|
From: | BHN66 |
Subject: | Re: [Discuss-gnuradio] problem with ofdm bandwidth and sampling rate |
Date: | Fri, 5 Jun 2015 11:22:46 +0200 |
hi felix,i have tried it with the resampler block but it didn't work well.on the tx side i have used it to resample from 11khz, which i need for my 10khz bandwidth, to 48khz. on the rx side i can see the spectrum with 48khz and the bandwidth of my signal still remains at 10khz (as requested). the problem is that i can't detect any signal at rx side. when i adjust both parts (tx and rx) with a sampling rate at 11khz it works.for better understanding i have attached my flowgraphs and sink outputs.alphonsoGesendet: Donnerstag, 04. Juni 2015 um 23:40 Uhr
Von: "Wunsch, Felix (CEL)" <address@hidden>
An: "address@hidden" <address@hidden>, "address@hidden" <address@hidden>
Betreff: Re: [Discuss-gnuradio] problem with ofdm bandwidth and sampling rateOn 03.06.2015 17:29, address@hidden wrote:Well, the measurable on-air bandwidth is always defined by the speed/rate at which your soundcard processes your digital samples. If you remember that B ~ 1/T and that the rate of your soundcard controls T it becomes obvious that changing the sample rate changes the bandwidth. If you don't want that, you could use a resampler that adapts its resampling ratio to the sampling rate of the soundcard.hello felix,>>please remember to always reply to the list.i'm sorry, i'm new at this. i have checked my configuration and i hope it works the next time.to mix up the baseband signal to 12khz or higher to short wave (3-30mhz) should be the same procedure. i have tested it by using a multiply block and a signal source block as the carrier frequency.but there is an other question: if i configured my system as described, can i be sure that the bandwidth of each sub carrier has the bandwidth and symbol duration as shown by the equations?used_bw = occupied_carriers * dfdf = used_bw / occupied_carriers = 10khz / 228df = 43.86hz --> tsym = 22.8msit's very confusing why i have to adjust my used bw by changing the sampling rate. when i follow the equations and the standard i choose one mode (RM A, SO 3). that means i have to use 228 carriers
and have a symbol duration with 24ms which leads to 41.66hz carrier spacing. so the used bw is 228 * 41.66hz = 9.5khz (approx. 10khz). this bw should be fix and should not change by the sampling rate.sorry for the maybe silly questions but i want to keep on that stuff.
Felix@Marcusyou mean if there were pilots for a channel estimation in the transmitted signal?alphonso-- Karlsruhe Institute of Technology (KIT) Communications Engineering Lab (CEL) Felix Wunsch, M. Sc. Research Associate Kaiserstraße 12 Building 05.01 76131 Karlsruhe Phone: +49 721 608-46276 Fax: +49 721 608-46071 E-Mail: address@hidden www.cel.kit.edu KIT -- University of the State of Baden-Württemberg and National Laboratory of the Helmholtz Association
-- Karlsruhe Institute of Technology (KIT) Communications Engineering Lab (CEL) Felix Wunsch, M. Sc. Research Associate Kaiserstraße 12 Building 05.01 76131 Karlsruhe Phone: +49 721 608-46276 Fax: +49 721 608-46071 E-Mail: address@hidden www.cel.kit.edu KIT -- University of the State of Baden-Württemberg and National Laboratory of the Helmholtz Association
[Prev in Thread] | Current Thread | [Next in Thread] |