problem1 : No ofdm signal at OFDM reciver. simply noise like signal.

configuration in the OFDM transmitter block should be correct . carrier indices, pilot indices , SYNC words. should be correctly set.

problem2 : ofdm signal at the reciver has deformed signal. you can see saturated or clipped off signal portions

solution : add a multiply by constant block before transmitting SDR sink.

adjust the transmitter attenuation and reciver gain so that recieved signal has enough SNR.

problem3 : signal at OFDM reciever keeps coming but ON and OFF

cause : this may be because short packet length (eg: 1 byte of data) and hence huge tag processing overwhelms blocks in flow graph . so sdr sink block may not be getting enough time to tranmit the signal continously.

solution: let the packet length be a higher value .

problem4 : packet parser detects invalid packets

debug logs you can see on command line are as follows :

packet_headerparser_b :info: Detected an invalid packet at item 0 header_payload_demux :info: Parser returned #f packet_headerparser_b :info: Detected an invalid packet at item 48 header_payload_demux :info: Parser returned #f packet_headerparser_b :info: Detected an invalid packet at item 96 header_payload_demux :info: Parser returned #f packet_headerparser_b :info: Detected an invalid packet at item 144 header_payload_demux :info: Parser returned #f packet_headerparser_b :info: Detected an invalid packet at item 1296 header_payload_demux :info: Parser returned #f packet_headerparser_b :info: Detected an invalid packet at item 1872 header_payload_demux :info: Parser returned #f packet_headerparser_b :info: Detected an invalid packet at item 3024 header_payload_demux :info: Parser returned #f packet_headerparser_b :info: Detected an invalid packet at item 4320 header_payload_demux :info: Parser returned #f packet_headerparser_b :info: Detected an invalid packet at item 4800

causes : there can be timing synchronization error (or) frequency deviation error .

debugging : found that using a window in fft block is causing this problem .out_hdr signal from header payload demux is fed back into it’s input header_data input after passing through header parser. the header parser is failing to verify header CRC. and outputs the message #f . and prints error log info like : “Detected an invalid packet at item 96(offset)”

problem5: Payload in an OFDM frame = (96bytes+CRC32) = (96×8)+(4×8)=(768+32)=800 bits
with BPSK as modulation scheme for header&Payload as well , It fits in 800/48 = 16.66 => 17 symbols.
17×48 = 816 ===> 800 data symbols + 16 extra symbols

payload serializer produces packet length tag key value pair : <"payload_len" ,816>