diff options
Diffstat (limited to 'src/OfdmGenerator.cpp')
| -rw-r--r-- | src/OfdmGenerator.cpp | 73 |
1 files changed, 46 insertions, 27 deletions
diff --git a/src/OfdmGenerator.cpp b/src/OfdmGenerator.cpp index 3d3dfd7..41c1c85 100644 --- a/src/OfdmGenerator.cpp +++ b/src/OfdmGenerator.cpp @@ -26,6 +26,8 @@ #include "OfdmGenerator.h" #include "PcDebug.h" + +#include <complex> #include "fftw3.h" #define FFT_TYPE fftwf_complex @@ -33,23 +35,25 @@ #include <string.h> #include <stdexcept> #include <assert.h> -#include <complex> #include <string> OfdmGenerator::OfdmGenerator(size_t nbSymbols, - size_t nbCarriers, - size_t spacing, - bool inverse) : + size_t nbCarriers, + size_t spacing, + bool enableCfr, + float cfrClip, + float cfrErrorClip, + bool inverse) : ModCodec(), RemoteControllable("ofdm"), myFftPlan(nullptr), myFftIn(nullptr), myFftOut(nullptr), myNbSymbols(nbSymbols), myNbCarriers(nbCarriers), mySpacing(spacing), - myCfr(false), - myCfrClip(1.0f), - myCfrErrorClip(1.0f), + myCfr(enableCfr), + myCfrClip(cfrClip), + myCfrErrorClip(cfrErrorClip), myCfrFft(nullptr) { PDEBUG("OfdmGenerator::OfdmGenerator(%zu, %zu, %zu, %s) @ %p\n", @@ -62,8 +66,8 @@ OfdmGenerator::OfdmGenerator(size_t nbSymbols, /* 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"); + RC_ADD_PARAMETER(clip, "CFR: Clip to amplitude"); + RC_ADD_PARAMETER(errorclip, "CFR: Limit error"); if (inverse) { myPosDst = (nbCarriers & 1 ? 0 : 1); @@ -100,11 +104,10 @@ OfdmGenerator::OfdmGenerator(size_t nbSymbols, myFftIn, myFftOut, FFTW_BACKWARD, FFTW_MEASURE); - myCfrPostClip.resize(N); - myCfrPostFft.resize(N); + myCfrPostClip = (FFT_TYPE*)fftwf_malloc(sizeof(FFT_TYPE) * N); + myCfrPostFft = (FFT_TYPE*)fftwf_malloc(sizeof(FFT_TYPE) * N); myCfrFft = fftwf_plan_dft_1d(N, - reinterpret_cast<FFT_TYPE*>(myCfrPostClip.data()), - reinterpret_cast<FFT_TYPE*>(myCfrPostFft.data()), + myCfrPostClip, myCfrPostFft, FFTW_FORWARD, FFTW_MEASURE); if (sizeof(complexf) != sizeof(FFT_TYPE)) { @@ -167,6 +170,9 @@ int OfdmGenerator::process(Buffer* const dataIn, Buffer* dataOut) "OfdmGenerator::process output size not valid!"); } + myNumClip = 0; + myNumErrorClip = 0; + for (size_t i = 0; i < myNbSymbols; ++i) { myFftIn[0][0] = 0; myFftIn[0][1] = 0; @@ -177,10 +183,17 @@ int OfdmGenerator::process(Buffer* const dataIn, Buffer* dataOut) memcpy(&myFftIn[myNegDst], &in[myNegSrc], myNegSize * sizeof(FFT_TYPE)); + std::vector<complexf> reference; + if (myCfr) { + reference.resize(mySpacing); + memcpy(reference.data(), myFftIn, mySpacing * sizeof(FFT_TYPE)); + } + fftwf_execute(myFftPlan); // IFFT from myFftIn to myFftOut if (myCfr) { - cfr_one_iteration(dataOut, i); + complexf *symbol = reinterpret_cast<complexf*>(myFftOut); + cfr_one_iteration(symbol, reference.data()); } memcpy(out, myFftOut, mySpacing * sizeof(FFT_TYPE)); @@ -188,33 +201,36 @@ int OfdmGenerator::process(Buffer* const dataIn, Buffer* dataOut) in += myNbCarriers; out += mySpacing; } + + if (myCfr) { + etiLog.level(debug) << "CFR: " << myNumClip << " clipped, " << + myNumErrorClip << " err clipped"; + } + return sizeOut; } -void OfdmGenerator::cfr_one_iteration(Buffer *symbols, size_t symbol_ix) +void OfdmGenerator::cfr_one_iteration(complexf *symbol, const complexf *reference) { - 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]); + const float mag_squared = std::norm(symbol[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); + symbol[i] *= std::sqrt(clip_squared / mag_squared); + myNumClip++; } } // Take FFT of our clipped signal - std::copy(out, out + mySpacing, myCfrPostClip.begin()); + memcpy(myCfrPostClip, symbol, mySpacing * sizeof(FFT_TYPE)); fftwf_execute(myCfrFft); // FFT from myCfrPostClip to myCfrPostFft // Calculate the error in frequency domain by subtracting our reference @@ -223,23 +239,26 @@ void OfdmGenerator::cfr_one_iteration(Buffer *symbols, size_t symbol_ix) // 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 complexf constellation_point = + reinterpret_cast<complexf*>(myCfrPostFft)[i]; + + complexf error = reference[i] - constellation_point; const float mag_squared = std::norm(error); if (mag_squared > err_clip_squared) { error *= std::sqrt(err_clip_squared / mag_squared); + myNumErrorClip++; } - // Update the reference in-place to avoid another copy for the + // Update the input to the FFT directl to avoid another copy for the // subsequence IFFT - reference[i] += error; + complexf *fft_in = reinterpret_cast<complexf*>(myFftIn); + fft_in[i] = constellation_point + error; } // Run our error-compensated symbol through the IFFT again fftwf_execute(myFftPlan); // IFFT from myFftIn to myFftOut - } |