Pulse or digital communications – Spread spectrum – Direct sequence
Reexamination Certificate
2007-05-29
2007-05-29
Tse, Young T. (Department: 2611)
Pulse or digital communications
Spread spectrum
Direct sequence
C375S147000, C375S326000, C375S354000, C375S355000
Reexamination Certificate
active
10627088
ABSTRACT:
The present invention provides a method and system for clock and carrier recovery in a direct sequence spread spectrum communication system. The process involves the receiver receiving a digital signal that has been transmitted by a remote transmitter. The method for joint clock and carrier recovery comprises the following steps. The received signal is down-converted and the signal is then converted to digital form. The signal is de-spread to obtain the phase of the signal constellation. The clock error at the receiver is then estimated from the phase error of the signal constellation by means of an optimal linear estimator. The discrete carrier frequency offset of the received signal is then estimated from the estimated clock error. The optimal linear estimator used here for estimating the clock error is also the maximum likelihood estimator.
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patent: 5361276 (1994-11-01), Subramanian
patent: 6005889 (1999-12-01), Chung et al.
patent: 6621857 (2003-09-01), Belotserkovsky et al.
Kaushik Barman and Vellenki Umapathi Reddy, ‘Maximun Likelihood Clock and Carrier Recovery in a Direct Sequence Spread Spectrum Communication System’, pp. 322-325; 2002 IEEE International Conference on Personal Wireless Communications, held in New Delhi, India, on Dec. 15-17, 2002.
Barman Kaushik
Reddy Vellenki Umapathy
Botjer William L.
Hellosoft Inc.
Tse Young T.
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