Iterative EM Based IMD Synchronization for Fast Time-Variant Channel with Subspace Order Recursive LS Iterator

We solve the problem of iterative expectation-maximization (EM) based information measure directed (IMD) synchronization in fast time-variant environment. We identified correspondence between the EM iterator and the weighted least squares (LS) problem. An order recursive form of the LS iterator reduces the implementation complexity. The channel coefficients are allowed to change arbitrarily up to the granularity of the symbol period. The coefficients are modeled using parametric subspace providing a wide range of configuration for the channel dynamics while reducing the dimensionality of the problem substantially