Multimedia Broadcast Multicast Service(MBMS)

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Multimedia Broadcast Multicast Service

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Multimedia Broadcast Multicast Service (MBMS) is a broadcasting service that can be offered via existing GSM and UMTS cellular networks. The infrastructure offers an option to use an uplink channel for interaction between the service and the user, which is not a straightforward issue in usual broadcast networks, as for example conventional digital television 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.

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 256kbit/s per MBMS Bearer Service and between 800kbit/s and 1.7Mbit/s per cell/band. The actual cell capacity depend 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 downlink direction. The actual datarate 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.

MBMS is believed to be currently under active evaluation by Mobile Network Operators as a means of delivering Mobile Television to the mass market. Competing technologies include DVB-H, DMB and EPM-DAB. However due to spectrum availability and the cost of building new broadcast infrastructure these technologies may not be viable. On the other hand, there have already been some DMB and DVB-H trials ongoing, like those during the football championships 2006 in Germany vs. no field tests of MBMS in the same timeframe. So it seems the competing technologies have a time to market advantage.

[edit] 3GPP Technical Specifications

MBMS Bearer Service (Distribution Layer):

3GPP TS 22.146 Multimedia Broadcast/Multicast Service (MBMS); Stage 1

3GPP TS 23.246 Multimedia Broadcast/Multicast Service (MBMS); Architecture and functional description

3GPP TS 25.346 Introduction of the Multimedia Broadcast/Multicast Service (MBMS) in the Radio Access Network (RAN); Stage 2

3GPP TS 43.246 Multimedia Broadcast/Multicast Service (MBMS) in the GERAN; Stage 2

3GPP TR 25.803 S-CCPCH performance for Multimedia Broadcast/Multicast Service (MBMS)

MBMS User Service (Service Layer):

3GPP TS 22.246 Multimedia Broadcast/Multicast Service (MBMS) user services; Stage 1

3GPP TS 26.346 Multimedia Broadcast/Multicast Service (MBMS); Protocols and codecs

3GPP TR 26.946 Multimedia Broadcast/Multicast Service (MBMS) user service guidelines

3GPP TS 33.246 3G Security; Security of Multimedia Broadcast/Multicast Service (MBMS)

3GPP TS 32.273 Telecommunication management; Charging management; Multimedia Broadcast and Multicast Service (MBMS) charging

[edit] See also

• Mobile TV
• DVB-H
• MediaFLO