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| author | Andy Walls <awalls.cx18@gmail.com> | 2017-08-06 18:22:34 -0400 |
|---|---|---|
| committer | Andy Walls <awalls.cx18@gmail.com> | 2017-08-06 18:22:34 -0400 |
| commit | 688c1853def7210ec0baca9f09ec1b98d8e90474 (patch) | |
| tree | ed15cf80d461c20df4c3b619664f6a1083909642 /gr-digital/examples/demod | |
| parent | dfa01b39cf91df6387afb905285c57df9ba8e295 (diff) | |
digital: Add TED gain example Octave script & update symbol_sync_test_float.grc
Diffstat (limited to 'gr-digital/examples/demod')
3 files changed, 142 insertions, 6 deletions
diff --git a/gr-digital/examples/demod/symbol_sync_test_complex.grc b/gr-digital/examples/demod/symbol_sync_test_complex.grc index 11a044d382..77bacdeb12 100644 --- a/gr-digital/examples/demod/symbol_sync_test_complex.grc +++ b/gr-digital/examples/demod/symbol_sync_test_complex.grc @@ -594,11 +594,11 @@ </param> <param> <key>start</key> - <value>0.1</value> + <value>0.05</value> </param> <param> <key>step</key> - <value>0.1</value> + <value>0.01</value> </param> <param> <key>stop</key> diff --git a/gr-digital/examples/demod/symbol_sync_test_float.grc b/gr-digital/examples/demod/symbol_sync_test_float.grc index b0213d8b10..ce1b24ba4b 100644 --- a/gr-digital/examples/demod/symbol_sync_test_float.grc +++ b/gr-digital/examples/demod/symbol_sync_test_float.grc @@ -332,7 +332,7 @@ </param> <param> <key>value</key> - <value>0.07</value> + <value>0.125</value> </param> <param> <key>_enabled</key> @@ -558,7 +558,7 @@ </param> <param> <key>value</key> - <value>1.0</value> + <value>0.28365</value> </param> <param> <key>_enabled</key> @@ -594,11 +594,11 @@ </param> <param> <key>start</key> - <value>0.1</value> + <value>0.05</value> </param> <param> <key>step</key> - <value>0.1</value> + <value>0.01</value> </param> <param> <key>stop</key> diff --git a/gr-digital/examples/demod/symbol_sync_test_float_ted_gain.m b/gr-digital/examples/demod/symbol_sync_test_float_ted_gain.m new file mode 100644 index 0000000000..b4d47010b3 --- /dev/null +++ b/gr-digital/examples/demod/symbol_sync_test_float_ted_gain.m @@ -0,0 +1,136 @@ +% Copyright (C) 2017 Free Software Foundation +% +% This file is part of GNU Radio +% +% GNU Radio is free software; you can redistribute it and/or modify +% it under the terms of the GNU General Public License as published by +% the Free Software Foundation; either version 3, or (at your option) +% any later version. +% +% GNU Radio is distributed in the hope that it will be useful, +% but WITHOUT ANY WARRANTY; without even the implied warranty of +% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +% GNU General Public License for more details. +% +% You should have received a copy of the GNU General Public License +% along with GNU Radio; see the file COPYING. If not, write to +% the Free Software Foundation, Inc., 51 Franklin Street, +% Boston, MA 02110-1301, USA. + +% GNU Octave script to accompany the GNURadio flowgraph +% +% gnuradio/gr-digital/examples/demod/symbol_sync_test_float.grc +% +% to simulate the Mueller and Muller and Gardner timing error detectors +% and compute Expected TED gains applicable to the situation in that +% flowgraph. + +% Define some constants +N_bits = 30000; % Number of bits used for timing error analysis +Rb = 1200.0; +bits_per_sym = 1; +baud_rate = Rb/bits_per_sym; +N_syms = N_bits/bits_per_sym; % Number of symbols used for timing error analysis +tea_sps = 100; % samples/symbol used for timing error analysis +tea_Fs = tea_sps * baud_rate; % sample rate used for timing error analysis +a_sps = 6.66667; % actual samples per symbol used in application +a_Fs = a_sps * baud_rate; % actual sample rate used in application + +% Create rectangular pulse filter +pf_taps = 1/tea_sps * ones(tea_sps, 1); +pf_len = length(pf_taps); +pf_delay = pf_len/2; + +% Generate some bits +bits = rand(N_bits,1) > 0.5; +%bits = repmat([1;0], [N_bits/2, 1]); + +% Convert the bits to NRZ symbols in [-1, 1] +symbols = 2*bits-1; + +% Convert symbols to baseband pulses +pkg load signal; +x = tea_sps * upsample(symbols, tea_sps); +baseband = filter(pf_taps, [1], x); + +% Create rectangular matched filter, +% that's a little too long, to introduce more ISI +isi_sps = 6; % Play with isi samples to see S-curve effects +mf_taps = 1/(tea_sps+isi_sps) * ones((tea_sps+isi_sps), 1); +mf_len = length(mf_taps); +mf_delay = mf_len/2; + +% Matched filter the received baseband pulses +mf_baseband = filter(mf_taps, [1], baseband); +mf_baseband = mf_baseband * 1.0; % Play with amplitude to see S-curve effects + +% Symbol centers are now at indices n*tea_sps + isi_sps/2 (I think!) +% Symbol clock period is tea_sps samples +% Symbol peaks are perfectly at +/-1.0 + +% Timing offset granularity is in 1/tea_sps-th of a symbol +tau = [(-tea_sps/2):1:(tea_sps/2-1)]; +tau_norm = tau/tea_sps*a_sps; + +% M&M TED. Contellation points at -1.0 and +1.0. +% Gardener TED. +% Perfect estimate of symbol clock period. +% No external noise. +mm_ted_output = zeros(N_syms-2, length(tau)); +ga_ted_output = zeros(N_syms-2, length(tau)); +% For each known symbol peak set (M&M needs prev and current symbol) +for i = [2:(N_syms-1)] + % Cycle through all the timing offsets around this symbol + % using a perfect symbol clock period estimate + opt_prev_idx = (i-1)*tea_sps + isi_sps/2; + opt_curr_idx = i*tea_sps + isi_sps/2; + for j = [1:length(tau)] + prev_soft_sym = mf_baseband(opt_prev_idx - tau(j)); + mid_soft_samp = mf_baseband((opt_curr_idx+opt_prev_idx)/2 - tau(j)); + curr_soft_sym = mf_baseband(opt_curr_idx - tau(j)); + if (prev_soft_sym >= 0) + prev_decision = 1; + else + prev_decision = -1; + end + if (curr_soft_sym >= 0) + curr_decision = 1; + else + curr_decision = -1; + end + mm_ted_output(i,j) = prev_decision * curr_soft_sym - curr_decision * prev_soft_sym; + ga_ted_output(i,j) = (prev_soft_sym - curr_soft_sym) * mid_soft_samp; + end +end + +mean_mm_ted_output = mean(mm_ted_output); +mean_ga_ted_output = mean(ga_ted_output); + +% Plot the S-Curves +figure(1); +plot(tau_norm, mean_mm_ted_output, '- .b;M and M TED;', ... + tau_norm, mean_ga_ted_output, '- +r;Gardner TED;'); +title('S-Curve, 6.667 Samples/Symbol, Rectangular Pulses, Imperfect MF, E_s/N_0 = \infty'); +xlabel('Timing Error from Symbol Center, \tau_\epsilon (samples)'); +ylabel('Expected Value of TED Output, E(e[n] | \tau_\epsilon)'); +grid on; + +% Plot the TED gains +figure(2); +tau_diff = tau(1:(end-1))+0.5; +tau_diff_norm = tau_diff/tea_sps*a_sps; +diff_mm_ted_output = diff(mean_mm_ted_output)/(a_sps/tea_sps); +diff_ga_ted_output = diff(mean_ga_ted_output)/(a_sps/tea_sps); +plot(tau_diff_norm, diff_mm_ted_output, '- .b;M and M TED;', ... + tau_diff_norm, diff_ga_ted_output, '- +r;Gardner TED;'); +title('TED Gain, 6.667 Samples/Symbol, Rectangular Pulses, Imperfect MF, E_s/N_0 = \infty'); +xlabel('Timing Error from Symbol Center, \tau_\epsilon (samples)'); +ylabel('Timing Error Detector Gain, Slope of E(e[n] | \tau_\epsilon), (sample^{-1})'); +grid on; + +% Print out the central TED gains +k = length(diff_mm_ted_output); +mm_ted_gain = mean(diff_mm_ted_output(((k-1)/2):((k-1)/2+1))) +k = length(diff_ga_ted_output); +ga_ted_gain = mean(diff_ga_ted_output(((k-1)/2):((k-1)/2+1))) + |