Pulse or digital communications – Spread spectrum – Direct sequence
Reexamination Certificate
2006-08-08
2006-08-08
Fan, Chieh M. (Department: 2611)
Pulse or digital communications
Spread spectrum
Direct sequence
C375S147000, C375S150000, C375S152000
Reexamination Certificate
active
07088766
ABSTRACT:
A DSSS system determines transmission reliability of a communication channel in real time. A DSSS transmitter (f0=1/T) generates a Pseudo Noise (PN) code and modulates a carrier source [cos. (2Σγc)] with a selected chip rate. The transmitter bandwidth is a direct function of the chip rate. The PN coded carrier signal is further modulated by a data signal [m(t)] to provide an output signal [s(t)] to a correlator via a communication channel for purposes of determining the transmission characteristic of the channel. The correlator running a variable length pseudo noise code combines the code and the carrier which relates the incoming data signal to a correlation value for detecting the data signal. The correlation value is compared to a threshold value based upon experience of reliable transmission of data through the communication channel. The value of the correlation value declines as the data is attenuated in the communication channel, thus, the band limiting effect of the communication can be determined by the change in the correlation value.
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Aust Carrie E.
Cranford, Jr. Hayden C.
Schmatz Martin L.
Cockburn Joscelyn G.
Fan Chieh M.
International Business Machines - Corporation
Morgan & Finnegan
Perilla Jason M.
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