GNU Radio 3.6.5 C++ API

Schmidl & Cox synchronisation for OFDM. More...
#include <digital_ofdm_sync_sc_cfb.h>
Public Member Functions  
~digital_ofdm_sync_sc_cfb ()  
Friends  
DIGITAL_API digital_ofdm_sync_sc_cfb_sptr  digital_make_ofdm_sync_sc_cfb (int fft_len, int cp_len, bool use_even_carriers) 
Schmidl & Cox synchronisation for OFDM.
Input: complex samples. Output 0: Fine frequency offset, scaled by the OFDM symbol duration. This is in [1]. The normalized frequency offset is then 2.0*output0/fft_len. Output 1: Beginning of the first OFDM symbol after the first (doubled) OFDM symbol. The beginning is marked with a 1 (it's 0 everywhere else).
The evaluation of the coarse frequency offset is *not* done in this block. Also, the initial equalizer taps are not calculated here.
Note that we use a different normalization factor in the timing metric than the authors do in their original work[1]. If the timing metric (8) is
we calculate the normalization as
i.e., we estimate the energy from *both* halfsymbols. This avoids spurious detects at the end of a burst, when the energy level suddenly drops.
[1] Schmidl, T.M. and Cox, D.C., "Robust frequency and timing synchronization for OFDM", Communications, IEEE Transactions on, 1997.
digital_ofdm_sync_sc_cfb::~digital_ofdm_sync_sc_cfb  (  ) 
DIGITAL_API digital_ofdm_sync_sc_cfb_sptr digital_make_ofdm_sync_sc_cfb  (  int  fft_len, 
int  cp_len,  
bool  use_even_carriers  
)  [friend] 
fft_len  FFT length 
cp_len  Length of the guard interval (cyclic prefix) in samples 
use_even_carriers  If true, the carriers in the sync preamble are occupied such that the even carriers are used (0, 2, 4, ...). If you use all carriers, that would include the DC carrier, so be careful. 