention even if it is switched on and off again, and/or (and preferably also) if its power supply is interrupted (e.g. and especially if its battery is removed and replaced) . Indeed, it is particularly preferred for the terminal to automatically revert to this mode of operation over power cycles, e.g., when the battery is removed and replaced, when it is in this mode of operation, rather than, e.g., reverting to a different mode of operation when the power is interrupted. Thus, for example, the terminal will preferably automatically request the call set-up of the present invention as soon as it has powered up again (and, e.g. registered and obtained any required encryption keys) , if there is a power interruption while the terminal is operating or set-up in the manner of the present invention. Thus, in a particularly preferred embodiment, the terminal will remain in the mode of operation of the

present invention, even if the terminal is powered off (whether, e.g., due to it being switched off, or its power supply being interrupted (e.g. its battery being removed) (and resume such operation automatically immediately it is powered on again) .

In a preferred embodiment, the terminal can be switched out of its operation in the manner of the present invention (i.e. the "permanent transmit" call cleared) , for example, and preferably, by a local or remote user giving an appropriate instruction or input to the terminal . Most preferably only the initiating entity (e.g. local or remote user) can deactivate the operation of the terminal in the manner of the present invention (and the terminal preferably otherwise remains in this operating mode, e.g. as discussed above, even through power interruptions) .

The present invention can be applied to any form of call, although as will be appreciated by those skilled in. the art, it will be particularly applicable to and preferably applied to group calls. It may be particularly applicable where, e.g., most of the activity in a group call takes place between two people, the user invoking the operation of the present invention and a dispatcher or controller. The communications terminal can take any suitable or desired form. It is preferably a mobile terminal (mobile station) of a mobile communications system. The mobile s _; tation may, e.g., be portable or, e.g., vehicle mounted, etc., as is known in the art. The various processes, etc., of the present invention to be carried out in or by the system infrastructure can be performed in any suitable and desired components of the system infrastructure and/or terminal (e.g. mobile station). The communications system of the present invention can be any suitable such system. The present invention

is particularly, but not exclusively, applicable to mobile communication systems, such as the TETRA system. Thus the present invention also extends to a communications terminal and to a method of operating a communications terminal of a mobile communications system, and to a mobile communications system and a method of operating a mobile communications system, that is in accordance with and/or that can be operated in accordance with, the present invention. The mobile communications system is preferably a TETRA system and the communications terminal is preferably a TETRA terminal .

As will be appreciated by those skilled in the art, ¹ ' all of the aspects and embodiments of the ¹ present invention described herein can and preferably do include, as appropriate, any one or more or all of the preferred and optional features of the invention described herein.

The methods in accordance with the present invention may be implemented at least partially using software e.g. computer programs. It will thus be seen that when viewed from further aspects the present invention provides computer software specifically adapted to carry out the method or a method herein described when installed on data processing means, a computer program element comprising computer software code portions for performing the method or a method herein described when the program element is run on data processing means, and a computer program comprising code means adapted to perform all the steps of a method or of the methods herein described when the program is run on a data-processing system. The invention also extends to a computer software carrier comprising such software which when used to operate a communications system or terminal comprising data processing means causes in conjunction with said data processing means said system

or terminal to carry out the steps of the method of the present invention. Such a computer software carrier could be a physical storage medium such as a ROM chip, CD ROM or disk, or could be a signal such as an electronic signal over wires, an optical signal or a radio signal such as to a satellite or the like.

It will further be appreciated that not all steps of the method of the invention need be carried out by computer software and thus from a further broad aspect the present invention provides computer software and such software installed on a computer software carrier for carrying out at least one of the steps of the methods set out herein.

The present invention may accordingly suitably be embodied as a computer program product for use with a computer system. Such an implementation may comprise a series of computer readable instructions either fixed on a tangible medium, such as a computer readable medium, for example, diskette, CD-ROM, ROM, or hard disk, or transmittable to a computer system, via a modem or other interface device, over either a tangible medium, including but not limited to optical or analogue communications lines, or intangibly using wireless techniques, including but not limited to microwave, infrared or other transmission techniques. The series of computer readable instructions embodies all or part of the functionality previously described herein.

Those skilled in the art will appreciate that such computer readable instructions can be written in a number of programming languages for use with many computer architectures or operating systems. Further, such instructions may be stored using any memory technology, present or future, including but not limited to, semiconductor, magnetic, or optical, or transmitted using any communications technology, present or future, including but not limited to optical, infrared, or

microwave. It is contemplated that such a computer program product may be distributed as a removable medium with accompanying printed or electronic documentation, for example, shrink-wrapped software, pre-loaded with a computer system, for example, on a system ROM or fixed disk, or distributed from a server or electronic bulletin board over a network, for example, the Internet or World Wide Web.

A number of preferred embodiments of the present invention will now be described by way of example only. The preferred embodiments of the invention will be described with particular reference to a TETRA mobile communications system. However, as discussed above, while the present invention is particularly applicable to TETRA mobile communications systems, as will be ^■ appreciated by those skilled in the art, it is not exclusive to those systems and can be applied to other mobile communications systems and communications systems equally. In the present embodiment, a mobile terminal

(station) of a TETRA communications system has three soft keys, "Permanent Transmit Toggle", "Activate Permanent Transmit" and "Deactivate Permanent Transmit" . When the "permanent transmit call" state is not active and the "permanent transmit toggle" or "activate permanent transmit" soft key function is invoked, the terminaL' enters the "permanent transmit call" state.

When the "permanent transmit call" state is active and a channel is available and unoccupied, the radio automatically requests transmission with low Tx

Priority. In TETRA voice + data mode this is done using the U-TX DEMAND PDU. In direct mode (either via a gateway or not) a DM-(G)TX REQUEST and/or DM-(G)PREEMPT PDU is used.

If transmission is granted, the terminal behaves as if the PTT was continuously pressed, until the transmission is interrupted.

If there is an ongoing half duplex call, permanent transmit is applied on that call for both TMO and DMO. Otherwise, a new half duplex call is setup on the presently selected talk group or individual identity, if any (depending on the terminal being in Individual or Group mode) , or the call is set up on the group or individual identity included in the remote command message, using any other parameters included with the command such as maximum transmit power and DMO frequency.

If the transmission gets interrupted, after the interruption, when the communications channel is available and unoccupied, the terminal automatically re-requests transmission as defined above.

The terminal exits the "permanent transmit call" state, and clears the call, if: • the user explicitly clears the call using the

Clear key or invoking the "Reject or exit from call" soft key function; or

• the user implicitly clears the call by performing a user-interface action that results in clearing the call.

The terminal exits the "permanent transmit call" state, and stays in the call, if:

• the "permanent transmit toggle" or "deactivate permanent transmit" soft key function is invoked when the terminal is already in

"permanent transmit call" state, or;

• the PTT is pressed.

A permanent transmit call is also preferably automatically cleared and re-set up if the terminal observes that the destination address or call mode has to change (which could, e.g. happen if a terminal using

direct mode operation notices that it has gone out of range of the gateway it has been using, and has to switch to working through a different gateway or to working mobile station to mobile station (i.e. without using the gateway) ) .

Other arrangements and enhancements would be possible.

For example, the terminal could also or instead be set into the "permanent transmit call" state by a user attaching to the terminal a control unit with buttons that allow the terminal to be set-up, configured, etc., and using- the control unit to set the terminal in the "permanent transmit call" state. The control unit would then be removed, and the terminal used without the control unit attached, with the terminal automatically assuming the set "permanent transmit call" state when it is powered up (e.g. by switching it on or attaching a battery) (i.e. such that if the control unit is detached, from the terminal after the terminal has been set into the "permanent transmit call" state, the terminal remains in that state) .

In this case, the detachable control unit may have "hard keys" or "soft keys" for controlling the terminal in this manner, and may, e.g., be connected (coupled) to the terminal by a cable, by a short range radio connection (e.g. Bluetooth), and/or by a near-field wireless connection (e.g. an inductive loop), etc.. If Whisper Mode is enabled, it preferably gets activated/deactivated when the terminal enters/exits the "permanent transmit call" state.

The permanent transmit soft key function preferably has no effect if invoked when the terminal is participating on a full duplex call .

Activation of the Permanent Transmit soft key function preferably overrides the live microphone functionality of an alarm call.

When the terminal switches on and successfully attaches to/selects a TMO/DMO talk group after initial talk group request, the permanent transmit function can preferably be automatically invoked, for example by setting a parameter to indicate that operation.

When the "permanent transmit call" state is active, the terminal preferably informs the user of that fact, for example by means of an appropriate display.