Blind channel identification for multirate precoding and OFDM systems

Algorithms are proposed for blind estimation of frequency selective channels in a multirate precoding communications system. These methods exploit the cyclostationarity induced by a filter-bank structure at the transmitter to identify FIR nonminimum phase channels without higher-order statistics or fractional-sampling. As an example, OFDM systems are considered with and without the cyclic prefix. Some redundancy, independent of the channel memory, is shown to be necessary for OFDM and other orthonormal transformation systems for blind channel identification. Methods of blind channel estimation for more general transform modulations are also supported in this framework. Monte Carlo simulations are used to provide examples of performance.