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-rw-r--r--configure.ac3
-rw-r--r--include/osmocom/dsp/Makefile.am2
-rw-r--r--include/osmocom/dsp/iqbal.h77
-rw-r--r--src/Makefile.am6
-rw-r--r--src/iqbal.c301
5 files changed, 385 insertions, 4 deletions
diff --git a/configure.ac b/configure.ac
index 6c7bf8d..ef2f014 100644
--- a/configure.ac
+++ b/configure.ac
@@ -18,6 +18,9 @@ AM_CONDITIONAL(HAVE_DOXYGEN, test $DOXYGEN != false)
AC_CONFIG_MACRO_DIR([m4])
+dnl checks for libraries
+PKG_CHECK_MODULES(FFTW3F, fftw3f >= 3.2.0)
+
dnl checks for header files
AC_CHECK_HEADERS([complex.h fcntl.h math.h stdio.h stdlib.h string.h unistd.h sys/mman.h sys/types.h sys/stat.h],,
AC_MSG_ERROR([Missing required header files.]))
diff --git a/include/osmocom/dsp/Makefile.am b/include/osmocom/dsp/Makefile.am
index 5a6534f..24c4c4a 100644
--- a/include/osmocom/dsp/Makefile.am
+++ b/include/osmocom/dsp/Makefile.am
@@ -1,3 +1,3 @@
-osmodsp_HEADERS = cfile.h cxvec.h cxvec_math.h
+osmodsp_HEADERS = cfile.h cxvec.h cxvec_math.h iqbal.h
osmodspdir = $(includedir)/osmocom/dsp
diff --git a/include/osmocom/dsp/iqbal.h b/include/osmocom/dsp/iqbal.h
new file mode 100644
index 0000000..c7f7e60
--- /dev/null
+++ b/include/osmocom/dsp/iqbal.h
@@ -0,0 +1,77 @@
+/*
+ * iqbal.h
+ *
+ * IQ balance correction / estimation utilities
+ *
+ * Copyright (C) 2013 Sylvain Munaut <tnt@246tNt.com>
+ *
+ * All Rights Reserved
+ *
+ * This program 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 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef __OSMO_DSP_IQBAL_H__
+#define __OSMO_DSP_IQBAL_H__
+
+/*! \defgroup iqbal IQ balance utilities
+ * @{
+ */
+
+/*! \file iqbal.h
+ * \brief Osmocom IQ balance utils header
+ */
+
+#include <complex.h>
+
+#include <osmocom/dsp/cxvec.h>
+
+
+/* IQ balance correction and estimation */
+
+void osmo_iqbal_fix(float complex *out, float complex *in, unsigned int len,
+ float mag, float phase);
+
+struct osmo_cxvec *
+osmo_iqbal_cxvec_fix(const struct osmo_cxvec *in, float mag, float phase,
+ struct osmo_cxvec *out);
+
+float
+osmo_iqbal_estimate(const float complex *data,
+ int fft_size, int fft_count);
+
+float
+osmo_iqbal_cxvec_estimate(const struct osmo_cxvec *sig,
+ int fft_size, int fft_count);
+
+
+/* IQ balance optimization */
+
+/*! \brief Processing options for the IQ balance optimization algorithm */
+struct osmo_iqbal_opts {
+ int fft_size; /*!< \brief FFT size to use */
+ int fft_count; /*!< \brief Number of FFT to use */
+ int max_iter; /*!< \brief Max # iterations per pass */
+ int start_at_prev; /*!< \brief Use prev values as starting point */
+};
+
+extern const struct osmo_iqbal_opts osmo_iqbal_default_opts;
+
+int
+osmo_iqbal_cxvec_optimize(const struct osmo_cxvec *sig, float *mag, float *phase,
+ const struct osmo_iqbal_opts *opts);
+
+/*! @} */
+
+#endif /* __OSMO_DSP_IQBAL_H__ */
diff --git a/src/Makefile.am b/src/Makefile.am
index b647898..ce37da5 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -3,9 +3,9 @@
LIBVERSION=0:0:0
INCLUDES = $(all_includes) -I$(top_srcdir)/include
-AM_CFLAGS = -Wall -ffast-math
+AM_CFLAGS = -Wall -ffast-math $(FFTW3F_CFLAGS)
lib_LTLIBRARIES = libosmodsp.la
-libosmodsp_la_SOURCES = cfile.c cxvec.c cxvec_math.c
-libosmodsp_la_LDFLAGS = -version-info $(LIBVERSION)
+libosmodsp_la_SOURCES = cfile.c cxvec.c cxvec_math.c iqbal.c
+libosmodsp_la_LDFLAGS = -version-info $(LIBVERSION) $(FFTW3F_LIBS)
diff --git a/src/iqbal.c b/src/iqbal.c
new file mode 100644
index 0000000..59c42eb
--- /dev/null
+++ b/src/iqbal.c
@@ -0,0 +1,301 @@
+/*
+ * iqbal.c
+ *
+ * IQ balance correction / estimation utilities
+ *
+ * Copyright (C) 2013 Sylvain Munaut <tnt@246tNt.com>
+ *
+ * All Rights Reserved
+ *
+ * This program 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 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+/*! \addtogroup iqbal
+ * @{
+ */
+
+/*! \file iqbal.c
+ * \brief IQ balance utils implementation
+ */
+
+#include <complex.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <fftw3.h>
+
+#include <osmocom/dsp/cxvec.h>
+#include <osmocom/dsp/cxvec_math.h>
+#include <osmocom/dsp/iqbal.h>
+
+
+/* ------------------------------------------------------------------------ */
+/* IQ balance correction and estimation */
+/* ------------------------------------------------------------------------ */
+
+/*! \brief Apply IQ balance correction to a given complex buffer
+ * \param[out] out Complex output buffer
+ * \param[in] in Complex input buffer
+ * \param[in] len Number of complex samples to process
+ * \param[in] mag Magnitude correction (approximated)
+ * \param[in] phase Phase correction (approximated)
+ *
+ * The input and output buffers can be the same for in-place modification.
+ *
+ * The exact applied is out[i] = (a * (1 + mag)) + (b + phase * a) * i
+ * (with in[i] = a+bi).
+ */
+void
+osmo_iqbal_fix(float complex *out, float complex *in, unsigned int len,
+ float mag, float phase)
+{
+ int i;
+
+ for (i=0; i<len; i++) {
+ float complex v = in[i];
+ out[i] = (crealf(v) * (1.0f + mag)) +
+ (cimagf(v) + phase * crealf(v)) * I;
+ }
+}
+
+/*! \brief Apply IQ balance correction to a given complex vector
+ * \param[in] in Complex input vector
+ * \param[in] mag Magnitude correction (approximated)
+ * \param[in] phase Phase correction (approximated)
+ * \param[out] out Complex output vector (can be NULL or equal to 'in')
+ * \returns The output complex vector (or NULL if error)
+ *
+ * If the 'out' parameter is NULL, a new vector will be allocated
+ * See \ref osmo_iqbal_fix for details of the correction applied.
+ */
+struct osmo_cxvec *
+osmo_iqbal_cxvec_fix(const struct osmo_cxvec *in, float mag, float phase,
+ struct osmo_cxvec *out)
+{
+ if (!out)
+ out = osmo_cxvec_alloc(in->len);
+
+ if (!out || out->max_len < in->len)
+ return NULL;
+
+ osmo_iqbal_fix(out->data, in->data, in->len, mag, phase);
+
+ out->len = in->len;
+ out->flags = in->flags;
+
+ return out;
+}
+
+/*! \brief Objectively estimate IQ balance in a given complex buffer
+ * \param[in] data Input complex buffer (at least fft_size * fft_count samples)
+ * \param[in] fft_size Size of the FFT to use internally
+ * \param[in] fft_count The number of consecutive FFT to use internally
+ * \returns A number >= 0.0f estimating the IQ balance (the lower, the better)
+ */
+float
+osmo_iqbal_estimate(const float complex *data, int fft_size, int fft_count)
+{
+ float complex *fft;
+ float est = 0.0f;
+ fftwf_plan fft_plan;
+ int i, j;
+
+ fft = malloc(sizeof(float complex) * fft_size);
+ fft_plan = fftwf_plan_dft_1d(fft_size, fft, fft, FFTW_FORWARD, FFTW_ESTIMATE);
+
+ for (i=0; i<fft_count; i++)
+ {
+ float complex corr = 0.0f;
+
+ memcpy(fft, &data[i*fft_size], sizeof(float complex) * fft_size);
+ fftwf_execute(fft_plan);
+
+ for (j=1; j<fft_size/2; j++)
+ corr += fft[fft_size-j] * conjf(fft[j]);
+
+ est += osmo_normsqf(corr); /* / (fft_size / 2); */
+ }
+
+ /* est /= fft_count; */
+
+ fftwf_destroy_plan(fft_plan);
+ free(fft);
+
+ return est;
+}
+
+/*! \brief Objectively estimate IQ balance in a given complex vector
+ * \param[in] sig Input complex vector (at least fft_size * fft_count samples)
+ * \param[in] fft_size Size of the FFT to use internally
+ * \param[in] fft_count The number of consecutive FFT to use internally
+ * \returns A number >= 0.0f estimating the IQ balance (the lower, the better)
+ */
+float
+osmo_iqbal_cxvec_estimate(const struct osmo_cxvec *sig,
+ int fft_size, int fft_count)
+{
+ if (sig->len < fft_size * fft_count)
+ return -1.0f;
+
+ return osmo_iqbal_estimate(sig->data, fft_size, fft_count);
+}
+
+
+/* ------------------------------------------------------------------------ */
+/* IQ balance optimization */
+/* ------------------------------------------------------------------------ */
+
+/*! \brief Default values for the optimization algorithm */
+const struct osmo_iqbal_opts osmo_iqbal_default_opts = {
+ .fft_size = 1024,
+ .fft_count = 8,
+ .max_iter = 25,
+ .start_at_prev = 1,
+};
+
+/*! \brief Internal state structure for the IQ balance optimization algorithm */
+struct _iqbal_state
+{
+ const struct osmo_iqbal_opts *opts; /*!< \brief Options */
+ const struct osmo_cxvec *org; /*!< \brief Original vector */
+ struct osmo_cxvec *tmp; /*!< \brief Temporary vector */
+ int feval; /*!< \brief # of function evaluation */
+};
+
+/*! \brief Optimization objective function - Value
+ * \param[in] state Current state object of optimization loop
+ * \param[in] x An array of 2 float for (mag,phase) point to evaluate at
+ * \returns The value of the objective function at point 'x'
+ */
+static inline float
+_iqbal_objfn_value(struct _iqbal_state *state, float x[2])
+{
+ state->feval++;
+ osmo_iqbal_cxvec_fix(state->org, x[0], x[1], state->tmp);
+ return osmo_iqbal_cxvec_estimate(state->tmp,
+ state->opts->fft_size, state->opts->fft_count);
+}
+
+/*! \brief Optimization objective function - Gradient estimation
+ * \param[in] state Current state object of optimization loop
+ * \param[in] x An array of 2 float for (mag,phase) point to evaluate at
+ * \param[in] v The value of the objective function at point 'x'
+ * \param[out] grad An array of 2 float for the estimated gradient at point 'x'
+ */
+static void
+_iqbal_objfn_gradient(struct _iqbal_state *state, float x[2], float v, float grad[2])
+{
+ #define GRAD_STEP 0.001f
+
+ float xd[2], vd[2];
+
+ xd[0] = x[0] + GRAD_STEP; xd[1] = x[1];
+ vd[0] = _iqbal_objfn_value(state, xd);
+
+ xd[0] = x[0]; xd[1] = x[1] + GRAD_STEP;
+ vd[1] = _iqbal_objfn_value(state, xd);
+
+ grad[0] = (vd[0] - v) / GRAD_STEP;
+ grad[1] = (vd[1] - v) / GRAD_STEP;
+}
+
+/*! \brief Optimization objective function - Value & Gradient estimation
+ * \param[in] state Current state object of optimization loop
+ * \param[in] x An array of 2 float for (mag,phase) point to evaluate at
+ * \param[out] grad An array of 2 float for the estimated gradient at point 'x'
+ * \returns The value of the objective function at point 'x'
+ */
+static inline float
+_iqbal_objfn_val_gradient(struct _iqbal_state *state, float x[2], float grad[2])
+{
+ float v = _iqbal_objfn_value(state, x);
+ _iqbal_objfn_gradient(state, x, v, grad);
+ return v;
+}
+
+
+/*! \brief Finds the best IQ balance correction parameters for a given signal
+ * \param[in] sig The input signal to optimize for
+ * \param[in,out] mag Magnitude correction (See \ref osmo_iqbal_fix)
+ * \param[in,out] phase Phase correction (See \ref osmo_iqbal_fix)
+ * \param[in] opts Options of the optimization process (See \ref osmo_iqbal_opts)
+ *
+ * The mag and phase parameters are pointers to float. If in the options,
+ * the 'start_at_prev' is enabled, the initial values of those will be used
+ * and so they should be initialized appropriately.
+ */
+int
+osmo_iqbal_cxvec_optimize(const struct osmo_cxvec *sig, float *mag, float *phase,
+ const struct osmo_iqbal_opts *opts)
+{
+ struct _iqbal_state _state, *state = &_state;
+ float cv, nv, step;
+ float cx[2], nx[2];
+ float cgrad[2];
+ float p;
+ int i;
+
+ if (!opts)
+ opts = &osmo_iqbal_default_opts;
+
+ if (sig->len < (opts->fft_size * opts->fft_count))
+ return -1;
+
+ state->org = sig;
+ state->tmp = osmo_cxvec_alloc(sig->len);
+ state->opts = opts;
+ state->feval = 0;
+
+ if (opts->start_at_prev) {
+ cx[0] = *mag;
+ cx[1] = *phase;
+ } else {
+ cx[0] = 0.0f;
+ cx[1] = 0.0f;
+ }
+
+ cv = _iqbal_objfn_val_gradient(state, cx, cgrad);
+ step = 0.1f * cv / (fabs(cgrad[0]) + fabs(cgrad[1]));
+
+ for (i=0; i<opts->max_iter; i++)
+ {
+ nx[0] = cx[0] - step * cgrad[0];
+ nx[1] = cx[1] - step * cgrad[1];
+
+ nv = _iqbal_objfn_value(state, nx);
+
+ if (nv < cv) {
+ p = (cv - nv) / cv;
+ if (p < 0.01f)
+ break;
+
+ cx[0] = nx[0];
+ cx[1] = nx[1];
+ cv = nv;
+ _iqbal_objfn_gradient(state, cx, cv, cgrad);
+ } else {
+ step /= 2.0f;
+ }
+ }
+
+ osmo_cxvec_free(state->tmp);
+
+ *mag = cx[0];
+ *phase = cx[1];
+
+ return 0;
+}
+
+/*! @} */