Real-time ML estimation of very frequency selective multipath channels

It is shown that the inverse filter is a good solution for estimating multipath channels when using binary sequences as the input signal. It is a maximum-likelihood estimator which enables the utilization of aperiodic sequences (bursts). Therefore, it is well suited for estimating very-frequency-selective channels. Since the channel is only occupied during short time intervals, it maintains compatibility with other services when measuring in occupied frequency bands. A practical realization shows that inverse-filter-based estimation techniques are well suited for implementing real-time channel sounders. The inverse filter is realized in SAW (surface acoustic wave) techniques. The implementation loss of 2.5 to 3.5 dB for the POP (peak/off peak) ratio shows that its realization is not particularly critical. The sounder estimates either full impulse responses or statistical parameters at a rate of 9 or 2.2 impulse responses per second, respectively. Relevant parameters characterizing the mobile radio channel are proposed