SYSTEM

BACKGROUND

Embodiments presented herein relate to methods, wireless communication devices, computer programs, and a computer program product for transmission control in a group communications system.

In group communications (GC) systems, there may be a challenge to obtain good performance and capacity for a given communications situation, e.g. depending on the physical environment in which the communications system is deployed.

In general terms, group communication requires that the same information is delivered to multiple clients. In GC systems (e.g. Push-To-Talk (PTT) systems or similar) the clients receiving the same media constitute a group of clients, which maybe called a communication group. In a GC system there is usually but not always only one user that is allowed to transmit data (e.g. voice or video) at a certain time.

In a GC system there is typically a transmission control function present, also known as floor control function. The transmission control function enables the clients in the GC system to request certain capacity of the shared resources used to transmit data in the system. The transmission control function usually needs a Transmission Arbitrator (TA), also known as floor arbitrator. The TA decides on which client(s) that is/are currently allowed to transmit data in a

communication group. Typically, a transmission control process performed by the transmission control function starts with a client that wish to transmit and therefore sends a transmission request (or floor request) message to the TA. If there are available resources the TA grants the client the right to transmit by sending a transmission grant message (e.g. a floor grant message). The TA also sends a transmission arbitrator taken (TA taken) message (e.g. a floor taken message) to the group of clients that have announced interest in the specific communication group.

The transmission control or floor control function in a Mission Critical (MC) system usually includes other and/ or additional features than those indicated above. For example, it may allow and in that case control simultaneous transmissions from different GC clients. The transmission control function may also include override/pre-emption capabilities, which can be used when a client with higher priority (e.g. a dispatcher) needs to interrupt a current transmission from another client. In that case the transmission grant or floor grant can be revoked from the client that is currently transmitting. Another function of a transmission control may be queuing. This can be used when there are more clients requesting to transmit than the maximum number of simultaneous transmissions allowed and/ or supported by the TA. In that case the TA may grant the client to transmit according to a certain queue order or similar.

In a GC system there is usually a network based GC control node. This GC control node could e.g. implement the functionality of a group communication service application server (GCS AS) and be a MC service server. Typically, it is the GCS AS that implements a floor control server. GC can also be used in off -network operational mode. Off -network operational mode means that the group communication clients (that resides in wireless communication devices, WCD) transmit data directly to other wireless devices in proximity, without using any network infrastructure such as radio base stations or similar. The off -network mode is also known as Direct Mode Operation (DMO) or Device to Device (D2D).

In off -network operational mode one of the GC clients must take the TA role in the communication group. This can be done with different approaches. One way is to decide on one specific GC client which is assigned to take the TA role. This client remains as a TA for the group communication ongoing in the off-network mode (this approach is known as single-arbitrator). An alternative is that the transmitting client takes the TA role and keep the role until someone else is granted the permission to transmit. When another client is granted the permission to transmit, that client becomes the TA (this is known as self- arbitration).

Figure lB illustrates a known exemplifying transmission control procedure using self-arbitration. There is no ongoing data being transmitted when GC service client 1 requests to transmit in step 1. If no response is detected, the GC service client ι will take the TA role in step 2 and send a TA taken to the other GC clients in step 3. Additional transmission from any client during the media flow (step 4) will be either rejected, queued or granted by the TA (i.e. GC service client 1).

The challenge with GC in off-network operational modes, is to decide which GC client shall take the TA role. If the TA role is given to one specific client in a single-arbitrator approach, the GC depends on that client. If that client is shutdown/logs out or moves out of radio coverage related to the other clients in the communication group the communication will need a new TA. The other approach known as self-arbitration may continue to work even if the current TA client is shutdown etc. However, using self-arbitration will give an unpredictable behavior when the clients are distributed in an area, and not all the clients are in continuous proximity (for radio transmission/reception) of all other clients in the communication group.

Figure 2 illustrates an exemplifying number of Group Communication (GC) clients that are geographically distributed. The dashed circle R200 represents the broadcast area for GC client R, the dotted circle G200 represents the broadcast area for GC client G and the dashed-dotted circle P200 represents the broadcast area for GC client P. Now, assume that GC client P requests the right to transmit and thus to take over the role as TA in a self-arbitration scheme. There will then be an unpredictable behavior, since at least some GC clients, marked with a solid oval OV200 in figure 2, are outside the dash-dotted circle P200 and will thus not be able to receive the request to transmit and thus not able to receive any subsequent data from GC client P. It follows that some more remote GC clients in the dashed circle R200 (c.f. the clients in OV200) may not be aware of that GC client P now acts as TA and may thus start one or more simultaneous transmissions. This will cause interference and it may even cause other GC clients to assume the TA role despite that GC client P has already assumed the TA role. The interference issue may also occur in single-arbitration approach but may in that case be under better control.

Hence, there is a need to improve the method of choosing the right TA at the right moment in time.

SUMMARY

An object of embodiments herein is to improve the method of choosing a transmission arbitrator (TA) for transmission control in a group communication (GC) system.

According to a first aspect there is presented a method for transmission control in a group communications system. The method being performed by a first group communication (GC) wireless communication device (WCD) (e.g. a WCD belonging to a certain communication group) currently acting as a transmission arbitrator (TA) for a plurality of group communication wireless communication devices (GC WCDs). Generally, the WCD maybe any kind of suitable WCD. The method comprises: receiving, from a second GC WCD, a transmission request comprising location information indicating the location of the second GC WCD; and evaluating, based on the location information, if the second GC WCD can be approved as a new TA. According to a second aspect there is presented a GC WCD for transmission control in a GC system. The first GC WCD comprises processing circuitry configured to cause the first GC WCD to perform a set of operations causing the first GC WCD to act as a current TA for a plurality of GC WCDs and causing the first GC WCD to: receive, from a second GC WCD, a transmission request comprising location information indicating the location of the second GC WCD; and evaluate, based on the location information, if the second GC WCD can be approved as a new TA.

It is preferred that the first GC WCD and the second GC WCD are peer WCDs, e.g. such that they are of the same kind or at least are configured to operate in the same manner with regards to the group communication.

To use the location as input to decide on which GC WCD that should be the TA gives a more predictable behaviour of the communication and it is not dependent on if one specific device leaves the area or the group communication session or similar.

Group communication in off -network operation with a WCD as TA is typically applicable when the normal network infrastructure is not reliable or when the WCDs are out of coverage of the network. For example, in a mission critical scenario, such GC may be applicable for Public Safety users in one specific incident area and it will then be a clear advantage if the location of incident is used to decide on which GC WCD that should acts as a TA. One WCD that is far away from the center of the incident is less suitable to be the TA than a WCD that is closer to the center of the incident.

Generally, all terms used in the disclosure are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a/an/the element, apparatus, component, means, step, etc." are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated.

BRIEF DESCRIPTION OF THE DRAWINGS

The proposed solutions are now described, by way of example, with reference to the accompanying drawings, in which:

Fig. lA is a schematic diagram illustrating a communications system according to embodiments;

Fig. lB illustrates a known exemplifying transmission control procedure using self-arbitration; Fig. 2 illustrates an exemplifying number of Group Communication (GC) clients that are geographically distributed;

Fig. 3A and 3B are flowcharts of methods according to embodiments;

Fig. 4 is a signalling diagram according to an embodiment;

Fig. 5A and 5B are schematic diagrams showing functional modules of a client node according to an embodiment;

Fig. 6 shows one example of a computer program product comprising computer readable means according to an embodiment.

DETAILED DESCRIPTION

The proposed solutions will now be described more fully hereinafter with reference to the accompanying drawings, in which certain embodiments are shown. These proposed solutions may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the proposed solutions to those skilled in the art. Like numbers refer to like elements throughout the description. Any step or feature illustrated by dashed lines should be regarded as optional.

Figure lA is a schematic diagram illustrating a communications system 100 where embodiments presented herein can be applied. The communications system 100 is assumed to provide services for group communication and may hence be regarded as a group communications (GC) system. The GC system 100 maybe a push to talk (PTT) system or similar.

The communications system 100 comprises at least two client nodes 400a, 400b and may comprise at least one control node 200. The at least one control node 200 maybe provided in, or installed on, a radio access network node 110 or in another entity or device in a radio access network 120, in an entity or device of a core network 130, or in an entity or device of a service network 140. Each client node may be provided in, or installed on, a respective wireless communication device 150a, 150b.

Examples of WCDs 150a, 150b include, but are not limited to, mobile stations, mobile phones, handsets, wireless local loop phones, user equipment (UE), smartphones, laptop computers, and tablet computers. Examples of radio access network nodes 110 include, but are not limited to, radio base stations, base transceiver stations, node Bs, evolved node Bs, and access points. As the skilled person understands, the communications system 100 may comprise a plurality of radio access network nodes 110, each providing network access to a plurality of WCDs 150a, 150b. The herein disclosed embodiments are no limited to any particular number of radio access network nodes 110 or WCDs 150a, 150b. In this respect it is assumed that there is at least two WCDs 150a, 150b each comprising a respective client node 400a, 400b. Typically the WCD 150a, 150b are GC WCDs but the WCD 150a, 150b may generally be any suitable kind of WCD. The embodiments disclosed herein thus relate to mechanisms for transmission control in a group communications (GC) system. In order to obtain such mechanisms there is provided a WCD 150a, 150b, a method performed by the WCD, and a computer program comprising code, for example in the form of a computer program product, that when run on processing circuitry of the WCD 150a, 150b, causes the WCD to perform the method.

Figure 3A and Figure 3B are flow charts illustrating embodiments of methods for transmission control in a GC system 100 comprising a plurality of GC wireless communication devices (WCDs). The methods are advantageously provided as computer programs 420a, 420b.

Reference is now made to Figure 3A illustrating a method for transmission control in a GC system 100 according to an embodiment. Actions S102, S106, Sio8a and S110 in Fig. 3A correspond to actions with same reference number illustrated in Figure 4 showing a signalling diagram illustrating embodiments described herein. The method is performed by a first GC WCD 150a currently acting as a transmission arbitrator (TA) for a plurality of peer GC WCDs of the same or similar kind.

Typically, a GC system contains several peer GC WCDs or similar that should receive the same data (e.g. voice or video), e.g. 150a, 150b, 150c, lsod as indicated in Fig. lA and Fig. 4. Preferably, the data is transmitted by one transmitting instance at a certain time in the GC system, e.g. a WCD. The TA decides on which peer WCD that is currently allowed to transmit data in the GC system.

In one action S102 of the flowchart in Fig. 3A, a first GC WCD 150a receives a transmission request from a second GC WCD 150b. The request comprises location information indicating the location of the second GC WCD

i5ob.Generally, the GC WCD 150a, 150b maybe any kind of suitable WCD. The transmission request may be any suitable message with information that indicates to the first GC WCD 150a currently acting as TA that the second GC WCD 150b wishes to send a group transmission intended for the GC WCDs in the GC system.

The location information may e.g. indicate a distance between the first GC WCD and the second GC WCD and/or a distance between a predetermined position and a position of the second GC WCD and/ or a position at which the second GC WCD is located and/or an area wherein the second GC WCD is located. For example, the distance between the first GC WCD and the second GC WCD may be indicated by the signal strength at which the transmission request from the second GC WCD was received by the first GC WCD. Any distance between a certain position (e.g. the position of the first GC WCD or any other position, e.g. such as the location of an accident or an incident or an event or similar) and the position of the second GC WCD may e.g. be determined by knowing the position of the certain position (e.g. knowing its coordinates or similar) and receiving the position of the second GC WCD (e.g. the coordinates or similar of the second GC WCD). The area wherein the second GC WCD is located may e.g. be indicated by a position at which the second GC WCD is located, or by some indicator representing a certain area e.g. such as a defined event area or incident area or e.g. a cell, a routing area (RA) or a tracking area (TA) or similar area concept that is commonly used in the specifications produced in the 3rd Generation Partnership Project (3GPP). In another action S106, the first GC WCD 150a evaluates, based on the location information received in action S102, if the second GC WCD 150b can be approved as a new TA.

The evaluation may e.g. be done by determining whether the second GC WCD 150b is within a predetermined distance of the first GC WCD and/ or within a predetermined distance of a certain position, e.g. the location of an traffic accident or some other incident or an event or similar and/or whether the second GC WCD is within a predetermined area, e.g. such as within a cell or a RA or a TA or similar. Here, it is preferred that the second GC WCD 150b is approved as the new TA when the GC WCD is found to be within the

predetermined distance and/or within the predetermined area.

In another action Sio8a it is preferred that that the first GC WCD 150a sends, when the second GC WCD 150b is approved as the new TA in the previous action S106, a TA notification towards the second GC WCD 150b to indicate that the second GC WCD 150b has been approved as the new TA. However, if the second GC WCD 150b was not approved as the new TA then it is preferred that that the first GC WCD 150a sends a TA notification towards the second GC WCD 150b to indicate that the second GC WCD 150b is rejected as the new TA. If this happens, it is preferred that the first GC WCD 150a also sends a transmission request response to the second GC WCD 150b, see step 108b below. Alternatively, the first GC WCD 150a may not sends any notification at all towards the second GC WCD 150b when the second GC WCD 150b was not approved as the new TA.

The TA notification maybe any suitable message with information that indicates to the second GC WCD 150b that it has been approved as TA. In another action S110 it is preferred that that the first GC WCD 150a receives from the second GC WCD 150b, in response to sending a TA notification in action Sio8a indicating that the second GC WCD 150b is approved as the new TA, a TA taken message indicating that the second GC WCD 150b has accepted to be the new TA. The TA taken message may be any suitable message with information that indicates to the first WCD 150a that the second WCD 150b has now accepted to be the new TA. Reference is now made to Figure 3B illustrating a method for transmission control in a GC system 100 according to further embodiments. Actions S102, S104, S106, Sio8a, Sio8b and S110 in Fig. 3a correspond to actions with same reference number illustrated in Figure 4 showing a signalling diagram illustrating embodiments described herein.

Action S102 in the flowchart of Fig. 3B is preferably the same or very similar as action S102 described above with reference to Fig. 3A.

In action S104 it is preferred that that the first GC WCD 150a determines whether the transmission request received in action S102 can be granted, or otherwise queued or rejected.

The determining may e.g. be based on a number (e.g. maximum number) of queued transmission requests supported by the GC WCD 150a and/ or a number (e.g. maximum number) of simultaneous transmissions allowed by the GC WCD 150a in the GC system and/or the capability (and preferably the authority) of the GC WCD 150a (and preferably also of the GC WCD 150b) to override one or more ongoing transmissions from other GC WCDs. Here, it is preferred that the transmission request is granted if there is no transmission going on in the GC system or if the maximum number of simultaneous transmissions allowed by the GC WCD 150a in the GC system is not reached or if the transmission in the transmission request is allowed to override one or more transmissions ongoing in the GC system. Similarly, the transmission request may be queued by the GC WCD 150a currently acting as TA if the maximum number of queued transmission requests is not reached.

Action S106 in the flowchart of Fig. 3B is preferably the same or very similar as action S106 described above with reference to Fig. 3A.

Action Sio8a in the flowchart of Fig. 3B is preferably the same or very similar as action Sio8a described above with reference to Fig. 3A. In action Sio8b it is preferred that the first GC WCD 150a sends a

transmission request response towards the second GC WCD 150b indicating that the transmission request is granted, or otherwise that the transmission request is queued or rejected. The transmission request response may be any suitable message with information that indicates to the second GC WCD 150b that the transmission request has been granted, queued or rejected or similar.

As indicated in fig. 3B and fig. 4, the TA notification in action Sio8a and the transmission request response in action Sio8b maybe sent as in S108 in one common response message towards the second GC WCD 150b.

Action S110 in the flowchart of Fig. 3B is preferably the same or very similar as action S110 described above with reference to Fig. 3A.

Figure 5A schematically illustrates, in terms of a number of functional units, the components of a GC WCD 150a, 150b according to an embodiment.

Processing circuitry 310 is provided using any combination of one or more of a suitable central processing unit (CPU), multiprocessor, microcontroller, digital signal processor (DSP), application specific integrated circuit (ASIC), field programmable gate arrays (FPGA) etc., capable of executing software

instructions stored in a computer program product 410b (as in Fig. 6), e.g. in the form of a storage medium 430.

Particularly, the processing circuitry 310 is configured to cause the GC WCD 150a, 150b to perform a set of operations or steps S102 and S106, or some or all of operations or steps S102-S110. These operations, or steps, S102-S110 have been discussed above. For example, the storage medium 330 may store the set of operations, and the processing circuitry 310 may be configured to retrieve the set of operations from the storage medium 330 to cause the client node 300a, 300b to perform the set of operations. The set of operations maybe provided as a set of executable instructions. Thus, the processing circuitry 310 is thereby arranged to execute methods as herein disclosed.

The storage medium 330 may also comprise persistent storage, which, for example, can be any single one or combination of magnetic memory, optical memory, solid state memory or even remotely mounted memory.

The GC WCD 150a, 150b may further comprise a communications interface 320 for communications at least with the second GC WCD 150b. As such the communications interface 320 may comprise one or more transmitters and receivers, comprising analogue and digital components and a suitable number of antennas for wireless communications and ports for wireline communications.

The processing circuitry 310 controls the general operation of the GC WCD 150a, 150b e.g. by sending data and control signals to the communications interface 320 and the storage medium 330, by receiving data and reports from the communications interface 320, and by retrieving data and instructions from the storage medium 330. Other components, as well as the related functionality, of the GC WCD 150a, 150b are omitted in order not to obscure the concepts presented herein.

Figure 5B schematically illustrates, in terms of a number of functional modules, the components of a GC WCD 150a, 150b according to an embodiment. The GC WCD 150a, 150b of Fig. 5B comprises a number of functional modules; a receive module 310a configured to perform steps S102, S110, and an evaluation module 310b configured to perform step S106. The GC WCD 150a, 150b of Fig. 5B may further comprises a number of optional functional modules, as herein represented by functional modules 310c and 3iod. The functionality of each functional module 3ioa-3iod have been discussed above. In general terms, each functional module 3ioa-3iod maybe implemented in hardware or in software. Preferably, one or more or all functional modules 3ioa-3iod maybe

implemented by the processing circuitry 310, possibly in cooperation with functional units 320 and/or 330. The processing circuitry 310 may thus be arranged to fetch, from the storage medium 330, instructions as provided by a functional module 3ioa-3iob and to execute these instructions, thereby performing any set of operations or steps S102 and 106, or some or all of operations or steps S102-S110 as disclosed above.

Any processing circuitry, communications interface and storage medium of the GC WCD 150a, 150b maybe shared with the processing circuitry 310,

communications interface 320 and storage medium 330 of the GC WCD 150a, 150b. It is thus not necessary for the GC WCD 150a, 150b to have a specific or dedicated processing circuitry 310, communications interface 320 and/ or storage medium 330 as long as the processing circuitry, communications interface and storage medium of the GC WCD 150a, 150b is configured to implement the functionality of the herein disclosed set of operations or steps S102 and S106, or some or all of operations or steps S102-S110 as disclosed above.

Figure 6 shows one example of a computer program product 410a, 410b comprising computer readable means 430. On this computer readable means 430, a computer program 420a can be stored, which computer program 420a can cause the processing circuitry 310 and thereto operatively coupled entities and devices, such as the communications interface 320 and the storage medium 330, to execute methods according to embodiments described herein. The computer program 420a and/or computer program product 410a may thus provide means for performing any steps of the GC WCD 150a, 150b as herein disclosed. On this computer readable means 430, a computer program 420b can be stored, which computer program 420b can cause the processing circuitry 310 and thereto operatively coupled entities and devices, such as the

communications interface 320 and the storage medium 330, to execute methods according to embodiments described herein. The computer program 420b and/or computer program product 410b may thus provide means for performing any steps of the GC WCD 150a, 150b as herein disclosed.

In the example of Fig. 6, the computer program product 410a, 410b is illustrated as an optical disc, such as a CD (compact disc) or a DVD (digital versatile disc) or a Blu-Ray disc. The computer program product 410a, 410b could also be embodied as a memory, such as a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM), or an electrically erasable programmable read-only memory (EEPROM) and more particularly as a non-volatile storage medium of a device in an external memory such as a USB (Universal Serial Bus) memory or a Flash memory, such as a compact Flash memory. Thus, while the computer program 420a, 420b is here schematically shown as a track on the depicted optical disk, the computer program 420a, 420b can be stored in any way which is suitable for the computer program product 410a, 410b. The proposed solutions have mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the disclosure, as shown by the appended list of enumerated embodiments denoted items. 1. A method for transmission control in a GC system 100, the method being performed by a first WCD 150a currently acting as a TA for a plurality of WCDs, (150a, 150b, 150c, I50d) in the GC system, comprising:

- receiving (S102), from a second WCD 150b, a transmission request

comprising location information indicating the location of the second WCD 150b; and

- evaluating (S106), based on the location information, if the second WCD

150b can be approved as a new TA. 2. The method according to item l, comprising:

sending (Sio8a) a TA notification message towards the second WCD indicating one of; that the second WCD is approved as the new TA, or that the second WCD is rejected as the new TA.

3. The method according to item 2, comprising:

receiving S110, in response to sending (108a) the TA notification message indicating that the second WCD is approved as the new TA, a TA taken message indicating that the second WCD has accepted to be the new TA.

4. The method according to any one of item 1-3, wherein the location information indicates at least one of;

- a distance between the first WCD and the second WCD,

- a distance between a predetermined position and a position of the second WCD,

- a position at which the second WCD is located,

- an area wherein the second WCD is located.

5. The method according to any one of item 1-4, wherein the evaluating (S106) comprises an evaluation of whether the second WCD is within at least one of;

- a predetermined range of the first WCD,

- a predetermined range of a predetermined position,

- a predetermined area.

6. The method according to item 5, wherein the predetermined area is indicated by at least one of;

- a position at which the first WCD is located,

- a predetermined area surrounding the first WCD, - a broadcast area in which the first WCD may send broadcast messages to be received by the other WCDs 150b, 150c, lsod in said plurality of WCDs. 7. The method according to any one of item 1-6, comprising:

determining (S104) if the transmission request can be one of; granted, queued, or rejected.

8. The method according to item 7, wherein the determining (S104) is based on at least one of;

- a number of queued transmission requests supported by the first WCD,

- a number of simultaneous transmission allowed by the first WCD, or

- a capability of the first WCD to override one or more ongoing

transmissions.

9. The method according to any one of item 7-8, comprising:

sending (Sio8b) a transmission request response towards the second WCD indicating that;

- transmission request is granted, or

- transmission request is queued, or

- transmission request is rejected.

10. The method according to items 2 and 9, wherein the TA notification (Sio8a) and the transmission request response (Sio8b) are sent (S108) in one response message towards the second WCD.

11. A first WCD 150a for transmission control in a GC system 100, the first WDC 150a comprising processing circuitry 310, the processing circuitry being configured to cause the first WCD 150a to perform a set of operations causing the first WCD 150a to act as a current TAfor a plurality of WCDs, (150a, 150b, 150c, I50d) in the GC system 100 and causing the first WCD 150a to:

- receive (S102), from a second WCD 150b, a transmission request

comprising location information indicating the location of the second WCD 150b; and

- evaluate (S106), based on the location information, if the second WCD

150b can be approved as a new TA.

12. The first WCD 150a according to item 11, further comprising a storage medium 330 storing a set of operations, and wherein the processing circuitry is configured to retrieve said set of operations from the storage medium to cause the first WCD to perform said set of operations.

13. The first WCD 150a according to any one of item 11-12, further comprising a communications interface 320 for communications at least with the second

WCD, and wherein the processing circuitry is configured to receive and transmit messages via said communications interface 320.

14. The first WCD 150a according to any one of item 11-13, wherein the processing circuitry is configured to send (Sio8a) a TA notification message towards the second WCD indicating one of; that the second WCD 150b is approved as the new TA, or that the second WCD is rejected as the new TA.

15. The first WCD 150a according to any one of item 12-14, wherein the processing circuitry is configured to receive (S110), in response to sending

(108a) the TA notification message indicating that the second WCD 150b is approved as the new TA, a TA taken message indicating that the second WCD 150b has accepted to be the new TA. 16. The first WCD 150a according to any one of item 11-15, wherein the location information indicates at least one of;

- a distance between the first WCD and the second WCD,

- a distance between a predetermined position and a position of the second WCD,

- a position at which the second WCD is located,

- an area wherein the second WCD is located.

17. The first WCD 150a according to any one of item 11-16, wherein the processing circuitry is configured to evaluate, based on the location information, whether the second WCD 150b is within at least one of;

- a predetermined range of the first WCD,

- a predetermined range of a predetermined position,

- a predetermined area.

18. The first WCD 150a according to item 17, wherein the predetermined area is indicated at least one of;

- a position at which the first WCD 150a is located,

- a predetermined area surrounding the first WCD,

- a broadcast area in which the first WCD may send broadcast messages to be received by the other WCDs 150b, 150c, lsod in said plurality of WCDs.

19. The first WCD 150a according to any one of item 11-18, wherein the processing circuitry is configured to determine (S104) if the transmission request can be one of; granted, queued, or rejected.

20. The first WCD 150a according to item 19, wherein the processing circuitry is configured to determine(Si04) if the transmission request can be one of;

granted, queued, or rejected, based on at least one of; - a number of queued transmission requests supported by the first WCD,

- a number of simultaneous transmission allowed by the first WCD, or

- a capability of the first WCD to override one or more ongoing

transmissions.

21. The first WCD 150a according to item 20, wherein the processing circuitry is configured to send (Sio8b) a transmission request response towards the second WCD indicating that;

- transmission request is granted, or

- transmission request is queued, or

- transmission request is rejected.

22. The first WCD 150a according to items 14 and 20, wherein the processing circuitry is configured to send (108) the TA notification (Sio8a) and the transmission request response (Sio8b) in one response message towards the second WCD 150b.

23. A computer program 420a for transmission control in a group

communications system 100, the computer program comprising computer code which, when run on processing circuitry 310 of a first GC WCD 150a currently acting as a TA for a plurality of GC WCDs (150a, 150b, 150c, lsod), causes the first GC WCD to:

- receiving (S102), from a second GC WCD 150b, a transmission request comprising location information indicating the location of the second GC WCD; and

- evaluating (S106), based on the location information, if the second GC

WCD can be approved as a new TA. 24. A computer program product 410a, 410b comprising a computer program 420a, 420b according to at least item 23, and a computer readable means 430 on which the computer program is stored.

While various aspects and embodiments of the present disclosure have been described above, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of the present disclosure should not be limited by any of the above described exemplary embodiments. Moreover, any combination of the elements described in this disclosure in all possible variations thereof is encompassed by the disclosure unless otherwise indicated herein or otherwise clearly contradicted by context.

Additionally, while the actions and processes described herein and illustrated in the drawings are shown as a sequence of steps, this was done solely for the sake of illustration. Accordingly, it is contemplated that some steps may be added, some steps may be omitted, the order of the steps may be re-arranged, and some steps maybe performed in parallel.