WO2006026937A1

WO2006026937A1 - Method for message transmission within a group of communication terminals

Info

Publication number: WO2006026937A1
Application number: PCT/DE2004/002009
Authority: WO
Inventors: Peter Kim; Frank Mademann
Original assignee: Siemens Aktiengesellschaft
Priority date: 2004-09-06
Filing date: 2004-09-06
Publication date: 2006-03-16

Abstract

The invention relates to a method for message transmission within a group of communication terminals, whereby a number of communication terminals of the group are allocated an IP Multicast address and a message addressed with said IP Multicast address is simultaneously transmitted to the number of communication terminals by means of a broadcast or multicast transmission service of a mobile communication network.

Description

description

Method for transmitting messages within a group of communication terminals

The invention relates to a method for message transmission within a group of communication terminals.

In modern telecommunication networks, methods are generally known in which various communication terminals form a group and in which messages are exchanged between the communication terminals of this group. Such a method is used, for example, in the group communication service "Push-to-talk over Cellular." In this group communication service, messages can be exchanged between the communication terminals of the group without a connection being set up for each individual message Instead, in the group communication service, message transmission to the communication terminals of the group is initiated by a simple keystroke, for example a so-called method for transmitting messages within a group IP multimedia conferencing service, for example, from the publication "3GPP TS 24.147 V1.0 (2004-06), Technical Specification, 3rd Generation Partnership Project; Technical Specification Group Core Network; Conferencing using the IP Multimedia (IM)" Core Network (CN) Subsys tem "is known.

The invention has for its object to provide a method of - - type mentioned above, with the least effort and inexpensive messages within a group of communication terminals can be transmitted.

This object is achieved according to the invention by a method for message transmission within a group of communication terminals, in which method a plurality of communication terminals of the group is assigned an IP multicast address, and a message addressed with this IP multicast address simultaneously the plurality of communication terminals are transmitted by means of a broadcast or multicast transmission service of a mobile communication network. A broadcast transmission service is also referred to as a "broadcast call", in the broadcast transmission service the message is transmitted to all the (receiving) communication terminals of the group. The multicast transmission service is also called "point to multipoint". Transmission "; In this case, the message is simultaneously transmitted to a plurality of communication terminals of the group. IP multicast addresses as such are known, for example, from the publication "Request for Members: 3330, IANA, September 2002", in particular from chapters 2 and 3. These are selected IP addresses which are used for transmission of messages are reserved by means of the IP multicast method.

In the method according to the invention, it is particularly advantageous for messages to be transmitted within the group of communication terminals by means of the broadcast or multicast transmission service of a mobile communication service. As a result, the communication resources of the group can share the transmission resources (eg communication channels or data transmission bandwidths). In particular, it is avoided that for each communication cation terminal of the group own Datenübertragungsressour¬ cen need to be reserved exclusively. As a result, a very resource-saving (low resource cost) and thus cost-effective transmission of messages is possible.

According to the invention, the method can be configured in such a way that the IP multicast address of the plurality of communication terminals is assigned to a server controlling the message transmission (in order, for example, to receive messages).

The method according to the invention can also proceed in such a way that the message addressed by the IP multicast address is transmitted by the server controlling the message transmission to the plurality of communication terminals.

As such a server, for example, a push-to-talk server of a push-to-talk service can be used. As such a messaging controlling server, an IMS conference server may also be used. In the abovementioned embodiments of the method according to the invention, the assignment of the IP multicast address or the outside of the message addressed with the IP multicast address is controlled by the message transmissions which are present anyway (and / or are already known) Server made. As a result, the method according to the invention can be carried out relatively inexpensively, since typically only existing hardware needs to be adapted to the new method. There is no need to reinstall additional hardware.

The method according to the invention can be designed such that the message addressed with the IP multicast address is transmitted by means of a BündeIfunk system to the plurality of Kommuni¬ cation terminals.

The inventive method can also be configured so that the message addressed with the IP multicast address is transmitted to the plurality of communication terminals by means of a wireless local area network (WLAN). This allows the resource-saving and efficient transmission of messages even in trunked radio systems or wireless local area networks.

However, the method according to the invention can also proceed in such a way that the message addressed by the IP multicast address is transmitted by a communication terminal of the group directly to one, several or all communication terminals of the plurality of communication terminals. Direct transmission of the message here means transmission of the message from the one communication terminal to or the (destination) communication terminal (s) of the plurality of communication terminals, which without intermediate circuit of other receiving stations, transmitting stations, exchanges or the like Facilities are done. Thus, without the use of further means, the message is transmitted directly from the one communication terminal via the air interface to the communication terminal (s) of the plurality of communication terminals. No further units of the mobile communications network are involved in this transmission.

The method according to the invention can be designed such that the message addressed with the IP multicast address is transmitted using a direct transmission mode of a burst radio method. Trunked radio method as such (for example TETRA) are known, for example, from the publication "ETSI TECHNICAL REPORT, ETR 300-1, May 1997, Terrestrial Trunked Radio (TETRA); Voice plus Data (V + D); Desigers'guide; Part 1: Overview, technical description and spatial aspects ".

The method according to the invention can also be embodied such that the message addressed with the IP multicast address is transmitted using an ad hoc transmission mode of a wireless local area network data transmission method.

The method according to the invention can proceed in such a way that the number of communication terminals of the group located in a predetermined spatial area of a mobile radio network is determined. If a predetermined number of digits is undershot, the communication terminals located in the area each have an IP unicast. Address zuge¬ meadows and a addressed with one of these IP unicast addresses message via a exclusively the jeweili¬ gen Kommunikationsausgerät assigned message transmission channel to the respective communication terminal will transmit gen, or when exceeding the preselected limit number of the plurality the IP multicast address is assigned to the communication terminals located in the area, and the message addressed with this IP multicast address is simultaneously sent to the plurality of communication terminals by means of the broadcast or multicast transmission service of the mobile communication system network is transmitted.

As a result, it is advantageously achieved that the transmission is carried out by means of the broadcast or multicast transmission service only when one of the Limit number exceeding number of Kommunikationsendge¬ devices of the group in a predetermined spatial area (for example, in a radio cell) of the mobile network be¬ finds. If there are fewer communication terminals than the preselected limit number in the predetermined spatial area, then the respective communication terminals are each assigned an IP unicast address and the message is transmitted via a unicast message transmission channel (ie via a exclusively communication terminal assigned to the communication terminal) transmit to the respective communication terminal. The message addressed with the IP multicast address can also be transmitted, for example, by means of a WLAN and trunked radio. IP unicast addresses are generally known: These are, for example, those IP addresses which are assigned to a mobile telephone, for example, for participation in the known WAP method (WAP = Wireless Application Protocol). For example, this WAP method uses the IP unicast address to deliver specific Internet pages to the mobile phone.

In the abovementioned embodiment variant of the method according to the invention, it is particularly advantageous that the broadcast or multicast transmission service is used only when the preselected limit number is exceeded. This ensures a particularly efficient and cost-effective Nachrichten¬ transmission. The reason for this is due to the fact that when using broadcast or multicast transmission services for the control of the transmission power of base stations of the mobile communication network, a great deal of effort has to be made which does not exist due to the different transmission conditions to the respective communication terminals necessarily leads to optimal transmission power and thus vor¬ geous use of resources. This control must often be based on the communication terminal of the group which is worst able to receive the messages. Since, according to the invention, the broadcast or multicast transmission service is used only in the number of communication terminals exceeding the limit number in the predetermined spatial area, the advantages due to the efficient sharing of network resources are unequal greater than the effort required to control the transmission power. In the case of a small number of communication terminals in the predetermined spatial area, however, a transmission is advantageously used via a respective message channel exclusively assigned to the respective communication terminals by means of an IP unicast address, so that the comparatively simple or more effective control is then also used the transmission power is made possible at the acceptance of a separate use of transmission resources of the mobile communication network an efficient message transmission (data transmission).

The method according to the invention can, however, also be such that, for a predetermined spatial area of a mobile radio network, irrespective of the number of communication terminals of the group located in this area, it is predetermined whether an IP unicast station is located in this area. Address or an IP multicast address is assigned. This fixed specification, whether in the predetermined spatial area the communication terminals of the

One IP address or one IP multicast address is assigned to each group fast and simple decision on the type of message transmission to be used.

The method according to the invention can also run such that the server transmits an information message to the first communication terminal of the group, whereby these first communication terminals are informed that they (eg, within the next 60 seconds, for example, within a short time) a transmission permission message for Sending a message to the other communication terminals of

Group are then received, and are then reserved by these first Kom¬ munikationsendgeräten before receiving the transmission permission message transmission resources of Mobilkommunktionsnet- zes, the WLAN or the trunk radio for sending the Nachs rieht. By reserving transmission resources of the mobile communication network even before the transmission permission message is received, it is advantageously made possible that the message can be sent immediately after receipt of the transmission permission message from the respective communication terminal (which requests a transmission permission) and no undesired time delays ¬ occur.

The inventive method can be configured such that the messages transmitted by the server to a communication terminal of the group are encrypted by means of an encryption method operating within or above the IP protocol level. Within or above the IP protocol level, such an encryption method can advantageously be implemented with little effort, since interactions with and adaptations of the respective often present encryption methods (eg, the bundle) radio, the WLAN or the mobile radio system), which work below the IP protocol level.

The method according to the invention can also run such that an IP multicast address for the group of communication terminals is requested by the server from an IP address administration device, and the plurality of communication terminals of the group receive these IP multicast addresses. Address zu¬ ordered, and is informed by the server, the IP address management device about an end of the use of the IP multicast address, whereupon the IP multicast address for other message transmissions of other groups can be called. This advantageously makes it possible to implement the method according to the invention, in particular even in the case of a large number of different groups of communication terminals and with a limited number of IP multicast addresses. Namely, it is advantageously avoided that individual IP multicast addresses are permanently assigned to a group of communication terminals and thus blocked for further use by other groups.

The method according to the invention is explained in more detail below on the basis of exemplary embodiments. 1 shows a schematic representation of elements involved in a method for message transmission within a group of communication terminals, FIG. 2 shows an exemplary method sequence of the inventive method, and FIG. 3 shows a further exemplary method sequence of the method according to the invention. " Messages within a group of kommuni¬ kationsendgeräten take place, for example, in so-called push-to-talk services (PTT services). When using a mobile communication network, such services are also referred to as push-to-talk-over-cellular (POC) services. These services allow data messages or voice messages to be sent from a communication terminal of a group of communication terminals to one, several or all other communication terminals of the group. The communication terminals can be stationary (eg stationary landline telephones) or mobile (eg mobile telephones). In the case of push-to-talk services, a desired transmission of data messages or voice messages to other communication terminals of the group is often indicated by pressing a key; this is referred to as a transmission request. This request and subsequently transmitted transmission permission messages make it possible to control message transmission rights. The control of the message senders often takes place automatically on the basis of the priorities assigned to the respective communication terminals or their users by the server controlling the message transmission (eg a push-to-talk server). This server ver¬ gives message transmission rights by sending broadcast permission messages to communication terminals.

Similar methods of message transmission within a group of communication terminals may also be used in telephone conferences. In the following, the method according to the invention is explained mainly using the example of the push-to-talk service. The explanations also apply analogously to IP-based conference services or other message transmission services running within closed user groups. The push-to-talk service, IP conferencing services, and other messaging services within a group of communication terminals use the IP protocol for data transport (IP transport services). Thus, the transmission of messages within a group is independent of a particular mobile radio system or of a specific transmission system; In the case of message transmission within the group, different IP transmission systems can also be used in parallel. For example, z. For example, public mobile radio communication networks, private mobile communication networks and / or one or more wireless local area networks can be used in parallel. This results in a high flexibility. In sparsely populated areas, for example, IP transport services of a public communication network can be used, while in urban areas, due to the higher communication volume, advantageously a private network can be used. Wireless local area networks (WLANs) can preferably be used in buildings or on limited sites as an IP transport service ge.

An essential aspect of the method described is that, in the case of message transmission within a group of communication terminals, messages are transmitted by means of a broadcast or multicast transmission service. As such a broadcast or multicast transmission service, for example, the MBMS service (Multimedia Broadcast / Multicast service, which is known as such from the publication "3GPP TS 23.246 V.6.3.0 (2004-06), Technical

Specification, - 3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; Multimedia Broadcast / Multicast Service (MBMS); Architecture and Functional description "), the" 3GPP2 Broadcast / Multicast Service "service. vice (BCMS) ", the IP multicast service of a WLAN, an IP Multicast service in the fixed network or also the IP transport service of a trunked radio system (eg TETRA or TETRAPOL).

A server controlling the message transmission between the communication terminal devices of the group (for example a PTT server) assigns an IP multicast address to the plurality of communication terminals of a group, for example, if a predetermined spatial area of the mobile radio network has a fixed one Number (limit number) of group members (ie of communication terminals of the group) is exceeded. If the configured number (limit number) is not reached, the communication end rate of the group is assigned an IP unicast address. Alternatively, for a predetermined spatial area, the information may be available that each communication terminal located in this area (irrespective of the number of communication terminal stations located in this area) has an IP unicast address or (all together) an IP address. Assigned to the multicast address. Alternatively, it may also be stipulated that communication terminals of specific groups are always assigned an IP unicast address or always an IP multicast address in common. In a further alternative sequence, the server controlling the message transmission (for example the push-to-talk server) can decide on the basis of the IP transmission system currently being used by the communication terminal whether the communication terminal has an IP multicast address or an IP Unicnic address.

Information about the current location of a communication terminal can either be provided by the communication terminal itself or by the IP transmission used in each case. System to be sent to the PTT server. Due to the mobility of the communication terminals, the number of communication terminals of the group members in the individual predetermined spatial areas may change. The PTT server can then change the transmission mode from multicast transmission to unicast transmission or vice versa for each communication terminal.

Usually already before the beginning of the message transmission, communication users or their communication terminals register with a group or are assigned to this group as members. It is therefore a predefined or preselected group for which an assignment of the group members to the group is necessary before the beginning of the message transmission. After registration or

By assigning receive the communication terminals from the PTT Ser¬ ver the necessary communication parameters of the group über¬ mitted. These communication parameters also include the above-mentioned IP unicast addresses or the IP multicast addresses which are assigned to the communication terminals. Based on available information (eg location information of the communication terminals), the PTT server decides whether the respective terminals are assigned an IP unicast address or an IP multicast address. Some communication terminals of the group can IP unicast adres sen, other communication terminals of the group can get assigned an IP multicast address. When logging on to the group, the communication terminals can also be assigned keys for the encryption and decryption of messages for realizing an encrypted message transmission. A method for message transmission within a group of communication terminals may, for example, proceed as follows:

The server controlling the message transmission (for example a push-to-talk server, an IMS conference server or another control computer) receives from the communication terminals of the group or from the IP used for the respective message transmission. Transmission system information on the current whereabouts of the communication terminals of the group. Based on this information, the

Server, the number of in a predetermined spatial area (for example, in a radio cell of Mobilfunk¬ network) located communication terminals of the group er¬ average. The server compares this determined number with 5 of a preselected limit number. If the number of communication terminals located in the predetermined spatial area is smaller than the preselected limit number, then the server assigns its own IP 0 unicast address to the communication terminals of the group located in the area. As soon as a message is to be sent to the communication terminals, this message is addressed in each case with the IP unicast address of the respective communication terminal and transmitted to the respective communication terminal via a message transmission channel assigned exclusively to the respective communication terminal (unicast message transmission). , The Adressie¬ tion of the message and the transmission of the message to the respective communication terminals is vor¬ taken by the server, the message is then by means of a Unicast transmission service to the appropriate Kommunika '. transmission terminals. If, in comparing the number of communication terminals located in the spatial area with the preselected limit number, the server determines that the number is greater than the limit number, then the (group) communication terminals of the group in the area are IP multicast address assigned. The server addresses the message with this IP multicast address and sends the message to the majority of Kommunikationsend¬ devices. Subsequently, the message is simultaneously transmitted to the plurality of communication terminals by the broadcast or multicast transmission service.

As a server controlling the message transmission, for example, a push-to-talk server, an IMS conference server or another control computer can be used. The transmission of the message addressed with the IP multicast address to the plurality of communication terminals can take place via a trunking system (such as TETRA or TetraPol). The message can also be transmitted, for example via a wireless local area network (WLAN) to the plurality of communication terminals.

Alternatively, the message addressed with the IP multicast address can also be transmitted from one communication terminal of the group directly to another or several other communication terminals of the plurality of communication terminals. For example, the so-called WLAN ad hoc mode of a wireless local area network can be used for this direct message transmission. Alternatively, a direct (direct) transmission mode of a fringe radio system can also be used for the direct transmission of messages. In an alternative embodiment of the method according to the invention can also be dispensed with the above-described determination of the number of located in a predetermined spatial area of a mobile network communication terminal, instead can for predetermined raumli¬ che areas of the MobiIfunknetzes (regardless of the number of themselves in these areas Each of the communication terminals located in this area can be preset as to whether an IP unicast address or an IP multicast address is assigned to a communication terminal located in this area, if required. This fixed specification or information can be stored, for example, in the server controlling the message transmission. As a result, the decision considerably simplifies whether a unicast message transmission or a multicast or broadcast message transmission is to be carried out.

If a communication terminal of a group wants to send a message to the communication terminals of the group, then it reports this intention to transmit to the message transmission controlling server (ie, for example, to the PTT server or to the IMS conference server). The server controls the message transmission u. a. in that it registers the send requests, and (possibly after evaluation of priorities of the individual communication terminals or their users stored in it) transmits successive send permission messages to the communication terminals. Even before sending a transmission permission message to a specific communication terminal from the server an information message to this communication terminal of

Group transmitted. This ^<■ is this Kommunikationsendge¬ advises informed that the server has er¬ keep the request. In addition, the server may announce that the communication terminal shortly (in real time, namely, as soon as the time before him sending messages Kommunikations¬ terminals have ended their news broadcasting activity) a transmission permission message for sending his message to the other communication terminals of the group is obtained.

Thereupon, transmission resources of the mobile communication network for sending the message are served by this communication terminal even before receiving the transmission permission message. As soon as this communication terminal receives the transmission permission message, it can immediately start sending the message without any delay.

The messages transmitted by the server controlling the message transmission to the communication terminal of the group can be transmitted in encrypted form; they can be encrypted using an encryption method that is hierarchically located within or above the IP protocol level of the protocol stack.

Especially with a small number of available IP

Multipurpose addresses and a comparatively large number of groups of communication terminals, the following embodiment of the method according to the invention can be used: The server controlling the message transmission requests an IP address from an IP address management device.

Multi-address for a group of Kommunikationsendgerä¬ th. This IP multicast address is then transmitted from the IP address management device to the server controlling the message transmission. The server controlling the message transmission assigns to the majority of com-

- Communication devices of the group to the IP multicast address. After the one or more messages addressed with this IP multicast address are sent to the majority of the communication tion of the group has been transmitted, ie, when the communication is terminated within this group, the server in¬ formed the IP address management device on an end of the use of the IP MuIticast address. The IP address manager can then provide the IP multicast address for other groups of communication terminals for further message transmissions.

According to the invention, the WLAN ad-hoc mode can be used to enable direct (i.e., immediate) communication of the devices within a group without a network infrastructure. This can e.g. be used if the network infrastructure has failed or if there is no radio coverage. In this case, the terminal devices send their voice sequences or their data directly by means of multicast data transmission, which all terminals of the plurality of the same group can receive within the radio range of the respective transmitting terminal. Alternatively, the direct (direct) communication between terminals of the trunked radio systems can be used. These are opposite

WLAN the advantage of greater range and a reservier¬ th frequency range, ie there are exclusive transmission resources. Repeaters can be used to increase the range in the direct communication of terminals of the trunked radio systems. For the purpose of direct communication, the mobile communication terminals, for example, change from the WLAN infrastructure (or the GSM / UMTS infrastructure) to the WLAN adhoc mode. Or (if a trunking system is used as an IP transmission system), the mobile communication terminals change to its direct transmission mode, which allows communication without a network infrastructure. The mobile communication terminals preferably continue to use the IP multicast addresses that are used when logging on assigned to the PTT server for the group (s). In comparison with the infrastructure mode, the mobile communication terminals ME in adhoc mode or in direct mode also send their PTT data messages to this IP multicast address (s) and not only receive from this IP multicast Address (s). If the PTT server decides to allocate IP unicast addresses for data reception when logging on mobile communication terminals ME, multicast addresses can also be assigned as an alternative.

In another embodiment, the IP multicast address (s), WLAN or trunked radio channel numbers and other transmission parameters as well as the keys for encryption are preconfigured on the mobile communication terminals ME for each group, whereby group communication is also preconfigured contact with or without prior registration with the PTT server is possible. The communication terminals then agree with each other, which group or configuration should be used for the communication. Alternatively, the mobile communication terminals ME lead searches to predetermined

Channels to find communication messages from their group.

If the network infrastructure structure does not exist or does not function, the PTT server controls the transmission permission. The mobile communication terminals ME do this themselves. There are various possibilities for this:

1. The mobile communication terminals ME send messages when their user requests it (eg by pressing a button); the users recognize (hear) when other users speak and coordinate with each other. 2. Send the mobile communication terminals ME if their user requests it; However, they do not send if data is already being sent with the multicast address, or if the corresponding WLAN or trunked radio channel is busy.

3. The mobile communication terminals ME send transmission requests in the multicast channel to all other mobile communication terminals ME; Each mobile communication terminal ME creates and stores a list of transmission requests and waits until it is its turn. The position in the list can be influenced by specifying the priority of the mobile communication terminal ME or of the user in the transmission request.

The use of mechanisms for resource control is intended to prevent the reuse of unused resources, especially when communicating towards the PTT server. On the other hand, resources should already be reserved if the transmission permission is issued in order to avoid start delays when sending the group members. If many mobile communication terminals ME are in a radio cell or a predetermined spatial area, then the resources are often not sufficient to constantly allocate the resources required for transmission to all mobile communication terminals ME during a session. In order to avoid permanent reservation of resources, the PTT server can already indicate in the transmission permission, which typically indicates to all the communication terminals ME and FE the current transmitter, which the communication terminals ME and FE have the reservation of Resources already allowed before the transmission permission and thus avoids a start delay. This display of the next sender can also take place in a separate message (eg a status message) in order to chen communication terminals ME and FE to allow resource reservation, for example, have made their transmission request after sending the Sen¬ permission.

Furthermore, a communication terminal ME or FE can maintain its resource reservation even after the end of the sending of messages in order to quickly access e.g. to be able to respond to queries. A communication terminal ME or FE maintains the resource reservation for a configured or transmitted by the PTT server waiting time.

The above resource reservation or resource control mechanisms are equally suitable for unicast transmission and multicast transmission. For multicast reception, a mobile communication terminal must allocate and set up separately unicast resources for transmission. In the case of unicast reception, a mobile communication terminal without the intention of transmitting must only reserve and set up resources for receiving data. To send, this mobile communication terminal must modify the resource reservation and / or Ressourcenein¬ direction, so that resources are available for sending. After transmission, mobile communication terminals should release the transmission resources in both variants (unicast and multicast reception). The above described control of the reservation by waiting for

Sending or signaling from the PTT server is applicable for both variants.

The description of the method has hitherto essentially been provided for the use of a PTT service for group communication. Almost the same is the procedure when using IP ^: 'based conference services such as the 3GPP service "IMS Conference." Again, there are the variants of a conference On the one hand, the subscribers / group members register with the conference server (comparable to the PTT server) regardless of whether the conference is currently running or not. In the other variant, the conference server sets up a connection to all conference participants / group members when a participant starts the conference. Alternatively, the conference server can also establish the connection to the conference participants / group members in a time- or event-controlled manner. The control of the transmission / voice rights is analogous to the method described in connection with the PTT server: a mobile Kommuni¬ kationsendgerät sends a send request to the Konfe¬ renzserver, this tells all mobile Kommunikationsendgerä¬ th who has broadcast permission. Likewise, the resource control can be applied, ie it can be displayed who receives the transmission rights below.

A PTT service is often understood to mean only one voice service. However, other data such as video messages or short messages may also be transmitted. The use of IMS network components together with the IP transport services makes it possible to use such other IMS services. Such IMS services have traditionally been implemented as bilateral communications. It is also possible to connect to conventional telephones (fixed or mobile) via IMS gateways.

The communication within the groups is secured by encryption. This encryption takes place at or above the IP protocol level, which makes the protection independent of the respective IP transport network. The keys are assigned via known methods for key exchange or generation (eg a public key infrastructure). and uses unicast transmissions of the respectively used by the terminal ge IP transmission system. Alternatively, keys can also be entered manually or by means of data carriers (eg SIM card) in the terminals.

The separation of communication control and IP transmission system is an advantage of this group communication system. It enables the use of a wide variety of (and therefore also mobile) IP transmission systems. Specifically, this is the communication control based on IP unicast and IP multicast transmission systems. As a result, overall a more favorable cost structure and a higher flexibility can be achieved in comparison to the previous group communication systems with dedicated connections or dedicated transmission systems. Thus, e.g. a service without necessarily having to adapt the involved IP transmission systems. Or IP transmission systems can be added or exchanged without changing the communication control.

FIG. 1 shows various communication terminals, wherein a distinction is made between mobile communication devices ME such as mobile telephones, palmtops or portable computers with mobile radio interface and fixed communication terminals FE (FE = fixed equipment) such as For example, landline IP phones or workstation computers.

A first mobile communication terminal ME is connected to a private GSM / GPRS IP transmission system in the form of a GSM / GPRS mobile radio network, which uses a broadcast / multicast service center BMSC (BMSC = Broadcast / Multicast Service Center) to broadcast / multicast Service provides. The service center BMSC in turn is connected to a push-to-talk server (PTT server) and a group management server GLMS (GLMS = Group / List Management Server). A second mobile communication terminal ME is connected to a public UMTS IP transmission system in the form of a UMTS mobile radio network, which also provides a broadcast / multicast service with the aid of the broadcast / multicast service center. A third mobile communication terminal ME is also connected to the PTT server via a private WLAN IP transmission system (in the form of a wireless local area network). A fourth mobile communication terminal ME is connected via a private or public trunked radio IP transmission system (in the form of a trunked radio link) to the PTT server. A fixed communication terminal FE is connected to the PTT server via a fixed IP transmission system (eg in the form of the Internet). Furthermore, a group manager unit is connected to the PTT server and to the group management server GLMS. The mobile communication terminals ME, the fixed communication terminal FE and the group manager unit communicate with the PTT server via the various IP transmission systems.

The mobile terminals ME or their users are registered subscribers of the IP transmission systems or can use these on the basis of roaming contracts. The communication terminals initially register with the respective IP transmission system and then with the group communication system. The group communication system in the present case comprises the PTT server and the management server GLMS. In another example, the group communication system may also include the group manager unit, the PTT server, and / or a 3GPP IP multimedia subsystem. The registration can be an au- authentication and authorization. Authentication and authorization take place by means of the standard method provided for the respective IP transmission system or by means of the standard procedures as described in the specifications of the "3GPP IP Multimedia Subsystem" or in the guidelines of the Open Mobile Alliance (OMA ) are known.

After that, the mobile communication terminals ME and the stationary communication terminal FE register with the PTT server as a member of a group or as a member of several groups. If no 3GPP-IMS system or a corresponding system implemented according to OMA specifications is used, a direct log-on of the communication terminals including authentication and authorization at the PTT server can also take place without IMS or OMA procedures be used. In the latter case, the address of the PTT server is stored or configured in the communication terminals.

In the logon processes, terminal-specific keys and / or group-specific keys can be determined for the communication terminals and assigned to the communication terminals. The affiliation of the communication terminals to a group is stored on the management server GLMS and can be set up and / or modified there by the communication terminals or by the group manager unit.

The assignment of an IP multicast address (for example by the PTT server) causes a mobile communication terminal ME to log on to a multicast transmission service of the respective IP transmission system. If a WLAN or an IP landline network is used as the IP transmission system, then the mobile communication terminal ME carries out the procedure "IP multicast join." If the MBMS service of a mobile radio network (GSM / GPRS, UMTS or CDMA2000) is used, then the mobile communication terminal ME registers with the MBMS service which belongs to the assigned IP multicast address, whereby the service center BMSC checks whether the mobile communication terminal ME or its user is checking this multicast service The corresponding rights may be stored either in the service center BMSC, in a standalone database or in a stand-alone server (eg in an AAA server, AAA = authentication, authorization and accounting) and receive authorizations can also be stored in the management server GLMS, in which management servers the affiliations of the communications can also be stored be stored to the individual groups for the PTT service. Alternatively, there is no need to check the rights since the application often takes place via an already authorized unicast connection. Advantageously, the service center BMSC and the PTT server can be realized in one unit; This can be minimized by communication between the PTT server and service center BMSC delay times and a low communication effort can be achieved.

After successful registration of a mobile communication terminal ME or the fixed communication terminal FE in one of the multicast transmission services, the corresponding communication terminal is able to receive all voice messages (voice sequences) or data messages (Datense¬ sequences), which by means of this Multicast transmission service to the members of the corresponding group be transmitted. The actual control of the group communication (for example the registration of the individual terminals at the PTT server and the request for a transmission permission by the individual terminals) takes place independently of the use of the multicast transmission service via unicast transmission services. For example, voice sequences or data are transmitted via unicast transmission services to the PTT server. Control messages can preferably also be transmitted by means of multicast transmission services. Such a control message is, for example, the indication as to which communication terminal currently has a transmission permission.

2 shows a message flow of a so-called "pre-established PoC session" using a multicast transmission In such a "pre-establishment session", the communication terminals of the group report independently of a currently occurring group communication (session ) at the PTT server. In contrast to this, in the case of an "on-demand PoC session", the communication terminals of a group are only reported to the communication when a communication terminal of the group makes a send request.

Therefore, the time from a transmission request to be submitted later to the receipt of a transmission permission is shortened by the time duration of this application, if one compares the "Pre-Established PoC Session" with the "On Demand PoC Session". The shortening of the time of the "Pre-Established Session" compared to the "On-Demand Session", especially in the case of use by z. For example, police on-duty services are an important quality feature. preferably the "Pre-Established PoC Session" are used.

With reference to FIG. 2, a "Pre-Established PoC Session" is described below for the push-to-talk service, in which a transmitting communication terminal in a Wireless Local Area Network both transmits and receives using a unicast transmission service ,

A first mobile communication terminal MEA assigned to a first communication user (user) is switched on (box "switching on") and logs on to the associated IP transmission system (in the exemplary embodiment in the case of a wireless local area network WLAN) (box "). Registration on the transmission system "). A second mobile communication terminal MEB assigned to a second communication subscriber is likewise switched on and registers with the associated IP transmission system (in the exemplary embodiment for a mobile radio network in accordance with the GSM / UMTS standard). Then the following process steps take place:

Arrows 1:

The first mobile telecommunication terminal MEA and the second mobile telecommunication terminal MEB log on to the PTT server as subscribers of the same group. The PTT server then checks the group membership by means of a query in the group management server GLMS (not shown in Figure 2, see Figure 1). If the result of the check is positive, the PTT server confirms the registration to the mobile communication terminals MEA and MEB and delivers the parameters required for the respective IP transmission systems to the mobile communication terminals MEA and MEB. As such a parameter, the mobile commu- nation terminal MEA an IP unicast address for sending data to the PTT server and for receiving data from the PTT server. As such a parameter, the second mobile communication terminal MEB receives one or more IP unicast addresses for sending data to the PTT server and one or more IP muIticast addresses for receiving data from the PTT server. The logon process takes place by means of the SIP message "INVITE", the transmission of the unicast addresses or the multicast addresses, for example, by means of the SIP message "200OK" or by means of a stand-alone message.

Arrows 2:

The mobile communication terminal MEB activates those MBMS transmission services in the IP transmission system GSM / UMTS assigned to it, which belong to the IP multicast address assigned to it. The mobile communication terminal MEB is then ready to receive messages originating from the PTT server. The service center BMSC checks in the MBMS activation the rights of use of the respective MBMS transmission services by means of a query of the management server GLMS (not shown in Figure 2).

Arrow 3: The mobile communication terminal MEA requests a transmission permission from the PTT server. If the mobile communication terminal uses a reservation of transmission resources ("resource reservation"), then it is already requesting corresponding transmission resources for the transmission of its data to the PTT server.

Arrows 4: The PTT server sends a control message to the service center BMSC in order to initiate the functions provided for the MBMS transmission services for activating transmission resources (alternatively, the receipt of the message sent to the terminals at the service center BMSC may also include these MBMS Activate functions). The activation by means of a separate control message results in a lower time delay than in resource activation by the receipt of the message to the terminals.

Arrows 5:

The mobile communication terminal MEA receives a transmission permission message from the PTT server. At the same time, information (transmission status) is sent via this transmission permission via the service center BMSC and via the mobile radio network GSM / UMTS to the second mobile communication terminal MEB.

Arrows 6:

The mobile communication terminal MEA sends data in the form of messages (in the example a voice sequence message) to the PTT server. The PTT server forwards this data to the service center BMSC; the service center BMSC sends the data via the MBMS transmission service on to the receiving mobile communication terminals of the group (of which only the second mobile communication terminal MEB is shown in the exemplary embodiment).

Arrow 7:

The mobile communication terminal MEA reports the end of the data message transmission to the PTT server.

Step 8: The PTT server waits for a predetermined period of time for further transmission requests of the first mobile communication terminal MEA or other communication terminals of the group. This avoids time-consuming and possibly even data loss-related setup and disassembly of the transmission resources. The mobile communication terminal MEA also waits a predetermined period of time before a resource is released, provided that it uses a "resource reservation" in WLAN. (Alternatively, the PTT server controls the resource reservation of the communication terminals ME or FE as described in connection with FIG For example, it can be established that all mobile communication terminals ME listed in the control message establish or maintain the resource reservation.)

Arrow 9:

The PTT server sends a message for releasing the transmission resources to the service center BMSC. This then executes the corresponding functions, the transmission resources are released.

FIG. 3 shows a push-to-talk service with a "pre-established PoC session", in which a transmitting communication terminal MEB receives messages using a GSM / UMTS mobile radio network by means of a multicast transmission service and by means of a unicast Broadcasting service sends messages.

The mobile communication terminals MEA and MEB are analogous to the process illustrated by Figure 2 already registered with the PTT server as a participant of the group. Corresponding MBMS transmission services of the mobile network GSM / UMTS are likewise already activated for the second mobile communication terminal MEB. The corresponding method steps "switch on", "log on to the transmission system", arrows 1 and arrows 2 of FIG. 2 are not shown again in FIG.

Arrow 33:

The second mobile communication terminal MEB sends a send request message to the PTT server.

Arrow 34:

The second mobile communication terminal MEB sets up one or more unicast transmission services (eg several unicast transmission services for several different data components) in the IP transmission system GSM / UMTS in order to transmit PTT data messages to the PTT server to send. For sending voice data messages, these unicast transmission services usually have a real-time characteristic, which requires resource reservation. This resource reservation is only performed when needed, ie. H. only if data is to be sent to the communication terminals of the group (in the case of communication terminals without multicast data transmission, resource reservation is also used when receiving data). Alternatively, the PTT server controls when the second mobile communication terminal MEB sets up unicast transmission services and thus resers resources. This happens e.g. with a separate status message, which also confirms the receipt of the send request message.

Arrows 35:

The PTT server sends one or more initiation or

Check messages to the BMSC service center for the MBMS specified functions for activating transmission resources to initiate. In the example given, the second mobile communication terminal MEB is also the recipient of the MBMS transmission services. The PTT service usually works half duplex, ie you can not send and receive on the same side. This prevents the transmission of the speech sequences from being disturbed by its own possibly delayed speech sequences.

Arrows 36:

The second mobile communication terminal MEB receives the transmission permission message from the PTT server. Information about this (the so-called send status) is also sent by the PTT server to the first mobile communication terminal MEA.

Arrows 37:

The second mobile communication terminal MEB sends a data message (eg a voice sequence) to the PTT server. The PTT server sends this data to the BMSC service center; the service center BMSC sends the data via the MBMS transmission services of the mobile radio network GSM / UMTS to the other receiving communication terminals of the group (in the exemplary embodiment, these are the communication terminals MEC, MED, etc.). The PTT server also sends the data to the mobile communication terminals that can be reached via unicast transmission services (in this embodiment, for example, to the first mobile communication terminal MEA).

Arrow 38: The second mobile communication terminal MEB notifies the PTT

Server the end of its data transfer.

Step 39: The PTT server as well as the second mobile communication terminal MEB (which in the exemplary embodiment represents the transmitting communication terminal) wait for a predetermined time for further transmission requests in order to avoid an unnecessary, expensive and potentially associated with data loss on and Ab construction of the transmission resources. The waiting times of the second mobile communication terminal MEB and the PTT server can be of different lengths. (Alternatively, the PTT server controls resource reservation of the communication terminals as described above in connection with FIG.

Arrows 40:

The PTT server sends a control message for releasing the transmission resources to the BMSC service center, which then performs the corresponding functions. The mobile communication terminal MEB then reduces the unicast transmission service; the unicast transmission service is terminated.

Used abbreviations:

PTT push to talk

POC push-to-talk over cellular

GLMS Group / List Management Server BMSC Broadcast / Multicast Service Center

GSM Global System for Mobile Communications

GPRS General Packet Radio Service

UMTS Universal Mobile Telecommunications System

WLAN Wireless Local Area Network ME Mobile Equipment

MBMS multimedia broadcast / multicast service

FE Fixed Equipment

3GPP Third Generation Partnership Project

OMA Open Mobile Alliance IMS IP Multimedia Subsystem

IP Internet Protocol

Claims

claims

A method of messaging within a group of communication terminals (ME, MEA, MEB, MEC, MED), wherein in the method

- a plurality of communication terminals (MEB, MEC, MED) of the group is assigned an IP multicast address, and

- a message addressed with this IP multicast address is simultaneously transmitted to the plurality of communication terminals by means of a broadcast or multicast transmission service of a mobile communication network (arrows 37).

2. The method according to claim 1, characterized in that

from a server controlling the message transmission

(PTT server) is assigned the IP multicast address of the plurality of communication terminals (arrows 1).

3. The method according to claim 1 or 2, characterized in that

- By a server controlling the message transmission (PTT server) the addressed with the IP multicast address message is sent to the plurality of communication terminals.

4. The method according to claim 2 or 3, characterized in that

- When the server is a push-to-talk server (PTT server) is used.

5. The method according to claim 2 or 3, characterized in that - Server is an IMS conference server.

6. The method according to any one of the preceding claims, characterized in that - the message addressed with the IP multicast address message is transmitted by means of a trunked radio system to the plurality of Kommuni¬ kationsendgeräten.

7. The method according to any one of the preceding claims, characterized in that

- The message addressed with the IP multicast address message is transmitted by means of a wireless local area network (WLAN) to the plurality of communication terminals.

8. The method according to claim 1, characterized in that

- The addressed with the IP multicast address message is transmitted from a communication terminal of the group directly to the plurality of communication terminals.

9. The method according to claim 8, characterized in that

the message addressed with the IP multicast address is transmitted using a direct transmission mode of a trunked radio method.

10. The method according to claim 8, characterized in that

the message addressed with the IP multicast address is transmitted using an ad hoc transmission mode of a wireless local area network data transmission method.

11. The method according to any one of the preceding claims, characterized in that

the number of communication terminals of the group located in a predetermined spatial area of a mobile radio network is determined, and if a preselected limit number is undershot, an IP unicast address is assigned to each of the communication terminals located in the area one of these IP unicast addresses addressed message is transmitted via a dedicated only the respective communication terminal message transmission channel to the respective communication terminal, or

if the preselected limit number of the plurality of communication terminals in the area is exceeded, the IP multicast address is assigned and the message addressed with this IP multicast address is simultaneously sent to the plurality of communication terminals by means of the broadcasting system. or multicast transmission service of the mobile communication network.

12. The method according to any one of claims 1 to 10, characterized in that

is predetermined for a predetermined spatial area of a Mobilfunknet¬ zes regardless of the number of be¬ in this area be¬ finding communication terminals of the group, ^' whether a befindliches in this area Kommunikationsend¬ device an IP unicast address or IP multicast Address is assigned.

13. The method according to any one of claims 2 to 12, characterized in that

an information message is transmitted from the server to first communication terminals of the group, whereby these first communication terminals inform about this be received that a transmission permission message for sending a message to the other Kommunikationsend¬ devices of the group are obtained, and

- are then reserved by these first communication terminals before receiving the transmission permission message Übertragungs¬ resources for sending the message.

14. The method according to any one of claims 2 to 13, characterized in that - the messages transmitted by the server to a communication terminal of the group are encrypted by means of an encryption method acting within or above the IP protocol level.

15. The method according to any one of claims 2 to 14, characterized in that

an IP multicast address for the group of communication terminals is requested by the server from an IP address management device, the plurality of communication terminals of the group is assigned this IP multicast address, and

the IP address management device is informed by the server about an end of the use of the IP multicast address, whereupon the IP multicast address can be called up for further message transmissions of other groups.