FR2709908A1 - Telecommunication system for the dissemination of information and group communications. - Google Patents

Abstract

A telecommunications system includes at least one base station (18, 19, 20, 21) and a plurality of remote units (22-26), each having an identification. The remote units can be arranged in at least one group and are designed to communicate with the base station over a radio link. A group service center, or GSC, (12) receives traffic from an incoming channel of the radio link and reproduces it in an outgoing channel of the radio link. Remote units have a means of communicating their identification to the GSC. In the GSC, a search means correlates the identification of the remote unit with the identifications of other remote units of a common group and a means establishes respectively distinct links with said other remote units using the identification of these remote units.

Description

The present invention relates to an information dissemination system

  and group communication in a compressed telecommunications system

  with at least one base station and several remote units, o the remote units have distinct identifications, as is the case for example in point-to-point communications, that is to say peer-to-peer, especially in radio -

GSM cell phone.

  It has been proposed to use GSM cellular radiotelephone techniques (Special Mobile Group) in distribution type systems for private mobile radio service (PMR) made available to railway agents, o

  peer-to-peer communications and group communications are required.

  In the field of cellular radiotelephony, it has been proposed to provide a conference service center enabling conference calls to be established in which a certain number of peer-to-peer communications are established simultaneously on an appropriate basis and each time slot d '' an incoming channel is connected to each outgoing time slot in the center of

conference service.

  In the article "Group Calls in GSM", ETSI SMG-UIC Task Force, February 1993, it was suggested that such a conference center could be

  used to manage group calls in a PMR system.

  It remains to solve the problem of the spectrally efficient management of such an assembly, which must be able to be managed without undue delays at each stage.

  of the procedure, so that such a system is accepted on the commercial market.

  According to a first aspect of the invention, there is provided a telecommunications system comprising at least one base station and several remote units. Each remote unit has an identification. The remote units can be arranged in at least one group and are designed to communicate with the base station via a radio link. A group service center (GSC) is proposed, which includes means for receiving traffic from an incoming channel of the radio link and for reproducing it in an outgoing channel via the radio link. At least one remote unit is provided which includes means for

  communicate their identification to the GSC and establish a telecommunication link

  cations with the GSC. The invention is distinguished in that: the GSC comprises a search means making it possible to correlate the identification of said remote unit with the identifications of other units distant from a common group and a means making it possible to establish telecommunications links with said other units

  using the identifications of these remote units.

  Thus, since intelligence has been added to it, the GSC becomes more than a simple conference-type means of connection and actively establishes group communications. The GSC can establish group communication based on prior knowledge of the group to which given remote units belong, or, when a remote unit belongs to more than one group, the GSC simply needs to be informed of the identification of the group to which

  the remote unit requests to be connected.

  According to a second aspect of the invention, a telecommunications system is proposed which comprises at least one base station and several remote units, each remote unit having an identification, the remote units being able to be arranged in at least one group and being designed for communicating with the base station over a time division multiple access (TDMA) type radio link which includes entry time slots and exit time slots, means for establishing a group of units remote, assign a control channel to each remote unit in the group, and reserve a traffic channel for the group, means for periodically transmitting remote unit control information to each remote unit of the group while the group is established, a means placed in a remote unit and used to introduce a request for transmission, and a means placed in the remote unit and used to provide transmission access, for the remote unit of the group, to the reserved traffic channel as soon as a transmission request is made in this remote unit and to transmit on the channel of reserved traffic with emissions that are adjusted based on unit control information

  remote when said transmit access is provided.

  In this way, the transmission parameters, such as the synchronization advance and the power level, are established and, as soon as the

  conversation button (FI), you can have immediate access to the channel.

  The following description, intended to illustrate the invention, aims

  to allow a better understanding of its characteristics and advantages; it is based on the appended drawings, among which: FIG. 1 is a functional diagram of a private mobile radio system (PMR) according to the invention; Figure 2 is a block diagram of the group service center of Figure 1; Figure 3 is a flowchart showing the steps involved in establishing a group call in the system of Figure 1; and Figure 4 is a flowchart showing the operation of the

  system following the steps shown in Figure 3.

  Dictionary of acronyms BS Base station BSC Base station control device BTS Basic transceiver station GSC Group service center GSC Group service control device GSM Special Group Mobile ISDN Integrated services digital network MS Mobile station MSC PSTN Mobile Communication Center Public Switched Telephone Network FIT SDCCH Conversation Button Autonomous Specialized Control Channel TCH TDMA Traffic Channel Time Division Multiple Access In Figure 1, the relationship between the GSC and the network is shown. In

  a GSM network, mobiles 22 to 26 are connected by telecommunication channels

  radio communications to BTS 18 to 21. Each BTS 18 to 21 contains the components

  system radio and modules that interface with a BSC 15 to 17.

  A BTS 18 to 21 is connected by means of terrestrial links with its BSC 15 to 17. A BSC (for example the BSC 15) manages a group of BTS (for example the BTS 18 and 19) and plays the role of an interface digital processing between them and the MSCs 13 and 14 in order to carry out the communication processing as defined by the GSM. A BSC 15 to 17 is connected by means of terrestrial links to an MSC 13, 14. The MSC 13 and 14 are telephone exchanges. Each MSC 13, 14 provides mobile services placed inside its coverage area. It also provides interfaces with a PSTN 10 network or an ISDN 11 network and

  with land circuits from BSC 15 to 17.

  An MS 22 is presented, which has a FIT 30 button that acts as a transmitter activation key. All other MS have a

PFIT button.

  The GSC is connected to the MSC. The GSC manages the commu-

  group communications and information communications using a conference facility or multiplexers, the number of the latter being between one and a large number. The GSC can be placed inside the MSC or else a separate piece of equipment which is

  connected to the MSC using terrestrial links.

  Figure 2 shows a block diagram of the GSC. This consists of a GSC control device 100, an MSC interface 101, a group database 102 and a conference type or multiplexer link device, in number between one and a large number, 103. The GSC control device 100 controls the group database, manages the interface with the MSC via the MSC interface 101, and controls the conference type connection device, or the multiplexer, 103. The group database 102 contains all the information concerning the members of the

  group and their group communication and information dissemination privileges

  tions. The conference type link device or the multiplexer 103 connects two or more audio traffic channels and allows: (1) the establishment of conference links between these traffic channels (by allowing all parties to speak at the same time time to all other conference members); and (2) the oral dissemination of information from the initial TCH user to all members of the group. The

  device 100 GSC control indicates to the connection device of the confere type

  rence or multiplexer 103 who are the group members, as well as the type

Communication.

  The group database 102 is maintained from a control terminal 105. According to a variant, a mobile station user can create, modify and delete information and group communication communications groups. Different levels of access can be given to different types of users. The GSC 12 manages information or group broadcasting communications and monitors the connection status of each mobile station. This allows the service center to indicate whether a communication is successful or not. If all parties are connected to the conference, the service center can inject (or interrupt) a warning tone in the voice signal path. The tone can be sent to the person initiating the conference or to all participants in the conference. The service center decides whether the parties called can answer (group communication) or cannot answer (information broadcast communication). The protocol is optimized for information dissemination communication or for group communication, and communication management can be very fast (between 1 and 2 establishments

communication standards).

  This solution offers a very high level of service and management of

  communications, which can be compared to a complete installation for conference

  rence. It is notably more spectrally efficient than the solution

  consisting in assigning a TCH to each participant in the group communication.

  The SDCCH solution allows a constant signaling connection between the GSC and each participant in the group communication. Group management is therefore easier. It is not necessary to establish signaling links each time a mobile station changes state, for example due to transfer to a

  new cell, entering a new group, or leaving a group.

  In addition, during group communication, data can be transmitted to individual mobile stations as well as to an entire group. Specific mobile stations can be removed from the conference to answer

  higher priority communications.

  Each SDCCH carries a quarter of the data rate of a TCH. The load, expressed in terms of spectrum, resulting from the permanent use of an SDCCH for each mobile station in the group can be reduced by using a speed channel of 1/8 or 1/6, i.e. -to say that each SDCCH time slot has a duration equal to 1/8 or 1/6 of a traffic channel time slot. Figures 3 and 4 show a flow diagram showing how the SDCCH can be used to control access to a group broadcast channel. Initially, group communication is established for a

  group A (step 200). The GSC control device gives access to identifiers

  cations of the group's MS in the group database (step 201). The GSC starts the connection of each element of the group (step 202). When the

  first element of the group called responds, it is assigned a SDCCH.

  Authentication and encryption are performed (step 203), and the new member is added to the group (step 204). The MSC then reserves an information dissemination TCH (step 205). The group call is then established and the system waits for the PIT button to be pressed (step 206). If additional group members respond later, they are added to the group in the same way (step 207). Additional channels of information dissemination traffic are added in necessary number, since the mobile stations can be in different cells and paging groups. All the mobile stations in the group can then listen to the downlink information channel. At the same time, the timing advance and the power adjustment are adjusted using the SDCCH

(step 208).

  If the FIT button is pressed (Figure 4), the FIT instruction is sent to the MSC (step 257). The MSC assigns the uplink TCH to the MS (step 258). The MS then switches from SDCCH to TCH and the conversation begins (step 259). The conversation is reproduced in the GSC and is inserted into the outgoing TCH (step 260). The MSC prevents other mobile stations from having access to the uplink TCH (step 261). When the FIT button on the MS is released, the uplink TCH is released, the information broadcast

  stops, and the mobile unit returns to the SDCCH (step 262).

  Of course, those skilled in the art will be able to imagine, from the

  telecommunications system whose description has just been given as

  merely illustrative and in no way limitative, various variants and modifications do not

  outside the scope of the invention.

Claims (4)

  1. Telecommunications system comprising at least one base station (18 to 21), several remote units (22 to 26), each remote unit having an identification, the remote units being able to be arranged in at least one group and being designed to communicate with the base station on a radio link, and a group service center, denoted GSC, (12) comprising means intended to receive traffic from an incoming channel of the radio link and to reproduce it in a outgoing channel of the radio link,   at least one remote unit comprising means for communicating   to identify its identification to the GSC and to establish a telecommunications link with the GSC, characterized in that: the GSC comprises a search means (102) serving to correlate the identification of the remote unit with the identifications of other remote units   of a common group and a means used to establish, one by one, tele-   communications with said other remote units using identifications of these distant units.   2. Telecommunications system, characterized in that it comprises at least one base station (18 to 21) and several remote units (22 to 26), each remote unit having an identification, the remote units being able to be arranged in at least a group and being designed to communicate with the base station over a time division multiple access (TDMA) radio link, comprising entry time slots and exit time slots, means (12, 13 , 14) used to establish a group of remote units, to assign a control channel to each remote unit in the group, and to reserve a traffic channel for the group; means (208) for periodically transmitting remote unit control information to each remote unit in the group while the group is established, means (30) located in a remote unit and for initiating a request for transmission (PIT), and means (259) placed in the remote unit and serving to give transmission access, for the remote unit of the group, to the reserved traffic channel when introducing a send request to this remote unit and to send on the reserved traffic channel with transmissions which have been adjusted according to the remote unit control information when said transmit access has been given. 3. Telecommunication system according to claim 2, characterized in that the control information transmitted is synchronization advance information and the means placed in the remote unit are designed to   adjust the synchronization of the input time slots.   4. Telecommunication system according to claim 2, characterized in that the control information transmitted is output power information and the means placed in the remote unit are designed to   adjust the output power of the transmissions from the remote unit.