Ex Parte Lindqvist et al

Board of Patent Appeals and Interferences

Jun 29, 2009

09584796 (B.P.A.I. Jun. 29, 2009)

UNITED STATES PATENT AND TRADEMARK OFFICE
_____________

BEFORE THE BOARD OF PATENT APPEALS
AND INTERFERENCES
_____________

Ex parte FREDRIK LINDQVIST, ANTONI FERTNER,
and PAL FRENGERT
_____________

Appeal 2009-001682
Application 09/584,796
Technology Center 2600
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Decided:1 June 29, 2009
_______________

Before JOSEPH F. RUGGIERO, MAHSHID D. SAADAT, and ROBERT
E. NAPPI, Administrative Patent Judges.

NAPPI, Administrative Patent Judge.

DECISION ON APPEAL

1 The two-month time period for filing an appeal or commencing a civil
action, as recited in 37 C.F.R. § 1.304, begins to run from the decided date
shown on this page of the decision. The time period does not run from the
Mail Date (paper delivery) or Notification Date (electronic delivery).
Appeal 2009-001682
Application 09/584,796

This is a decision on appeal under 35 U.S.C. § 6(b) of the rejection of
claims 1, 3 through 7, 9 through 28 and 30 through 44.
We reverse.
INVENTION
The invention is directed towards a method for use in multicarrier
communications systems. The method is directed to reducing echo when a
transmitted signal leaks back to a receiver. See page 1 and 2 of Appellants’
Specification. Claim 1 is reproduced below:
1. An echo canceller for use in a transceiver, comprising:
first electronic circuitry configured to estimate in the frequency
domain an echo signal, and
second electronic circuitry configured to remove in the
frequency domain the estimated echo signal in the frequency domain
from a received signal in the frequency domain,
wherein the first electronic circuitry is further configured to
estimate the echo signals in the frequency domain using a
combination of (i) a product of a first matrix of coefficients in the
frequency domain and a transmitted symbol and (ii) a product of a
second matrix of coefficients in the frequency domain and a
previously-transmitted symbol.

REFERENCES
Chaffee US 5,117,418 May 26, 1992
Ho US 5,317,596 May 31, 1994
Dowling US 6,597,745 B1 Jul. 22, 2003

REJECTIONS AT ISSUE
The Examiner has rejected claims 1, 3 through 7, 9 through 17, 20
through 28, and 30 through 43 under 35 U.S.C. § 103(a) as being
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unpatentable over Ho in view of Dowling. The Examiner’s rejection is on
pages 4 through 7 of the Answer.2
The Examiner has rejected claims 18, 19, and 44 under 35 U.S.C.
§ 103(a) as being unpatentable over Chaffee in view of Dowling. The
Examiner’s rejection is on pages 7 through 9 of the Answer.

ISSUES
Obviousness rejection based upon Ho and Dowling.
Appellants argue on pages 17 through 24 of the Brief3 that the
Examiner’s rejection of independent claims 1, 12, 20, 30, and 35 under 35
U.S.C. § 103(a) as being unpatentable over Ho and Dowling is in error.
Appellants state that each of independent claims 1, 12, 20, 30, and 35 recites
estimating and removing echo in the frequency domain and that the
combination of Ho and Dowling does not teach this feature. Appellants
argue that Ho primarily cancels echo in the time domain and residual echo is
removed in the frequency domain. Brief 17. Appellants further argue that
Dowling does not teach estimating and removing an echo signal from a
received signal in the frequency domain. Brief 18.
Thus, Appellants’ contentions present us with the issue: have
Appellants shown that the Examiner erred in finding that the combination of
Ho and Dowling teaches estimating and removing an echo signal as
claimed?

2 Throughout the opinion we refer to the Answer mailed February 27, 2008.
3 Throughout the opinion we refer to the corrected Brief dated January 2,
2008, Reply Brief, dated February 15, 2007 and the Supplemental Reply
Brief dated May 18, 2007.
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Obviousness rejection based upon Chaffee and Dowling.
Appellants argue on pages 24 through 30 of the Brief that the
Examiner’s rejection of claims 18, 19, and 44 under 35 U.S.C. § 103(a) as
being unpatentable over Chaffee and Dowling is in error. Appellants state
that claims 18 and 19 recite estimating echo in the frequency domain based
upon a product of a matrix (claim 19 recites a vector) and the currently
transmitted symbol, and a matrix (vector) and a previously transmitted
symbol. Appellants argue that Chaffee does not teach this feature and that
Dowling teaches a precoder for transmission channel distortion and not echo
estimation as claimed.
Thus, Appellants’ contentions present us with the issue: have
Appellants shown that the Examiner erred in finding that the combination of
Chaffee and Dowling teaches estimating and removing an echo signal as
claimed?
PRINCIPLES OF LAW
Section 103 forbids issuance of a patent when “the
differences between the subject matter sought to be patented
and the prior art are such that the subject matter as a whole
would have been obvious at the time the invention was made to
a person having ordinary skill in the art to which said subject
matter pertains.”
KSR Int'l Co. v. Teleflex Inc., 550 U.S. 398, 405 (2007).
Such a showing requires:
‘some articulated reasoning with some rational underpinning to
support the legal conclusion of obviousness’ . . . [H]owever, the
analysis need not seek out precise teachings directed to the
specific subject matter of the challenged claim, for a court can
take account of the inferences and creative steps that a person
of ordinary skill in the art would employ.
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Id. at 418 (quoting In re Kahn, 441 F.3d 977, 988 (Fed. Cir. 2006)).
Therefore, in analyzing a rejection under 35 U.S.C. § 103, we must
“determine whether there was an apparent reason to combine the known
elements in the fashion claimed.” KSR, 550 U.S. at 418. The proper inquiry
is whether a person of ordinary skill in the art would have seen a benefit to
combining the prior art teachings. KSR, 550 U.S. at 424.
The evidence of record is insufficient to show obviousness if it merely
suggests “to explore a new technology or general approach that seemed to be
a promising field of experimentation, where the prior art gave only general
guidance as to the particular form of the claimed invention or how to achieve
it.” In re O’Farrell, 853 F.2d 894, 903 (Fed. Cir. 1988).
Further, a rejection based on § 103 must rest upon a factual basis
rather than conjecture or speculation. “Where the legal conclusion [of
obviousness] is not supported by the facts it cannot stand.” In re Warner,
379 F.2d 1011, 1017 (CCPA 1967). See also In re Kahn, 441 F.3d at 988.

FINDINGS OF FACT
1. Ho teaches a method for echo cancellation in a full duplex
communication system. The method makes use of frequency domain
echo parameters and time domain echo parameters to produce a
frequency domain echo. The frequency domain echo is converted to a
time domain echo and subtracted from the time domain received
signal. The time domain received signal, with the time domain echo
subtracted is then converted to the frequency domain and the
frequency domain echo is also subtracted. Abstract, col. 4, ll. 30-53.
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2. Ho teaches that the circuit for a transceiver which implements the
method includes an encoder, item 12, and an inverse fast fourier
transform (IFFT) item 14, on the transmit leg. The receiving leg
includes two summing junctions, items 52 and 58, and a fast fourier
transform (FFT) item 56. Between the two legs is an echo canceller
which receives inputs from either side of the IFFT on the transit leg
(i.e. inputs in frequency domain and time domain). These inputs are
processed to emulate and produce an echo component. The echo
canceller provides outputs to each of the summers in the receiver leg
(i.e. output is summed with the received signal in the time domain and
frequency domain) to subtract out the emulated echo and produce an
echo free reception. Figure 3, col. 5, l. 65- col. 6, l. 22.
3. Dowling teaches a precoder which compensates for effects of
intersymbol interference in multicarrier systems. Col. 1, ll. 7-13.
4. Dowling suggests that the precoder may be merged with other
elements of communications systems such as echo cancellers.
However, Dowling provides no details of how the two are to be
merged. Col. 22, ll. 1-6.
5. Chaffee teaches a system for reducing echoes in a duplex
communications system. The transmitted signal is converted to the
frequency domain, and multiplied by filter coefficients to generate
estimated echo coefficients. These echo coefficients are converted to
the time domain and subtracted from the received signal to create a
residual echo signal. The residual echo signal is used to update the
filter coefficient. Abstract.

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ANALYSIS
Obviousness rejection based upon Ho and Dowling.
Appellants’ arguments have persuaded us that the Examiner erred in
finding that the combination of Ho and Dowling teaches estimating and
removing an echo signal as claimed.
Claims 1, 3 through 7, 9 through 17, and 35 through 43
Independent claim 1 recites a first circuitry configured to estimate in the
frequency domain an echo, and that this circuitry is “configured to estimate
echo signals in the frequency domain using a combination of (i) a product of
a first matrix of coefficients in the frequency domain and a transmitted
symbol and (ii) a product of a second matrix of coefficients in the frequency
domain and a previously-transmitted symbol.” Thus, the scope of claim 1
includes that a circuit estimates echo signal in the frequency domain using
both: a) a product of coefficients and a transmitted signal, and b) a product
of a second set of coefficients and a previously transmitted symbol.
Independent claims 12 and 35 recite limitations of similar scope.
In rejecting independent claims 1, 12, and 35 the Examiner finds that
Ho teaches an echo canceller which includes circuitry to estimate and
remove echo signals in the frequency domain. Answer 5. However, the
Examiner notes that Ho does not perform the estimation by using both the
product of a first matrix and first symbol, and the product of a second matrix
and a previously transmitted symbol. The Examiner finds that Dowling
teaches a precoder that compensates for noise by using a combination of a
first matrix and first symbol, and the product of a second matrix and a
previously transmitted symbol. Answer 5. Based upon these findings the
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Examiner concludes that the combination of Dowling’s precoder with the
encoder item 12 of Ho would yield the claimed invention. Answer 10. We
disagree with the Examiner’s conclusion.
Dowling’s precoder is used to precode data for transmission; the
precoding is to compensate for inter-symbol interference in a transmission
channel. Fact 3. While Dowling discloses that the precoder can be used
with echo cancellers, Dowling provides no insight as to how the precoder is
to be used with such systems. Fact 4. Further, Dowling does not teach that
the calculations which use a combination of a first matrix and first symbol,
and the product of a second matrix and a previously transmitted symbol are
used for echo estimation or cancellation. Thus, even if as found by the
Examiner, Dowling’s precoder were used for Ho’s encoder item 12, the echo
canceller item 100, would be using the precoded signal to perform the
estimation of echo, which does not meet the claim limitation of using a
combination of a first matrix and first symbol, and the product of a second
matrix as a previously transmitted symbol, for echo estimation or
cancellation. Accordingly, we will not sustain the Examiner’s rejection of
independent claims 1, 12, and 35 under 35 U.S.C. § 103(a) as being
unpatentable over Ho in view of Dowling. Claims 3 through 7, 9 through
11, 13 through 17 and 36 through 43 ultimately depend upon one of
independent claims 1, 12, and 35. Thus, we similarly will not sustain the
Examiner’s rejection of claims 3 through 7, 9 through 11, 13 through 17, and
36 through 43 under 35 U.S.C. § 103(a) as being unpatentable over Ho in
view of Dowling.
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Claims 20 through 28 and 30 through 34.
Independent claim 20 differs in scope from independent claims 1, 12,
and 35 discussed above in that it does not recite estimating echo signals
using transmitted and previously transmitted signals. Rather, independent
claim 20 recites an echo canceller in a transceiver that uses a frequency
domain model of an echo path channel that takes into account the effects of
inter-carrier interference and to subtract the echo estimate from the received
signal. Independent claim 30 recites using a frequency domain model of an
echo path channel that includes the effects of inter-carrier interference and
inter-symbol interference, to subtract the echo estimate from the received
signal.
In rejecting claims 20 and 30, the Examiner applies the same rationale
discussed above with respect to claim 1 and finds that Dowling discloses
that the precoder takes into account the effects of inter-carrier interference
(ICI). Answer 6. Further, the Examiner finds that the echo path is directly
based on the transmission channel as the transmission channel provides the
impedance mismatch which causes the echo. Answer 15. We disagree with
the Examiner’s rationale. As discussed above, Dowling discloses that the
precoder can be used with echo cancellers, however, Dowling provides no
insight as to how the precoder is to be used with such systems. Fact 4.
Further, Dowling does not teach that the calculations are directed to inter-
symbol or inter-carrier interference that are used for echo estimation or
cancellation. Thus, we do not find sufficient evidence to support the
Examiner’s conclusion that Dowling in combination with Ho teaches using a
frequency domain model of an echo path channel that includes inter-carrier
or inter-symbol interference, as recited in independent claims 20 and 30.
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Claims 21 through 28 and 31 through 34 ultimately depend upon one of
claims 20 and 30. Accordingly, we will not sustain the Examiner’s rejection
of claims 20 through 28 and 30 through 34 under 35 U.S.C. § 103(a) as
being unpatentable over Ho in view of Dowling.

Obviousness rejection based upon Chaffee and Dowling
Claims 18 and 19
Appellants’ arguments have persuaded us that the Examiner erred in
finding that that the combination of Chaffee and Dowling teaches estimating
and removing an echo signal as recited in claims 18 and 19. Claim 18
recites circuitry which uses a combination of the product of a first matrix
and a transmitted symbol and the product of a second matrix and a
previously transmitted symbol to estimate an echo signal in the frequency
domain and to remove the echo in the time domain. Claim 19 recites a
similar limitation, with the exception of the product being between a vector
and symbol.
In rejecting these claims the Examiner finds that Chaffee teaches an
echo canceller which includes circuitry to estimate and remove echo signals
in the frequency domain and remove them in the time domain. Answer 7.
However, the Examiner notes that Chaffee does not perform the estimation
by using both the product of a first matrix and first symbol, and the product
of a second matrix and a previously transmitted symbol. The Examiner
finds that Dowling teaches a precoder that compensates for noise by using a
combination of a first matrix and first symbol, and the product of a second
matrix and a previously transmitted symbol. Answer 5. Based upon these
findings, the Examiner concludes that the combination of Dowling’s
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precoder and the echo canceller of Chaffee would yield the claimed
invention. Answer 10. We disagree with the Examiner’s conclusion.
As discussed above with respect to claim 1, Dowling discloses that the
precoder can be used with echo cancellers; however, Dowling provides no
insight as to how the precoder is to be used with such systems. Fact 4.
Further, Dowling does not teach that the calculations which use a
combination of a first matrix and first symbol, and the product of a second
matrix and a previously transmitted symbol are used for echo estimation or
cancellation. Thus, we do not find that the Examiner has shown that all of
the limitations of independent claims 18 and 19 are taught by the
combination of Chaffee and Dowling and we will not sustain the Examiner’s
rejection of claims 18 and 19 under 35 U.S.C. § 103(a).
Claim 44
On page 9 of the Answer the Examiner rejects dependent claim 44
under 35 U.S.C. § 103(a) as being unpatentable over Chaffee and Dowling.
The Examiner states that the rejection is based, in part, upon the rejection of
claim 35 based upon Chaffee. However, no rejection of claim 35 based
upon Chaffee is before us. Nonetheless, as discussed above we will not
sustain the Examiner’s rejection of claim 35 under 35 U.S.C. § 103(a) based
upon the teachings of Ho and Dowling. Similarly, as discussed with respect
to claims 18 and 19, we do not find that the teachings of Chaffee provide a
teaching of the features not taught by the combination of Ho and Dowling.
Accordingly, we will not sustain the Examiner’s rejection of claim 44.

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ORDER
The decision of the Examiner to reject claims 1, 3 through 7, 9
through 28 and 30 through 44 is reversed.

REVERSED

ELD

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