00001 00035 #include <itpp/comm/ofdm.h> 00036 #include <itpp/base/specmat.h> 00037 #include <itpp/base/transforms.h> 00038 #include <itpp/base/operators.h> 00039 00040 00041 namespace itpp { 00042 00043 OFDM::OFDM(int inNfft, int inNcp, int inNupsample) 00044 { 00045 set_parameters(inNfft, inNcp, inNupsample); 00046 } 00047 00048 void OFDM::set_parameters(const int inNfft, const int inNcp, const int inNupsample){ 00049 it_assert(inNfft >= 2, "OFDM: Nfft must be >=2."); 00050 it_assert(inNcp >= 0 && inNcp <= inNfft, "OFDM: Ncp must be >=0 and <=Nfft."); 00051 it_assert(inNupsample >= 1 && inNupsample <= 100, "OFDM: Ncp must be >=1 and <=100."); 00052 Nfft = inNfft; 00053 Ncp = inNcp; 00054 Nupsample = inNupsample; 00055 norm_factor = std::sqrt(static_cast<double>(Nupsample*Nfft*Nfft) / (Nfft+Ncp)); 00056 setup_done = true; 00057 } 00058 00059 void OFDM::modulate(const cvec &input, cvec &output){ 00060 it_assert(setup_done == true, "OFDM::modulate: You must set the length of the FFT and the cyclic prefix!"); 00061 const int N = input.length() / Nfft; 00062 it_assert(N*Nfft == input.length(), "OFDM::modulate: Length of input vector is not a multiple of Nfft."); 00063 00064 output.set_length(Nupsample*N*(Nfft+Ncp)); 00065 cvec outtemp(Nfft); 00066 00067 for (int i = 0; i < N; i++) { 00068 outtemp = ifft(concat(input.mid(i*Nfft, Nfft/2), zeros_c(Nfft*(Nupsample-1)), 00069 input.mid(i*Nfft+Nfft/2, Nfft/2))) * norm_factor; 00070 output.replace_mid(Nupsample*(Nfft+Ncp)*i, concat(outtemp.right(Nupsample*Ncp), outtemp)); 00071 } 00072 } 00073 00074 cvec OFDM::modulate(const cvec &input) 00075 { 00076 cvec output; 00077 modulate(input, output); 00078 return output; 00079 } 00080 00081 void OFDM::demodulate(const cvec& input, cvec &output){ 00082 it_assert(setup_done == true, "OFDM::demodulate: You must set the length of the FFT and the cyclic prefix!"); 00083 const int N = input.length() / (Nfft+Ncp) / Nupsample; 00084 it_assert(Nupsample*N*(Nfft+Ncp) == input.length(), "OFDM: Length of input vector is not a multiple of Nfft+Ncp."); 00085 00086 output.set_length(N*Nfft); 00087 // normalize also taking the energy loss into the cyclic prefix into account 00088 for (int i = 0; i < N; i++) { 00089 cvec x = fft(input.mid(Nupsample*(i*(Nfft+Ncp)+Ncp), Nupsample*Nfft)); 00090 output.replace_mid(Nfft*i, concat(x.left(Nfft/2), x.right(Nfft/2)) / norm_factor); 00091 } 00092 } 00093 00094 cvec OFDM::demodulate(const cvec &input){ 00095 cvec output; 00096 demodulate(input, output); 00097 return output; 00098 } 00099 00100 } //namespace itpp
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