Telemetry system with authenticaiton

• US 20010004375A1
• Filed: 12/20/2000
• Published: 06/21/2001
• Est. Priority Date: 04/09/1998
• Status: Active Grant

• Current Assignee: Partyka, Andrzej
• Original Assignee: Partyka, Andrzej
• Inventors: Partyka, Andrzej
• Granted Patent: US 7,224,713 B2
• Time in Patent Office: Days
• US Class Current: 375/135
• CPC Class Codes: H04B 1/7156 Arrangements for sequence synchronisation
• CPC Class Codes: H04B 2001/71367 using a transform
• CPC Class Codes: H04B 2001/71566 Tracking
• CPC Class Codes: H04K 1/00 Secret communication
• CPC Class Codes: H04K 3/25 based on characteristics of target signal or of transmission as countermeasure against surveillance H04K3/827, e.g. using direct sequence spread spectrum or fast frequency hopping spread spectrum techniques H04B1/69
• CPC Class Codes: H04K 3/65 using deceptive jamming or spoofing, e.g. transmission of false signals for premature triggering of RCIED, for forced connection or disconnection to/from a network or for generation of dummy target signal
• CPC Class Codes: H04K 3/827 using characteristics of target signal or of transmission as countermeasure against jamming H04K3/25, e.g. using direct sequence spread spectrum or fast frequency hopping spread spectrum techniques H04B1/69
• CPC Class Codes: H04K 3/88 related to allowing or preventing alarm transmission
• CPC Class Codes: H04L 27/30 wherein each code element is represented by a combination of frequencies

Abstract

A telemetry system includes many radio transmitters using frequency hopping carriers to intermittently transmit transmissions indicative of status of sensors associated with the transmitters. The transmitters transmit transmissions independently of a receiver receiving the transmissions and independently of each other. The carrier frequency and the time between transmissions are changed according to a frequency-time hopping sequence that is different for each transmitter. The sequences and the resulting frequency ad time hopping are predictable and can be reproduced in the receiver based on the transmitter ID number. The system also includes one or more receivers containing a plurality of memory registers to hold, simultaneously for each transmitter, digital data indicative of (a) expected time and (b) expected frequency of the next transmission occurrence. The data is updated based on the time and the content of the received transmissions. The receiver authenticates the received transmissions by discriminating transmissions received at a wrong frequency and time. In addition, each transmitter encrypts the transmission using a variable encryption key that is varied with each transmission. The key variations are based on the frequency and time hopping sequence and are different for each transmitter. Alternatively, prior to encryption, each transmitter modifies data for transmission, using a modifier that is varied based on the frequency and time hopping sequence that is different for each transmitter. In addition, for faster acquisition and robust operation, the receiver includes and RSSI circuit based on FFT to detect transmitted carrier power at several different frequencies. The receiver also includes one or more frequency selective circuits that are tuned in response to the outputs from FFT and the status of the time and frequency registers.

Claims

1. A method of authentication in a telemetry system, said method comprising:

transmitting, by each of a plurality of transmitters, transmissions intermittently at time intervals and at a plurality of frequencies independently of any receiver of said transmissions, and

holding, by a receiver, simultaneously for each of said plurality of transmitters, data indicative of an expected frequency and an expected time of at least one future transmission, and

discriminating transmissions based at least in part on at least one of (a) an expected and an actual transmission frequency and (b) an expected and an actual transmission time.

2. The method of

claim 1

wherein said receiver determines authenticity of transmissions based at least in part on said discriminating.

3. The method of

claim 1

wherein each of said plurality of transmitters encrypts data for transmission, and said receiver decrypts received data.

4. The method of

claim 3

wherein each of said plurality of transmitters changes encryption key for each of a plurality of transmissions.

5. The method of

claim 4

wherein, for each transmitter, said encryption key is determined based on at least one of (a) frequency hoping and (b) time hopping of said each transmitter.

6. The method of

claim 3

wherein said transmitter performs modification of at least a portion of said data for transmission with a modifier that is varied for each of a plurality of transmissions.

7. The method of

claim 6

wherein, for each transmitter, said modifier is based on at least one of (a) frequency hoping and (b) time hopping of said each transmitter.

8. A receiver for authenticating telemetry transmissions, said receiver comprising:

logic for holding, simultaneously for each plurality of transmissions, data indicative of an expected time and an expected frequency of at least one future transmission, wherein each said plurality of transmissions is transmitted by a different one of a plurality of transmitters, wherein each of said plurality of transmitters is for transmitting transmissions intermittently at time intervals and at a plurality of frequencies independently of any equipment that is capable of receiving any of said transmissions from any of said plurality of transmitters, and

circuitry for receiving said transmissions;

wherein said receiver is for discriminating transmissions based at least in part on at least one of (a) an expected and an actual transmission frequency and (b) an expected and an actual transmission time.

9. The receiver of

claim 8

wherein said receiver is for determining authenticity of transmissions based at least in part on said discriminating.

10. The receiver of

claim 8

wherein said receiver is for decrypting received data encrypted for transmission by each of said plurality of transmitters.

11. The receiver of

claim 10

wherein said receiver is for using, for each of said plurality of transmitters, a different decryption key for each of a plurality transmissions.

12. The receiver of

claim 11

wherein said receiver is for determining, for each of said plurality of transmitters, a key for decryption based, at least in part, on said data indicative of an expected time and an expected frequency of at least one future transmission.

13. The receiver of

claim 10

wherein said receiver is for verification, for each of said plurality of transmitters, based on at least a portion of a known content of received data modified by a modifier varied for each of said plurality of transmissions.

14. The receiver of

claim 13

wherein said receiver is for determining, for each of said plurality of transmitters, said modifier based on said data indicative of an expected time and an expected frequency of at least one future transmission.

15. A frequency hopping telemetry transmitter comprising:

circuit for transmitting transmissions intermittently, at time intervals and at various frequencies, independently of any receiver of said transmissions, and

logic for holding, in operation, upon each of said transmissions, data indicative of (a) a frequency and (b) time of at least one future transmission, wherein said frequency is predictable based on at least one past transmission frequency;

wherein said transmitter is for encryption of data for transmission using an encryption key that varies for each of a plurality of said transmissions.

16. The transmitter of

claim 15

wherein said encryption key is determined based, at least in part, on said data indicative of at least one of (a) frequency and (b) time of at least one future transmission.

17. The transmitter of

claim 15

wherein said encryption key is varied according to a sequence that is individually selected for said transmitter from a plurality of predetermined sequences.

18. A frequency hopping telemetry transmitter comprising:

circuit for transmitting transmissions intermittently, at time intervals and at various frequencies, independently of any receiver of said transmissions, and

logic for holding, in operation, upon each of said transmissions, data indicative of (a) a frequency and (b) time of at least one future transmission, wherein said frequency is predictable based on at least one past transmission frequency;

wherein said transmitter is for modification of at least a portion of known data for transmission using a modifier that varies for each of a plurality of said transmissions.

19. The transmitter of

claim 18

wherein said modifier is determined based, at least in part, on said data indicative of at least one of (a) frequency and (b) time of at least one future transmission.

20. The transmitter of

claim 18

wherein said modifier is varied according to a sequence that is individually selected for said transmitter from a plurality of predetermined sequences.