Pulse or digital communications – Spread spectrum – Direct sequence
Reexamination Certificate
2005-05-24
2009-10-27
Fan, Chieh M (Department: 2611)
Pulse or digital communications
Spread spectrum
Direct sequence
C375S140000, C375S141000, C375S143000, C375S145000, C375S146000, C375S295000, C375S354000, C375S357000, C375S359000, C375S367000
Reexamination Certificate
active
07609751
ABSTRACT:
A first node initiating communications with a second node already in a secure network sends a discovery burst having a preamble portion and a payload portion. The preamble portion is sent at a varying frequency between high and low thresholds that are reflective of Doppler uncertainty between the nodes. The second node continuously listens at a frequency, termed an acquisition frequency. A data sequence in the preamble portion, known to the second node, is received and used to determine the receive instant in the preamble portion, and thereby compare against the known frequency ramp to determine the frequency at which the payload portion will be received. Preferably, the first node varies the preamble portion between thresholds more than once within the time span of a single preamble portion, and the preamble and payload portions are spread with different spreading codes. The preamble portion may also be disguised with noise generated by the first node.
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Ertel Richard B.
Giallorenzi Thomas R.
Griffin Dan M.
Hall Eric K.
Harris Johnny M.
Fan Chieh M
Harrington & Smith PC
L-3 Communications Corporation
Lee Siu M
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