Multimedia Broadcast Multicast Service (MBMS)
This is a broadcasting service that can be offered via existing GSM and UMTS cellular networks and it also offers an option to use an uplink channel for interaction between the service and the user, which is not a common issue in the usual broadcast networks, like the conventional digital television which is only a one-way (unidirectional) system. MBMS uses multicast distribution in the core network instead of point-to-point links for each end device. Features of MBMS include MBMS Bearer Service and the MBMS User Service.
The MBMS Bearer Service uses IP Multicast addresses for the IP flow. The plus of the MBMS Bearer Service over the legacy UMTS bearer services (interactive, streaming, etc) is that the transmission resources in the core- and radio network are shared. The flow of one MBMS packet is replicated by GGSN, SGSN and RNCs. MBMS may use an advanced counting scheme to decide, whether one or more dedicated ( i.e. unicast) radio channels lead to a more efficient system usage over one common (i.e. broadcast) radio channel.
UTRAN MBMS offers up to 256kbit/s per MBMS Bearer Service and between 800kbit/s and 1.7Mbit/s per cell/band. The actual cell capacity depends on the UE capabilities. GERAN MBMS offers between 32kbit/s and 128kbit/s. Up to 4 GSM Timeslot may be used for one MBMS bearer in the downlink direction. The actual data rate per Traffic Slot depends on network dimensioning.