Method of adding encryption/encoding element to the modulation/d

Details Method of adding encryption/encoding element to the modulation/d Method of adding encryption/encoding element to the modulation/d

1997-10-17

2000-12-05

Chin, Stephen

Pulse or digital communications

Systems using alternating or pulsating current

Angle modulation

375261, 375298, 332103, H04L 2710

Patent

active

061576794

ABSTRACT:
A method is provided of adding an encryption element to the QAM modulation/demodulation process. This is achieved by first forming a sequence of transmit QAM constellation symbols on the basis of the information signal to be modulated/demodulated, which signal is comprised by a corresponding sequence of transmit information values. Each QAM transmit constellation symbol is based on a fixed transmit constellation in a complex plane and is characterized by a real part and an imaginary part, each part including a sign, the sign consisting of plus or minus. On the basis of a fixed algorithm, during signal modulation, one or more of the transmit constellation symbols are altered by, for example, conjugating the sign value of either the real or imaginary parts thereof to form a disguised or encrypted set of symbols. During demodulation, a corresponding "undo" algorithm is employed by the receiver to undo the conjugation/encoding of altered QAM symbols, thus decrypting the signal to arrive at the original sequence of QAM constellation symbols.

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patent: 5406588 (1995-04-01), Birchler et al.
patent: 5621762 (1997-04-01), Miller et al.
patent: 5790514 (1998-08-01), Marchok et al.
patent: 5835536 (1998-11-01), May et al.
patent: 5838728 (1998-11-01), Alamouti et al.

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