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[Discuss-gnuradio] about ofdm

From: bin zan
Subject: [Discuss-gnuradio] about ofdm
Date: Mon, 24 Aug 2009 16:43:12 -0400

Hi all,
       I was trying to cut a packet into several pieces and send them through ofdm. I force the transmitter use only certain sub-carriers, for example first 64 sub-carriers. However, at the receiver side, I found it only can receive first piece of packet correct, and never receive the remaining piece correctly. Any help?


        The only places I modified are in gr_ofdm_mapper_bcv::work
 memset(out, 0, d_fft_length*sizeof(gr_complex));
  i = 0;
  unsigned char bits = 0;
  //while((d_msg_offset < d_msg->length()) && (i < d_occupied_carriers)) {     
  //while((d_msg_offset < d_msg->length()) && (i < d_subcarrier_map.size())) {
  while((d_msg_offset < d_msg->length()) && (i<64))  //so only use first 64 subcarriers
at transmitter side.
 And: in gr_ofdm_frame_sink::demapper
 if(d_byte_offset == 8) {
      //printf("demod byte: %x \n\n", d_partial_byte);                         
      if(bytes_produced<8)         //this will match the first 64 carriers for bpsk
           out[bytes_produced++] = d_partial_byte;                                                       
       d_byte_offset = 0;
       d_partial_byte = 0;
at the receiver side.

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