T 0276/09 (Multiplication-free signal processing/LUCENT) of 17.10.2012

Summary of Facts and Submissions

I. The appeal is against the decision of the examining division, posted on 2 July 2008, refusing European patent application No. 00307409.3 on the grounds of added subject-matter (Article 123(2) EPC) and lack of support of the claims by the description (Article 84 EPC 1973) regarding a main request, while a late-filed auxiliary request was not admitted into the examination proceedings under Rule 116(1) EPC 1973.

The following documents were cited in the examination proceedings:

D1: S. Ariyavisitakul and L.J. Greenstein: "Redu-

ced-Complexity Equalization Techniques for

Broadband Wireless Channels", IEEE Journal On

Selected Areas in Communications, pages 5-15,

January 1997;

D2: G.M. Durant and S. Ariyavisitakul: "Implemen-

tation of a Broadband Equalizer for High-Speed

Wireless Data Applications", Proceedings of IEEE

International Conference on Universal Personal

Communications, pages 1015-1020, October 1998;

D3: US-A-4 381 546.

II. Notice of appeal was received on 28 August 2008. The appeal fee was paid on the same day. The statement setting out the grounds of appeal was received on 12 November 2008. The appellant requested that the decision of the examining division be set aside in its entirety and that a patent be granted on the basis of a new set of claims (claims 1 to 18) according to a main request or to an auxiliary request, both filed with the statement setting out the grounds of appeal. In addition, oral proceedings were requested as an auxiliary measure.

III. A summons to oral proceedings scheduled for 26 October 2012 was issued on 29 May 2012. In an annex to this summons pursuant to Article 15(1) RPBA, the board expressed its preliminary opinion on the appeal. In particular, objections were raised under Articles 123(2) EPC, 84 EPC 1973 and Article 52(1) EPC in conjunction with Articles 54 and 56 EPC 1973 with respect to the main request. The appellant was also informed that the claims of the auxiliary request were considered to fulfil the requirements of the EPC.

IV. With a letter of reply dated 26 September 2012, the appellant filed another set of claims (claims 1 to 18) according to a new main request replacing the claims of the former main request. Moreover, it was requested that the procedure be continued in writing.

V. With a communication dated 17 October 2012, the appellant was informed that the oral proceedings appointed for 26 October 2012 were cancelled.

VI. Independent claim 1 of the new main request reads as follows:

"A method of processing information in a receiver (100; 120) of a digital communication system, the method comprising the step of:

applying a signal processing operation to a sequence of transmitted symbols, wherein the transmitted symbols correspond to points in a first modulation constellation, the first modulation constellation corresponds to a rotated version of a second modulation constellation, and each of the transmitted symbols represents a particular number of information bits including a first information bit b0 and a second information bit b1;

the signal processing operation utilizing at least one selector (30) to compute a product of an element of a channel estimate and a given one of the transmitted symbols;

CHARACTERIZED IN THAT the selector comprises first and second controllable inverters (10-1, 10-2) and first and second switches (12-1, 12-2), the first and second controllable inverters being adapted to receive respective real and imaginary parts of the element of the channel estimate, said first controllable inverter either inverting or not inverting the real part based on a first control signal, the first control signal being determined by b1, said second controllable inverter either inverting or not inverting the imaginary part based on a second control signal, the second control signal being determined by both b0 and b1, wherein each of the first and second switches has one input adapted to receive the inverted or non?inverted real part from the first controllable inverter and another input adapted to receive the inverted or non-inverted imaginary part from the second controllable inverter, each of the first and second switches being operative to select as its output one of its two inputs responsive to a third control signal, the third control signal being determined by b0, wherein the outputs of the first and second switches provide respective real and imaginary parts of a product of the element of the channel estimate and the given symbol."

The further independent claims 10 and 18 of the new main request are directed towards a corresponding apparatus and system, respectively.

Reasons for the Decision

1. Admissibility of the appeal

The appeal complies with the provisions of Articles 106 to 108 EPC (cf. point II above) and is therefore admissible.

2. New Main Request (Sole Request)

This request was filed in response to the objections raised in the board's communication under Article 15(1) RPBA and is therefore admitted into the proceedings under Article 13(1) RPBA.

The claims of this request are identical to those of the auxiliary request filed with the statement setting out the grounds of appeal and differ from the claims of the main request underlying the appealed decision in that independent claims 1, 10, and 18 as amended further specify that

(a) the selector includes controllable inverters which

invert the respective real and imaginary parts of

the channel estimates based on first and second

control signals, while the corresponding switches

generate the resulting product based on the

inverters' outputs and a third control signal;

(b) the transmitted symbols include a first information

bit b0 and a second information bit b1;

(c) the first control signal is determined by b1;

(d) the second control signal is determined by both

b0 and b1;

(e) the third control signal is determined by b0.

2.1 Article 123(2) EPC

2.1.1 The added feature (a) is supported by the disclosure of page 8, lines 5-10 in conjunction with Fig. 3 of the application as filed.

The added feature (b) is based on the disclosure of page 8, lines 4-5 in combination with Fig. 2, while added features (c) to (e) are supported, for example, by Fig. 3 of the application as filed.

2.1.2 As a result of the above amendments made in response to the objections under Article 123(2) EPC raised by the examining division (cf. appealed decision, sections 3.1 and 3.2) and by the board (cf. board's communication under Article 15(1) RPBA, section 3.1), the board is satisfied that those objections no longer apply.

Therefore, the board concludes that the application complies with the provision of Article 123(2) EPC.

2.2 Article 84 EPC 1973: Support by the description

Likewise, the board judges that the claims are now supported by the description as required by Article 84 EPC 1973 due to the amendments made to the claims.

2.3 Article 52(1) EPC: Novelty and inventive step

In the board's judgment, the present claims meet the requirements of Article 52(1) EPC for the following reasons:

2.3.1 The board concurs with the examining division in considering D2 as the closest prior art.

2.3.2 Document D2 is related to a decision-feedback equaliser (DFE) technique for QPSK-based wireless broadband communications with reduced complexity and discloses, with regard to the wording of claim 1, a method of processing information in a receiver of a digital communication system (see e.g. Fig. 1) utilising a selector (viz. "feedback filter FBF") to compute a product of channel estimates (viz. "hk") and transmitted symbols (viz. "xn"). Moreover, using symbols of value ±1±j in D2 (see page 1016, left-hand column, lines 8-13) implies that pi/4-QPSK is adopted, i.e. that the symbols are rotated by 45° with respect to conventional QPSK modulation and thus correspond to a rotated modulation constellation as claimed.

2.3.3 The difference between the subject-matter of claim 1 and the disclosure of D2 is seen as being that

(i) the selector comprises first and second

controllable inverters and first and second

switches;

(ii) the first and second controllable inverters are

adapted to receive respective real and imaginary

parts of the element of the channel estimate,

said first controllable inverter either inverting

or not inverting the real part based on a first

control signal being determined by b1, said

second controllable inverter either inverting or

not inverting the imaginary part based on a

second control signal being determined by both b0

and b1;

(iii) each of the switches has one input adapted to

receive the inverted or non-inverted real part

from the first controllable inverter and another

input adapted to receive the respective inverted

or non-inverted imaginary part from the second

controllable inverter, each of the switches being

operative to select as its output one of its two

inputs responsive to a third control signal being

determined by b0, wherein the outputs of the

first and second switches provide respective real

and imaginary parts of a product of the element

of the channel estimate and the given symbol.

2.3.4 As a consequence, the subject-matter of claim 1 is new over the cited prior art (Article 54 EPC 1973).

2.3.5 The objective problem associated with claim 1 is therefore regarded as being how to implement the calculation of real and imaginary parts of an inner vector product made up of channel estimation weights and transmitted symbols at a QPSK-based digital data receiver without performing complex-number multipli-cations.

2.3.6 D2, albeit touching on the issue of multiplication-free implementation of feedback filters for QPSK-based communications, does not provide a hint towards the separate calculation of real and imaginary parts without resorting to complex-number multiplications. Rather, D2 merely teaches replacing multiplications for correlating complex values in a QPSK-based receiver implementation by using additions (see e.g. page 1016, left-hand column, lines 8-13; page 1018, left-hand column, second paragraph) while being silent as to calculations of the real and imaginary parts of a symbol/channel estimate product via inverters and switches based on control signals depending on the respective information bits of incoming symbols.

2.3.6 Likewise, D1 solely discloses the replacement of multiplications by additions for the purpose of correlating complex values in a QPSK-based receiver implementation, thus clearly leading away from calculating real and imaginary parts of an inner vector product using inverters and switches based on control signals depending on the incoming symbols. Therefore, even if the teachings of D2 and D1 were combined, the skilled person would not arrive at the claimed solution.

Finally, D3 deals with a 45°-rotation of QAM-based transmissions at the receiver for channel impairment measurements, but it is silent as to building products of channel estimate coefficients and incoming symbols.

2.3.7 Therefore, the subject-matter of claim 1 is also found to be inventive in the light of the cited prior art (Article 56 EPC 1973).

Since the subject-matter of the further independent claims 10 and 18 corresponds to that of claim 1, the above reasoning also applies to those claims.

2.3.8 In conclusion, the subject-matter of the present claims is new and involves an inventive step within the meaning of Articles 54 and 56 EPC 1973.

2.4 Since all the other requirements of the EPC are also found to be fulfilled, the board decides to grant a patent on the basis of claims 1 to 18 according to the new main request.

Order

For these reasons it is decided that:

1. The decision under appeal is set aside.

2. The case is remitted to the department of first instance with the order to grant a patent in the following version:

Description (pages):

- 1, 4 to 20 as originally filed;

- 2, 3 filed with the letter of 30 June 2004;

- 2a filed with the letter of 14 June 2007;

Claims (nos.):

- 1 to 18 filed with the letter of 26 September 2012;

Drawings (sheets):

- 1/8 to 8/8 as originally filed.