Patent ID: 7986723

Claim:
A delay estimation apparatus, comprising: correlation means which generates a correlation output between a received signal and a supplied template waveform; analog to digital (AD) conversion means which uniformly samples said correlation output generated by said correlation means into discrete samples; and arithmetic operation means which computes a time delay estimate of said received signal based on said discrete samples generated by said AD conversion means, wherein said arithmetic operation means includes a delay estimation procedure which utilizes both autocorrelation information of the transmit signal associated with said received signal and the statistical information of the noise components in said discrete samples generated by said AD conversion means, said arithmetic operation means including a delay estimation procedure which computes a delay estimate of said received signal according to a simplified solution of a maximum likelihood (ML) method, said maximum likelihood (ML) method for finding an estimate such that a probability function summarizing statistics of given observations is maximized, said simplified maximum likelihood solution being given as the following equation τ ^ = t Z T ⁢ W Z ⁢ h ⁡ ( t Z ) 1 Z T ⁢ W Z ⁢ h ⁡ ( t Z ) , where h(t z ) is a vector containing Z consecutive samples selected from said discrete samples generated by said AD conversion means, t z is a vector containing time instants associated with said samples h(t z ), 1 z is a vector containing only one's, and W z is an accompanying matrix of the covariance matrix of said samples h(t z ) excluding the noise spectral density factor related to said received signal, said samples h(t z ) being selected in such a manner that h(t z ) represents a peak portion of said correlation function output from said correlator.