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 several OFDM tones, resulting in an irreducible error rate. Code-Spreaded 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, an 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 CS-OFDM is analyzed and shown to provide substantial improvements relative to standard OFDM, especially in the latter case.

Date Published: 3 April 2008
PDF: 8 pages
Proc. SPIE 6980, Wireless Sensing and Processing III, 698004 (3 April 2008); doi: 10.1117/12.784456

Published in SPIE Proceedings Vol. 6980:
Wireless Sensing and Processing III
Sohail A. Dianat; Michael D. Zoltowski, Editor(s)