Authentication techniques in a monitoring system

• US 6,844,816 B1
• Filed: 10/05/1999
• Issued: 01/18/2005
• Est. Priority Date: 10/05/1999
• Status: Expired due to Term

• Current Assignee: B.I. Incorporated (Geo Group Incorporated)
• Original Assignee: B.I. Incorporated (Geo Group Incorporated)
• Inventors: Melton, Donald Alfred, Wilbur, Todd James
• Primary Examiner(s): Zimmerman, Brian
• Application Number:
  US09/412,488
• Time in Patent Office: 1,932 Days
• Field of Search: 340/572.1, 340/572.4, 340/573.1, 340/573.3, 340/573.4, 340/5.26, 340/5.27, 340/825.49, 340/539
• US Class Current: 340/572.1
• CPC Class Codes: G07C 9/28 the pass enabling tracking or indicating presence
• CPC Class Codes: G08B 21/22 responsive to presence or absence of persons
• CPC Class Codes: H04L 63/126 the source of the received data
• CPC Class Codes: H04M 11/007 with remote control systems remote control in general G08C

Abstract

An Electronic House Arrest Monitoring (EHAM) system of the present invention includes a transmitter attached to a monitored offender and a receiver positioned in the vicinity of the desired monitoring location. The transmitter and the receiver each have a pattern stored or generated therein for determining the interval of time between signal transmissions and receptions. The pattern is pseudo-random to offer improved protection against imposter transmitters, in other words the time intervals are selected to be unequal and randomly varying but the pattern is repeated or cycled to allow continuing signal transmission by the transmitter. The transmitter transmits signals at varying time intervals according to this pattern, and the receiver authenticates signals it receives as coming from the monitored transmitter based on the expected time intervals from the pattern. The pattern may include any number of time intervals and, in one embodiment, includes more than one subpattern to extend the length of the repeat cycle to increase the difficulty of defeating the monitoring system. As further protection against imposter devices, the receiver may verify the signals based on information unique to the transmitter included in each signal. The receiver may further use the received signals and unique time interval patterns to determine a number of operating states, including New Transmitter ID Received, Transmitter In Range and Locked to Transmitter, Transmitter In Range and Not Locked, Transmitter Out of Range, and Imposter Likely. The monitoring system may also include a remote host computer linked to the receiver or receivers to enable these operating states to be monitored remotely by enforcement personnel.

Claims

1. A monitoring system for monitoring location of a person or thing to be monitored, comprising:

a transmitter, associated with the person or thing to be monitored, for transmitting authentic signals at time intervals that vary according to a pattern and which include information representative of respective current positions where such authentic signals occur in said pattern of various time intervals in order to predict when a subsequent authentic signal from the transmitter is expected; and

a receiver for receiving signals, said receiver being operative to use said current position information in a received authentic signal to identify a subsequent time interval from said pattern of various time intervals in order to predict when a subsequent authentic signal from the transmitter is expected, and, further, to determine whether an actual subsequently received signal is an authentic signal that is actually transmitted by said transmitter based on whether such subsequent signal is received when expected in the pattern of various time intervals.

2. The monitoring system of claim 1, wherein said determination by said receiver is also based upon transmitter identification information included in said signals from said transmitter.

3. The monitoring system of claim 1, wherein durations of the various time intervals in said pattern are pseudo-random.

4. The monitoring system of claim 1, said monitoring system further comprising a remote host computer communicatively linked to said receiver and to at least one presence and absence enforcement facility, and wherein said receiver is operable to determine, and communicate to said remote host computer, a present operating state of said transmitter based on said received authentic signals, said present operating state being one of New Transmitter ID Received, Transmitter In Range and Locked to Transmitter, Transmitter in Range but Not Locked to Transmitter, Transmitter Out of Range, or Imposter Likely.

5. The monitoring system of claim 4, wherein said receiver is operable to remain in at least one of said present operating states for a threshold time period without said receiver receiving a signal determined by said receiver to be an authentic signal transmitted by said transmitter.

6. The monitoring system of claim 4, including at least two of said transmitters communicatively linked to said receiver.

7. The monitoring system of claim 1, wherein said pattern has a predetermined number of time intervals and wherein said transmitter transmits said authentic signals on a continuing basis by repeating said number of time intervals of said pattern.

8. The monitoring system of claim 1, wherein said transmitter and said receiver are operable to generate said pattern.

9. The monitoring system of claim 8, wherein said pattern includes at least two subpatterns in a selectable order and each of said transmitter and said receiver includes at least two subpattern generators to generate said at least two subpatterns.

10. The monitoring system of claim 9, wherein each of said transmitter and said receiver includes at least one selection device for determining said selectable order of said at least two subpatterns in said pattern.

11. The monitoring system as defined in claim 10, wherein said authentic signals transmitted by said transmitter include selection information and said at least one selection device of said receiver and transmitter use said selection information for said determining of said selectable order of said subpatterns in said pattern.

12. A method of authenticating transmission signals from a particular transmitter being used to monitor location of a person or a thing to be monitored, said method comprising:

placing a transmitter, for transmitting signals at time intervals that vary according to a pattern, at the location of the person or thing to be monitored;

providing a receiver for receiving signals;

generating said pattern by operating at least two subpattern generators at said transmitter and at least two subpattern generators at said receiver so that said pattern includes at least two subpatterns in selectable order;

transmitting signals from said transmitter at said time intervals according to said pattern;

operating said receiver to receive signals; and

authenticating with said receiver whether said received signals are said transmitted signals from said transmitter by measuring time intervals between consecutive ones of said received signals and comparing said measured time intervals with said pattern.

13. The method of claim 12, wherein said authenticating includes the steps of:

receiving with said receiver at least two signals from said transmitter;

measuring a time interval between a consecutive pair of said at least two signals;

comparing said measured time interval to said pattern to identify a first location in said pattern;

selecting a next time interval from said pattern relative to said first location;

receiving a next signal after a second time interval; and

comparing said next time interval to said second time interval, wherein said received signals are authenticated as being from said receiver when said next time interval and said second time interval are substantially equal;

wherein said receiving said at least two signals from said transmitter step includes validating said received signals based on transmitter identification information associated with said transmitter and included by said transmitter in each of said transmitted signals.

14. The method of claim 13, wherein said validating further includes comparing a measured time interval between a received signal and a previously received, consecutive signal to a predetermined minimum time interval, said received signal being invalid if said measured time interval is less than said minimum time interval.

15. The method of claim 12, wherein said authenticating includes verifying that each of said received signals include transmitter identification information associated with said transmitter.

16. The method of claim 12, wherein each of said transmitter and said receiver includes at least one selection device for determining said selectable order and further wherein said generating includes operating said at least one selection device to determine said selectable order of said at least two subpatterns in said pattern.

17. A method of authenticating transmissions received by a receiver as having originated from a particular transmitter, comprising:

developing a pattern of sequential time intervals in which each time interval has a different duration;

actuating the transmitter to transmit a plurality of authentic signals in a sequence that has time intervals between successive transmitted authentic signals that match in duration and in sequence with the durations of the time intervals of said pattern;

measuring intervals between successive signals received by the receiver and testing such measured time intervals between successive received signals for compliance with at least one of the time intervals in the pattern;

upon finding a match between a measured time interval between received signals and a time interval in said pattern, predicting, based on said pattern, a time when another authentic transmission is expected to be received; and

upon receiving another signal, determining whether said another signal has actually been received at the time when said another authentic transmission was expected to be received.

18. The method of claim 17, including developing said pattern to be semi-random.

19. The method of claim 17, including determining that said receiver is in range and locked onto transmissions from said transmitter based on said another signal having been received when an authentic transmission had been expected.

20. The method of claim 17, including determining whether some of said time intervals between successive received signals are equal.

21. The method of claim 20, including determining, based on some of said time intervals between successive received signals being equal, that an imposter transmitter is likely within range of said receiver.

22. The method of claim 17, wherein the durations of the time intervals are integer multiples of a base timing increment.

23. The method of claim 22, including continuing to monitor signals received by said receiver for a threshold number of valid transmissions received, where a valid transmission includes occurring on an integer multiple of said base timing increment.

24. The method of claim 23, including determining that said transmitter is out of range of said receiver based on not receiving a valid transmission within a selected period of time.

25. The method of claim 23, including determining that said transmitter is in range of said receiver based on:

(i) reception of said threshold number of valid transmissions; and

(ii) time intervals between said valid transmissions matching time intervals in said pattern.

26. The method of claim 25, including determining whether said time intervals between said valid transmissions are between said minimum duration and said maximum duration.

27. The method of claim 26, including determining that the receiver is in range and locked onto said transmissions of said transmitter based on said time intervals between said valid transmissions being between said minimum duration and said maximum duration.

28. The method of claim 26, including determining that the receiver is in range and not locked onto said transmissions of said transmitter based on said time intervals between said valid transmissions not being between said minimum duration and said maximum duration.

29. The method of claim 22, wherein the durations of the time intervals are in a range between a minimum duration and a maximum duration.

30. A monitoring system for monitoring location of a person or thing to be monitored, comprising:

a transmitter, associated with the person or thing to be monitored, for transmitting signals at time intervals that vary according to a pattern which has a predetermined number of time intervals and includes at least two subpatterns in a selectable order, wherein said transmitter is operable to generate said pattern and includes at least two subpattern generators to generate said at least two subpatterns; and

a receiver for receiving signals, said receiver being operative to determine if received signals are transmitted by said transmitter based on said signals from said transmitter being received at time intervals according to said pattern, wherein said receiver is also operable to generate said pattern and includes at least two subpattern generators to generate said at least two subpatterns.

31. The monitoring system of claim 30, wherein each of said transmitter and said receiver includes at least one selection device for determining said selectable order of said at least two subpatterns in said pattern.

32. The monitoring system of claim 31, wherein said signals transmitted by said transmitter include selection information and said at least one selection device of said receiver and of said transmitter use said selection information for said determining of said selectable order of said subpatterns in said pattern.

33. A method of authenticating transmission signals from a particular transmitter being used to monitor location of a person or a thing to be monitored, said method comprising:

placing a transmitter at the location of the person or thing to be monitored for transmitting authentic signals at time intervals according to a pattern in which individual time intervals are unique;

providing a receiver for receiving signals from said transmitter at said time intervals according to said pattern;

operating said receiver to receive signals transmitted by the transmitter;

measuring a time interval between a pair of received signals;

comparing such measured time interval with the unique time intervals in the pattern to identify where such measured time interval is located within the pattern;

determining when to expect at least one subsequent signal transmission from said transmitter based on where said measured time interval is located in the pattern and on time durations of successive next time intervals to come in the pattern;

receiving a subsequent signal, determining if such subsequent signal is received when expected, and, if received when expected, treating such subsequent signal as an authentic transmission by said transmitter as opposed to a possible unauthentic transmission by an imposter transmitter.

34. The method of claim 33, including:

transmitting said signals from said transmitter with transmitter identification information associated with said transmitter in said signals; and

verify that signals received by the receiver are valid as containing the transmitter identification information before using such signals to determine location in the pattern and to authenticate said subsequent signals as having been transmitted by said transmitter.

35. The method of claim 34, including monitoring elapsed time after receipt of a signal that has been verified as valid based on containing the transmitter identification information, and, if a predetermined maximum time threshold elapses without receipt of another signal that is verified as valid based on containing the transmitter identification information, then logging a transmitter out of range (TOR) message.

36. The method of claim 33, including:

creating each time interval in the pattern as being an integer multiple of a base timing increment; and

before using a time interval between a pair of received signals for determining location of such time interval in the pattern, verifying that such time interval is valid as being an integer multiple of said base timing increment.

37. The method of claim 36, including verifying that multiple successive time intervals between received signals are valid as being integer multiples of said base timing increment before determining location of a time interval in the pattern.

38. The method of claim 37, including logging an indication of transmitter first found (TFF) upon verifying that a minimum threshold number of multiple successive time intervals between received signals are valid as being integer multiples of said base timing increment.

39. The method of claim 38, including designating whether the receiver is locked onto transmissions by the transmitter based on whether at least one of the time intervals of the minimum threshold number has a duration that falls within a range between a pre-set minimum limit and a pre-set maximum limit for time interval duration, and, if so, logging a transmitter in lock (TIL) designation, but, if not, logging a transmitter not locked (TNL) designation.

40. The method of claim 33, including providing the pattern for comparing the measured time interval between received signals independent of actual transmitted signals received.

41. In a monitoring system for monitoring location of a particular person or thing, wherein the monitoring system includes a particular transmitter positioned at the location of the particular person or thing and being capable of transmitting authentic signals that include identification information which identifies said particular transmitter, and wherein the monitoring system includes a receiver capable of receiving authentic signals transmitted by said particular transmitter and of recognizing the identification information in such signals to determine that such authentic signals are valid as having come from said particular transmitter, the improvement comprising:

authentication means for determining if apparently valid signals, which are received by the receiver and contain the information that identifies said particular transmitter, are actually authentic signals transmitted by said authentic transmitter as opposed to imposter signals transmitted by an imposter transmitter that is enabled to transmit imposter signals which include said identification information, the authentication means including;

pattern means for providing a pattern of a plurality of time intervals in which the time intervals have different lengths, and wherein the particular transmitter is programmed to transmit a plurality of authentic signals at time intervals which match the time intervals of said pattern;

actual time interval detection means for determining actual time intervals between sequentially received signals which contain said identification information; and

pattern detection means for comparing an actual time interval detected by the actual time interval detection means with the time intervals in the pattern and, if a matching time interval in the pattern is found, predicting based on said pattern, when a subsequent authentic signal is expected to be received.

42. The improvement of claim 41, wherein the authentication means includes signal identification means associated with the receiver for detecting signals received by the receiver that include said identification information.

43. The improvement of claim 42, wherein the authentication means includes pattern confirmation means for checking whether a subsequent actual signal with said identification information is received when a subsequent authentic signal is expected to be received as predicted by said pattern detection means, and, if so, accepting that such subsequent actual signal is an authentic signal that was transmitted by the particular transmitter, but, if not, then rejecting such subsequent actual signal as a likely imposter.

44. The improvement of claim 42, wherein the authentication means includes the particular transmitter being operative to include position information in an authentic signal transmission that indicates the position of the authentic signal transmission in the pattern.

45. The improvement of claim 44, wherein the authentication means includes means for using the position information in the authentic signal to predict, based on said pattern, when a subsequent authentic signal is expected to be received.

46. The improvement of claim 45, wherein the authentication means includes pattern confirmation means for checking whether a subsequent actual signal with said identification information is received when a subsequent authentic signal is expected to be received as predicted, and, if so, accepting that such subsequent actual signal is an authentic signal that was transmitted by the particular transmitter, but, if not, then rejecting such subsequent actual signal as a likely imposter.