DFT spreading of modulation symbols reduces PAPR

  • In OFDM, each modulation symbols “sees” a single 15 kHz subcarrier (flat channel)
  • In SC-FD-A, each modulation symbol “sees” a wider bandwidth (i.e. mx 180 KHz)
  • Equalization is required in the SC-FDMA receiver
DFT-spread OFDM (DFTS-OFDM) is a transmission scheme that can combine the desired properties discussed in the previous sections, i.e.:
• Small variations in the instantaneous power of the transmitted signal (‘singlecarrier’ property).
• Possibility for low-complexity high-quality equalization in the frequency domain.
• Possibility for FDMA with flexible bandwidth assignment.
Due to these properties, DFTS-OFDM has been selected as the uplink transmission scheme for LTE.