For RRC Re-establishment Procedure, what are Functionlities in Layer-2 ?

Question

What procedures effect in (MAC,RLC and PDCP) ???

Please help to make note of functionalities effected in LTE layer-2 when RRC re-establishment triggers?

Answer 1

Hi sripathi,

Actually Re-establishment is triggered From Layer 2 to RRC, then RRC to EnodeB RRC. RLC is the responsiblity to trigger re-establishment. when to trigger is implementation specific. One scenario is In RLC AM mode if MAX ARQ transmission happens and still Data got NACK means it wil trigger re-establishment to RRC.

Comments

Hi Jaganath,

The scenario which you mentioned, its nothing but when RLF Happens triggering Reestablishment.... in that case, What MAC or RLC functionalities when it triggers reestablishment ?

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RLC will send only when it reachs MAX Tx count, It may be because of RLF or protocol mis configuration, or any other reason. It is not only on RLF.  MAC functionality is nothing for re establishment.

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what about MAC reset and RLC reset ...and maintaining sequence number in RLC ?

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After re establihment RRC will re configure all layers with new configuration , so what ever the state of UE in RLC and MAC will be re setted.

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In this case(re-set), how can we maintain sequence number of already processing data in RLC ... how can we maintain it in next transmissions?

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No , after re establishment all old satate will be deleted , It will start as a first transmission