and Modified Covariance), the strongest influence on the achievable extrapolation parameter estimation (EM and RELAXation spectral length for these types of channel came from the relation estimator (RELAX)), and subspace parameter estimation between the length of the observation interval over which (ESPRIT, Unitary ESPRIT, root-MUSIC) or on adaptive the data is known and the actual number of scatterers. filter algorithms, derived from autoregressive modelling. Channels with relatively high densities of scatterers or The adaptive filter algorithms comprised Modified Co- diffusely scattered components pose severe problems for variance, Least Mean Squares algorithm (LMS), the subspace-based spectral estimation schemes, see also Normalised Least Mean Squares algorithm (NLMS), Besson and Stoica [BeSt00], demanding impractically Affine Projection (AfP), Recursive Least Squares algo- long data interval lengths over which stationarity of the rithm (RLS), and Q-R decomposition-based Recursive channel cannot be guaranteed. As a rule of thumb, for Least Squares algorithm (QR-RLS). The comparison was a prediction length of one wavelength, the length of the made on synthetic data and measured data. Synthetic data data interval in wavelengths should equal at least half the was generated according to either the well-known Jakes number of scatterers in the channel, for noise-free cases. model, using nine scatterers giving a small set of de- The fundamental reason for this is that the well-known terministic well-separated Doppler shifts, or the sto- reciprocal relation between resolution in time and that in chastic Dersch-model developed for the Research and frequency limits the accuracy of the Doppler estimation Technology Development in Advanced Communication on short intervals. The maximum achievable prediction Technologies (RACE) Code Division Testbed RACE length depends mainly on this accuracy. Besides, one of Project (CoDiT) project that only specifies temporal the consequences is that the best prediction schemes for correl