Mbms bearer setup in a group communications system

Multimedia Broadcast and Multicast Service Carrier Setting in Group Communication System

MBMS BEARER SETUP IN A GROUP COMMUNICATIONS SYSTEM

The embodiment presented herein relates to a computer program product of a control node, a user node, a computer program, and a multimedia broadcast multicast service (MBMS) carrier configuration used in a group communication system.

In a communication system, there may be a challenge to obtain the excellent performance and capacity of a given communication protocol and to adopt the parameters and physical environment of the communication system in it. For example, one example of an application available in some communication systems is group communication services. Generally speaking, group communication requires the same information to be delivered to multiple users. In a group communication system (for example, a push-to-talk (PTT) system), users who receive the same media constitute a group of users. These users can be located in different locations. If many users are located in the same area, multicast or broadcast-based transmission using, for example, multicast broadcast multimedia service (MBMS) is effective. When MBMS is used in a group communication system, it is necessary to inform the user before which radio resources are used for broadcast media and how the user will receive one of the specific group calls in their resources. The process of using information to notify the user to receive a group call via MBMS is marked as the service announcement process. In a group communication system (for example, a push-to-talk (PTT) system), a floor control function is very important. This low-level control function provides users with the ability to request certain capabilities for transferring media to other users' shared resources in the group communication system. In order to effectively use a low-level control function, it is necessary to constantly decide which user is allowed to transmit the media to one of the low-level arbiters. The bottom-level control procedure starts with the hope that a user of the transmission medium sends a bottom-level request message to the bottom-level arbiter. If there are available resources, the bottom arbiter grants the user the right to be transmitted by the bottom arbiter that sends a bottom grant message to the user. The bottom layer arbiter also sends a bottom layer adoption message to all users who have declared interest in joining, and thus exchange media in a specific communication group. Fig. 10 is a signalling scheme of using the MBMS carrier for group communication via a cellular communication system according to the prior art. At least one group communication session is pre-established based on the handshaking media description parameters of the communication type to be executed (step S301). If the MBMS carrier is used for group communication, the MBMS carrier needs to be activated and announced to the user (step S302). The announcement contains a description of the media, which includes the Internet Protocol (IP) address and the port to which the media will be sent, the media codec, and the encryption key. In addition, the announcement is group-specific. A call setting procedure is triggered by the first bottom layer request (step S303). The service announcement procedure (as in step S302 above) must be executed before the call setting, because this procedure takes too much time. In addition, on the same carrier, the underlying control message is sent as the medium. This means that media packets and control packets are being sent on the same MBMS carrier. The bottom layer request message responds with a bottom layer grant message, thereby allowing the user who has sent the bottom layer request to use the declared MBMS carrier of the media transmission of the specific group (step S304). Broadcast a bottom layer adoption message to other users to inform these users that the MBMS carrier will be used for media transmission (step S305). Under normal network conditions, not all groups have uninterrupted calls at the same time. Therefore, the resources of all groups that activate the MBMS carrier of a specific group and declare that the MBMS carrier is used for group communication can be invalid, because many groups can be quiet (that is, groups that currently do not transmit media between users) Group). Therefore, there is still a need for improved utilization of one of the available network resources for effective group communication.

One purpose of the embodiments herein is to effectively utilize the available network resources for effective group communication. According to a first aspect, a method for multimedia broadcast multicast service (MBMS) carrier setting in a group communication system is presented. The method is executed by a control node. The method includes activating and declaring an MBMS bearer to a user node, wherein the MBMS bearer is independent of any specific group of user nodes. The method includes: obtaining a call setting message of a group call from a first user node of one of the user nodes. The method includes: broadcasting a connection message of a group call to at least one other user node of the user node in response to the received call setting message. Advantageously, this provides an effective setting procedure for one of the MBMS carriers in a group communication system. Advantageously, this provides an effective service announcement procedure. This allows radio resources to be utilized in an efficient and dynamic way. Advantageously, this allows the control node to determine which group call should be broadcast based on the number of users in each group. According to a second aspect, a control node for multimedia broadcast multicast service (MBMS) bearer settings in a group communication system is presented. The control node includes a processing circuit. The processing circuit is configured to cause the control node to perform a set of operations. The processing circuit is configured to enable the control node to activate and announce an MBMS bearer to the user node, wherein the MBMS bearer is independent of any specific group of user nodes. The processing circuit is configured so that the control node obtains a call setting message of a group call from a first user node of the user node. The processing circuit is configured to respond to the received call setting message so that the control node broadcasts a connection message of a group call to at least one other user node of the user node. According to a third aspect, a computer program for multimedia broadcast multicast service (MBMS) carrier settings in a group communication system is presented, and the computer program includes making the control node when running on a processing circuit of a control node The computer program code of a method is executed according to the first aspect. According to a fourth aspect, a method for multimedia broadcast multicast service (MBMS) carrier setting in a group communication system is presented. The method is executed by a user node. The method includes obtaining a broadcast service announcement of an MBMS bearer from a control node, the MBMS bearer being independent of any specific group of user nodes. The method includes providing a call setting message of a group call to the control node. According to a fifth aspect, a user node for multimedia broadcast multicast service (MBMS) bearer configuration in a group communication system is presented. The user node includes a processing circuit. The processing circuit is configured to cause the user node to perform a set of operations. The processing circuit is configured so that the user node obtains a broadcast service announcement of an MBMS bearer from a control node, and the MBMS bearer is independent of any specific group of user nodes. The processing circuit is configured so that the user node provides a call setting message of a group call to the control node. According to a sixth aspect, a computer program for multimedia broadcast multicast service (MBMS) carrier settings in a group communication system is presented, and the computer program includes making the user node when running on the processing circuit of a user node The computer program code of a method is executed according to the fourth aspect. According to a seventh aspect, a computer program product including a computer program according to at least one of the third aspect and the sixth aspect and a computer readable component stored on the computer program is presented. It should be noted that, wherever appropriate, any feature of the first, second, third, fourth, fifth, sixth, and seventh aspects can be applied to any other aspects. Sample. Similarly, any advantages of the first aspect can be equally applied to the second aspect, the third aspect, the fourth aspect, the fifth aspect, the sixth aspect, and/or the seventh aspect, respectively, and vice versa NS. Other objectives, features, and advantages of the disclosed embodiments will be understood from the following detailed disclosure, from the attached column of the embodiments, and from the drawings. Generally speaking, unless clearly defined otherwise herein, all terms used in the present invention should be interpreted according to their original meanings in the technical field. Unless specifically stated otherwise herein, all references to "a/the element, device, component, component, step, etc." will be openly interpreted as at least one example of the reference element, device, component, component, step, etc. Unless specifically stated otherwise herein, it is not necessary to perform the steps of any method disclosed herein in the exact order disclosed.

Hereinafter, the proposed solution will be described more fully with reference to the accompanying drawings, some of which are shown in the accompanying drawings. However, these proposed solutions can be embodied in many different forms, and should not be interpreted as being limited to the embodiments described herein; instead, these embodiments are provided by way of examples so that the present invention will be comprehensive and complete. And completely convey the scope of the proposed solution to those who are familiar with the technology. The same numbers refer to the same elements in the description. Any steps or features depicted by dashed lines should be considered optional. FIG. 1 is a schematic diagram of a communication system 100 in which one of the embodiments presented herein can be applied. Assuming that the communication system 100 provides services to group communication, it can be regarded as a group communication system. The group communication system 100 may be a push-to-talk (PTT) system. The communication system 100 includes at least one control node 200 and at least two user nodes 300a, 300b. At least one control node 200 may be provided in or installed on a radio access network node 110, or provided in a radio access network 120 between another entity or device, a core network 130 An entity or device or an entity or device of a service network 140. Each user node may be provided in or installed on a respective wireless device 150a, 150b. Examples of wireless devices 150a, 150b include (but are not limited to) mobile stations, mobile phones, cell phones, wireless local line phones, user equipment (UE), smart phones, laptop computers, and desktop computers. Examples of the radio access network node 110 include (but are not limited to) radio base stations, base transceiver stations, node Bs, evolved node Bs, and access points. As understood by those skilled in the art, the communication system 100 may include a plurality of radio access network nodes 110, each of which provides network access to the plurality of wireless devices 150a, 150b. The embodiments disclosed herein are not limited to any specific number of radio access network nodes 110 or wireless devices 150a, 150b. In this regard, it is assumed that there is at least one control node 200 and at least two user nodes 300a, 300b. The embodiments disclosed herein are therefore related to the mechanism of multimedia broadcast multicast service (MBMS) carrier configuration used in a group communication system. In order to obtain these mechanisms, a control node 200 is provided, a method executed by the control node 200, a computer program including a code (for example, in the form of a computer program product), when the code is on the processing circuit of the control node 200 At runtime, the control node 200 is caused to execute the method. In order to obtain these mechanisms, further provide a user node 300a, 300b, a method executed by the user nodes 300a, 300b, and a computer program including a code (for example, in the form of a computer program product), when the code is in the user When the processing circuits of the nodes 300a and 300b are running, the user nodes 300a and 300b are caused to execute the method. In terms of several functional units, FIG. 2a schematically illustrates the components of the control node 200 according to an embodiment. Use one of the software instructions that can be executed in a computer program product 410a (as in FIG. 4) stored in, for example, a storage medium 230, suitable for central processing unit (CPU), multiprocessor, microcontroller The processing circuit 210 is provided by any combination of one or more of a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA), etc. In particular, the processing circuit 210 is configured to cause the control node 200 to perform a set of operations or steps S101 to S105. These operations or steps S101 to S105 will be disclosed below. For example, the storage medium 230 may store the set of operations, and the processing circuit 210 may be configured to retrieve the set of operations from the storage medium 230, so that the control node 200 can perform the set of operations. The set of operations can be provided as a set of executable instructions. Therefore, the processing circuit 210 is thereby configured to perform the method as disclosed herein. The storage medium 230 may also include permanent storage, which, for example, may be any single or combination of magnetic memory, optical memory, solid-state memory, or even remotely mounted memory. The control node 200 may further include a communication interface 220 for communicating with at least the user nodes 300a, 300b. Thus, the communication interface 220 may include one or more transmitters and receivers, which include analog and digital components, a suitable number of antennas for wireless communication, and ports for wired communication. The processing circuit 210, for example, by sending data to the communication interface 220 and the storage medium 230 and controlling the signals to the communication interface 220 and the storage medium 230, by receiving data and reports from the communication interface 220, and by retrieving data from the storage medium 230 Obtain data and instructions to control the general operation of the control node 200. Other components and related functions of the control node 200 are omitted so as not to hinder the concepts presented herein. In terms of several functional modules, FIG. 2b schematically illustrates the components of the control node 200 according to an embodiment. The control node 200 of FIG. 2b includes a number of functional modules; it is configured to perform one of the following steps S102 to activate the module 210a, configured to perform one of the following steps S102, to declare the module 210b, and configured to perform the following steps One of S103 and S105 obtains a module 210c and is configured to perform a broadcast module 210d of the following step S104. The control node 200 of FIG. 2b may further include several optional functional modules, such as any of the pre-built modules 210e configured to perform one of the following steps S101. The function of each functional module 210a to 210e will be further disclosed in the background content of the usable functional modules 210a to 210e. Generally speaking, each functional module 210a to 210e can be implemented in hardware or software. Preferably, one or more or all of the functional modules 210a to 210e may be implemented by the processing circuit 210 (possibly) in cooperation with the functional units 220 and/or 230. The processing circuit 210 can therefore be configured to retrieve the instructions provided by a functional module 210a to 210e from the storage medium 230 and execute these instructions, thereby performing any steps as will be disclosed below. The control node 200 may be provided as a separate device or as part of at least one further device. For example, the control node 200 may be provided in a node of a radio access network or a node of a core network. Alternatively, the functions of the control node 200 may be distributed between at least two devices or nodes. These at least two nodes or devices may be part of the same network part (such as a radio access network or a core network) or may be distributed between at least two of these network parts. Some examples of where the control node 200 can be provided in the communication system 100 are shown in FIG. 1. The function of the control node 200 can be implemented at the service layer of the protocol stack. Generally speaking, instructions that need to be executed in real time can be executed in a device or node and are operated closer to the radio access network than instructions that do not need to be executed in real time. In this regard, for example, when the embodiments disclosed herein are executed in real time, at least part of the control node 200 may reside in a radio access network, such as a radio access network node. Therefore, a first part of an instruction executed by the control node 200 can be executed in a first device, and a second part of an instruction executed by the control node 200 can be executed in a second device; the embodiments disclosed herein do not It is limited to any specific number of devices on which the instructions executed by the control node 200 can be executed. Therefore, according to the embodiments disclosed herein, these methods are suitable for execution by a control node 200 remaining in a cloud computing environment. Therefore, although a single processing circuit 210 is shown in FIG. 2a, the processing circuit 210 may be distributed in a plurality of devices or nodes. The processing circuit 210 is similarly applied to the functional modules 210a to 210e in FIG. 2b and the computer program 420a in FIG. 4 (see below). In terms of several functional units, FIG. 3a schematically illustrates the components of a user node 300a, 300b according to an embodiment. One of the software instructions that can be executed in a computer program product 410b (as in FIG. 4) stored in the form of a storage medium 330 is suitable for central processing unit (CPU), multiprocessor, microcontroller, Digital signal processor (DSP), application specific integrated circuit (ASIC), field programmable gate array (FPGA), etc., provide the processing circuit 310 in any combination of one or more. In particular, the processing circuit 310 is configured to make the user nodes 300a, 300b perform a set of operations or steps S201 to S205. These operations or steps S201 to S205 will be disclosed below. For example, the storage medium 330 may store the set of operations, and the processing circuit 310 may be configured to retrieve the set of operations from the storage medium 330 to cause the user nodes 300a, 300b to perform the set of operations. The set of operations can be provided as a set of executable instructions. Therefore, the processing circuit 310 is thereby configured to perform the method as disclosed herein. The storage medium 330 may also include permanent storage, which, for example, may be any single or combination of magnetic memory, optical memory, solid-state memory, or even remotely mounted memory. The user nodes 300a, 300b may further include a communication interface 320 for communicating with at least the control node 200. Thus, the communication interface 320 may include one or more transmitters and receivers, which include analog and digital components and a suitable number of antennas for wireless communication and ports for wired communication. Processing circuit 310 For example, by sending data to the communication interface 320 and the storage medium 330 and controlling signals to the communication interface 320 and the storage medium 330, by receiving data and reports from the communication interface 320, and by retrieving data from the storage medium 330, and Command and control the general operations of the user nodes 300a and 300b. The other components and related functions of the user nodes 300a, 300b are omitted so as not to hinder the concepts presented in this article. In terms of several functional modules, FIG. 3b schematically illustrates the components of a user node 300a, 300b according to an embodiment. The user nodes 300a, 300b of FIG. 3b include several functional modules; the module is configured to perform one of the following steps S201, S202 to obtain a module, and the module is configured to perform one of the following steps S203, S205 to provide a module. The user nodes 300a, 300b of FIG. 3b may further include several optional functional modules, as represented by the functional module 310c in this document. The function of each functional module 310a to 310b will be further disclosed in the background content of the usable functional modules 310a to 310b. Generally speaking, each functional module 310a to 310b can be implemented in hardware or software. Preferably, the processing circuit 310 (Possibly) cooperate with the functional units 320 and/or 330 to implement one or more or all of the functional modules 310a to 310b. The processing circuit 310 can therefore be configured to retrieve the instructions provided by a functional module 310a to 310b from the storage medium 330 and execute these instructions, thereby performing any steps as will be disclosed below. The user nodes 300a, 300b may be provided as a separate device or part of at least one further device. For example, the user nodes 300a, 300b may be provided in a wireless device 150a, 150b. Therefore, any processing circuit, communication interface, and storage medium of the wireless devices 150a, 150b can be shared with the processing circuit 310, communication interface 320, and storage medium 330 of the user nodes 300a, 300b. Therefore, the user nodes 300a, 300b do not need to have their own processing circuit 310, communication interface 320, and storage medium 330, as long as the processing circuits, communication interface, and storage medium of the wireless devices 150a, 150b are configured to implement the user node 300a disclosed herein. , 300b function. FIG. 4 shows an example of a computer program product 410a, 410b including a computer readable component 430. A computer program 420a can be stored on the computer readable component 430, and the computer program 420a can turn on the processing circuit 210 and enable entities and devices (such as the communication interface 220 and the storage medium 230) to be operatively coupled to the processing circuit 210 according to the description herein. The described embodiment implements the method. The computer program 420a and/or the computer program product 410a can therefore provide components for executing any steps of the control node 200 as disclosed herein. A computer program 420b can be stored on the computer readable component 430. The computer program 420b can turn on the processing circuit 310 and enable entities and devices (such as the communication interface 320 and the storage medium 330) to be operatively coupled to the processing circuit 310 according to The embodiments described herein implement the method. The computer program 420b and/or the computer program product 410b can therefore provide components for executing any steps of the user nodes 300a, 300b as disclosed herein. In the example of FIG. 4, the computer program product 410a, 410b is shown as a compact disc, such as a CD (compact disc) or a DVD (Digital Versatile Disc) or a Blu-ray Disc. The computer program product 410a, 410b can 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 specifically, is embodied 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 small flash memory. Therefore, although the computer programs 420a, 420b are schematically shown as a track on the depicted optical disc herein, the computer programs 420a, 420b can be stored in any manner suitable for the computer program products 410a, 410b. 5 and 6 are flowcharts of an embodiment of a method for MBMS bearer setting executed by the control node 200. 7 and 8 are flowcharts of an embodiment of a method for MBMS bearer setting performed by the user node 300a. These methods are advantageously provided as computer programs 420a, 420b. Reference is now made to FIG. 5 illustrating a method for MBMS bearer configuration performed by the control node 200 according to an embodiment. Without instructing any group to be assigned to the MBMS carrier, an MBMS carrier is activated and announced for group communication. Therefore, in a step S102, the control node 200 is configured to activate and announce an MBMS bearer to the user nodes 300a, 300b, wherein the MBMS bearer is independent of any specific group of the user nodes 300a, 300b. Therefore, the MBMS bearer is announced without indicating any specific group of user nodes 300a, 300b assigned to the MBMS bearer. In this regard, the activation module 210a and the announcement module 210b may include, when executed by the control node 200, the processing circuit 210 (possibly) in combination with the communication interface 220 and the storage medium 230 to activate and announce the MBMS carrier so that the control node 200 executes the steps The instruction of S101. The underlying request message will be carried out in advance by a call setting message indicating which resources of the MBMS bearer will be used for a specific group call. Therefore, in a step S103, the control node 200 is configured to obtain a call setting message of a group call from a first user node 300a of the user nodes 300a, 300b. In this regard, the obtaining module 210c may include, when executed by the control node 200, the processing circuit 210 (possibly) combining the communication interface 220 and the storage medium 230 to obtain the call setting information so that the control node 200 executes step S103. In addition, in a step S104, the control node 200 is configured to broadcast a connection message of a group call for at least one other user node 300b of the user nodes 300a, 300b in response to the call setting message received in step S103. In this regard, the broadcast module 210d may include an instruction that when executed by the control node 200 causes the processing circuit 210 to (possibly) combine the communication interface 220 and the storage medium 230 to broadcast the connection message so that the control node 200 executes step S104. Group communication sessions and service announcements are group diagnosis. When the group call setting is performed, all downlink (from the control node to the user node) communication can be completed via the MBMS bearer. An embodiment of further details regarding the MBMS bearer configuration performed by the control node 200 will now be disclosed. The announcement of the MBMS carrier may include the parameters of the media stream to be transmitted on the MBMS carrier. The call setting message may include a group identifier of a specific group of the user nodes 300a, 300b of the group call. The control node 200 has received the group identifier for the user nodes 300a, 300b and therefore knows the participants of each group. The control node 200 may determine whether unicast or broadcast will be used. If it is determined, the broadcast of the control node 200 determines which stream in a bearer will be used. For example, the control node 200 can thereby determine which group call should be broadcast based on the number of user nodes 300a, 300b in each group. For example, assume that a first group call (named N1) of one of the participating user nodes is continuing via an MBMS bearer, and a second group call is a second group call of one of the participating user nodes (named N2>N1) Start in. The control node 200 can be configured such that the larger group (ie, the second group in the existing example) uses the resources of the MBMS bearer and therefore moves the first group to unicast transmission. Reference is now made to FIG. 6 illustrating a method for MBMS bearer configuration performed by the control node 200 according to a further embodiment. According to an embodiment, in a step S101, the control node 200 is configured to pre-establish at least a group communication session. This pre-establishment may occur before the control node 200 starts and broadcasts the MBMS bearer. Therefore, the group communication session and service announcement can be performed before any group call settings. However, this is not a necessary condition. Alternatively, step S102 can be performed before step S101. The activation of the MBMS carrier and the pre-establishment of the group communication session can be completed in any order, as long as the two are executed before the call setting information is obtained, as in step S103. The pre-establishment in step S101 may include exchanging media description parameters and communication parameters with the user nodes 300a and 300b. The connection message broadcast in step S104 can inform which resources on the carrier will be used for the media of a specific group of user nodes. The control node 200 can thereby assign resources from a large number of resources (in the form of available MBMS bearers) to a user node of a group call and notify the assigned resources. The control node 200 can be configured to handle the low-level control in the group communication system 100. According to an embodiment, in a step S105, the control node 200 is configured to obtain a bottom request message of the group call from the first user node 300a after obtaining the call setting message. The bottom request message can be obtained after the call setting message of the group call is obtained in step S103. Alternatively, the underlying request message and the call setting message (obtained in step S103) are combined into one message. Now refer to FIG. 7 which illustrates a method for MBMS bearer configuration performed by the user node 300a according to an embodiment. As mentioned above, in step S102, the control node 200 announces an MBMS bearer. Therefore, in a step S202, the user node 300a may be configured to obtain a broadcast service announcement of an MBMS carrier from the control node 200. The MBMS carrier is independent of any specific group of user nodes 300a, 300b. In this regard, the obtaining module 310a may include, when executed by the user node 300a, making the processing circuit 310 (Possibly) Combine with the communication interface 320 and the storage medium 330 to obtain the broadcast service announcement so that the user node 300a executes the instruction of step S202. In a step S203, the user node 300a is configured to provide a call setting message of a group call to the control node 200. In this regard, the providing module 310b may include, when executed by the user node 300a, the processing circuit 310 (possibly) combined with the communication interface 320 and the storage medium 330 to provide call setting information so that the user node 300a executes the instruction of step S203. The user node 300a can provide the call setting message of the group call in response to the announcement that the user node 300a has obtained the broadcast service. However, the user node 300a does not need to receive the broadcast service announcement before providing the call setting message. If there is no MBMS carrier, the control node 200 will decide to use unicast when receiving the call setting message. An embodiment of further details regarding the MBMS bearer configuration performed by the user node 300a will now be disclosed. Reference is now made to FIG. 8 which illustrates a method for MBMS bearer configuration performed by the user node 300a according to a further embodiment. As disclosed above, the control node 200 in step S102 establishes at least the group communication session in advance. Therefore, according to an embodiment, in a step S201, the user node 300a is configured to obtain at least the pre-established information of the group communication session from the control node 200. As disclosed above, the pre-establishment in step S101 can occur before step S102 of announcing the MBMS carrier. Therefore, the user node 300a can obtain the pre-established information before obtaining the broadcast service announcement of the MBMS carrier from the control node 200. However, as also disclosed above, the order of steps S101 and S102 can be reversed and therefore the order of steps S201 and S202 can also be reversed. As disclosed above, the control node 200 in step S104 broadcasts one of the connection messages of the group call on the MBMS bearer to at least one other user node 300b of the user nodes 300a and 300b in response to the call setting message received in step S103. Then, in step S203, the first user node 300a provides the call setting information. Then, according to an embodiment, in a step S205, the user node 300a is further configured to provide a bottom request message of the group call to the control node 200 after providing the call setting message in step S203. A specific embodiment for MBMS bearer configuration will now be disclosed in detail based on at least part of the above-disclosed embodiments with reference to the signaling diagram of FIG. 9. Parallel reference continues in Figures 1 to 8. This particular embodiment relates to a group communication system (such as a PTT system) including a group communication server represented by the control node 200 disclosed herein, the group communication server including a low-level arbiter function and It is a cellular network that supports transmission based on unicast and broadcast and can be installed on the wireless device 150a, 150b of user nodes 300a, 300b. Steps S101 and S201: Before the group communication can be started, the control node 200 and the user nodes 300a, 300b establish at least one group communication session in advance by using the handshaking media description parameters of the communication type to be executed. This can include IP address, port, media codec and encryption key. In addition, each group communication session may include one or more media streams. This establishes one or more media streams in one or more group communication sessions that can be used by any group with the same media description parameters. Steps S102 and S202: when no specific group of user nodes is indicated, at least one MBMS bearer is activated and announced. The service announcement informs the user nodes 300a, 300b that there are one or more active MBMS bearers on certain resources. Steps S103 and S203: the first user node 300a sends a call setting message (via a unicast carrier) to inform the control node 200 of one of the pre-established sessions for media transmission. This alleviates the need for the user node 300a and the control node 200 to negotiate media description parameters again. One purpose of the call setting message is to use one of the pre-established sessions to set up a group call. Steps S104 and S204: the control node 200 knows the location of at least one second user node 300b (ie, the received user node) in the specific group and if at least a part of the at least one second user node 300b is located in the same area, then The control node 200 may decide to use MBMS as one of the transmission modes. To achieve this, the control node 200 sends a connection message via the broadcast channel in the area of at least one second user node 300b, that is, a group call will start from a specific group on the activated MBMS resource and used for a The media description parameter of a specific media stream. The call connection message can be sent via a previously activated MBMS bearer to all user nodes 300b that will receive group call messages via this MBMS bearer. The call connection message may include the group identification and an identifier of the media stream in the pre-established session used for the group call. Steps S105 and S205: start a group call by the first user node 300a sending a bottom layer request message to the control node 200. This message can be sent via a unicast carrier. Steps S106 and S206: The control node 200 responds to the bottom request message with a bottom grant message to the first user node 300a, thereby allowing the first user node 300a to be used for the transmission of the specific group. This message can be sent via a unicast carrier. Steps S107 and S207: the control node 200 sends a bottom layer adoption message to at least one second user node 300b to inform the at least one second user node 300b to use the bottom layer and media transmission can start from another user node 300a. This message may include the identification of the transmitting user node 300a and the group identification. The message can be sent via an MBMS carrier to all user devices 300b that have been previously configured to receive calls via the MBMS carrier. Steps S106 and S206: On the one hand, it can be S107 and S207, and on the other hand, it can be executed in reverse order, that is, steps S107 and S207 can be executed before steps S106 and S206 are executed for the same group communication session. Now compare the procedure of using the MBMS carrier for group communication via a cellular communication system according to the prior art illustrated in FIG. 10 (and as described above). According to the prior art, the MBMS bearer is activated and announced before the call is set up. According to the prior art, the user nodes 300a, 300b already know which resources of the MBMS bearer are assigned to the underlying request of a specific group. Some differences between the mechanism disclosed in this article and the prior art are that when using MBMS carriers, there are no call setting messages and connection messages sent according to the prior art. In addition, the service announcement in the prior art allocates MBMS resources to a specific group. In the organization disclosed in this article, MBMS resources can be dynamically allocated to any group. The proposed solutions are mainly described above with reference to some embodiments. However, as can be easily understood by those skilled in the art, other embodiments shown in the attached list of the enumerated embodiments other than those disclosed above may also fall within the scope of the present invention.

<p>100Communication System</p><p>110Radio access network node</p><p>120Radio access network</p><p>130Core network</p><p>140Service Network</p><p>150aWireless device</p><p>150bWireless device</p><p>200Control Node</p><p>210Processing circuit</p><p>210aFunction Module/Startup Module</p><p>210bFunction Module/Announcement Module</p><p>210cFunction Module/Get Module</p><p>210dFunction Module/Broadcast Module</p><p>210eFunction Module</p><p>220Functional Unit</p><p>230Functional Unit/Storage Media</p><p>300aUser Node</p><p>300bUser Node</p><p>310Processing circuit</p><p>310aFunctional Module</p><p>310bFunctional Module</p><p>310cFunctional Module</p><p>320Communication Interface/Functional Unit</p><p>330Storage Media/Functional Unit</p><p>410aComputer Program Products</p><p>410bComputer Program Products</p><p>420acomputer program</p><p>420bcomputer program</p><p>430Computer readable components</p><p>S101Step</p><p>S102Step</p><p>S103Step</p><p>S104Step</p><p>S105Step</p><p>S106Step</p><p>S107Step</p><p>S201Step</p><p>S202Step</p><p>S203Step</p><p>S204Step</p><p>S205Step</p><p>S206Step</p><p>S207Step</p><p>S301Step</p><p>S302Step</p><p>S303Step</p><p>S304Step</p><p>S305Step</p>

Now (for example) describe the proposed solution with reference to the accompanying drawings, in which: Fig. 1 shows a schematic diagram of a communication system according to an embodiment; Fig. 2a shows the function of a control node according to an embodiment A schematic diagram of a unit; Fig. 2b is a schematic diagram showing a functional module of a control node according to an embodiment; Fig. 3a is a schematic diagram showing a functional unit of a user node according to an embodiment; Fig. 3b is a diagram showing A schematic diagram of a functional module of a user node according to an embodiment; Fig. 4 shows an example of a computer program product including a computer readable component according to an embodiment; Figs. 5, 6, 7 and 8 is a flowchart of a method according to an embodiment; FIG. 9 is a signaling scheme according to an embodiment; and FIG. 10 is a signaling scheme according to one of the prior art.

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