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Re: [Discuss-gnuradio] channel model question

 From: John Andrews Subject: Re: [Discuss-gnuradio] channel model question Date: Mon, 28 Jun 2010 15:56:56 -0700

But still there is a problem. 1000/100,000 = 0.01 so the channel_model must consume 100,000 samples coming into it to represent an offset of 1000Hz. How, does it know how many samples to consume as the ratio can be the same for a different combination such as 100/10000.

If x(i) = sin(2*pi*freq_offset_ratio*i) , i must vary from {1,sampling_rate}.

On Mon, Jun 28, 2010 at 3:00 PM, Josh Blum wrote:
For some reason, the channel model's frequency_offset is not in Hz. Rather its a fraction of the sample rate. You should pass in my_offset_in_hz/my_sample_rate to this parameter.

The signal source works like that. I suppose that means that the sample rate and frequency are redundant because you really only care about the ratio between them.

_josh

oh consistency...

On 06/28/2010 02:12 PM, John Andrews wrote:
Hi,
I have a nagging doubt about how the channel model is implemented in
gnuradio. Suppose I have an input signal entering the channel model at
100,000 samples/sec. Let's say the channel model has to add an offset of
1000Hz to the input signal. Then I must have 100,000 samples of a 1000Hz
SINE_WAVE signal and multiply each input sample with a corresponding input
sample. Am I right? If I am right then i don't see this happening here with
the sampling rate given as 1 in the line below

d_freq_offset = gr_make_sig_source_c(1, GR_SIN_WAVE, frequency_offset, 1.0,
0.0);

If I am wrong then will someone please correct me here.

thank you very much
John

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