[X] strip back experimental stuff to just features we need
[X] ZOH/integrator
[X] OFDM up and down conversion
- [ ] rate Fs HF model and HF results
- [ ] handle boarder carriers
+ [X] rate Fs HF model and HF results
+ [X] add QPSK
+ [X] add CP
+ [ ] adjust waveform parameters for real world
+ [ ] Nsec run time take into account CP
+ [ ] handle border carriers
[ ] start with phantom carriers
+ but unhappy with 1800Hz bandwidth
[ ] also try interpolation or just single row
Rs = 62.5;
Fs = 8000;
M = Fs/Rs;
- Tcp = 0.004; Ncp = Tcp*M;
+ Tcp = 0.002; Ncp = Tcp*Fs;
foffset = 0;
woffset = 2*pi*foffset/Fs;
% DDD
% PPP
- Nrows = sim_in.Nsec*Rs;
+ Nrows = sim_in.Nsec*Rs
Nframes = floor((Nrows-1)/Ns);
Nbits = Nframes * Nbitsperframe; % number of payload data bits
if isfield(sim_in, "path_delay_ms")
path_delay_ms = sim_in.path_delay_ms;
end
- printf("Doppler Spread: %3.2f Hz Path Delay: %3.2f ms\n", dopplerSpreadHz, path_delay_ms);
-
path_delay_samples = path_delay_ms*Fs/1000;
+ printf("Doppler Spread: %3.2f Hz Path Delay: %3.2f ms %d samples\n", dopplerSpreadHz, path_delay_ms, path_delay_samples);
randn('seed',1);
- spread1 = doppler_spread(dopplerSpreadHz, Fs, sim_in.Nsec*Fs*1.1);
- spread2 = doppler_spread(dopplerSpreadHz, Fs, sim_in.Nsec*Fs*1.1);
+ spread1 = doppler_spread(dopplerSpreadHz, Fs, (sim_in.Nsec*(M+Ncp)/M+0.2)*Fs);
+ spread2 = doppler_spread(dopplerSpreadHz, Fs, (sim_in.Nsec*(M+Ncp)/M+0.2)*Fs);
% sometimes doppler_spread() doesn't return exactly the number of samples we need
EbNo = bps * (10 .^ (EbNodB(nn)/10));
variance = 1/(M*EbNo/2);
-
% generate tx bits
tx_bits = rand(1,Nbits) > 0.5;
[nr nc] = size(tx_sym);
assert(nr == Nrp);
- % OFDM up conversion and upsampling to rate Fs
+ % OFDM up conversion and upsampling to rate Fs ---------------------
w = (0:Nc+1)*2*pi*Rs/Fs;
W = zeros(Nc+2,M);
W(c,:) = exp(j*w(c)*(0:M-1));
end
- Nsam = Nrp*M;
- tx = zeros(1,Nrp*M);
+ Nsam = Nrp*(M+Ncp);
+ tx = [];
+
+ % OFDM upconvert symbol by symbol so we can add CP
+
for r=1:Nrp
- for c=1:Nc+2
- acarrier = tx_sym(r,c) * W(c,:);
- tx((r-1)*M+1:r*M) += acarrier/M;
- end
+ asymbol = tx_sym(r,:) * W/M;
+ asymbol_cp = [asymbol(M-Ncp+1:M) asymbol];
+ tx = [tx asymbol_cp];
end
-
+ assert(length(tx) == Nsam);
+
+ % channel simulation ---------------------------------------------------------------
+
rx = tx;
if hf_en
- %rx = hf_gain * tx(1:Nsam) .* spread1(1:Nsam);
- %rx = hf_gain * [tx(path_delay_samples+1:Nsam) zeros(1,path_delay_samples)] .* spread2(1:Nsam);
- rx = hf_gain * [tx(path_delay_samples+1:Nsam) zeros(1,path_delay_samples)];
+ %rx = [zeros(1,path_delay_samples) tx(1:Nsam-path_delay_samples)];
+ rx = hf_gain * tx(1:Nsam) .* spread1(1:Nsam);
+ rx += hf_gain * [zeros(1,path_delay_samples) tx(1:Nsam-path_delay_samples)] .* spread2(1:Nsam);
end
rx = rx .* exp(j*woffset*(1:Nsam));
noise = sqrt(variance)*(0.5*randn(1,Nsam) + j*0.5*randn(1,Nsam));
rx += noise;
- % downconvert, downsample and integrate using OFDM
+ % downconvert, downsample and integrate using OFDM. Start integrating just after CP
+ % when ISI has died down
rx_sym = zeros(Nrp, Nc+2);
for r=1:Nrp
+ st = (r-1)*(M+Ncp)+Ncp+1; en = st + M - 1;
+ %printf("st: %d en: %d\n", st, en);
for c=1:Nc+2
- acarrier = rx((r-1)*M+1:r*M) .* conj(W(c,:));
+ acarrier = rx(st:en) .* conj(W(c,:));
rx_sym(r,c) = sum(acarrier);
end
end
end % r=1:Ns:Nrp-Ns
end % c=2:Nc+1
-
% remove pilots to give us just data symbols and demodulate
rx_bits = []; rx_np = [];
endfunction
-% Plot BER against Eb/No curves at various pilot insertion rates Ns
-% using the HF multipath channel. Second set of curves includes Eb/No
-% loss for pilot insertion, so small Ns means better tracking of phase
-% but large pilot insertion loss
+% Plot BER against Eb/No curves for AWGN and HF
-% Target operating point Eb/No is 6dB, as this is where our rate 1/2
+% Target operating point Eb/No for HF is 6dB, as this is where our rate 1/2
% LDPC code gives good results (10% PER, 1% BER). However this means
% the Eb/No at the input is 10*log(1/2) or 3dB less, so we need to
% make sure phase est works at Eb/No = 6 - 3 = 3dB
+%
+% For AWGN target is 2dB so -1dB op point.
+
+function run_curves
+ sim_in.bps = 2; sim_in.Nc = 8; sim_in.Ns = 7; sim_in.verbose = 0;
-function run_curves_hf
- sim_in.Nc = 8;
- sim_in.Ns = 8;
- sim_in.Nsec = 240;
- sim_in.EbNodB = 1:8;
- sim_in.verbose = 0;
sim_in.hf_en = 0;
+ sim_in.Nsec = 30;
+ sim_in.EbNodB = -3:5;
+ awgn_EbNodB = sim_in.EbNodB;
+
+ awgn_theory = 0.5*erfc(sqrt(10.^(sim_in.EbNodB/10)));
+ awgn = run_sim(sim_in);
+
+ sim_in.hf_en = 1;
+ sim_in.Nsec = 120;
+ sim_in.EbNodB = 1:8;
EbNoLin = 10.^(sim_in.EbNodB/10);
hf_theory = 0.5.*(1-sqrt(EbNoLin./(EbNoLin+1)));
- hf_sim = run_sim(sim_in);
+ hf = run_sim(sim_in);
figure(4); clf;
- semilogy(sim_in.EbNodB, hf_theory,'b+-;HF theory;');
+ semilogy(awgn_EbNodB, awgn_theory,'b+-;AWGN theory;');
hold on;
- semilogy(sim_in.EbNodB, hf.ber,'c+-;Ns=8 HFsim;');
+ semilogy(sim_in.EbNodB, hf_theory,'g+-;HF theory;');
+ semilogy(awgn_EbNodB, awgn.ber,'r+-;AWGN sim;');
+ semilogy(sim_in.EbNodB, hf.ber,'c+-;HF sim;');
hold off;
- axis([1 8 4E-2 2E-1])
+ axis([-3 8 1E-2 2E-1])
xlabel('Eb/No (dB)');
ylabel('BER');
grid; grid minor on;
function run_single
sim_in.bps = 2;
sim_in.Nc = 8;
- sim_in.Ns = 8;
- sim_in.Nsec = 10;
- sim_in.EbNodB = 4;
+ sim_in.Ns = 7;
+ % sim_in.Nsec = (sim_in.Ns+1)/62.5; % one frame
+ sim_in.Nsec = 120;
+ sim_in.EbNodB = 3;
sim_in.verbose = 1;
- sim_in.hf_en = 0;
+ sim_in.hf_en = 1;
+ sim_in.path_delay_ms = 1;
run_sim(sim_in);
end
format;
more off;
-
-run_single
-%run_curves_hf
+%run_single
+run_curves
projects / freetel-svn-tracking.git / commitdiff