Wednesday, January 12, 2011

Using SC-FDMA in LTE


     Single carrier frequency division multiple access (SC-FDMA) has been adopted by the third generation partnership project (3GPP) for uplink transmission in technology standardized for long term evolution (LTE) of cellular systems.SC-FDMA was chosen because it combines the low PAPR techniques of single-carrier transmission systems, such as GSM and CDMA, with the multi-path resistance and flexible frequency allocation of OFDMA. 
 
     Data symbols in the time domain are converted to the frequency domain using a discrete Fourier transform (DFT).Then in the frequency domain they are mapped to the desired location in the overall channel bandwidth before being converted back to the time domain using an inverse FFT (IFFT).

     
Finally, the CP is inserted. Because SC-FDMA uses this technique, it is sometimes called discrete Fourier transform spread OFDM or (DFT-SOFDM).



 OFDMA Vs. SC-FDMA

      It is the parallel transmission of multiple symbols that creates the undesirable high PAR of OFDMA.By transmitting the M data symbols in series at M times the rate, the SC-FDMA occupied bandwidth is the same as multi-carrier OFDMA.

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