On 2/18/15, 6:45 PM, Richard Bell wrote:
Hello all,
I am testing a QPSK Tx/Rx I made in grc across two USRP N210's. I can
demodulate and decode the data fine at the receiver to produce the bits
I transmitted. The problem is, when watching the frequency sink at the
output of the USRP source (picture attached), there is typically 4
seconds of latency between making a change at the transmitter and seeing
the change at the frequency sink block. I'm worried this is a bad sign
of things to come.
Richard,
The lag is not due to processing power, but instead due to buffering
latency. Every flow between blocks has a default buffer size of 64k
bytes. This means that the LOWER sample rates will take longer to
traverse the buffer.
The latest versions of GRC include a block parameter to restrict the
buffer size. This should be set to a much lower value than the default
for the portions of the flowgraph that are dealing with packed or
unpacked data bits, as these are at a MUCH lower rate than the I/Q
samples going into the demodulator.
@(^.^)@ Ed
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