ofdm.cpp
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#include <itpp/comm/ofdm.h>
#include <itpp/base/specmat.h>
#include <itpp/base/operators.h>
#include <itpp/signal/transforms.h>
namespace itpp
{
OFDM::OFDM(int inNfft, int inNcp, int inNupsample)
{
set_parameters(inNfft, inNcp, inNupsample);
}
void OFDM::set_parameters(const int inNfft, const int inNcp, const int inNupsample)
{
it_assert(inNfft >= 2, "OFDM: Nfft must be >=2.");
it_assert(inNcp >= 0 && inNcp <= inNfft, "OFDM: Ncp must be >=0 and <=Nfft.");
it_assert(inNupsample >= 1 && inNupsample <= 100, "OFDM: Ncp must be >=1 and <=100.");
Nfft = inNfft;
Ncp = inNcp;
Nupsample = inNupsample;
norm_factor = std::sqrt(static_cast<double>(Nupsample * Nfft * Nfft) / (Nfft + Ncp));
setup_done = true;
}
void OFDM::modulate(const cvec &input, cvec &output)
{
it_assert(setup_done == true, "OFDM::modulate: You must set the length of the FFT and the cyclic prefix!");
const int N = input.length() / Nfft;
it_assert(N*Nfft == input.length(), "OFDM::modulate: Length of input vector is not a multiple of Nfft.");
output.set_length(Nupsample*N*(Nfft + Ncp));
cvec outtemp(Nfft);
for (int i = 0; i < N; i++) {
outtemp = ifft(concat(input.mid(i * Nfft, Nfft / 2), zeros_c(Nfft * (Nupsample - 1)),
input.mid(i * Nfft + Nfft / 2, Nfft / 2))) * norm_factor;
output.replace_mid(Nupsample*(Nfft + Ncp)*i, concat(outtemp.right(Nupsample*Ncp), outtemp));
}
}
cvec OFDM::modulate(const cvec &input)
{
cvec output;
modulate(input, output);
return output;
}
void OFDM::demodulate(const cvec& input, cvec &output)
{
it_assert(setup_done == true, "OFDM::demodulate: You must set the length of the FFT and the cyclic prefix!");
const int N = input.length() / (Nfft + Ncp) / Nupsample;
it_assert(Nupsample*N*(Nfft + Ncp) == input.length(), "OFDM: Length of input vector is not a multiple of Nfft+Ncp.");
output.set_length(N*Nfft);
// normalize also taking the energy loss into the cyclic prefix into account
for (int i = 0; i < N; i++) {
cvec x = fft(input.mid(Nupsample * (i * (Nfft + Ncp) + Ncp), Nupsample * Nfft));
output.replace_mid(Nfft*i, concat(x.left(Nfft / 2), x.right(Nfft / 2)) / norm_factor);
}
}
cvec OFDM::demodulate(const cvec &input)
{
cvec output;
demodulate(input, output);
return output;
}
} //namespace itpp
itpp::OFDM::modulate
cvec modulate(const cvec &input)
Modulate complex data symbols. Length of input must be an integer multiple of Nfft.
Definition ofdm.cpp:73
itpp::OFDM::OFDM
OFDM(void)
Empty constructor.
Definition ofdm.h:50
itpp::OFDM::set_parameters
void set_parameters(const int Nfft, const int Ncp, const int inNupsample=1)
Set parameters.
Definition ofdm.cpp:45
it_assert
#define it_assert(t, s)
Abort if t is not true.
Definition itassert.h:94
itpp::length
int length(const Vec< T > &v)
Length of vector.
Definition matfunc.h:51
itpp
itpp namespace
Definition itmex.h:37
ofdm.h
Interface of an Orthogonal Frequency Division Multiplex (OFDM) class.
operators.h
Definitions of operators for vectors and matricies of different types.
specmat.h
Definitions of special vectors and matrices.
transforms.h
Fourier, Hadamard, Walsh-Hadamard, and 2D Hadamard transforms - header file.

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