EP0247790A2
Expired / Lapsed
EP
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Secure communication system for multiple remote units
Assignee: Fairchild Weston Systems Inc
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Filing: 1987-05-21
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Granted: —
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Expires: 2007-05-21
Abstract
Abstract A frequency-hopping datalink for 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.
Inventors
- 👤 William N. Waggener
- 👤 John P. Keal
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-06 12:59
CPC Classifications
H; H04; H04B; H04B1/00; H04B1/69; H04B1/713; H04B1/7143; H04K; H04K1/00; H04K1/003
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
132 words
In a secure communication system of the frequency-hopping type 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 characterized by 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 the first and second predetermined frequencies is transmitted as part of the information signal and said predetermined frequencies are periodically changed in accordance with a random pattern.
Claim 2
Dependent Claim
132 words
In a secure communication system of the frequency-hopping type 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 characterized by 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 the first and second predetermined frequencies is transmitted as part of the information signal and said predetermined frequencies are periodically changed in accordance with a random pattern.
Claim 3
Dependent Claim
86 words
The method according to claim 1, wherein the base station includes a receiver and the remote unit includes a transmitter and the method is characterized by the steps of: (e) generating a second information signal at the remote unit; (f) transmitting the second information signal at the first predetermined frequency; (g) receiving the second information signal at the relay unit; (h) retransmitting the second information signal by the relay unit at the second predetermined frequency; and (i) receiving the second information signal at the base station.
Claim 4
Dependent Claim
60 words
The method according to claim 1 or 2, characterized in that the information signal includes a portion representative of the first and second frequencies of transmission of the next information signal and in that the relay unit retransmits the information signal at said second frequency which is determined by the frequency representative portion of an immediately preceding transmitted information signal.
Claim 5
Dependent Claim
92 words
The method according to claim 2 or 3, characterized in that said first information signal transmitted by the base station includes a portion representative of the first and second frequencies of transmission of the next first and second information signals, and wherein the relay unit receives said first and second information signals at said first frequency and retransmits both the first and second information signals at said second frequency, said first and second frequencies being determined by the frequency representative portion of an immediately preceding information signal transmitted by the base station.
Claim 6
Dependent Claim
78 words
The method according to claim 4, characterized in that there are a plurality of remote units and wherein said first information signal includes a portion indicative of separate and unique time delays for transmission of information signals generated by each of said remote units and in that in step (h), the second information signal is transmitted by said remote unit at a predetermined time after the relay unit retransmits a first information signal transmitted by the base station.
Claim 7
Dependent Claim
80 words
The method according to claim 3, characterized in that the portion of the information signal representative of the first and second frequencies of transmission is an encrypted version of said first and second frequencies and is a signal for changing the state of a pseudo-random frequency selector including a frequency mapping table containing data indicative of a plurality of predetermined frequencies, said frequency mapping table forming part of the transmitters and receivers of said relay unit and said remote unit.
Claim 8
Dependent Claim
145 words
A secure communication apparatus of the frequency-hopping type characterized by: 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 transmitter and 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 the first and second predetermined frequencies is transmitted by the base station as part of the information signal, said base station further including means for periodically changing said predetermined frequencies in a random pattern and for transmitting information representative thereof to the relay unit and remote unit.
Claim 9
Dependent Claim
145 words
A secure communication apparatus of the frequency-hopping type characterized by: 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 transmitter and 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 the first and second predetermined frequencies is transmitted by the base station as part of the information signal, said base station further including means for periodically changing said predetermined frequencies in a random pattern and for transmitting information representative thereof to the relay unit and remote unit.
Claim 10
Dependent Claim
77 words
The apparatus according to claim 7, characterized by: means for generating a second information signal at the remote unit; means located at the remote unit for transmitting the second information signal at the first predetermined frequency, the second information signal being received by the receiver of the relay unit and retransmitted by the transmitter of the relay unit at the second predetermined frequency; and receiver means located at the base station for receiving the second information signal.
Claim 11
Dependent Claim
66 words
The apparatus according to claim 7 or 8, characterized in that the information signal generated by the base station includes a portion representative of the first and second frequencies of transmission of the next information signal and wherein the relay unit retransmitting means retransmits the information signal at said second frequency which is determined by the frequency representative portion of an immediately preceding transmitted information signal.
Claim 12
Dependent Claim
106 words
The apparatus according to claim 8 or 9, characterized in that the base station generating and transmitting means generates and transmits a first information signal at said first frequency including a portion representative of the first and second frequencies of transmission of the next first and second information signals, and wherein the remote unit receives said first and second information signals at said first frequency and the relay unit retransmitting means retransmits both the first and second information signals at said second frequency, said first and second frequencies being determined by the frequency representative portion of an immediately preceding information signal transmitted by the base station.
Claim 13
Independent Claim
47 words
The apparatus according to claims 8, 9 or 10, characterized in that there are a plurality of remote units and wherein said first information signal includes a portion indicative of separate and unique time delays for transmission of information signals generated by each of said remote units.
Claim 14
Dependent Claim
80 words
The apparatus according to claim 9, 10 or 11, characterized in that the base station includes means for encrypting the portion of the information signal representative of the first and second frequencies of transmission and is a signal for changing the state of a pseudo-random frequency selector including a frequency mapping table containing data indicative of a plurality of predetermined frequencies, said frequency mapping table forming part of the transmitters and receivers of said relay unit and said remote unit.
References Cited (Backward Citations)
No citation records indexed.
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