Technical Description
The MBMS feature is split into the MBMS Bearer Service and the MBMS User Service. The MBMS Bearer Service includes a Multicast- and a Broadcast Mode. The MBMS Bearer Service uses IP multicast addresses for the IP flows. The advantage of the MBMS Bearer Service compared to legacy UMTS bearer services (interactive, streaming, etc.) is, that the transmission resources in the core- and radio network are shared. One MBMS packet flow is replicated by GGSN, SGSN and RNCs. MBMS may use an advanced counting scheme to decide, whether or not zero, one or more dedicated (i.e. unicast) radio channels lead to a more efficient system usage than one common (i.e. broadcast) radio channel.
UTRAN MBMS offers up to 256 kbit/s per MBMS Bearer Service and between 800 kbit/s and 1.7 Mbit/s per cell/band. The actual cell capacity depends on the UE capabilities. GERAN MBMS offers between 32 kbit/s and 128 kbit/s. Up to 4 GSM timeslot may be used for one MBMS bearer in downlink direction. The actual data rate per Traffic Slot depends on network dimensioning.
The MBMS User Service is basically the MBMS Service Layer and offers a Streaming- and a Download Delivery Method. The Streaming Delivery method can be used for continuous transmissions like Mobile TV services. The Download Method is intended for “Download and Play” services. To increase the transmission reliability, an application layer FEC code may be used. Further, a file-repair service may be offered to complement the download delivery method.
MBMS has been standardized in various groups of 3GPP (Third Generation Partnership Project), and the first phase standards are found in UMTS release 6. As Release 6 was functionally frozen by the 3rd quarter of 2004, practical network implementations may be expected by the end of 2007, and the first functional mobile terminals supporting MBMS are estimated to be available by also end of 2007.
Read more about this topic: Multimedia Broadcast Multicast Service
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