Technique for frequency-hopped spread spectrum communications
First Claim
1. A frequency-band spread spectrum communications system comprising:
- a transmitter capable of operating in either a conventional or unconventional mode, said transmitter when operating in said conventional mode transmitting one of M tones, where M is 2 raised to a power m, conveying log2 M information bits within a corresponding one of q channels and when operating in said unconventional mode randomly selecting one of the M tones and transmitting it in one of r channels within each frequency hop, r being an integer greater than or equal to M, said r channels being selected pseudorandomly to convey log2 M information bits, and q being the number of channels available per hop;
a first finite state machine for causing said transmitter to operate in said conventional mode with a probability of Pc and said unconventional mode with a probability 1-pc, pc being the probability that said machine will produce a logical "0";
a receiver for receiving signals from said transmitter said receiver including a demodulator for providing a first output signal and a bank of radiometers for providing a plurality of second output signals; and
a second finite state machine for controlling said receiver to select either said first output signal or a largest one of said plurality of second output signals, said first and second finite state machines being synchronizable with one another.
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Abstract
A countermeasure to a partial-band follower jammer for frequency hopping spread spectrum communication systems employs an M-ary orthogonal frequency shift keyed (FSK) signaling system having q frequency channels available for hopping. During each signaling interval, the transmitter and receiver operate in either a conventional or unconventional mode. The conventional mode is selected by the transmitter and the receiver with a pseudorandom probability pc. In this mode, the transmitter transmits one of r tones within the corresponding hop (i.e., within one of q channels), and log2 r information bits are conveyed, while the receiver comprises a dehopper followed by noncoherent matched filters. The unconventional mode is selected with probability 1-pc. In this mode, the transmitter randomly chooses one of the r tones and transmits it in one of r channels within each hop, where the r channels are selected pseudorandomly. In the unconventional mode, log2 r information bits are transmitted and the receiver comprises a bank of r radiometers.
33 Citations
8 Claims
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1. A frequency-band spread spectrum communications system comprising:
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a transmitter capable of operating in either a conventional or unconventional mode, said transmitter when operating in said conventional mode transmitting one of M tones, where M is 2 raised to a power m, conveying log2 M information bits within a corresponding one of q channels and when operating in said unconventional mode randomly selecting one of the M tones and transmitting it in one of r channels within each frequency hop, r being an integer greater than or equal to M, said r channels being selected pseudorandomly to convey log2 M information bits, and q being the number of channels available per hop; a first finite state machine for causing said transmitter to operate in said conventional mode with a probability of Pc and said unconventional mode with a probability 1-pc, pc being the probability that said machine will produce a logical "0"; a receiver for receiving signals from said transmitter said receiver including a demodulator for providing a first output signal and a bank of radiometers for providing a plurality of second output signals; and a second finite state machine for controlling said receiver to select either said first output signal or a largest one of said plurality of second output signals, said first and second finite state machines being synchronizable with one another. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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Specification