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42cf28baf6d435d361421d123f618d45084e3b43
matlab/ofdm/ofdm_rx.m
T
jens 42cf28baf6 [calcWiener] 
- calc W_pilots
[RX]
- added delta_freq for tracking (Zwischenstand)


git-svn-id: http://moon:8086/svn/matlab/trunk@52 801c6759-fa7c-4059-a304-17956f83a07c
2015-05-02 08:55:06 +00:00

312 lines
8.1 KiB
Matlab
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function [sym_out, H, W] = ofdm_rx(filename, foff, SNR, with_cir, show_H)
%
% [sym_out, H, W] = ofdm_rx(filename, foff, SNR, with_cir, show_H)
% Example: ofdm_rx('drm-15435-if.wav', -174.65, 400, 0, 1)
% Example: ofdm_rx('xv.wav', 0, 400, 0, 1)
% or ofdm_rx('yv.wav', 0, 400, 0, 1)
close all;
drm_mode = 'B';
drm_bw = '10k';
[ofdm_drm_params, ofdm_spec_occ] = drm_params(drm_mode, drm_bw);
pre_mix = 0;
fs = 12000;
N = 256;
Ng = 64;
[carrier_pilot, phi_pilot, mag_pilot] = getRefFreq(drm_mode);
[carrier_time, phi_time, mag_time] = getRefTime(drm_mode);
h_cir = [0 0 .1 -.2 .5 .2 -.1 0 0 ];
% Generate signal
[xwav fs_ nbits] = wavread(filename);
[len ndim] = size(xwav);
if (ndim == 2)
fprintf('Mode: Baseband\n');
x = xwav(:, 1) + j*xwav(:, 2);
x = x.*exp(-j*(2*pi*(foff/fs_)*(0:len-1)'));
elseif (ndim == 1)
fprintf('Mode: Passband\n');
x = xwav.*exp(-j*(2*pi*(0.25-foff/fs_)*(0:len-1)'));
hlp = FIRCalcLowpass(12000/fs_, 15);
x = filter(hlp, 1, x);
% Downsample
x = x(1:4:length(x));
else
error('Cannot read file!');
end
if with_cir
x = filter(h_cir, 1, x);
end
x = x - mean(x);
x = x./max(abs(x));
xout = [real(x) imag(x)];
wavwrite(xout,fs,nbits,'ofdm_rx.wav');
x = awgn(x, SNR, 'measured');
K = fix((length(x))/(N+Ng))-1;
% Timing coarse
cp_off = 0;
cp_off_ = [];
if 1
fprintf('Coarse timing estimation\n');
Z = 0;
for k=1:20
xp = x((k-1)*(N+Ng)+1:k*(N+Ng));
[cp_off, Nd, valid, Z] = timing_coarse(xp, N, Ng, Ng, Z);
if (valid)
cp_off_ = [cp_off_ cp_off];
end
end;
cp_off = round(median(cp_off_))
Nd = Nd
end
fdet_coarse_Z = 0;
Z_cfa_pre = 0;
df_i_ = [];
valid_latency_count = 20;
if 1
fprintf('Coarse integer CFO estimation\n');
% Integer CFO coarse
for k=1:200
xp = x((k-1)*(N+Ng)+cp_off+1:k*(N+Ng)+cp_off);
[d_bin, valid, fdet_coarse_Z] = cfo_coarse_int(xp(Ng+1:N+Ng), N, carrier_pilot, 11, fdet_coarse_Z);
if valid
df_i = -d_bin(1)/N*fs;
if valid_latency_count > 0
valid_latency_count = valid_latency_count - 1;
else
break;
end
end
end;
end
fprintf('Coarse fractional CFO estimation\n');
% CFO coarse
df_f_ = [];
for k=1:200
xp = x((k-1)*(N+Ng)+cp_off+1:k*(N+Ng)+cp_off);
[domega_f, Z_cfa_pre] = cfo_coarse_fract(xp, N, Ng, Ng, Nd, Z_cfa_pre);
df_f_ = [df_f_ domega_f*fs];
end;
df_coarse = df_i + mean(df_f_(10:200))
df_coarse_ = df_i + df_f_;
if pre_mix
x1 = x.*exp(j*(2*pi*df_coarse/fs.*(0:length(x)-1)'));
df_track = 0;
else
x1 = x;
df_track = df_coarse;
end
% CFO Fine
fprintf('Fine CFO estimation\n');
fprintf('Receive Symbols\n');
Xlast = [];
df_fine = 0;
df_fine_ = [];
df_track_ = [];
kn = fs/(2*pi*(1+Ng/N))/N;
x_ = [];
Hp_ = [];
Z_ = [];
phi = 0.0;
bin_track = 1;
sym_pilot = exp(j*2*pi*phi_pilot'/1024);
bin_pilot = c2i(N, carrier_pilot);
for k=1:K,
xp = x1((k-1)*(N+Ng)+cp_off+1:k*(N+Ng)+cp_off);
xp = xp.*exp(j*(2*pi*df_track/fs*(0:N+Ng-1)' + phi));
phi = phi + 2*pi*df_track/fs*(N+Ng);
xp = xp(Ng+1:N+Ng);
x_ = [x_' xp']';
X = fft(xp);
if (~isempty(Xlast))
Z = Xlast .* conj(X);
df_fine = kn*angle(Z(bin_pilot));
df_fine_ = [df_fine_ df_fine];
phi_p = angle(X(bin_pilot));
mag_p = abs(X(bin_pilot));
df_track = df_track + 0.1*mean(df_fine(bin_track));
df_track_ = [df_track_ df_track];
Hp = X(bin_pilot)./conj(sym_pilot);
Hp_ = [Hp_ Hp];
Z_ = [Z_ X];
end
Xlast = X;
end
if ~isempty(cp_off_)
figure;
plot(0:length(cp_off_)-1, cp_off_, 0:length(cp_off_)-1, cp_off*ones(size(cp_off_)), 'r-'); grid; title('cp_{off}')
end
df_track_ = df_track_';
figure;
subplot(3, 1, 1)
plot(0:length(df_coarse_)-1, df_coarse_); grid; title('df_{coarse}')
subplot(3, 1, 2)
plot(0:length(df_track_)-1, df_track_); grid; title('df_{track}')
subplot(3, 1, 3)
plot(0:length(df_fine_)-1, df_fine_); grid; title('df_{fine}')
figure;
Z_pilot = Z_(bin_pilot, 200:length(Z_))';
plot(real(Z_pilot), imag(Z_pilot), '+'); grid; title('SymPilot_{Freq}');
maxZ = max(max(abs(Z_pilot)));
if (maxZ < 1)
axis([-1 1 -1 1]);
else
axis([-maxZ maxZ -maxZ maxZ]);
end
%% Detect start of DRM frame
bins = c2i(N, carrier_time);
kc_max = -1000;
n_max = 0;
skip_syms = 15*4;
for n=0:15-1
frame_timing_Z = 0;
k = skip_syms+n;
for m=1:2
[kc valid frame_timing_Z] = timing_frame(Z_(bins, k)', bins, 15, frame_timing_Z);
k = k + 15;
end
if valid
if kc > kc_max
n_max = n;
kc_max = kc;
end
end
end
frame_start = n_max
figure;
start = skip_syms+frame_start;
Z_timing = Z_(bins, start:15:length(Z_))';
plot(real(Z_timing), imag(Z_timing), '+'); grid; title('SymPilot_{Time}');
maxZ = max(max(abs(Z_timing)));
if (maxZ < 1)
axis([-1 1 -1 1]);
else
axis([-maxZ maxZ -maxZ maxZ]);
end
[W_syms, W_pilots] = calcWiener(drm_mode, drm_bw);
figure;
% Detect scattered gain pilots
symbols_per_frame = ofdm_drm_params.nspf;
symbols_to_delay = ofdm_drm_params.y;
frames_per_window = 2*ofdm_drm_params.y;
H_gain_cell = cell (frames_per_window, 1);
H_gain_carriers_cell = cell (frames_per_window, 1);
H_raw = zeros(length(ofdm_spec_occ.kmin:ofdm_spec_occ.kmax),1);
carriers = ofdm_spec_occ.kmin:ofdm_spec_occ.kmax;
carrier_indexes = c2i(N, carriers);
fac_cell_list = ...
{
[],
[],
[13, 25, 43, 55, 67],
[15, 27, 45, 57, 69],
[17, 29, 47, 59, 71],
[19, 31, 49, 61, 73],
[9, 21, 33, 51, 63, 75],
[11, 23, 35, 53, 65, 77],
[13, 25, 37, 55, 67, 79],
[15, 27, 39, 57, 69, 81],
[17, 29, 41, 59, 71, 83],
[19, 31, 43, 61, 73],
[21, 33, 45, 63, 75],
[23, 35, 47, 65, 77],
[]
};
symbol_counter = 0;
win_count = 0;
H_syms = [];
H_pilots = [];
sym_out = [];
kk = 1;
H_ = [];
for k=start:length(Z_)
%shifted symbol index
nn = rem(k-start-1-symbols_to_delay + symbols_per_frame, symbols_per_frame);
m = floor(nn/ofdm_drm_params.y);
n = rem(nn, ofdm_drm_params.y);
[carrier_gain, phi_gain, mag_gain] = getRefGain(ofdm_drm_params, ofdm_spec_occ, symbol_counter);
carrier_gain_bins = c2i(N, carrier_gain);
if ~isempty(H_pilots)
delta_freq_offset = fs/(2*pi*N)*angle( H_pilots * conj(H2_))
end
H2_ = H_;
H_= Z_(carrier_gain_bins, k)./(mag_gain.*exp(j*2*pi*phi_gain/1024)).';
H_raw(carrier_gain_bins) = H_;
H_gain_cell{win_count+1} = transpose(H_);
ii = 1+mod(n+(0:frames_per_window-1), frames_per_window);
H_gain = [H_gain_cell{ii}];
H_gain_carriers_cell{win_count+1} = carrier_gain;
str = sprintf('Frame %d, SymCount %d, winCount %d, n=%d', k, symbol_counter, win_count, n);
if length(H_gain) == 208
H_syms = H_gain*W_syms{n+1};
H_pilots = H_gain*W_pilots{n+1};
ZZ = Z_(carrier_indexes, k-symbols_to_delay).';
sym_eq = ZZ ./ H_syms;
sym_out(:, kk) = sym_eq;
if show_H
H_raw(1:2:N) = H_raw(2:2:N);
subplot(3, 1, 1)
plot(carriers, abs(H_raw(carrier_indexes)), 'b-', carriers, abs(H_syms), 'r-'); grid; title('abs(H_{syms})'); axis([ofdm_spec_occ.kmin ofdm_spec_occ.kmax 0 15+0*max(abs(H_syms))]); title(str);
subplot(3, 1, 2)
plot(carriers, angle(H_raw(carrier_indexes)), 'b-', carriers, angle(H_syms), 'r-'); grid; title('phi(H_{syms})'); axis([ofdm_spec_occ.kmin ofdm_spec_occ.kmax -4 4]); title(str);
subplot(3, 1, 3)
plot(carriers, abs(sym_eq), 'b-'); grid; title('abs(Sym_{Eq})'); axis([ofdm_spec_occ.kmin ofdm_spec_occ.kmax 0 2]); title(str);
hold on;
for b=c2i(N, carrier_pilot)
x = [b b];
y = [0 2];
plot(x-1,y, 'r-');
end
hold off;
pause(0.01);
else
fac_c = fac_cell_list{mod(symbol_counter-symbols_to_delay, symbols_per_frame)+1};
if (~isempty(fac_c))
fac_i = fac_c - ofdm_spec_occ.kmin + 1;
hold on;
plot(sym_eq(fac_i), '+', 'MarkerSize', 4);
pause(0.01);
grid; title('FAC'); axis([-1 1 -1 1]);
hold off;
end
end
end
kk = kk + 1;
win_count = mod(win_count+1, frames_per_window);
symbol_counter = mod(symbol_counter + 1, symbols_per_frame);
end
function Y = spec_order(N, X)
Y = [X(N/2+1:N)' X(1:N/2)']';
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