MBMS OV - (2) MBMS Operation Mode

3GPP has defined two modes of operation for MBMS:

- the broadcast mode

- the multicast mode.

The broadcast mode differs from the multicast mode in that there is no specific requirement to activate or subscribe to the MBMS in broadcast mode.

The multicast mode generally requires a subscription to the multicast subscription group and then the user joining the corresponding multicast group. The subscription and group joining may be made by the PLMN operator, the user or a third party on their behalf (e.g. company).

The following trust relationships between the roles that are participating in MBMS services are proposed:

- the user trusts the home network operator to provide the MBMS service according to the service level agreement (SLA);

- the user trusts the network operator after mutual authentication;

- the network trusts an authenticated user using integrity protection and encryption at RAN level;

- the network may have trust or no trust in a content provider.

The home network and visited network trust each other when a roaming agreement is defined, in the case the user is roaming in a VPLMN.

1.1. MBMS Broadcast Mode

The broadcast mode is a unidirectional point-to-multipoint transmission of multimedia data (e.g. text, audio, picture, video) from a single source entity to all users in a broadcast service area.

Broadcast service Availability

If provided by the network MBMS in broadcast mode shall be available to all users in the broadcast service areas that are registered/attached to a PLMN.

Broadcast service

- A unidirectional point-to-multipoint service in which data is efficiently transmitted from a single source to multiple UEs in the associated broadcast service area.

- Broadcast services may be received by all users who have enabled the specific broadcast service locally on their UE and who are in the broadcast area defined for the service.

- The PLMN operator shall be able to provision one or more broadcast services within his PLMN.

- The operators sharing a network shall be able to provide one or more broadcast services for their own subscribers and inbound roamers from roaming partners only.

- A broadcast service shall be able to distribute different content data to different locations, i.e. local broadcast areas, within the broadcast service area. In any location a user will never receive different content data from a single broadcast service.

Broadcast service area or broadcast area

- The area in which a specific broadcast service is available.

- A broadcast area is configured individually for each broadcast service.

- Broadcast areas associated with different broadcast services are independent of each other and may overlap.

- It is defined individually per broadcast service.

- The broadcast service area may represent the coverage area of the entire PLMN, or part(s) of the PLMN’s coverage area.

- The broadcast service area is the sum of all local broadcast areas offering the same service.

Broadcast session

- A continuous and time-bounded reception of a broadcast service by the UE.

- A single broadcast service can only have one broadcast session at any time.

- A broadcast service may consist of multiple successive broadcast sessions which can be received by UE.

- A broadcast service might consist of

- a single on-going session (e.g. a media stream) or

- involve several intermittent sessions over an extended period of time (e.g. messages).

Broadcast data transmission

- MBMS data transmission should adapt to different RAN capabilities or different radio resource availability, e.g. by reducing the bitrate of the MBMS data.

Quality of service

- The PLMN operator shall be able to configure the quality of service for each individual broadcast service. It should be possible to adapt the MBMS data transmission to different RAN capabilities or different radio resource availability.

- The home environment shall be able to set priority to select which simultaneous broadcast services are supported when there is a limit on the resources available.

Types of data services

- MBMS in the broadcast mode shall be transparent for the transferred data packets independent of the type of service being transmitted, will support a number of services, and permit support of and therefore transfer all data types e.g. Audio, Data, Video or combinations thereof.

- A minimum number of data types may need to be identified to enable interoperability.

Sources of data services

- In addition to supporting their own broadcast services the PLMN shall as well support broadcast services from third parties (i.e. HE-VASPs or VASPs or IMS server)

Broadcast service announcements

- The PLMN operator shall be able to provide service announcements for a broadcast service within and outside of the broadcast area defined for the service. The broadcast mode could be advertising or a welcome message to the network. As not all users attached to the network may wish to receive these messages then the user shall be able to enable/disable the reception of these broadcast service on his UE.

User mobility

- The user shall be able to continue receiving broadcast services throughout the broadcast service area. For example, in case of handover and presuming that a certain broadcast service is offered in the target cell, it should be possible for the user to continue receiving the service in the target cell.

User selectivity

- The user shall be able to discover what broadcast services are available at the user's current location and outside of the current location.

- The user shall be able to enable/disable the reception of specific broadcast services and can receive simultaneously more than one MBMS service.

- The user may be able to define service preference for reception. A priority procedure may be implemented to allow the user to select between simultaneous broadcast services e.g. while receiving commercial broadcast service a new broadcast service may interrupt this.

- While receiving one or more broadcast services, it shall be possible for the user to be informed about incoming voice calls or the availability of other MBMS services.

Broadcast Service in UE

- The broadcast mode should allow terminals to minimise their power consumption. The reception of the traffic in the broadcast mode is not guaranteed. The receiver may be able to recognize data loss.

- Dependent on terminal capabilities, it shall be possible for the user to participate in other services, while simultaneously participating in MBMS services. For example the user can originate or receive a call or send and receive messages whilst receiving advertisements.

Network and radio efficiency

- The PLMN operator shall be able to use network and radio resources in an efficient manner. The operator shall be able to schedule a certain broadcast service at pre-determined times.

1.2. MBMS Multicast Mode

The multicast mode allows the unidirectional point-to-multipoint transmission of multimedia data (e.g. text, audio, picture, video) from a single source point to a multicast group in a multicast service area.

Multicast services Availability

- If provided by the network, MBMS in multicast mode shall be available to all users that are registered/attached to a PLMN.

Multicast services

- A unidirectional point-to-multipoint service in which data is efficiently transmitted from a single source to a multicast group in the associated multicast service area.

- Multicast services can only be received by such users that are subscribed to the specific multicast service and have joined the multicast group associated with the specific service.

- The PLMN operator shall be able to provision one or more multicast services.

- A multicast service shall be able to distribute different content data to different locations, i.e. local multicast areas, within the multicast service area. In any location a user will never receive different content data from a single multicast service.

Multicast services area

- The area in which a specific multicast service is available.

- It is defined individually per multicast service.

- The multicast service area may represent the coverage area of an entire PLMN, or part(s) of the PLMN’s coverage area.

- The multicast service area is the sum of all local multicast areas offering the same service.

- A multicast area is configured individually for each multicast service.

- Multicast areas associated with different multicast services are independent of each other and may overlap. Multicast service areas may cover part(s) of one or more PLMNs

Multicast Session:

- A continuous and time-bounded reception of a multicast service by the UE.

- A single multicast service can only have one multicast session at any time.

- A multicast service may consist of multiple successive multicast sessions which can be received by the UE, involves one or more successive multicast sessions.

- A multicast service might consist of

- a single on-going session (e.g. a multimedia stream) or

- involve several intermittent multicast sessions over an extended period of time (e.g. messages).

Multicast subscription groups and multicast groups

- In the multicast mode there is the possibility for the network to selectively transmit to cells within the multicast service area which contain members of a multicast group.

- Multicast group: A group of users that have an activated MBMS in multicast mode and therefore are ready to or are receiving data transmitted by this service. The multicast group is a subset of the Multicast subscription group. Multicast subscription group members may join the corresponding multicast group.

- Multicast Subscription Group: A group of users who are subscribed to a certain MBMS in multicast mode and therefore authorised to join and receive multicast services associated with this group.

- The PLMN operator shall be able to provision one or more multicast subscription groups. The home environment shall be able to make a user a member of a multicast subscription group (subscription).

Multicast subscription

- Multicast subscription: The process by which a user subscribes or is subscribed to a multicast subscription group and thereby is authorised to join certain multicast services. Multicast subscription is performed either upon user selection or due to home environment initiation.

- On receipt of a request to join a multicast group, the PLMN shall check that the user is a member of the applicable multicast subscription group. The home environment shall be able to join users to the multicast group e.g. at the request of the subscriber.

- The subscriber shall be able to subscribe to or unsubscribe from a multicast subscription group. The user shall be able to join a multicast group only if he is a member of the applicable multicast subscription group. The user shall be able to leave a multicast group if he is a member of that group.

Quality of service

- The PLMN operator shall be able to configure the quality of service for individual multicast services. It should be possible to adapt the MBMS data transmission to different RAN capabilities or different radio resource availability.

- As part of the same service, it should be possible for the operator to provide the UEs with multiple successive sessions with different quality-of-service for each session.

- The home environment shall be able to set priority to select which simultaneous multicast services are supported when there is a limit on the resources available.

Types of services

- The multicast mode shall be independent of the type of service being transmitted, will support a number of services, and permit support of all data types e.g. Audio, Data, Video or combinations thereof. A minimum number of data types may need to be identified to enable interoperability

Sources of services

- In addition to supporting their own multicast services the PLMN shall as well support multicast services by third parties (i.e. HE-VASPs or VASPs or IMS server).

Multicast service announcements

- The PLMN operator shall be able to provide service announcements for a multicast service within and outside of the multicast area defined for the service.

Multicast data transmission

- MBMS data transmission should adapt to different RAN capabilities or different radio resource availability, e.g. by reducing the bitrate of the MBMS data.

User mobility

- The user shall be able to continue receiving multicast services throughout the multicast service area in which the service is provided. For example, in case of handover and presuming that a certain multicast service is offered in the target cell, it should be possible for the user to continue the session in the target cell. It is possible that data loss will occur due to user mobility.

User selectivity

- The user shall be able to discover what multicast services are available at the user's current location and outside of the current location. The user shall be able to select between different multicast services provided to the user and can receive simultaneously more than one MBMS service.

- The user may be able to define service preference for reception. A priority procedure may be implemented to allow the user to select between simultaneous broadcast/multicast services e.g. while receiving commercial broadcast service a new multicast service may interrupt this.

- While receiving PS or CS services, it shall be possible for the user to receive notification of MBMS multicast sessions.

- While receiving one or more multicast services it shall be possible for the user to be informed about incoming voice calls or the availability of other MBMS services.

Multicast Service in UE:

- Dependent on terminal capabilities, it shall be possible for the user to participate in other services, while simultaneously participating in MBMS services. For example the user can originate or receive a call or send and receive messages whilst receiving MBMS video content.

- Multicast mode should allow terminals to minimise their power consumption.

IP Multicast Service vs MBMS

- The multicast mode defined in MBMS should not confuse with IP Multicast (RFC s 1112, 1301, 1458, 1920). There are similarities between these two services and such similarities may exploit in 3GPP networks but maximizing efficiency on the radio interface and of network resources. Multicast mode shall be inter-operable with IETF IP Multicast so that current and future services can deliver in a more resource efficient manner.

Network and radio efficiency

- The PLMN operator shall be able to use network and radio resources in an efficient manner.

- The operator shall be able to schedule a certain multicast service at pre-determined times.

- Within the multicast service area, the network may distribute the data across the whole multicast service area or parts of the area. The decision to distribute to only parts of the multicast service area may be based on: a) multicast group members are present in a given part of the multicast area b) resources are not available in parts of the multicast service area.

Multicast Service – Misc:

- Reception of multicast services cannot be guaranteed over the access network. For many applications and services guaranteed data reception may be carried out by higher layer services or applications which make use of MBMS.

1.3. Service Announcement and Discovery of MBMS (broadcast/multicast) services

The user shall be able to find out or be informed about MBMS services available in the network. The network shall support service announcements both for the broadcast and multicast mode of MBMS in order to enable the user to be informed about the MBMS services available currently, or some time later..

Users should also be able to discover and monitor MBMS service availability e.g. using a URL.

- MBMS service announcement/discovery mechanisms should allow users to request or be informed about the range of MBMS services available. This includes operator specific MBMS services as well as services from content providers outside of the PLMN.

- Operators/service providers may consider several service discovery mechanisms. This could include standard mechanisms such as SMS, or depending on the capability of the terminal, applications that encourage user interrogation. The method chosen to inform users about MBMS services may have to account for the users location, (e.g. current cell, in the HPLMN or VPLMN). Users who have not already subscribed to a MBMS service should also be able to discover MBMS services.

The following could be considered useful for MBMS service discovery mechanisms (not exhaustive): -

- SMS-CB

- MBMS Broadcast mode to advertise MBMS Multicast Services

- PUSH mechanism (WAP, SMS-PP)

- Web URL

1.4. Multicast subscription and reception of MBMS services

The following is the expected sequence for the user to be able to access the MBMS multicast mode:

1 The user subscribes or is subscribed to a multicast subscription group which is uniquely identified and thereby becomes a member of that group. The subscription may be continuous (e.g. as defined by the subscriber's contract), time-limited, or generated by the subscriber on a one-time basis.

2 The user discovers, or becomes aware (e.g. via service announcements), that there are multicast services currently active, or multicast services that will become active at some time later, at the user's current location.

3a) The user selects a multicast service and hence the user joins the corresponding multicast group. The user should be able to join a multicast service as soon as possible after announcement of the service.

3b) As an alternative, the Home Environment can join the user to the selected multicast group on behalf of the user, that has previously subscribed to this multicast group.

Signalling exchange between the UE and the network might not be necessary in some cases, e.g. in the case of network congestion.

4 If the transmission is not already in progress the network starts transmitting the corresponding multicast content. Alternatively, the transmission may start at a later time.

5 The network may optionally select to set up unicast (point to point) connections to some users e.g. if there are insufficient users to justify multicasting

6 The UE starts receiving the multicast data associated with the multicast group(s) it has joined

7 The user may choose to stop receiving a selected multicast service and thereby leaves the multicast group. The user may also select to continue (or not) to receive service announcements for this multicast subscription group.

8 The user may unsubscribe or be unsubscribed from the multicast subscription group and stop receiving both the multicast data and future service announcements for this multicast subscription group.

The home environment shall be able to remove a user from a multicast group (deactivation) and if required remove the subscriber from the multicast subscription group (un-subscription).

This is required to allow the operator to bar service.