--- /dev/null
+% fdmdv_ut_freq_off.m
+% David Rowe 17 June 2014
+%
+% Unit Test program for freq offset estimation in FDMDV modem.
+%
+% Copyright David Rowe 2012 This program is
+% distributed under the terms of the GNU General Public License
+% Version 2
+
+% [ ] sweep of different delays
+% [ ] sweep of Eb/No
+% [ ] sweep of freq offsets
+% [ ] plot/print pass fail/relevant stats
+% + variance
+% + histogram of freq ests?
+
+fdmdv; % load modem code
+
+% Simulation Parameters --------------------------------------
+
+frames = 100;
+EbNovec = 10;
+Foff_hz = 0;
+
+% ---------------------------------------------------------------------
+% Eb/No calculations. We need to work out Eb/No for each FDM carrier.
+% Total power is sum of power in all FDM carriers
+% ---------------------------------------------------------------------
+
+function Nsd = calc_Nsd_from_EbNo(EbNo_dB)
+ global Rs;
+ global Nb;
+ global Fs;
+
+ C = 1; % power of each FDM carrier (energy/sample). Total Carrier power should = Nc*C = Nc
+ N = 1; % total noise power (energy/sample) of noise source across entire bandwidth
+
+ % Eb = Carrier power * symbol time / (bits/symbol)
+ % = C *(1/Rs) / Nb
+ Eb_dB = 10*log10(C) - 10*log10(Rs) - 10*log10(Nb);
+
+ No_dBHz = Eb_dB - EbNo_dB;
+
+ % Noise power = Noise spectral density * bandwidth
+ % Noise power = Noise spectral density * Fs/2 for real signals
+ N_dB = No_dBHz + 10*log10(Fs/2);
+ Ngain_dB = N_dB - 10*log10(N);
+ Nsd = 10^(Ngain_dB/20);
+end
+
+% ------------------------------------------------------------
+
+modulation = 'dqpsk';
+tx_filt = zeros(Nc,M);
+tx_fdm_log = [];
+rx_fdm_log = [];
+prev_tx_symbols = ones(Nc+1,1);
+ferr = 0;
+foff = 0;
+foff_log = [];
+
+% fixed delay simuation
+
+Ndelay = M+20;
+rx_fdm_delay = zeros(Ndelay,1);
+
+% ---------------------------------------------------------------------
+% Eb/No calculations. We need to work out Eb/No for each FDM carrier.
+% Total power is sum of power in all FDM carriers
+% ---------------------------------------------------------------------
+
+% freq offset simulation states
+
+phase_offset = 1;
+freq_offset = exp(j*2*pi*Foff_hz/Fs);
+foff_phase = 1;
+t = 0;
+foff = 0;
+
+% ---------------------------------------------------------------------
+% Main loop
+% ---------------------------------------------------------------------
+
+for ne = 1:length(EbNovec)
+ EbNo_dB = EbNovec(ne);
+ Nsd = calc_Nsd_from_EbNo(EbNo_dB);
+
+ for f=1:frames
+
+ % ------------------- Modulator -------------------
+
+ tx_bits = get_test_bits(Nc*Nb);
+ tx_symbols = bits_to_psk(prev_tx_symbols, tx_bits, modulation);
+ prev_tx_symbols = tx_symbols;
+ tx_baseband = tx_filter(tx_symbols);
+ tx_fdm = fdm_upconvert(tx_baseband);
+ tx_fdm_log = [tx_fdm_log real(tx_fdm)];
+
+ % ------------------- Channel simulation -------------------
+
+ % frequency offset
+
+ Foff = Foff_hz; for i=1:M freq_offset = exp(j*2*pi*Foff/Fs);
+ phase_offset *= freq_offset; tx_fdm(i) = phase_offset*tx_fdm(i); end
+
+ rx_fdm = real(tx_fdm);
+
+ % AWGN noise
+
+ noise = Nsd*randn(1,M);
+ rx_fdm += noise;
+ rx_fdm_log = [rx_fdm_log rx_fdm];
+
+ % Delay
+
+ rx_fdm_delay(1:Ndelay-M) = rx_fdm_delay(M+1:Ndelay);
+ rx_fdm_delay(Ndelay-M+1:Ndelay) = rx_fdm;
+ %rx_fdm_delay = rx_fdm;
+
+ % ------------------- Freq Offset Est -------------------
+
+ % frequency offset estimation and correction, need to call
+ % rx_est_freq_offset even in track mode to keep states updated
+
+ [pilot prev_pilot pilot_lut_index prev_pilot_lut_index] = ...
+ get_pilot(pilot_lut_index, prev_pilot_lut_index, M);
+ [foff_coarse S1 S2] = rx_est_freq_offset(rx_fdm_delay, pilot, prev_pilot, M);
+ foff_log(ne,f) = foff_coarse;
+ end
+end
+
+% ---------------------------------------------------------------------
+% Print Stats
+% ---------------------------------------------------------------------
+
+% ---------------------------------------------------------------------
+% Plots
+% ---------------------------------------------------------------------
+
+figure(1)
+clf
+for ne = 1:length(EbNovec)
+ foff_std(ne) = std(foff_log(ne,:));
+end
+plot(EbNovec,foff_std)
+xlabel("Eb/No (dB)")
+ylabel("Std Dev")
+
+figure(2)
+clf;
+plot(foff_log(1,:))
+xlabel("Frames")
+ylabel("Freq offset estimate")
+
+figure(3)
+clf;
+hist(foff_log(1,:))
% Design to test coherent demodulation ideas on HF channels without\r
% building a full blown modem. Uses 'genie provided' estimates for\r
% timing estimation, frame sync.\r
+%\r
\r
1;\r
\r
comb = conj(spread(sc:sc+M-1))' + conj(spread_2ms(sc:sc+M-1))';\r
if hf_phase_only\r
tx_filt = tx_filt.*exp(j*angle(comb));\r
- hf_angle_log = [hf_angle_log angle(comb)];\r
else\r
if hf_mag_only\r
comb = conj(spread(sc:sc+M-1))' + conj(spread_2ms(sc:sc+M-1))';\r
C_log = [C_log abs(comb)*hf_gain];\r
end\r
tx_filt_log = [tx_filt_log tx_filt];\r
+ hf_angle_log = [hf_angle_log angle(comb)];\r
\r
% AWGN noise and phase/freq offset channel simulation\r
% 0.5 factor ensures var(noise) == variance , i.e. splits power between Re & Im\r
figure(3);\r
clf;\r
\r
- if hf_phase_only\r
- plot(hf_angle_log);\r
- axis([1 10000 min(hf_angle_log) max(hf_angle_log)])\r
- else\r
- plot(C_log);\r
- end\r
+ subplot(211)\r
+ plot(C_log);\r
+ subplot(212)\r
+ plot(hf_angle_log);\r
+ axis([1 10000 min(hf_angle_log) max(hf_angle_log)])\r
end\r
endfunction\r
\r
projects / freetel-svn-tracking.git / commitdiff