Maximum likelihood sequence estimation apparatus

Claim 1

A maximum likelihood sequence estimation apparatus for determining the identity of a received sequence of digital data, comprising: a received signal hold circuit for holding a received signal and outputting the signal depending on an output instruction; a maximum likelihood sequence estimation circuit for inputting said received signal and determining all possible sequences of data, determining the sequences having a highest probability of generation on the basis of a channel impulse response characteristic estimation value and storing such sequences at surviving paths, deciding as a maximum likelihood sequence the final surviving path at a point where all surviving paths converge to a single path and outputting such data as a final estimated received data sequence; a merge detection control circuit for detecting the convergence or merge of said surviving paths and transmitting an instruction for outputting said final estimated data sequence to said maximum likelihood sequence estimation circuit and an instruction for outputting said received signal to said received signal hold circuit; and a channel impulse response characteristic estimation circuit for estimating a channel impulse response characteristic value based on the outputs of said maximum likelihood sequence estimation circuit and received signal hold circuit and supplying the channel impulse response characteristic estimation value to said maximum likelihood sequence estimation circuit as an updated channel impulse response characteristic value.

Claim 4

A method of estimating a channel impulse response characteristic value of a communication channel over which digital data is received, as a calculation parameter in a maximum likelihood sequence estimation process for estimating a maximum likelihood data sequence, comprising the steps of: holding a received signal and outputting the signal in response to an output instruction; determining the sequences having a highest probability of generation on the basis of a channel impulse response characteristic estimation value and storing such sequences at surviving paths, deciding as a maximum likelihood sequence the final surviving paths at a point where all surviving paths converge to a single path and outputting such data as a final estimated received data sequence; detecting the convergence or merge of said possible sequences and transmitting an instruction for outputting said final estimated data sequence and an instruction for outputting said received signal; and estimating a channel impulse response characteristic value based on the outputted final surviving path and the outputted held received signal and supplying the channel impulse response characteristic estimation value as an updated channel impulse response characteristic value.