Orthogonal frequency division multiplexing (OFDM) method and apparatus for protecting and authenticating wirelessly transmitted digital information

• US 20050180315A1
• Filed: 01/13/2005
• Published: 08/18/2005
• Est. Priority Date: 01/13/2004
• Status: Active Grant

• Current Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Original Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Inventors: Shin, Sung-Hyuk, Olesen, Robert Lind, Chitrapu, Prabhakar R., Kaewell, John David Jr., Herschaft, Richard Dan, Hoffmann, John Erich
• Granted Patent: US 7,929,409 B2
• Time in Patent Office: Days
• US Class Current: 370/208
• CPC Class Codes: H04B 7/2628 using code-division multiple access [CDMA] or spread spectrum multiple access [SSMA] H04B7/2618 takes precedence
• CPC Class Codes: H04L 1/0041 Arrangements at the transmitter end
• CPC Class Codes: H04L 1/0061 Error detection codes
• CPC Class Codes: H04L 1/0065 Serial concatenated codes
• CPC Class Codes: H04L 1/0606 Space-frequency coding
• CPC Class Codes: H04L 1/0618 Space-time coding
• CPC Class Codes: H04L 1/08 by repeating transmission, e.g. Verdan system H04L1/1858 and H04L1/189 take precedence
• CPC Class Codes: H04L 1/1812 Hybrid protocols; Hybrid automatic repeat request [HARQ]
• CPC Class Codes: H04W 12/06 Authentication

Abstract

A method and apparatus for protecting and authenticating wirelessly transmitted digital information using numerous techniques. The apparatus may be a wireless orthogonal frequency division multiplexing (OFDM) communication system, a base station, a wireless transmit/receive unit (WTRU), a transmitter, a receiver and/or an integrated circuit (IC). The wireless OFDM communication system includes a transmitter which steganographically embeds digital information in an OFDM communication signal and wirelessly transmits the OFDM communication signal. The system further includes a receiver which receives the OFDM communication signal and extracts the steganographically embedded digital information from the received OFDM communication signal.

Claims

1. In a wireless orthogonal frequency division multiplexing (OFDM) communication system including a transmitter and a receiver, a method of protecting and authenticating wirelessly transmitted digital information, the method comprising:

(a) the transmitter steganographically embedding digital information in an OFDM communication signal;

(b) the transmitter wirelessly transmitting the OFDM communication signal;

(c) the receiver receiving the OFDM communication signal; and

(d) the receiver extracting the steganographically embedded digital information from the received OFDM communication signal.

2. The method of claim 1 wherein the digital information is encoded on a guard period between each OFDM symbol.

3. The method of claim 2 wherein more than one guard period is utilized to encode the digital information.

4. The method of claim 1 wherein the digital information is encoded on pilot sub-carriers.

5. The method of claim 4 wherein the digital information is encoded as manipulating a specified pilot sub-carrier with information which is opposite of what is expected in a receiver.

6. The method of claim 4 wherein the digital information is encoded as alternating pilot sub-carriers in a predetermined pattern.

7. The method of claim 1 wherein the digital information is encoded by puncturing one or more sub-carriers in a predetermined manner.

8. The method of claim 7 wherein the digital information is encoded as puncturing of a specific sub-carrier.

9. The method of claim 7 wherein the digital information is encoded as the distance between punctured sub-carriers.

10. The method of claim 1 wherein the digital information is encoded as varying amplitude level of particular sub-carriers in a predetermined manner.

11. The method of claim 10 wherein amplitude level of consecutive symbols are varied for transferring the digital information.

12. The method of claim 10 wherein amplitude level of even numbered sub-carriers and amplitude level of odd numbered sub-carriers are varied for transferring the digital information.

13. The method of claim 1 wherein the digital information is encoded using a sub-carrier located periphery of OFDM transmission spectrum.

14. The method of claim 13 wherein additional peripheral sub-carrier is added for carrying the digital information.

15. The method of claim 1 wherein the digital information is encoded as modifying a polynomial for a particular scrambling code.

16. The method of claim 1 wherein the digital information is encoded as modifying a polynomial for a cyclic redundancy check (CRC).

17. The method of claim 1 wherein the digital information is encoded utilizing synchronization bits.

18. The method of claim 17 wherein the synchronization bits are scrambled for transferring the digital information.

19. The method of claim 17 wherein the number of synchronization bits are varied for transferring the digital information.

20. The method of claim 17 wherein the synchronization bits are altered in every data packet transmission in a predetermined pattern.

21. The method of claim 1 wherein the digital information is encoded utilizing bits in an OFDM header field.

22. The method of claim 21 wherein unused bits in a service field is utilized.

23. The method of claim 21 wherein unused bits in a signal field is utilized.

24. The method of claim 22 wherein bits in a reserved field are toggled in a predetermined pattern.

25. The method of claim 23 wherein bits in a rate field are utilized.

26. The method of claim 25 wherein an unspecified bit pattern replacing a specified bit pattern is utilized to encode the digital information.

27. The method of claim 25 wherein an OFDM data packet is intentionally mapped incorrectly at a predetermined time or time interval.

28. The method of claim 1 wherein the digital information is encoded utilizing tail bits.

29. The method of claim 28 wherein the tail bits are either header tail bits or convolutional tail bits.

30. The method of claim 1 wherein the digital information is encoded utilizing pad bits.

31. The method of claim 1 wherein the digital information is encoded by delaying a particular OFDM symbol in a predetermined pattern.

32. The method of claim 1 wherein the digital information is encoded by offsetting the OFDM carrier frequency in a predetermined manner.

33. The method of claim 32 wherein more than one step of frequency offset is utilized, whereby more than one digital information is encoded by one frequency offset.

34. The method of claim 1 wherein the digital information is encoded by code puncturing after forward error correction (FEC) coding is completed.

35. The method of claim 34 further comprising:

puncturing a portion of the OFDM at an FEC rate higher than that which will be used to decode the OFDM signal;

embedding watermark information in said portion of the OFDM signal so as to create the equivalent of an OFDM signal encoded at a lower FEC rate; and

transmitting the watermark embedded OFDM signal at said lower FEC rate.

36. The method of claim 1 wherein the digital information is encoded by utilizing more than one pulse shaping in a predetermined manner.

37. The method of claim 1 wherein the digital information is encoded utilizing DC term sub-carrier.

38. The method of claim 1 wherein the digital information is encoded by varying channel switching time, whereby a receiver'"'"'s acknowledgement (ACK) response time is varied in a predetermined pattern.

39. The method of claim 1 wherein the digital information is encoded by changing OFDM symbol constellation pattern.

40. The method of claim 39 wherein a transmit accuracy is altered to produce wobble-shaped constellation pattern.

41. The method of claim 39 wherein the constellation pattern is rotated in a particular degree.

42. The method of claim 1 wherein the digital information is encoded by alternating antenna polarization in a predetermined pattern.

43. The method of claim 1 further comprising a step of denying a service to a user when said user is known to be unauthenticated.

44. The method of claim 43 wherein the authenticity of the user is checked at the earliest stage of communication.

45. The method of claim 43 further comprising steps of disassociating all associated users and wherein authorized users obtain a new session key upon detecting the unauthenticated user.

46. The method of claim 45 wherein each authorized user generates the new session key by at least one of a function of an old session key, a function of the time of day and a function of information transmitted to users informing them to disassociate.

47. The method of claim 1 wherein the digital information is encoded by intentionally corrupting forward error correction coding in a predetermined pattern, whereby a transmission is authenticated when a receiver detects a particular error rate.

48. The method of claim 1 wherein more than one embedded channel is utilized to carry digital information.

49. The method of claim 48 wherein the embedded channel is changed in a predetermined manner.

50. The method of claim 48 wherein the embedded channel is encrypted.

51. The method of claim 1 wherein step (a) further comprises:

(al) the transmitter embedding the digital information in the OFDM communication signal as a watermark in a transmitting (TX) layer 2/3.

52. The method of claim 1 wherein step (a) further comprises:

(a1) the transmitter embedding the digital information in the OFDM communication signal as a watermark in a transmitting (TX) physical layer.

53. The method of claim 1 wherein step (a) further comprises:

(a1) the transmitter embedding the digital information in the OFDM communication signal as a watermark in a transmitting (TX) radio frequency (RF) layer.

54. The method of claim 1 wherein step (d) further comprises:

(d1) the receiver extracting the digital information from the OFDM communication signal using a receiving (RX) layer 2/3 processing device.

55. The method of claim 1 wherein step (d) further comprises:

(d1) the receiver extracting the digital information from the OFDM communication signal using a receiving (RX) physical layer processing device.

56. The method of claim 1 wherein step (d) further comprises:

(d1) the receiver extracting the digital information from the OFDM communication signal using a receiving (RX) radio frequency (RF) processing device.

57. A wireless orthogonal frequency division multiplexing (OFDM) communication system for protecting and authenticating wirelessly transmitted digital information, the system comprising:

(a) a transmitter which steganographically embeds digital information in an OFDM communication signal and wirelessly transmits the OFDM communication signal; and

(b) a receiver which receives the OFDM communication signal and extracts the steganographically embedded digital information from the received OFDM communication signal.

58. A wireless transmit/receive unit (WTRU) for protecting and authenticating wirelessly transmitted digital information, the WTRU comprising:

(a) a transmitter which steganographically embeds digital information in an orthogonal frequency division multiplexing (OFDM) communication signal and wirelessly transmits the OFDM communication signal; and

(b) a receiver which receives an OFDM communication signal and extracts steganographically embedded digital information from the received OFDM communication signal.

59. A base station for protecting and authenticating wirelessly transmitted digital information, the base station comprising:

(a) a transmitter which steganographically embeds digital information in an orthogonal frequency division multiplexing (OFDM) communication signal and wirelessly transmits the OFDM communication signal; and

(b) a receiver which receives an OFDM communication signal and extracts steganographically embedded digital information from the received OFDM communication signal.

60. An integrated circuit (IC) for protecting and authenticating wirelessly transmitted digital information, the IC comprising:

(a) a transmitter which steganographically embeds digital information in an orthogonal frequency division multiplexing (OFDM) communication signal and wirelessly transmits the OFDM communication signal; and

(b) a receiver which receives an OFDM communication signal and extracts steganographically embedded digital information from the received OFDM communication signal.