Multimedia Broadcast
Multicast Service, MBMS
A new service introduced in 3GPP Release 6 specifications is
Multimedia Broadcast Multicast Service (MBMS). There are two high level modes
of operation in MBMS, as given
1.
Broadcast
mode, which allows sending audio and video. The already existing Cell Broadcast
Service (CBS) is intended for messaging only. The broadcast mode is expected to
be a service without charging and there are no specific activation requirements
for this mode.
2.
Multicast mode allows sending multimedia data
for the end users that are part of a multicast subscription group. End users
need to monitor service announcements regarding service availability, and then
they can join the currently active service. From the network point of view, the
same content can be provided in a point-to-point fashion if there are not
enough users to justify the high power transmission. A typical example in 3GPP
has been the sport results service where, for example, ice hockey results would
be available as well as video clips of the key events in different games of the
day. Charging is expected to be applied for the multicast mode.
From the radio point of view, MBMS is considered an application
independent way to deliver the MBMS User Services, which are intended to
deliver to multiple users simultaneously. The MBMS User Services can be
classified into three groups as follows
1. Streaming services, where a basic example is audio and video
stream;
2. File downloads services;
3. Carousel service, which can be considered as a combination of
streaming and file download. In this kind of service, an end user may have an
application which is provided data repetitively and updates are then broadcast
when there are changes in the content.
For MBMS User Services, an operator controls the distribution of
the data. Unlike CBS, the end user needs first to join the service and only
users that have joined the service can see the content. The charging can then
be based on the subscription or based on the keys which enable an end user to
access the data. The MBMS content can be created by the operator itself or by a
third party and, as such, all the details of what an MBMS service should look like
will not be specified by 3GPP, but left for operators and service providers.
One possible MBMS high level architecture is shown in Figure, where the IP
multicast network refers here to any server providing MBMS content over the
Internet.
