NR-U LBT CAM: Negative delay error due to overflow always happens

[George]

Hello!

I am trying to build a simulation for NR-U WiFi. However I can not use the LBT channel access methods as it is always resulting in a negative delay error that looks as follows:

assert failed. cond="delay.IsPositive ()", msg="DefaultSimulatorImpl::Schedule(): Negative delay", +0.413999992s 2 file=../src/core/model/default-simulator-impl.cc, line=235

I cannot get it running for any set of parameters. Can anyone help me with this issue please or at least point me to some files I could look at to fix this issue? Thank you very much!

Kind regards,

George

[Bill Tao]

Hi, George.

My personal experience with Negative delay is that, using the gdb debugger to look at the few function calls that lead up to Schedule() is usually helpful. In particular, you can look at which parameters are used to calculate the delay for Schedule() that results in it being negative.

ns-3 has a wiki page that explains how to use gdb.

Cheers,

Bill.

[George]

Hi Bill,

Thank you very much! I have done what you suggested and it helped me find the problem! 

Kind regards,

George

[Biljana B.]

Hi George,

if you have found the solution to a problem with the negative delay could you please create a MR, so we include it in the official release.

Thanks,

Biljana