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From: | Marcus Müller |
Subject: | Re: [Discuss-gnuradio] Help with GNU Radio Companion |
Date: | Fri, 20 Nov 2015 00:02:11 +0100 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.2.0 |
Hi Antonio,
that is not the "helpdesk"; everyone on the list tries to be as helpful as we can, but it's a mailing list for people of a common interest, GNU Radio in that case, not something that can guarantee a certain reaction. I love to help, though, so here's me, in the middle of the night, answering you. Your mail from ten days ago definitely reached the mailing list. I don't currently have time to discuss it in detail, but considering it hasn't gotten a reply in more than a week, I think it's fair to say you should send another one, but this time improving your questions a little bit: * the GNU Radio companion has a function to save an image of your flowgraph, instead of sending a screenshot of your screen. Use that. * Your flowgraph is not not tidy, and contains a lot of stuff that you don't seem to use. Tidy it up. Remember: the easier you make it for other people to understand your problem, the more likely you'll get good responses. * Don't repeat previous emails without adding information. Seriously, you've sent me the same email personally that you sent to the mailing ten days ago; aside from me having a constant urge to help people, why should the situation have changed since then? Note that I really don't want to scare you away, but increase your chance of getting a good solution. * You're not using the default values in the OFDM mod and demod blocks, if I'm not mistaken. Why are you using exactly those? * You say "the BER is the same"; well, what is "the same"? If I go back and look into one of your screenshots, it's very close to 0.5, right? That's crucial information, and including that in your mail text would make a lot of sense. * You're not really trying to investigate the situation; for example, a BER of 0.5 has a special meaning, which you should know if you're doing your final project on BER curves. * You ask for "correct settings". Well, obviously, "correct" depends on what you're trying to do; it's not like there's one universially correct way to do digital communications (otherwise, the research on that would be pretty dead!). * You have a 32kS/s throttle block in there, but your BER rate block has a window of 20 million samples -- which means that the BER sink accumulates over more than 10 minutes worth of samples; you should explain why you chose that. * There should be the ofdm_loopback.grc example, installed with the other GNU Radio examples. It achieves a 0 BER after the first few samples. Have you compared that to your flow graph? I think if you answer all of the above questions, you can make a pretty good mailing list post. Right now, you're asking "I don't know what goes wrong!"; maybe if you start asking yourself "how does one diagnose this?", you can come up with a way to understand what's going wrong. Maybe start with a data source that is simpler than an image -- what about sending a sawtooth signal? It would be much easier to see in a graphical sink when you display the received signal. Mostly, don't use the old OFDM mod/demod blocks, but the new OFDM transmitter/receiver blocks. Best regards, Marcus On 19.11.2015 23:19, ANTONIO TAMAYO
wrote:
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