Method of forming a channel estimate for a time-varying radio ch

Pulse or digital communications – Receivers – Interference or noise reduction

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375348, 455 63, H03D 106, H04B 110

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054652766

ABSTRACT:
Radio signals are transmitted over a fading radio channel and are filtered and sampled in a receiver to obtain a digital signal. A channel equalizer has an equalizing filter in which a channel estimate is formed with the aid of a known synchronizing sequence. A Viterbi analyzer decides symbols with the aid of the channel estimate. An estimated time derivative of the channel estimate is formed and adapted with the aid of the decided symbols. The channel estimate is adapted to the radio channel by the derivative estimate and the decided symbols. In the event of fading with rapidly varying signal strength, the channel estimate is adapted slowly and is predicted mainly through the derivative estimate which varies relatively evenly. The digital signal is stored in a memory and an initial value is formed for the derivative estimate as a difference between two known channel estimates divided by a time difference therebetween. The known channel estimate may belong to two separate synchronizing sequences or may belong to one synchronizing sequence and a fading time point in which the channel estimate has zero value.

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