Adaptive sequence estimation for digital cellular radio channels
AssigneeLucent Technologies Inc.
InventorsStephen Russell Huszar, Nambirajan Seshadri
Life of this patent
Estimating the term…
Abstract
An equalizer/decoder for a communication channel presenting impairments to error-free reception of transmitted symbols includes a modified Viterbi decoder operating on samples of received signals in a plurality of equivalent subchannels. Estimates of each of the subchannels are updated using a locally best estimate in the Viterbi trellis processing, thereby avoiding delay in updating channel estimates in a rapidly changing channel such as a digital cellular communications channels. A leaky predictor channel updating technique also proves advantageous in an alternative embodiment.
Claims13
A method for decoding time varying signals comprising:
- receiving a time varying signal, r(t), from a communications channel, which signal represents a sequence of symbols, c.sub.k, k=1,2,3, . . . , supplied to said communications channel with a symbol interval T, sampling r(t) at a rate R/T, with R>=2, to produce a set of R samples r.sub.k (l), l=1,2, . . . , R, during a kth symbol interval T,
- for each of a set of candidate (M+1)-symbol sequences, c.sub.k-M, c.sub.k-(M-1), . . . , c.sub.k-1, c.sub.k, generating a set of R values, s.sub.k (l), l=1,2 . . . , R, representing partial estimates of an output of said channel,
- forming an error signal reflecting the difference between each of r.sub.k (l) and s.sub.k (l), 1!l=1,2, . . . ,R, for each of said candidate sequences, and selecting as the sequence of symbols supplied to said communications channel the candidate sequence which yields the lowest value for said error signal.
A method for decoding time varying signals comprising:
- receiving a time varying signal, r(t), from a communications channel, which signal represents a sequence of symbols, c.sub.k, k=1,2,3, . . . , supplied to said communications channel with a symbol interval T,
- sampling r(t) at a rate R/T, with R>1, to produce a set of R sequences r.sub.k (l), l=1,2, . . . , R, during a kth symbol interval T,
- generating a set of R values, s.sub.k (l), l=1,2 . . . ,R, each representing a partial estimate of an output of said channel,
- forming an error signal reflecting the difference between each of r.sub.k (l) and s.sub.k (l), 1!l=1,2, . . . ,R, for each of said candidate sequences, and selecting as the sequence of symbols supplied to said communications channel the candidate sequence which yields the lowest value for said error signal.
Dependencies are inferred from the claim text.