How TM mode switching is happen at eNB and on what basis eNB change the transmission mode (TM) in LTE?

Question

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 ?

Answer 1

Hi,

TM mode switching is based on the UE capability and UE feedback of channel condition. Like in TM4 if UE faces poor channel quality then ENB will do transmit diversity in TM4 but it will not change TM mode to 2 because in TM4 itself we can use transmit diversity. But it is implementation specific if you want to switch TM mode in above scenario then you can switch to TM2.