US 5,432,821 AGranted

System and method for estimating data sequences in digital transmissions

AssigneeUniversity of Southern California

InventorsAndreas Polydoros, Riccardo Raheli

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Abstract

A method for selecting the best survivor from a plurality of surviving possible distal data symbols creates a channel estimate for each of the survivors independent of the others. The likelihood of each survivor is then evaluated, whereupon the most likely survivor is selected. The likelihood of each survivor is computed based only on its own channel estimate. A data sequence estimation system includes a memory for storing a plurality of "surviving" sequences. For each stored survivor, the system includes a channel estimator and a metrics computer, which calculates a measure of the likelihood of the survivor as a function of the survivor itself, the observed input, and the parameters of the associated channel estimator. The system also includes a processor that accumulates the metric and selects a best survivor as a function of a computed maximum likelihood. There is no need to feed back the best survivor to update a single channel estimator, since, when the survivor has been selected, the associated channel estimator is already established.

Claims12

Dependent claims

A system for estimating data sequences in digital transmissions, with a transmission channel and a received observed digital signal y.sub.k comprising:

a survivor memory circuit for storing a digital representation of each of a plurality of N possible data paths as a sequence of N initial survivor sequences s.sub.1, . . . , s.sub.N, where N is an integer;
for each initial survivor sequence, an individual channel estimator;
for each initial survivor sequence, an individual transition metrics computation circuit for computing a transition metric from the initial survivor sequence at a time k to each of a plurality of data states at a time k+1;
an accumulated metrics computation circuit for cumulatively computing and storing accumulated metrics for each initial survivor sequence plus each associated transition metric up to time k+1;
a survivor selection circuit for selecting candidate survivor sequences from among the initial survivor sequences stored in the accumulated metrics computation circuit;
a best survivor circuit for selecting and transmitting as an estimated encoding sequence a.sub.k-D corresponding to a most likely estimate of an actually transmitted data sequence;
in which:
each channel estimator has an inputs the corresponding initial survivor sequence and the observed digital signal y.sub.k and has as an output signal a channel estimate signal corresponding to an estimate of the transmission channel as a predetermined function only of the corresponding initial survivor sequence and the observed digital signal;
each metrics computation circuit has as inputs the corresponding initial survivor sequence, the corresponding channel estimate signal, and the observed digital signal y.sub.k and has as outputs transition metrics computation signals corresponding to the input initial survivor sequence;
the accumulated metrics computation circuit has as inputs the metrics computation signals from all of the metrics computation circuits and has as outputs accumulated metrics signals;
the survivor selection circuit has as inputs the accumulated metrics signals and has as outputs the N candidate survivor signals;
the best survivor selection circuit has as inputs the N candidate survivor signals and has as an output the estimated encoding sequence a.sub.k-D ;
whereby metrics computation is performed independently for each initial survivor sequence using the separate channel estimators for each survivor.

10 more elements

A system for estimating data sequences in digital transmissions, with a transmission channel and a received observed digital signal y.sub.k comprising:

a survivor memory circuit for storing each of a plurality of possible data paths as a sequence of N initial survivor sequences s.sub.1, . . . , s.sub.N, where N is an integer;
a plurality of N individual channel estimators;
a plurality of N individual transition metrics computation circuits, wherein each individual transition metrics computation circuit computes a transition metric from the initial survivor sequence at a time k to each of a plurality of data states at a time k+1;
an accumulated metrics computation circuit for computing and storing accumulated metrics for each initial survivor sequence and each associated transition metric up to time k+1;
a survivor selection circuit for selecting new and updated candidate survivor sequences based on the initial survivor sequences and the accumulated metrics associated to each possible state transition stored in the accumulated metrics computation circuit for each of the plurality of possible data paths;
a best survivor circuit for selecting and outputting a most likely estimate of an actually transmitted data sequence,
wherein each channel estimator receives the corresponding initial survivor sequence and the observed digital signal y, and transmits a channel estimate signal corresponding to an estimate of the transmission channel as a predetermined function only of the corresponding initial survivor sequence and the observed digital signal.

4 more elements

Dependencies are inferred from the claim text.