Add PAPRStats module

1 files changed, 76 insertions, 0 deletions

diff --git a/src/PAPRStats.h b/src/PAPRStats.h
new file mode 100644
index 0000000..9463a3d
--- /dev/null
+++ b/src/PAPRStats.h
@@ -0,0 +1,76 @@
+/*
+   Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2011 Her Majesty
+   the Queen in Right of Canada (Communications Research Center Canada)
+
+   Copyright (C) 2017
+   Matthias P. Braendli, matthias.braendli@mpb.li
+
+    http://opendigitalradio.org
+ */
+/*
+   This file is part of ODR-DabMod.
+
+   ODR-DabMod 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 of the
+   License, or (at your option) any later version.
+
+   ODR-DabMod 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 ODR-DabMod.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#ifdef HAVE_CONFIG_H
+#   include "config.h"
+#endif
+
+#include <cstddef>
+#include <vector>
+#include <deque>
+#include <complex>
+
+typedef std::complex<float> complexf;
+
+/* Helper class to calculate Peak-to-average-power ratio.
+ * Definition of PAPR:
+ *
+ * PAPR_dB = 10 * log_10 ( abs(x_peak)^2 / x_rms^2 )
+ *
+ * with abs(x_peak) the peak amplitude of the signal, and
+ * x_rms the Root Mean Squared.
+ *
+ * x_rms^2 = 1/n * Sum abs(x_n)^2
+ *         = 1/n * Sum norm(x_n)
+ *
+ * Given that peaks are rare in a DAB signal, we want to accumulate
+ * several seconds worth of samples to do our calculation.
+ */
+class PAPRStats
+{
+    public:
+        PAPRStats(size_t num_blocks_to_accumulate);
+
+        /* Push in a new block of samples to measure. calculate_papr()
+         * assumes all blocks have the same size.
+         */
+        void process_block(const complexf* data, size_t data_len);
+
+        /* Returns PAPR in dB if enough blocks were processed, or
+         * 0 otherwise.
+         */
+        double calculate_papr(void);
+
+    private:
+        size_t m_num_blocks_to_accumulate;
+        std::deque<double> m_squared_peaks;
+        std::deque<double> m_squared_mean;
+};
+
+
+