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LTE: Does RLC segmentation and reassembling applicable for MBMS data ?

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MBMS Data receives from MBMS-GW to eNodeB module interfacing towards MBMS-GW. It removes GTP-U header and sends data to lower layer i.e RLC. As per my understanding so far, RLC does segmentation and re-assembling for the received upper layer PDU to make it fit into MAC PDU. Now I want to know, Does the same concept applicable for MBMS data also or for RLC it is transparent mode transmission.

Which format is used by RLC for the MBMS transmission ?

posted Nov 13, 2016 by Rupam

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1 Answer

+1 vote

I have minimal information to share on MBMS logical channels. MCCH and MTCH both logical channels are mapped to RLC UM mode. RLC UM mode transmission is used for delay sensitive services and also when data flow direction is uni directional such as MTCH (point to multi-point transmission) . Though RLC UM entity supports segmentation and re-assembling, I think this is not applicable for MCCH and MTCH since there is a parameter "UM_Window_Size". Value of this parameter is set to zero for MCCH and MTCH. I am still not fully confirmed.

answer Nov 16, 2016 by Vimal Kumar Mishra
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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.

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.

+1 vote

RLC is one of the L2 layer in LTE radio protocol stack. It does many functions such as segmentation, re-assembling and along with that it supports various transmissions mode like transparent mode, acknowledgement mode and un-acknowledgement mode.
Now I want to understand for which type of RLC SDUs and PDUs transparent mode transmission is used.
Does the RLC create single RLC entity at cell level or at the UE level or at the bearer level ?

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