TABLE OF CONTENTS In the past, cellular systems have mostly focused on transmission of data intended for a single user and not on broadcast services. Broadcast networks, exemplified by the radio and TV broadcasting networks, have on the other hand focused on covering very large areas and have offered no or limited possibilities for transmission of data intended for a single user. Multimedia Broadcast and Multicast Services, (MBMS), introduced for WCDMA in Release 6, supports multicast/broadcast services in a cellular system, thereby combining multicast and unicast transmissions within a single network.
With MBMS, the same content is transmitted to multiple users located in a specific area, the MBMS service area, in a unidirectional fashion. The MBMS service area typically covers multiple cells, although it can be made as small as a single cell.
Broadcast and multicast describe different, although closely related scenarios:
In broadcast, a point-to-multipoint radio resource is set up in each cell being part of the MBMS broadcast area and all users subscribing to the broadcast service simultaneously receive the same transmitted signal. No tracking of users' movement in the radio access network is performed and users can receive the content without notifying the network. Mobile TV is an example of a service that could be provided through MBMS broadcast.
In multicast, users request to join a multicast group prior to receiving any data. The user movements are tracked and the radio resources are configured to match the number of users in the cell. Each cell...
