Re: [Discuss-gnuradio] Using GMSK Mod to send digital data (e.g. an ASCII string)

[Adeel Anwar]

>>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 <address@hidden> 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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