I am trying to change the OFDM_tx_rx payload modulation by a custom 64kQAM,
I implemented the block in several ways, it works fine but I had issues using it with OFDM_tx_rx:
/*********1- sync:************************************
taking a short item and produce a complex item
modulation:
**signatures:***
64kQAM_code_impl::64kQAM_code_impl( )
: gr::sync_block("64kQAM_code",
gr::io_signature::make(1, 1, sizeof(unsigned short int)),
gr::io_signature::make(1, 1, sizeof(gr_complex)))
{}
**work function:***
int
64kQAM_code_impl::work(int noutput_items,
gr_vector_const_void_star &input_items,
gr_vector_void_star &output_items)
{
const unsigned short int *in = (const unsigned short int *) input_items[0];
gr_complex *out = (gr_complex *) output_items[0];
for(int i = 0;i <noutput_items; i++) {
out[i].real((float(in[i]&0x00FF)-128.0)*level);
out[i].imag((float((in[i]&0xFF00)>>8)-128.0)*level);
}
return noutput_items;
}
demodulation:
taking a complex item and produce a short item
**signature:***
64kQAM_decode_impl::64kQAM_decode_impl( )
: gr::sync_block("64kQAM_decode",
gr::io_signature::make(1, 1, sizeof(gr_complex)),
gr::io_signature::make(1, 1, sizeof(unsigned short int)))
{}
**work function:***
int
64kQAM_decode_impl::work(int noutput_items,
gr_vector_const_void_star &input_items,
gr_vector_void_star &output_items)
{
const gr_complex *in = (const gr_complex *) input_items[0];
unsigned short int *out = (unsigned short int *) output_items[0];
unsigned short int tmp;
for(int i =0; i <noutput_items; i++)
{
tmp = int((in[i].imag()/level)+128.5);
tmp = (tmp<<8) | int((in[i].real()/level)+128.5);
out[i] = tmp;
}
return noutput_items;
}
Problem: -I got the write samples in the QT time sink, and in the
file sink, but the transmission stops after some amount
of data has been transmitted (repeat set to yes), the
packet_len tag is displayed
/*****2- interpolator/decimator:***********************
modulation:
takes 2 bytes and produce one complex item
demodulation:
takes one complex item and produce 2 bytes.
my decimaition and interpolation factor is 2
Problems: same as 1.
/******2-general:**************************************
modulation:
taking two byte items and produce a complex item
void
64kQAM_code_impl::forecast (int noutput_items, gr_vector_int &ninput_items_required)
{
ninput_items_required[0] = noutput_items*2;
}
int
64kQAM_code_impl::general_work (int noutput_items,
gr_vector_int &ninput_items,
gr_vector_const_void_star &input_items,
gr_vector_void_star &output_items)
{
const unsigned char *in = (const unsigned char*) input_items[0];
gr_complex *out = (gr_complex *) output_items[0];
for(int i = 0;i <noutput_items; i++)
{
out[i].real(in[2*i]*level);
out[i].imag(in[2*i+1]*level);
}
consume_each (noutput_items);
// Tell runtime system how many output items we produced.
return noutput_items;
}
demodulation:
void
64kQAM_decode::forecast (int noutput_items, gr_vector_int &ninput_items_required)
{
ninput_items_required[0] = noutput_items/2;
}
int
64kQAM_decode_impl::general_work (int noutput_items,
gr_vector_int &ninput_items,
gr_vector_const_void_star &input_items,
gr_vector_void_star &output_items)
{
const gr_complex *in = (const gr_complex *) input_items[0];
unsigned char *out = (unsigned char *) output_items[0];
for(int i =0; i <noutput_items; i++)
{
out[2*i]=in[i].real()/level;
out[2*i+1] =in[i].imag()/level;
}
consume_each (noutput_items);
// Tell runtime system how many output items we produced.
return noutput_items*2;
}
taking a complex item and produce two byte items
problem: -It writes quickly a large amount of data to the disk.
-In the QT display I get the correct samples but in a sink file
I got additionnal data generally this type (^@^@), also packet_len tag
is not displayed on the QT time GUI.
4-trying with tagged stream block, tagged stream mux block gives an error : " Buffer too small for min_noutput_items"