Systems and methods for handling media transmission in mission critical (MC) systems

Abstract

The disclosure relates to a 5G or 6G communication system supporting a higher data transmission rate. A system and method for processing media transmission in a mission critical (MC) system or MC video system are provided. According to the system and method of the present invention, waste of network resources can be avoided, and an opportunity to transmit important data can be given to other participants in a group when a maximum number of transmissions at a time in a group call is limited by network capacity. Therefore, the efficiency of the MC video system can be improved.

Description

Technical Field

[0001] This disclosure relates to telecommunications networks, and more specifically to mission-critical (MC) systems provided through telecommunications networks. More specifically, the present invention relates to systems and methods for processing media transmission in mission-critical (MC) systems or MC video systems. Background Technology

[0002] 5G mobile communication technology defines a wide frequency band that enables features such as high transmission rates and new services. This can be achieved not only in "sub-6GHz" bands such as 3.5GHz, but also in "greater than 6GHz" bands, including 28GHz and 39GHz, known as millimeter waves. Furthermore, to achieve transmission rates 50 times faster than 5G and ultra-low latency one-tenth that of 5G, 6G mobile communication technology (referred to as "super 5G systems") is being considered in terahertz bands (such as the 95GHz to 3THz band).

[0003] In the early stages of 5G mobile communication technology development, to support services and meet performance requirements related to enhanced mobile broadband (eMBB), ultra-reliable low-latency communication (URLLC), and massive machine-type communication (mMTC), standardization work is currently underway on beamforming and massive MIMO to mitigate radio wave path loss in millimeter waves and increase radio wave transmission distance. This includes supporting parameter sets (e.g., operating multiple subcarrier spacings) for efficient utilization of millimeter wave resources and dynamic operation of time slot formats; supporting multi-beam transmission and initial access techniques for broadband; defining and operating BWP (bandwidth portion); new channel coding methods (such as LDPC (low-density parity-check) codes for large data transmissions and polar codes for highly reliable transmission of control information); L2 preprocessing; and network slicing for providing dedicated networks specifically for particular services.

[0004] Currently, discussions are underway regarding improvements and enhancements to the initial performance of 5G mobile communication technology for services supported by 5G mobile communication technology. Physical layer standardization has been achieved for technologies such as V2X (Vehicle-to-Everything) for improving user convenience by using information transmitted about vehicle location and status to help autonomous vehicles determine driving directions; NR-U (New Radio Unlicensed) for system operation in unlicensed frequency bands to comply with various regulatory requirements; NR UE power saving; and non-terrestrial networks (NTN) for providing coverage in areas where terrestrial network communication is unavailable, including direct satellite communication and positioning.

[0005] Further, technologies for air interface architecture / protocol, such as Industrial Internet of Things (IIoT) supporting new services by interworking with other industries, e.g., healthcare, smart city, and security & safety, vehicle industries, and so on, IAB (Integrated Access and Backhaul) supporting wireless backhaul link and access link by an integrated means, mobility enhancement including conditional handover and DAPS (Dual Active Protocol Stack) handover, and two-step random access (2-step RACH) simplifying random access procedures, are being standardized. Also, a system architecture / service based on a 5G baseline architecture, e.g., service based interface or service based architecture, in conjunction with network function virtualization (NFV) and software-defined networking (SDN) technologies, and mobile edge computing (MEC) for receiving services based on UE location are being standardized.

[0006] With the commercialization of 5G mobile communication systems, exponentially increasing connected devices will access communication networks, and thus improvement in functionality and performance of 5G mobile communication systems and integrated operation of connected devices will be necessary. To this end, new research related to extended reality (XR) effectively supporting AR (Augmented Reality), VR (Virtual Reality), MR (Mixed Reality), and the like, improvement of 5G performance and reduction of complexity using artificial intelligence and machine learning (ML), AI service support, metaverse service support, and drone communication is planned.

[0007] Further, development of 5G mobile communication systems will serve as a basis for developing technologies for 6G mobile communication systems providing coverage for terahertz bands, technologies for multiple antenna transmission (such as FDD-MIMO (Full Dimensional MIMO), array antennas, and large-scale antennas), metamaterial-based lenses and antennas for improving coverage of signals in terahertz bands, OAM (Orbital Angular Momentum)-based high-dimensional space multiplexing technologies, and RIS (Reconfigurable Intelligent Surface)-based technologies, as well as technologies for improving frequency efficiency and overall network performance of 6G mobile communication systems and full-duplex technologies, AI (Artificial Intelligence)-based communication technologies for implementing system optimization using satellites and AI from the design stage and internalizing end-to-end AI support functions, and next-generation distributed computing technologies for implementing complex services beyond the limit of terminal operation capacity using super-high-performance communication and computing resources.

[0008] According to the development of communication systems, a method of processing media transmission in a mission critical (MC) system or MC video system is required. SUMMARY

[0009] TECHNICAL PROBLEM

[0010] In MC system or Mission Critical Video (MCVideo) system, the transmission control server state machine for 'General reception control operation' as specified in 3GPP TS 24.581 subclause 6.3.6, the transmission control server state machine for 'General transmission control operation' as specified in 3GPP TS 24.581 subclause 6.3.4, and the transmission control server state machine for 'Basic transmission control operation oriented to transmission participants' as specified in 3GPP TS 24.581 subclause 6.3.5 do not define any procedure to terminate the stream of the transmitter when all MCVideo receivers terminate receiving the stream, or when all MCVideo receivers do not accept the reception notification even after providing sufficient time to accept or reject the notification. Thus, the procedure to terminate the transmission stream is not defined when no user is interested in receiving that particular stream. Further, the conventional system does not provide any reason for the termination of transmission. Thus, if other users want to send important communication, the opportunity is not provided.

[0011] Therefore, it is desirable to address the above disadvantages or other disadvantages, or at least provide a useful alternative.

[0012] Solution to the problem

[0013] In Mission Critical Video (MCVideo) system, when a user in a group is authorized to send media, all MCVideo users belonging to that group will get the media transmission notification message from the MCVideo server. Based on user interest or priority, the user can accept, reject, or ignore the notification. If none of the users in the group accept the notification within a given time, or if initially some users are accepted but later all those users terminate the reception by sending a reception end request to the server, the user stream being sent should be terminated and the sending user should be informed of the reason for termination. 3GPP TS 24.581 currently does not define any procedure or method to terminate the stream and inform the transmitter when there is no active receiver for that stream.

[0014] In the present disclosure, a procedure to address the above problem is provided. In the present disclosure, a new timer and a new counter in the MCVideo server are disclosed. The new timer will be started when none of the MCVideo users are receiving the stream, even if the stream is currently being sent by other MCVideo users. And the new timer will be stopped when at least one user is authorized to receive the stream. The new counter is used to track the count of active receiving users for the stream. When there is no active receiver for the stream, the MCVideo server can use the transmission end request or the transmission revocation message to terminate the stream and inform the transmitter of the reason for termination.

[0015] According to one embodiment of the disclosure, a method of handling media transmission in a mission critical (MC) system is provided. The method includes receiving, by a MC server, a request from a first sender to send a media stream to at least one receiver. Thereafter, sending, by the MC server, a notification to the at least one receiver to receive the media stream sent by the first sender. The MC server starts a timer having a predetermined duration after sending the notification. Then, the MC server determines that the notification to receive the media stream is rejected or not accepted by the at least one receiver within the predetermined duration of the timer, and then, the MC server sends a transmission end request to the first sender to terminate the request of media stream transmission based on one of the rejection or the non-acceptance of the reception of the media stream.

[0016] According to another embodiment of the disclosure, a method of handling media transmission in a mission critical (MC) system at a MC device is provided. Thus, the method includes receiving, by the MC device, a transmission end request from a MC server to terminate a media stream transmission. Thereafter, notifying, by the MC device, a user associated with the MC device of a reason for terminating the media stream transmission, wherein the reason for terminating the transmission is lack of at least one receiver device to receive the media stream. The method further includes sending, by the MC device, a transmission end response to the MC server and terminating the transmission of the media stream to the MC server.

[0017] According to another embodiment of the disclosure, a method of handling media transmission in a mission critical (MC) system at a transmission participant device is provided. The method includes receiving, by the transmission participant device, a transmission end request from a transmission control server. The method further includes notifying, by the transmission participant device, a user associated with the transmission participant device that a media stream termination cause indicating an authorization of a client to send media is revoked due to lack of at least one participant device to receive the media stream. The method further includes sending, by the transmission participant device, a transmission end response to the transmission control server and terminating the transmission of the media stream to the transmission control server.

[0018] According to another embodiment of the disclosure, a method of handling media transmission in a mission critical (MC) at a transmission control server is provided. The method includes sending, by the transmission control server, a transmission end request message to a transmission MC device to terminate a media stream transmission when a timer (T11) defined as a stream reception idle T11 timer expires. The method further includes receiving, by the transmission control server, a transmission end response from the transmission participant device. The transmission control server then sends a transmission end notification message to at least one media receiving client, wherein the transmission end notification message indicates the transmission end from the transmission participant device.

[0019] According to another embodiment of this disclosure, a method for processing media transmission in a mission-critical (MC) at a transmission control server is provided. The method includes the transmission control server authorizing a first transmission participant device to transmit a media stream to a plurality of MC devices, and then sending a "media transmission notification" message to at least one MC device to receive the media stream transmitted by the first transmission participant device. The method also includes the transmission control server receiving a "receive media request" message from the at least one MC device to receive the media stream from the first transmission participant device. Thereafter, the transmission control server sends a "receive media response (authorization)" message to the at least one MC device to indicate authorization to receive the media stream from the first transmission participant device. Then, the transmission control server receives a "media reception end request" message to terminate reception from the at least one MC device, and then sends a "media reception end response" to indicate the termination response of media stream reception. Then, the transmission control server determines that the at least one MC device has not received a media stream based on the expiration of a predetermined duration of timer T11 (stream reception idle), and then enters a "reception idle" state based on a counter (C11) value defined as the count of active receivers of the media stream.

[0020] These and other aspects of the embodiments herein will be better understood and appreciated when considered in conjunction with the following description and accompanying drawings. However, it should be understood that while the following description indicates preferred embodiments and many specific details, it is given by way of illustration rather than limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit of the invention, and the embodiments herein encompass all such modifications.

[0021] Beneficial effects of the invention

[0022] This disclosure provides a system and method for processing media transmission in a mission-critical (MC) system or MC video system. According to the system and method of the invention, network resources can be avoided, and when the maximum number of transmissions in a group call is limited by network capacity, other participants in the group can be given the opportunity to transmit important data. Therefore, the efficiency of the MC video system can be improved. Attached Figure Description

[0023] The present disclosure is illustrated in the accompanying drawings, in which the same reference numerals denote corresponding parts in the various drawings. The embodiments herein will be better understood from the following description with reference to the accompanying drawings, in which:

[0024] Figure 1A illustrates an exemplary scenario (a) according to an embodiment of the present disclosure;

[0025] Figure 1B illustrates an exemplary scenario (b) according to an embodiment of the present disclosure;

[0026] Figure 2 An example architecture of a mission critical (MC) system for handling media transmission is shown, in accordance with an embodiment of the present disclosure;

[0027] Figure 3 A block diagram of an MC device for handling media transmission is shown, in accordance with an embodiment of the present disclosure;

[0028] Figure 4 A block diagram of a transmission control server for handling media transmission is shown, in accordance with an embodiment of the present disclosure;

[0029] Figure 5 A flow diagram for handling media transmission in an MC system is shown, in accordance with an embodiment of the present disclosure;

[0030] Figure 6 A flow diagram for handling media transmission in an MC device 101 is shown, in accordance with an embodiment of the present disclosure;

[0031] Figure 7 A flow diagram for handling media transmission in a transmission participant device is shown, in accordance with an embodiment of the present disclosure;

[0032] Figure 8 A flow diagram for handling media transmission in a transmission control server 102 is shown, in accordance with an embodiment of the present disclosure;

[0033] Figure 9 A flow diagram for handling media transmission in a transmission control server 102 is shown, in accordance with an embodiment of the present disclosure;

[0034] Figure 10 A state diagram for "transmission participant basic transmission control operation" is shown, in accordance with an embodiment of the present disclosure;

[0035] Figure 11 A state diagram for "transmission control server general transmission control operation" is shown, in accordance with an embodiment of the present disclosure;

[0036] Figure 12 A state machine diagram for "transmission control server basic transmission control operation for transmission participant" is shown, in accordance with an embodiment of the present disclosure;

[0037] Figure 13 A state machine diagram for transmission control server general receive control operation is shown, in accordance with an embodiment of the present disclosure;

[0038] Figure 14 A hardware configuration of a system in the form of a computer system is shown, in accordance with an embodiment of the present disclosure;

[0039] Figure 15a block diagram of an MC device according to embodiments of the disclosure is shown; and

[0040] Figure 16 a block diagram of an MC server according to embodiments of the disclosure is shown.

[0041] Further, those skilled in the art will appreciate that the elements in the figures are illustrated for simplicity and that not all elements of a device are necessarily shown. For example, a flow diagram illustrates the method in terms of the most prominent steps involved, to help improve understanding of aspects of the disclosure. Further, in terms of the structure of the devices, one or more components of the device can be represented in the figures by conventional symbols, and the figures can show only those specific details that are necessary to appreciate the embodiments of the present disclosure, to describe the particular implementations of the devices, in order not to obscure the drawings with details that will be readily apparent to those skilled in the art having the benefit of hereof. DETAILED DESCRIPTION

[0042] In order to facilitate an understanding of the principles of the present disclosure, reference will now be made to the embodiments illustrated in the drawings, and specific language will be used to describe the same. It will, nevertheless, be understood that no limitation of the scope of the disclosure is intended by this reference, such alterations and further modifications in the illustrated system, and such further applications of the principles of the present disclosure as illustrated therein being contemplated as would normally occur to one skilled in the art to which the disclosure relates.

[0043] Those skilled in the art will appreciate that the foregoing general description and the following detailed description are explanatory only and are not restrictive of the disclosure.

[0044] Reference throughout this specification to "an aspect", "another aspect" or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. Accordingly, appearances of the phrases "in one embodiment", "in another embodiment", and similar language in the specification, throughout the specification, can but do not necessarily all refer to the same embodiment.

[0045] The terms "comprises", "comprising", or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process or method that comprises a list of steps does not include only those steps but can include other steps not expressly listed or inherent to such process or method. Similarly, one or more devices, subsystems, elements, structures, or components not expressly shown or described can be included in or utilized by one or more devices, subsystems, elements, structures, or components described herein without departing from the scope of the present disclosure. Additionally, the terms "comprises", "comprising", or the like can be used herein to generally refer to the inclusion of one or more steps, elements, structures, or components in some examples, the term "comprises" can mean "includes, but does not

[0046] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0047] In a Mission Critical Video (MCVideo) system, when a MCVideo user in a group is granted permission to send media, all MCVideo users belonging to that group will get a media transmission notification message from the MCVideo server. Based on user interest or priority, the user can accept, reject, or ignore the notification. If none of the users in the group accept the notification within a given time, or initially some users are accepted but later all those users terminate reception by sending a reception end request to the server, the transmitter's stream should be terminated and the sending user should be informed of the reason for termination. This is mainly to avoid wasting resources and to give other users a chance to send important data. 3GPP TS 24.581 currently does not define any procedure or method to terminate the stream when there are no active receivers for that stream and to inform the transmitter. An exemplary case is shown in the accompanying drawings. FIG. 1A and FIG. IB illustrate the problems that can occur due to such conditions.

[0048] FIG. 1A illustrates an exemplary scenario (a) according to an embodiment of the disclosure. According to FIG. 1A, user A has requested to send media. The MCVideo server has sent authorization to user A and transmission notification to user C and user D. No other member in the group is sending media. Assume that user C and user D do not accept the transmission notification. Then user A is sending media but no other user is receiving it. Next, user B requests to send media but because user A's transmission is still valid, user B's request is rejected or goes to the queue.

[0049] FIG. IB illustrates an exemplary scenario (b) according to an embodiment of the disclosure. According to scenario (b), user A has requested to send media. The MCVideo server has sent authorization to user A and transmission notification to user C and user D. At this stage, no other member in the group is sending at that time. User C accepts the transmission notification but user D rejects or ignores the transmission notification. After some time, user C ends reception even though user A is still sending. At this point, user A is sending media but no other user is receiving the media. Then, user B requests to send media but because user A's transmission is still valid, user B's request is rejected or goes to the queue.

[0050] According to the above disclosed scenario, the sender A continues to send the transmission even if none of the receivers (e.g., users C or D) has accepted the transmission notification request. This results in unnecessary wastage of resources. It also prohibits, or does not allow, another user B to initiate his media transmission. Further, mission critical systems have a limit on the maximum simultaneous transmissions in a particular group call. Some participants have important disaster video stream to transmit, which can block, or delay, sending information in real time to the decision control room, thereby causing damage to the life saving work. This situation can not be good in a mission critical environment.

[0051] According to an embodiment of the present disclosure, a unique procedure is provided to address the above mentioned problem. In particular, in case none of the mission critical users in the group is receiving a particular stream due to other priorities, a new timer Tl 1 and a new counter Cl 1 are defined at the MCVideo server are used.

[0052] The new timer Tl 1 can be started when no MCVideo user is receiving the stream, even if it is currently being sent from other MCVideo users, and on expiry of the timer Tl 1, the MCVideo server will initiate a "Transmission TM End Request", denying the sending device / client to terminate sending the stream, and other users in the queue are authorized to send the media. The new timer Tl 1 can be stopped when at least one user is authorized to receive the stream. Further, the new counter Cl 1 is used to keep track of the count of active receivers for the stream. When there are no active receivers for the stream, the MCVideo server can use a transmission end request or a transmission revoke message to terminate the media stream and inform the transmitter the reason for termination.

[0053] Figure 2 An example architecture of a mission critical (MC) system for handling media transmission is shown, in accordance with an embodiment of the present disclosure. In accordance with Figure 2 The MC system 200 can include one or more MC devices 1, MC device 2,..., MC device N. For the sake of convenience, the MC device can be referred to as MC device 101 throughout the disclosure. Further, the MC device 101 can alternatively be referred to as a receiver or a sender without deviating from the scope of the present disclosure. The MC device 101 communicates with a transmission control server 102. The transmission control server 102 can alternatively be referred to as a server, MC server, or MCVideo server without deviating from the scope of the present disclosure. The transmission control server 102 is exchangeably coupled with a transmission participant device 100. The transmission participant device 100 can also communicate with an MC client 103. The transmission participant device 100 and the MC client 103 can optionally be referred to as a receiver or MC device without deviating from the scope of the present disclosure.

[0054] In accordance with Figure 2An MC group call session can be established between the MC device 100, the MC device 101 and the transmission control server 102. The plurality of transmission participant devices 100 can send a transmission request to the transmission control server 102 to transmit the media. The media can be referred to as a media stream without deviating from the scope of the present disclosure. The transmission control server 102 can grant permission to the transmission participant device 100 and send a “media transmission notification” to the other MC devices 101 to receive the media transmission. Based on the response of the MC devices 101, the media can be transmitted to only the authorized MC devices 101. New timers T11 and counters C11 can be implemented at the transmission control server 102 for handling various scenarios explained, but not limited to, in FIG. 1A and FIG. 1B.

[0055] Figure 3 A block diagram of an MC device for handling media transmission according to an embodiment of the present disclosure is shown. The MC device 101 can be a computing device including, but not limited to, a smartphone, a tablet, a smart glass, a smart network camera, a desktop computer, a laptop, a relay device, a D2D device, a V2X device, or any other computing device. The transmission participant device 100 can also be referred to as the MC device 101 and can be associated with the same group. Referring to Figure 3 The MC device 101 of an embodiment of the present disclosure can include a memory 110, a processor 120, a communicator 130, and an I / O interface 140. The memory 110 can include an application repository 110a. The application repository 110a can include applications 110aa to 110an. The processor 120 can include an MC communication session organizer 120a and an MC media engine 120b.

[0056] Figure 4 A block diagram of a transmission control server for handling media transmission according to an embodiment of the present disclosure is shown. The transmission control server 102 can include various network devices including routers, bridges, servers, computing devices, storage devices, etc. The transmission participant and control MCVideo function can be referred to as the transmission control server 102. Referring to Figure 4 The transmission control server 102 of an embodiment of the present disclosure can include a memory 102a, a processor 102b, a communicator 102c, and an I / O interface 102d. The processor 102b can include an MC media engine 102ba and an MC communication session organizer 102bb.

[0057] Figure 5 A flow diagram for handling media transmission in an MC system according to an embodiment of the present disclosure is shown. Referring to Figure 5 The method 500 can be implemented in an MC server 102 of an MC system as shown in Figure 2 Herein, reference will be made collectively to Figures 2 to 4An explanation is in order. In one implementation, the MC server 102 can perform the method 500.

[0058] According to Figure 5 At step 501, the method 500 initially includes receiving, by the MC server 102, a request from a first sender to send a media stream to at least one receiver. In one embodiment, the first sender can be one of the transport participant devices 100, while the receiver can be one of the MC devices 101. In another embodiment, the first sender and the at least one receiver belong to the same group of MC devices 101, and the media stream can include, but is not limited to, at least one of video or audio data.

[0059] Thereafter, at step 503, the MC server 102 can be configured to send a notification to the at least one receiver to receive the media stream sent by the first sender. The notification can be a type of message including, but not limited to, audio, video, text, multimedia, or user interface element type.

[0060] Thereafter, at step 505, the MC server 102 can be configured to start a timer for a predetermined duration after sending the notification. The timer can be a timer T11 defined as a stream reception idle timer, which is associated with a media stream idle. Further, the duration can be set according to the criticality of the MC system.

[0061] Thereafter, at step 507, the MC server 102 can be configured to perform a determination of whether the notification to receive the media stream is rejected or not accepted by the at least one receiver within the predetermined duration of the timer. For example, the notification to receive the media stream can be rejected due to a priority task, or the receiver can not accept the notification due to unawareness of the notification.

[0062] At step 509, the MC server 102 can be configured to send a transport end request to the first sender to terminate the media stream transport request based on one of a rejection or a non-acceptance of the reception of the media stream.

[0063] Further, referring back to step 505, after sending the notification to the at least one receiver, the MC server 102 can be configured to check the acceptance of the sent media by the at least one receiver. Based on the rejection or the non-acceptance of the reception of the media stream by the at least one receiver, the MC server 102 can be configured to terminate the transmission of the media stream from the first sender device.

[0064] In further implementations of the method 500, the MC server 102 can be configured to receive a transport end response from the first sender in response to sending the transport end request. The transport end request can include a reason for ending the transport. In one embodiment, the reason for ending the transport is due to a lack of at least one receiver to receive the media stream.

[0065] In another embodiment of the method 500, the MC server 102 can be configured to authorize a second sender to transmit a new media stream to at least one receiver after sending the transmission end request to the first sender.

[0066] In a further implementation of the method 500, the MC server 102 can be configured to accept a notification of receiving the media stream. Accepting the notification of receiving the media stream can include receiving, by the MC server 102, a request to receive the media stream from the at least one receiver. For example, when the notification is accepted by the at least one receiver, the receiver sends a request to the MC server to receive the media stream in response.

[0067] After the above steps, the MC server 102 can be configured to send a response to the at least one receiver to notify the receiver about the receiving authorization permission. Thereafter, the MC server 102 can be configured to perform an increment of a counter value for each active receiver from the at least one receiver based on the authorized receiving. For example, the counter C11 defined above is used to count the active receivers for the stream.

[0068] After the above step of accepting the notification of receiving the media stream, the MC server 102 can receive a request to terminate the receiving of the media stream from the at least one receiver. Thereafter, the MC server 102 can be configured to send a response to indicate the termination of the media stream receiving. Further, the MC server 102 can be configured to decrement the counter value by 1 for each termination of the media stream received from one of the at least one receiver. If the counter value reaches a lower limit, the MC server 102 enters an“idle receiving” state. Thereafter, if the timer expires, the MC server 102 determines that none of the at least one receiver receives the media stream. After the timer expires, the MC server 102 can be configured to send a transmission end request to the first sender to terminate the transmission.

[0069] In another implementation of the method 500, the MC server 102 can be configured to restart the timer for a predetermined duration when the counter value reaches a minimum predetermined value after the decrement of the counter value or when the MC server 102 sends the“media transmission notification” message to the MC device 102.

[0070] In a further implementation of the method 500, the MC server 102 can be configured to terminate the timer if the at least one receiver accepts the notification of receiving the media or if the media transmission is ended by the transmission control server 102 by sending the transmission end notification message.

[0071] Figure 6 A flowchart for processing a media transmission in the MC device 101 according to an embodiment of the present disclosure is shown. Referring toFigure 6 The method 600 can be implemented in the MC device 101 of the MC system 200, as shown in Figure 2 Herein, the method 600 will be explained in combination with Figures 2 to 5 In one implementation, the MC device 101 can perform the method 600.

[0072] According to Figure 6 At step 601, the method 600 includes receiving, by the MC device 101, a transmission end request from the MC server 102 for terminating the media stream transmission, further to step 509 as shown in Figure 5

[0073] Thereafter, at step 603, the method 600 includes notifying, by the MC device 101, a user associated with the MC device 101 of a reason for terminating the media stream transmission. In one embodiment, the reason for ending the transmission is due to lack of at least one receiver device for receiving the media stream. Accordingly, the user holding the MC device 101 is notified of the end of the transmission and the reason for termination.

[0074] After step 603, at step 605, the MC device 101 can be configured to send a transmission end response to the MC server 102, and thereafter at step 607, the MC device 101 can be configured to terminate the transmission of the media stream to the MC server 102.

[0075] Figure 7 A flowchart for handling media transmission in a transmission participant device according to an embodiment of the present disclosure is shown. Referring to Figure 7 The method 700 can be implemented in the transmission participant device 100 of the MC system 200, as shown in Figure 2 Herein, the method 700 will be explained in combination with Figures 2 to 6 In one implementation in the transmission participant device 100, the method 700 can be performed.

[0076] According to Figure 7 At step 701, the method 700 includes receiving, by the transmission participant device 100, a transmission end request from the transmission control server 102, further to step 509 as shown in Figure 5

[0077] Thereafter, at step 703, the transmission participant device 100 can be configured to notify a user associated with the transmission participant device 100 of a media stream termination reason. The media stream termination reason indicates that the client's permission to send the media stream is being revoked due to lack of at least one other transmission participant device 100 to receive the media stream.

[0078] Subsequently, at step 705, the transmission participant device 100 can be configured to send a transmission end response to the transmission control server 102.​​

[0079] Thereafter, at step 707, the transmitting participant device 100 can be configured to terminate sending the media stream to the transmission control server 102.

[0080] According to Figure 7 , the transmitting participant device 100 can be configured to enter a “call release” state for a broadcast group call or a “not allowed to send” state for a normal or non-broadcast group call. For example, if the call is initiated as a broadcast group call, the transmitting participant device 100 will enter the call release state after sending the transmission end response message, i.e., after step 705. For any other type of call after step 705, the transmitting participant device 100 can enter the “not allowed” state. For example, the transmitting participant device 100 can be an MC device 101 and is associated with the same group.

[0081] Figure 8 A flowchart for processing media transmission in the transmission control server 102 according to an embodiment of the disclosure is shown. Referring to Figure 8 , the method 800 can be implemented in the transmission control server 102 of the MC system 200, as Figure 2 shown. It will be explained here in combination with Figures 2 to 7 . In the implementation in the transmission control server 102, the method 800 can be performed. Figure 8 The method disclosed in Figure 5 is according to another embodiment of the transmission control server 102 disclosed in

[0082] According to Figure 8 , at step 801, the transmission control server 102 is configured to send a transmission end request message to the transmitting MC device 101 for terminating the transmission of the media stream upon expiry of a timer T11. The timer T11 is referred to as a stream reception idle T11 timer. In some embodiments, the transmission end request includes at least one of the “no receiving participant” cause in the “reject reason” field of the transmission end request, which indicates the reason for terminating the media stream

[0083] At step 803, the transmission control server 102 is configured to receive a transmission end response from the transmitting participant device 100 that is transmitting. Thereafter, at step 805, the transmission control server 102 is configured to send a transmission end notification message to at least one media receiving client. In some embodiments, the transmission end notification message indicates the transmission end from the transmitting participant device 100.

[0084] In one implementation of the method 800, the transmission control server 102 is further configured to determine whether there are any media transmission requests in the queue. If there are any media transmission requests in the queue, the transmission control server 102 is configured to remove the media transmission request from the queue. Thereafter, the transmission control server 102 can be configured to authorize the permission to send the media stream to the second transmission participant device 100. In step 801, after sending the transmission end request message to the transmission participant device 100, the transmission control server 102 enters the “pending transmission cancellation” state.

[0085] In another implementation of the method 800, further to step 803, after receiving the transmission end response message from the transmission participant device 100, the transmission control server (102) in the general transmission control operation state machine enters the “transmission idle” state if the counter value (Cx) reaches the minimum limit during the simultaneous transmission of the media stream, or enters the “transmission occupied” state if the counter value (Cx) does not reach the minimum limit. The counter Cx is the same as the counter C11 discussed above. That is, if there is no other transmission participant device 100 transmitting media at this time, the transmission control server 102 in the general transmission control operation state enters the “transmission idle” state, or if at least one transmission participant device 100 is transmitting media at this time, enters the “transmission occupied” state.

[0086] In another implementation of the method 800, further to step 803, after receiving the transmission end response message from the transmission participant device 100, the transmission control server 102 operating in the basic transmission control operation state machine stops the timer T3. The timer T3 is defined as a transmission cancellation timer. In addition, the transmission control server 102 can be configured to enter the ‘U: not allowed and transmission idle’ state.

[0087] The basic transmission control operation can be defined as one state machine per user or per group, and the general transmission control operation can be defined as one state machine per group. For example, if there is a group call of three users (MC devices), there can be one general transmission control operation state machine instance and three basic transmission control operation instances (one instance per user per group) in the server.

[0088] Figure 9 A flowchart for processing media transmission in the transmission control server 102 according to an embodiment of the disclosure is shown. Referring to Figure 9 , the method 900 can be implemented in the transmission control server 102 of the MC system 200 as shown in Figure 2 . Here, reference will be made to Figures 2 to 8 for explanation in combination. In the implementation in the transmission control server 102, the method 900 can be executed. Figure 9The method disclosed in Figure 5 and Figure 8 another embodiment of the transmission control server 102 disclosed in

[0089] According to Figure 9 , at step 901, the transmission control server 102 can be configured to authorize the first transmission participant device 100 to send a permission to transmit a media stream to the plurality of MC devices 101. Thereafter, at step 903, the transmission control server 102 can be configured to send a "media transmission notification" message to the at least one MC device 101 to receive the media stream transmitted by the first transmission participant device 100. At step 905, the transmission control server 102 can be configured to receive a "receive media request" message from the at least one MC device 101 to receive the media stream from the first transmission participant device 100. After step 905, at step 907, the transmission control server 102 can be configured to send a "receive media response (authorization)" message to the at least one MC device 101 to indicate the authorized permission to receive the media stream from the first transmission participant device 100. Thereafter, at step 909, the transmission control server 102 can be configured to receive a "media reception end request" message from the at least one MC device 101 to terminate the reception. At step 911, the transmission control server 102 can be configured to send a "media reception end response" message to the MC device 101 to indicate the termination response of the media stream reception. Thereafter, at step 913, the transmission control server 102 can be configured to determine that the at least one MC device 101 is not receiving the media stream. The determination is based on the expiry of a predetermined duration of a timer T11 (stream reception idle timer). At step 915, the transmission control server 102 enters a "reception idle" state based on the counter C11 value. The counter value provides a count of active receivers that are receiving the media stream.

[0090] In some embodiments, the counter C11 value is initialized to zero. Further, the counter C11 is associated with a sender synchronization source (SSRC) or a user ID of the at least one MC device 101. Further, the timer T11 is defined as a stream reception idle timer that is started for a predetermined duration after the transmission control server 102 sends the "media transmission notification" message to the at least one MC device 101 or if the counter (C11) value reaches a minimum limit.

[0091] In some embodiments, for each "receive media response (authorization)" sent to the MC device 101, the counter C11 value is incremented by 1 and for each "media reception end request" or "media reception end response" message received from the MC device 101, the counter C11 value is decremented by 1.

[0092] In some embodiments, the transport control server 102 can disable (or stop) the timer T11 if the at least one MC device 101 receives the media stream from the transport participant device (100) by sending the authorization permission via the 'Receive Media Request (Authorization)' message, or if the media transport is ended by the transport control server 102 by sending the 'Transport End Notification' message to the at least one MC device 101. Thus, after the expiry of the timer T11 (stream reception idle period expiry), the MC server 102 sends an indication to terminate the transport. The various state machine diagrams with respect to the various entities described above are explained in detail in the subsequent paragraphs.

[0093] Figure 10 A state diagram of 'Transport Participant Basic Transport Control Operation' is shown in accordance with an embodiment of the disclosure. New procedures have been added to receive the transport end request from the transport control server 102 and to send the transport end response from the transport participant device 100. Figure 10 The state diagram shown in FIG. 10 corresponds to the state diagram shown in FIG. 9 with respect to Figure 7 The method 700 shown in FIG. 11. For the sake of brevity of the disclosure, explanation of similar steps is avoided. The detailed information of the state machine is explained as follows:

[0094] In one embodiment, when the state 1001 'Send permission obtained' is reached, and on receiving the 'Transport End Request message' 1003 or 1005 from the transport control server 102, the transport participant device 100:

[0095] 1. Should inform the user that the permission to send RTP media is being revoked;

[0096] 2. Can provide the user with information about the reason for the authorization to terminate sending media;

[0097] 3. Should request the media in the MCVideo client 103 to discard any remaining buffered RTP media packets and stop forwarding encoded video to the MCVideo server 102; and

[0098] 4. Should send the transport end response message to the transport control server 102.

[0099] 5. If the session is not a broadcast group call, or if the A bit in the transport indicator field is set to '1' (normal call), should enter the 'U: No send permission' state; and

[0100] 6. If the session is started as a broadcast group call:

[0101] a. Should indicate to the MCVideo client 103 that the media transport is complete; and

[0102] b. Should enter the 'Release call' state.

[0103] Figure 11 A state diagram for "Transport Control Server General Transport Control Operation" is shown in accordance with embodiments of the disclosure. A new procedure is added to handle the transport end request message and forward it to the "Transport Control Server Basic Transport Control State Machine". Figure 11 The state diagram shown in FIG. 12 corresponds to the method 500, 800, and 900 explained in FIGS. 5, 8, and 9, respectively, with respect to Figure 5 、 Figure 8 、 Figure 9 The method 500, 800, and 900 explained in FIGS. 5, 8, and 9, respectively. For the sake of brevity of the disclosure, explanation of similar steps is avoided. The detailed information of the state machine is explained as follows:

[0104] In one embodiment, when in state 1101 "G: Transport In-Progress", and upon receiving a transport end request message, the transport control arbitration logic in the transport control server 102:

[0105] 1. Should stop timer T4 (Transport Grant) if running;

[0106] 2. Should include a reject reason field, where the <Reject Reason> value is set to #8 (No receiving participants);

[0107] i. May include an additional text string in the <Reject Phrase> value explaining the reason for rejecting the transport request; and

[0108] 3. Should enter the "G: Pending Transport Revocation" state 1109.

[0109] In some embodiments, the transport control arbitration logic in the transport control server 102 enters the "G: Pending Transport Revocation" state 1109 after sending a transport revocation or transport end request message to the allowed transport participant devices 100. In this state, the MCVideo server 102 forwards the RTP media packets in the MCVideo call to the other transport participant devices 100.

[0110] In some embodiments, the functions of the transport end request message and the transport revocation message sent from the server 102 are the same on both the client and the server side, and the handling of the transport end request message is added in the "G: Pending Transport Revocation" state 1109 in this document. For this purpose, a new state can also be created later if needed.

[0111] In some embodiments, when entering the 'G: Pending Transport Revocation' state 1109, the transport control arbitration logic in the transport control server 102:

[0112] 1. A transmission revoke or transmission end request message shall be sent to the allowed transmission participants 100. The transmission revoke or transmission end request message:

[0113] a. shall include the reason for sending the "transmission revoke message" or "transmission end request" in the <REJECT-REASON> value in the reject reason field; and

[0114] b. shall include the transmission indicator field with the appropriate indication if the group call is a broadcast group call, a system call, an emergency call, an impending permanent call, or a temporary group session; and

[0115] 2. The general state shall be set to "G: pending transmission revoke" 1109.

[0116] In one embodiment, when in the state "G: pending transmission revoke" 1109, upon receipt of the transmission end response message 1107, the transmission control arbitration logic in the transmission control server 102 performs the following steps:

[0117] 1. The media distributor in the MCVideo server shall be requested to stop forwarding RTP media packets for the requesting transmission participant; and

[0118] 2. If the counter Cx (concurrent transmission video) has not reached its lower limit, then decrement the counter Cx (concurrent transmission video) by 1;

[0119] 3. If Cx (concurrent transmission video) has reached the lower limit, then enter the "G: transmission idle" state.

[0120] 4. If Cx (concurrent transmission video) has not reached the lower limit, and if the active transmission request queue is not empty, then the transmission control server 102:

[0121] a. shall select a queued transmission request from the top of the active transmission request queue;

[0122] b. shall delete the queued transmission request from the active transmission request queue; and

[0123] c. shall enter the "G: transmission in use" state 1101.

[0124] Figure 12 A state machine diagram for "transmission control server basic transmission control operations oriented to transmission participant operations" in accordance with an embodiment of the present disclosure is shown. New procedures have been added to send a transmission end request from the transmission control server 102 to the transmission participant device 100, and to process a transmission end response from the transmission participant device 100. Figure 12 The state diagram explained in the middle corresponds to the state diagram explained in the Figure 5 , Figure 8 ,Figure 9 The method 500, 800, 900 explained in the middle. For the sake of brevity of the present disclosure, explanations of similar steps are avoided. Detailed information of the state machine is explained as follows:

[0125] In some embodiments, in state 1201 "U: Allowed", when a transmission end request message is received from the transmission control server 102, the transmission control interface facing the MCVideo client 103 in the transmission control server 102:

[0126] 1. The "transmission end request" message shall be forwarded to the associated transmission participant 100; and

[0127] 2. The state 1203 "U pending transmission withdrawal" shall be entered.

[0128] In one embodiment, in relation to state 1203 "U: pending transmission withdrawal", the transmission control interface facing the MCVideo client 103 in the transmission control server 102 uses this state during the grace period after sending the transmission withdrawal or transmission end request message.

[0129] In this state, the timer T3 (transmission withdrawal) is running.

[0130] In some embodiments, the functions of the transmission end request message and the transmission withdrawal message sent from the transmission control server 102 are the same on the client and server side, the processing of the transmission end request message is added in the "U: pending transmission withdrawal" state 1203, and the timer T3 (transmission withdrawal) is also used for the transmission end request message. For this purpose, a new state and timer can also be created later if necessary.

[0131] In some embodiments, in state "U: pending transmission withdrawal" 1203, when the timer T3 (transmission withdrawal) expires, the transmission control interface facing the MCVideo client 103 in the transmission control server 102:

[0132] 1. The "transmission withdrawal" or "transmission end request" message shall be re-sent to the associated transmission participant 100. The transmission withdrawal message or the transmission end request:

[0133] a. Shall include the same rejection reason field and the same transmission indicator field as in the previously sent transmission withdrawal message or transmission end request;

[0134] 2. Timer T3 (transmission withdrawal) shall be started; and

[0135] 3. The "U: pending transmission withdrawal" state 1203 shall be maintained.

[0136] In a further implementation, the number of times the transport control server 102 retransmits the transport revocation message or the transport end request and the action taken when the transport control server 102 abandons are implementation options. However, it is recommended that the MCVideo client 103 be disconnected from the MCVideo call when the transport control server 102 abandons.

[0137] In one embodiment, in the state "U: pending transport revocation" 1203, and upon receiving a transport end response message from the associated transport participant device 100, the transport control interface faces the MCVideo client 103 in the transport control server 102:

[0138] 1. If the first bit in the subtype of the transport end response message is set to '1' (ack required), a transport control Ack message should be sent. The transport control Ack message:

[0139] a. should include a message type field set to '1' (transport end response); and

[0140] b. should include a source field set to '2' (control MCVideo function is the source);

[0141] 2. If timer T3 (transport revocation) is running, timer T3 (transport revocation) should be stopped; and

[0142] 3. The transport end response message should be forwarded to the transport control server arbitration logic; and

[0143] 4. The state "U: not allowed and transport idle" should be entered.

[0144] Figure 13 A state machine diagram for the transport control server general receive control operation is shown in accordance with an embodiment of the present disclosure. A new timer and a new counter are introduced. The new timer will be started when no MCVideo user is receiving the stream, even if the stream is currently being sent from other MCVideo users. And the new timer can be stopped when at least one user is granted permission to receive the stream. The new counter is used to track the count of active receivers for the stream. When there is no active receiver for the stream, the general receive control operation state machine will inform the transport control arbitration logic to terminate the ongoing transport. Figure 13 The state diagram shown in FIG. 6 corresponds to the method 500 explained in relation to Figure 5 , Figure 8 , and Figure 9 FIGS. 5, 8, and 9. For the sake of brevity of the present disclosure, explanation of similar steps is avoided. The details of the state machine are explained as follows:

[0145] In some embodiments, in state 1301 "Gr: Receive Idle", upon receiving a media transmission request notification message, the receive control arbitration logic in the transmission control server 102:

[0146] 1. A media transmission notification message should be sent to all other transmission participants 100. The media transmission notification message:

[0147] a. Should include a receive mode field set to '0' indicating an automatic receive mode if the group call is a broadcast group call, a system call, an emergency call, an impending call;

[0148] b. Should include a receive mode field set to '1' indicating a manual receive mode if the group call is not a broadcast group call, a system call, an emergency call, or an impending call.

[0149] 2. A timer T11 (stream receive idle) should be started and associated with the transmitter SSRC or UserId.

[0150] 3. A counter C11 (count of active receivers for the stream) should be initialized to '0' and associated with the transmitter SSRC or UserId.

[0151] 4. Should remain in the "Gr: Receive Idle" state.

[0152] In some embodiments, in state 1301 "Gr: Receive Idle", upon receiving a receive media request message, the receive control arbitration logic in the transmission control server 102:

[0153] 1. If the "receive media request" is rejected:

[0154] a. A "receive media response (reject)" message should be sent. The "receive media response" message:

[0155] i. If the first bit in the sub-type of the receive media response message is set to '1' (ack required), a transmission control Ack message should be sent; and

[0156] ii. Should include a result field set to '0' (receive media rejected); and

[0157] b. Should remain in the "Gr: Receive Idle" state 1301; or

[0158] 2. If the "receive media request" is authorized:

[0159] a. Timer T5 (receive inactivity) should be stopped;

[0160] b. Timer T11 (stream receive idle) should be stopped if it is running;

[0161] c. Increment the counter C11 (count of active receivers of the stream) associated with the transmitter SSRC by 1;

[0162] d. The SSRC of the transmission participant 100 requesting to receive media should be stored until reception associated with the transmission request is complete;

[0163] e. A receive media response message should be sent. The receive media response message:

[0164] i. If the first bit in the sub-type of the receive media response message is set to '1' (acknowledge required), a transmission control Ack message should be sent; and

[0165] ii. Should include a result field set to '1' (receive media granted);

[0166] f. If C7 (accept reception) has not reached its upper limit, it should be incremented by 1; and

[0167] g. The "Gr: accept reception" state 1303 should be entered.

[0168] In one embodiment, in the state 1301 "Gr: reception idle" and upon receiving a transmission end notification, the reception control arbitration logic in the transmission control server 102:

[0169] 1. A "transmission end notification" message should be sent to all other transmission participants.

[0170] 2. If running, a timer T11 (stream reception idle) associated with the transmitter SSRC should be stopped;

[0171] 3. The "Gr: reception idle" state should be maintained.

[0172] In one embodiment, in the state 1301 "Gr: reception idle" and upon expiration of the timer T11 (stream reception idle), the reception control arbitration logic in the transmission control server 102:

[0173] 1. Should communicate with the transmission control arbitration logic in the transmission control server 102 to terminate the stream associated with the expired timer T11.

[0174] 2. The "Gr: reception idle" state 1301 should be maintained.

[0175] As an example, the termination of the stream by sending a transmission revocation message or a transmission end request message is determined based on a local policy of the MCVideo server 102.

[0176] In some embodiments, in state 1303 "Gr: Accepting Reception", and upon receiving a reception media request message, the reception control arbitration logic in the transport control server 102:

[0177] 1. If the reception media request is rejected:

[0178] a. A reception media response (reject) message should be sent. The reception media response message:

[0179] i. sets the first bit in the subtype of the reception media response message to '1' (ack required), sends a transport control Ack message; and

[0180] ii. shall include a result field set to '0' (reception media rejected); and

[0181] b. The "Gr: Accepting Reception" state 1303 should be maintained; or

[0182] 2. If the reception media request is granted:

[0183] a. Timer T5 (inactivity) should be stopped;

[0184] b. If running, the timer T11 (stream reception idle) associated with the transmitter SSRC should be stopped;

[0185] c. The counter C11 (count of active receivers for the stream) associated with the transmitter SSRC should be incremented by 1;

[0186] d. The SSRC of the transmitting participant 100 that requested reception media should be stored until reception completion associated with this transmission request;

[0187] e. A reception media response (grant) message should be sent. The reception media response message:

[0188] i. sets the first bit in the subtype of the reception media response message to '1' (ack required), sends a transport control Ack message; and

[0189] ii. shall include a result field set to '1' (reception media granted);

[0190] f. Timer T6 (reception grant) should be started;

[0191] g. If C7 (accepting reception) has not reached its upper limit, it should be increased by 1; and

[0192] h. The "Gr: Accepting Reception" state 1303 should be maintained.

[0193] In one embodiment, in state 1303 "Gr: Accepting Reception", and upon receiving a reception media end request message, the reception control arbitration logic in the transport control server 102:

[0194] 1. A reception media end response message shall be sent. The reception media end response message:

[0195] i. If the first bit in the subtype of the reception media end response message is set to '1' (ack required), a transport control Ack message shall be sent.

[0196] ii. The message type field set to 'y' (reception media end authorized) shall be included;

[0197] 2. Timer T6 (reception authorization) shall be stopped;

[0198] 3. If the counter C11 (count of active receivers for the stream) has not reached its lower limit, the counter C11 is decremented by 1;

[0199] 4. If C11 has reached its lower limit, timer T11 (stream reception idle) shall be started.

[0200] 5. If C7 (accepting reception) has not reached its lower limit, C7 is decremented by 1;

[0201] 6. If C7 has not reached its lower limit, the "Gr: Accepting Reception" state shall be maintained.

[0202] 7. If C7 has reached its lower limit, the "Gr: Reception Idle" state shall be entered.

[0203] In some embodiments, when all transport participants 100 have stopped reception, the decision to start the same timer T11 or a new timer can be made based on the local policy of the MCVideo server 102.

[0204] In one embodiment, in state 1303 "Gr: Accepting Reception", and upon receiving a reception media end response message, the reception control arbitration logic in the transport control server 102:

[0205] 1. If the first bit in the subtype of the reception media end response message is set to '1' (ack required), a transport control Ack message shall be sent.

[0206] 2. Timer T6 (reception authorization) shall be stopped;

[0207] 3. If the counter C11 (count of active receivers for the stream) has not reached its lower limit, the counter C11 is decremented by 1;

[0208] 4. If C11 has reached its lower limit, timer T11 (stream reception idle) should be started.

[0209] 5. If its lower limit has not been reached, C7 (accept reception) is decremented by 1 ;

[0210] 6. If C7 has not reached its lower limit, the "Gr: accept reception" state 1303 should be maintained.

[0211] 7. If C7 has reached its lower limit, the "Gr: reception idle" state 1301 should be entered.

[0212] In one embodiment, in the "Gr: accept reception" state 1303, and upon receipt of a media transmission request notification message from the reception control arbitration logic in the transmission control server 102:

[0213] 1. A media transmission notification message should be sent to all other transmission participants 100. The media transmission notification message:

[0214] a. Should include a reception mode field set to "0" indicating an automatic reception mode if the group call is a broadcast group call, a system call, an emergency call, or an upcoming call; and

[0215] b. Should include a reception mode field set to '1'indicating a manual reception mode if the group call is not a broadcast group call, a system call, an emergency call, or an upcoming call; and

[0216] 2. Timer T11 (stream reception idle) should be started and associated with the transmitter SSRC or UserId present in the media transmission notification message.

[0217] 3. Counter C11 (count of active receivers of the stream) should be initialized to 0 and associated with the transmitter SSRC or UserId present in the media transmission notification message.

[0218] 4. The "Gr: accept reception" state 1303 should be maintained.

[0219] In one embodiment, in the "Gr: accept reception" state 1303, and upon receipt of a transmission end notification message, the reception control arbitration logic in the transmission control server 102:

[0220] 1. A media transmission end notification message should be sent to all other transmission participants 100.

[0221] 2. If running, timer T11 (stream reception idle) associated with the transmitter SSRC should be stopped;

[0222] 3. C7 (accepted) should be decreased by the value of C11 (count of active receivers of the stream) related to the transmitter SSRC; in one implementation, the difference of the values of C7 and C11 can be considered as a counter value for determining the state of the transmission control server 102. In particular, after the counter value reaches a minimum limit, the transmission control server 102 enters the "Gr: accept idle" state 1301, otherwise the transmission control server 102 enters the "Gr: accept receiving" state 1303.

[0223] 4. If C7 has not reached its lower limit, it should be kept in the "Gr: accept receiving" state 1303.

[0224] 5. If C7 has reached its lower limit, it should enter the "Gr: accept idle" state 1301.

[0225] In one embodiment, in the state 1303 "Gr: accept receiving", and upon expiration of the timer T11 (stream receiving idle), the reception control arbitration logic in the transmission control server 102:

[0226] 1. Should communicate with the transmission control arbitration logic in the transmission control server 102 to terminate the stream associated with the expired timer T11.

[0227] 2. Should be kept in the "Gr: accept receiving" state 1303.

[0228] In some embodiments, the termination of the stream by sending a transmission cancel message or a transmission end request message is decided based on the local policy of the MCVideo server 102.

[0229] In one embodiment, when the transmission of the stream is terminated due to the expiration of the T11 timer, the transmission end request with the rejection reason #8 sent from the transmission control server 102 is explained in detail below.

[0230] Reason #8 - No receiver

[0231] The <reject reason> value set to '8' indicates that the permission of the MCVideo client 103 to send media is being revoked since there is no participant to receive the stream.

[0232] In some embodiments, a rejection reason value field is added to the transmission end request message to indicate the reason for ending the transmission. The basic format of the transmission end request message can be seen in Table 1:

[0233] [Table 1]

[0234]

[0235] The reject reason field of the transmission end request message includes a <reject reason> cause value in the reject reason field, which explains the reason why the transmission control server 102 wants the transmission participant 100 to stop transmitting the media, and can be followed by additional information. Thus, the length of the packet can vary depending on the value of the reject reason.

[0236] In some embodiments, a timer T11 (stream reception idle timer) is used in the transmission control server 102. The timer will be started even if the stream is currently being sent from other MCVideo users, when no MCVideo user is receiving the stream. The timer can be stopped when at least one user is authorized to receive the stream basic details of the timer T11 shown in Table 2.

[0237] [Table 2]

[0238]

[0239]

[0240] In some embodiments, a counter C11 (count of active receivers for a stream) is used in the transmission control server 102, and the timer stores the count of active receiving users for the stream. The basic details of the counter C11 are shown in Table 3.

[0241] [Table 3]

[0242]

[0243] In summary, the above provides the following:

[0244] 1. Handling of transmission (TM) end request and response messages and state transitions based on the messages at the client and server side.

[0245] 2. Introducing a new counter C11 (count of active receivers for a stream) to store the count of active receivers per stream. Counter initialization / increment / decrement based on different message handling and state transitions based on counter values are provided.

[0246] 3. New timer T11 (stream reception idle) in the server state machine is being implemented and timer stop / start / expiry handling.

[0247] 4. Method to terminate a stream, with the help of the newly introduced "reject reason value" field and reason, to inform the sending user of the reason for termination when no user is receiving the stream. All race conditions in the transmission (TM) end request message in the transmission control server 102 are handled.

[0248] Accordingly, because the maximum number of transmissions in a group call is limited by network capacity, the present disclosure avoids wasting network resources and gives other participants in the group a chance to transmit important data. This solution improves the efficiency of the Mission Critical Video (MCVideo) system in high network congestion situations in which the Mission Critical Video system typically operates.

[0249] Figure 14 A hardware configuration of a system in the form of computer system 1400 in accordance with an embodiment of the present disclosure is shown. Computer system 1400 can include a set of instructions that can be executed to cause computer system 1400 to perform any one or more of the methods disclosed herein. Computer system 1400 can operate as a standalone device or can be connected, e.g., using a network, to other computer systems or peripheral devices.

[0250] In a networked deployment, computer system 1400 can operate in the capacity of a server or as a client user computer in server-client user network environment, or as a peer computer system in a peer-to-peer (or distributed) network environment. Computer system 1400 can also be implemented as or incorporated into a variety of devices, such as a personal computer (PC), a tablet PC, a personal digital assistant (PDA), a mobile device, a palmtop computer, a laptop computer, a desktop computer, a communications device, a wireless telephone, a land-line

[0251] Computer system 1400 can include a processor 1402, such as central processing unit (CPU), a graphics processing unit (GPU), or both. Processor 1402 can be a component in a variety of systems. For example, processor 1402 can be part of a standard personal computer, a workstation, or a server. Processor 1402 can be one or more general processors, digital signal processors, application-specific integrated circuits, field programmable gate arrays, servers, networks, digital circuits, analog circuits, combinations thereof, or other now known or later developed devices for analyzing and processing data. Processor 1402 can implement software programs, such as code produced by a programming language.

[0252] The computer system 1400 can include a memory 1404, e.g., a memory 1404 that can communicate via a bus 1408. The memory 1404 can include, without limitation, a variety of types of volatile and non-volatile storage means including, without limitation, random access memory (RAM), read only memory (ROM), programmable read only memory (PROM), electronically programmable read only memory (EPROM), electronically erasable read only memory (EEPROM), flash memory, a magnetic data media, an optical data media, or the like. In one example, the memory 1404 includes a cache or random access memory for the processor 1402. In alternative examples, the memory 1404 is separate from the processor 1402, such as a cache, system memory, or other memory. The memory 1404 can be an external storage device or a database for storing data. The memory 1404 is operable to store instructions executable by the processor 1402. The functions, acts or tasks illustrated in the figures or described herein can be performed by the programmed processor 1402 operating the instructions stored in the memory 1404. The functions, acts or tasks are independent of the particular type of instructions set, storage media, processor or processing strategy and can be performed by software, hardware, integrated circuits, firm ware, micro-code and the like, working individually or in combination. Similarly, the processing strategy can include multiprocessing, multitasking, parallel processing and the like.

[0253] As shown, the computer system 1400 can or can not further include a display unit 1410, such as a liquid crystal display (LCD), an organic light emitting diode (OLED), a flat panel display, a solid state display, a cathode ray tube (CRT), a projector, a printer or other now known or later developed display device for outputting determined information. The display 1410 can serve as an interface for a user to view the functioning of the processor 1402, or specifically, to interface with software stored in the memory 1404 or the drive unit 1416.

[0254] Further, the computer system 1400 can include an input device 1412 configured to allow a user to interact with any of the components of system 1400. The computer system 1400 can also include a disk or optical drive unit 1416. The disk drive unit 1416 can include a computer-readable medium 1422 on which is embedded one or more sets of instructions 1424, such as software. Also, the instructions 1424 can embody one or more of the methodologies or flow diagrams described herein. In a particular example, the instructions 1424 can reside completely, though not necessarily entirely, within the memory 1404 or the processor 1402 during execution thereof by the computer system 1400.

[0255] The present application relates to a computer readable medium including instructions 1424 or receiving and executing instructions 1424 in response to a propagated signal so that a device connected to a network 1426 can communicate voice, video, audio, images or any other data over the network 1426. Further, the instructions 1424 can be sent or received over the network 1426 via a communication port or interface 1420 or using a bus 1408. The communication port or interface 1420 can be part of the processor 1402 or can be a separate component. The communication port 1420 can be created in software or can be a physical connection in hardware. The communication port 1420 can be configured to connect with a network 1426, external media, the display 1410, or any other components in system 1400, or combinations thereof. The connection with the network 1426 can be a physical connection, such as a wired Ethernet connection or can be established wirelessly as discussed later. Likewise, the additional connections with other components of the system 1400 can be physical or can be wireless connections.

[0256] The network 1426 can comprise a wired network, a wireless network, an Ethernet AVB network, or combinations thereof. The wireless network can be a cellular telephone network, an 802.11, 802.16, 802.20, 802.1Q or WiMax network. Further, the network 1426 can be a public network, such as the Internet, a private network, such as an intranet, or combinations thereof, and can utilize various networking protocols now available or later developed including, but not limited to, TCP / IP based networking protocols. The system is not limited to operation with any particular standard and protocol. For example, standards for Internet and other packet-switched network transmissions (e.g., TCP / IP, UDP / IP, HTML, and HTTP) can be used.

[0257] Figure 15 A block diagram illustrating an MC device, such as MC device 101, according to embodiments of the present application is described.

[0258] Referring to Figure 15 The MC device 1500 includes a transceiver 1510, a controller 1520, and a memory 1530.

[0259] The transceiver 1510 is capable of transmitting / receiving a signal to / from other MC devices, servers, or entities according to embodiments of the present disclosure.

[0260] The controller 1520 is capable of controlling operations of the MC device 1500. The controller 1520 is capable of controlling the MC device 1500 to perform operations related to the MC device 1500 as described in embodiments of the present disclosure.

[0261] The memory 1530 is capable of storing at least one of information related to the MC device 1500 and information transmitted / received via the transceiver 1510.

[0262] Figure 16 A block diagram of an MC server, such as the MC server 102, according to an embodiment of the disclosure is shown.

[0263] Referring to Figure 16 The MC server 1600 includes a transceiver 1610, a controller 1620, and a memory 1630. The MC server 1600 can be a transmission control server 102 as described in embodiments of the disclosure.

[0264] The transceiver 1610 is capable of transmitting / receiving a signal to / from other MC devices, servers, or entities according to embodiments of the disclosure.

[0265] The controller 1620 is capable of controlling the operation of the MC server 1600. The controller 1620 is capable of controlling the MC server 1600 to perform operations related to the MC server 1600 as described in embodiments of the disclosure.

[0266] The memory 1630 is capable of storing at least one of information related to the MC server 1600 and information transmitted / received via the transceiver 1610.

[0267] According to an embodiment of the disclosure, a method of processing media transmission in a mission critical (MC) system is provided. An MC server receives a request from a first transmitter to transmit a media stream to at least one receiver; the MC server transmits a notification to the at least one receiver to receive the media stream transmitted by the first transmitter; the MC server starts a timer having a predetermined duration after transmitting the notification; it is determined by the MC server that the notification to receive the media stream is rejected or not accepted by the at least one receiver within the predetermined duration of the timer; the MC server transmits a transmission end request to the first transmitter to terminate the media stream transmission request based on one of the rejection or the non-acceptance of the reception of the media stream.

[0268] In an embodiment of the disclosure, wherein after transmitting the notification to the at least one receiver, the method further comprises: checking, by the MC server, the acceptance of the transmitted media by the at least one receiver; and terminating, by the MC server, the transmission of the media stream from the first transmitter device based on one of the rejection or the non-acceptance of the reception of the media stream by the at least one receiver.

[0269] In an embodiment of the disclosure, the method further comprises receiving, by the MC server, a transmission end response from the first sender in response to sending the transmission end request, wherein the transmission end request includes a reason for ending the transmission, and wherein the reason for ending the transmission is due to lack of at least one receiver for receiving the media stream.

[0270] In an embodiment of the disclosure, the method further comprises authorizing, by the MC server, the second sender to transmit a new media stream to the at least one receiver after sending the transmission end request to the first sender.

[0271] In an embodiment of the disclosure, the method further comprises accepting the notification of receiving the media stream, comprising: receiving, by the MC server, a request from the at least one receiver to receive the media stream; sending, by the MC server, a response to the at least one receiver to notify the receiving authorization permission; and incrementing, by the MC server, the counter value by 1 for each active receiver from the at least one receiver based on the authorized receiving.

[0272] In an embodiment of the disclosure, the method further comprises receiving, by the MC server, a request to terminate the media stream reception from the at least one receiver; sending, by the MC server, a response indicating the termination of the media stream reception; decrementing, by the MC server, the counter value by 1 for each termination of the media stream reception from the at least one receiver; determining, by the MC server, that the at least one receiver is not receiving the media stream based on the expiration of the timer; and entering, by the MC server, the "receiving idle" state based on the counter value.

[0273] In an embodiment of the disclosure, the method further comprises restarting, by the MC server, the timer for a predetermined duration when the counter value reaches a minimum predetermined value after each decrement of the counter value, or when the MC server sends the "media transmission notification" message to the MC device.

[0274] In an embodiment of the disclosure, the method further comprises terminating, by the MC server, the timer based on at least one of: a) if the at least one receiver accepts the notification to receive the media; or b) if the media transmission is ended by the transmission control server 102 by sending the transmission end notification message.

[0275] In an embodiment of the disclosure, wherein the MC server sends the transmission end request to the first sender to terminate the transmission after the expiration of the timer.

[0276] In an embodiment of the disclosure, wherein the first sender and the at least one receiver belong to the same group of MC devices, and wherein the media stream includes at least one of video and audio data.

[0277] According to another embodiment of the disclosure, a method of handling media transmission in a mission critical (MC) system is provided. A MC device receives a transmission end request from a MC server to terminate media stream transmission; a cause of terminating the media stream transmission is notified by the MC device to a user associated with the MC device, wherein the cause of terminating the transmission is due to lack of at least one receiver device for receiving the media stream; a transmission end response is sent by the MC device to the MC server; and the media stream transmission to the MC server is terminated by the MC device.

[0278] According to another embodiment of the disclosure, a method of handling media transmission in a mission critical (MC) system in a plurality of MC devices is provided. The method comprises: receiving, by a transmission participant device 100, a transmission end request from a transmission control server 102; notifying, by the transmission participant device 100, a user associated with the transmission participant device 100 that a media stream termination cause indicating authorization of a client to send media is revoked due to lack of at least one participant device to receive the media stream; sending, by the transmission participant device 100, a transmission end response to the transmission control server 102; and terminating, by the transmission participant device 100, the media stream transmission to the transmission control server 102.

[0279] In an embodiment of the disclosure, the method further comprises entering, by the transmission participant device 100, a "call release" state for a broadcast group call or a "not allowed to send" state for a normal or non-broadcast group call, wherein the transmission participant device 100 is a MC device 101 and is associated with a same group.

[0280] According to another embodiment of the disclosure, a method of handling media transmission in a mission critical (MC) system in a transmission control server 102 is provided. The method comprises: sending, by the transmission control server 102, a transmission end request message to a transmission MC device to terminate media stream when a timer (T11) defined as a stream reception idle timer expires; receiving, by the transmission control server 102, a transmission end response from a transmission participant device 100; and sending, by the transmission control server 102, a transmission end notification message to at least one media receiving client, wherein the transmission end notification message indicates a transmission end from the transmission participant device 100.

[0281] In an embodiment of the disclosure, the method further comprises: determining, by the transmission control server 102, whether there is any media transmission request in a queue; removing, by the transmission control server 102, the media transmission request from the queue; and authorizing, by the transmission control server 102, a permission to send the media stream to a second transmission participant device 100, wherein the transmission control server 102 enters a "pending transmission revocation" state after sending the transmission end request message to the transmission participant device 100.

[0282] In an embodiment of the disclosure, wherein after receiving the end of transmission response message from the transmission participant device 100, the transmission control server 102 in the basic transmission control operation state machine enters the 'transmission idle' state if the counter value (Cx) reaches the minimum limit during the simultaneous transmission of the media stream, or enters the 'transmission occupied' if the counter value (Cx) has not reached the minimum limit.

[0283] In an embodiment of the disclosure, wherein after receiving the end of transmission response message from the transmission participant device 100, the transmission control server 102 operating in the basic transmission control operation state machine stops the timer (T3) defined as the transmission cancellation timer and enters the 'U: not allowed and transmission idle' state.

[0284] In an embodiment of the disclosure, wherein the end of transmission request includes at least one of the 'no receiver participant' reason in the'reason for rejection' field of the end of transmission request to indicate the reason for terminating the media stream.

[0285] According to another embodiment of the disclosure, a method of handling media transmission in a mission critical (MC) system in a transmission control server 102 is provided. The method includes: authorizing, by the transmission control server 102, a first transmission participant device 100 to transmit a media stream to a plurality of MC devices 101; sending, by the transmission control server 102, a'media transmission notification' message to at least one MC device 101 to receive the media stream transmitted by the first transmission participant device 100; receiving, by the transmission control server 102, a'receive media request' message from at least one MC device 101 to receive the media stream from the first transmission participant device 100; sending, by the transmission control server 102, a'receive media response (authorization)' message to at least one MC device 101 to indicate authorization to receive the media stream from the first transmission participant device 100; receiving, by the transmission control server 102, a'media reception end request' message to terminate reception from at least one MC device 101; sending, by the transmission control server 102, a'media reception end response' to indicate a termination response of the media stream reception; determining, by the transmission control server 102, that at least one MC device 101 is not receiving the media stream based on the expiration of a predetermined duration of a timer T11; and entering, by the transmission control server 102, a'reception idle' state based on a counter (C11) value defined as a count of active receivers of the media stream.

[0286] In an embodiment of the disclosure, wherein the counter C11 value is initialized to 0, wherein the counter C11 is associated with a sender synchronization source (SSRC) or a user ID of the at least one MC device and a timer (T11) defined as a stream reception idle timer initiated with a duration of time after the transmission control server 102 sends a "media transmission notification" message to the at least one MC device 101.

[0287] In an embodiment of the disclosure, wherein the counter C11 value is incremented by 1 for each of the "receive media response (grant)" sent to the MC device 101 and decremented by 1 for each of the "media reception end request" or "media reception end response" message received from the MC device 101.

[0288] In an embodiment of the disclosure, wherein the timer (T11) is initiated with a duration of time based on at least one of: (a) the counter (C11) value reaching a minimum limit; or (b) after sending the media transmission notification message to the at least one MC device 101.

[0289] In an embodiment of the disclosure, wherein the timer (T11) is disabled by the transmission control server 102 based on at least one of: (a) the at least one MC device 101 being granted to receive the media stream from the transmission participant device 100 by sending a grant permission via the receive media request (grant) message; or (b) the media transmission being ended by the transmission control server 102 by sending a "transmission end notification" message to the at least one MC device 101.

[0290] In an embodiment of the disclosure, wherein the MC server sends an indication to terminate the transmission after the timer T11 expires.

[0291] According to another embodiment of the disclosure, there is provided an MC server for handling media transmission in a mission critical (MC) system. The MC server comprises one or more processors configured to: receive a request from a first sender to send a media stream to at least one receiver; send a notification to the at least one receiver to receive the media stream sent by the first sender; initiate a timer having a predetermined duration of time after sending the notification; determine that the at least one receiver rejects or does not accept the notification to receive the media stream within the predetermined duration of time of the timer; and send a transmission end request to the first sender to terminate the media stream transmission based on one of the rejection or the non-acceptance of the media stream reception.

[0292] According to another embodiment of the disclosure, a mission critical (MC) device for handling media transmission in a MC system is provided. The MC device includes one or more processors configured to: receive a transmission end request from a MC server to terminate a media stream transmission; notify a user associated with the MC device of a reason for terminating the media stream transmission, wherein the reason for terminating the transmission is due to a lack of at least one receiver device for receiving the media stream; send a transmission end response to the MC server; and terminate the media stream transmission to the MC server.

[0293] According to another embodiment of the disclosure, a transmission participant device for handling media transmission in a mission critical (MC) system in a plurality of MC devices 101 is provided. The transmission participant device includes one or more processors configured to: receive a transmission end request from a transmission control server 102; notify a user associated with the transmission participant device that a media stream termination cause indicating a client's authorization to send media is revoked due to a lack of at least one participant device to receive the media stream; send a transmission end response to the transmission control server 102; and terminate sending the media stream to the transmission control server 102.

[0294] According to another embodiment of the disclosure, a transmission control server for handling media transmission termination in a mission critical (MC) system is provided. The transmission control server includes one or more processors configured to: send a transmission end request message to a sending MC device to terminate a media stream transmission when a timer (T11) defined as a stream reception idle timer expires; receive a transmission end response from a transmission participant device 100; and send a transmission end notification message to at least one media receiving client, wherein the transmission end notification message indicates a transmission end from the transmission participant device 100.

[0295] According to another embodiment of the present application, there is provided a transport control server for handling media transport in a mission critical (MC) system. The transport control server comprises one or more processors configured to: authorize a first transport participant device 100 to send a media stream to a plurality of MC devices 101; send a "media transport notification" message to at least one MC device 101 to receive a media stream transmitted by the first transport participant device 100; receive a "receive media request" message from the at least one MC device 101 to receive the media stream from the first transport participant device 100; send a "receive media response (authorization)" message to the at least one MC device 101 to indicate authorization to receive the media stream from the first transport participant device 100; receive a "media reception end request" message to terminate reception from the at least one MC device 101; send a "media reception end response" to indicate a termination response of media stream reception; determine that the at least one MC device 101 has not received the media stream based on expiration of a predetermined duration of a timer T11; and enter a "receive idle" state based on a counter (C11) value defined as a count of active receivers of the media stream.

[0296] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The singular forms "a," "an," and "the" include plural referents unless otherwise stated.

[0297] While the subject matter has been described above in terms of particular aspects, it is not intended to be limited to the aspects described herein, which are intended only to be illustrative. The methods described herein can be modified in various ways, as will be apparent to persons skilled in the art. The drawings and the foregoing description give examples of embodiments. Those skilled in the art will appreciate that one or more of the elements can well be combined into a single functional element. Alternatively, certain elements can be split into multiple functional elements. Elements from one embodiment can be added to another embodiment.

Claims

1. A method executed by a mission-critical MC server in a mission-critical MC system, the method comprising: Receive a request message from the first MC device for sending a stream to at least one second MC device; In response to the request message, a notification message for receiving the stream sent by the first MC device is sent to the at least one second MC device, and a stream receive idle timer for the stream is started, wherein the stream receive idle timer is associated with the synchronization source SSRC or user identifier ID of the first MC device. The stream receive idle timer has expired; as well as Based on the identification, a request message for terminating the transmission of the stream is sent to the first MC device.

2. The method of claim 1, further comprising: Receive a request message for receiving the stream from the at least one second MC device; as well as If reception of the stream is authorized, the stream reception idle timer is stopped and the active receiver counter for the stream is incremented by 1. The counter is associated with the SSRC or user ID of the first MC device.

3. The method of claim 1, further comprising: Receive a request message or response message from the at least one second MC device to terminate the reception of the stream; If the active receiver counter used for the stream does not reach the lower limit, the counter value is reduced by 1; as well as If the counter has reached the lower limit value, the stream receive idle timer is started.

4. The method of claim 1, further comprising: Send a notification message to the at least one second MC device to terminate the stream and stop the stream receive idle timer.

5. The method of claim 1, further comprising: Receive a response message from the first MC device to terminate the transmission of the stream. The request message for terminating the transmission of the stream includes a rejection reason value, which indicates that the reason why the permission for the first MC device to send the stream is being revoked is that no participant is receiving the stream.

6. A method executed by a first mission-critical MC device in a mission-critical MC system, the method comprising: A request message is sent to the MC server for sending a stream to at least one second MC device. The request message triggers the start of a stream receive idle timer for the stream, wherein the stream receive idle timer is associated with the synchronization source SSRC or user identifier ID of the first MC device. If the first MC device is authorized to send the stream, the stream is sent to the at least one second MC device; If the stream receive idle timer has expired, a request message for terminating the stream transmission is received from the MC server. Send a response message to the MC server to terminate the transmission of the stream.

7. The method according to claim 6, wherein: When reception of the stream is authorized, the active receiver counter value for the stream is incremented, and the stream reception idle timer is stopped. If the counter has reached its lower limit, the stream receive idle timer will be started. The counter is associated with the SSRC or the user ID of the first MC device, and The request message for terminating the transmission of the stream includes a rejection reason value indicating that the reason the permission for the first MC device to send the stream is being revoked is that no participant is receiving the stream.

8. A mission-critical MC server in a mission-critical MC system, the MC server comprising: transceiver; as well as The controller is configured as follows: The transceiver receives a request message from the first MC device for sending a stream to at least one second MC device. In response to the request message, a notification message for receiving the stream sent by the first MC device is sent to the at least one second MC device via the transceiver, and a stream receive idle timer for the stream is started, wherein the stream receive idle timer is associated with the synchronization source SSRC or user identifier ID of the first MC device. The stream receive idle timer has expired; as well as Based on the identification, a request message for terminating the transmission of the stream is sent to the first MC device via the transceiver.

9. The MC server according to claim 8, wherein the controller is further configured to: The transceiver receives a request message for receiving the stream from the at least one second MC device. If reception of the stream is authorized, stop the stream reception idle timer and increment the active receiver counter for the stream by 1. in, The counter is associated with the SSRC or user ID of the first MC device.

10. The MC server according to claim 8, wherein the controller is further configured to: Receive a request message or response message for terminating the reception of the stream from the at least one second MC device via the transceiver; If the active receiver counter value used for the stream does not reach the lower limit, the counter is decremented by 1; and If the counter has reached the lower limit value, the stream receive idle timer is started.

11. The MC server according to claim 8, wherein the controller is further configured to: Sending a notification message to the at least one second MC device via the transceiver to terminate the transmission of the stream, and Stop the stream receive idle timer.

12. The MC server according to claim 8, wherein the controller is further configured to: The transceiver receives a response message from the first MC device to terminate the transmission of the stream.

13. The MC server according to claim 8, in, The request message for terminating the transmission of the stream includes a rejection reason value indicating that the reason the permission for the first MC device to send the stream is being revoked is that no participant is receiving the stream.

14. A first mission-critical MC device in a mission-critical MC system, the first MC device comprising: transceiver; as well as The controller is configured as follows: The transceiver sends a request message to the MC server for sending a stream to at least one second MC device. This request message triggers the start of a stream receive idle timer for the stream, wherein the stream receive idle timer is associated with the synchronization source SSRC or user identifier ID of the first MC device. If the first MC device is authorized to send the stream, the stream is sent to the at least one second MC device via the transceiver. If the stream receive idle timer expires, a request message for terminating the stream transmission is received from the MC server via the transceiver. The transceiver sends a response message to the MC server to terminate the transmission of the stream.

15. The first MC device according to claim 14, wherein: When the reception of the stream is authorized, the active receiver counter for the stream is incremented, and the stream reception idle timer is stopped. If the counter has reached its lower limit, the stream receive idle timer will be started. The counter is associated with the SSRC or the user ID of the first MC device, and The request message for terminating the transmission of the stream includes a rejection reason value indicating that the reason the permission for the first MC device to send the stream is being revoked is that no participant is receiving the stream.

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