hello marcus i connect the usrp“tx and rx pin whit a wire to imitate that no error,so i think the ber should be zero. my problem is that if i want to use uhd_sink and source to test this grc,is there some other work i need to do compare with the connect of virtual sink +source. this is my question : with the connect of virtual sink+source the ber is zero ,i think with the connect of uhd_sink+source the ber should be 0.01 or other number clear to zero,but when i use uhd_sink +source the ber is clear to 1. thank for you reply
--Ekko 2015-11-03 22:49 GMT+08:00 Marcus Müller <marcus.muel...@ettus.com>: > Hi Ekko, > > >difference between uhd_sink+uhd_source with virtual_sink+virtual_source > > uhd_sink / _source talk to radio *hardware*, virtual sink and source are > just "invisible" GRC connections, and simply talk to the block that is > attached to them. > > > in this grc when i use virtual_sink+virtual_source,the ber is zero > > obviously, because it's simply a direct connection, no noise, hence, no > errors. > > > but when i use uhd_sink+uhd_source, and i connect the B200's tx and rx > port with a RF wire. but the ber is not zero. > > Real world radios have noise (and other imperfections), and hence there's > bit errors. That's the core problem of digital communications, and has been > for the last couple of decades. > > > how can i use uhd_sink+uh_source just like virtual_sink+virtual_source > > You can't. One reproduces perfectly, the other is the real RF world. > Getting information across the wireless channel without error is what > science has been working on, and since Shannon we know that you can not > achieve a transmission with arbitrarily low BER over a channel with limited > SNR at arbitrary speed. Every real channel has limited SNR. > > What you do is apply your signal processing and communication theory > skills to counteract the effects of the channel, check correctness and > correct errors (if possible), possibly make the sender retransmit etc; but > you will never break Shannon's limits. > > Best regards, > Marcus > > > On 11/03/2015 01:58 PM, chai E wrote: > > hello all > i have a question about the difference between uhd_sink+uhd_source with > virtual_sink+virtual_source > the accessory is the grc file i am running. > in this grc when i use virtual_sink+virtual_source,the ber is zero ,in > other words,the sorce file is same with the dest file > but when i use uhd_sink+uhd_source, and i connect the B200's tx and rx > port with a RF wire. but the ber is not zero. > i want to konw what is the difference ,and how can i use > uhd_sink+uh_source just like virtual_sink+virtual_source > > > --Ekko > > > _______________________________________________ > Discuss-gnuradio mailing > listDiscuss-gnuradio@gnu.orghttps://lists.gnu.org/mailman/listinfo/discuss-gnuradio > > > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > >
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