Patent ID: 7224715
Filing Date: 2007-05-29
Classification: H04B

Abstract:
1. A method for clock and carrier recovery at a receiver of a direct sequence spread spectrum communication system, the clock and carrier recovery being accomplished using a predefined training sequence, each symbol of the predefined training sequence being spread by a predefined spreading sequence, the predefined training sequence being transmitted on a channel by a transmitter, a signal corresponding to the transmitted training sequence being received by the receiver, the method comprising the steps of: a. down-converting the received signal to convert it to a baseband signal; b. sampling the baseband signal at a predefined sampling rate to obtain samples of the baseband signal, wherein the sampled baseband signal comprises a plurality of symbols; c. estimating a symbol boundary using the samples of the baseband signal; d. computing a maximum likelihood estimate of a mean of phase errors using the samples of the baseband signal with the estimated symbol boundary; e. computing a maximum likelihood estimate of a carrier frequency offset using the maximum likelihood estimate of the mean of the phase errors; and f. computing a maximum likelihood estimate of a clock error using the maximum likelihood estimate of the carrier frequency offset.