Secure communication system for multiple remote units
First Claim
1. In a secure communication system of the frequency-hopping type generating successive signals at different frequency "hops" having at least one base station including a transmitter, at least one relay unit including a transmitter and a receiver, and at least one remote unit including a receiver, a method of preventing intentional jamming of the system comprising the steps of:
- (a) generating and transmitting at the base station an information signal at a first predetermined frequency;
(b) receiving the information signal at the relay unit;
(c) retransmitting the information signal by the relay unit at a second predetermined frequency; and
(d) receiving the information signal at the remote unit,wherein information for setting both the first and second predetermined frequencies of the next hop is transmitted as part of the information signal and said predetermined first and second frequencies are periodically changed in accordance with a random pattern.
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Accused Products
Abstract
A frequency-hopping datalink and providing communication between a base station, relay unit and multiple remote units utilizes time-division multiplexing and transmits information signals containing information relevant to the next frequencies of transmission. Signals from the base station are transmitted on a first frequency to a relay unit which retransmits the signals on a second frequency to a group of remote units. The information signal from the base station contains information concerning the frequencies of the next transmission and the time slot allotted for the remote units to respond. The remote units respond back at the first frequency which is received by the relay unit and rebroadcast to the base station at the second frequency. The first and second frequencies are changed after each message in accordance with a pseudo-random sequence generated either at the base station (and transmitted in encrypted form) or by means of a pseudo-random sequence generated at each remote unit and the relay unit, whose initial state is reset by an internal or externally derived time reference and whose pattern is determined by an internal key.
168 Citations
18 Claims
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1. In a secure communication system of the frequency-hopping type generating successive signals at different frequency "hops" having at least one base station including a transmitter, at least one relay unit including a transmitter and a receiver, and at least one remote unit including a receiver, a method of preventing intentional jamming of the system comprising the steps of:
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(a) generating and transmitting at the base station an information signal at a first predetermined frequency; (b) receiving the information signal at the relay unit; (c) retransmitting the information signal by the relay unit at a second predetermined frequency; and (d) receiving the information signal at the remote unit, wherein information for setting both the first and second predetermined frequencies of the next hop is transmitted as part of the information signal and said predetermined first and second frequencies are periodically changed in accordance with a random pattern. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A secure communication system of the frequency-hopping type generating successive signals at different frequency "hops", comprising:
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at least one base station including a transmitter; at least one relay unit including a transmitter and a receiver; and at least one remote unit including a receiver, said base station transmitter including means for generating and transmitting an information signal at a first predetermined frequency; said relay unit transmitter and receiver including means for receiving the information signal and for retransmitting the information signal at a second predetermined frequency and said remote unit receiver including means for receiving the information signal, wherein information for setting both the first and second predetermined frequencies of the next hop is transmitted by the base station as part of the information signal, said base station further including means for periodically changing said predetermined first and second frequencies in a random pattern and for transmitting information representative thereof to the relay unit and remote unit. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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Specification