Doubt in digital modulation chain

GNU Radio
1

Dear All,

I am constructing the flow graph(screen capture, grc) attached.

I am expecting the data at the output of packed-to-unpacked block to be
the
same as the data at the output of differential decoder, except for some
stray bits in the beginning. When I search for patterns in the transmit
chain, in the receive chain, I don’t get any match. This it the
code(also
attached) that I use to compare data in the transmit chain and the
receive
chain.

import scipy

template_len = 20

temp = scipy.fromfile(open("/tmp/diff-encode-out.bin"),
dtype=scipy.uint8, count=1000)
template = temp[100:template_len+100]
print len(template)
match = False
rec = scipy.fromfile(open("/tmp/rec-map-out.bin"), dtype=scipy.uint8,
count=100000)
for i in range(9950):
if (template == rec[i:template_len+i]).all():
print i
break

The program works for BPSK, but fails to find pattern in QPSK, DQPSK
etc.
Would anyone know what is going wrong in my flow-graph?

Thank you in advance.

2

On Mon, Jul 7, 2014 at 4:08 PM, Manu T S [email protected] wrote:

======================
count=100000)

Manu T S

Hi Manu,

This generally looks correct, but you’ll want to see about that map
block
(or the constellation pre-diff coding) to translate the symbols->bits
correctly. And if you think you’ve done it right, try again :slight_smile:

Tom