T 2073/15 (Multiple antennas transmission mode selection/QUALCOMM) 24-06-2019

Reasons for the Decision

1. The appeal is admissible (see point II).

2. Main request

The claims are based on the claims of the then first auxiliary request on which the decision was based. It was refused by the examining division for lack of compliance of its claim 1 with the requirements of Article 123(2) EPC, Rule 137(5) EPC, and Article 83 EPC.

2.1 Article 123(2) EPC

Claim 1 has been amended by replacing the feature of "associating the user preference with an entry or entries in a codebook comprising precoding weights to be applied in conjunction with beam forming directly to the beams", objected to under Article 123(2) EPC in the decision, by the feature of "associating the user preference with an entry in a codebook, wherein the entry comprises precoding weights to be applied in conjunction with beam-forming to the beams".

The amended feature specifies that the entry of the codebook which is associated with the received user preference comprises precoding weights to be applied in conjunction with beam-forming to the beams. It is described in the application document as originally filed that the transmission mode can be one of precoding, SDMA, SDMA precoding, MIMO, MIMO precoding, MIMO-SDMA, and diversity (see in particular paragraphs [0008] to [0012]). It is not explicitly described that the transmission mode must be one of these. Paragraph [0032] describes that the number of entries in the codebook, corresponding to the transmission modes, may for example amount to sixty-four. Further, paragraph [0032] ("(e.g. precoding,...MIMO-SDMA, etc.)"), together with paragraph [0071] ("These modes include SDMA,..., and/or the like") and paragraph [0073] ("the modes include SDMA,..., and/or the like") clearly teach that the list of possible transmission modes is not strictly limited to the above mentioned transmission modes. Moreover, among the cited transmission modes, at least precoding SDMA is a mode which uses precoding weights to be applied in conjunction with beam-forming to the beams (see paragraph [0067] and Figure 4). It is thus unambiguously disclosed that the transmission modes corresponding to the entries of the codebook may be modes which are based on precoding weights to be applied in conjunction with beam-forming to the beams.

The above-mentioned replaced feature in claim 1 was also objected to under Article 123(2) EPC in the decision because of the term "directly" in the wording "precoding weights to be applied...directly to the beams". The appellant has overcome this objection by deleting the term "directly" in claim 1. Independent claim 8, however, still contains the term "directly". Nevertheless, the board holds that the feature of applying the precoding weights directly to the beams is supported by the application documents as originally filed. In that respect, paragraphs [0049] and [0050] in combination with Figure 4 teach that the precoding weights are associated and applied to the virtual sectors 404, including a number of beams (five in Figure 4) of the SDMA beam space, i.e. to the virtual sectors 404 formed by the beam-forming operation. Since no other operation on the virtual sectors 404, after they have been formed, is described, the application of the precoding weights to the beams of each virtual sector 404 can be defined as being performed "directly".

For these reasons the board holds that the claims meet the requirements of Article 123(2) EPC.

2.2 Rule 137(5) EPC

The board agrees with the appellant that the feature defining the application of the precoding weights to the beams in conjunction with beam-forming was included in the search.

In that respect, the board notes firstly that, in the search report issued by the EPO as International Searching Authority, the invention which was first defined in the originally filed claims, and which was the subject of the search, was defined as being related to "the set of different transmission modes contained in the codebook, of which one can be selected". This indicates the relevance of the transmission modes for the search.

Secondly, the potential special technical features which were identified at the search stage to make a contribution over prior-art document D1 were the features of originally filed claim 3 that the codebook also included an entry for SDMA. The problem solved by these features was formulated as "How to enhance the set of possible options for the mode selection?". This also clearly indicates that the kind of transmission mode was the subject of the search.

Thirdly, originally filed claim 3, which was included in the search, comprised a list of transmission modes, including SDMA precoding. With respect to SDMA precoding, which was thus included in the scope of the search related to the first invention, the description in paragraph [0067] teaches how sectors, virtual sectors, and beams within a virtual sector, are formed in this transmission mode. This description of SDMA precoding, a feature included in the scope of the search, corresponds fairly well to the description of paragraphs [0049] and [0050] in combination with

Figure 4 related to precoding weights applied in conjunction with beam-forming to the beams.

The board therefore holds that the claims meet the requirements of Rule 137(5) EPC.

2.3 Article 83 EPC

The decision found that the whole description did not disclose how the precoding weights were applied to the beams formed by beam-forming.

The description, inter alia in paragraphs [0036], [0049] in combination with Figure 4, and [0050], clearly mentions that the precoding is applied in the beam space of SDMA beams, i.e. after the beams of the SDMA, shown as virtual sectors including a number of beams and referenced 404 in Figure 4, have been formed. The precoding coefficients, or weights, are thus applied to the beams of the virtual sectors after the data symbols have been multiplied with the beam-forming weights. As stated in the decision (see Reasons 17.3.1 and 17.3.2), both precoding and beam-forming, when performed separately, are based on transmitting the same data symbol on multiple transmit antennas in parallel, wherein a different weight, namely a precoding weight or a beam-forming weight, is applied to the data symbol at each antenna before transmission.

The decision further acknowledged (see Reasons 17.3.4) that the skilled person would consider a multiplication of the weights at each antenna in order to combine precoding and beam-forming processes. It however raised the objection that the skilled person would not be able to implement a workable solution, not inferior to pure precoding and pure beam-forming, without knowledge of how to select the precoding and beam-forming weights.

The board however agrees with the appellant that the aim of beam-forming, known per se, is to create the virtual sectors 404 which focus the transmission towards the user device, while the aim of the precoding applied to the beams of the virtual sectors is to maximise the received signal power in the presence of radio-channel time dispersion. It is thus clear from the description that the selection of the precoding weights is performed depending on the selection of the beam-forming weights in order to achieve the desired effect. Therefore the skilled person would first be able to select beam-forming weights to apply standard beam-forming and create the desired virtual sectors (404 in Figure 4). The skilled person would then be able to select precoding weights applied subsequently to the virtual sectors in order to ensure, as argued by the appellant, that the signals arrive simultaneously at the user device.

For these reasons the board holds that the application meets the requirement of Article 83 EPC.

2.4 Inventive step

Since the issue of inventive step with regard to

prior-art documents D1 and D2 on file has not been addressed in the summons to oral proceedings, during the oral proceedings, or in the decision, the board considers that it is appropriate to remit the case to the department of first instance for further prosecution in that respect (see point 4 below).

3. Procedural violations / Reimbursement of the appeal fee

The appellant requested reimbursement of the appeal fee under Rule 103(1)(a) EPC for violation by the examining division of its right to be heard under Article 113(1) EPC.

The appellant argued in substance that both the refusal of the request for continuation in writing (auxiliary request III) and the refusal of the "late-filed main request" (MR-OP) as inadmissible represent a substantial procedural violation of the right to be heard since these requests were filed in response to the objection under Article 83 EPC raised for the first time during the oral proceedings before the examining division.

The board understands that the "'late-filed main request' (MR-OP)" quoted by the appellant is the request filed by the appellant after the request for continuation in writing (auxiliary request III) was refused, and that it is indistinctively referred to as "latest non-considered request", "last late-filed claim set" and "late-filed main request (MR-OP)" in point 9 of the minutes of the oral proceedings. According to point 9 of these minutes, this request was not admitted into the procedure. The decision, however, does not mention this request (see point 26 and 27). Said "late-filed main request" needs to be distinguished from the "Main Request" and the "New Main Request", which were filed during the oral proceedings and before the "late-filed main request" was filed (see the requests attached to the minutes of the oral proceedings). The "New Main Request" was not admitted into the proceedings for the reasons given in points 20 to 24 of the decision (see also points 7 and 8 of the minutes).

The appellant did not have an a priori right to have the "late-filed main request" admitted into the

first-instance proceedings. However, a party filing a request is always entitled to be heard on why it considers the request should be admitted. If the request is not admitted, this decision must be reasoned (Rule 111(2) EPC). From the minutes of the oral proceedings (point 9), it appears that the admissibility of the "late-filed main request" was briefly discussed before the request was filed. The request filed bears a handwritten remark "not considered by ExDiv" (see the corresponding annex to the minutes). At the end of point 9 of the minutes, a statement is made that the "late-filed main request (MR-OP) is not admitted into the procedure, Rule 116(2) EPC". It is not entirely clear whether this statement refers to the "late-filed main request" or the "New Main Request" as filed earlier during the oral proceedings and also referred to as "MR-OP" (see points 7 and 8 of the minutes). It is clear, however, that the decision does not contain any reference to the "late-filed main request", let alone any reasons as to why it was not admitted into the proceedings.

The board thus holds that the handling of the "late-filed main request" involved a violation of the appellant's right to be heard for the above reasons, and that the request for reimbursement of the appeal fee under Article 103(1)(a) EPC is justified.

On the other hand, the board does not see a procedural violation in the context of the then pending auxiliary request III (continuation in writing to allow consultation with the applicant on the objection under Article 83 EPC against then auxiliary request I). The board agrees with the examining division in that the request should have been made before the debate on the auxiliary request I was closed and before lower-ranking requests were discussed.

4. The board has decided that the main request complies with the requirements of Articles 83 and 123(2) EPC and of Rule 137(5) EPC. However, a remittal for further prosecution is appropriate since the issue of inventive step with regard to prior art documents D1 and D2 was not discussed during the first instance proceedings (see above point 2.4).