Blind Equalization of COFDM Systems Based on the Minimization of a Quadratic Criterion

• Published in: International Workshop on HDTV '96 pp. 311 - 319
• Main Authors: Madec, Philippe, de Courville, Marc, Duhamel, Pierre
• Format: Conference Proceeding
• Language: English
• Published: SMPTE 01.10.1996
• ISBN: 1614829470; 9781614829478
• DOI: 10.5594/M001263

The COFDM concept has recently been applied to the design of DFT-based digital modulations for use over frequency selective channels. The cyclic convolution property of the DFT enables a low complexity equalization scheme at the expense of bandwidth efficiency since a "guard time" is required. Moreover this technique is very specific to DFT-based OFDM systems. As digital modulations generate continuous signals after baseband level digital filtering, non-critical sampling is recommended, that is, some zero symbols must be appended to the block of symbols to be modulated. As shown in [10], minimizing a quadratic criterion based on the subband components of the received signal that should be null is sufficient to perform (blind) equalization. Therefore less channel capacity is lost since neither a guard time nor reference symbols are required. The performance of a linear equalizer using this criterion is studied here for COFDM systems with 64-QAM subcarrier modulation.