A method includes receiving signals transmitted over a communication channel in multiple blocks transmitted in respective frequency bins during respective time intervals. An estimate of the communication channel, for a given block transmitted during a respective time interval, is computed by (i) computing respective interim filtering results for the blocks transmitted in the respective time interval in the respective frequency bins belonging to the predefined subset, by filtering a first group of the reference signals that are transmitted in odd-order frequency bins and in a first set of symbols, so as to produce odd-order interim filtering results, and filtering a second group of the reference signals that are transmitted in even-order frequency bins and in a second set of symbols that does not overlap the first set, so as to produce even-order interim filtering results; and (ii) combining the odd-order interim filtering results and the even-order interim filtering results.