Telemetry system with authentication

• US 7,224,713 B2
• Filed: 12/20/2000
• Issued: 05/29/2007
• Est. Priority Date: 04/09/1998
• Status: Expired due to Fees

• Current Assignee: Andrzej Partyka
• Original Assignee: Andrzej Partyka
• Inventors: Partyka, Andrzej
• Primary Examiner(s): TRAN, KHANH C
• Application Number:
  US09/741,411
• Publication Number:
  US 20010004375A1
• Time in Patent Office: 2,351 Days
• Field of Search: 375/132, 375/135, 375/136, 375/134, 375/137, 455/67.11, 455/67.13, 455/67.7, 455/76, 455/115.1, 455/115.4, 455/150.1, 455/151.2, 455/500, 455/502, 340/870.01, 340/870.02, 340/870.03, 340/870.18, 340/870.06, 340/870.11, 340/870.13
• 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 independently of any other of said plurality of transmitters, 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

authenticating transmissions based on an expected and actual transmission frequency and time.

2. The method of claim 1 wherein said expected transmission frequency comprises estimate for transmitter reference frequency drift.

3. The method of claim 1 wherein said expected transmission time comprises estimate for transmitter time reference drift.

4. The method of claim 3 wherein each of said plurality of transmitters controls transmission frequency and time between transmissions based on frequency-time pattern that is different for each of said plurality of transmissions.

5. The method of claim 1 wherein, each of said plurality of transmitters is for varying encryption key between transmissions.

6. The method of claim 5 wherein said encryption key is varied based on frequency-time pattern for controlling transmission frequency and time between transmissions.

7. The method of claim 1 wherein each of said plurality of transmitters is for controlling transmission frequency and time between transmissions.

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 authenticating transmissions based on an expected and actual transmission frequency and time.

9. The receiver of claim 8 wherein said expected transmission frequency comprises estimate for transmitter reference frequency drift.

10. The receiver of claim 8 wherein said expected transmission time comprises estimate for transmitter time reference drift.

11. The receiver of claim 8 wherein frequency and time of transmissions is controlled according to a frequency-time pattern that is different for each of said plurality of transmitters.

12. The receiver of claim 8 wherein said receiver is for changing decryption key between transmissions based on a frequency-time pattern for controlling frequency and time of transmissions.

13. The receiver of claim 8 wherein said receiver in operation authenticates transmissions based on verifiable and variable modification of transmission content.

14. The receiver of claim 13 wherein said verifiable modification is based on frequency-time pattern for controlling transmission frequency and time.

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 providing a predetermined frequency-time pattern for controlling transmission frequency and time between transmissions, and

wherein said transmitter is for varying encryption, for said transmissions, based at least in part, on said frequency-time pattern.

16. The transmitter of claim 15 wherein said frequency-time pattern is predetermined based on a transmitter identification.

17. The transmitter of claim 15 wherein said frequency-time pattern is predetermined based on a transmitter identification.

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 providing a predetermined frequency-time pattern for controlling transmission frequency and time between transmissions, and

wherein said transmitter is for modification of at least a portion of known data for transmission using a modifier that is varied based, at least in part, on said frequency-time pattern.

19. The transmitter of claim 18 wherein frequency-time pattern is individually selected for said transmitter from a plurality of predetermined patterns.

20. The transmitter of claim 18 wherein said frequency-time pattern is predetermined based on a transmitter identification.