Bugzilla – Bug 2095
Wrong values in default-traces.h
Last modified: 2015-05-02 15:53:40 UTC
Created attachment 2015 [details] Original default-traces.h file in ns-3.22 I have observed wrong OFDM traces in default-traces.h, which have been made with an external OFDM simulator(IT++). In the modulation 4 (16QAM 3/4) the BER values are abnormally high and the table lenght is not long enough. The problem begins in the line: 257 static const double modulation4[6][115] = { .... } The file is src/wimax/model/default-traces.h Adtionally I am using an alternative default-traces.h with OFDM traces belonging to the 64QAM 1/2 traces (my simulations do not require accurate phy model), and the results of throughput are much more logical and precise with this modulation 4. I attach both default-traces.h
Created attachment 2016 [details] Modified default-traces.h file which gives normal values
Thank you for providing patches. Can you document any more how these new values were obtained, and can we leave a comment about this in the header file? Would it be correct to summarize this as: "Fix OFDM modulation values for 16QAM 3/4 coding in the WiMax module" or if not, can you provide another summary statement that better captures what has changed in the model?
Originally, I only copy-pasted from modulation5 to modulation4, since for me was enough. However, in order to try obtain a less clumsy method, I have simulated new traces for modualtion4 with It++. I attach the figure ber-snr-values.png which sumarize the problem. Modulation4 never reaches values close enough to zero, so the BER and BLER were always to high. I have contacted with the original authors, but none of them reminds or have anything of the simulator used originally. So instead of use the complex environment used originally (solomon-reed, interleaving and TDL channel) I have simulated a simple scenario with AWGN channel. Maybe is not completely alike to the real world, but at least it improve the older default-traces-h and make the module more usable. I attach the new default-trace.h as patch whith a brief description.
Created attachment 2023 [details] Image with the BER-SNR relationship used in thw WiMAX module Image with the BER-SNR relationship used in thw WiMAX module
Created attachment 2024 [details] Proposed patch for fix default-traces.h Proposed patch for fix default-traces.h in ns-3.22. The only changes made are the header with the changes performed and the traces for modulation4 (16 QAM 3/4)
Comment on attachment 2024 [details] Proposed patch for fix default-traces.h It can be applied from the ns3.22 main working directory with patch -p2
changeset: 11344:c0f16f16643d