Ex Parte Tanaka et alDownload PDFPatent Trial and Appeal BoardJan 27, 201511926327 (P.T.A.B. Jan. 27, 2015) Copy Citation UNITED STATES PATENT AND TRADEMARK OFFICE ____________________ BEFORE THE PATENT TRIAL AND APPEAL BOARD ____________________ Ex parte MASATO TANAKA and HIROJI AKAHORI ____________________ Appeal 2012-007094 Application 11/926,327 Technology Center 2400 ____________________ Before ELENI MANTIS MERCADER, MICHAEL J. STRAUSS, and HUNG H. BUI, Administrative Patent Judges. MANTIS MERCADER, Administrative Patent Judge. DECISION ON APPEAL Appeal 2012-007094 Application 11/926,327 2 STATEMENT OF THE CASE Appellants appeal under 35 U.S.C. § 134(a) from a rejection of claims 1–4 and 6–16. We have jurisdiction under 35 U.S.C. § 6(b). We affirm. THE INVENTION The claims are directed to an orthogonal frequency division multiplex (OFDM) signal equalizer. Abstract. Claim 1, reproduced below, is representative of the claimed subject matter: 1. An equalizer which equalizes a received orthogonal frequency division multiplex (OFDM) signal which includes periodic pilot symbols, said equalizer comprising: a channel estimation unit which estimates a frequency response of a transmission channel of the received OFDM signal; and an equalization circuit which equalizes the received OFDM signal in accordance with the frequency response estimated by the channel estimation unit, and which outputs a resultant equalized OFDM signal, wherein the channel estimation unit determines complex gain amounts of respective propagation channels of the OFDM signal based on the pilot symbols, applies the complex gain amounts to a window function circuit which passes given complex gain amounts among the complex gain amounts which are contained within a predetermined time region window, and computes the frequency response based on the given complex gain amounts which are contained within the predetermined time region window, and wherein the window function circuit cuts out the complex gain amounts so that the given complex gain amounts are centered at a middle of one symbol period. REFERENCES Kloos US 6,909,761 B2 Jun. 21, 2005 Appeal 2012-007094 Application 11/926,327 3 Vijayan McCoy US 2005/0249181 A1 US 2007/0201349 A1 Nov. 10, 2005 Aug. 30, 2007 (filed Feb. 24, 2006) REJECTIONS1 The Examiner made the following rejections: 1. Claims 1–4, 6–12 and 14–16 stand rejected under 35 U.S.C. § 103(a) as being unpatentable over Vijayan and McCoy. Ans. 5-10. 2. Claim 13 stands rejected under 35 U.S.C. § 103(a) as being unpatentable over Vijayan, McCoy, and Kloos. Ans. 10. ISSUE The dispositive on appeal issue is whether the Examiner erred in combining the teachings of Vijayan and McCoy. ANALYSIS We have reviewed the Examiner’s rejections in light of Appellants’ arguments that the Examiner has erred. We disagree with Appellants’ conclusions. We adopt as our own (1) the findings and reasons set forth by the Examiner in the action from which this appeal is taken and (2) the reasons set forth by the Examiner in the Examiner’s Answer in response to Appellants’ Appeal Brief and concur with the conclusions reached by the Examiner. We highlight the following for emphasis. 1 Appellants argue the rejection of claim 1. Separate patentability is not argued for claims 2-4 and 6-16. Therefore, based on Appellants’ arguments, we decide the appeal of claims 1-4 and 6-16 based on claim 1 alone. See 37 C.F.R. § 41.37(c)(1)(vii). Appeal 2012-007094 Application 11/926,327 4 Appellants argue that one of ordinary skill in the art would have no motivation to modify channel estimator 172 depicted in Figure 8 of Vijayan in view of the window generator 404 of McCoy (App. Br. 9). In particular, Appellants assert that the window generator 404 of McCoy is part of synchronization maintenance function 107 shown in Figure 1, and is for the purpose of adjusting samples r(n) of the received signal to provide synchronization (App. Br. 9). The window function performed by window generator 404 of McCoy is separate and distinct from channel estimator 113 and, as such, is unrelated to channel estimation by channel estimator 113 (App. Br. 9). Appellants argue that one of ordinary skill in the art, looking to improve the channel estimation performed by channel estimator 172 depicted in Figure 8 of Vijayan would have no motivation to consider synchronization maintenance function 107 of McCoy because synchronization maintenance function 107 does not provide channel estimation (App. Br. 10). Instead, synchronization maintenance function 107 of McCoy merely synchronizes the received symbols (App. Br. 10). In contrast, channel estimator 113 depicted in Figure 1 of McCoy performs channel estimation (App. Br. 10). According to Appellants, even though McCoy teaches a window function, that window function is unrelated to channel estimation and thus cannot be used as the basis for modification of the channel estimation of Vijayan (App. Br. 10). We do not agree with Appellants’ arguments. The Examiner finds, and we agree, Vijayan teaches a windowing function applied to the tap indexes (i.e. complex gain amounts of the channel impulse response) in order to determine the FFT window for the received OFDM symbol (¶ 149; Ans. 13). Vijayan also describes computing a frequency response based on Appeal 2012-007094 Application 11/926,327 5 the given complex gain amounts which are contained within the predetermined time region window (Fig. 5, Step 522, ¶ 139; Ans. 13). Vijayan teaches determination of the channel frequency response by performing a Fast Fourier transform (FFT) on the impulse response complex gain amounts which is performed in FFT unit 834 of Figure 8 (Ans. 13). Thus, Vijayan describes the use of a window to select complex gain amounts derived from received pilot symbols and compute the frequency response of the channel by performing a FFT on the complex gain amounts as claimed (Ans. 13). The Examiner acknowledges that Vijayan does not explicitly disclose wherein the window function circuit cuts out the complex gain amounts so that the given complex gain amounts are centered at a middle of one symbol period (Ans. 7, 14). The Examiner then relies on the window function disclosed by McCoy using cross correlation to time-align the symbol duration with the window function to select samples from the center of the symbol period (¶¶ 25–26, DEL of Fig. 6 equals half the distance between L and Nfft) (Ans. 7). Thus, McCoy cures Vijayan’s deficiency by teaching how the window function cuts out samples from the center at the middle of one symbol period (i.e. Nfft) (Fig. 6, ¶¶ 35-37) (Ans. 7). With respect to the motivation to combine the references, the Examiner finds, and we agree, Vijayan is concerned with proper time alignment of the window function to improve performance of channel estimation (see ¶ 143; Ans. 14). The Examiner further notes that McCoy indicates a similar need for proper time alignment of a windowing function in an OFDM receiver (Ans. 14). More particularly, the Examiner finds, and we agree, that Vijayan indicates that the performance of channel estimation can be affected by how the FFT window is aligned with a received symbol Appeal 2012-007094 Application 11/926,327 6 (¶ 143). Similarly, McCoy indicates that by properly aligning a window (i.e. FFT window) one can reduce inter symbol interference and inter carrier interference (¶¶ 2, 12; Ans. 14). In McCoy, the window is applied to a time domain representation of a signal comprising complex values (¶ 17 describing r(n) as a digital or sampled complex signal) (Ans. 14). Thus, both references indicate that proper alignment of FFT windows are important considerations prior to performing an FFT on a time domain signal (Ans. 14). Namely, time aligning a complex signal with a window such that the window is centered on the period of a time domain signal (Ans. 14). The Supreme Court stated “[t]he combination of familiar elements according to known methods is likely to be obvious when it does no more than yield predictable results.†KSR Int’l Co. v. Teleflex Inc., 550 U.S. 398, 416 (2007). Therefore, we agree with the Examiner’s analysis and conclude the Examiner has provided the requisite articulated reasoning with rational underpinnings sufficient to justify the legal conclusion of obviousness. Thus, we affirm the Examiner’s rejection of claim 1 and for the same reasons the Examiner’s rejection of claims 2–4 and 6–16. CONCLUSION The Examiner did not err in combining the teachings of Vijayan and McCoy. DECISION The Examiner’s decision to reject claims 1–4 and 6–16 is affirmed. No time period for taking any subsequent action in connection with this appeal may be extended under 37 C.F.R. § 1.136(a)(1)(iv). Appeal 2012-007094 Application 11/926,327 7 AFFIRMED lv Copy with citationCopy as parenthetical citation