| 摘要 |
<p>Symbols (y(n - L)) in a symbol sequence transmitted via a fading channel are estimated (S/< ANd >(n - L)) in an equalizer having a channel estimating filter (CEST). An error signal (e(n)) influences an adaptation circuit (10) which controls adjustable coefficients (7) so as to form a channel estimate (c1(n), c2(n), c3(n)), which is adapted during the whole of the symbol sequence. The adaptation circuit (10) performs an adaptation algorithm, which is influenced by mean energy values (U(n)) obtained from the channel estimate in a mean-value-forming circuit (15). Subsequent to fading the adaptation algorithm is able to control the coefficients (7) so that one of the coefficients will erroneously dominate the channel estimate, with erroneous estimation of symbols (S/< ANd >(n - L)) as a result. This is counteracted by selecting the largest of the mean energy values (U(n)), this largest value influencing the adaptation algorithm (10). When the signal strength of the transmitted symbols falls beneath a threshold value, the coefficient which dominated the channel estimate, for instance the first coefficient (c1(n)), is sustained to also dominate after fading and the remaining coefficients are set to zero.</p> |
