Problem in using LTE Rrcreal model with more users

[Thomas Sanders]

Hi,

I am trying to simulate some mobile users in lte multi-cell environment. I am getting error while setting RrcReal model, if I increase the users beyond some extent (7=>8)... Can some one tell me the reason of this or its a bug? does it have something to do with packetmetadata?

assert failed. cond="it != m_teidRbidMap.end ()", file=../src/lte/model/epc-enb-application.cc, line=281 terminate called without an active exception 

While debugging I don't know why the uecontextrelease() method get invoked which erase the teid <> rbid mapping information. Can anyone tell the reason?  

 

Please provide your comments, if possible

Thanks in advance

[Biljana Bojovic]

Hi Thomas,

could you please provide some test script to reproduce?

Thanks,

Biljana

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[Thomas Sanders]

Hi, I have checked the above code it is still not working as the number of users increases... I will be thankful if someone can highlight what is the possible cause of error ?  

Thanks

On Thursday, 17 November 2016 21:00:42 UTC+10, Thomas Sanders wrote:

Thanks for your response, please find the example code attached.

Waiting for your comments

On Thursday, 17 November 2016 19:56:23 UTC+10, Biljana Bojović wrote:

Hi Thomas,

could you please provide some test script to reproduce?

Thanks,

Biljana

On Thu, Nov 17, 2016 at 10:14 AM, Thomas Sanders <sander...@gmail.com> wrote:

Hi,

I am trying to simulate some mobile users in lte multi-cell environment. I am getting error while setting RrcReal model, if I increase the users beyond some extent (7=>8)... Can some one tell me the reason of this or its a bug? does it have something to do with packetmetadata?

assert failed. cond="it != m_teidRbidMap.end ()", file=../src/lte/model/epc-enb-application.cc, line=281 terminate called without an active exception 

While debugging I don't know why the uecontextrelease() method get invoked which erase the teid <> rbid mapping information. Can anyone tell the reason?  

 

Please provide your comments, if possible

Thanks in advance

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[Tommaso Pecorella]

../scratch/lte_simulation.cc:291:30: error: 'InstallSingleEnbDevice' is a private member of 'ns3::LteHelper'

  enbLteDevs.Add (lteHelper->InstallSingleEnbDevice (enbNodes.Get (0)));

                             ^

./ns3/lte-helper.h:603:18: note: declared private here

  Ptr<NetDevice> InstallSingleEnbDevice (Ptr<Node> n);

This error shows that you did modify something in the ns-3 LTE module. Is there something else we need to know and you "forgot" to mention ?

T.

[Thomas Sanders]

Yes! Sorry, to deal with that you can define the InstallSingleEnbDevice as a public member function in lte-helper.h

Or in lte_simulation.cc file just remove the InstallSingleEnbDevice statements and add this,
enbLteDevs = lteHelper->InstallEnbDevice (enbNodes);

Please check now!!!

Thanks

[Tommaso Pecorella]

Hi,

it seems tat your script is a modification of an let example.

I'd suggest to re-start from the example and add selectively your changes to find which one is responsible for the problem.

As an example, I found out that replacing "lteHelper->Attach (ueLteDevs);" with "lteHelper->Attach (ueLteDevs, enbLteDevs.Get (0));" delays the assert (it's still there).

Once you have a minimal change from the example that is triggering the bad behaviour it will be easier to fix the problem.

Keep us updated and open a bug if you find that it's a bug in ns-3.

Cheers,

T.

[Thomas Sanders]

Hi,

Thanks for your reply. Upon investigation, I found that for some users the problem occured when the ConnectionSetupTimeout timer expired which invoked the uecontextrelease method that erase the teid <> rbid mapping information. Can anyone you please tell the reason for this behavior? 

[Biljana Bojović]

Hi Thomas,

seems that the problem that you are facing is due to the fact that the Radio Link Failure (RLF) is not implemented yet in LTE. So it may happen this kind of "unexpected" behavior when handover is used.

So, there are couple of options that you could do:

1) Implement RLF procedure, this would be very welcome by ns-3 community, many people need it.  Some advices by Nicola Baldo how to do it you may find in this thread:
https://groups.google.com/d/msg/ns-3-users/xShe_Hqy6r4/qcytuSEvsvAJ

2) Follow the advices from documentation for how to overcome this issue:
 https://www.nsnam.org/docs/models/html/lte-user.html#tuning-simulation-with-handover

3) Some another possible workaround by increasing the timer settings...

Please let us know whether this helps you solve the issue.

Cheers,
Biljana



he context is released is ok, and it should happen in the cases when signal strength becomes low, but the problem is that there is no RLF procedure that will

[Thomas Sanders]

Thanks for your reply, much appreciated!

As I checked if I change timers, I need to change them all since they all are dependent on each other. 

Anyway, I will check your options further.