endfunction
-% Estimate fine timing instant using a window of samples rx. We
-% exploit similarity in waveform M-Ncp samples apart due to CP
-
-function ft_est = fine_timing(states, rx)
- Nsamperframe = states.Nsamperframe; M = states.M; Ncp = states.Ncp; Fs = states.Fs;
- verbose = states.verbose;
-
- Ncorr = length(rx) - (M+Ncp-1);
- printf("length %d Ncorr %d mx %d", length(rx), Ncorr, Ncorr+M+Ncp-1);
- printf("M: %d Ncp: %d\n", M, Ncp);
-
- assert(Ncorr > 0, "length(rx) too small");
- corr = zeros(1,Ncorr);
- for i=1:Ncorr
- corr(i) = abs(rx(i:i+Ncp-1) * rx(i+M:i+M+Ncp-1)')/(rx(i:i+Ncp-1) * rx(i:i+Ncp-1)');
- end
-
- [mx ft_est] = max(abs(corr));
-
- if verbose
- printf("ft_est: %d\n", ft_est);
- figure(6); clf;
- plot(abs(corr))
- end
-endfunction
-
-
function [sim_out rate_fs_pilot_samples rx] = run_sim(sim_in)
Fs = 8000;
Rs = sim_in.Rs;
EbNodB = sim_in.EbNodB;
verbose = sim_in.verbose;
hf_en = sim_in.hf_en;
+ timing_en = sim_in.timing_en;
Ns = sim_in.Ns; % step size for pilots
Nc = sim_in.Nc; % Number of cols, aka number of carriers
printf("Nrp....: %d (number of rows including pilots)\n", Nrp);
end
+ % generate same pilots each time
+
+ rand('seed',1);
+ pilots = 1 - 2*(rand(1,Nc+2) > 0.5);
+
% set up HF model ---------------------------------------------------------------
if hf_en
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);
+ % generate same fading pattern for every run
+
randn('seed',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);
% printf("nsymb: %d lspread1: %d\n", nsymb, length(spread1));
end
+ % init timing est states
+
+ tstates.Nsamperframe = Nsamperframe; tstates.M = M; tstates.Ncp = Ncp;
+ tstates.verbose = 0; tstates.Fs = Fs;
+ delta_t = [];
+ window_width = 11; % search window_width/2 from current timing instant
+
% simulate for each Eb/No point ------------------------------------
for nn=1:length(EbNodB)
% place symbols in multi-carrier frame with pilots and boundary carriers
- %pilots = ones(1,Nc+2);
- %pilots(1:2:Nc+2) = -1;
- pilots = 1 - 2*(rand(1,Nc+2) > 0.5);
tx_sym = []; s = 1;
for f=1:Nframes
aframe = zeros(Nrowsperframe,Nc+2);
end
assert(length(tx) == Nsam);
- % these are used for coarse timing and freq acquisition
+ % OFDM symbol of pilots is used for coarse timing and freq during acquisition, and fine timing
rate_fs_pilot_samples = tx(1:M+Ncp);
% channel simulation ---------------------------------------------------------------
rx = tx;
-
+
if hf_en
%rx = [zeros(1,path_delay_samples) tx(1:Nsam-path_delay_samples)];
rx = hf_gain * tx(1:Nsam) .* spread1(1:Nsam);
noise = sqrt(variance)*(0.5*randn(1,Nsam) + j*0.5*randn(1,Nsam));
rx += noise;
-
- % 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(st:en) .* conj(W(c,:));
- rx_sym(r,c) = sum(acarrier);
- end
- end
+ % some spare samples at end to allow for timing est window
+
+ rx = [rx zeros(1,M)];
% pilot based phase est, we use known tx symbols as pilots ----------
+ rx_sym = zeros(Nrp, Nc+2);
phase_est_pilot_log = 10*ones(Nrp,Nc+2);
phase_est_stripped_log = 10*ones(Nrp,Nc+2);
phase_est_log = 10*ones(Nrp,Nc+2);
- for c=2:Nc+1
- for r=1:Ns:Nrp-Ns
+ timing_est_log = [];
+ timing_est = Ncp/2;
+
+ for r=1:Ns:Nrp-Ns
+
+ if timing_en
+
+ % update timing every frame
+
+ if (mod(r-1,Ns) == 0) && (r != 1) && (r != Nrp)
+ %st = (r-1)*(M+Ncp) - ceil(window_width/2);
+ st = (r-1)*(M+Ncp) + 1 - floor(window_width/2) + (timing_est-1);
+ en = st + Nsamperframe-1 + length(rate_fs_pilot_samples) + window_width-1;
+ ft_est = coarse_sync(tstates, rx(st:en), rate_fs_pilot_samples);
+ timing_est += ft_est - ceil(window_width/2);
+ %if verbose
+ % printf("ft_est: %d timing_est %d\n", ft_est, timing_est);
+ %end
+ delta_t = [delta_t ft_est - ceil(window_width/2)];
+ end
+ end
+
+ timing_est_log = [timing_est_log timing_est];
+
+ % down convert at current timing instant
+
+ % previous pilot
+
+ if r > Ns+1
+ rr = r-Ns;
+ st = (rr-1)*(M+Ncp) + 1 + timing_est; en = st + M - 1;
+ for c=1:Nc+2
+ acarrier = rx(st:en) .* conj(W(c,:));
+ rx_sym(rr,c) = sum(acarrier);
+ end
+ end
+
+ % pilot - this frame - pilot
+
+ for rr=r:r+Ns
+
+ st = (rr-1)*(M+Ncp) + 1 + timing_est; en = st + M - 1;
+ for c=1:Nc+2
+ acarrier = rx(st:en) .* conj(W(c,:));
+ rx_sym(rr,c) = sum(acarrier);
+ end
+ end
+
+ % next pilot
+
+ if r < Nrp - 2*Ns
+ rr = r+2*Ns;
+ st = (rr-1)*(M+Ncp) + 1 + timing_est; en = st + M - 1;
+ for c=1:Nc+2
+ acarrier = rx(st:en) .* conj(W(c,:));
+ rx_sym(rr,c) = sum(acarrier);
+ end
+ end
+
+ % OK - now estimate and correct phase
+
+ for c=2:Nc+1
% estimate phase using average of 6 pilots in a rect 2D window centred
% on this carrier
rx_corr(rr,c) = rx_sym(rr,c) * exp(-j*aphase_est_pilot);
end
- end % r=1:Ns:Nrp-Ns
- end % c=2:Nc+1
+ end % c=2:Nc+1
+ end % r=1:Ns:Nrp-Ns
+
% remove pilots to give us just data symbols and demodulate
plot(phase_est_pilot_log(:,2:Nc+1),'g+', 'markersize', 5);
#{
+ % todo, work out a way to plot rate Fs hf model phase
if sim_in.hf_en
plot(angle(hf_model(:,2:Nc+1)));
end
#}
axis([1 Nrp -pi pi]);
+
+ figure(6); clf;
+ subplot(211)
+ stem(delta_t)
+ subplot(212)
+ plot(timing_est_log);
end
sim_out.ber(nn) = sum(Nerrs)/Nbits;
sim_in.Tcp = 0.002;
sim_in.Rs = 1/Ts; sim_in.bps = 2; sim_in.Nc = 16; sim_in.Ns = 8;
- sim_in.Nsec = 3*(sim_in.Ns+1)/sim_in.Rs; % one frame
- %sim_in.Nsec = 1;
+ %sim_in.Nsec = 3*(sim_in.Ns+1)/sim_in.Rs; % one frame
+ sim_in.Nsec = 30;
- sim_in.EbNodB = 20;
+ sim_in.EbNodB = 6;
sim_in.verbose = 1;
- sim_in.hf_en = 0;
+ sim_in.hf_en = 1;
sim_in.foff_hz = 0;
+ sim_in.timing_en = 0;
run_sim(sim_in);
end
% Run an acquisition test, returning vectors of estimation errors
-function [delta_ct delta_foff] = acquisition_test(Ntests=10, EbNodB=100, foff_hz=0, hf_en=0, fine_en)
+function [delta_t delta_foff] = acquisition_test(Ntests=10, EbNodB=100, foff_hz=0, hf_en=0, fine_en)
% generate test signal at a given Eb/No and frequency offset
- man I hope IL isn't too big.....
#}
- delta_ct = []; delta_foff = [];
+ delta_t = []; delta_t = []; delta_foff = [];
if fine_en
[ft_est foff_est] = coarse_sync(states, rx(st:en), rate_fs_pilot_samples);
printf("ft_est: %d timing_instant %d %d\n", ft_est, timing_instant, mod(timing_instant, Nsamperframe));
timing_instant += Nsamperframe + ft_est - ceil(window_width/2);
- delta_ct = [delta_ct ft_est - ceil(window_width/2)];
+ delta_t = [delta_ft ft_est - ceil(window_width/2)];
end
else
% for coarse simulation we just use contant window shifts
% valid coarse timing ests are modulo Nsamperframe
- delta_ct = [delta_ct ct_est-ct_target];
+ delta_t = [delta_ct ct_est-ct_target];
delta_foff = [delta_foff (foff_est-foff_hz)];
end
end
endfunction
-function fine_timing_test(Ntests=10, EbNodB=100, foff_hz=0, hf_en=0)
-
- % generate test signal at a given Eb/No and frequency offset
-
- Ts = 0.016;
- sim_in.Tcp = 0.002;
- sim_in.Rs = 1/Ts; sim_in.bps = 2; sim_in.Nc = 16; sim_in.Ns = 8;
-
- sim_in.Nsec = Ntests*(sim_in.Ns+1)/sim_in.Rs;
-
- sim_in.EbNodB = EbNodB;
- sim_in.verbose = 0;
- sim_in.hf_en = hf_en;
- sim_in.foff_hz = foff_hz;
-
- [sim_out rate_fs_pilot_samples rx] = run_sim(sim_in);
-
- % set up fine timing states
-
- Nsamperframe = states.Nsamperframe = sim_out.Nsamperframe;
- M = states.M = sim_out.M; Ncp = states.Ncp = sim_out.Ncp;
- states.verbose = 1;
- states.Fs = sim_out.Fs;
-
- figure(5); clf;
- subplot(211)
- plot(real(rx(1:1+Ncp-1)))
- hold on;
- plot(real(rx(M+1:M+1+Ncp-1)),'g')
- hold off;
- subplot(212)
- plot(imag(rx(1:1+Ncp-1)))
- hold on;
- plot(imag(rx(M+1:M+1+Ncp-1)),'g')
- hold off;
- rx(1:1+Ncp-1) * rx(1:1+Ncp-1)'
- rx(1:1+Ncp-1) * rx(M+1:M+1+Ncp-1)'
-
- st = 1;
- en = 2*(M+Ncp);
-
- figure(4); clf;
- subplot(211)
- plot(real(rx(st:en)))
- subplot(212)
- plot(imag(rx(st:en)))
-
- %%xx
- ft_est = fine_timing(states, rx(st:en));
-endfunction
-
% choose simulation to run here -------------------------------------------------------
format;
more off;
-%run_single
+run_single
%run_curves
-acquisition_histograms(1)
-%fine_timing_test
+%acquisition_histograms(1)
projects / freetel-svn-tracking.git / commitdiff