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ofdm.cpp
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1
31#include <itpp/comm/ofdm.h>
32#include <itpp/base/specmat.h>
33#include <itpp/base/operators.h>
35
36
37namespace itpp
38{
39
40OFDM::OFDM(int inNfft, int inNcp, int inNupsample)
41{
42 set_parameters(inNfft, inNcp, inNupsample);
43}
44
45void OFDM::set_parameters(const int inNfft, const int inNcp, const int inNupsample)
46{
47 it_assert(inNfft >= 2, "OFDM: Nfft must be >=2.");
48 it_assert(inNcp >= 0 && inNcp <= inNfft, "OFDM: Ncp must be >=0 and <=Nfft.");
49 it_assert(inNupsample >= 1 && inNupsample <= 100, "OFDM: Ncp must be >=1 and <=100.");
50 Nfft = inNfft;
51 Ncp = inNcp;
52 Nupsample = inNupsample;
53 norm_factor = std::sqrt(static_cast<double>(Nupsample * Nfft * Nfft) / (Nfft + Ncp));
54 setup_done = true;
55}
56
57void OFDM::modulate(const cvec &input, cvec &output)
58{
59 it_assert(setup_done == true, "OFDM::modulate: You must set the length of the FFT and the cyclic prefix!");
60 const int N = input.length() / Nfft;
61 it_assert(N*Nfft == input.length(), "OFDM::modulate: Length of input vector is not a multiple of Nfft.");
62
63 output.set_length(Nupsample*N*(Nfft + Ncp));
64 cvec outtemp(Nfft);
65
66 for (int i = 0; i < N; i++) {
67 outtemp = ifft(concat(input.mid(i * Nfft, Nfft / 2), zeros_c(Nfft * (Nupsample - 1)),
68 input.mid(i * Nfft + Nfft / 2, Nfft / 2))) * norm_factor;
69 output.replace_mid(Nupsample*(Nfft + Ncp)*i, concat(outtemp.right(Nupsample*Ncp), outtemp));
70 }
71}
72
73cvec OFDM::modulate(const cvec &input)
74{
75 cvec output;
76 modulate(input, output);
77 return output;
78}
79
80void OFDM::demodulate(const cvec& input, cvec &output)
81{
82 it_assert(setup_done == true, "OFDM::demodulate: You must set the length of the FFT and the cyclic prefix!");
83 const int N = input.length() / (Nfft + Ncp) / Nupsample;
84 it_assert(Nupsample*N*(Nfft + Ncp) == input.length(), "OFDM: Length of input vector is not a multiple of Nfft+Ncp.");
85
86 output.set_length(N*Nfft);
87 // normalize also taking the energy loss into the cyclic prefix into account
88 for (int i = 0; i < N; i++) {
89 cvec x = fft(input.mid(Nupsample * (i * (Nfft + Ncp) + Ncp), Nupsample * Nfft));
90 output.replace_mid(Nfft*i, concat(x.left(Nfft / 2), x.right(Nfft / 2)) / norm_factor);
91 }
92}
93
94cvec OFDM::demodulate(const cvec &input)
95{
96 cvec output;
97 demodulate(input, output);
98 return output;
99}
100
101} //namespace itpp
Class for modulating and demodulation of OFDM signals using the FFT.
Definition ofdm.h:47
cvec modulate(const cvec &input)
Modulate complex data symbols. Length of input must be an integer multiple of Nfft.
Definition ofdm.cpp:73
OFDM(void)
Empty constructor.
Definition ofdm.h:50
void set_parameters(const int Nfft, const int Ncp, const int inNupsample=1)
Set parameters.
Definition ofdm.cpp:45
#define it_assert(t, s)
Abort if t is not true.
Definition itassert.h:94
int length(const Vec< T > &v)
Length of vector.
Definition matfunc.h:51
itpp namespace
Definition itmex.h:37
Interface of an Orthogonal Frequency Division Multiplex (OFDM) class.
Definitions of operators for vectors and matricies of different types.
Definitions of special vectors and matrices.
Fourier, Hadamard, Walsh-Hadamard, and 2D Hadamard transforms - header file.
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