GB2376382A

GB2376382A - Transmission of SMS cell broadcast messages

Info

Publication number: GB2376382A
Application number: GB0114022A
Authority: GB
Inventors: Per Johan Schultz; Hans Fredrik Svensson; John Gunnar Olsson
Original assignee: Telefonaktiebolaget LM Ericsson AB
Current assignee: Telefonaktiebolaget LM Ericsson AB
Priority date: 2001-06-08
Filing date: 2001-06-08
Publication date: 2002-12-11
Also published as: AU2002348772A1; WO2002102099A3; WO2002102099A2; GB0114022D0

Abstract

A cellular radio communications network uses multicast messages for transmitting SMS cell broadcast messages over the network. Thus, a single multicast message is sent from a base station controller 4 to a group of addressed base stations 2, which respond by transmitting SMS cell broadcast messages over the air interface. The multicast group for receiving page requests may include all base stations, in which case the base stations must be capable of determining whether they are specifically addressed, and should respond by transmitting a SMS cell broadcast message.

Description

COMMUNICATIONS SYSTEM TECHNICAL FIELD OF THE INVENTION This invention relates to a mobile communications system, and in particular to the sending of SMS cell broadcast messages in such a system.

BACKGROUND OF THE INVENTION Conventional mobile telephony systems allow the use of SMS Cell Broadcast (SMS-CB) to send unacknowledged short messages of a general nature to suitably designed mobile stations within a given geographical area, known as a cell broadcast area.

Cell broadcast areas may comprise one or more cells, or may comprise the entire network coverage area.

SMS cell broadcast messages may for example relate to weather or traffic information, or other information of general interest.

In the GSM system, the SMS cell broadcast service is defined in GSM TS 03.41 version 5.3. 0.

As defined in this specification document, SMS cell broadcast messages originate in cell broadcast entities (CBEs), which are connected to a cell broadcast centre (CBC).

A cell broadcast centre may be connected to several base station controllers (B8Cs), and each base station controller may be connected to several base transceiver stations (BT8s).

Individual cell broadcast SMS (CBS) messages are assigned their own geographical coverage areas, and are sent from the cell broadcast centre via the base station controllers, using unicast, to the base transceiver stations which are required to provide the appropriate geographical coverage.

The received messages are then broadcast by the base transceiver stations, and can be received by any suitable mobile stations within the coverage areas of

those base transceiver stations.

Thus, each cell broadcast SMS message can require the transmission of many messages from the base station controller. In the case of a network topology which is based on the internet protocol (IP), all messages which share a common path are competing for the available bandwidth. Thus, at the base station controller, for example, the transmission of many SMS cell broadcast messages reduces the bandwidth which is available for other types of message.

SUMMARY OF THE INVENTION The present invention is concerned with reducing the bandwidth which is required to handle the SMS cell broadcast messages which are transmitted within a network.

In particular, the invention concerns the use of multicast messages to transmit SMS cell broadcast messages within the network. Thus, for example, a single multicast SMS cell broadcast message can be sent in respect of many unicast messages from the base station controller to the individual base stations, thereby reducing the bandwidth required to carry such messages.

Preferably, multicast groups, that is, groups of addressees that will respond to specific messages, are defined. Each message can then be addressed to an appropriate group. For example, a multicast group can be defined in respect of each cell in a location area, or each cell covered by a BSC.

BRIEF DESCRIPTION OF DRAWINGS Figure 1 shows a part of a cellular telephone network in accordance with the invention.

Figure 2 is a flow chart showing a first method in accordance with the invention.

Figure 3 is a flow chart showing a second method

in accordance with the invention.

Figure 4 is a flow chart showing a third method in accordance with the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Figure 1 is a schematic diagram of a part of a typical GSM cellular radiotelephone network infrastructure used for sending cell broadcast short message service messages in accordance with the invention.

As is conventional, the illustrated network includes a large number of cells, each containing a respective base transceiver station (BTS) 2, only some of which are shown in Figure 1. Each base transceiver station 2 has an antenna, for communication with any mobile stations (MSs) within the cell.

Each base transceiver station BTS has a respective landline connection to a base station controller (BSC) 4.

As defined in the GSM specification document, SMS cell broadcast messages originate in cell broadcast entities (CBEs) 6, which are connected to a cell broadcast centre (CBC) 8.

The cell broadcast centre 8 may be connected to several base station controllers (BSCs) 4.

In the preferred embodiment of the invention, the network is an internet protocol (IP) based transmission network, in which all messages, including payload and signalling messages, share the available bandwidth.

It will be appreciated that radio telecommunications networks can take many forms, and that the invention is applicable more widely than to the specific form of network illustrated in Figure 1.

In the preferred embodiment of the invention, the base station controllers 4 are responsible for sending the cell broadcast SMS messages to the base transceiver

stations 2 for broadcasting, although the cell broadcast centre 6 is responsible for the management of cell broadcast SMS messages.

For example, amongst the management functions which the cell broadcast centre 6 carries out, it allocates a serial number to each cell broadcast SMS message, and it determines the set of cells to which each message should be broadcast, indicating within the respective serial number the geographical scope of the message.

For example, the network can define a number of location areas, which are used in paging mobile stations. Each location area can cover the area served by multiple base transceiver stations.

It is also possible to set up other user defined cell groups, covering areas larger than the area served by a single base transceiver station.

When a newly configured base transceiver station is first connected to the network, it may form part of one or more location areas or other user defined cell groups.

The invention relies on the use of multicast messaging between the network and the base stations, to reduce the total number of messages being transmitted, for example through the base station controller. A multicast message is a message which is sent over a network to any desired number of receivers in the network. Each receiver can belong to one or more multicast groups, and the membership of the multicast groups can be assigned on configuration of the system, but can be altered dynamically.

In a preferred embodiment of the invention, there is one multicast group which includes every base transceiver station connected to a base station controller, a respective multicast group corresponding

to each of the defined location areas in the network, and a respective multicast group corresponding to each of the user defined cell groups.

Thus every cell is a member of the multicast group corresponding to its base station controller. Further, every cell in a location area or other user defined group is a member of the corresponding multicast group or groups.

As mentioned above, when a SMS cell broadcast message is to be sent, a determination is made as to the desired geographical extent of the SMS cell broadcast message.

As a result of this determination about the desired geographical extent of the SMS cell broadcast message, the message can be sent from the cell broadcast centre 8 to the desired base transceiver stations.

The base station controller 4 is provided with information to determine, based on the desired geographical extent of the message, which multicast groups must receive the message.

For example, if the message is to be sent to every base transceiver station which is connected to the base station controller, it is only necessary to send a single multicast SMS cell broadcast message to the multicast group which includes every base transceiver station. Alternatively, if the message is to be sent to every base transceiver station in a location area or other user defined group, it is only necessary to send a single multicast SMS cell broadcast message to the corresponding multicast group. In other cases, it may be necessary to send more than one multicast message, but the required number of messages will generally be small.

Thus, in this embodiment of the invention, the

number of messages which must be sent, and hence the occupied bandwidth, are minimised, although it is necessary that the base station controller has knowledge of the multicast groups.

Figure 2 is a flow chart showing the procedure carried out in the base station controller 4 in implementing this embodiment of the invention.

In step 21, the base station controller receives a SMS cell broadcast from the cell broadcast centre. The SMS cell broadcast indicates the set of cells to which the message should be broadcast. In step 22, the base station controller extracts this information relating to the required extent of the SMS cell broadcast message. In step 23, the base station controller determines the addresses of the multicast groups to which the message is to be sent, and, in step 24, it sends the SMS cell broadcast message.

Thus, where a message is to be sent to every cell in a multicast group, only one multicast message needs to be sent.

In an alternative preferred embodiment of the invention, there is defined a single multicast group for SMS cell broadcast purposes, and every base station belongs to that multicast group.

Figure 3 shows the simplified procedure carried out by the base station controller in that case. In step 31, the base station controller receives a SMS cell broadcast request from the cell broadcast centre.

As described above, all SMS cell broadcast messages are sent to the single multicast group which includes all base stations, so the base station controller only needs to know that one address, which it recalls in step 32, and, in step 33, it sends the SMS cell broadcast message.

Figure 4 is a flow chart showing the procedure

carried out by the base stations when the base station controller is carrying out the simplified procedure of Figure 3. Although the base station controller requires less knowledge, as described above, the base transceiver stations require more knowledge.

Specifically, each base transceiver station needs to know which user defined group, location area and BSC it belongs to, so that it knows which of the received SMS cell broadcast messages are addressed to it.

At step 41, the base station receives a new SMS cell broadcast message. At step 42 it determines whether it is in one of the cells to which the message is to be broadcast. If the answer is no, the procedure passes to step 43, and the message is discarded. If at step 42 it is determined that the cell is one to which the message is to be broadcast, the procedure passes to step 44, and the message is sent over the air interface to the active mobile stations in that cell at that time.

Thus, in this case, only one message still passes through the BSC, thereby freeing BSC resources for other purposes. However, the total number of SMS cell broadcast messages sent to the base transceiver stations is increased, because messages are sent unnecessarily to some base stations.

The procedures described above with reference to Figures 2 and 3 can also be implemented by base station controllers in a network in which not all base transceiver stations are capable of handling multicast messages. In that case, messages for base stations which cannot handle multicast operation must continue to be sent by the respective base station controllers as unicast messages. The BSC must therefore receive messages sent from the SMS cell broadcast centre, and determine the base stations to which it must send

unicast messages, as well as the multicast groups to which it must send multicast messages.

The invention has been described above with reference to its use in a GSM network, which is used primarily for voice calls. However, it will be apparent that the invention is equally applicable to any mobile communications network. For example, the invention is applicable to a General Packet Radio System (GPRS) network, which transmits packet data signals. In such a network, a location area can be subdivided into routing areas.

It will also be noted that the networks of the present invention allow the operation of the SMS cell broadcast system to be tested easily. Specifically, a particular device can be dynamically assigned to one or more multicast groups, and can then monitor receipt of SMS cell broadcast messages sent to that group.

There are therefore described networks, and methods of operation thereof, in which the efficiency of use of network resources, for sending SMS cell broadcast messages, can be optimised.

Claims

1. A method of transmitting a SMS cell broadcast message in a cellular communications network infrastructure comprising a plurality of base stations, the method comprising transmitting a multicast message over the network infrastructure, such that a group of said base stations respond thereto by transmitting a SMS cell broadcast message over an air interface.

2. A method as claimed in claim 1, comprising defining a single multicast group for all SMS cell broadcast messages.

3. A method as claimed in claim 1, wherein the network infrastructure comprises a plurality of base station controllers, the method comprising defining a respective multicast group containing the base stations associated with each base station controller.

4. A method as claimed in claim 1, comprising defining one multicast group corresponding to each location area in the network.

5. A method of issuing SMS cell broadcast messages over an air interface from a base station in a cellular radio communications network, the method comprising: receiving a multicast SMS cell broadcast message over the network infrastructure; and issuing a corresponding SMS cell broadcast message over the air interface.

6. A method as claimed in claim 5, wherein the base station has information about a cell in which it is located, the method comprising: determining whether a received multicast SMS cell broadcast message is specifically addressed thereto; and, if so issuing a corresponding SMS cell broadcast message over the air interface.

7. A method of testing a cellular radio communications network infrastructure, the method comprising dynamically allocating a test device to a multicast SMS cell broadcast group, and monitoring SMS cell broadcast messages received thereby.

8. A network node, for use in a cellular communications network infrastructure, the node being suitable for connection to a second node which generates SMS cell broadcast messages and to a plurality of base stations, wherein the node is adapted to receive an SMS cell broadcast message from the second node, and to transmit a multicast message to at least one of said base stations in response thereto, such that said base stations respond to the multicast message by transmitting a SMS cell broadcast message over an air interface.

9. A network node as claimed in claim 8, wherein the node has a definition of a multicast group, and wherein the node is adapted to transmit a multicast message to said multicast group in response to any SMS cell broadcast message received from the second node.

10. A network node as claimed in claim 8, wherein the node has a definition of a plurality of multicast groups, and wherein, in response to an SMS cell broadcast message received from the second node, the node is adapted to determine an intended geographic extent of said message, to select one or more of said multicast groups corresponding to the intended geographic extent of said message, and to transmit a multicast message to the selected one or more of said multicast groups.

11. A network node as claimed in claim 8,9 or 10, wherein the node is a base station controller.

12. A base station, for use in a cellular

communications network infrastructure, the base station being adapted to receive a multicast SMS cell broadcast message over the network infrastructure, and to issue a corresponding SMS cell broadcast message over an air interface in response thereto.

13. A base station as claimed in claim 12, wherein the base station has information about a cell in which it is located, and is adapted to determine whether a received multicast SMS cell broadcast message is specifically addressed thereto, and, if so, to issue the corresponding SMS cell broadcast message over the air interface.