Created attachment 1961 [details]
LOG traces of the AM RLC entity with some comments

Hi, my name is Imen, I am using the Lte module of ns3.21 to simulate a simple downlink UDP packet transmissions with AM RLC model. But I have encountered some problems with the RLC layer: It doesn't send all the packets of the transmission buffer "all the time", I mean that depends on the number of packets sent from the remote server. 

1-for 15 pckts of 100 bytes ==> 15 pckts are received by the application layer of the UE

2-for 20 pckts of 100 bytes ==> 15 pckts are received by the application layer of the UE

3-for 100 pckts of 100 bytes ==> 94 pckts are received by the application layer of the UE

I tried to follow the problem with the LOG traces, I found that the AM RLC stopped caling the DoNotifyTxOpportunity function after having all transmitted from the REtransmission buffer even if there were pending pckts on the transmission buffer. I don't know if it's really a bug or there is something escaping me. 
   
I have attached below my LOG file with some comments.