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LTE: What type of data is considered for transparent mode (TM) transmission in LTE 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 ?

posted Oct 1, 2016 by Rupam

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2 Answers

0 votes

RLC layer support three mode of transmission in LTE radio stack. These three modes are transparent mode (TM), un-acknowledge mode (UM) and acknowledge mode (AM). In case of transparent mode, RLC layer does not put any header. It does not apply segmentation and re-assembling for RLC SDUs.

BCCH/PCCH/CCCH logical channels information is carried out using the transparent mode.

answer Oct 2, 2016 by Harshita
0 votes

Hi rupam,

RLC entity is per LC basis. Each LC will have one entity. As harshitha said BCCH/PCCH/CCCH will be TM mode. Remaining LC's base on OAM(operator) configuration ENB will select the operation mode.

answer Oct 3, 2016 by Jaganathan
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+1 vote

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 ?

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.

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