Decision Directed and Constant Modulus Algorithms Derived and Evaluated for Multicarrier Systems

The purpose of this research is to derive and examine blind adaptive algorithms for equalizing multicarrier (MC) communication systems and analyze how they performunder varying environmental conditions and parametric variations, focusing on equalizersset in cascade with the channel. Two well-accepted and widely-known cost functions,Decision Directed (DD) and Constant Modulus (CM), are applied to the MC signalstructure, and gradient descent algorithms based on both DD and CM functions arederived, analyzed and compared. Comparison of the new algorithms, Multi CarrierDecision Directed (MCDD) and Multi Carrier Constant Modulus (MCCM), focuses ondetailing how each algorithm performs when the factors of noise power and symbolsynchronization are varied. Additionally, a Frequency Domain Equalizer (FEQ) isdeveloped and employed to de-rotate and resize the output symbol constellation. BothMCDD and MCCM are compared against other blind and trained adaptive MCequalization algorithms in the areas of bit error rate (BER) vs. signal to noise ratio (SNR)and BER vs. synchronization delay. Results are presented showing that MCDD andMCCM perform worse than a MC Trained (MCT) approach but better than bothMulticarrier Equalization by Restoration of Redundancy (MERRY) and Carrier NullingAlgorithm (CNA).