Hello Adeel/ML, this is fine, thanks.
Next doubt is the data format as input of the GMSK block.
Should it be as sequence of unsigned char[] bits ("01010101 00000000")
or unsigned char[] bytes ("\x55\x00")? Looking at the Mod code
(gmsk.py), the modulator first does a bytes_to_syms().
Second, in GRC 3.5.6.1 there are 2 GMSK modulator blocks, called:
- GMSK Mod (Samples/Symbols, BT)
- GMSK Modulator (Samples/Symbols, 3dB Time-Bandwith Product, Pulse
Duration)
What's their difference, and what are the meaning for the parameters on
the 2nd (GMKS Modulator)?
Thanks!
Il 21/07/2013 07:52, Adeel Anwar ha scritto:
>>1. Still I have to insert a "Packer Encoder" between my code and the
GMSK mod? If yes, with which parameters? The GMSK mod is configured with
Samples/Sym=50 , BT=0.4.
No. U can make custom packet structure and in that case u need not to
use Packet-Encoder.
>>2. Can someone explain me how to use the bitrate parameter? I mean,
should I "sync" the output of my block with the modulator? If yes, how?
Sync is not required because Signal-Processing blocks in GR don’t
understand bitrate/sampling-rate. If u have connected Transmitter-FG
with USRP, then u can determine the "effective bitrate" of transmitter
by calculating it backwards from USRP-sink sampling-rate.
symbol-rate = usrp-sampling-rate / samples-per-symbol
bit-rate = symbol-rate * modulated_bits_per_symbol
-Adeel
On Sun, Jul 21, 2013 at 1:44 AM, embyte <emb...@madlab.it
<mailto:emb...@madlab.it>> wrote:
Hello list, I would like to transmit some data using gnu-radio. My
data is a binary representation of an ASCII string.
I wrote my own block that builds the frame (header, payload, CRC,
trailer) as an array of 256 bytes (0s or 1s):
gr_make_io_signature(0, 0, 0)
gr_make_io_signature(1, 1, sizeof(char))
char *out = (char *) output_items[0];
[build the frame]
memcpy (out, frame, 256);
noutput_items = 256;
My question are:
1. Still I have to insert a "Packer Encoder" between my code and
the GMSK mod? If yes, with which parameters? The GMSK mod is
configured with Samples/Sym=50 , BT=0.4.
2. Can someone explain me how to use the bitrate parameter? I mean,
should I "sync" the output of my block with the modulator? If yes, how?
I tried to redirect the transmitted signal to a file, and use a
receiver (that I know working), but without success. The parameters
used in the receiver's GMSK demod are the same configured in the
modulator.
Thanks!
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