Subspace recursive weighted LS solution of iterative synchronisation in time-variant channel

作者：Sykora Jan^*; Vcelak Jan

来源：European Transactions on Telecommunications, 2008, 19(6): 681-696.

DOI：10.1002/ett.1225

Expectation-Maximisation (EM) based iterative synchroniser is a particular form of the Information Measure Directed (IMD) synchroniser using a posteriori soft information from the iterative decoding network. We solve the problem of EM-based IMD synchronisation in the general fast time-variant channel. The channel coefficients are allowed to change arbitrarily up to the granularity of the symbol period. We have identified the correspondence between the EM iterator and the weighted least squares (LS) problem. This allows to Utilise a wide range of solutions developed for the LS problem. Particularly interesting is the subspace order recursive form of the LS iterator which reduces the implementation complexity. The parameter subspace in the estimator is modelled using a wide range of configuration. This allows consideration for the channel dynamics while reducing the dimensionality of the problem substantially when the model is properly matched to the real channel behaviour including an adaptive subspace dimension setting. The procedure is demonstrated on example systems with the estimation of phase and jointly amplitude and phase on serially concatenated coding scheme. We use realistic Jake's Doppler dynamics as an example for the true channel and variety of subspace models for the EM estimator.

• 出版日期2008-10