96 lines
2.7 KiB
Matlab
96 lines
2.7 KiB
Matlab
% ofdm_tx.m
|
|
% David Rowe March 2018
|
|
%
|
|
% File based, uncoded OFDM tx. Generates a file of ofdm samples,
|
|
% including optional channel simulation. See also ofdm_ldpc_tx.m, and
|
|
% ofdm_mod.c
|
|
|
|
#{
|
|
Examples:
|
|
|
|
i) 10 seconds, AWGN channel at SNR3k=3dB
|
|
|
|
octave:4> ofdm_tx("awgn_snr_3dB_700d.raw", "700D", 10, 3)
|
|
|
|
ii) 10 seconds, multipath poor channel at SNR=6dB
|
|
|
|
octave:5> ofdm_tx("hf_snr_6dB_700d.raw", "700D", 10, 6, "mpp")
|
|
|
|
iii) Data mode example, three bursts of one packet each, SNR=100dB:
|
|
|
|
octave:6> ofdm_tx("test_datac0.raw","datac0",1,100,"awgn","bursts",3)
|
|
|
|
#}
|
|
|
|
function ofdm_tx(filename, mode="700D", N, SNR3kdB=100, channel='awgn', varargin)
|
|
ofdm_lib;
|
|
channel_lib;
|
|
randn('seed',1);
|
|
pkg load signal;
|
|
|
|
tx_clip_en = 0; freq_offset_Hz = 0.0; burst_mode = 0; Nbursts = 1;
|
|
i = 1;
|
|
while i<=length(varargin)
|
|
if strcmp(varargin{i},"txclip")
|
|
tx_clip_en = 1;
|
|
elseif strcmp(varargin{i},"bursts")
|
|
burst_mode = 1;
|
|
Nbursts = varargin{i+1}; i++;
|
|
else
|
|
printf("\nERROR unknown argument: [%d] %s \n", i ,varargin{i});
|
|
return;
|
|
end
|
|
i++;
|
|
end
|
|
|
|
% init modem
|
|
|
|
config = ofdm_init_mode(mode);
|
|
states = ofdm_init(config);
|
|
print_config(states);
|
|
ofdm_load_const;
|
|
|
|
if burst_mode
|
|
% burst mode: treat N as Npackets
|
|
Npackets = N;
|
|
else
|
|
% streaming mode: treat N as Nseconds
|
|
Npackets = round(N/states.Tpacket);
|
|
end
|
|
|
|
% Generate fixed test frame of tx bits and concatenate packets
|
|
|
|
tx_bits = create_ldpc_test_frame(states, coded_frame=0);
|
|
atx = ofdm_mod(states, tx_bits);
|
|
tx = [];
|
|
for f=1:Npackets
|
|
tx = [tx atx];
|
|
end
|
|
if length(states.data_mode)
|
|
% note postamble provides a "column" of pilots at the end of the burst
|
|
tx = [states.tx_preamble tx states.tx_postamble];
|
|
end
|
|
|
|
% if burst mode concatenate multiple bursts with spaces
|
|
if burst_mode
|
|
atx = tx; tx = zeros(1,states.Fs); on_time = 0; off_time = states.Fs;
|
|
for b=1:Nbursts
|
|
tx = [tx atx zeros(1,states.Fs)];
|
|
on_time += length(atx);
|
|
off_time += states.Fs;
|
|
end
|
|
% adjust channel simulator SNR setpoint given (burst on length)/(total length including silence) ratio
|
|
mark_space_SNR_offset = 10*log10(on_time/(on_time+off_time));
|
|
SNRdB_setpoint = SNR3kdB + mark_space_SNR_offset;
|
|
printf("SNR3kdB: %4.2f Burst offset: %4.2f SNRdB_setpoint: %4.2f\n", SNR3kdB, mark_space_SNR_offset, SNRdB_setpoint)
|
|
else
|
|
SNRdB_setpoint = SNR3kdB; % no adjustment to SNR in streaming mode
|
|
end
|
|
|
|
printf("Npackets: %d Nbursts: %d ", Npackets, Nbursts);
|
|
states.verbose=1;
|
|
tx = ofdm_hilbert_clipper(states, tx, tx_clip_en);
|
|
rx_real = ofdm_channel(states, tx, SNRdB_setpoint, channel, freq_offset_Hz);
|
|
frx = fopen(filename,"wb"); fwrite(frx, rx_real, "short"); fclose(frx);
|
|
endfunction
|