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How NAS messages are transported between the UE and the MME.

0 votes

When the MME sends a DL NAS message is the connection between MME and UE held long enough just to receive the message ? What happens if there are back-to-back NAS messages to be delivered, does the the UE open a connection to MME and receive all the messages at once. Or does it open close the connection to get each of the messages separately.

posted Aug 21, 2014 by anonymous

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2 Answers

+1 vote

MME doesn't have a direct connection with the UE. MME is connected to enodeB via S1 interface and enodeB to UE on Uu

  1. NAS message transferred from MME to enodeB on S1 interface (downlink NAS transport) and enodeB forword this message to UE in a encapsulated way in RRC message.

  2. all NAS messages forwarded one by one from MME to enodeB to UE and vice-versa.

  3. If UE is in Idle mode then RRC connection is established first then message is forwarded.

answer Aug 22, 2014 by Salil Agrawal
0 votes

If MME is sending "NAS massage" to an UE by using S1-AP "Downlink NAS Transport" , it means UE is connected with MME/Network. When an UE is not connected to network and network wants to send any message, it initiates paging for that UE. There is an User Inactivity timer which runs at eNodeB, it significance is that if there is no data trans/receive to/from UE, release the rrc connection and also informs to MME.

answer Aug 21, 2014 by Harshita
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+4 votes

There are couple of procedures are defined which consist of NAS as well as RRC signalling messages exchange.
Some of the NAS message sends to an UE through RRC Connection Reconfiguration message as piggybacked and some as DL Info transfer.

I want to know, Is there any procedure exists in lte when an UE receives RRC Connection Reconfiguration along with NAS message and responds back to network with NAS message first and then Reconfiguration Complete to eNodeB.

Usually, I saw UE sends RRC Connection Reconfiguration Complete message first then NAS response message.

0 votes

Does NAS messages affected while doing Hand over procedure in LTE or 5G ?

+3 votes

When this message is sent by Network to an UE ? There are couple of optional IEs within the message, what significance of their presence within the message ?

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