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B.2.5.7 MBSFN TRANSMISSION<br />
The current understanding is that the MBMS support can be provided with single frequency network<br />
mode of operation (MBSFN). This mode of operation is characterized by synchronous transmission by all<br />
of the eNBs that are participating in the MBMS service. The content is synchronized across the eNBs by<br />
synchronizing the radio frame timing, common configuration of the radio protocol stack and usage of a<br />
SYNC protocol in the core network. Studies have shown that MBSFN transmission can significantly<br />
improve the downlink spectral efficiency over that of a single cell transmission.<br />
In LTE, MBMS is transmitted in the MBMS service area, which is mapped to one or multiple MBSFN<br />
areas. All the cells in one MBSFN area transmit the same content with the uniform radio resources<br />
(Figure B.8).<br />
Figure B.8. Diagramatic Representation of the MBMS Service Area.<br />
To support the MBSFN transmission, the SYNC protocol is introduced to LTE, the SYNC protocol layer is<br />
located in the BM-SC and eNB as shown in Figure B.9.<br />
UE<br />
MBMS<br />
packet<br />
RLC<br />
MAC<br />
PHY<br />
RLC<br />
MAC<br />
PHY<br />
eNB<br />
TNL<br />
MBMS<br />
Gateway<br />
www.4gamericas.org February 2011 Page 134<br />
M1<br />
TNL<br />
BM-SC<br />
MBMS<br />
packet<br />
SYNC SYNC<br />
TNL<br />
SYNC: Protocol to synchronise<br />
data used to generate a certain<br />
radio frame<br />
Figure B.9. Location of the SYNC Protocol in the Network.
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