Hi Eric,
I now understand what you mean. The rate at which the blocks produce data is solely based on what you want to produce and how you want to produce using the inputs. It has nothing to do with "data rate". Its just how fast your computer can perform the algorithm that's generating the output.
Suppose I consume 1 input item to produce 10 output items the relative rate at which the output is produced is 10 to 1 for each input item consumed. "Data rate" in this case is not what it is for the real world physical rate (e.g. the rate at which data is transfered on a USB). Now the actual rate at which data moves out of the block and onto the USB and to the USRP is entirely dependent upon my computer's abitlity.
If I really want to limit the rate at which the data enters the D/A then I must make the D/A sample the incoming data such that the effective rate is the rate at which I want the samples to be selected by the D/A.
Suppose the D/A samples the data at 100 samples / second and my computer produces data at 200 samples / second. I can repeat my data twice and make it behave effectively at 100 samples/ second and then use it.
Do I make any sense ?
Thanks again,
Ali
On Tue, Sep 9, 2008 at 8:20 AM, Eric Blossom
<address@hidden> wrote:
On Tue, Sep 09, 2008 at 04:01:02AM -0500, Murtuza wrote:
> Hi friends,
>
> I have a gnuradio block that generates Gold code PN sequence. This code is
> based on Ed's code (mentioned earlier in a thread) which makes use of the
> gr.glfsr_source_b block and gr.xor_bb block. This gold code block generates
> PN seq at a rate that is depended upon the computer's performance ability.
> If I want to send a controlled sequence at 2Mcps how do I do this ? My work
> requires a chip sequence of 2Mcps but the one generated on my computer may
> be faster or slower. I did not find the exact rate though. Any ideas on how
> to do this ?
>
> Thanks
> Ali
Ali,
Virtually none of the blocks in GNU Radio (or any software radio for
that matter) know or care about the ultimate sample rate. The only
place that sample rate comes into play is when you actually meet a
sink or source that is attached to some kind of device that's
connected to the outside world (e.g., A/D, D/A, USRP).
If you have a rate limiting output device (D/A, USRP) and you know the
rate at which it consumes samples, then you can work backwards from
there. In any case, all kinds of questions come into play. How may
samples per chip are you using? 1?
Q: What is the sample rate of this stream of samples:
0, 1, 0, 1, 0, 1, 0, 0, 1, 1, 0, 1, ...
Eric
--
Mir Murtuza Ali
Graduate Student
Center for Wireless Communications
University of Mississippi
University, MS 38677