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Is eMBMS data cyphered ?

+3 votes

When eMBMS gateway sends data to eNodeB then does eNodeB cyphered data or not. Suppose a set of user (known as multi casting) is on going then would PDCP be performed ROHC and cyphering or not for that set of users ?

posted Sep 9, 2013 by Vikram Singh

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In my understanding MCCH/MTCH data is transperent to PDCP layer. 3GPP 36.323 doesnt talk about MCCH/MTCH data processing at all.
Only RLC UM mode with 5 bit SN and t-reordering is 0. As its multicast data without ARQ so applying ROHC doesnt make sense.

1 Answer

+1 vote

Ideally yes, eMBMS sits in the core network and connection between MME and eNodeB is secure so on the similar lines eNodeB and eMBMS should also be the same. otherwise there would be a issue with the concept of RAN operator and Core Network operator.

answer Sep 9, 2013 by Luv Kumar
eNodeB and MME has control plane. when SGW sends data to eNodeB in point to point communication (normal data flow) . PDCP performs encryption and ROHC of the received packet since a Keyrrc encryption is applicable to an UE. this query is little bit related to key generation part. Since Keyrrc encryption is per user basis then how a mulitcast data can be cyphered by eNodeB ? since in multicasting and broadcasting a data over the radio is access by set/all users from the same place(same resource blocks). Now question how data is being protected by eNodeB ? is it a different Key all together to protect multicast data or eMBMB gateway do some thing to secure multicast data ?
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0 votes

One question came out and want to get answer for that just to avoid assumptions what I have.
A multiple MBMS services are being transmitted over the air through eNodeBs belong to one MBSFN Area. Here I considered all the eNodeBs belongs to that particular MBSFN area have maximum six sub frames of a radio frame to broadcast the content and all eNodeBs are doing.
In between some of the eNodeBs belong to same MBSFN Area get congested and out of 6 sub frames only two subframes are being used in those eNodeB.
My first question where exactly things will be affected ?
Another question, MBMS-GW will be sending data in same speed with same SYNC information. Since few eNodeBs are congested then how data will be transmitted ? Segmentation at eNodeB RLC may affect User experience since UE combines the data in MBMS case from all the neighboring eNodeBs and get better result in term of quality.
If one eNodeB is sending data without segmentation and the other one is sending with segmentation then How UE RLC will behave and what will be the user experience ?

Please ignore these question if segmentation and reassembling is not applicable for MBMS data transmission at RLC.

0 votes

In case of UE specific data transmission MAC layer allocates radio resources on dynamic basis. When we say dynamic resource allocation it means in each TTI (subframe) different amount of data is sent over the over considering various factor QCI, amount of data buffered at RLC and available radio resource.
What about the MBMS data transmission. MBSFN subrames are fixed in radio frame for the MBMS data transmission. Is there really need of any dynamic resources allocation for the MBMS data comes from RLC layer or it is persistent since required modulation and coding other parameters are already known at the time of bearer establishment and these parameters does not change throughout the data transmission of MBMS data.