In current MBMS system, the BM‑SC, MBMS-GW and MME are located in the Core Network. The backhaul delay between the BM‑SC and the eNB is non-negligible when calculating the end-to-end delay, especially when MBMS is used to delivery downlink V2X messages in the V2X system. To minimize the latency, possible deployment can consider the following options:
To move the MBMS CN functions (e.g. BM‑SC, MBMS-GW) closer to the eNB.
To move the user plane of MBMS CN functions (BM‑SC, MBMS-GW) closer to the eNB.
These options are illustrated in clause B.2
and clause B.3
. The list of deployment options is not exhaustive and that they are shown for illustration purposes only.
If the V2X Application Server utilizes xMB interface, the options B.2 and B.3 replace MB2‑C and MB2‑U with xMB‑C and xMB‑U respectively.
In this case BM‑SC, and MBMS-GW are located close to the eNB. This option is shown in Figure B.2-1
In this case user plane of MBMS CN functions (BM‑SC and MBMS-GW) is located close to the eNB. This option is shown in Figure B.3-1
The user plane of MBMS CN functions can implement the following user plane functionalities:
Receive user data from V2X Application Server over MB2‑U.
IP multicast distribution of MBMS user plane data to E-UTRAN (M1 reference point).
Data synchronization (as for the BM‑SC in legacy MBMS mechanisms).
If used, apply favourable error resilient schemes, e.g. specialized MBMS codecs or Forward Error Correction schemes.
If used, MBMS data encryption.
The procedure for Local MBMS based MBMS data delivery described in clause 126.96.36.199
makes this type of deployment option possible to improve V2X latency.
The separation of control and user plane functions in this option is for illustration only.