Ad HOC group call setup for migrated mission critical service users in interconnected MC system

Abstract

The disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate. Embodiments of the present invention relate to a method and system for managing an ad hoc group call in a mission-critical (MC) communication system. The method for managing an ad hoc group call in an MC communication system comprises a primary MC system (10) and a secondary MC system (30). A first MC service server (25) in the primary MC system (10) receives an ad hoc group call initiation request from a first MC service client (15) including MC service identifiers of target users. The first MC service server (25) invites a second MC service client (20) by forwarding the request using a service ID assigned by the secondary MC system (30). Upon detecting that a third user has migrated to the secondary MC system (30), the first MC service server (25) transmits a redirection notification to the first MC service client (15) including both the old and new MC service IDs and the migration reason. The first MC service server (25) sends an ad hoc group call response indicating success or failure with details, and the ad hoc group call is established across the included MC systems (10, 30, 50).

Description

AD HOC GROUP CALL SETUP FOR MIGRATED MISSION CRITICAL SERVICE USERS IN INTERCONNECTED MC SYSTEM

[0001] The present invention pertains to the field of wireless communication. More specifically, it relates to methods and systems for the setup of ad hoc group calls for a migrated Mission Critical (MC) service user.

[0002] 5G mobile communication technologies define broad frequency bands such that high transmission rates and new services are possible, and can be implemented not only in "Sub 6GHz" bands such as 3.5GHz, but also in "Above 6GHz" bands referred to as mmWave including 28GHz and 39GHz. In addition, it has been considered to implement 6G mobile communication technologies (referred to as Beyond 5G systems) in terahertz bands (for example, 95GHz to 3THz bands) in order to accomplish transmission rates fifty times faster than 5G mobile communication technologies and ultra-low latencies one-tenth of 5G mobile communication technologies.

[0003] At the beginning of the development of 5G mobile communication technologies, in order to support services and to satisfy performance requirements in connection with enhanced Mobile BroadBand (eMBB), Ultra Reliable Low Latency Communications (URLLC), and massive Machine-Type Communications (mMTC), there has been ongoing standardization regarding beamforming and massive MIMO for mitigating radio-wave path loss and increasing radio-wave transmission distances in mmWave, supporting numerologies (for example, operating multiple subcarrier spacings) for efficiently utilizing mmWave resources and dynamic operation of slot formats, initial access technologies for supporting multi-beam transmission and broadbands, definition and operation of BWP (BandWidth Part), new channel coding methods such as a LDPC (Low Density Parity Check) code for large amount of data transmission and a polar code for highly reliable transmission of control information, L2 pre-processing, and network slicing for providing a dedicated network specialized to a specific service.

[0004] Currently, there are ongoing discussions regarding improvement and performance enhancement of initial 5G mobile communication technologies in view of services to be supported by 5G mobile communication technologies, and there has been physical layer standardization regarding technologies such as V2X (Vehicle-to-everything) for aiding driving determination by autonomous vehicles based on information regarding positions and states of vehicles transmitted by the vehicles and for enhancing user convenience, NR-U (New Radio Unlicensed) aimed at system operations conforming to various regulation-related requirements in unlicensed bands, NR UE Power Saving, Non-Terrestrial Network (NTN) which is UE-satellite direct communication for providing coverage in an area in which communication with terrestrial networks is unavailable, and positioning.

[0005] Moreover, there has been ongoing standardization in air interface architecture / protocol regarding technologies such as Industrial Internet of Things (IIoT) for supporting new services through interworking and convergence with other industries, IAB (Integrated Access and Backhaul) for providing a node for network service area expansion by supporting a wireless backhaul link and an access link in an integrated manner, mobility enhancement including conditional handover and DAPS (Dual Active Protocol Stack) handover, and two-step random access for simplifying random access procedures (2-step RACH for NR). There also has been ongoing standardization in system architecture / service regarding a 5G baseline architecture (for example, service based architecture or service based interface) for combining Network Functions Virtualization (NFV) and Software-Defined Networking (SDN) technologies, and Mobile Edge Computing (MEC) for receiving services based on UE positions.

[0006] As 5G mobile communication systems are commercialized, connected devices that have been exponentially increasing will be connected to communication networks, and it is accordingly expected that enhanced functions and performances of 5G mobile communication systems and integrated operations of connected devices will be necessary. To this end, new research is scheduled in connection with eXtended Reality (XR) for efficiently supporting AR (Augmented Reality), VR (Virtual Reality), MR (Mixed Reality) and the like, 5G performance improvement and complexity reduction by utilizing Artificial Intelligence (AI) and Machine Learning (ML), AI service support, metaverse service support, and drone communication.

[0007] Furthermore, such development of 5G mobile communication systems will serve as a basis for developing not only new waveforms for providing coverage in terahertz bands of 6G mobile communication technologies, multi-antenna transmission technologies such as Full Dimensional MIMO (FD-MIMO), array antennas and large-scale antennas, metamaterial-based lenses and antennas for improving coverage of terahertz band signals, high-dimensional space multiplexing technology using OAM (Orbital Angular Momentum), and RIS (Reconfigurable Intelligent Surface), but also full-duplex technology for increasing frequency efficiency of 6G mobile communication technologies and improving system networks, AI-based communication technology for implementing system optimization by utilizing satellites and AI (Artificial Intelligence) from the design stage and internalizing end-to-end AI support functions, and next-generation distributed computing technology for implementing services at levels of complexity exceeding the limit of UE operation capability by utilizing ultra-high-performance communication and computing resources.

[0008] The present invention has been made to address at least the above problems and / or disadvantages and to provide at least the advantages described below. Accordingly, an aspect of the present invention provides a method and apparatus for ad hoc group call setup towards a migrated MC service user.

[0009] In an aspect, the objects are achieved by providing a method for managing an ad hoc group call in a mission-critical (MC) communication system that includes a primary MC system and a secondary MC system. The method includes receiving by a first MC service server in the primary MC system an ad hoc group call initiation request from a first MC service client associated with a first MC service user. The ad hoc group call initiation request comprises MC service identifiers of a plurality of target MC service users.

[0010] Further, the method includes inviting by the first MC service server of the primary MC system a second MC service client to join the ad hoc group call by sending the ad hoc group call initiation request using the MC service ID assigned by the secondary MC system and establishing the ad hoc group call with the second MC service client.

[0011] Furthermore, the method includes determining by the first MC service server that a third MC service user has migrated to the secondary MC system with a new MC service ID assigned by the secondary MC system. The method further includes transmitting by the first MC service server an ad hoc group call redirection notification to the first MC service client informing the first MC service client that the ad hoc group call request towards the third MC service user is redirected to the secondary MC system.

[0012] The ad hoc group call redirection notification comprises information about the MC service ID of the third MC service user assigned by both the primary MC system and the secondary MC system and a reason for the call redirection being user migration.

[0013] Furthermore, the method includes transmitting by the first MC service server an ad hoc group call response to the first MC service client upon receiving responses to the corresponding ad hoc group call request. The ad hoc group call response includes the success or failure result along with detailed reason information in case of failure and establishes the ad hoc group call among multiple group members from at least one of the primary MC system, the secondary MC system, and a tertiary MC system.

[0014] Furthermore, the method includes transmitting by the first MC service server an ad hoc group call response to the first MC service client upon receiving responses to the corresponding ad hoc group call request, wherein the ad hoc group call response includes the success or failure result and detailed reason information in case of failure. The method further includes establishing the ad hoc group call among multiple group members from at least one of the primary MC system, the secondary MC system, and a tertiary MC system.

[0015] In an aspect, the objects are achieved by providing a first Mission Critical (MC) System for managing ad hoc group call setup in a communication environment comprising multiple interconnected MC systems. The first MC system comprises a memory including information about a second and third MC system, a processor, and an MC-Migration Service (MC-MS) controller, the MC-MS controller being coupled to both the memory and the processor.

[0016] Upon receiving an ad hoc group call initiation request from a first MC service client associated with a first MC service user, the MC-MS controller via a first MC service server in the primary MC system processes the request, wherein the request includes MC service identifiers of a plurality of target MC service users.

[0017] The MC-MS controller then invites a second MC service client to join the ad hoc group call by sending the ad hoc group call initiation request using the MC service identifier assigned by a secondary MC system and establishes the ad hoc group call with the second MC service client.

[0018] Furthermore, the MC-MS controller determines that a third MC service user has migrated to the secondary MC system with a new MC service identifier assigned by the secondary MC system.

[0019] Upon such determination, the MC-MS controller transmits an ad hoc group call redirection notification to the first MC service client informing that the ad hoc group call request toward the third MC service user is redirected to the secondary MC system. The redirection notification includes the MC service identifiers assigned by both the primary and secondary MC systems for the third MC service user along with a reason for the call redirection, namely user migration.

[0020] Furthermore, the MC-MS controller transmits an ad hoc group call response to the first MC service client upon receiving responses to the ad hoc group call request. The ad hoc group call response includes a success or failure result and, in case of failure, detailed reason information.

[0021] Furthermore, the MC-MS controller establishes the ad hoc group call among multiple group members from at least one of the primary MC system, the secondary MC system, and a tertiary MC system.

[0022] In an aspect, the objects are achieved by providing a first MC System for an ad hoc group call setup by a first mission-critical (MC) system in a communication environment comprising multiple interconnected MC systems. The first MC System comprises a memory including information about a second and third MC system, a processor, and an MC-Migration Service (MC-MS) controller. The MC-MS controller is coupled to both the memory and the processor.

[0023] Upon receiving an ad hoc group call initiation request from a first MC service client associated with a first MC service user, the MC-MS controller via a first MC service server in the primary MC system processes the request, wherein the request includes MC service identifiers of a plurality of target MC service users. The MC-MS controller invites a second MC service client to join the ad hoc group call by sending the ad hoc group call initiation request using the MC service identifier assigned by a secondary MC system and establishes the ad hoc group call with the second MC service client. Further, the MC-MS controller determines that a third MC service user has migrated to the secondary MC system with a new MC service identifier assigned by the secondary MC system.

[0024] Upon such determination, the MC-MS controller transmits an ad hoc group call redirection notification to the first MC service client informing that the ad hoc group call request towards the third MC service user is redirected to the secondary MC system. The redirection notification includes the MC service identifiers assigned by both the primary and secondary MC systems for the third MC service user along with a reason for the call redirection, namely user migration. Further, the MC-MS controller transmits an ad hoc group call response to the first MC service client upon receiving responses to the ad hoc group call request. The ad hoc group call response includes a success or failure result and, in case of failure, detailed reason information. Furthermore, the MC-MS controller establishes the ad hoc group call among multiple group members from at least one of the primary MC system, the secondary MC system, and a tertiary MC system.

[0025] The aspects of an embodiment ass will be better appreciated and understood with the following description and accompanying drawings. While the descriptions indicate preferred embodiments and specific details, they are provided for illustration, not limitation. Numerous changes and modifications can be made within the scope of an embodiment ass, which include all such modifications.

[0026] Advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention. For more enhanced communication system, there is a need for method and network for ad hoc group call setup towards a migrated MC service user.

[0027] The invention is illustrated in the accompanying drawings, where like reference letters indicate corresponding parts. An embodiment ass will be better understood from the following description with reference to the drawings.

[0028] FIG. 1 is a block diagram of a primary mission-critical MC system (MC System A) for ad hoc group call setup in a communication environment comprising multiple interconnected MC systems according to embodiments as disclosed herein.

[0029] FIG. 2 is a block diagram of a secondary mission-critical MC system (MC System B) for ad hoc group call setup in a communication environment comprising multiple interconnected MC systems according to embodiments as disclosed herein.

[0030] FIG. 3 is a sequence diagram that illustrates a scenario of ad hoc group call towards migrated MC service users according to an embodiment as disclosed herein.

[0031] FIG. 4 is a sequence diagram that illustrates an alternate solution for ad hoc group call towards migrated MC service users according to an embodiment as disclosed herein.

[0032] FIG. 5A is a flow chart that illustrates a method for managing an ad hoc group call in an MC communication system comprising a primary MC system and secondary MC system according to an embodiment as disclosed herein.

[0033] FIG. 5B is a flow chart that illustrates a method for managing an ad hoc group call in an MC communication system first MC service server to establish an ad hoc group call involving clients across multiple MC systems according to an embodiment as disclosed herein.

[0034] The advent of Mission Critical (MC) communication systems has revolutionized the way emergency services, military operations, and other critical communication networks operate. These systems enable robust, reliable, and secure communication among users, facilitating coordination and information sharing in real-time. One of the key functionalities of MC system is the ability to initiate ad hoc group calls, which allow multiple users to participate in a call without prior setup, thereby enhancing responsiveness during critical situations.

[0035] Typically, an ad hoc group call is initiated by a user (the initiator) using the participant list that includes the MC service IDs of the MC service users. The call is hosted on the MC service server of the initiator's primary MC system. However, complications arise when one or more of the requested participants have been migrated to a partner MC system (migrated MC system). Migration can occur due to various reasons, such as load balancing, network optimization, or user mobility.

[0036] When a participant is migrated to a partner MC system, they are assigned a new MC service ID by the partner MC system. The initiator, unaware of the migration, continues to use the MC service ID assigned by the primary MC system. Consequently, the ad hoc group call must be redirected to the partner MC system using the new MC service ID assigned by the migrated MC system. The primary MC system of the migrated user is aware of the migration and assists in redirecting the call.

[0037] Further, complications increase when participants are migrated between interconnected partner MC system. In such scenarios, the primary MC system of the migrated user must provide the new MC service ID assigned by another partner MC system to the MC system hosting the ad hoc group call. This hosting MC service server further delivers the call to the migrated user using the new MC service ID.

[0038] Despite the mechanisms in place, the current methods do not provide a seamless way to establish ad hoc group calls with migrated MC service users using their new MC service IDs assigned by the partner MC system. This results in several issues, including:

[0039] 1. Communication Delays: Inefficiencies in redirecting calls can lead to significant delays, which are detrimental in mission-critical scenarios where timely communication is paramount.

[0040] 2. Complex Call Routing: The process of redirecting calls through multiple MC system complicates call routing, increasing the likelihood of errors and call failures.

[0041] 3. User Confusion: Users may experience confusion due to the changes in their MC service IDs, leading to difficulties in initiating or participating in ad hoc group calls.

[0042] 4. System Overhead: The need for continuous updates and coordination between primary and partner MC system adds to the system overhead, impacting overall performance and reliability.

[0043] Thus, it is desired to address the above-mentioned disadvantages, issues, or other shortcomings or at least provide a useful alternative.

[0044] The principal object of the invention herein is to provide methods and systems for ad hoc group call setup towards a migrated MC service user.

[0045] Another object of the invention herein is to provide a procedure to support ad hoc group calls towards migrated MC service users.

[0046] Yet another object of the invention herein is a method for managing an ad hoc group call in an MC communication system.

[0047] Yet another object of the invention herein is to provide a system for ad hoc group call setup by a first MC system in a communication environment comprising multiple interconnected MC systems.

[0048] In an aspect, the objects are achieved by providing a method for managing an ad hoc group call in a mission-critical (MC) communication system that includes a primary MC system and a secondary MC system. The method includes receiving by a first MC service server in the primary MC system an ad hoc group call initiation request from a first MC service client associated with a first MC service user. The ad hoc group call initiation request comprises MC service identifiers of a plurality of target MC service users.

[0049] Further, the method includes inviting by the first MC service server of the primary MC system a second MC service client to join the ad hoc group call by sending the ad hoc group call initiation request using the MC service ID assigned by the secondary MC system and establishing the ad hoc group call with the second MC service client.

[0050] Furthermore, the method includes determining by the first MC service server that a third MC service user has migrated to the secondary MC system with a new MC service ID assigned by the secondary MC system. The method further includes transmitting by the first MC service server an ad hoc group call redirection notification to the first MC service client informing the first MC service client that the ad hoc group call request towards the third MC service user is redirected to the secondary MC system.

[0051] The ad hoc group call redirection notification comprises information about the MC service ID of the third MC service user assigned by both the primary MC system and the secondary MC system and a reason for the call redirection being user migration.

[0052] Furthermore, the method includes transmitting by the first MC service server an ad hoc group call response to the first MC service client upon receiving responses to the corresponding ad hoc group call request. The ad hoc group call response includes the success or failure result along with detailed reason information in case of failure and establishes the ad hoc group call among multiple group members from at least one of the primary MC system, the secondary MC system, and a tertiary MC system.

[0053] Furthermore, the method includes transmitting by the first MC service server an ad hoc group call response to the first MC service client upon receiving responses to the corresponding ad hoc group call request, wherein the ad hoc group call response includes the success or failure result and detailed reason information in case of failure. The method further includes establishing the ad hoc group call among multiple group members from at least one of the primary MC system, the secondary MC system, and a tertiary MC system.

[0054] In an aspect, the objects are achieved by providing a first Mission Critical (MC) System for managing ad hoc group call setup in a communication environment comprising multiple interconnected MC systems. The first MC system comprises a memory including information about a second and third MC system, a processor, and an MC-Migration Service (MC-MS) controller, the MC-MS controller being coupled to both the memory and the processor.

[0055] Upon receiving an ad hoc group call initiation request from a first MC service client associated with a first MC service user, the MC-MS controller via a first MC service server in the primary MC system processes the request, wherein the request includes MC service identifiers of a plurality of target MC service users.

[0056] The MC-MS controller then invites a second MC service client to join the ad hoc group call by sending the ad hoc group call initiation request using the MC service identifier assigned by a secondary MC system and establishes the ad hoc group call with the second MC service client.

[0057] Furthermore, the MC-MS controller determines that a third MC service user has migrated to the secondary MC system with a new MC service identifier assigned by the secondary MC system.

[0058] Upon such determination, the MC-MS controller transmits an ad hoc group call redirection notification to the first MC service client informing that the ad hoc group call request toward the third MC service user is redirected to the secondary MC system. The redirection notification includes the MC service identifiers assigned by both the primary and secondary MC systems for the third MC service user along with a reason for the call redirection, namely user migration.

[0059] Furthermore, the MC-MS controller transmits an ad hoc group call response to the first MC service client upon receiving responses to the ad hoc group call request. The ad hoc group call response includes a success or failure result and, in case of failure, detailed reason information.

[0060] Furthermore, the MC-MS controller establishes the ad hoc group call among multiple group members from at least one of the primary MC system, the secondary MC system, and a tertiary MC system.

[0061] In an aspect, the objects are achieved by providing a first MC System for an ad hoc group call setup by a first mission-critical (MC) system in a communication environment comprising multiple interconnected MC systems. The first MC System comprises a memory including information about a second and third MC system, a processor, and an MC-Migration Service (MC-MS) controller. The MC-MS controller is coupled to both the memory and the processor.

[0062] Upon receiving an ad hoc group call initiation request from a first MC service client associated with a first MC service user, the MC-MS controller via a first MC service server in the primary MC system processes the request, wherein the request includes MC service identifiers of a plurality of target MC service users. The MC-MS controller invites a second MC service client to join the ad hoc group call by sending the ad hoc group call initiation request using the MC service identifier assigned by a secondary MC system and establishes the ad hoc group call with the second MC service client. Further, the MC-MS controller determines that a third MC service user has migrated to the secondary MC system with a new MC service identifier assigned by the secondary MC system.

[0063] Upon such determination, the MC-MS controller transmits an ad hoc group call redirection notification to the first MC service client informing that the ad hoc group call request towards the third MC service user is redirected to the secondary MC system. The redirection notification includes the MC service identifiers assigned by both the primary and secondary MC systems for the third MC service user along with a reason for the call redirection, namely user migration. Further, the MC-MS controller transmits an ad hoc group call response to the first MC service client upon receiving responses to the ad hoc group call request. The ad hoc group call response includes a success or failure result and, in case of failure, detailed reason information. Furthermore, the MC-MS controller establishes the ad hoc group call among multiple group members from at least one of the primary MC system, the secondary MC system, and a tertiary MC system.

[0064] The aspects of an embodiment ass will be better appreciated and understood with the following description and accompanying drawings. While the descriptions indicate preferred embodiments and specific details, they are provided for illustration, not limitation. Numerous changes and modifications can be made within the scope of an embodiment ass, which include all such modifications.

[0065] The embodiments and their features are detailed with reference to non-limiting examples shown in the drawings and described below. Well-known components and techniques are omitted for brevity. The described embodiments can be combined to form new ones. The term "or" is used non-exclusively unless stated otherwise. Examples provided are illustrative and not limiting.

[0066] Embodiments can be described and illustrated as blocks performing specific functions. These blocks, referred to as managers, units, modules, hardware components, etc., are implemented by analog and / or digital circuits such as logic gates, integrated circuits, microprocessors, microcontrollers, memory circuits, passive and active electronic components, optical components, hardwired circuits, etc., and may be driven by firmware and software. These circuits may be embodied in semiconductor chips or on substrates like printed circuit boards. Blocks can be implemented by dedicated hardware, processors, or a combination of both. Each block can be divided into multiple interacting blocks or combined into more complex blocks without departing from the scope of the disclosure.

[0067] The accompanying drawings aid in understanding the technical features but do not limit the embodiments. The disclosure includes any alterations, equivalents, and substitutes beyond those shown. Terms like first, second, third, etc., are used for distinction and do not limit the elements.

[0068] The proposed invention provides a method and system for managing an ad hoc group call in a mission-critical (MC) communication system comprising a primary MC system and at least one partner MC system. When a user migrates to another MC service system, they are assigned an MC service ID from the migrated system. Users in the migrated user's home system continue to use the MC service ID assigned by the primary system. If a user in the primary system initiates an ad hoc group call to a migrated user, they will use the MC service ID known to their client, which is assigned by the primary system. Consequently, the ad hoc group call will not be delivered to the migrated user.

[0069] This invention addresses this issue by providing a method for establishing an ad hoc group call with migrated MC service users from a partner MC system (migrated MC system), including the MC service user from the primary MC system. The ad hoc group call setup is initiated with the primary system-assigned MC service ID of the targeted MC service user. Without this solution, establishing an ad hoc group call with migrated MC service users in the partner MC system is not possible. The invention enables the establishment of ad hoc group calls with migrated MC service users using the MC service ID assigned by the primary MC system and routing the call to the migrated MC system using the MC service ID assigned by the migrated MC system.

[0070] An ad hoc group call can be initiated using the participant list (MC service IDs of the MC service users) provided by the initiator of the ad hoc group call. Any requested participant MC service user may have migrated to a partner MC system and been assigned a new MC service ID from the partner MC system. The initiator of the call, unaware of the migration, still uses the MC service ID assigned by the primary MC system of the migrated MC service user. If any requested participant MC service user has migrated to a partner MC system, the ad hoc group call should be delivered to the partner MC system to which the MC service user has migrated. The primary MC system of the migrated MC service user is aware of the migration and assists in redirecting the ad hoc group call to the partner MC system using the partner MC system-assigned MC service ID.

[0071] If one of the requested participants is from an interconnected MC system and has migrated to another partner system, the call should be delivered to the partner MC system to which the participant has migrated. The primary MC system of the migrated MC service user assists in redirecting the ad hoc group call setup request by providing the partner MC system-assigned MC service ID to the MC system where the ad hoc group call is hosted (focus MC service server of the caller's primary MC system). The primary MC system of the migrated MC service user receives the ad hoc group call setup request using the primary MC system-assigned MC service ID when the initiator of the call is unaware of the migration. The ad hoc group call hosting MC service server of the MC system further delivers the call to the migrated MC service user using the partner MC system-assigned MC service ID.

[0072] Existing systems, as described in 3GPP specifications, lack a method for establishing an ad hoc group call with a migrated MC service user using the MC service ID assigned by the primary MC system and routing it to the migrated MC system using the MC service ID assigned by the migrated MC system. In contrast, the proposed solution provides a method for establishing such ad hoc group calls.

[0073] The invention relates to the field of mission-critical services used by public safety communities (such as police, military, fire services, ambulance crews, and others) in operations requiring high reliability, speed, quick accessibility, and low latency operational support. Such operations necessitate communication among users from different MC systems and migrated MC systems. This invention specifically relates to providing a method for setting up ad hoc group calls towards migrated MC service users.

[0074] Referring now to the drawings, and more particularly to FIGS. 1 through 5, there are shown preferred embodiments.

[0075] FIG. 1 is a block diagram of a primary mission-critical (MC) system (MC System A) for ad hoc group call setup in a communication environment comprising multiple interconnected MC systems. In an embodiment, the primary MC System (10) includes a processor (26), a memory (27), a communicator (28), and an MC-Migration Service (MC-MS) controller (29). The processor (26) is coupled with the memory (27), the communicator (28), and the MC-MS controller (29).

[0076] The processor (28) manages an ad hoc group call in an MC communication system. It communicates with the memory (27), the communicator (28), and the MC-MS controller (29). Configured to execute instructions stored in the memory (27), the processor (26) may include one or more processors, such as a Central Processing Unit (CPU), Application Processor (AP), Graphics Processing Unit (GPU), Visual Processing Unit (VPU), or Neural Processing Unit (NPU).

[0077] The memory (27) stores the operating system, application software, and temporary data for the processor (26). It includes instructions for the processor (26) and includes non-volatile storage elements such as magnetic hard disks, optical disks, floppy disks, flash memories, EPROM, or EEPROM. The memory (27) can be considered a non-transitory storage medium, meaning it is not a carrier wave or propagated signal, but it is still movable. Further, the memory (27) holds second and third MC system information, including service identifier updates for migrated users, metadata identifying the source and destination MC system of the migrated user, and floor control and media plane setup for all MC service clients across the interconnected MC system. This information helps the MC system efficiently manage ad hoc group calls, ensuring seamless connectivity and robust communication within the network.

[0078] The communicator (28) enables communication between the processor (26) and memory (27), supporting protocols like TCP / IP, UDP, TLS, IPSec, and HTTPS. It is also configured for internal communication between hardware components, featuring an electronic circuit for wired or wireless message transmission.

[0079] The MC-MS controller (29) is specialized hardware for managing ad hoc group calls in an MC communication system. Its innovative integrated circuit can for example includes a multi-core architecture, with each core optimized for specific tasks such as group call initiation, ad hoc group call responses, data storage, and call management. The circuit combines analog components, including a low-noise amplifier, and digital components, such as a microcontroller unit (MCU) and a digital signal processor (DSP). These components work together to introduce a new attribute related to the storage format used by the first MC system (10).

[0080] The MC-MS controller (29) receives an ad hoc group call initiation request from a first MC service client associated with a first MC service user via a first MC service server in the primary MC system (10). This request includes MC service identifiers of multiple target MC service users. The request is processed by the MC-MS controller (29) to verify the validity of the MC service identifiers and ensure that the target users are available for the group call. The MC-MS controller (29) utilizes a database to cross-reference the MC service identifiers with user profiles and their current status within the network. Further, the MC-MS controller (29) checks for any restrictions or permissions associated with the target users to ensure compliance with system policies.

[0081] An invitation to join the ad hoc group call is extended by the MC-MS controller (29) through the first MC service server of the primary MC system (10) to a second MC service client. The ad hoc group call initiation request is sent using the MC service ID assigned by the secondary MC system (30), thereby establishing the ad hoc group call with the second MC service client. The invitation includes metadata such as the call type, priority level, and encryption parameters to ensure secure communication. The MC-MS controller (29) also manages the synchronization of call settings between the primary and secondary MC systems to maintain consistency in the user experience. Furthermore, the MC-MS controller (29) monitors the network for any potential issues that could affect the call quality and implements corrective measures as needed.

[0082] The MC-MS controller (29) determines that a third MC service user has migrated to the secondary MC system (30) and has been assigned a new MC service ID by the secondary MC system (30). The MC-MS controller (29) updates its internal records to reflect the new MC service ID and ensures that all future communications involving the third MC service user are routed through the secondary MC system (30). The migration process includes authentication and validation steps to confirm the identity of the third MC service user and prevent unauthorized access.

[0083] A notification of ad hoc group call redirection is transmitted by the MC-MS controller (29) through the first MC service server to the first MC service client. This notification informs the first MC service client that the ad hoc group call request directed towards the third MC service user has been redirected to the secondary MC system (30). The notification includes information about the MC service ID of the third MC service user assigned by both the primary MC system (10) and the secondary MC system (30) along with the reason for the call redirection being user migration. In an example, the notification can provide details on the expected impact on call quality and any changes in call handling procedures due to the redirection.

[0084] Upon receiving responses to the corresponding ad hoc group call request, the MC-MS controller (29) transmits an ad hoc group call response to the first MC service client via the first MC service server. This response includes the success or failure result and detailed reason information in case of failure. The ad hoc group call is then established among multiple group members from at least one of the primary MC system (10), the secondary MC system (30), and a tertiary MC system. The MC-MS controller (29) dynamically allocates network resources to optimize the call experience and ensures that all participants are connected with minimal disruptions. Further, the MC-MS controller (104) logs the call details for future reference and analysis to improve system performance and user satisfaction.

[0085] FIG 2 is a block diagram of a secondary mission-critical (MC) system (MC System B) (30) for ad hoc group call setup in a communication environment with multiple interconnected MC systems. The second MC System (30) includes a processor (41), memory (42), communicator (43), and MC-Migration Service (MC-MS) controller (44). The processor (41) manages ad hoc group calls, communicating with the memory (42), communicator (43), and MC-MS controller (44). It can be a general-purpose processor (CPU, AP), graphics processor (GPU, VPU), or AI processor (NPU).

[0086] The memory (42) stores the operating system, application software, temporary data, and instructions for the processor (41). It includes non-volatile storage elements like hard disks, optical disks, flash memories, EPROM, and EEPROM. The memory (42) holds MC system information, service identifier updates, metadata, and setup details for MC service clients, ensuring efficient ad hoc group call management and robust communication.

[0087] The communicator (43) facilitates communication between the processor (41) and memory (42), supporting protocols like TCP / IP, UDP, TLS, IPSec, HTTPS, and internal hardware communication. It includes an electronic circuit for wired or wireless communication, enabling message transmission.

[0088] Specialized hardware designed for managing an ad hoc group call in the MC communication system is the MC-MS controller (44). In an embodiment, the structure of such an innovative integrated circuit of the MC-MS controller (44) can include a multi-core architecture that enables the management of an ad hoc group call in an MC communication system. Each core is optimized for specific tasks such as group call initiation requests, ad hoc group call responses with the MC service clients, storing data of 1st and 3rd MC system data size, and performing the management of an ad hoc group call in an MC communication system. The integrated circuit of the MC-MS controller (44) is made of a combination of analog and digital components designed to enable managing an ad hoc group call in an MC communication system. Analog components include a low-noise amplifier. Digital components include a microcontroller unit (MCU) and a digital signal processor (DSP) that work in tandem to introduce one new attribute that includes information related to the storage format to be used by the secondary MC system (30).

[0089] The MC-MS controller (44) determines that the fourth MC service user has migrated to the tertiary MC system, with a new MC service ID assigned by the tertiary MC system. An ad hoc group call redirection notification is transmitted by the MC-MS controller (44) to the first MC service server (25), informing the first MC service server (25) that the ad hoc group call initiation towards the fourth MC service user has migrated and is assigned a new MC service ID by the tertiary MC system. This notification comprises information about the MC service ID of the fourth MC service user assigned by both the secondary MC system (30) and the tertiary MC system, and the reason for the call redirection being user migration.

[0090] In an embodiment, the method for managing an ad hoc group call in a mission-critical (MC) communication system, which includes a primary Mission Critical (MC) system (10) and a secondary MC system (30), includes receiving an ad hoc group call initiation request by the first MC service server (25) in the primary MC system (10) from a first MC service client (15) associated with a first MC service user. The ad hoc group call initiation request comprises MC service identifiers of a plurality of target MC service users. The first MC service server (25) of the primary MC system (10) invites a second MC service client (20) to join the ad hoc group call by sending the ad hoc group call initiation request using the MC service ID assigned by the secondary MC system (30) and establishes the ad hoc group call with the second MC service client (20).

[0091] In another embodiment, the first MC service server determines that the third MC service user has migrated to the secondary MC system (30) with a new MC service ID assigned by the secondary MC system (30). The first MC service server transmits an ad hoc group call redirection notification to the first MC service client (15), informing the first MC service client (15) that the ad hoc group call request towards the third MC service user is redirected to the secondary MC system (30). This notification includes information about the MC service ID of the third MC service user assigned by both the primary MC system (10) and the secondary MC system (30), and the reason for the call redirection being user migration. Upon receiving responses to the corresponding ad hoc group call request, the first MC service server transmits an ad hoc group call response to the first MC service client (15). This response includes the success or failure result and detailed reason information in case of failure, and establishes the ad hoc group call among multiple group members from at least one of the primary MC system (10), the secondary MC system (30), and a tertiary MC system.

[0092] FIG 3 is a sequence diagram illustrating a scenario of an ad hoc group call towards migrated MC service users. The MC service user, unaware of the migration of the target MC service user, initiates an ad hoc group call using the MC service ID assigned by the primary MC system of the targeted MC service users. This ad hoc group call is hosted in the primary MC system of the initiator. The targeted MC service users belong to both the primary MC system and the partner MC system.

[0093] When any of the targeted MC service users belonging to the primary MC system have migrated to the partner MC system, they are assigned a new MC service ID from the partner MC system. The primary MC system of the migrated MC service user knows the MC service IDs from both the primary MC system and the partner MC system. Upon receiving an ad hoc group call request for a migrated MC service user at the primary MC system, the request is attempted to be redirected to the migrated MC service user using the newly assigned MC service ID in the partner MC system. The initiator of the ad hoc group call is informed of this redirection, along with the MC service IDs from both systems and the reason for the redirection, which is migration.

[0094] Similarly, when any of the targeted MC service users belonging to the partner MC system have migrated to another partner MC system (i.e., migrated MC system), they are assigned a new MC service ID from the other partner MC system. The partner MC system becomes the primary MC system of the migrated MC service user. The primary MC system of the migrated MC service user knows the MC service IDs from both the primary MC system and the other partner MC system. Upon receiving an ad hoc group call request for a migrated MC service user at the primary MC system of the migrated MC service user, the primary MC system assists in redirecting the ad hoc group call setup request by providing the MC service ID assigned by the other partner MC system to the MC system where the ad hoc group call is hosted (focus MC service server of the caller's primary MC system). The ad hoc group call hosting MC service server further delivers the call to the migrated MC service user using the MC service ID assigned by the other partner MC system. The initiator of the ad hoc group call is informed of this redirection, along with the MC service IDs from both systems and the reason for the redirection, which is migration.

[0095] In an alternate solution, when an ad hoc group call request for a migrated MC service user is received at the primary MC system of the migrated MC service user, the primary MC system attempts the ad hoc group call request to the migrated MC service user using the newly assigned MC service ID in the partner MC system. The primary MC system provides the ad hoc group call redirection notification to the MC system where the ad hoc group call is hosted (focus MC service server of the caller's primary MC system) and further to the initiator of the ad hoc group call.

[0096] Information flows Ad hoc group call redirection notify:The Table 1, describes the information flow of an ad　hoc group call redirection notification, which is sent from the MC service server to MC service server and MC service server to an MC service client initiating an ad　hoc group call towards a migrated MC service user.

[0097] Information elementStatusDescriptionMC service IDMThe MC service ID of the MC service user initiating anad　hocgroup call, i.e., calling party. The MC service ID can either be MCPTT ID, MCVideo ID, or MCData ID.MC service IDMThe MC service ID of the target MC service user (i.e., called party), which the MC service user has obtained from its primary MC system before migration. The MC service ID can either be MCPTT ID, MCVideo ID, or MCData ID.MC service IDMThe MC service ID of the target MC service user, which the MC service user has obtained from its migrated MC system after Migration. The MC service ID can either be MCPTT ID, MCVideo ID, or MCData ID.Redirection reasonMThe called MC service user has migrated.

[0098]

[0099] Ad hoc group call procedure towards a migrated MC service user : The following clauses specify the generic procedure for ad　hoc group call towards a migrated MC service user that is utilised by all the MC services (i.e. MCPTT, MCVideo and MCData) in conjunction with the procedures as specified in the respective MC services in 3GPP　TS　23.379

[0016] , 3GPP　TS　23.281

[0012] , and 3GPP　TS　23.282

[0013] .

[0100] Adhoc group calls can be initiated using the participant list provided by the initiator of the call. These calls will be hosted in the primary MC system of the initiator. If one of the requested participants is migrated to a partner MC system, the call should be delivered to the partner MC system to which the MC service user has migrated. The primary MC system of the migrated MC service user assists in redirecting the call to the partner MC system using the partner MC system-assigned MC service ID. The initiator of the call, unaware of the migration, uses an MC service ID assigned by the primary MC system of the migrated MC service user. Both the primary and partner MC system MC service servers are included in call redirection to deliver the call appropriately into the MC system.

[0101] When one of the requested participants is from the interconnected MC system and has migrated to another partner system, the call should be delivered to the partner MC system to which the participant has migrated. The primary MC system of the migrated MC service user assists in redirecting the adhoc group call setup request by providing the partner MC system-assigned MC service ID to the MC system where the adhoc group call is hosted (focus MC service server of the caller's primary MC system). The primary MC system of the migrated MC service user receives the adhoc group call setup request using the primary MC system-assigned MC service ID when the initiator of the call is unaware of the migration of the MC service user. The adhoc group call hosting MC service server of the MC system further delivers the call to the migrated MC service user using the partner MC system-assigned MC service ID.

[0102] FIG 3 illustrates a generic adhoc group call procedure from MC service user 1 using MC service client 1 towards MC service user 2 using MC service client 2, a migrated MC service user 3 using MC service client 3, and a migrated MC service user 4 using MC service client 4. MC system A is the primary MC system of MC service user 3 before migration. MC system B is the primary MC system of MC service user 4 before migration. MC system B is the MC system to which MC service user 3 has migrated, and MC system C is the MC system to which MC service user 4 has migrated. The procedure includes the coordination of multiple MC systems to ensure seamless communication among users, even after migration. Each MC service client is equipped with unique identifiers and communication protocols to facilitate the group call setup and management.

[0103] The procedure is based on the following existing procedures: The ad hoc group call setup procedures as described in clause 10.1.9.3.2.1 of 3GPP TS 23.379, in clause 7.1.9.3.2.1 of 3GPP TS 23.281, or in clause 7.1.7.3.2.1 of 3GPP TS 23.282.

[0104] Several preconditions for the ad hoc group call setup towards migrated MC service user procedures are necessary. The MC system A, MC system B, and MC system C are interconnected MC systems. MC system A serves as the primary MC system for MC service user 1, MC service user 2, and MC service user 3 before migration. MC system B is the MC system to which MC service user 3 has migrated. Similarly, MC system B is the primary MC system for MC service user 4 before migration, and MC system C is the system to which MC service user 4 has migrated. These preconditions ensure that the MC systems can communicate and coordinate effectively, allowing for the seamless transfer of call control and user information between systems.

[0105] MC service user 1, MC service user 2, and MC service user 3 belong to the same home MC system, i.e., the primary MC system, while MC service user 4 belongs to another home MC system, i.e., the partner MC system (which is an interconnected MC system). MC service server A is aware of the migration of MC service user 3 and has been informed of its MC service ID provided by MC system B, as described in clause 10.6.3.3 of 3GPP TS 23.280. Similarly, MC service server B is aware of the migration of MC service user 4 and has been informed of its MC service ID provided by MC system C, as described in clause 10.6.3.3 of 3GPP TS 23.280. This awareness and exchange of information are crucial for maintaining accurate user profiles and ensuring that call requests are directed to the correct MC systems.

[0106] An authorized MC service user 1 at MC service client 1 intends to invite MC service users at MC service client 2, MC service client 3, and MC service client 4 for the ad hoc group call. The ad hoc group call is hosted on MC service server A of MC system A. The hosting server is responsible for managing the call setup, maintaining the call state, and coordinating with other MC systems to include migrated users. The server uses predefined protocols to handle call invitations, user authentication, and resource allocation.

[0107] The steps followed in the ad hoc group call setup, as illustrated in FIG 3, are as follows:

[0108] In step 1, the MC service user 1 (at MC service client 1) initiates an ad hoc group call request towards MC service user 2 (at MC service client 2), MC service user 3 (at MC service client 3) who has migrated to MC system B, and MC service user 4 (at MC service client 4) who has migrated to MC system C. The initiator of the ad hoc group call includes the MC service ID of MC service users in an ad hoc group call request, which are obtained from their primary MC system.

[0109] At step 2, the MC service server A of the MC system A invites the MC service client 2 to the ad hoc group call and successfully establishes the ad hoc group call with the MC service client 2. The server uses signaling messages to communicate the call invitation and establish the connection, ensuring that the client is ready to participate in the group call.

[0110] In step 3, the MC service server A determines that MC service user 3, who has to be invited for the ad hoc group call, has migrated to MC system B with a new MC service ID assigned by MC system B. The server retrieves the updated user information from the interconnected MC systems to ensure accurate call routing.

[0111] Further, at step 4, the MC service server A informs the MC service client 1 that the ad hoc group call request towards MC service user 3 is redirected to MC system B (migrated MC system) by sending an ad hoc group call redirection notification. The ad hoc group call redirection notification includes information about the MC service ID of the target MC service user 3 assigned by both MC system A and MC system B and the reason for the call redirection as user migration. This notification ensures that the initiating client is aware of the redirection and can adjust its call handling accordingly.

[0112] In step 5, the MC service server A of the MC system A invites the MC service client 3 to the ad hoc group call using the MC service ID assigned by MC system B and successfully establishes the ad hoc group call with the MC service client 3. The server uses the updated MC service ID to route the call invitation to the correct MC system, ensuring that the migrated user can join the group call.

[0113] At step 6, the MC service server A of the MC system A further initiates an ad hoc group call request towards the MC service client 4 of the MC system B. The ad hoc group call request is routed to the MC service client 4 via the MC service server B of the MC system B. The routing process includes inter-system communication protocols to ensure that the call request reaches the correct destination.

[0114] The MC service server B of the MC system B determines that MC service user 4, who has to be invited for the ad hoc group call, has migrated to MC system C with a new MC service ID assigned by MC system C, as illustrated in step 7. The server updates its user profile database to reflect the new MC service ID and prepares to redirect the call request accordingly.

[0115] At step 8, the MC service server B informs the MC service server A that the initiation of the ad hoc group call towards MC service user 4 has migrated and been assigned a new MC service ID by MC system C (migrated MC system) by sending an ad hoc group call redirection notification. The ad hoc group call redirection notification includes information about the MC service ID of the target MC service user 4 assigned by both MC system B and MC system C and the reason for the call redirection as user migration. This notification ensures that the initiating server can update its call routing information and proceed with the call setup.

[0116] In step 9, the MC service server A informs the MC service client 1 that the ad hoc group call request towards MC service user 4 is redirected to MC system C (migrated MC system) by sending an ad hoc group call redirection notification. The ad hoc group call redirection notification includes information about the MC service ID of the target MC service user 4 assigned by both MC system B and MC system C and the reason for the call redirection as user migration. This step ensures that the initiating client is aware of the redirection and can adjust its call handling accordingly.

[0117] Furthermore, the MC service server A of the MC system A invites the MC service client 4 to the ad hoc group call using the MC service ID assigned by MC system C and successfully establishes the ad hoc group call with the MC service client 4, as illustrated in step 10. The server uses the updated MC service ID to route the call invitation to the correct MC system, ensuring that the migrated user can join the group call.

[0118] Step 11 illustrates that the MC service server A of the MC system A provides an ad hoc group call response to the MC service client 1 upon receiving a response to the corresponding ad hoc group call request in step 1. The ad hoc group call response will consist of the success or failure result and / or detailed reason information in case of failure. This response ensures that the initiating client is informed of the call setup status and can take appropriate action based on the result.

[0119] Upon successful establishment of an ad hoc group call setup, the call is established amongst the multiple group members from MC system A, MC system B, and MC system C. The media plane and floor control resources are established, as illustrated in step 12. These resources are used for managing the audio and data streams during the group call, ensuring clear communication and efficient floor control.

[0120] FIG 4 is a sequence diagram that illustrates an alternate solution for an ad hoc group call towards migrated MC service users according to an embodiment as disclosed herein. This figure demonstrates an alternate method of an ad hoc group call. The method presents a generic ad hoc group call procedure from MC service user 1 using MC service client 1 towards MC service user 2 using MC service client 2, a migrated MC service user 3 using MC service client 3, and a migrated MC service user 4 using MC service client 4. In this scenario, MC system A is the primary MC system of MC service user 3 before migration, and MC system B is the primary MC system of MC service user 4 before migration. The MC system B is the system to which MC service user 3 has migrated, and MC system C is the system to which MC service user 4 has migrated. This alternate solution provides a different approach to handling user migration and call setup, ensuring flexibility and adaptability in various network configurations.

[0121] The procedure is based on the following existing procedures: The ad hoc group call setup procedures as described in clause 10.1.9.3.2.1 of 3GPP TS 23.379, in clause 7.1.9.3.2.1 of 3GPP TS 23.281, or in clause 7.1.7.3.2.1 of 3GPP TS 23.282. These clauses outline the standardized methods for initiating and managing group calls within MC systems, ensuring interoperability and reliability. The procedures include steps for user authentication, call initiation, and resource allocation, which are used for maintaining the quality and security of the group call.

[0122] Several preconditions for the ad hoc group call setup procedures are necessary. The MC system A, MC system B, and MC system C are interconnected MC systems. MC system A serves as the primary MC system for MC service user 1, MC service user 2, and MC service user 3 before migration. MC system B is the MC system to which MC service user 3 has migrated. MC system B also serves as the primary MC system for MC service user 4 before migration, while MC system C is the MC system to which MC service user 4 has migrated. These preconditions ensure that the MC systems can communicate and coordinate effectively, allowing for the seamless transfer of call control and user information between systems.

[0123] MC service user 1, MC service user 2, and MC service user 3 belong to the same home MC system, i.e., the primary MC system, whereas MC service user 4 belongs to another home MC system, i.e., the partner MC system (which is an interconnected MC system). MC service server A is aware that MC service user 3 has migrated and is informed of its MC service ID provided by MC system B, as described in clause 10.6.3.3 of 3GPP TS 23.280. Similarly, MC service server B is aware that MC service user 4 has migrated and is informed of its MC service ID provided by MC system C, as described in clause 10.6.3.3 of 3GPP TS 23.280. This awareness and exchange of information are crucial for maintaining accurate user profiles and ensuring that call requests are directed to the correct MC systems.

[0124] An authorized MC service user 1 at MC service client 1 intends to invite MC service users at MC service client 2, MC service client 3, and MC service client 4 for the ad hoc group call. The ad hoc group call is hosted on MC service server A of MC system A. The hosting server is responsible for managing the call setup, maintaining the call state, and coordinating with other MC systems to include migrated users. The server uses predefined protocols to handle call invitations, user authentication, and resource allocation.

[0125] The sequence diagram illustrated in FIG 4 follows these steps:

[0126] Step 1 includes the MC service user 1 (at MC service client 1) initiating an adhoc group call request towards MC service user 2 (at MC service client 2), MC service user 3 (at MC service client 3) who has migrated to MC system B, and MC service user 4 (at MC service client 4) who has migrated to MC system C. The initiator of the adhoc group call includes the MC service IDs of the MC service users in the adhoc group call request, which are obtained from their primary MC system. The request is formatted according to standardized protocols to ensure compatibility across different MC systems.

[0127] The MC service server A of MC system A invites MC service client 2 to the adhoc group call and successfully establishes the adhoc group call with MC service client 2, as illustrated in step 2. The server uses signaling messages to communicate the call invitation and establish the connection, ensuring that the client is ready to participate in the group call.

[0128] Step 3 shows the MC service server A determining that MC service user 3, who needs to be invited to the adhoc group call, has migrated to MC system B with a new MC service ID assigned by MC system B. The server retrieves the updated user information from the interconnected MC systems to ensure accurate call routing.

[0129] In step 4, MC service server A informs MC service client 1 that the adhoc group call request towards MC service user 3 is redirected to MC system B (migrated MC system) by sending an adhoc group call redirection notification. This notification includes information about the MC service ID of the target MC service user 3 assigned by both MC system A and MC system B and the reason for the call redirection as user migration. This notification ensures that the initiating client is aware of the redirection and can adjust its call handling accordingly.

[0130] Step 5 includes MC service server A of MC system A inviting MC service client 3 to the adhoc group call using the MC service ID assigned by MC system B and successfully establishing the adhoc group call with MC service client 3. The server uses the updated MC service ID to route the call invitation to the correct MC system, ensuring that the migrated user can join the group call.

[0131] The MC service server A of MC system A further initiates an adhoc group call request towards MC service client 4 of MC system B in step 6. The adhoc group call request is routed to MC service client 4 via MC service server B of MC system B. The routing process includes inter-system communication protocols to ensure that the call request reaches the correct destination.

[0132] Step 7 shows MC service server B of MC system B determining that MC service user 4, who needs to be invited to the adhoc group call, has migrated to MC system C with a new MC service ID assigned by MC system C. The server updates its user profile database to reflect the new MC service ID and prepares to redirect the call request accordingly.

[0133] In step 8, MC service server B informs MC service server A that the initiation of the adhoc group call towards MC service user 4 has migrated and been assigned a new MC service ID by MC system C (migrated MC system) by sending an adhoc group call redirection notification. This notification includes information about the MC service ID of the target MC service user 4 assigned by both MC system B and MC system C and the reason for the call redirection as user migration. This notification ensures that the initiating server can update its call routing information and proceed with the call setup.

[0134] Step 9 illustrates MC service server A informing MC service client 1 that the adhoc group call request towards MC service user 4 is redirected to MC system C (migrated MC system) by sending an adhoc group call redirection notification. This notification includes information about the MC service ID of the target MC service user 4 assigned by both MC system B and MC system C and the reason for the call redirection as user migration. This step ensures that the initiating client is aware of the redirection and can adjust its call handling accordingly.

[0135] Further, in step 10, MC service server B of MC system B invites MC service client 4 to the adhoc group call using the MC service ID assigned by MC system C and successfully establishes the adhoc group call with MC service client 4. The server uses the updated MC service ID to route the call invitation to the correct MC system, ensuring that the migrated user can join the group call.

[0136] Step 11 includes MC service server A of MC system A providing an adhoc group call response to MC service client 1 upon receiving a response to the corresponding adhoc group call request in step 1. The adhoc group call response will consist of the success or failure result and / or detailed reason information in case of failure. This response ensures that the initiating client is informed of the call setup status and can take appropriate action based on the result.

[0137] Upon successful establishment of the adhoc group call setup, a call is established amongst the multiple group members from MC system A, MC system B, and MC system C. The media plane and floor control resources are established, as illustrated in step 12. These resources are used for managing the audio and data streams during the group call, ensuring clear communication and efficient floor control.

[0138] FIG 5A is a flow chart illustrating a method for managing an ad hoc group call in a Mission Critical (MC) communication system comprising a primary MC system and a secondary MC system. Step 501 includes receiving by a first MC service server (25) in the primary MC system (10) an ad hoc group call initiation request from a first MC service client (15) associated with a first MC service user. The ad hoc group call initiation request includes MC service identifiers of a plurality of target MC service users. For example, the ad hoc group call initiation request may include priority levels for each target user, ensuring that high-priority users are given precedence in the call setup. Further, the request can include metadata such as the type of communication (voice, video, or data) and encryption requirements to maintain secure communication.

[0139] In step 502, the first MC service server (25) of the primary MC system (10) invites a second MC service client (20) to join the ad hoc group call by sending the ad hoc group call initiation request using the MC service ID assigned by the secondary MC system (30) and establishes the ad hoc group call with the second MC service client (20). The invitation process includes verifying the availability and readiness of the second MC service client (20) to participate in the call. The server can perform compatibility checks to ensure that the second MC service client (20) can handle the specific type of communication requested. Furthermore, the server may allocate necessary resources such as bandwidth and processing power to support the ad hoc group call.

[0140] Step 503 includes determining by the first MC service server that the third MC service user has migrated to the secondary MC system (30) with a new MC service ID assigned by the secondary MC system (30). This determination may include querying the secondary MC system (30) for updated user status and service identifiers. The server can track the migration history of the third MC service user to ensure accurate and timely updates. Further, the server may update its internal database to reflect the new MC service ID and associated metadata for the third MC service user.

[0141] Step 504 includes transmitting by the first MC service server an ad hoc group call redirection notification to the first MC service client (15) informing the first MC service client (15) that the ad hoc group call request towards the third MC service user is redirected to the secondary MC system (30). The ad hoc group call redirection notification comprises information about the MC service ID of the third MC service user assigned by both the primary MC system (10) and the secondary MC system (30) and the reason for the call redirection being user migration. The notification can include timestamps indicating when the migration occurred and when the redirection was initiated. Further, the notification can include instructions for the first MC service client (15) on how to handle the redirected call, such as updating contact lists or reconfiguring call settings.

[0142] In step 505, the first MC service server transmits an ad hoc group call response to the first MC service client (15) upon receiving responses to the corresponding ad hoc group call request. The ad hoc group call response includes the success or failure result and detailed reason information in case of failure. The response can include diagnostic information to help the first MC service client (15) troubleshoot any issues that may have caused the failure. Furthermore, the response can include performance metrics such as latency, jitter, and packet loss rates to provide insights into the quality of the established call.

[0143] Step 506 includes establishing the ad hoc group call among multiple group members from at least one of the primary MC system (10), the secondary MC system (30), and a tertiary MC system. The establishment process includes setting up secure communication channels and synchronizing media streams across the interconnected MC systems. The server can implement quality of service (QoS) policies to ensure optimal call performance. Further, the server may monitor the call in real-time to detect and resolve any issues that may arise during the communication.

[0144] In one embodiment, the method includes the secondary MC system (30) providing the updated service identifier of the second MC service user to the first MC system (10) upon migration. This process may include secure data exchange protocols to ensure the integrity and confidentiality of the updated service identifier. Another embodiment includes the third MC system (50) being interconnected with the secondary MC system and the primary MC system (10) via a service federation interface. The service federation interface may support various communication standards and protocols to facilitate seamless interoperability among the MC systems. The method also includes, in an embodiment, the redirection notifications sent to the first MC service client (15) including metadata identifying the source and destination MC system of the migrated user. This metadata may include additional details such as user roles, permissions, and communication preferences. Another embodiment includes the ad hoc group call being hosted and managed by the primary MC system (10) irrespective of the migrated status of participating MC service users. The primary MC system (10) may employ advanced load balancing techniques to efficiently manage the call. Further, the first MC service server (25) in the primary MC system (10) coordinates floor control and media plane setup for all MC service clients across the interconnected MC system. The server may use sophisticated algorithms to optimize floor control and ensure fair access to communication resources.

[0145] FIG 5B is a flow chart illustrating a method for managing an ad hoc group call in an MC communication system. The first MC service server establishes an ad hoc group call involving clients across multiple MC systems, detects migration of a user to a different MC system, and initiates redirection of an ad hoc group call. The first MC service server handles ad hoc group call redirection after user migration and re-invites the migrated fourth MC service client using the updated MC service ID assigned by the tertiary MC system. The server can perform additional checks to verify the authenticity and validity of the updated MC service ID before re-inviting the fourth MC service client.

[0146] Step 507 includes inviting by the first MC service server the third MC service client (35) to join the ad hoc group call by sending the ad hoc group call initiation request using the MC service ID assigned by the secondary MC system (30) and establishing the ad hoc group call with the third MC service client. The invitation process may include negotiating communication parameters such as codec selection, encryption methods, and bandwidth allocation. The server can log the invitation details for auditing and troubleshooting purposes.

[0147] Step 508 includes transmitting by the first MC service server (25) an ad hoc group call request towards the fourth MC service client (45) via a second MC service server (40) of the secondary MC system (30), wherein the fourth MC service user at the fourth MC service client (45) has migrated from the secondary MC system (30) to the tertiary MC system. The transmission process may include secure tunneling protocols to protect the integrity and confidentiality of the ad hoc group call request. The server can perform compatibility checks to ensure that the fourth MC service client (45) can handle the specific type of communication requested.

[0148] In step 509, the second MC service server determines that the fourth MC service user has migrated to the tertiary MC system with a new MC service ID assigned by the tertiary MC system. This determination may include querying the tertiary MC system for updated user status and service identifiers. The server can track the migration history of the fourth MC service user to ensure accurate and timely updates. Further, the server may update its internal database to reflect the new MC service ID and associated metadata for the fourth MC service user.

[0149] Step 510 includes transmitting by the second MC service server (40) an ad hoc group call redirection notification to the first MC service server (25) informing the first MC service server (25) that the ad hoc group call initiation towards the fourth MC service user has migrated and is assigned with a new MC service ID by the tertiary MC system. The ad hoc group call redirection notification comprises information about the MC service ID of the fourth MC service user assigned by both the secondary MC system (30) and the tertiary MC system and the reason for the call redirection being user migration. For example, the notification can include timestamps indicating when the migration occurred and when the redirection was initiated. Further, the notification can include instructions for the first MC service server (25) on how to handle the redirected call, such as updating contact lists or reconfiguring call settings.

[0150] Step 511 includes transmitting by the first MC service server (25) to the first MC service client (15) the ad hoc group call redirection. The ad hoc group call redirection notification includes information about the MC service ID of the fourth MC service user assigned by both the secondary MC system (30) and the tertiary MC system and the reason for the call redirection being user migration. For example, the notification can include diagnostic information to help the first MC service client (15) troubleshoot any issues that may have caused the redirection. Furthermore, the notification can include performance metrics such as latency, jitter, and packet loss rates to provide insights into the quality of the redirected call.

[0151] Step 512 includes inviting by the first MC service server (25) the fourth MC service client (45) to join the ad hoc group call by sending the ad hoc group call initiation request using the MC service ID assigned by the tertiary MC system and establishing the ad hoc group call with the fourth MC service client (45). For example, the invitation process can include negotiating communication parameters such as codec selection, encryption methods, and bandwidth allocation. The server can log the invitation details for auditing and troubleshooting purposes.

[0152] In one embodiment, the MC communication system includes the secondary MC system (30) providing the updated service identifier of the second MC service user to the primary MC system (10) upon migration. This process may include secure data exchange protocols to ensure the integrity and confidentiality of the updated service identifier. Another embodiment includes the third MC system (50) being interconnected with the secondary MC system (30) and the primary MC system (10) via a service federation interface. The service federation interface may support various communication standards and protocols to facilitate seamless interoperability among the MC systems. The MC communication system also includes, in an embodiment, the redirection notifications sent to the first MC service client (15) including metadata identifying the source and destination MC system of the migrated user. This metadata may include additional details such as user roles, permissions, and communication preferences. Another embodiment includes the ad hoc group call being hosted and managed by the primary MC system (10) irrespective of the migrated status of participating MC service users. The primary MC system (10) may employ advanced load balancing techniques to efficiently manage the call. Further, the first MC service server (25) in the primary MC system (10) coordinates floor control and media plane setup for all MC service clients across the interconnected MC system. The server may use sophisticated algorithms to optimize floor control and ensure fair access to communication resources.

[0153] Ad hoc group call and migration are important features in the Mission Critical services deployment. Hence, this feature will be implemented mandatorily by all the MC service providers.

[0154] The description of the specific embodiments provided here will clearly reveal their general nature, allowing others to modify or adapt them for various applications without straying from the core concept. Such adaptations and modifications are intended to be included within the scope of the disclosed embodiments. The terminology used is for descriptive purposes only and not meant to limit the scope. Therefore, while preferred embodiments are described, those skilled in the art will understand that modifications can be made within the scope of the described embodiments.

Claims

1.A method performed by a first mission critical (MC) server of a first MC system in a communication system, the method comprising:receiving, from a first MC service client of the first MC system, an ad hoc group call initiation request message including MC service identifiers of a plurality of target MC service users;inviting a second MC service client of a second MC system to join the ad hoc group call by sending the ad hoc group call initiation request message using an MC service ID assigned by the second MC system and establishing the ad hoc group call with the second MC service client;determining that a third MC service user is migrated to the second MC system with a new MC service ID assigned by the second MC system;　transmitting, to the first MC service client of the first MC system, an ad hoc group call redirection notification message informing that the ad hoc group call request towards the third MC service user is redirected to the second MC system, wherein the ad hoc group call redirection notification message includes information about an MC service ID of the third MC service user assigned by the first MC system and the second MC system, and a reason for the call redirection being user migration;transmitting, to the first MC service client, an ad hoc group call response message, wherein the ad hoc group call response message includes the success or failure result and detailed reason information in case of a failure; andestablishing the ad hoc group call among multiple group members from at least one of the first MC system, the second MC system, and a third MC system.2.The method of claim 1, further comprising:inviting a third MC service client of the second MC system to join the ad hoc group call by sending the ad hoc group call initiation request message using the MC service ID assigned by the second MC system and establishing the ad hoc group call with the third MC service client; and　transmitting, to a fourth MC service client via a second MC service server of the second MC system, an ad hoc group call request message wherein a　fourth MC service user at the fourth MC service client has migrated from the second MC system to the third MC system.3.The method of claim 2, further comprising:determining that the fourth MC service user has migrated to the third MC system with a new MC service ID assigned by the third MC system; andreceiving, from the second MC service server of the second MC system, an ad hoc group call redirection notification message informing that the ad hoc group call initiation towards the fourth MC service user has migrated and is assigned with a new MC service ID by the third MC system,wherein the ad hoc group call redirection notification message includes information about the MC service ID of the fourth MC service user assigned by both the second MC system and the third MC system, and the reason for the call redirection being user migration.4.The method of claim 3, further comprising:transmitting, to the first MC service client, the ad hoc group call redirection notification message, wherein the ad hoc group call redirection notification includes information about an MC service ID of the fourth MC service user assigned by both the second MC system and the third MC system, and the reason for the call redirection being user migration; andinviting the fourth MC service client to join the ad hoc group call by sending the ad hoc group call initiation request message using an MC service ID assigned by the third MC system and establishing the ad hoc group call with the fourth MC service client.5.The method of claim 1,wherein the second MC system provides an updated service identifier of the second MC service user to the first MC system upon migration,wherein the third MC system is interconnected with the second MC system and the first MC system via a service federation interface.6.A method performed by a first mission critical (MC) client of a first MC system in a communication system, the method comprising:receiving, from a first MC service server of the first MC system, an ad hoc group call initiation request message including MC service identifiers of a plurality of target MC service users;receiving, from the first MC service server of the first MC system, an ad hoc group call redirection notification message informing that the ad hoc group call request towards a third MC service user is redirected to a second MC system, wherein the ad hoc group call redirection notification message includes information about an MC service ID of the third MC service user assigned by the first MC system and a second MC system, and a reason for the call redirection being user migration; andreceiving, from the first MC service server of the first MC system, an ad hoc group call response message, wherein the ad hoc group call response message includes the success or failure result and detailed reason information in case of a failure.7.The method of claim 6, further comprising:receiving, from the first MC service server, an ad hoc group call redirection notification message, wherein the ad hoc group call redirection notification includes information about an MC service ID of a fourth MC service user assigned by both a second MC system and a third MC system, and a reason for the call redirection being user migration.8.The method of claim 6,wherein the second MC system provides an updated service identifier of a second MC service user to the first MC system upon migration, andwherein the third MC system is interconnected with the second MC system and the first MC system via a service federation interface.9.A first mission critical (MC) server of a first MC system in a communication system, the first MC server comprising:a transceiver, anda controller coupled with the transceiver, and configured to:receive, from a first MC service client of the first MC system, an ad hoc group call initiation request message including MC service identifiers of a plurality of target MC service users,invite a second MC service client of a second MC system to join the ad hoc group call by sending the ad hoc group call initiation request message using an MC service ID assigned by the second MC system and establishing the ad hoc group call with the second MC service client,determine that a third MC service user is migrated to the second MC system with a new MC service ID assigned by the second MC system,　transmit, to the first MC service client of the first MC system, an ad hoc group call redirection notification message informing that the ad hoc group call request towards the third MC service user is redirected to the second MC system, wherein the ad hoc group call redirection notification message includes information about an MC service ID of the third MC service user assigned by the first MC system and the second MC system, and a reason for the call redirection being user migration,transmit, to the first MC service client, an ad hoc group call response message, wherein the ad hoc group call response message includes the success or failure result and detailed reason information in case of a failure; andestablish the ad hoc group call among multiple group members from at least one of the first MC system, the second MC system, and a third MC system.10.The first MC server of claim 9, wherein the controller is further configured to:invite a third MC service client of the second MC system to join the ad hoc group call by sending the ad hoc group call initiation request message using the MC service ID assigned by the second MC system and establishing the ad hoc group call with the third MC service client, and　transmit, to a fourth MC service client via a second MC service server of the second MC system, an ad hoc group call request message wherein a　fourth MC service user at the fourth MC service client has migrated from the second MC system to the third MC system.11.The first MC server of claim 9, wherein the controller is further configured to:determine that the fourth MC service user has migrated to the third MC system with a new MC service ID assigned by the third MC system, andreceive, from the second MC service server of the second MC system, an ad hoc group call redirection notification message informing that the ad hoc group call initiation towards the fourth MC service user has migrated and is assigned with a new MC service ID by the third MC system,wherein the ad hoc group call redirection notification message includes information about the MC service ID of the fourth MC service user assigned by both the second MC system and the third MC system, and the reason for the call redirection being user migration.12.The first MC server of claim 9, wherein the controller is further configured to:transmit, to the first MC service client, the ad hoc group call redirection notification message, wherein the ad hoc group call redirection notification includes information about an MC service ID of the fourth MC service user assigned by both the second MC system and the third MC system, and the reason for the call redirection being user migration, andinvite the fourth MC service client to join the ad hoc group call by sending the ad hoc group call initiation request message using an MC service ID assigned by the third MC system and establishing the ad hoc group call with the fourth MC service client,wherein the second MC system provides an updated service identifier of the second MC service user to the first MC system upon migration,wherein the third MC system is interconnected with the second MC system and the first MC system via a service federation interface.13.A first mission critical (MC) client of a first MC system in a communication system, the first MC client comprising:a transceiver, anda controller coupled with the transceiver, and configured to:receive, from a first MC service server of the first MC system, an ad hoc group call initiation request message including MC service identifiers of a plurality of target MC service users,receive, from the first MC service server of the first MC system, an ad hoc group call redirection notification message informing that the ad hoc group call request towards a third MC service user is redirected to a second MC system, wherein the ad hoc group call redirection notification message includes information about an MC service ID of the third MC service user assigned by the first MC system and a second MC system, and a reason for the call redirection being user migration; andreceive, from the first MC service server of the first MC system, an ad hoc group call response message, wherein the ad hoc group call response message includes the success or failure result and detailed reason information in case of a failure.14.The first MC client of claim 13, wherein the controller is further configured to:receive, from the first MC service server, an ad hoc group call redirection notification message, wherein the ad hoc group call redirection notification includes information about an MC service ID of a fourth MC service user assigned by both a second MC system and a third MC system, and a reason for the call redirection being user migration.15.The first MC client of claim 13,wherein the second MC system provides an updated service identifier of a second MC service user to the first MC system upon migration, andwherein the third MC system is interconnected with the second MC system and the first MC system via a service federation interface.

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