Iterative decoding networks with iteratively data eliminating SDD and EM based channel state estimator

The paper establishes a general framework for iterative separate CSE in general iterative decoding networks. Two particular cases of CSE are examined - SDD (soft-decision directed) and EM (expectation-maximization) based one. Both have capabilities for exploiting the iteratively improved backward measure from the decoding network, however both exhibit different properties and provide different possibilities for iteration scenarios. An example application with simple serially concatenated code with QPSK mapping in AWGN channel with phase rotation is investigated to demonstrate the differences between the algorithms in terms of MSE, ambiguity resolution, and convergence behavior.