Patent No. 6,931,084
`Petition For Inter Partes Review
`
`
`
`UNITED STATES PATENT AND TRADEMARK OFFICE
`
`__________________
`
`BEFORE THE PATENT TRIAL AND APPEAL BOARD
`
`___________________
`
`SIRIUS XM RADIO INC.,
`Petitioner,
`
`v.
`
`FRAUNHOFER-GESELLSCHAFT ZUR
`FÖRDERUNG DER ANGEWANDTEN
`FORSCHUNG E.V.,
`Patent Owner.
`
`____________________
`
`Case IPR2018-________
`Patent No. 6,931,084
`
`__________________________________________________________
`
`PETITION FOR INTER PARTES
`REVIEW OF U.S. PATENT NO. 6,931,084
`
`
`
`Mail Stop Patent Board
`Patent Trial and Appeal Board
`United States Patent and Trademark Office
`P.O. Box 1450
`Alexandria, VA 22313-1450
`
`
`
`Petition For Inter Partes Review
`
`
`
`UNITED STATES PATENT AND TRADEMARK OFFICE
`
`__________________
`
`BEFORE THE PATENT TRIAL AND APPEAL BOARD
`
`___________________
`
`SIRIUS XM RADIO INC.,
`Petitioner,
`
`v.
`
`FRAUNHOFER-GESELLSCHAFT ZUR
`FÖRDERUNG DER ANGEWANDTEN
`FORSCHUNG E.V.,
`Patent Owner.
`
`____________________
`
`Case IPR2018-________
`Patent No. 6,931,084
`
`__________________________________________________________
`
`PETITION FOR INTER PARTES
`REVIEW OF U.S. PATENT NO. 6,931,084
`
`
`
`Mail Stop Patent Board
`Patent Trial and Appeal Board
`United States Patent and Trademark Office
`P.O. Box 1450
`Alexandria, VA 22313-1450
`
`
`
`
`Petition for Inter Partes Review
`U.S. Patent No. 6,931,084
`
`TABLE OF CONTENTS
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`Page
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`
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`I.
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`Introduction ...................................................................................................... 1
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`II. Mandatory Notices........................................................................................... 6
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`
`
` A.
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` B.
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` C.
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` D.
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`Real Party in Interest ............................................................................. 6
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`Related Matters ...................................................................................... 6
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`Lead and Backup Counsel ..................................................................... 7
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`Service Information ............................................................................... 7
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`III. Payment of Fees (37 C.F.R. § 42.103) ............................................................ 8
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`IV. REQUIREMENTS FOR INTER PARTES REVIEW UNDER 37
`C.F.R. §§ 42.104 .............................................................................................. 8
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`
`
` Grounds for Standing (37 C.F.R. § 42.104(A)) .................................... 8 A.
`
`
`
` B.
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`
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` C.
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`Identification of Challenged Claims (37 C.F.R. § 42.104(B)(1)) ......... 8
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`Claims and Statutory Grounds Under §§ 42.22 and
`42.104(B)(2) (37 C.F.R. § 42.104(B)(2)) .............................................. 8
`
`
`
` D.
`
`Claim Construction (37 C.F.R. § 42.104(B)(3)) ................................... 9
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`V.
`
`SUMMARY OF THE ‘1084 PATENT AND ITS TECHNICAL
`FIELD .............................................................................................................. 9
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`
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` Overview of the Technical Field ......................................................... 10 A.
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`1.
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`Transmissions Using Frequencies, Carriers, Signals And
`Symbols ..................................................................................... 10
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`U.S. Patent No. 6,931,084
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`2.
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`3.
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`4.
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`Phase Modulation ...................................................................... 11
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`Phase Modulation in Satellite and Multi Carrier
`Modulation Transmissions ........................................................ 14
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`Correcting for Multi-Path or Echo Effects ............................... 18
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`
`
` Overview of the ‘1084 Patent .............................................................. 22 B.
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`
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` Overview of the Prosecution History .................................................. 24 C.
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`
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` D.
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`
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` E.
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`The Challenged Claims ....................................................................... 27
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`Person Having Ordinary Skill in the Art ............................................. 27
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`VI. Overview of the Prior Art .............................................................................. 28
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`
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` Overview of the Tsujishita Reference (Ex. 1006) ............................... 28 A.
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`
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` Overview of the Moose 1990 Reference (Ex. 1007) .......................... 29 B.
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`
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` Overview of Koslov (Ex. 1009) .......................................................... 29 C.
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`VII. Detailed Explanation of the Grounds for Unpatentability............................. 30
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`
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` Overview of Unpatentability of Claims 1-3 of the ‘1084 Patent ........ 30 A.
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` Ground 1: Tsujishita In View of Moose 1990 Renders Obvious B.
`Claims 1–3 of the ‘1084 Patent Under 35 U.S.C. § 103 ..................... 31
`
`
` Ground 2: Tsujishita In View of Moose 1990 and Koslov C.
`Renders Obvious Claims 1–3 of the ‘1084 Patent Under
`35 U.S.C. § 103 ................................................................................... 45
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`VIII. CONCLUSION .............................................................................................. 58
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`CERTIFICATE OF COMPLIANCE WITH 37 C.F.R. § 42.24........................ 59
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`Petition for Inter Partes Review
`U.S. Patent No. 6,931,084
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`TABLE OF AUTHORITIES
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` Page(s)
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`Cases
`In re Am. Acad. of Sci. Tech Ctr.,
`367 F.3d 1359 (Fed. Cir. 2004) ............................................................................ 9
`
`Forschung e.V. v. Sirius XM Radio Inc.,
`1:17-cv-00184 (D. Del. Feb. 22, 2017) ........................................................ 6, 7, 9
`
`Statutes
`35 U.S.C. § 103 .................................................................................................passim
`
`35 U.S.C. §§ 311–319 ................................................................................................ 1
`
`Other Authorities
`
`37 C.F.R. § 42 ............................................................................................................ 1
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`37 C.F.R. § 42.15(a) ................................................................................................... 7
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`37 C.F.R. § 42.103 ..................................................................................................... 7
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`37 C.F.R. §§ 42.104 ............................................................................................... 8, 9
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`MPEP § 2111 ............................................................................................................. 9
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`Petition for Inter Partes Review
`U.S. Patent No. 6,931,084
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`Sirius XM Radio Inc. petitions for inter partes review under 35 U.S.C. §§
`
`311–319 and 37 C.F.R. § 42 of Claims 1–3 of Eberlein et al., U.S. Patent No.
`
`6,931,084 (the “’1084 Patent”). Ex. 1001. The ‘1084 Patent issued on August 16,
`
`2005, to Fraunhofer-Gesellschft zur Förderung der angewandten Forschung e.V.
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`(“Fraunhofer” or “Patent Owner”). Id. Petitioner asserts that there is a reasonable
`
`likelihood that at least one claim is unpatentable and respectfully requests review
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`of, and judgment against, Claims 1–3 of the ‘1084 Patent (the “Challenged
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`Claims”) as unpatentable under 35 U.S.C. § 103.
`
`I.
`
`INTRODUCTION
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`As described in more detail below, the Challenged Claims describe a
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`technique for modifying and/or correcting signals in a mobile receiver that may
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`have been corrupted during the transmission and reception process. When data is
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`broadcast in a multi-carrier modulated (“MCM”) broadcast system, the data can
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`become corrupted during the process for a number of reasons. Ex. 1002 (Lyon)
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`¶¶ 116; 66-70 (citing Ex. 1013 (Proakis) at pp. 258-269, pp. 272-273 and pp. 702-
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`713). For example, as illustrated below, when there are multiple pathways (“multi-
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`path”) for signals to arrive at a receiver, the receiver observes multiple copies of
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`the same signal. Id.
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`Petition for Inter Partes Review
`U.S. Patent No. 6,931,084
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`The ‘1084 Patent refers to these copies of the signal as “echoes.” Ex. 1002
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`(Lyon) at ¶ 94 (citing Ex. 1001 (‘1084 Patent) at 1:13-17, 5:60-67, and 6:1-8).
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`Because the transmission path and corresponding distances that each echo travels
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`are different (e.g., due to bouncing off of obstacles and/or reflectors), the received
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`signals are not in sync, may be out of phase with each other, and may not have the
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`same signal strength. Id. at ¶¶ 117, 66-70 (citing Ex. 1013 (Proakis) at pp. 258-
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`269, pp. 272-273 and pp. 702-713).
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`Because the issues caused by multi-path signals and echoes were known at
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`the time of alleged invention, as explained in the accompanying Expert Declaration
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`of David Lyon, Ph.D, communication engineers employed a variety of techniques
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`to correct these issues. Id. at ¶ 118. In particular, a person of ordinary skill in the
`
`art at the time of the invention (“POSA”) would have known that echo phase offset
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`correction techniques were implemented in MCM systems using differential phase
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`decoding based on the difference between subcarriers in the time domain –– a
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`more conventional system compared to MCM systems using phase difference
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`between subcarriers in the frequency domain. Ex. 1002 (Lyon) ¶¶ 118-124; see
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`also ¶¶ 125-156.
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`The claims of the ‘1084 Patent purportedly implement echo phase offset
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`correction techniques in MCM systems based on the frequency domain approach
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`rather than the conventional time domain technique. Id. at ¶ 119. The application
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`of echo phase offset techniques to MCM system based on the frequency domain
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`apporach, however, was not new. Id. at ¶¶ 119-155. In fact, the ‘1084 Patent file
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`history confirms that the echo phase offset correction technique in MCM systems
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`was known prior to the April 14, 1998, effective filing date of the ‘1084 Patent.
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`Ex. 1003 (8/6/2004 OA) at 2-5; Ex. 1002 (Lyon) at ¶¶ 103-108. During
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`prosecution of App. Ser. No. 09/673,266 (the “’266 Application), the examiner
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`rejected method claims 19-21 (corresponding to issued Claims 1-3) under 35
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`U.S.C. § 103. Ex. 1003 (8/6/2004 OA) at 3-5. The examiner found that
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`calculating the average echo phase offset and using the average offset to remove
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`echo components was known based on, at least the following references, Moose
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`(U.S. Pat. No. 5,166,924) (“Moose ‘924”) and Andren (U.S. Pat. No. 5,732,105)
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`(“Andren”). Ex. 1003 (8/6/2004 OA) at 4; Exs. 1004, 1005.
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`Importantly, the applicant did not (and could not) dispute or challenge the
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`examiner’s analysis and findings that calculating the average echo phase offset and
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`using the average offset to correct for the effects caused by echoes (and the steps
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`that proceed the averaging, such as determining the phase difference across
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`simultaneous MCM carrier) were all known. Ex. 1003 (12/6/2004 Reply) at 2; Ex.
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`Petition for Inter Partes Review
`U.S. Patent No. 6,931,084
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`1002 (Lyon) at ¶¶ 103-108. Indeed, the following references not identified during
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`prosecution of the ‘266 Application confirm that echo phase offset corrections in
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`multi-carrier modulation (MCM) broadcasting systems were well known:
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`Tsujishita (U.S. Pat. No. 6,341,123 Patent) (“Tsujishita” or the “‘123 Patent”) Ex.
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`1006, and Moose, “Differential Modulation And Demodulation Of Multi-
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`Frequency Digital Communications Signals” (“Moose 1990”) Ex. 1007. See also
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`Schmidl (U.S. Pat. No. 5,732,113) (“Schmidl”) Ex. 1008. For example, prior art
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`systems described in ‘‘123 patent explain that problems caused by echoes can be
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`solved by determining the average offset between the phases of symbols on
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`carriers of the same frequency but in adjacent MCM symbols, and then using the
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`average of these offsets to correct each decoded phase shift by eliminating
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`deviation (error) in the local carrier frequency. This is fundamentally what is
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`found in the Challenged Claims. Ex. 1006 (Tsujishita) at 1:10-17, 2:19-22, and
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`Figure 16 (conventional DAB with phase error detector 12).
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`During prosecution of the ‘266 Application, the applicant accepted that
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`using an average echo phase offset in an MCM system was obvious and amended
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`claims 19-21 to traverse the §102 and §103 rejections based on Moose ‘924 and
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`Andren. Ex. 1003 (12/6/2004 Reply) at 2. The applicant was forced to add a
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`requirement that the absolute value of the signal used to calculate the average echo
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`phase offset had to meet or exceed a set threshold. Ex. 1003 (12/6/2004 Reply) at
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`2. As such, application claims 19-21 (corresponding to issued Claims 1-3) include
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`the step of “comparing an absolute value of a symbol associated with a respective
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`decoded phase shift with a threshold, wherein only phase shifts having associated
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`therewith symbols having an absolute value exceeding said threshold are used in
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`said step of averaging said echo phase offsets.” Id.; see also Ex. 1001 (‘1084
`
`Patent) Claims 1-3. Thus, the Patent Office, based on the cited references,
`
`considered that the only purportedly novel aspect of the methods claimed in
`
`application claim 19-21 (corresponding to Claims 1-3 of the ‘1084 Patent) is that
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`an absolute value of a symbol associated with a respective decoded phase shift
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`with a threshold must be compared to (and meet or exceed) a threshold in order to
`
`be used in said step of averaging said echo phase offsets. Ex. 1003 (8/6/2004 OA)
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`at 3-5; Ex 1002 (Lyon) at ¶¶ 105-108.
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`Notwithstanding the applicant’s amendment, as demonstrated below, it
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`would have been obvious to POSA to require echo phase offset data to meet a
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`threshold value before using it to calculate average echo phase offset to ensure the
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`data is statistically significant and useful. Ex. 1002 (Lyon) at ¶¶ 105-108, 119-
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`124, 132-135. Setting threshold values to determine whether phase error data is
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`reliable and/or meaningful is a basic and well-known principle. Id. at ¶¶ 108, 123-
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`124, 135-137, 150-154. Indeed, the Koslov reference expressly discusses use of
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`such threshold setting as part of the process for calculating echo phase offsets. Ex.
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`1002 (Lyon) at ¶¶ 123-124, 132-137, 150-154 (citing Ex. 1009 (Koslov, U.S. Pat.
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`No. 5,940,450) (“Koslov”) at 2:27-57, 3:1-28, 4:46-58).
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`In addition to setting a single threshold value, more complex systems were
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`known where the values used for averaging the phase errors could effectively use
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`selective scaling to make contributions from higher magnitude symbols more
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`important. Ex. 1002 (Lyon) ¶¶ 123-124. For example, phase errors could be
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`scaled and thus given more weight based on the value of the associated symbol.
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`Id. (citing Ex 1010 (Robertson; “Analysis of the Effect of Phase-Noise in
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`Orthogonal Frequency Division Multiplex (OFDM) Systems”) at § 7).
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`Accordingly, for these and other reasons described more particularly below,
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`Petitioner respectfully requests that the Board find each of the Challenged Claims
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`obvious under 35 U.S.C. § 103 in view of the various teachings of Tsujishita,
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`Moose 1990, and Koslov.
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`II. MANDATORY NOTICES
` Real Party in Interest A.
`
`The Real Party in Interest is Sirius XM Radio Inc.
`
` Related Matters B.
`
`Patent Owner asserted the ‘997 Patent against Petitioner in Fraunhofer-
`
`Gesellschaft zur Förderung der angewandten Forschung e.V. v. Sirius XM Radio
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`Inc., 1:17-cv-00184 (D. Del. Feb. 22, 2017) (the “Litigation”). Petitioner has also
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`Petition for Inter Partes Review
`U.S. Patent No. 6,931,084
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`filed petitions for inter partes review of U.S. Patent Nos. 6,314,289; 7,061,997 and
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`6,933,084, which Patent Owner also asserted against Petitioner in the foregoing
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`litigation. Shortly after the Patent Owner filed the Litigation, Petitioner filed a
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`motion to dismiss the Complaint on grounds that Petitioner has had a license to the
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`‘997 Patent because of a license granted to Petitioner by the Patent Owner through
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`an intermediary. Litigation at D.I. 10-13, 19-21, 29. That motion is currently
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`pending before the District Court.
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`
` Lead and Backup Counsel C.
`Lead Counsel
`Jonathan S. Caplan
`jcaplan@kramerlevin.com
`Reg. No. 38,094
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`
`
`Backup Counsel
`Mark A. Baghdassarian
`mbaghdassarian@kramerlevin.com
`Pro Hac Vice to be requested
`
`Jeffrey H. Price
`jprice@kramerlevin.com
`Reg. No. 69,141
`
`Kramer Levin Naftalis & Frankel LLP
`1177 Avenue of the Americas
`New York, NY 10036
`Tel: 212.715.9100 Fax: 212.715.8000
`
`
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`Service Information
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`D.
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`Sirius XM consents to electronic service at the email addresses listed above.
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`Petition for Inter Partes Review
`U.S. Patent No. 6,931,084
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`III. PAYMENT OF FEES (37 C.F.R. § 42.103)
`Petitioner authorizes the U.S. Patent and Trademark Office to charge
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`Deposit Account No. 50-0540 for the fee set in 37 C.F.R. § 42.15(a) for this
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`petition and for any additional fees.
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`IV. REQUIREMENTS FOR INTER PARTES REVIEW UNDER
`37 C.F.R. §§ 42.104
`
` Grounds for Standing (37 C.F.R. § 42.104(A)) A.
`Sirius XM certifies, under 37 C.F.R. § 42.104(a), that the ‘1084 patent is
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`available for inter partes review, and Sirius XM is not barred or estopped from
`
`requesting inter partes review of the ‘1084 patent on the grounds identified.
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`B.
`
`
`Identification of Challenged Claims
`(37 C.F.R. § 42.104(B)(1))
`Petitioner requests inter partes review of the Challenged Claims of the ‘1084
`
`Patent (i.e., Claims 1-3) on the grounds set forth below, and requests that these
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`claims be found unpatentable.
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`
` Claims and Statutory Grounds Under §§ 42.22 and 42.104(B)(2) C.
`(37 C.F.R. § 42.104(B)(2))
`
`The priority date for the ‘1084 Patent is April 14, 1998, the filing date of the
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`PCT international stage application (PCT/EP98/02169) to which the ‘3084 Patent
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`claims priority. Petitioner asserts that the Challenged Claims are unpatentable as
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`follows:
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`Petition for Inter Partes Review
`U.S. Patent No. 6,931,084
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`Ground Claim(s)
`1
`1-3
`
`Basis
`Obvious under § 103 by Tsujishita (6,341,123 Patent)
`in view of Moose 1990 and/or the knowledge of a POSA
`
`2
`
`1-3
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`
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`Obvious under § 103 by Tsujishita (6,341,123 Patent)
`in view of Moose 1990, Koslov (5,940,450) and/or the
`knowledge of a POSA
`
`The detailed claim charts and discussion in Section VII below set forth the bases
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`for the unpatentability of the Challenged Claims. Additional support is set forth in
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`the accompanying Declaration of David Lyon, Ph.D. Ex. 1002.
`
`
` Claim Construction (37 C.F.R. § 42.104(B)(3)) D.
`For the purposes of this review, Petitioners construe the claim language such
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`that it is “given its broadest reasonable construction in light of the specification of
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`the patent in which it appears” (“BRI”). Because the BRI standard for claim
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`construction at the USPTO is different than that used in District Court litigation,
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`see In re Am. Acad. of Sci. Tech Ctr., 367 F.3d 1359, 1364, 1369 (Fed. Cir. 2004),
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`MPEP § 2111, Petitioner reserves the right to argue a different claim construction
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`in a different forum for any term in the ‘1084 Patent as appropriate in that
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`proceeding.
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`V.
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`SUMMARY OF THE ‘1084 PATENT AND ITS TECHNICAL FIELD
`
`The ‘1084 Patent describes well-known techniques for modifying data
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`corrupted by echoes in multi-carrier demodulation systems where differential
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`phase decoding shifts is performed based on a phase difference between
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`simultaneous carrier waves having different frequencies. Ex. 1002 (Lyon) ¶¶ 37,
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`38, 91-102.
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`
` Overview of the Technical Field A.
`Explained below is an overview of the basic fundamentals of
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`communication systems, including (a) the basics of transmissions using
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`frequencies, carriers, signals and symbols; (b) the use of what is called binary and
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`quadrature phase shift keying; (c) the use of multi-carrier modulated or MCM
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`transmissions using orthogonal frequency division multiplexing (OFDM)
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`transmission; and (d) the correction of echoes resulting from the transmission of
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`signals. Additional description of the field is included in the accompanying Lyon
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`Declaration. Ex. 1002 (Lyon) ¶¶ 38.
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`1.
`
`Transmissions Using Frequencies, Carriers, Signals And
`Symbols
`
`In most wide area, radio communication systems, a network owner/operator
`
`is granted a license by the United States Federal Communication Commission (the
`
`“FCC”) to transmit their signals in a particular piece of the radio frequency
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`spectrum. The network operator will convey information over their licensed
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`spectrum by modulating that information onto one or more radio carriers. Id. at
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`¶44-46(citing Ex. 1012 (Lathi) at p. 12). A simple and important example of a
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`carrier is a sinusoidal signal that oscillates at the selected carrier radio frequency.
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`Id.
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`To transmit information, it is necessary to systematically modify one or
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`more parameters of the carrier. This systematic modification of a carrier is referred
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`to as modulation. Two of the more common forms of modulation are amplitude
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`modulation and phase modulation. Id. at ¶¶ 47-49.
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`Amplitude modulation refers to modifying the amplitude, (i.e. peak to peak
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`size), of the carrier in order to convey information. Id. (citing Ex. 1012 (Lathi) at
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`pp. 12-13, pp. 222-224, and pp. 234-235). The amplitudes of the modulated carrier
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`waveform convey to the receiver the bit values that are being transmitted in a
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`particular time frame (called a symbol time). Id.
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`Phase Modulation
`
`2.
`Another common way of transmitting information is to use phase
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`modulation by amplitude modulating both the cosine (real, see below) carrier and
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`sine (imaginary) carrier during each symbol time a transmitter can produce
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`amplitude and/or phase modulated symbols. Id. at ¶¶ 50-55 (citing Ex. 1012
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`(Lathi) at p. 12 and Ex. 1013 (Proakis) at p. 225 and pp. 258-261).
`
`The simplest form of phase modulation is called “binary phase shift keying”
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`(also known as “BPSK”) and is illustrated below in Figure 1. Id. In Figure 1, a 0
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`bit corresponds to a starting phase of the symbol of a carrier at 0° and a 1 bit
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`corresponds to a starting phase of a symbol of a carrier at 180. Id. (citing Ex. 1013
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`(Proakis) at pp. 231-232 and p. 245).
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`
`
`Figure 1 BPSK phase modulation
`
`Engineers illustrate symbols by representing them as complex numbers.
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`Complex numbers have a real and imaginary part and are usually written in the
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`form (a + i.b), where i is the square root of -1, i.e. i = √ -1. Id. (citing Ex. 1013
`
`(Proakis) at pp. 225-226). Complex numbers in mathematics can be plotted on the
`
`complex plane, which is represented by the x-y axis. Id. Symbols represented as
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`complex numbers have a real part (‘a’ in the preceding equation which multiplies
`
`the cosine function at the carrier frequency) and an imaginary part (‘b’ in the
`
`preceding equation which multiplies the sine at the same carrier frequency). Id.
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`The real part is shown on the x-axis and the imaginary part is shown on the y-axis.
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`Id.
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`Rather than using just two phases to represent information, it is possible to
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`use four or eight phases instead. Id. (citing Ex. 1013 (Proakis) at pp. 265-271). In
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`the case of four phases, each phase represents two bits of information, as 22 = 4,
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`whereas for eight phases, each phase represents three bits of information as 23 = 8.
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`Figure 2 shows a complex plane representation of a system using four phases. Id.
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`The symbols representing the bit pairs and their corresponding phases are: ’00’
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`with a phase of 0°, ’01’ with phase 90°, ’10’ is -90°, and ’11’ is 180°. Id.
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`Grouping bits together in pairs and mapping them to these four different phases is
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`called Quadrature Phase Shift Keying (QPSK). Id.
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`Figure 2 QPSK Phase Modulation
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`Petition for Inter Partes Review
`U.S. Patent No. 6,931,084
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`3.
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`Phase Modulation in Satellite and Multi Carrier
`Modulation Transmissions
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`BPSK and QPSK modulation schemes utilizing a single carrier frequency
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`are commonly used with satellite transmission systems. Id. at ¶¶ 56-65 (citing Ex.
`
`1014 (Zou) at pp. 2-5). For terrestrial radio transmissions, a well-known technique
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`called Multi-Carrier Modulation (also referred to as MCM) is often used because it
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`has desirable properties related to reducing the disruptive effects of multipath
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`propagation. Id. Further below we illustrate how BPSK and QPSK can be used in
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`MCM systems. Id. MCM is also commonly referred to as OFDM (which stands
`
`for Orthogonal Frequency Division Multiplexing) and sometimes DMT (Digital
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`Dual-Tone). Id.
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`Transmitting via a satellite can be thought of as using a single “fat pipe”
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`(i.e., a single signal or carrier) through which all of the bits and symbols are sent.
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`Id. By contrast, with an MCM transmission, instead of a fat pipe, the same bits
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`and symbols are transmitted through a myriad of skinny pipes (i.e., many signals or
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`modulated carriers, often referred to as subcarriers) all stacked right next to each
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`other in the frequency spectrum as illustrated in Figure 3 below:
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`U.S. Patent No. 6,931,084
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`Figure 3. Illustrative comparison of QPSK and MCM transmission of
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`bits
`Id. (citing Ex. 1014 (Zou) at p. 2).
`
`A carrier or equivalent subcarrier in a terrestrial MCM transmission is
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`modulated in the same way described above for modulating a carrier transmitted
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`over a satellite (such as with BPSK or QPSK). Id. (citing Ex. 1014 (Zou) at pp. 2-
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`3). That is, each subcarrier can be modulated with QPSK (or BPSK or more
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`generally M-PSK) and so each subcarrier conveys a fraction of the bits that
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`represent the information being conveyed to the user (e.g., the digitized audio). Id.
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`MCM has two dimensions – a frequency dimension and a time dimension –
`
`as illustrated in Figure 4 below.
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`Figure 4
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`Id. (citing Ex. 1014 (Zou) at pp. 3-4).
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`The first dimension in an MCM transmission is the “frequency” dimension.
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`Each set of subcarrier symbols is transmitted over its own distinct frequency and
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`each unit in the frequency direction is called a “subcarrier.” Id. The frequency
`
`dimension in the Figure 4 above is represented by each of the subcarriers – i.e.,
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`SC1 represents subcarrier 1; SC2 represents subcarrier 2; SC3 represents subcarrier
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`3; and so on until the last subcarrier, which is 100 in the Figure 4 above. Id.
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`The second dimension is the “time” dimension and each complete unit in the
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`time direction (containing all the subcarriers in that frequency is called an MCM
`
`Symbol. Id. Each individual subcarrier carries a sequence of symbols with those
`
`symbols transmitted one at a time. Id. In the figure above, the subcarrier symbols
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`are represented by the rows of colored boxes, where an MCM Symbol is
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`represented by each row of boxes having the same color. Id.
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`U.S. Patent No. 6,931,084
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`In Figure 4, SC1 represents the first subcarrier of the MCM transmission and
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`the individually colored boxes represent each of the subcarrier symbols found on
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`that subcarrier over some period of time. Id. SC2 represents the second subcarrier
`
`and the individually colored boxes represent each of the subcarrier symbols found
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`on that subcarrier. Id. An MCM transmission can have hundreds of subcarriers
`
`with each subcarrier carrying sequences of subcarrier symbols. For purposes of
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`this illustration, the Figure 4 shows 100 subcarriers with each subcarrier carrying
`
`three subcarrier symbols over a period of time. Id.
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`Each of the subcarriers in an MCM system can be modulated in many
`
`different ways. Id. A common modulation scheme is QPSK (described above),
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`and in this case each subcarrier symbol carries two bits of information. Id. Thus,
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`to transmit information in this kind of an MCM system, it is necessary to modulate
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`each subcarrier such that its phase takes one of the four values 0, +90, -90 and 180°
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`depending upon the bit pairs to be transmitted. Id.
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`It is normal for the transmitted signal to undergo corruption before it reaches
`
`the receiver. Id. (citing Ex. 1013 (Proakis) at pp. 258-269, pp. 272-273 and pp.
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`702-713). This corruption can include amplitude corruption (that is not all signals
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`retain the same amplitude), phase rotation (that is the entire signal is rotated in the
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`complex plane such that rather than being at nominal phase differences of 0, +90, -
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`90 and 180°, instead the phase difference are at, for example, +15, 105, -65 and
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`195°), and phase distortion (that is rather than being spaced 90° apart, the phase
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`difference vary from subcarrier to subcarrier). Id. These various forms of
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`corruption are constantly changing, and so the receiver must account for and
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`correct for those changes. Id.
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`Correcting for Multi-Path or Echo Effects
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`4.
`One of the issues that often arises between transmission of a signal and
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`receipt by a receiver is called multi-path. Id. at ¶¶ 66-90 (citing Ex. 1013 (Proakis)
`
`at pp. 702-713.) As the signal travels from the transmitter to the receiver in an
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`MCM transmission, there are several paths that the signal can take, such as (a)
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`going directly from the transmitter to the receiver; or (b) going from the transmitter
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`and then bouncing off one or more buildings and then reflecting back towards the
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`receiver. Id. Each path will delay the arrival of the signal at the receiver by a
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`different amount of time. Id. Each path will also lead to a different amount of
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`signal power loss and a different rotation of the phase of the subcarrier symbols.
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`Because each transmission path has a different length, the signal transported
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`on each path is received at a different point in time by the receiver (for example, a
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`signal bouncing off two buildings often times will arrive at the receiver later than a
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`signal bouncing off only one building). Id. The result is that the receiver observes
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`multiple copies of the same signal (referred to as echoes in the ‘1084 Patent). Id.
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`At the receiver, when multiple paths or echoes of signals are received by the
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`receiver, all of those signals add up together and are presented to the receiver as
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`one combined signal. As a result, the receiver cannot observe the signal from each
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`path individually because all of the copies of the signals received by the receiver
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`are added together. Id.
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`In real world transmission, each signal propagated over a particular path
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`received by the receiver has suffered a different amount of amplitude loss, a
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`different amount of time delay, as well as a different amount of carrier phase
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`rotation – that is, the different multipath signals are not the same as one another.
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`Id.
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`The effect of the overall scaling and phase rotation on the signal received by
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`the receiver is unknown to the receiver. Id. (citing Ex. 1013 (Proakis) at p. 265).
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`As a result, the receiver typically cannot know with high confidence which QPSK
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`subcarrier constellation point was originally transmitted and thus cannot extract the
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`information transmitted with low error probability. Id.
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`When QPSK is used for the modulation of the subcarriers, the phase of the
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`received signal is what matters because with QPSK, the four constellation points
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`are distinguished from each other by their phase (and therefore the amplitude does
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`not matter for detecting which QPSK symbol was transmitted). Id. (citing Ex. 1013
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`(Proakis) at p. 225 and pp. 258-261).
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`In order for the receiver to determine the transmitted QPSK constellation
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`point and be able to extract the transmitted information, the receiver must
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`determine the phase rotation that occurred. Id. (citing Ex. 1013 (Proakis) at pp.
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`265-266). To determine the phase rotation, differential encoding at the transmitter
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`with the matching differential decoding at the receiver is used, meaning that the
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`transmitted information is encoded in the phase difference between two adjacent
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`carriers and not in the absolute phase of either. Id.
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`Differential phase decoding is the inverse operation of differential phase
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`encoding and is performed by taking the difference in the angles (phases) between
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`adjacent modulated carriers (symbols). Id.
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`When differential decoding is performed, the phases of adjacent symbols are
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`subtracted from one another and this subtraction removes any common phase
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`rotation between the two adjacent symbols. Id. However, adjacent MCM
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`subcarriers do not undergo exactly the same phase rotation, and thus subtracting
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`two adjacent subcarriers typica
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