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

• US 7,929,409 B2
• Filed: 01/13/2005
• Issued: 04/19/2011
• Est. Priority Date: 01/13/2004
• Status: Expired due to Fees

• Current Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Original Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Inventors: Kaewell, John David Jr., Herschaft, Richard Dan, Hoffmann, John Erich, Shin, Sung-Hyuk, Olesen, Robert Lind, Chitrapu, Prabhakar R.
• Primary Examiner(s): Ngo; Ricky
• Assistant Examiner(s): OVEISSI, MANSOUR
• Application Number:
  US11/035,174
• Publication Number:
  US 20050180315A1
• Time in Patent Office: 2,287 Days
• Field of Search: 370/204, 370/321, 370/208, 370/247, 370/250, 370205-206, 382/100, 455/466, 455/456, 455/247, 455/522, 455/574, 713/171, 713/172, 713/173, 713/174, 713/193, 375/260, 375/140, 375/147
• 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. A method for wireless orthogonal frequency division multiplexing (OFDM) communications, the method comprising:

receiving an electromagnetic OFDM communication signal, wherein the OFDM communication signal is an electromagnetic signal or an electronic signal including embedded digital information, wherein the digital information is encoded by performing a first code puncturing of one or more sub-carriers of the OFDM communication signal at a first forward error correction (FEC) rate and performing a second code puncturing of the one or more sub-carriers of the OFDM communication signal at a second FEC rate, wherein the second FEC rate is higher than the first FEC rate, and wherein the digital information includes watermark information that is steganographically embedded in a portion of the digital information that is discarded when performing the second code puncturing such that the digital information appears to be encoded at the first FEC rate;

extracting the steganographically embedded digital information from the received electromagnetic OFDM communication signal; and

comparing the digital information extracted with a stored information.

2. The method of claim 1 wherein the digital information is encoded on a guard period between each OFDM communication 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 as puncturing of a specific sub-carrier.

8. The method of claim 1 wherein the digital information is encoded as the distance between punctured sub-carriers.

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

10. The method of claim 9 wherein amplitude level of consecutive symbols are varied for transferring the digital information.

11. The method of claim 9 wherein amplitude level of even numbered sub-carriers and amplitude level of odd numbered sub-carriers are varied for transferring the digital information.

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

13. The method of claim 12 wherein additional peripheral sub-carrier is added for carrying the digital information.

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

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

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

17. The method of claim 16 wherein the synchronization bits are scrambled for transferring the digital information.

18. The method of claim 16 wherein the number of synchronization bits are varied for transferring the digital information.

19. The method of claim 16 wherein the synchronization bits are altered in every data packet transmission in a predetermined pattern.

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

21. The method of claim 20 wherein unused bits in a service field is utilized.

22. The method of claim 20 wherein unused bits in an OFDM communication signal field are utilized.

23. The method of claim 22 wherein bits in a rate field are utilized.

24. The method of claim 23 wherein an unspecified bit pattern replacing a specified bit pattern is utilized to encode the digital information.

25. The method of claim 23 wherein an OFDM data packet is intentionally mapped incorrectly at a predetermined time or time interval.

26. The method of claim 21 wherein bits in a reserved field are toggled in a predetermined pattern.

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

28. The method of claim 27 wherein the tail bits are either header tail bits or convolutional tail bits.

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

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

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

32. The method of claim 31 wherein more than one step of frequency offset is utilized, whereby more than one digital information is encoded by one frequency offset.

33. The method of claim 1 wherein the digital information is encoded by code puncturing after FEC coding is completed.

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

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

36. 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.

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

38. The method of claim 37 wherein a transmit accuracy is altered to produce wobble-shaped constellation pattern.

39. The method of claim 37 wherein the constellation pattern is rotated in a particular degree.

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

41. The method of claim 1, further comprising:

denying a service to a user on a condition that said user is known to be unauthenticated.

42. The method of claim 41 wherein the authenticity of the user is checked at the earliest stage of communication.

43. The method of claim 41, further comprising:

disassociating all associated users and wherein authorized users obtain a new session key upon detecting the unauthenticated user.

44. The method of claim 43 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.

45. 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 on a condition that the receiver detects a particular error rate.

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

47. The method of claim 46 wherein the embedded channel is changed in a predetermined manner.

48. The method of claim 46 wherein the embedded channel is encrypted.

49. The method of claim 1 wherein the digital information is embedded steganographically in the OFDM communication signal by:

a transmitter as a watermark in a transmitting (TX) layer 2/3.

50. The method of claim 1 wherein the digital information is embedded steganographically in the OFDM communication signal by:

a transmitter as a watermark in a transmitting (TX) physical layer.

51. The method of claim 1 wherein the digital information is embedded steganographically in the OFDM communication signal by:

a transmitter as a watermark in a transmitting (TX) radio frequency (RF) layer.

52. The method of claim 1 wherein extracting the steganographically embedded digital information from the received OFDM communication signal further comprises:

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

53. The method of claim 1 wherein extracting the steganographically embedded digital information from the received OFDM communication signal further comprises:

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

54. The method of claim 1 wherein extracting the steganographically embedded digital information from the received OFDM communication signal further comprises:

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

55. A method for wireless orthogonal frequency division multiplexing (OFDM) communications, the method comprising:

receiving an OFDM communication signal, wherein the OFDM communication signal is an electromagnetic signal or an electronic signal including embedded physical channels within the OFDM communication signal and embedded digital information wherein the digital information is encoded by performing a first code puncturing of one or more sub-carriers of the OFDM communication signal at a first forward error correction (FEC) rate and performing a second code puncturing of the one or more sub-carriers of the OFDM communication signal at a second FEC rate, wherein the second FEC rate is higher than the first FEC rate, and wherein the digital information includes watermark information that is steganographically embedded in a portion of the digital information that is discarded when performing the second code puncturing such that the digital information appears to be encoded at the first FEC rate;

extracting the steganographically embedded digital information from the received OFDM communication signal; and

comparing the digital information extracted with a stored information.

56. The method of claim 55 wherein the OFDM communication signal is maintained on a condition that there is no data to transmit.

57. The method of claim 56 wherein the embedded physical channels continue to transmit steganographically embedded digital information on a condition that the OFDM communication signal has no data to transmit.

58. The method of claim 56 wherein the OFDM communication signal is a cover signal for the embedded physical channels.

59. A wireless transmit/receive unit (WTRU) comprising:

a processor configured to create an electromagnetic orthogonal frequency division multiplexing (OFDM) communication signal, wherein the OFDM communication signal is an electromagnetic signal or an electronic signal including embedded digital information, wherein the digital information is encoded by performing a first code puncturing of one or more sub-carriers of the OFDM communication signal at a first forward error correction (FEC) rate and performing a second code puncturing of the one or more sub-carriers of the OFDM communication signal at a second FEC rate, wherein the second FEC rate is higher than the first FEC rate, and wherein the digital information includes watermark information that is steganographically embedded in a portion of the digital information that is discarded when performing the second code puncturing such that the digital information appears to be encoded at the first FEC rate;

a receiver configured to extract the steganographically embedded digital information from the received electromagnetic OFDM communication signal; and

a comparator configured to compare the digital information extracted with stored information at the receiver.