Performance evaluation of Code-Spread OFDM with error control coding

Orthogonal Frequency Division Multiplexing (OFDM) is a popular technique used to combat frequency selective fading in multipath channels. When spectral nulls are present in the channel, they can severely degrade or cancel out OFDM tones, resulting in an irreducible error rate. To combat this, standards typically employ forward error correction (FEC) techniques. Code-Spread OFDM (CS-OFDM) combines the characteristics of OFDM and Code Division Multiple Access (CDMA) to create a more robust modulation scheme which provides substantial performance improvements relative to standard OFDM. In CS-OFDM, each sinewave carries a weighted sum of all the information symbols being transmitted in an OFDM block interval. In this paper, the MMSE estimator is derived for each symbol for a number of cases, including when the number of carriers is greater than the number of symbols. The performance of both OFDM and CS-OFDM are evaluated with and without error control coding using the FEC techniques typically employed in OFDM standards.