Patent ID: 8588346
Filing Date: 2013-11-19
Classification: H04L

Abstract:
1. A Doppler frequency estimation system, comprising: a basis projector, for receiving and projecting channel sampling signals to a set of orthogonal bases to generate channel correlation vectors correspondingly; a polynomial generator, connected to the basis projector, for producing a target polynomial according to the channel correlation vectors, an estimated channel-envelope-to-noise-plus-interference power-ratio and a channel-envelope power; and an extreme value determinator, connected to the polynomial generator, for determining an extreme value of the target polynomial and outputting a frequency corresponding to the extreme value as an estimated Doppler frequency; wherein the extreme value determinator comprises: a local extreme value detector, connected to the polynomial generator, for dividing the Doppler frequency into a plurality of sub-bands and determining an extreme value of the target polynomial from each of the subbands, and then outputting an index of the sub-band corresponding to the extreme value of the target polynomial; and a global extreme value determinator, connected to the local extreme value detector, for obtaining a local minimum and a local minimum frequency respectively from each of the sub-bands, obtaining the extreme value of the target polynomial from each of the sub-bands according to the local minimum frequency, selecting a minimum value among the extreme values as the minimum of the target polynomial, and the frequency corresponding to the minimum value as the estimated Doppler frequency; wherein the local extreme value detector configured to perform the following procedures: (A) read a value of {{dot over (L)} for f m indicates an estimated frequency range, P indicates a number of the sub-bands, and L(f m )indicates the logarithmic likelihood function; (B) determine whether the point is greater than or equal to one and smaller than or equal to a predetermined value, and execute step (C) when the point is greater than or equal to one and smaller than or equal to a predetermined value, otherwise, execute step (F); (C) determine whether {dot over (L)} (D) store an index corresponding to the p-th sub-band; (E) determine whether the local minimum exists in a next sub-band; (F) determine whether {dot over (L)} (G) store an index corresponding to the 0-th sub-band which is the first one among the sub-bands; (H) determine whether {dot over (L)} (I) store an index corresponding to the (P+1)-th sub-band which is the last one among the sub-bands; and (J) output the index of the sub-band with the local minimum.