Reply To: BLER Error in Uplink Link Level Simulator using multisim

#5802

Hi,

I thought simulation.parameter_scripts = {‘examples/load_params_doc_antenna’}; means it only runs load_params_doc_antenna.m script ?

Yes, when you are using this line, only the specified parameter script is used where you have to adjust all parameters accordingly.

Why sometimes my BLER plot will show vertical straight line and sometimes show zero value ? Is it possible to get vertical straight line ? I guess zero value is acceptable.

I think the vertical straight lines you are referring to are the 95% bootstrap confidence intervals, indicating the simulated value’s confidence. In case this vertical line is very big, only a insufficient number or errors was found and the corresponding BLER cannot be calculated with high confidence. This usually happens when simulating to high SNR with a small number of subframes. For example, when you expect a BLER of 0.01 and you simulate 1000 subframes, there are only 10 frame errors found from which the BLER is calculated.

Can i explain it by saying using CQI Feedback set to false means CQI value is fix , so is the modulation order and thus the error keeps reducing while SNR increases ?

Yes, exactly. The feedback mechanism tries to maximize the throughput while maintaining a BLER of approximately 0.1 by selecting a proper CQI value. When disabling the feedback and simulating with a fixed CQI, the BLER will be very high at low SNR but decreases rapidly with SNR.

I also want to ask about the LTE_params.ChanMod_config.type like PedA, PedB , VehA, TU and so on. However, i cannot find any information about them with the documentation file as well as online resource. Is that any way i can approach ?

You can find two references for channel models in the simulator documentation. Specifications of channel models can be found in http://www.etsi.org/deliver/etsi_tr/125900_125999/125943/07.00.00_60/tr_125943v070000p.pdf and https://www.itu.int/dms_pubrec/itu-r/rec/m/R-REC-M.1225-0-199702-I!!PDF-E.pdf .

Last but not least, the uplink version i used is the latest version which is v1.5. I use 20 MHz bandwidth because it is a standard bandwidth used in the operator company here.

I understand, however, since almost all results scale with the employed bandwidth, I recommend to use the lowest bandwidth for simulations in order to save time.

greetings
Stefan