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-rw-r--r--src/OfdmGenerator.cpp134
-rw-r--r--src/OfdmGenerator.h79
2 files changed, 178 insertions, 35 deletions
diff --git a/src/OfdmGenerator.cpp b/src/OfdmGenerator.cpp
index 20ba2b7..3d3dfd7 100644
--- a/src/OfdmGenerator.cpp
+++ b/src/OfdmGenerator.cpp
@@ -2,7 +2,7 @@
Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2011 Her Majesty
the Queen in Right of Canada (Communications Research Center Canada)
- Copyright (C) 2016
+ Copyright (C) 2017
Matthias P. Braendli, matthias.braendli@mpb.li
http://opendigitalradio.org
@@ -34,19 +34,23 @@
#include <stdexcept>
#include <assert.h>
#include <complex>
-typedef std::complex<float> complexf;
+#include <string>
OfdmGenerator::OfdmGenerator(size_t nbSymbols,
size_t nbCarriers,
size_t spacing,
bool inverse) :
- ModCodec(),
- myFftPlan(NULL),
- myFftIn(NULL), myFftOut(NULL),
+ ModCodec(), RemoteControllable("ofdm"),
+ myFftPlan(nullptr),
+ myFftIn(nullptr), myFftOut(nullptr),
myNbSymbols(nbSymbols),
myNbCarriers(nbCarriers),
- mySpacing(spacing)
+ mySpacing(spacing),
+ myCfr(false),
+ myCfrClip(1.0f),
+ myCfrErrorClip(1.0f),
+ myCfrFft(nullptr)
{
PDEBUG("OfdmGenerator::OfdmGenerator(%zu, %zu, %zu, %s) @ %p\n",
nbSymbols, nbCarriers, spacing, inverse ? "true" : "false", this);
@@ -56,6 +60,11 @@ OfdmGenerator::OfdmGenerator(size_t nbSymbols,
"OfdmGenerator::OfdmGenerator nbCarriers > spacing!");
}
+ /* register the parameters that can be remote controlled */
+ RC_ADD_PARAMETER(cfr, "Enable crest factor reduction");
+ RC_ADD_PARAMETER(cfrclip, "CFR: Clip to amplitude");
+ RC_ADD_PARAMETER(cfrerrorclip, "CFR: Limit error");
+
if (inverse) {
myPosDst = (nbCarriers & 1 ? 0 : 1);
myPosSrc = 0;
@@ -91,6 +100,13 @@ OfdmGenerator::OfdmGenerator(size_t nbSymbols,
myFftIn, myFftOut,
FFTW_BACKWARD, FFTW_MEASURE);
+ myCfrPostClip.resize(N);
+ myCfrPostFft.resize(N);
+ myCfrFft = fftwf_plan_dft_1d(N,
+ reinterpret_cast<FFT_TYPE*>(myCfrPostClip.data()),
+ reinterpret_cast<FFT_TYPE*>(myCfrPostFft.data()),
+ FFTW_FORWARD, FFTW_MEASURE);
+
if (sizeof(complexf) != sizeof(FFT_TYPE)) {
printf("sizeof(complexf) %zu\n", sizeof(complexf));
printf("sizeof(FFT_TYPE) %zu\n", sizeof(FFT_TYPE));
@@ -115,6 +131,10 @@ OfdmGenerator::~OfdmGenerator()
if (myFftPlan) {
fftwf_destroy_plan(myFftPlan);
}
+
+ if (myCfrFft) {
+ fftwf_destroy_plan(myCfrFft);
+ }
}
int OfdmGenerator::process(Buffer* const dataIn, Buffer* dataOut)
@@ -157,7 +177,11 @@ int OfdmGenerator::process(Buffer* const dataIn, Buffer* dataOut)
memcpy(&myFftIn[myNegDst], &in[myNegSrc],
myNegSize * sizeof(FFT_TYPE));
- fftwf_execute(myFftPlan);
+ fftwf_execute(myFftPlan); // IFFT from myFftIn to myFftOut
+
+ if (myCfr) {
+ cfr_one_iteration(dataOut, i);
+ }
memcpy(out, myFftOut, mySpacing * sizeof(FFT_TYPE));
@@ -167,3 +191,99 @@ int OfdmGenerator::process(Buffer* const dataIn, Buffer* dataOut)
return sizeOut;
}
+void OfdmGenerator::cfr_one_iteration(Buffer *symbols, size_t symbol_ix)
+{
+ complexf* out = reinterpret_cast<complexf*>(symbols->getData());
+
+ out += (symbol_ix * mySpacing);
+
+ // use std::norm instead of std::abs to avoid calculating the
+ // square roots
+ const float clip_squared = myCfrClip * myCfrClip;
+
+ // Clip
+ for (size_t i = 0; i < mySpacing; i++) {
+ const float mag_squared = std::norm(out[i]);
+ if (mag_squared > clip_squared) {
+ // normalise absolute value to myCfrClip:
+ // x_clipped = x * clip / |x|
+ // = x * sqrt(clip_squared) / sqrt(mag_squared)
+ // = x * sqrt(clip_squared / mag_squared)
+ out[i] *= std::sqrt(clip_squared / mag_squared);
+ }
+ }
+
+ // Take FFT of our clipped signal
+ std::copy(out, out + mySpacing, myCfrPostClip.begin());
+ fftwf_execute(myCfrFft); // FFT from myCfrPostClip to myCfrPostFft
+
+ // Calculate the error in frequency domain by subtracting our reference
+ // and clip it to myCfrErrorClip. By adding this clipped error signal
+ // to our FFT output, we compensate the introduced error to some
+ // extent.
+ const float err_clip_squared = myCfrErrorClip * myCfrErrorClip;
+
+ complexf *reference = reinterpret_cast<complexf*>(myFftIn);
+ for (size_t i = 0; i < mySpacing; i++) {
+ complexf error = myCfrPostFft[i] - reference[i];
+
+ const float mag_squared = std::norm(error);
+ if (mag_squared > err_clip_squared) {
+ error *= std::sqrt(err_clip_squared / mag_squared);
+ }
+
+ // Update the reference in-place to avoid another copy for the
+ // subsequence IFFT
+ reference[i] += error;
+ }
+
+ // Run our error-compensated symbol through the IFFT again
+ fftwf_execute(myFftPlan); // IFFT from myFftIn to myFftOut
+
+}
+
+
+void OfdmGenerator::set_parameter(const std::string& parameter,
+ const std::string& value)
+{
+ using namespace std;
+ stringstream ss(value);
+ ss.exceptions ( stringstream::failbit | stringstream::badbit );
+
+ if (parameter == "cfr") {
+ ss >> myCfr;
+ }
+ else if (parameter == "clip") {
+ ss >> myCfrClip;
+ }
+ else if (parameter == "errorclip") {
+ ss >> myCfrErrorClip;
+ }
+ else {
+ stringstream ss;
+ ss << "Parameter '" << parameter
+ << "' is not exported by controllable " << get_rc_name();
+ throw ParameterError(ss.str());
+ }
+}
+
+const std::string OfdmGenerator::get_parameter(const std::string& parameter) const
+{
+ using namespace std;
+ stringstream ss;
+ if (parameter == "cfr") {
+ ss << myCfr;
+ }
+ else if (parameter == "clip") {
+ ss << std::fixed << myCfrClip;
+ }
+ else if (parameter == "errorclip") {
+ ss << std::fixed << myCfrErrorClip;
+ }
+ else {
+ ss << "Parameter '" << parameter <<
+ "' is not exported by controllable " << get_rc_name();
+ throw ParameterError(ss.str());
+ }
+ return ss.str();
+}
diff --git a/src/OfdmGenerator.h b/src/OfdmGenerator.h
index a8c3c19..9a6fa01 100644
--- a/src/OfdmGenerator.h
+++ b/src/OfdmGenerator.h
@@ -2,7 +2,7 @@
Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2011 Her Majesty
the Queen in Right of Canada (Communications Research Center Canada)
- Copyright (C) 2016
+ Copyright (C) 2017
Matthias P. Braendli, matthias.braendli@mpb.li
http://opendigitalradio.org
@@ -32,38 +32,61 @@
#include "porting.h"
#include "ModPlugin.h"
-
+#include "RemoteControl.h"
#include "fftw3.h"
-
#include <sys/types.h>
+#include <vector>
+#include <complex>
+typedef std::complex<float> complexf;
-class OfdmGenerator : public ModCodec
+class OfdmGenerator : public ModCodec, public RemoteControllable
{
-public:
- OfdmGenerator(size_t nbSymbols, size_t nbCarriers, size_t spacing, bool inverse = true);
- virtual ~OfdmGenerator();
- OfdmGenerator(const OfdmGenerator&);
- OfdmGenerator& operator=(const OfdmGenerator&);
-
-
- int process(Buffer* const dataIn, Buffer* dataOut);
- const char* name() { return "OfdmGenerator"; }
-
-protected:
- fftwf_plan myFftPlan;
- fftwf_complex *myFftIn, *myFftOut;
- size_t myNbSymbols;
- size_t myNbCarriers;
- size_t mySpacing;
- unsigned myPosSrc;
- unsigned myPosDst;
- unsigned myPosSize;
- unsigned myNegSrc;
- unsigned myNegDst;
- unsigned myNegSize;
- unsigned myZeroDst;
- unsigned myZeroSize;
+ public:
+ OfdmGenerator(size_t nbSymbols,
+ size_t nbCarriers,
+ size_t spacing,
+ bool inverse = true);
+ virtual ~OfdmGenerator();
+ OfdmGenerator(const OfdmGenerator&) = delete;
+ OfdmGenerator& operator=(const OfdmGenerator&) = delete;
+
+ int process(Buffer* const dataIn, Buffer* dataOut) override;
+ const char* name() override { return "OfdmGenerator"; }
+
+ /* Functions for the remote control */
+ /* Base function to set parameters. */
+ virtual void set_parameter(
+ const std::string& parameter,
+ const std::string& value) override;
+
+ /* Getting a parameter always returns a string. */
+ virtual const std::string get_parameter(
+ const std::string& parameter) const override;
+
+ protected:
+ void cfr_one_iteration(Buffer *symbols, size_t symbol_ix);
+
+ fftwf_plan myFftPlan;
+ fftwf_complex *myFftIn, *myFftOut;
+ size_t myNbSymbols;
+ size_t myNbCarriers;
+ size_t mySpacing;
+ unsigned myPosSrc;
+ unsigned myPosDst;
+ unsigned myPosSize;
+ unsigned myNegSrc;
+ unsigned myNegDst;
+ unsigned myNegSize;
+ unsigned myZeroDst;
+ unsigned myZeroSize;
+
+ bool myCfr; // Whether to enable crest factor reduction
+ float myCfrClip;
+ float myCfrErrorClip;
+ fftwf_plan myCfrFft;
+ std::vector<complexf> myCfrPostClip;
+ std::vector<complexf> myCfrPostFft;
};
generated by cgit v1.2.3 (git 2.39.1) at 2024-09-21 10:29:59 +0000