Re: Implementation of OFDM TX and RX using GNURadio and USRP

On 27/11/2022 16:05, Daniel Estévez wrote:
> On 27/11/2022 17:23, Marcus D. Leech wrote:
>> On 27/11/2022 05:26, Daniel Estévez wrote:
>>>
>>> Hi,
>>>
>>> Another option for extracting one or a range of items from a vector
>>> is to use Vector to Stream followed by Keep 1 in N or Keep M in N.
>>> See near the bottom of this flowgraph for an example:
>>>
>>> https://github.com/daniestevez/reu-2022/blob/main/polyphase/polyphase_filter.grc
>>>
>>>
>>> Best,
>>> Daniel.
>>>
>> That would only allow the first or first-N of the streams to be
>> captured, rather than some arbitrary single stream, no?
>
> No, because these blocks have an initial offset parameter (and if they
> didn't, we could use "Skip Head"). As an example, say that we have
> 1024-point FFTs given as vectors and we only want the FFT bin number 42.
>
> We do vector to stream, then Keep 1 in N with N = 1024 and initial
> offset = 42. This would give us a stream where only the FFT bin number
> 42 appears.
>
> Now say that w want FFT bin numbers 42, 43, 44, 45. We do vector to
> stream, then Keep M in N with N = 1024, M = 4, initial offset = 42.
> This would give us a stream that contains:
>
> bin_42(t0), bin_43(t0), bin_44(t0), bin_45(t0), bin_42(t1),
> bin_43(t1), bin_44(t1), bin_45(t1)...
>
> If desired, we can turn this into vectors of 4 elements using stream
> to vector or use a deinterleave block to separate each of the bins in
> its own stream.
>
> Best,
> Daniel.
>
Hah!  I've used "Keep One in N" and "Keep M in N" for *years*, and never
noticed that!   Color me chagrined.....