Active waveform collection for use in transmitter identification

• US 6,035,188 A
• Filed: 06/27/1996
• Issued: 03/07/2000
• Est. Priority Date: 06/27/1996
• Status: Expired due to Fees

• Current Assignee: Cellular Technical Services Co., Inc. (Asensus Surgical, Inc.)
• Original Assignee: Cellular Technical Services Co., Inc. (Asensus Surgical, Inc.)
• Inventors: Green, Evan R., Stanhope, David M., Hoogerwerf, David N., McKernan, Randy
• Primary Examiner(s): Chin, Wellington
• Assistant Examiner(s): Kibreab, Senai
• Application Number:
  US08/670,489
• Time in Patent Office: 1,349 Days
• Field of Search: 455/411, 455/410, 455/408
• US Class Current: 455/411
• CPC Class Codes: H04L 63/08 for authentication of entities cryptographic mechanisms or cryptographic arrangements for entity authentication H04L9/32
• CPC Class Codes: H04W 12/126 Anti-theft arrangements, e.g. protection against subscriber identity module [SIM] cloning
• CPC Class Codes: H04W 12/79 Radio fingerprint
• CPC Class Codes: H04W 24/00 Supervisory, monitoring or testing arrangements
• CPC Class Codes: H04W 74/06 using polling

Abstract

A method and system for actively and rapidly collecting reference waveforms from a large number of cellular telephones is provided. The reference waveforms are used to generate fingerprints which are used to distinguish between authorized cellular telephones and unauthorized cellular telephones. Initially, the system selects a cellular telephone whose reference waveform is desired. The selected cellular telephone is then sent a polling message such as a page or registration request. The cellular telephone receives the polling message and transmits a radio frequency (RF) signal containing a reference waveform that contains certain transmission characteristics unique to the selected cellular telephone. From the received RF signal, the reference waveform is extracted and stored. Preferably, the selected cellular telephone is polled repeatedly in order to receive a sufficiently large number of reference waveforms to be able to generate an accurate fingerprint. One method of polling the cellular telephone is by calling the selected cellular telephone through a cellular telephone system. Another method of polling the cellular telephone is by transmitting a control message such as a page, registration, audit or maintenance message.

Claims

1. A method of collecting a reference waveform of a wireless telephone comprising the steps of:

(a) polling a selected one of a plurality of wireless telephones to automatically stimulate a transmission response signal containing a reference waveform indicative of a transmission characteristic of the selected wireless telephone;

(b) receiving from the selected wireless telephone the transmission response signal responsive to the poll;

(c) extracting the reference waveform from the received transmission response signal; and

(d) storing the extracted reference waveform.

2. The method according to claim 1 wherein steps (a) to (d) are repeated until at least two reference waveforms are stored.

3. The method according to claim 2, further comprising the steps of:

generating a fingerprint from the stored reference waveforms; and

optimizing the fingerprint.

4. The method according to claim 3 wherein the step of optimizing the fingerprint comprises the steps of:

aligning each stored reference waveform with respect to the other stored reference waveforms; and

normalizing each stored reference waveform with respect to the other stored reference waveforms.

5. The method according to claim 1, further comprising the step of generating a fingerprint from the stored reference waveform.

6. The method according to claim 1 wherein step (a) comprises transmitting to the selected wireless telephone one of a page, registration, audit and maintenance message.

7. The method according to claim 1 wherein step (a) comprises transmitting a page message to the selected wireless telephone, and further including, after step (c), the step of transmitting a hang-up message to the wireless telephone to prevent the wireless telephone from ringing.

8. The method according to claim 1 wherein step (a) comprises the step of using a wireless transmitter to call the selected wireless telephone.

9. The method according to claim 1 wherein step (a) comprises the step of sending to a wireless telephone switching system a command to poll the selected wireless telephone.

10. The method according to claim 1 wherein step (a) comprises the step of sending to a cell controller located within a cell site a command to poll the selected wireless telephone.

14. The method according to claim 1 wherein step (c) comprises demodulating a portion of the transmission response signal which indicates the transmission characteristic of the wireless telephone and wherein step (d) comprises storing the demodulated transmission response signal.

15. The method according to claim 14 wherein step (c) comprises demodulating a leading or trailing portion of the transmission response signal which indicates the transmission characteristic of the wireless telephone.

11. A method of collecting a reference waveform of a wireless telephone comprising the steps of:

polling the wireless telephone to automatically stimulate a transmission response signal containing a reference waveform indicative of a transmission characteristic of the wireless telephone;

receiving from the wireless telephone the transmission response signal responsive to the poll;

extracting the reference waveform from the received transmission response signal;

storing the extracted reference waveform;

validating the reference waveform when only one transmission response signal is received; and

discarding the reference waveform when more than one transmission response signals responsive to the poll are received.

12. A method of collecting a reference waveform of a wireless telephone comprising the steps of:

polling the wireless telephone to automatically stimulate a transmission response signal containing a reference waveform indicative of a transmission characteristic of the wireless telephone;

receiving from the wireless telephone the transmission response signal responsive to the poll;

extracting the reference waveform from the received transmission response signal;

p1 storing the extracted reference waveform;

selecting a wireless telephone among a plurality of wireless telephones currently transmitting on a call; and

waiting until the selected wireless telephone hangs up before polling the selected wireless telephone to automatically stimulate a transmission response signal therefrom.

13. The method according to claim 12, further including the steps of:

comparing the dialed digits used for the call made by the selected wireless telephone against a list of frequently called valid numbers of an authorized user of the selected wireless telephone; and

verifying that the selected wireless telephone belongs to the authorized user by determining the dialed digits are in the list of frequently called valid numbers.

16. A method of collecting a plurality of reference waveforms of an authorized wireless telephone to be later used in distinguishing telephone calls made by the authorized wireless telephone from telephone calls made by an unauthorized wireless telephone, the method comprising the steps of:

selecting the authorized wireless telephone among a plurality of wireless telephones currently transmitting on a call; and

repeating the following steps n times where n is greater than 1;

polling the selected wireless telephone to automatically stimulate a transmission response signal therefrom;

receiving from the selected wireless telephone the transmission response signal responsive to the poll;

extracting a reference waveform contained in the transmission response signal, the reference waveform indicating a transmission characteristic of the wireless telephone; and

storing the reference waveform.

17. The method according to claim 16, further comprising the step of generating a fingerprint from the stored reference waveforms.

18. The method according to claim 16 wherein the step of polling comprises transmitting to the selected wireless telephone one of a page, registration, audit and maintenance message.

19. A method of collecting a reference waveform of an authorized wireless telephone to be later used in distinguishing telephone calls made by the authorized wireless telephone from telephone calls made by an unauthorized wireless telephone, the method comprising the steps of:

(a) transmitting data to the authorized wireless telephone to elicit a transmission response signal from the authorized wireless telephone, the transmission response signal containing a reference waveform indicative of a transmission characteristic of the authorized wireless telephone;

(b) receiving from the authorized wireless telephone the transmission response signal responsive to the elicitation;

(c) extracting the reference waveform from the received transmission response signal; and

(d) storing the extracted reference waveform.

20. The method according to claim 19 wherein step (a) comprises transmitting to the authorized wireless telephone one of a page, registration, audit and maintenance message.

21. The method according to claim 19 wherein step (a) comprises transmitting a page message to the authorized wireless telephone, and further including, after step (c), the step of transmitting a hang-up message to the authorized wireless telephone to prevent the authorized wireless telephone from ringing.

22. The method according to claim 19 wherein step (a) comprises the step of using a wireless transmitter to place a telephone call to the authorized wireless telephone.

23. The method according to claim 19 wherein step (c) comprises demodulating a portion of the transmission response signal which indicates the transmission characteristic of the authorized wireless telephone and wherein step (d) comprises storing the demodulated transmission response signal.

24. The method according to claim 23 wherein step (c) comprises demodulating a leading or trailing portion of the transmission response signal which indicates the transmission characteristic of the authorized wireless telephone.

25. The method according to claim 19 wherein steps (a) to (d) are repeated until at least two reference waveforms are stored.

26. The method according to claim 19, further comprising the step of generating a fingerprint from the stored reference waveform.

27. A method of using an existing wireless telephone system to collect a reference waveform of an authorized wireless telephone to be later used in distinguishing telephone calls made by the authorized wireless telephone and telephone calls made by an unauthorized wireless telephone over the existing wireless telephone system, the method comprising the steps of:

(a) causing the existing wireless telephone system to transmit data to the authorized wireless telephone to elicit an automatic transmission response signal from the authorized wireless telephone, the transmission response signal containing a reference waveform indicative of a transmission characteristic of the authorized wireless telephone;

(b) receiving from the authorized wireless telephone the transmission response signal responsive to the elicitation through the existing wireless telephone system;

(c) extracting the reference waveform from the received transmission response signal; and

(d) storing the extracted reference waveform.

28. The method according to claim 27 wherein step (a) comprises transmitting to the authorized wireless telephone one of a page, registration, audit and maintenance message through a control channel editor.

29. The method according to claim 27 wherein step (a) comprises causing a cell controller of an existing cell site to transmit a page message to the authorized wireless telephone, and further including, after step (d), the step of causing the cell controller of the existing cell site to transmit a hang-up message to the authorized wireless telephone to prevent the authorized wireless telephone from ringing.

30. The method according to claim 27 wherein step (a) comprises the step of calling the authorized wireless telephone through a wireless telephone switching system in the existing wireless telephone system.

31. The method according to claim 27 wherein step (a) comprises the step of sending a command through a wireless telephone switching system in the existing wireless telephone system to elicit the transmission response signal from the authorized wireless telephone.

32. The method according to claim 27 wherein step (a) comprises the step of sending a command through a cell controller located within a cell site to elicit the transmission response signal from the authorized wireless telephone.

33. A system for collecting a reference waveform of an authorized wireless telephone to be later used in distinguishing telephone calls made by the authorized wireless telephone from telephone calls made by an unauthorized wireless telephone, the system comprising the steps of:

a radio frequency (RF) transmitter operable to transmit an RF signal containing a polling message only to the authorized wireless telephone;

a radio frequency (RF) receiver operable to receive from the authorized wireless telephone an automatic transmission response signal responsive to the polling message, the transmission response signal containing a reference waveform indicative of a transmission characteristic of the authorized wireless telephone;

a processor connected to the RF transmitter and receiver, the processor being operable to cause the RF transmitter to transmit the polling message to the authorized wireless telephone and to extract a reference waveform from the transmission response signal received by the RF receiver; and

a memory connected to the processor for storing the extracted reference waveform.

34. The system according to claim 33, further comprising:

a control channel editor connected to the RF transmitter and operable to insert the polling message into the RF signal generated by the RF transmitter.

35. The system according to claim 33, further comprising:

a demodulator connected between the RF receiver and the processor and operable to demodulate the received transmission response signal.

36. The system according to claim 33 wherein the polling message is one of a page, registration, audit and maintenance message.

37. The system according to claim 33, further comprising:

a line interface circuit connected to the processor and operable to dial the identification number of the authorized wireless telephone, thereby causing the RF transmitter to transmit the polling message to the authorized wireless telephone.

38. The system according to claim 37 wherein the line interface circuit dials the identification number of the authorized wireless telephone over a trunk line connected to a wireless telephone switching system.

39. The system according to claim 37 wherein the line interface circuit dials the identification number of the authorized wireless telephone through a telephone connected to a public switch network.

40. The system according to claim 37 wherein the line interface circuit dials the identification number of the authorized wireless telephone through another wireless telephone.

41. The system according to claim 33, further comprising:

an input-output (I/O) interface circuit connected to the processor and operable to send a command to cause the RF transmitter to transmit the polling message to the authorized wireless telephone.

42. The system according to claim 41 wherein the I/O interface circuit sends the command over an input-output line connected to a wireless telephone switching system.

43. The system according to claim 41 wherein the I/O interface circuit sends the command over an input-output line connected to a cell controller of a cell site.