System for signaling within a cellular telephone system

• US 6,088,586 A
• Filed: 01/24/1996
• Issued: 07/11/2000
• Est. Priority Date: 01/24/1996
• Status: Expired due to Fees

• Current Assignee: DRS ICAS, LLC (Leonardo S.p.A.)
• Original Assignee: Codem Systems, Inc.
• Inventors: Haverty, James D.
• Primary Examiner(s): Tsang, Fan
• Assistant Examiner(s): Ferguson, Keith
• Application Number:
  US08/592,856
• Time in Patent Office: 1,630 Days
• Field of Search: 455/456, 455/457, 455/11.1, 455/422, 455/434, 455/450, 455/509, 455/511, 455/515, 340/988, 340/989, 340/991, 340/992, 340/993, 340/994
• US Class Current: 455/422.1
• CPC Class Codes: H04W 4/90 Services for handling of emergency or hazardous situations, e.g. earthquake and tsunami warning systems [ETWS]
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management
• CPC Class Codes: H04W 76/50 for emergency connections
• CPC Class Codes: H04W 88/02 Terminal devices
• CPC Class Codes: H04W 92/10 between terminal device and access point, i.e. wireless air interface

Abstract

A cellular signaling system and method uses modified RCC signals or spread spectrum signals in an existing cellular telephone system for signaling a situation, such as an emergency or other cellular telephone communication, or for tracking, e.g. shipments or packages. The signaling system includes one or more modified signal transmitting devices, such as beacons, that transmit modified RCC signals that comply with the frequency spectrum requirements of standard RCC signals used in cellular telephone systems, but cannot be recognized by the existing cellular telephone system, or transmit a spread spectrum signal spread across a number of existing cellular channels. The signaling system further includes a modified signal receiver located at one or more cell sites in the existing cellular telephone system. When the existing cellular receiving device at a cell site does not recognize or understand the modified RCC signal, the modified signal receiver will decode the modified RCC signal. The signaling system can then determine the approximate physical geographic location of the source of the modified RCC signal, for example, using a time difference of arrival (TDOA) technique or other similar locating techniques. The signaling system is also capable of taking the appropriate actions, for example, notifying a response unit such as the police or fire department of a situation.

Claims

1. A signaling system using modified cellular telephone signals within an existing cellular telephone frequency spectrum used by an existing cellular telephone system, said signaling system comprising:

at least one modified cellular telephone signal transmitting device, for transmitting at least one modified reverse control channel (RCC) signal across at least one reverse control channel within said existing cellular telephone frequency spectrum, wherein said at least one modified RCC signal is unrecognizable by said existing cellular telephone system; and

at least one modified cellular telephone signal receiver, for receiving and decoding said at least one transmitted modified RCC signal.

2. The signaling system of claim 1, wherein said at least one modified cellular telephone signal transmitting device also transmits at least one spread spectrum signal transmitted across a plurality of channels within said existing cellular telephone frequency spectrum.

3. The signaling system of claim 1, further including a location determination system, responsive to said at least one transmitted cellular telephone signal, for determining at least an approximate physical geographic location of said at least one modified cellular telephone signal transmitting device.

4. The signaling system of claim 1, further including at least one modified RCC signal receiver located at each of at least three cellular telephone signal receiving sites, for independently receiving said at least one transmitted modified cellular telephone signal;

and

a location determination system, responsive to said at least one modified cellular telephone signal receiving device at each of said at least three cellular telephone signal receiving sites, for determining at least an approximate physical geographic location of said at least one modified cellular telephone signal transmitting device using a time difference of arrival of said at least one transmitted modified cellular telephone signal at each of said at least one modified cellular telephone signal receiving device at said at least three cellular telephone signal receiving sites.

5. The signaling system of claim 1, wherein said at least one modified cellular telephone signal receiving device includes a modified Advanced Mobile Phone System (AMPS) receiver.

6. The signaling system of claim 1, wherein said at least one modified cellular telephone signal transmitting device includes an activator.

7. The signaling system of claim 1, wherein said at least one modified cellular telephone signal transmitting device includes a means for intermittently transmitting said at least one modified RCC signal at predetermined time intervals.

8. The signaling system of claim 1, wherein said at least one modified cellular telephone signal transmitting device includes a signal receiver portion, for receiving at least one signal from at least one cellular telephone signal receiving site.

9. The signaling system of claim 1, wherein existing RCC signals in said existing cellular telephone system include an RCC signal burst having a stream of bits, for defining a message, wherein said at least one modified RCC signal includes a modified RCC signal burst having a modified stream of bits with at least one bit inverted from said stream of bits in said RCC signal burst, wherein said modified stream of bits of said modified RCC signal burst is not recognized by said existing cellular telephone system and is recognized by said modified cellular telephone signal receiver.

10. The signaling system of claim 1, wherein existing RCC signals in said existing cellular telephone system include a seizure precursor, for establishing RCC signal synchronization, wherein said at least one modified RCC signal includes a modified RCC signal burst having a modified seizure precursor, wherein said modified seizure precursor of said modified RCC signal burst is not recognized by said existing cellular telephone system and is recognized by said modified cellular telephone signal receiver.

11. The signaling system of claim 1, wherein existing RCC signals in said existing cellular telephone system include a digital color code, wherein said at least one modified RCC signal includes an invalid digital color code unrecognizable by said existing cellular telephone system.

12. The signal system of claim 1, wherein said modified RCC signal includes encoded information pertaining to a situation.

13. A modified existing cellular telephone system, said existing cellular telephone system using an existing cellular telephone frequency spectrum and including at least three cell sites, for determining a location of at least one modified cellular telephone signal transmitting device, said system comprising:

at least one modified cellular telephone signal transmitting device, for transmitting at least one modified RCC signal to said at least three cell sites, wherein said modified RCC signal is modified by manipulating at least one bit in said modified RCC signal such that said modified RCC signal is within said existing cellular telephone frequency spectrum but is unrecognizable by said existing cellular telephone system;

at least three modified cellular telephone signal receivers, each of said at least three modified cellular telephone signal receivers located at a respective one of said at least three cell sites, for receiving and decoding said at least one modified RCC signal; and

at least one location determination system, responsive to each of said at least three modified cellular telephone receivers, for determining at least an approximate physical geographic location of said at least one modified cellular telephone signal transmitting device.

14. The modified existing cellular telephone system of claim 13, wherein existing RCC signals in said existing cellular telephone system include a stream of bits, for defining a message, wherein said modified RCC signal includes a modified stream of bits with at least one bit inverted from said stream of bits in said existing RCC signal, and wherein said modified stream of bits of said modified RCC signal is unrecognizable by existing cellular telephone receivers at each of said at least three cell sites but is recognizable by said at least three modified cellular telephone signal receivers at said at least three cell sites.

15. The modified existing cellular telephone system of claim 13, wherein existing RCC signals in said existing cellular telephone system include a seizure precursor, for establishing RCC signal synchronization, wherein said at least modified RCC signal includes in modified seizure precursor, and wherein said modified seizure precursor of said modified RCC signal is unrecognizable by existing cellular telephone receivers at each of said at least three cell sites but is recognizable by said at least three modified cellular telephone signal receivers at said at least three cell sites.

16. The modified existing cellular telephone system of claim 13, wherein existing RCC signals in said existing cellular telephone system include a digital color code, where said at least one modified RCC signal includes an invalid digital color code, and wherein said invalid digital color code of said modified RCC signal is unrecognizable by existing cellular telephone receivers at each of said at least three cell sites but is recognizable by said at least three modified cellular telephone signal receivers at said at least three cell sites.

17. A signaling method for an existing cellular telephone system using an existing cellular telephone frequency spectrum and including at least one cell site, said method comprising the steps of:

providing at least one modified cellular telephone signal transmitting device and at least one modified cellular telephone signal receiver;

transmitting at least one modified RCC signal with said at least one modified cellular telephone signal transmitting device, wherein said modified RCC signal is within said existing cellular telephone frequency spectrum but is unrecognizable by an existing cellular receiver at said at least one cell site;

receiving at least said at least one modified RCC signal in said at least one cell site;

determining that said modified RCC signal is unrecognizable by said existing cellular receiver at said at least one cell site; and

decoding said at least one modified RCC signal received by said at least one modified cellular telephone signal receiver.

18. The method of claim 17, wherein said step of transmitting said at least one modified RCC signal includes transmitting a modified RCC signal burst having a stream of bits

wherein said stream of bits of said modified RCC signal burst is received by said existing cellular receiver at said at least one cell site and is determined to be invalid by said existing cellular receiver.

19. The signaling method of claim 17, wherein existing RCC signals in said existing cellular telephone system include a stream of bits, for defining a message, and wherein the step of transmitting at least one modified RCC signal includes inverting at least one bit in said stream of bits such that said stream of bits is unrecognizable by said existing cellular receiver at said at least one cell site.

20. The signaling method of claim 17, wherein existing RCC signals in said existing cellular telephone system include a seizure precursor, for establishing RCC signal synchronization, and wherein the step of transmitting at least one modified RCC signal includes the step of modifying said seizure precursor such that said seizure precursor is unrecognizable by said existing cellular receiver at said at least one cell site.

21. The signaling method of claim 17, wherein existing RCC signals in said existing cellular telephone system include a digital color code, and wherein the step of transmitting at least one modified RCC signal includes providing an invalid digital color code such that said invalid digital color code is unrecognizable by said existing cellular receiver at said at least one cell site.

22. The method of claim 17, further including the step of determining at least an approximate geographic location of said at least one modified cellular telephone signal transmitting device.

23. The method of claim 22, wherein said existing cellular telephone system includes at least three cell sites;

wherein said step of providing said at least one modified cellular telephone signal receiver includes providing a modified cellular telephone signal receiver at each of said at least three cell sites; and

wherein said step of determining said at least one approximate geographic location of said at least one modified cellular telephone signal transmitting device includes calculating a time difference of arrival of said at least one modified RCC signal at each of said at least three cell sites.

24. The method of claim 22, further including the step of:

responding to said at least one modified RCC signal after said at least one modified cellular telephone signal receiver decodes said at least one modified RCC signal.

25. The method of claim 22, further including the step of:

providing notification of said at least an approximate geographic location of said at least one modified cellular telephone signal transmitting device.

26. The method of claim 17, further including the step of:

activating said at least one modified cellular telephone signal transmitting device upon indication of a situation.

27. The method of claim 26, wherein said step of transmitting said at least one modified RCC signal with said at least one modified cellular telephone signal transmitting device includes intermittently transmitting said at least one modified RCC signal at predetermined time intervals upon activating said at least one modified cellular telephone signal transmitting device.

28. The method of claim 27, wherein said step of activating said at least one modified cellular telephone signal transmitting device upon indication of a situation includes activating said at least one modified cellular telephone signal transmitting device upon occurrence of an emergency.

29. A modified cellular telephone signal transmitting device for use within an existing cellular telephone frequency spectrum in an existing cellular telephone system that recognizes existing RCC signals having a stream of bits, said transmitting device comprising:

modified RCC signal generating means, for generating a modified RCC signal by modifying at least one bit in said stream of bits of said existing RCC signals such that said modified RCC signal is unrecognizable by said existing cellular telephone system; and

transmitting means, responsive to said modified RCC signal generating means, for transmitting said modified RCC signal within said existing cellular telephone frequency spectrum in said existing cellular telephone system.

30. The modified cellular telephone signal transmitting device of claim 29, wherein said modified RCC signal generating means generates said modified RCC signal by inverting at least one bit in said stream of bits such that said stream of bits is unrecognizable by said existing cellular telephone system.

31. The modified cellular telephone signal transmitting device of claim 29, wherein said modified RCC signal generating means generates said modified RCC signal by modifying a precursor of said existing RCC signals such that said modified seizure precursor is unrecognizable by said existing cellular telephone system.

32. The modified cellular telephone signal transmitting device of claim 29, wherein said modified RCC signal generating means generates said modified RCC signals by providing an invalid digital color code in said modified RCC signal such that said invalid digital color code is unrecognizable by said existing cellular telephone system.

33. The modified cellular telephone signal transmitting device of claim 31, wherein said control signals include modified forward control channel (FCC) signals transmitted by at least one modified FCC signal transmitter.

34. The modified cellular telephone signal transmitting device of claim 29 further including a transmitting device locating means, for locating said modified cellular telephone signal transmitting system.

35. The modified cellular telephone signal transmitting device of claim 29 further including control signal receiving means, for receiving modified control signals which control said modified cellular telephone signal transmitting device.

36. The modified cellular telephone signal transmitting device of claim 35, wherein said control signal receiving means receives at least one page request control signal, and wherein said transmitting means transmits said modified RCC signal in response to each said at least one page request control signal received by said control signal receiving means.

37. The modified cellular telephone signal transmitting device of claim 35, wherein said control signal receiving means receives at least one disable command control signal, and wherein said transmitting means disables transmission of said modified RCC signal in response to said disable command control signal received by said control signal receiving means.