Pulse or digital communications – Receivers – Interference or noise reduction
Patent
1992-09-09
1995-11-07
Chin, Stephen
Pulse or digital communications
Receivers
Interference or noise reduction
375348, 455 63, H03D 106, H04B 110
Patent
active
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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Gudmundson Perols B. O.
Larsson Lars G.
Chin Stephen
Ghebretinsae T.
Telefonaktiebolaget LM Ericsson
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