Runtime error on LTE-EPC simulation and documentation mistakes

[Einar César]

Dear colleagues,

I've read and follow instructions on user documentation found at http://www.nsnam.org/docs/release/3.20/models/html/lte-user.html to write a basic LTE-EPC simulation.

If I wouldn't mistaken, there are some things to correct on documentation (ns-3.20) and errors when running the code.

First, there is no method ActivateEpsBearer() to call in LteHelper class instance anymore as shown in documentation:

lteHelper->ActivateEpsBearer (ueLteDevs, EpsBearer (EpsBearer::NGBR_VIDEO_TCP_DEFAULT), pf);

As stated in documentation, default bearer is automatically activated in LteHelper::Attach() method. I create dedicated bearer calling lteHelper->ActivateDedicatedEpsBearer() in code attached on this message.

After write a test code (with some adjustments) I've got a following error on debugging:

Program received signal SIGSEGV, Segmentation fault.
0xb7965e11 in ns3::LteUePhy::DoSetDlBandwidth (this=0x8099560, dlBandwidth=6 '\006') at ../src/lte/model/lte-ue-phy.cc:1129
1129          m_downlinkSpectrumPhy->GetChannel ()->AddRx (m_downlinkSpectrumPhy);

Can someone help on this? What I'm doing wrong? I'm new on LENA model and I may don't know some basics. Sorry for bad english too.

Thanks for listening!

Regards!

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________________________________

Einar César Santos

MSc. Engenharia Elétrica

B.el Análise de Sistemas

[Nicola Baldo]

On Thursday, July 31, 2014 3:39:48 PM UTC+2, einarcesar wrote:

Dear colleagues,

I've read and follow instructions on user documentation found at http://www.nsnam.org/docs/release/3.20/models/html/lte-user.html to write a basic LTE-EPC simulation.

If I wouldn't mistaken, there are some things to correct on documentation (ns-3.20) and errors when running the code.

First, there is no method ActivateEpsBearer() to call in LteHelper class instance anymore as shown in documentation:

lteHelper->ActivateEpsBearer (ueLteDevs, EpsBearer (EpsBearer::NGBR_VIDEO_TCP_DEFAULT), pf);

This was already fixed in the dev tree:
http://www.nsnam.org/docs/models/html/lte-user.html#evolved-packet-core-epc
Anyway, thanks for reporting it!

 

As stated in documentation, default bearer is automatically activated in LteHelper::Attach() method. I create dedicated bearer calling lteHelper->ActivateDedicatedEpsBearer() in code attached on this message.

After write a test code (with some adjustments) I've got a following error on debugging:

Program received signal SIGSEGV, Segmentation fault.
0xb7965e11 in ns3::LteUePhy::DoSetDlBandwidth (this=0x8099560, dlBandwidth=6 '\006') at ../src/lte/model/lte-ue-phy.cc:1129
1129          m_downlinkSpectrumPhy->GetChannel ()->AddRx (m_downlinkSpectrumPhy);

Can someone help on this? What I'm doing wrong? I'm new on LENA model and I may don't know some basics. Sorry for bad english too.

A couple of suggestions:

• try to look in gdb's backtrace if you can trace the error back to your code
• if not, try to compare carefully your program with the user docs and with the example programs in src/lte/examples, to find out what you are doing wrong. For example, often the order in which you perform configurations matters a lot.
  

[Einar César]

Thanks for reply!

Yeah, I looked the backtrace before. The problem arise on Attach() method, but I just don't know why it happens yet. Still investigating... Follow backtrace for information:

#0  0x0059568f in ns3::LteUePhy::DoSetDlBandwidth (this=0x80d74c8, dlBandwidth=6 '\006') at ../src/lte/model/lte-ue-phy.cc:1129
#1  0x005953be in ns3::LteUePhy::DoSynchronizeWithEnb (this=0x80d74c8, cellId=1) at ../src/lte/model/lte-ue-phy.cc:1096
#2  0x00595121 in ns3::LteUePhy::DoSynchronizeWithEnb (this=0x80d74c8, cellId=1, dlEarfcn=100) at ../src/lte/model/lte-ue-phy.cc:1078
#3  0x005a2340 in ns3::MemberLteUeCphySapProvider<ns3::LteUePhy>::SynchronizeWithEnb(unsigned short, unsigned short) () from /home/einar/Download/ns-allinone-3.20/ns-3.20/build/libns3.20-lte-debug.so
#4  0x00601acd in ns3::LteUeRrc::DoForceCampedOnEnb (this=0x80d7ee8, cellId=1, dlEarfcn=100) at ../src/lte/model/lte-ue-rrc.cc:580
#5  0x00629800 in ns3::MemberLteAsSapProvider<ns3::LteUeRrc>::ForceCampedOnEnb(unsigned short, unsigned short) () from /home/einar/Download/ns-allinone-3.20/ns-3.20/build/libns3.20-lte-debug.so
#6  0x008e55b1 in ns3::EpcUeNas::Connect (this=0x80d8188, cellId=1, dlEarfcn=100) at ../src/lte/model/epc-ue-nas.cc:165
#7  0x006b5c60 in ns3::LteHelper::Attach (this=0x8091238, ueDevice=..., enbDevice=...) at ../src/lte/helper/lte-helper.cc:706
#8  0x006b59b6 in ns3::LteHelper::Attach (this=0x8091238, ueDevices=..., enbDevice=...) at ../src/lte/helper/lte-helper.cc:692
#9  0x08051306 in main (argc=1, argv=0xbffff534) at ../scratch/lte-test-epc.cc:81

I ask to anyone of you reply with possible cause(s) if you find it. I'll report something new too.

Best Regards!

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[Nicola Baldo]

Hi Einar,

I already told you in the previous email that the often the order in which you perform configurations matters a lot. In your case, you are calling some methods in an unsupported order, which triggers the error. I won't tell you which methods ;-) please follow the user documentation more closely and compare with the existing LTE examples to find out.