Method for frequency offset estimation in a direct sequence spread spectrum communications receiver
AssigneeNEC Corporation
InventorMajid Boloorian
Life of this patent
Estimating the term…
Abstract
A method of estimating the difference in frequency between base station transmissions received over a radio channel and a locally generated carrier frequency in a mobile receiver. The differential phase shifts imparted to different parts of a received synchronization code because of a frequency offset of the local reference oscillator are detected in the receiver. A series of partial correlations of the received synchronization code over a single transmission slot allows detection of the differential phase shifts. Signal to noise ratios may be improved by means of a series of overlapping partial correlations. The period over which the correlations are performed is much less than the coherence time of the radio channel.
Claims4
A method of estimating the frequency offset in a direct sequence spread spectrum communications receiver comprising computation of differences in phase imparted by down-conversion in the receiver to parts of a synchronization code received over a radio channel, said differences in phase being computed from a series of correlations of parts of the received synchronization code with a synchronization code stored in the receiver, in which the period over which the series of correlations is performed is not greater than the length of said stored synchronization code.
A method as in any preceding claim in which the series of partial correlations is performed on a code of length X chips and comprises a first correlation period of the first X-a chips of the code and a second correlation period of the last X-a chips of the code where a is a number of chips of said code not greater than X/2.
Dependencies are inferred from the claim text.