SimuLTE: D2D message flow

[kazola]

Dear,
I am trying to understand the message flow for a node sending a D2D packet to another node.
Maybe due to repetitions or so, but I am not able to clearly identify the RAC, RAC (grant), SRB, SRB (grant) sequence in the following OMNET eventlog for this multicast data communication. Why there are repetitions of the same message?
The last packet, the data one, is clear to me, arriving both eNode and the other node.
I am curious about your opinion. Have a nice day.

[Giovanni Nardini]

Hi,

I put some notes on your picture:

1) the UE sends the RAC request to the eNodeB

2) the eNodeB sends the reply corresponding to the RAC request. This reply only informs the UE that it won the contention. This is not a resource grant.

3) the eNodeB sends a first resource grant to allow the UE to send the BSR

4) the UE sends the BSR to the eNodeB using the granted resources.

Now, the eNodeB has to decode the received BSR. This requires some TTIs

5) the eNodeB sends a second resource grant to allow the UE to perform the transmission

6) the UE finally performs the multicast transmission using the above grant.

Message 1b is the beginning of a second RAC request that will follow the same steps.

Hope this helps.

Giovanni