AU2008202179A1 - Method for transmitting messages related to a broadcast or multicast service in a cellular communications system - Google Patents

Description

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION Standard Patent Applicant(s): SAMSUNG ELECTRONICS CO., LTD.

Invention Title: METHOD FOR TRANSMITTING MESSAGES RELATED TO A BROADCAST OR MULTICAST SERVICE IN A CELLULAR COMMUNICATIONS SYSTEM The following statement is a full description of this invention, including the best method for performing it known to me/us: 00 METHOD FOR TRANSMITTING MESSAGES RELATED TO A C BROADCAST OR MULTICAST SERVICE IN A CELLULAR SCOMMUNICATIONS SYSTEM BACKGROUND OF THE INVENTION This patent application is a divisional application of Australian patent application 2005204205 and relates to subject matter disclosed in that application.

Some description of the invention of 2005204205 is included herein to facilitate understanding of the present invention. If necessary reference may be had to the 00 disclosure of application 2005204205 to understand the present invention, and the Sdisclosure of that application is incorporated herein by reference.

Field of the Invention This invention relates to a broadcast or multicast service in a telecommunications system. More explicitly, but not exclusively, the invention relates to the realisation of a Multicast Broadcast services in a radio access network (RAN) such as in the Universal Mobile Telecommunications Service (UMTS) radio access network. UMTS concerns a third generation radio network using wideband code division multiple access (W-CDMA) technology.

Description of the Related Art A cellular communications system includes mobile user equipment (JlUEs), a radio access network (RAN) and one or more core networks (CNs), as illustrated in Figure 1 for the UMTS case. A detailed overview over the architecture of a cellular telecommunications system of the third generation may be found in the 3GPP specification "UTRAN Overall Description" 3GPP TS25.401 and related specifications. Communication between the UEs and the UTRAN is provided via the Uu interface whereas the communication between the UTRAN and the core networks is done via the Iu interface (Iu).

A radio access network includes base stations and radio network controllers or base station controllers (RNC/ BSC). The base stations handle the actual communication across the radio interface, covering a specific geographical area also referred to as a cell. The radio network controllers control the base stations connected to it, but in addition perform other functionality like for example the allocation of radio resources and the control of local mobility. An RNC connects to one or more core networks via the lu interface, to a number of base stations (node N:\Mclbourne\Cascs\Patcnt\60000-60999\P60436.AU. I \Specis\Specificaiondoc. 16.5.08 00 B's for the case of UTRAN) via the lub interface and possibly to one or more other c RNCs via the lur interface. The core network includes a serving GPRS (General Packet Radio Service) support node (SGSN) and a broadcast/multicast service centre (BM-SC). The BM-SC controls the distribution of the data to be transmitted 5 via the MBMS service.

Communications Networks of the third generation (3G) such as the UM'TS network provide Multimedia Broadcast Multicast Services (MBMS). MBMS is a point-to-multipoint service in which multimedia data such as audio, images or video data is transmitted from a single source entity to multiple recipients by using an uni- 0 10 directional bearer service. The MBMS bearer service offers both a broadcast mode Cl 00 and a multicast mode. In the broadcast mode, the data are broadcasted to all users.

In contrast, a user needs to subscribe to a particular MBMS service or a group of C1 MBMS services with a service provider in order to receive multicast services. The operator may then announce the service or use a service discovery mechanism to inform users about the range of MBMS services available. If the user is interested in a particular MBMS service, the user joins the service, i.e. the user activates the MBMS multicast service. In this way the user becomes a member of a particular multicast group and indicates to the network that he or she wants to receive the MBMS data of a particular MBMS service.

Transmitting the same data to multiple recipients allows network resources to be shared. In this way the MBMS architecture is designed to enable an efficient usage of radio-network and core-network resources.

In order to initiate a MBMS session, the CN sends a session start command to the RNC. The Session Start command is used to indicate that the core network is ready to send data relating to a particular MBMS service. The Session Start command triggers the establishment of a bearer resource for MBMS data transfer. It is noted that the Session Start occurs independently of activation of the service by the user. This means that a user may activate a particular service either before or after a Session Start.

After receiving the Session Start command, the RNC send MBIMS notifications to the UE in order to inform the UEs about forthcoming or even ongoing MBMS multicast data transfers. The RNC manages the use of the radio resources and decides whether the MBMS data will be transmitted using point to multipoint or point-to-point transfer mode on the radio interface. If there are sufficient UEs in a cell, the point-to-multipoint transfer mode is most efficient. If however the number of users in a cell is low, the point-to-point transfer mode may be most efficient. To decide which transfer mode to use, the RNC may perform a counting operation. Subsequently multimedia data relating to a particular MBMS N:\Melbourn\Cases\ilatent\60000-60999\P60436 AU I \Specis\Specificationdoc. 16.5.08 00 service are transmitted from the CN via the RNC to the UEs during the data transfer Sphase.

When the BM-SC determines that there will be no more data to send, the CN sends a Session Stop command to the RNC and the bearer resources are released If a user is no longer interested in a particular MBMS service, the user deactivates the service. Accordingly, the user leaves the multicast group if he or she does no longer wants to receive Multicast mode data of a specific MBMS bearer service.

It is noted that the phase subscription, joining and leaving are performed 0 10 individually per user. The other phases, such as the notification and the data 00 transfer, are performed for a particular service, i.e. for all users interested in the related service.

As of 3GPP RAN2 meeting number 39 (17-21 November 2003), the situation regarding how MBMS will be handled on the Uu interface has again become clearer. The current status of MBMS realisation in RAN2 is described in the 3GPP' specification "Introduction of Multimedia Broadcast Multicast Service (MBMS) in the Radio Access Network (RAN)" TS 25.346. v2.4.0.

SUMMARY OF THE INVENTION According to one aspect of the present invention, there is provided a method of providing a point-to-multipoint multicast service in a communications system, wherein said multicast service provides for the transmission of data from a network element to a plurality of mobile terminals, said method comprising the steps of: transmitting a first and a second message from a network element to said plurality of terminals, wherein said first message includes a plurality of configurations for transmitting said data to the plurality of terminals, and wherein said second message includes for a multicast service provided using a p-t-m transfer radio bearer a set of pointer to said configurations to be used for a particular multicast service.

transmitting data for said particular multicast service using said configurations.

In this way the signalling of radio messages relating to the set-up of radio resources for a broadcast or multicast message can be made much more efficient.

For example, by transmitting the first message more frequently than the second message, the second message may be re-used for more than one different broadcast or multicast services.

According to another aspect of the present invention, there is provided a method of signalling messages related to a point-to-multipoint broadcast or multicast service to a plurality of mobile terminals in a communications system, the method comprising: N:\Melbournc\Cases\Patent\60000-60999\P60436 AU.I\Specis\Specification.doc.16.5.08 00 O sending a first message including service specific information; and C sending a second message including information related to the radio resource configuration, wherein said second message does not include service specific Sinformation.

N According to another aspect of the present invention, there is provided a method of signalling messages related to a point-to-multipoint broadcast or multicast service to a plurality of mobile terminals in a communications system, the method comprising: 0 10 sending a first message including service specific information; and 00 sending a second message including information related to the radio resource 0 configuration, wherein said second message is used for more than one different ,I broadcast and/or multicast service.

In this way the configurations included in the radio configuration message can be used by more than one different broadcast and/or multicast service.

In this way duplication of configuration information used for more than one service can be avoided. Such a message structure also avoids duplication of the service specific information, such as the (often lengthy) identities of the multicast and/or broadcast services; according to the proposed message organisation this information only needs to be included in the service information message.

The use of two separate messages as described above makes it possible to transmit one message more frequently than the other, which may be beneficial in certain scenarios.

According to another aspect of the present invention, there is provided a method of signalling messages relates to a broadcast or multicast service to a plurality of mobile terminals in a communications system, the method comprising: sending a radio bearer information message containing a plurality of predefined radio bearer configurations, transport channel configurations and a physical channel list, excluding service IDs; and sending a service availability message including one of the service IDs and a pointer to one of the radio bearer configurations and one of the transport channel configurations and one of physical channels listed in the radio bearer information message.

BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the present invention will now be described, by example only, with reference to the accompanying figures, whereby N:\Melbourne\Cases\Patent\60000-60999\P60436.AU. I\Specis\Specification.doc. 16.5.08 00 Figs. 1 and 2 are schematic outlines of a mobile communications network, in cN which the present invention can be incorporated, Fig. 3 is a schematic illustration of a messaging timeline of a MBMS session according to the prior art; NO 5 Fig. 4 is a schematic illustration of a messaging timeline of a MBMS session according to one embodiment of the present invention; and Fig. 5 is a schematic illustration of mapping MBMS services according to one embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 00 SAn embodiment of the present invention will now be described in detail with ,i reference to the accompanying drawings. In the following description, a detailed description of known functions and configurations incorporated herein has been omitted for conciseness.

Figure 2 illustrates the architecture of a radio access network. The RAN comprises base stations 2, such as the so-called Node B's for the UTRAN, and radio network controllers 4 (RNC) also referred to as base station controllers (BSC). The base stations 2 handle the actual communication across the radio interface, covering a specific geographical area also referred to as a cell. The RNCs 4 control the base stations 2 connected to it, and also include other functionality for tasks such as the allocation of radio resources, i.e. the local mobility. An RNC 4 is connected to one or more core networks 8 via the Iu interface 12, to a number of base stations 2 via the lub interface 10 and possibly to one or more other RNCs 4 via the lur interlface 14.

In a UMTS network, the Radio Resource Control (RRC) protocol is used across the radio interface, i.e. between the UE and UTRAN. These protocol end points interact by exchanging protocol parameters, by sending messages comprising of one or more information elements.

In order to set up a MBMS session, the RNC receives a respective request from the CN. This MBMS Session Start Request contains a MBMS Service Identification, specifies the MBMS Bearer Service Type and MBMS Session Attributes such as the MBMS Service Area Information or Quality of Service parameters. After the RNC receives the MBMS Session Start Request, it notifies the UEs which are interested in and have activated the particular MBMS service.

The MBMS Session Start Request contains all information necessary to set up an MBMS Radio Access Bearer (RAB). Upon reception of the Session Start message, the RNC executes an MBMS data bearer set up over the Iu interface, and N:\Melboure\Cases\Patenl\60000-60999\P60436.AU. I \Specis\Specification doc. 16.5.08 00 subsequently informs the sending CN of the outcome of the set up in a MI3MS c Session Start response message.

For a particular MBMS service, data is then transferred via an MBMS RAI3 between the network and the UE.

In order to set up the connections between the RNC and the UE, the existing transport channel mechanism of the Forward Access Channel (FACH) over lub is used in case of a point-to-multipoint (ptm) MBMS transmission. A ptm connection is established if the number of counted MBMS users in a cell exceeds a ceriain Soperator-defined threshold. Otherwise, a point-to-point (ptp) connection is 0 10 established over the DTCH as defined for other dedicated services.

(N

00 The CN sends the MBMS Session Stop command in a similar way to the RNC, and the RNC then notifies the interested and activated UEs of the end ol the C1 MBMS session. When the RNC receives an MBMS Session Stop Request, it releases the associated MBMS RAB resource.

Referring now to Figure 3, the sequence of main events that take place during a MBMS session is described. More details may be found in the 3GPP specification TS 25.346. The session is started when a SESSION START message 101 is received by the UTRAN over lu, and terminated when the SESSION STOP message is received over lu.

After the SESSION START message 101, the UTRAN sends out M13MS notification indicators (NI's) 103 in order to wake-up UE's in RRC Idle, CELL_PCH, URA_PCH and CELLFACH states. The MBMS notification indicators 103 are sent on the MBMS notification Indicator channel (MICH-). Ul's only need to wake-up and look for the MBMS NI's at their normal paging occasions, i.e. the paging occasion for the normal UE DRX cycle used for conventional (R99) paging. As a result, the MBMS notification indicators 103 sent by the network have to be repeated continuously during one or more UE DRX cycles.

If a UE detects that an MBMS NI 103 is set for an MBMS service in which it is interested, the UE listens to the MBMS point-to-multipoint Control Channel (MCCH). It has been agreed that transmissions on MCCH will be scheduled.

although this is not specifically described in the 3GPP specification 25.346. Thus.

all UEs receiving the MBMS NIs 103 during a certain specified period will all listen to the MCCH at one specific instance, in this document referred to as the MCCInotification occasion. The specified period is typically the largest UE DRX cycle. It is assumed that the MCCH notification occasion configuration is broadcast on BCCH or MCCH.

The message sent every DRX cycle at the MCCH notification occasion is the MBMS NOTIFICATION message 105. This message 105 will at session start N:\Melbourne\Cases\Patent\60000-60999\P60436.AU \Specis\Specification.doc. 16.5.08 00 typically first trigger a counting procedure by indicating that a certain percentage, cK the so called "counting probability", of UEs interested in the session being started should respond by establishing an RRC connection It is noted that the MBlMS Notification message has not yet been described in 3GPP specification 25.346.

After the UE receives the MBMS notification message 105a, it sends a request 113 to establish an RRC connection to the core network to allow for the counting process. The request 113 includes a Service identification which identifies the MBMS service the UE is interested in. As a response, the CN identifies the MIBMS service the UE is interested in and sends a MBMS Linking Request Message 115 over the lu interface.

00 As soon as the UEs receive an "interesting" MBMS NI 103 the Uli shall Slisten to the MCCH at the MCCH notification occasions. An "interesting" MBMS SNI in this respect means that the NI relates to any of the MBMS services the UI has joined. After the first MBMS Notification message 105a has been sent, the one or more subsequent MBMS Notification messagesl05b may contain different counting probabilities. In this way the UTRAN determines whether the MBMS service should be provided by point-to-point or point-to-multipoint (ptp/ptm). By having higher counting probability at subsequent counting cycles, the UTRAN is able to obtain a gradual idea about how many UEs in the cell are interested in a specific MBMS service, and can then decide whether the MBMS service shall be provided ptp or ptm.

When the UTRAN has taken the ptp/ptm decision, the counting process will be stopped. In case ptp is selected, the interested UE's will receive a RADIO BEARER SETUP message. Figure 3 illustrates the case that the service is provide by ptm. In this case the UTRAN configures the MBMS point-to-multipoint Traffic Channel (MTCH) and updates the MCCH by sending the MBMS SERVICI.

INFORMATION message 107 and MBMS RADIO BEARER INFORMATION message 109. The two messages include the service identification and radio bearer information for the MBMS service.

After the UE has read the MBMS SERVICE INFORMATION messages 107 and MBMS RADIO BEARER INFORMATION messages 109, it is able to read the MI3MS data transmissions 111 on the corresponding MTCH. When transmission of the MBMS session is finalised and the SESSION STOP message 117 is received over Iu, the UJI will be informed about the session stop by a RADIO BEARER RELEASE message in case of ptp or a SESSION STOP notification 121 for ptm transmission. In order to ensure that all UEs detect the SESSION STOP notification, the UTRAN send again MBMS NIs 119, such that the interested UE listens to the MCCII.

N:\Melbourne\Cases\Patent\60000-60999\P60436.AU. I \Specis\Spccification.doc. 16.5.08 -9- 00 e--I 0Usage of MCCH notification occasion interval

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N As can be seen from the schematic illustration of Figure 3, the above described solution provides for one MCCH notification message at every MCCH notification occasion, with a fixed period between MCCH notification occasions equal to the ,O 5 (largest) UE DRX cycle. This appears as a simple and natural solution, as all tEs which are receiving the MBMS NI in one DRX cycle are also reading the same MCCH message.

However this approach has the disadvantage that the total time period the SMBMS NI have to be sent for a particular MBMS session are relatively long.

O 10 As an example, it is assumed that the error rate for transmitting the MI3MS NI ("4 00 is 1 and that the intervals between the MCCH notification occasions are equal to the UE DRX cycle of 1.28 seconds. Moreover, it is assumed that the LJTRAN requires three cycles with different counting probabilities to decide whether the MBMS session is to be transmitted in the ptp or in the ptm mode.

Due to the MBMS N1 error rate, the MBMS NI's have to be set at least during two different DRX cycles when the ptm decision is taken. Thus in total at session start, we will have to set the corresponding MBMS NI's during 5 UE DRX cycles more than 7 seconds of continuous MBMS NI's. If we include the two I)RX cycles we will need to inform all UE's of the Session termination, in total the MBMS PI's will be set for more than 10 seconds per session.

It is therefore advantageous to provide a MCCH notification occasion interval different to the longest UE DRX period. If a MCCH notification occasion interval is used which is shorter than the longest UE DRX cycle, the total time required to set up a MBMS session can be reduced.

First Embodiment According to a first embodiment, this can be achieved by providing additional MCCH notification occasions. The network signals an MCCH notification occasion schedule to the UE. For signalling the schedule the BCCH may for example be used.

In addition, it is specified that instead of listening only to one MCCH notilication occasion, the UE shall listen to all scheduled MCCH notification occasions starting from the moment it detects the MBMS NI and up to the next dedicated paging occasion. In this way an MCCH notification occasion interval of less than the normal DRX cycle can be achieved.

It is now referred to Figure 4, which illustrates the messaging for an MBIMS session having an MCCH notification occasion interval of half of the normal I)RX cycle. The same reference numerals as in Figure 3 are used for corresponding messages.

It can be seen that the second MCCH notification message 105b follows the first message 105a after a half UE DRX cycle. Therefore, the duration of the MB1lMS N:\Melbourn\Cass\Platent\60000-60999\I160436AU. I \Specis\Spccifcationdoc. 16.5.08 00 notifications CRX cycle is half of the longest UE DRX cycle. In this way the delay c" introduced by the counting procedure, i.e. from the session start message 101 to the SMBMS notification 105c, indicating that the session is broadcast over ptm, is only Stwo cycles rather than three cycles in the prior art MBMS session as outlined in IO 5 Figure 3.

However, in practice there is a limit to how much the period between 2 MBMS Notification messages can be decreased as the counting process itself takes a certain time. After the UE received the MBMS notification start messages 105a and 105b, it needs to send an RRC connection request 113. After a certain time 0 10 period the UE receives the MBMS UE linking request message 115 over the lu.

00 Therefore, in practice the MBMS notification cycle needs to be at least as long as Sthe time period between the messages 113 and 115. As an example, assume that it N takes 200ms in between a UE sending an RRC CONNECTION REQUEST 113 and receiving the MBMS UE LINKING REQUEST message 115. In that case, the period in between two consecutive MBMS NOTIFICATION messages needs to be at least 200ms.

Configuration of MBMS SERVICE INFORMATION message and MBMS RADIO BEARER INFORMATION message As described above with reference to Figure 3, MBMS service information is transmitted from the RNC to the UEs in two messages. The two messages are used to inform the UEs of all MBMS services available in one cell and to send the jUl-s radio bearer information relating to the MTCH. These two messages are the MBMS SERVICE INFORMATION message 107 and the MBMS RADIO BEARER INFORMATION message 109.

According to the 3GPP specification TS 25.346, MBMS SERVICE INFORMATION message is transmitted periodically to support the mobility in the MBMS service. The MBMS SERVICE INFORMATION message contains MIBMS service IDs and ptm indication. The MBMS service IDs indicate the MBMS services which are being served in the cell or the MBMS services which can be served if the UE requests it. Ptm indication indicates that the MBMS service is on ptm in the cell, thus it informs the UE of the need of reception of the MB1MS RADIO BEARER INFORMATION message. More information may be included in the MBMS SERVICE INFORMATION message.

MBMS RADIO BEARER INFORMATION includes MBMS Service ID, logical channel, transport channel and physical channel information for an MI3MS service. More information may be included in MBMS RADIO BEARER

INFORMATION

N:\Meibourne\Cascs\Patcnt\60000-60999\P60436AU I \Spccis\Spciicationdoc. 16.5.OX -ll- 00 O It is noted that the 3GPP specification TS 25.346 specifies that both messages, C i.e. the MBMS radio bearer information as well as the MBMS radio bearer t information message include the service IDs, although the information in the specification relating to the content and structure of these messages is sparse.

\D 5 However, it is important to set up the content and structure of the messages relating to the MBMS information in an efficient way. Particularly, the distribution of the information between the two messages is crucial in order to avoid duplication of information. For example, duplication of the service IDs or other information in the two messages may result in a waste of radio resources.

00 Second Embodiment In the following it is described how the content and structure of the two c MBMS information messages may be set up. A particular way of splitting the MBMS information into the MBMS service information and MBMS radio bearer information message is proposed and a way to avoid duplication or even multiplication of sending radio bearer information is described.

According to this embodiment, all service specific information appears only in a first message, referred to as the MBMS SERVICE AVAILABILITY message in the following, while the details of the radio resource configuration is included in a second message, i.e. the MBMS RADIO BEARER INFORMATION message.

It is noted that the existing model for mapping services and resources on to the radio interface as described in the 3GPP specifications is re- used for MBMS as much as possible.

Referring now to Figure 5, an example is given to illustrate the principle of mapping MBMS services and resources in the same manner on the radio interlace as other services.

The structure of Figure 5 includes three different radio access bearers 201 to 203, five radio bearers 211 to 215, four different transport channels 221 to 224 and two different physical channels 231 and 232.

The mapping structure used for the MBMS service is the following: One MBMS service maps onto a single RAB, which maps to one or more RBs, i.e. the use of RAB sub- flows is not excluded. Each RB corresponds to an MTCHI- logical channel. One or more of these logical channels may be mapped onto a lACI I transport channel, and one or more of these transport channels are mapped onto a physical channel.

Thus, each of the three RABs 201 to 203 corresponds to one MBMS service.

Of these three RABs, one RAB (RAB 201) maps to the three RBs 211, 212 and 213.

whereas the other two RABs 202 and 203 each correspond to RB 214 and 215, respectively.

N:\Melbourne\Cases\latcnt\60000-60999\P60436 AU. I \Specis\Spcificaion.doc. 165.08 12-

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RB 211, 212 and 215 then map onto the transport channel (TrCh) 221, 222 and N 224, respectively, whereas both RBs 213 and 214 corresponds to transport channel 223.

Moreover, the transport channels 221, 222 and 223 all correspond to physical channel (PhCh) 231, whereas transport channel 224 maps onto physical channel 232.

Thus Figure 5 illustrates that, for example, a physical channel can carry multiple transport channels, and that a transport channel can carry multiple R3s.

The transport channel is indicated within the RB mapping information. Since the transport channel identity is unique within the scope of a physical channel both 00 the transport channel identity and the Secondary Common Control Physical Channel S(S-CCPCH) identity need to be included in the RB mapping info.

N Several MBMS services can use the same radio bearer configuration. The same applies for the transport channel configuration. To provide efficient signalling support for this, the MBMS RADIO BEARER INFORMATION contains a number of pre-defined radio bearer and transport channel configurations. For each service, the MBMS SERVICE AVAILABILITY message then includes a pointer to one of the radio bearer configurations, and one of the transport channel configurations and one of the physical channels listed in the MBMS RADIO 13BARliR INFORMATION message. As can be seen from Figure 3 and 4, both the MBMS service availability message as well as the MBMS radio bearer information message are transmitted via the MCCH channel.

In this way an efficient way of signaling the information required to set up an MBMS p-t-m radio bearer can be achieved by two different aspects.

Firstly, duplication of the service identities is avoided, as the MBMS RADIO BEARER INFORMATION message does not contain the service IDs, but the MBMS Service Availability Message. Thus the amount of data to be transmitted on the MCCH can be considerably reduced. As an example, consider that there are 16 active MBMS sessions in parallel, and assume a service identity of 32 bit and a iUl DRX cycle of 640ms. By applying the above described approach of splitting the MBMS service information, the transmission rate on the MCCH can be reduced by almost 1 kbps.

Secondly, if several MBMS services share the same radio bearer and transport channel configuration further gains are achieved when several MBMS services use the same predefined radio bearer, transport channel and physical channel configurations. Instead of repeating the entire configuration for each service, the configuration elements are included once in the Radio Bearer Information message.

and for each service a pointer to one of these pre-defined configurations is included N:\Melbourne\Cascs\Paten\60000-60999\P60436A U. I \Spec is\Speciflcationdoc. 1 6.5.08 13- 00 in the Service Availability message. In this way the signaling of information relating c to the set-up of MBMS messages can be made much more efficiently.

Below, example message layouts are shown for an MBMS service availability message (Table 1) and for an MBMS Radio Bearer Information message (Table 2) 5 according to one embodiment of the present invention.

Referring now to Table 1, the content and structure of the MBMS service availability message is described. It is noted that the symbol indicates a hierarchical structure.

The first column of tables 1 and 2 specifies the Information element or group name of the information included in the two messages. Column 2 indicates whether 00 the information is mandatory (Mandatory Present MP) or optional (Optionally Present OP), or whether this has not been agreed (For Further Studies FIS). The 1 third column indicates the size of the list, whereas the forth column indicates a rough estimate of the total size of the information element (in bits). In the 11lih column additional information or comments regarding the size estimate for the different elements are provided.

The first information element of the MBMS service availability message in row 1 of Table 1 includes the message type, which indicates the type of the message and whether the message includes in addition any extension bits. The next element is the service list, listing all provided MBMS services. Up to 32 MBMS services are simultaneously available in a cell message. The list includes the MBMS service identities (IDs) as listed in row 3, and two further fields indicating whether a Packet Mobility Management (PMM) connection is required and the choice of transfer modes rows 4 and Rows 5 and 6 gives the choice of transfer modes as either ptp or ptm. Row 7 includes the RAB information, which is required to set up the ptm radio bearer and is provided for the MBMS services using this transfer mode.

Row 8 indicates the list of required radio bearer information. The list includes the RB identity and the RB mapping information as listed in rows 9 and 10. 'Those two fields include the pointers to the RB information provided in the MBMS radio bearer information message. The RB identity identifies a RB configuration included in the MBMS radio bearer information message. Up to 32 RBs can be identifies in a cell. The RB mapping information includes a pointer to the logical channel, to the transport channel and to the SCCPCH i.e. the RB mapping information includes the identities of the logical channel, the transport channel and the SCCPCH The last row indicates the estimated total message size for one particular case.

In this case the number of ptp and ptm connections is assumed to by 8 and the number of radio bearers used in assumed to be 1. In this case the total message size can be estimated to be 771 according to the following calculation: N:\Mclboumc\Cascs\Patent\60000-60999\P60436.AU. I\Spccis\Spccificationdoc. 16.5.08 14- 00 O 11 (34 N_ptp)+ (34 (3 N_rb 24) N_ptm) 771 for N_ptp= N N_ptm 8 and N_rb 1) In a typical set-up each MBMS service maps onto a single RB while the different services are all mapped onto the same FACH, MAC/ logical channel multiplexing is applied. In this case, each logical channel identifier value, used within the MAC header, identifies a specific MBMS service.

Referring now to Table 2, the content and structure of the MBMS radio bearer message is described.

Again, the first element is the message type (row After this, the message includes a list of predefined the point-to-multipoint RB information configurations, 00 transport channel configurations and physical channel configurations (rows 2, 7 and 815).

1 The RB information includes the RB identifies, Packet Data Convergence Protocol (PDCP) information, Forward Error Correction (FEC) information and Radio Link Control (RLC) information (rows 3 to For the following, it is assumed that the message size required for the RB identity is 7 bits, for the I'FLC information 20 bits, for the PDCP information 49 bits (for a single algorithm such as the Robust Header Compression (ROHC) and a single profile), and that the size for the RLC information using UM/TM segmentation is 5bits, the total size for the RB information list is given by 7 81 N_rb, whereby N_rb denotes the number of radio bearers listed in the message.

The SCCPCH list includes the SCCPCH identity (row the Transport Format Combination Set (TFCS) (row a list of the FACH (rows 10 to 13) and a PICH information (row 14). The list of FACH includes the transport channel identities, the Transport Format Set (TFS) and the Common Traffic Channel (CTCH) indicators. Using the estimates provided in the last column, the total size for the SCCPCH list is given by 144 bits for a single SCCPCI-. Every additional SCCPCH adds another 140 bits. It is noted that even though it has not yet been decided whether the fields including PDCP and FEC is mandatory, corresponding parameters have been included in the size estimate.

The physical channel configuration is provided in the Secondary CCPCI I information of row 15. The estimated size of the Secondary CCPCH information list is 14 to 26 bits, including secondary scrambling code and timing offsets.

N:\MeIbourne\Cases\Patent\60000-60999\160436.AU. I\Specis\Specificaiondoc. 16.508

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From the above it can be seen that for a typical MBMS configurations (assume 16 active MBMS services mapped on one RB, FACH and sCCPCH) both message have a comparable size.

MBMS SERVICE AVAILABILITY Information Nee Value Siz Comment element/ d e Group name Message type MP 5 Overhead of message type, extension bit Service list OP maxMBMSse 6 Upto 32 MBMS services rvPerPage simultaneously available in a cell message >Service ID MP 32 MBMS service identity eg.

TMGI

>PMM MP 1 connection required >CHOICE MP 1 Transfer mode >>PTP 0 (no data)

>>PTM

>>>RAB MP information to setup RB MP maxRBperRAB 3 information to setup list MP 5 Identifies a RB configuration identity included in the MBMS RADIO BEARER INFORMATION message.

Upto 32 RBs can be identified in a cell N :\Melboume\Cases\Patent\60000-60999\60436.AU. I\Specis\Specification doc. 16.5.08 16- 00 >>>BMID 19 Including the logical channel mapping info identity, as well as the transport channel identity and an S-CCPCH identity (requires a modified version of the existing data -4 Total 771 11 (34 Nptp)+ (34 (3 message size Nrb* 24) Nptm) 771 for the reference case Nptm= 8 and Nr= 1) Table 1 MBMS RADIO BEARER INFORMATION Information Nee Value Siz Comment element/ Group d e name Message type MPD 5 Overhead of message type, extension bit PTM RB info list MP maxMBMS- 7 7+ (81 Nrb) _______RBperCell >RB identity MPD 7 >PDCP info FF 49 Single algorithm (ROHO).

S single profile >FEC info FFS 20 Just a wild guess >RLC info MID 5 UM/ TM, segmentation SCCPCH list MP maxSCCPCH 4 4 ((80 60 Nfach)* Nsccpch) 144 for a single S-CCPCH.

Every S-CCPCH adds 140 (if the same assumptions apply) >SCCPCH MPD 4 maxSCCPCH equals 16 N:\MclIbou rne\Ca ses\Paten 1\60000-609 99\11604 36. A U, 1\Spec is\Specificationdoc. 1 6.5.08 -17-

O

0 O

(N,

>TFCS MP 50 Just the 6 TFs >FACH list MP maxFACHPCH 3 63 for a single FACH with 6 TFs. Each additional FACH may add 60+ (depending on TFS and TFCS impact) >>Transport MP channel identity >>TFS MP 54 (0x320, 1x320, 2x320, 4x320, 8x320, 16x320) ms TTI >>CTCH MP 1 indicator >PICH info OP 1 Absent; N/A for S-CCPCH carrying MTCH >Secondary MP 26 14 upto 26 (secondary CCPCH info scrambling code timing offset included) 4 Total 808 16 (81 Nrb)+ ((84 message size Nfach) Nsccpch) 804 assuming Nrb=8 (each PTM service having a separate RB configuration), single S-CCPCH, single FACH and TF/ TFCS as indicated Table 2 Third Embodiment Alternatively to the embodiment described above, avoiding of informaion duplication can also achieved by providing only a single MBMS inlbrmation message instead of having an MBMS service information message and a separate MBMS radio bearer information message. Therefore, according to this embodiments all MBMS information contained in the two messages described above are combined in a single MBMS information message by using a simple concatenation of the two separate messages indicated above.

N:\Mclbournc\Cascs\Patent\60000-60999\160436.A. I\Spccis\Spcificaiondoc. 16.508 00 -18-

O

However, the approach of having two separate messages as described above c has the additional advantage that one of the two messages can be transmitted more frequently than the other.

Apart from the MBMS session start, the MBMS SA and RB message are also IND 5 used for handling the mobility of UEs while receiving MBMS services. If a U1: in an RRC-IDLE state moves into a new cell, the UE has to find out if and how an MBMS service is supported in a cell. If the service is supported by ptm transmission in the new cell, the UE will only have to read the MBMS SA and MBMS R13 messages. Subsequently, the UE can receive the MTCH channel.

If, on the other hand, the service is supported by ptp transmission in the new 00 cell, the UE will have to establish an RRC Connection, go to the PMMCONNECTED state and wait for the RB SETUP for the RB of the MBMS

C

service. It is apparent that this procedure is relatively slow.

However, the UE only needs to receive the MBMS SA message and not the MBMS RB information to detect that an MBMS service is supported by ptp.

Therefore, the service interruption for a UE moving into the new cell can be significantly reduced by scheduling the MBMS SA message more frequently than the MBMS RB message.

Thus, by having two separate messages rather than one combined message, the MBMS SA message frequency can be increased without the need of increasing the frequency of the MBMS RB message. In this way an additional load due to inclusion of RB information in one message can be avoided while increasing the frequency of the MBMS SA message.

Whilst the above described embodiments have been described in the context olr UMTS, it is appreciated that the present invention can also be applied to other similar. For UMTS, it is expected to be applicable to all releases.

Whilst in the above described embodiments it has been described that the MBMS RB information message is transmitted on the MCCH, it is appreciated that alternatively some of the information indicated in the MBMS RB INFORMATION message could be transported on the BCCH instead. For example, if the MCCI I is multiplexed with MTCH's, then in order to be able to find the MCCI-, the sCCPC I information for the sCCPCH carrying the MCCH can be provided on the BCCI I. In this case the MBMS RB INFORMATION message may just include a reference to the corresponding sCCPCH configuration when indicating the mapping of an MTCH. However, it is advantageous that this multiplexing option is only used when the transport channel and physical channel configuration is relatively static.

otherwise the BCCH will need to be updated to frequently.

N\Meibourne\Cases\Patent\60000-60999\P60436 AU I\Specis\Spcciication doc.16 5 08 -19- 00 It is noted that throughout this document the term "message" is used to include C1 both indicators and messages, i.e. a message may either include only a single Sindication, or may include a message comprising different information elements.

It is to be understood that the embodiments described above are preferrcd ID 5 embodiments only. Namely, various features may be omitted, modificd or substituted by equivalents without departing from the scope of the present invention.

which is defined in the accompanying claims.

In the claims which follow and in the preceding description, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an 00 inclusive sense, i.e. to specify the presence of the stated features but not to preclude Sthe presence or addition of further features in various embodiments of the invention.

CK It is to be understood that, if any prior art publication is referred to herein.

such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art, in Australia or any other country.

N:\Mclbournc\Cases\Patent\60000-60999\P60436 AU.!\Specis\Spcciication.doc. 16.5.08

Claims (14)

1. A method of providing a point-to-multipoint multicast service in a communications system, wherein said multicast service provides for the D 5 transmission of data from a network element to a plurality of mobile terminals, said method comprising the steps of: transmitting a first and a second message from a network element to said plurality of terminals, wherein said first message includes a plurality of configurations lor 0 10 transmitting said data to the plurality of terminals, and 00 wherein said second message includes for a multicast service provided using a p-t-m transfer radio bearer a set of pointer to said configurations to be used Ior a N c particular multicast service, transmitting data for said particular multicast service using said configurations.

2. A method according to claim 1, wherein each of said plurality of' configurations includes a radio bearer configuration, a transport channel configuration and a physical channel configuration.

3. A method according to claim 1, wherein said first message is transmitted on a multicast control channel.

4. A method according to claim 1, wherein said second message is transmitted on a multicast control channel. A method according to claim 1, wherein the frequency of transmitting said first message is different to the frequency of transmitting said second message.

6. A method according to claim 1, wherein said first message is the MBMS service availability message.

7. A method according to claim 1, wherein said second message is the MBMS radio bearer information message.

8. A method of signalling messages related to a point-to-multipoint broadcast or multicast service to a plurality of mobile terminals in a communications system, the method comprising: N:\Melbourne\Cases\P1atent\60000-60999\160436.AU I \SpccisSpccificationdoc. 16.5.08 -21 O sending a first message including service specific information; and cK1 sending a second message including information related to the radio resource configuration, wherein said second message does not include service specific Sinformation. I0

9. A method of signalling messages related to a point-to-multipoint broadcast or multicast service to a plurality of mobile terminals in a communications system, the method comprising: sending a first message including service specific information; and sending a second message including information related to the radio resource (Nl 00 configuration, wherein said second message is used for more than one different Sbroadcast and/or multicast service. A method according to claim 9, wherein said second message includes a list of possible radio bearer configurations, a list of possible transport channel configurations, and/or a list of possible physical channels.

11. A method according to claim 10, wherein said first message includes a pointer to one of said radio bearer configurations, to one of said transport channel configurations and/or to one of said physical channels.

12. A method according to claim 8, wherein said first message is transmitted more frequently than said second message.

13. A method according to any of claims 1 to 12, wherein said broadcast or multicast service is a multimedia broadcast multicast service (MBMS).

14. A method according to any of claims 1 to 12, wherein said broadcast or multicast service is according to the UMTS standard. A cellular communications system comprising network portions and a plurality of terminals, wherein said system is adapted to implement the method according to any of claims 1 to 12.

16. A method of signalling messages relates to a broadcast or multicast service to a plurality of mobile terminals in a communications system, the method comprising: N:\Melbourne\Cases\Patcnt\60000-60999\P60436.AU I\Spccis\Spcciicaion.doc. 16.5.08

22- 00 sending a radio bearer information message containing a plurality ol c predefined radio bearer configurations, transport channel configurations and a physical channel list, excluding service IDs; and sending a service availability message including one of the service ND 5 IDs and a pointer to one of the radio bearer configurations and one of the transport channel configurations and one of physical channels listed in the radio bearer information message. 17. A method according to any one of claims 1 to 16, and substantially as 0 10 herein described with reference to the accompanying drawings. (N 00 O t'N N:\Melbournc\Cases\Paten\60000-60999\P60436 AU. I\Specis\Specification.doc. 165.08