Hi, I'm currently trying to get a hang of the OFDM-internals and I'm stuck in gr_ofdm_mapper_bcv. I hope someone might be able to enlighten me...
First of all, how exactly does gr_ofdm_mapper_bcv decide which carriers are used? I really, really hate having to ask this kind of question when I have the source code right here, but - with all respect to the authors - I find some of the code pretty obscure. Say I want to use an IFFT length of 16 (for academic reasons). A call like gr.ofdm_mapper_bcv(constellation, 2, oc, 16) will always throw an exception unless oc is 14 or 16. Using 8 subcarriers should not be a problem physically? What's the rule of possible combinations of FFT-length occupied carriers? Next, I noticed that the DC carrier(s) are left unused. Logically, this should happen in gr_ofdm_mapper_bcv, but I can't really find where. However, this is slightly confusing: say you set options.occupied in ofdm_mod to 200, then what you really get are 198 occupied subcarriers, or am I mistaken? By the way, why can't I use try:except to catch an instance of 'std::invalid_argument'? Is this a SWIG-problem? Thanks for any insight you may have! Cheers, MB -- Dipl.-Ing. Martin Braun Phone: +49-(0)721-608 3790 Institut fuer Nachrichtentechnik Fax: +49-(0)721-608 6071 Universitaet Karlsruhe (TH) http://www.int.uni-karlsruhe.de/
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