COMMUNICATION NETWORK AND METHOD FOR DECENTRALIZED COMMUNICATION MANAGEMENT VIA THE COMMUNICATION NETWORK

Description

TECHNICAL FIELD OF THE INVENTION

[0001] The technical field of the invention is that of communication networks and more particularly that of communication networks enabling decentralized management of communications.

[0002] The present invention relates to a communication network and more particularly to a communication network enabling decentralized management of communications. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0003] In the 3GPP standard governing 2G or GSM (for "Global System for Mobile Communications"), 3G, 4G or LTE (for "Long-Term Evolution") and 5G mobile networks, and more specifically in MCS (for "Mission Critical Services") mobile communications services within a tactical network, each user has a user server and at least one group server of their own called respectively "home user server" and "home groups server", defined by configuration, from which they can access their user profile and their multimedia groups allowing them to conduct private communications and group communications.

[0004] In the 3GPP MCS standard, these servers are considered reachable by the user, and when this is not the case, the user can optionally register with an isolated local MCS server if such a server has been deployed. However, only communication with users registered with that same local MCS server is possible; access to the communication services offered by the communication network is then considerably limited.

[0005] Therefore, there is a need for a user to be able to access communication services offered by a communication network, regardless of the state of the connection with their "home servers".

[0006] The document EP2887620 entitled "Session Initiation Protocol Messaging" is known from the prior art. SUMMARY OF THE INVENTION

[0007] The invention offers a solution to the problems mentioned above, by allowing a user to communicate with other users of a communication network independently of the state of their connection with their "home servers".

[0008] A first aspect of the invention relates to a communication network allowing at least one user equipment, through configuration information, to access communication services, the communication being a private communication or a communication within a multimedia group to which the user equipment is affiliated, the communication network comprising a plurality of servers and being characterized in that each server which the user equipment is authorized to access contains the configuration information of the user equipment.

[0009] Thanks to the invention, since the configuration information necessary for authentication and registration for user access to communication services is stored on all servers in the communication network that the user is authorized to access, the user can authenticate and register with any of the network servers and continue communicating with other users as if connected to their home servers. Communication management is therefore no longer centralized at the home server level but distributed across all servers in the communication network.

[0010] In addition to the characteristics mentioned in the preceding paragraph, the process according to a first aspect of the invention may have one or more complementary characteristics from among the following, considered individually or according to all technically possible combinations.

[0011] According to one embodiment, a plurality of servers in the communication network share a multicast signaling session.

[0012] Thus, each server sharing the signaling session can send a message to all other servers in the signaling session.

[0013] According to a variant of the previous embodiment, the signaling session is configured in each server sharing the signaling session.

[0014] According to an embodiment variant of the preceding embodiment compatible with the preceding embodiment variant, each server is configured to join the signaling session as soon as a first user device has registered with it.

[0015] Thus, a server to which no user equipment is connected does not receive messages sent via the signaling session.

[0016] According to an embodiment variant of the preceding embodiment compatible with the preceding embodiment variants, each server is configured to join the signaling session and send the list of user equipment that are registered with it, when said server connects or reconnects to the communication network.

[0017] Thus, the server informs other servers of the user equipment connected to it so that other servers can initiate private communications with this user equipment.

[0018] According to an embodiment compatible with the previous embodiment, each other server in the communication network is configured to respond by publishing the list of user equipment that is registered with it.

[0019] Thus, the server that connects or reconnects to the communication network knows all the users of the communication network and can contact them for private communications.

[0020] According to an embodiment compatible with the preceding embodiment, each multimedia group includes a multicast group session shared between the servers with which user devices affiliated with the multimedia group are registered.

[0021] Thus, users in a multimedia group can communicate and exchange data or videos via the group session.

[0022] According to a variant of the preceding embodiment, each server is configured to join a group session when one of the user devices registered with it joins the corresponding multimedia group.

[0023] Thus, the new user can communicate and exchange data with other users of the multimedia group to which he has just joined.

[0024] According to an embodiment of the preceding embodiment compatible with the preceding embodiment, each server is configured to join the group session(s) to which the user devices registered with it are affiliated when said server connects or reconnects to the communication network.

[0025] Thus, users authenticated with the server can communicate and exchange data with other users in the multimedia group.

[0026] According to an embodiment compatible with the preceding embodiments, each server includes a transmission management module.

[0027] Thus, each server has a module capable of managing the audio input and the video transmission input in a multimedia group.

[0028] A second aspect of the invention relates to a method for decentralized management of communications via a communication network comprising a plurality of servers, characterized in that it comprises the following steps: Authentication and registration of a user device with a first server of the communication network; Sending, by the first server, of a message signaling the authentication and registration of the user device, to the other servers of the communication network; Communication of the user device with at least one other user device authenticated and registered with a server of the communication network, the communication being a private communication or a communication within a multimedia group to which the user device is affiliated.

[0029] Thus, once the user equipment is connected to a server, the server informs all other servers so that they can join the user equipment in a private communication.

[0030] According to one embodiment, if the user equipment had already registered with another server on the communication network, the message includes an identifier of the other server.

[0031] Thus, the servers know that the user's equipment is no longer reachable via the other server.

[0032] According to an embodiment compatible with the previous embodiment, the message sending step is performed via the signaling session.

[0033] Thus, the message is sent to all servers on the network with which a user device is registered, and these servers can contact the user device as part of a private communication.

[0034] According to an embodiment compatible with the preceding embodiments, communication within a multimedia group is carried out via the corresponding group session.

[0035] Thus, the user equipment can communicate and exchange data with other user equipment in the multimedia group.

[0036] According to an embodiment compatible with the preceding embodiments, during each multimedia group communication, transmission management is dynamically assigned between the transmission management modules of the communication network servers sharing the group session.

[0037] Thus, at any given moment, the transmission management module that manages audio speaking and video transmission within the multimedia group is that of the server to which the user speaking or transmitting a video is affiliated, and transmission management is no longer centralized at the level of the "home servers".

[0038] The invention and its various applications will be better understood by reading the following description and examining the accompanying figures. BRIEF DESCRIPTION OF THE FIGURES

[0039] The figures are presented for illustrative purposes only and are in no way limiting to the invention. There figure 1 shows a schematic representation of a communication network according to a first aspect of the invention. figure 2 shows a synoptic diagram of a process according to a second aspect of the invention. DETAILED DESCRIPTION

[0040] Unless otherwise specified, the same element appearing on different figures has a unique reference.

[0041] A first aspect of the invention relates to a communication network enabling decentralized management of communications.

[0042] A "communication network" is defined as a network that provides access to communication services, that is, services related to communication, such as voice, video, or file-sharing services for interacting with one or more user devices. Communication services enable private communication between two user devices or group communication between user devices belonging to the same multimedia group.

[0043] The term "multimedia group" refers to a group comprising several user devices that can interact with each other once authenticated and registered with a server on the communication network that allows access to the multimedia group.

[0044] The term "user equipment authenticated with a server" means user equipment whose identity has been verified and / or validated by a server during an electronic exchange.

[0045] A "user device registered with a server" is defined as a user device connected to a server and therefore reachable for private communications via that server. A user device cannot register with a server if it has not first authenticated itself with that same server.

[0046] We define "decentralized communication management" as opposed to "centralized communication management," which is management carried out centrally at the level of the home servers of the user equipment that initiates the communication.

[0047] The communication network complies, for example, with the 3GPP MCS standard, that is to say, it is compatible with the 3GPP MCS standard and more particularly with the current version of 3GPP which is version 15, with previous versions from version 13 and with subsequent versions incorporating all the features of the invention.

[0048] The 200 communication network can be fixed, for example a communication network covering a company, or mobile, i.e. tactical, used, for example, in the case of a special forces mission.

[0049] The communication network according to a first aspect of the invention comprises at least one user device and a plurality of servers.

[0050] [ Fig. 1 ] There figure 1 shows a schematic representation of the communication network 200 according to a first aspect of the invention.

[0051] The communication network 200 comprises four user devices U1, U2, U3, U4.

[0052] A user device U1, U2, U3, U4 is, for example, a smartphone, a tablet, or a laptop. Generally, user devices U1, U2, U3, U4 have a screen.

[0053] The 200 communication network also includes four servers S1, S2, S3, S4.

[0054] Each server S1, S2, S3, S4 is for example compatible with the 3GPP MCS standard with regard to the client-server interface.

[0055] A server S1, S2, S3, S4 of the communication network 200 then includes an IDMS identity management module, a CMS configuration management module, a GMS multimedia group management module and a KMS encryption key management module.

[0056] The IDMS identity management module is configured to receive and process authentication requests sent by user devices U1, U2, U3, U4.

[0057] The CMS configuration management module is configured to receive a user profile request and send a user profile to each user device U1, U2, U3, U4 whose authentication request is accepted by the IDMS identity management module of the server S1, S2, S3, S4.

[0058] The GMS multimedia group management module is configured to receive a request for multimedia group profiles and send at least one multimedia group profile to each user device U1, U2, U3, U4 whose authentication request is accepted by the IDMS identity management module of the server S1, S2, S3, S4.

[0059] The KMS encryption key management module is configured to receive an encryption key request and send at least one encryption key to each user device U1, U2, U3, U4 whose authentication request is accepted by the IDMS identity management module of the server S1, S2, S3, S4. The received encryption key(s) then allow the user device U1, U2, U3, U4 to generate its own encryption keys for private communications.

[0060] An S1, S2, S3, S4 server of the 200 communication network includes, for example, an FCS (for "Floor Control Server") transmission management module.

[0061] The FCS transmission management module of an S1, S2, S3, or S4 server is configured to manage, in a decentralized manner, voice transmission during audio communication within a multimedia group to which user devices U1, U2, U3, and U4 registered with said server S1, S2, S3, and S4 are affiliated, and transmission during video communication. The FCS transmission management module does not manage email services with file exchange.

[0062] In the communication network 200 illustrated at the figure 1User equipment U4 is registered with server S1, user equipment U1 is registered with server S2 and user equipment U2, U3 are registered with server S3, which is materialized by solid bidirectional arrows between user equipment U4 and server S1, between user equipment U1 and server S2, between user equipment U2 and server S3 and between user equipment U3 and server S3.

[0063] No user equipment U1, U2, U3, U4 is registered with the S4 server.

[0064] In the communication network 200 according to a first aspect of the invention, the configuration information necessary for authentication and registration for access to communication services by a user equipment U1, U2, U3, U4 is duplicated in each server S1, S2, S3, S4 of the communication network 200 to which said user equipment U1, U2, U3, U4 is authorized to access.

[0065] Thus, on the figure 1 , assuming that user equipment U1, U2, U3, U4 has access to all servers S1, S2, S3, S4 of communication network 200, the configuration information of user equipment U1, U2, U3, U4 is configured in each of the servers S1, S2, S3, S4 of communication network 200.

[0066] Each user device U1, U2, U3, U4 can therefore authenticate and register with any of the servers S1, S2, S3, S4 of the communication network 200. There are therefore no longer any "home servers" in the strict sense, each server S1, S2, S3, S4 acting as a "home server" if the user device U1, U2, U3, U4 registers with it.

[0067] In the case where the servers S1, S2, S3, S4 are MCS servers, the configuration information includes, for example, the identifier, the user profile, the multimedia group profile(s) and the encryption key(s).

[0068] The identifier is then stored in the IDMS identity management module, the user profile in the CMS configuration management module, the multimedia group profile(s) in the GMS multimedia group management module and the encryption key(s) in the KMS encryption key management module of each of the S1, S2, S3, S4 servers which the user equipment U1, U2, U3, U4 is authorized to access.

[0069] A second aspect of the invention relates to a decentralized communications management method via the communication network 200 according to a first aspect of the invention.

[0070] [ Fig. 2 ] There figure 2 shows a synoptic diagram of process 100 according to a first aspect of the invention.

[0071] The first step 101 of process 100 consists of the authentication and registration of a user equipment U1, U2, U3, U4 with a server S1, S2, S3, S4 of the communication network 200, called the first server.

[0072] The first server S1, S2, S3, S4 uses, for example, a standard protocol for authentication, such as the OpenIDConnect protocol developed in the 3GPP MCS standard.

[0073] According to this protocol, the first authentication step 101 includes a first sub-step consisting of the sending, by the user equipment U1, U2, U3, U4, of an authentication request or query to the IDMS identity management module of the first server S1, S2, S3, S4.

[0074] The authentication request is then processed by the IDMS identity management module of the first server S1, S2, S3, S4 during a second sub-processing step.

[0075] This second sub-step of processing itself comprises several sub-steps: a first sub-step of receiving the authentication request sent by the user equipment U1, U2, U3, U4 by the IDMS identity management module; a second sub-step of sending a request for at least one authentication information to the user of the user equipment U1, U2, U3, U4 by the IDMS identity management module and receiving the request by the user equipment U1, U2, U3, U4; a third sub-step of providing the authentication information requested by the user using the user equipment U1, U2, U3, U4; a fourth sub-step of sending the authentication information provided by the user to the IDMS identity management module and receiving the authentication information by the IDMS identity management module;a fifth sub-step of traversing a user database (BDD) from the first server S1, S2, S3, S4 by the IDMS identity management module to determine whether the user database (BDD) contains authentication information or not.

[0076] At the end of the fifth substep of the second processing substep, if the IDMS identity management module has not found the authentication information, the authentication request is rejected. Conversely, if the IDMS identity management module has found the authentication information, the authentication request is accepted.

[0077] Authentication information is, for example, a password and / or a username and / or biometric data.

[0078] The user database (BDD) is, for example, a database of identifiers that links authentication information with a corresponding identifier.

[0079] If the authentication request is accepted, the identifier corresponding to the authentication information of user 302 is sent to user equipment U1, U2, U3, U4.

[0080] In a second substep of the first step 101 of process 100, the identifier is used to obtain a user profile. Specifically, user devices U1, U2, U3, and U4 send a user profile request to the configuration management module (CMS) of the first server S1, S2, S3, and S4. This user profile request includes the identifier. User devices U1, U2, U3, and U4 then receive the user profile corresponding to the identifier in return.

[0081] The user profile may contain a list of multimedia group identifiers corresponding to the multimedia groups to which their user profile gives them access.

[0082] In a third substep of the first step 101 of process 100, user equipment U1, U2, U3, U4 sends a multimedia group profile request to the multimedia group management module (GMS) of the first server S1, S2, S3, S4. This multimedia group profile request includes the identifier. User equipment U1, U2, U3, U4 then receives in return the multimedia group profile associated with each multimedia group identifier from the multimedia group identifier list.

[0083] In a fourth substep of the first step 101 of process 100, user equipment U1, U2, U3, U4 sends a request for encryption keys to the KMS encryption key management module of the first server S1, S2, S3, S4. The encryption key request includes the identifier. User equipment U1, U2, U3, U4 then receives at least one encryption key in return.

[0084] Once the user equipment U1, U2, U3, U4 has received the user profile, the multimedia group profile(s), and the encryption key(s), the user equipment U1, U2, U3, U4 has all the configuration elements allowing it to access the communication services offered by each multimedia group whose profile it has obtained and the private communication services.

[0085] The first server S1, S2, S3, S4 uses for example a standard protocol for registration, such as the SIP protocol ("for Session Initiation Protocol"), consisting of the sending by the user equipment U1, U2, U3, U4 of a SIP message containing an identifier retrieved from the IDMS identity management module during authentication.

[0086] A second step 102 of process 100 consists in the sending, by the first server S1, S2, S3, S4, of a message informing that the user equipment U1, U2, U3, U4 has authenticated and registered with it, to the other servers S1, S2, S3, S4 of the communication network 200.

[0087] The message may include an identifier of another server S1, S2, S3, S4 of the communication network 200 if the user equipment U1, U2, U3, U4 had already registered with that other server S1, S2, S3, S4 before trying to register with the first server S1, S2, S3, S4.

[0088] According to one embodiment, the message is sent via a multicast signaling session shared between several servers S1, S2, S3, S4 of the communication network 200.

[0089] A "signaling session" is a session usually used for the exchange of service messages between the servers of a network or between them and user equipment connected to the network, which are necessary for the establishment and management of communications.

[0090] A "multicast session" is defined as a session in which data is broadcast from a sender to at least one receiver.

[0091] The signaling session is defined for example by configuration in the S1, S2, S3, S4 servers of the 200 communication network.

[0092] For example, on the figure 1 , servers S1, S2 and S3 share an SS signaling session.

[0093] Thus, the information from user equipment U1 was sent to servers S1 and S3 after its registration via the SS signaling session.

[0094] For example, a server S1, S2, S3, S4 of the communication network 200 joins the SS signaling session if a first user device U1, U2, U3, U4 registers with it.

[0095] Thus, on the figure 1 no user equipment U1, U2, U3, U4 has ever registered with the S4 server which does not belong to the SS signaling session.

[0096] For example, when a new server joins the 200 communication network, or when a server (S1, S2, S3, or S4) on the 200 communication network loses connection to the 200 communication network and then reconnects, the server joins the signaling session and multicasts a list containing the user devices U1, U2, U3, and U4 that are registered with it. The other servers (S1, S2, S3, and S4) on the 200 communication network respond by also sending the list of user devices U1, U2, U3, and U4 that are registered with each of them.

[0097] Thus, each server S1, S2, S3, S4 of the communication network 200 is informed of the presence of each registered user device U1, U2, U3, U4 and can initiate communication with each registered user device U1, U2, U3, U4.

[0098] A third step 103 of process 100 consists, for user equipment U1, U2, U3, U4, in communicating with another user equipment U1, U2, U3, U4 registered with a server S1, S2, S3, S4 of the communication network 200 during a private communication or in communicating with a plurality of user equipment U1, U2, U3, U4 each registered with a server S1, S2, S3, S4 of the communication network 200 during a communication within a multimedia group to which user equipment U1, U2, U3, U4 is affiliated.

[0099] Each multimedia group to which a U1, U2, U3, U4 user device is affiliated offers group communication services, allowing the U1, U2, U3, U4 user device to communicate with other U1, U2, U3, U4 user devices affiliated with the multimedia group.

[0100] For this purpose, each multimedia group includes a multicast SG group session shared between the S1, S2, S3, S4 servers of the 200 communication network with which user equipment U1, U2, U3, U4 affiliated with the multimedia group are registered.

[0101] On the figure 1 , the S2 and S3 servers share a multicast SG group session, which allows, for example, user devices U1, U2 and U3 to communicate within the multimedia group.

[0102] For example, in the case where a user device U1, U2, U3 wants to send a file to the other devices U1, U2, U3 of the multimedia group, the file being stored in the server S2, S3 with which the user device U1, U2, U3 sending the file is registered, the group session SG is used to store the link to this file in each server S2, S3 so that each user device U1, U2, U3 affiliated with the multimedia group can have access to the file even if the server S2, S3 to which the user device U1, U2, U3 is connected loses its connection with the communication network 200.

[0103] For example, when a user device U1, U2, U3, U4 joins a multimedia group, the server S1, S2, S3, S4 to which it is affiliated joins the corresponding group session SG of said multimedia group.

[0104] For example, when a new server joins the communication network 200 or when a server S1, S2, S3, S4 of the communication network 200 loses connection to the communication network 200 and then reconnects to the communication network 200, the server joins the group session(s) corresponding to one or more multimedia groups to which the user equipment U1, U2, U3, U4 registered with said server S1, S2, S3, S4 are affiliated.

[0105] Audio communications within a multimedia group are typically of the "Push-To-Talk" (PTT) type, and during each multimedia group communication, the turn-taking is managed by the FCS transmission management module of an S2 or S3 server on the 200 communication network, which shares the multimedia group's SG session. Similarly, during each multimedia group video communication, the turn-taking is managed by the FCS transmission management module.

[0106] The management of speaking or transmitting within the multimedia group is dynamically allocated between the FCS transmission management modules of the S2 and S3 servers of the 200 communication network sharing the multimedia group's SG session. Therefore, the FCS transmission management module handling speaking or transmitting within a multimedia group is generally not the same at every moment of the communication.

[0107] For example, if user device U1 initiates an audio communication, the FCS transmission management module of server S2, with which user device U1 is registered, initially manages the transmission. If user device U2 then wants to speak and user device U1 is already communicating, server S3, with which user device U2 is registered, requests the transmission from server S2. If user device U2 is assigned a higher priority than user device U1, server S2 grants the transmission to user device U2, and the FCS transmission management module of server S3 takes over the transmission management. Otherwise, user device U1 retains the transmission.

[0108] If user device U1 is not communicating, the group session SG broadcasts a message indicating that the floor is open. User device U2 can then take the floor, and the FCS speech module of server S3 takes over managing the floor.

[0109] If multiple user devices (U2, U3) request to speak simultaneously, the S2 server, whose FCS transmission management module handles the transmission, grants the right to the user device (U2, U3) with the highest priority. If the user devices (U2, U3) have the same priority, the S2 server grants the right to the user device (U2, U3) whose request it received first.

Claims

1. Communication network (200) compliant with the 3rd Generation Partnership Project Mission Critical Service standard versions 13 to 15, also called 3GPP MCS versions 13 to 15, allowing at least one user device (U1, U2, U3, U4), thanks to configuration information, to access communication services, the communication being a private communication or a communication within a multimedia group with which the user device (U1, U2, U3, U4) is affiliated, the communication network (200) comprising a plurality of servers (S1, S2, S3, S4) and each server (S1, S2, S3, S4) of the plurality of servers (S1, S2, S3, S4) to which the user device (U1, U2, U3, U4) is authorized to access comprises the configuration information of the user device (U1, U2, U3, U4), and wherein at least two servers (S1, S2, S3, S4) of the plurality of servers (SI, S2, S3, S4) share a multicast signalling session (SS), each server (S1, S2, S3, S4) being configured to join the signalling session (SS) and send the list of user devices (U1, U2, U3, U4) that are registered with it when said server (S1, S2, S3, S4) connects or reconnects to the communication network (200), the network being characterized in that each multimedia group comprises a multicast group session (SG) shared between the servers (S1, S2, S3, S4) with which user devices (U1, U2, U3, U4) affiliated with the multimedia group is registered.

2. Communication network (200) according to the preceding claim, characterised in that the signalling session is configured in each server (S1, S2, S3, S4) that shares the signalling session (SS).

3. Communication network (200) according to claim 2, characterised in that each server (S1, S2, S3, S4) is configured to join the signalling session (SS) as soon as a first user device (U1, U2, U3, U4) has registered with it.

4. Communication network (200) according to any of the preceding claims, characterised in that, each other server (S1, S2, S3, S4) of the communication network (200) is configured to respond by publishing the list of user devices (U1, U2, U3, U4) that are registered with it.

5. Communication network (200) according to any of the preceding claims, characterised in that each server (S1, S2, S3, S4) is configured to join a group session (SG) when one of the user devices (U1, U2, U3, U4) registered with it is affiliated with the corresponding multimedia group.

6. Communication network (200) according to any of the preceding claims, characterised in that each server (S1, S2, S3, S4) is configured to join the group session or sessions with which the user devices (U1, U2, U3, U4) that are registered with it are affiliated, when said server (S1, S2, S3, S4) connects or reconnects to the communication network (200).

7. Communication network (200) according to any of the preceding claims, characterised in that each server (S1, S2, S3, S4) comprises a transmission management module (FCS).

8. Method (100) of decentralised management of communications via the communication network (200) compliant with the 3rd Generation Partnership Project Mission Critical Service standard, according to any of the preceding claims, characterised in that it comprises the following steps: - Authenticating and registering a user device (U1, U2, U3, U4) with a first server (S1, S2, S3, S4) among the plurality of servers (S1, S2, S3, S4) of the communication network (200, 101); - Sending, by the first server (S1, S2, S3, S4), of a message signalling the authentication and the registration of the user device (U1, U2, U3, U4), to the other servers (S1, S2, S3, S4) of the communication network (200, 102); - Communicating of the user device (U1, U2, U3, U4) with at least one other user device (U1, U2, U3, U4) authenticated and registered with a server (S1, S2, S3, S4) of the plurality of servers (S1, S2, S3, S4) of the communication network (200), the communication being a private communication or a communication within a multimedia group with which the user device (U1, U2, U3, U4) is affiliated (103).

9. Method (100) according to claim 8, characterised in that if the user device (U1, U2, U3, U4) had already registered with another server (S1, S2, S3, S4) of the plurality of servers (S1, S2, S3, S4), the message comprises an identifier of the other server (S1, S2, S3, S4).

10. Method (100) according to any of claims 8 to 9 via the communication network (200) of which at least two servers (S1, S2, S3, S4) share a multicast signalling session (SS), characterised in that the step (102) of sending the message is carried out via the signalling session (SS).

11. Method (100) according to any of claims 8 to 10 via the communication network (200), characterised in that the communication within a multimedia group is carried out via the corresponding group session (SG).

12. Method (100) according to any of claims 8 to 11 via the communication network (200) of which each server (S1, S2, S3, S4) comprises a transmission management module (FCS), characterised in that, during each multimedia group communication, the management of the transmission is assigned dynamically between the transmission management modules (FCS) of the servers (S1, S2, S3, S4) of the plurality of servers (S1, S2, S3, S4) that are sharing the group session (SG).