T 1551/17 (Subsea data communications/SIEMENS) 28-10-2021

1. Main request - novelty (Article 54 EPC)

1.1 Prior-art document DI1 discloses a system for communicating data between a topside control system ("surface facility") and a subsea installation ("subsea facility") over a data transmission line of an umbilical ("communication link", abstract; page 1, line 26 to page 2, line 14; FIG. 1). The topside system and the subsea installation each include a low-speed modem ("LSC Modem" 1/1a) and a high-speed modem ("HSC Modem" 5/5a) (ibid.).

Data transmission line 2 is coupled to the low-speed modems 1/1a via low-pass filters 4/4a and low-speed diplexers 3/3a and to the high-speed modems via

high-speed diplexers 6/6a (FIG. 1). The high-speed diplexers are in turn coupled to the data transmission line via capacitors which ensure a low impedance for the operating frequencies of the high-speed modems and a high impedance for the operating frequencies of the low-speed modems and consequently constitute high-pass filters (page 3, lines 24 to 31; FIG. 3). The low-pass filter in the signal path to the low-speed modem implies that the latter is a "low-frequency modem". Conversely, the high-pass filter in the signal path to the high-speed modem implies that the latter is a "high-frequency modem".

Hence, between the data transmission line and the low- and high-frequency modems at the topside system and those on the subsea side, coupling circuits are arranged which pass the signals in each frequency range to the corresponding modems. Said coupling circuits comprise implicitly a first interface towards the low-frequency modem, a second interface towards the high-frequency modem and a third interface towards the data transmission line, and are considered to be equivalent to the frequency multiplexers as claimed. Moreover, the "diplexer" circuits ensure that the operations of the modems do not affect each other and thus are configured to enable simultaneous communication in both frequency ranges between the topside modems and the subsea modems (cf. abstract).

DI1 therefore discloses a system with all the features of claim 1.

1.2 The proprietor argued that claim 1 described the detailed physical implementation of the system with a topside and a subsea frequency multiplexer, each frequency multiplexer having a first interface towards a low-frequency modem, a second interface towards a high-frequency modem and a third interface towards the data transmission line. Each frequency multiplexer coupled the data transmission line to the low-frequency and to the high-frequency modem. DI1, however, only disclosed on each side of the data transmission line two diplexers, namely diplexer 3 and 6 and diplexer 3a and 6a, and low-pass filters 4 and 4a. These aforementioned components were different entities. The skilled person would not deduce from DI1 that a combination of these components would form a new entity having the three interfaces according to feature 10) and corresponding to the multiplexers as claimed. Claim 1 could not be interpreted as just a distributed system incorporating the respective functions. The proprietor furthermore pointed to the two bidirectional arrows between each diplexer in Figure 1 of DI1 and the respective modem connected to it, and argued that they would render the disclosure unclear.

1.3 The board however notes that DI1, although not using the term "frequency multiplexer", discloses circuits which provide a connection with a low-pass characteristic between the data transmission line and a low-frequency modem as well as a connection with a high-pass characteristic between the data transmission line and a high-frequency modem. As to their functions, these circuits are equivalent to the claimed "frequency multiplexers". Claim 1 attributes the respective functions to an entity called "frequency multiplexer" but does not further specify the frequency multiplexer with respect to its physical implementation. Incidentally, it is noted that also the patent specification only describes the system by means of schematic block diagrams and is silent about their actual physical implementation.

As to the dual bidirectional arrows between the diplexers and the modems in Figure 1 of DI1, the board holds that, even if they were considered to be unclear, they would only raise questions concerning the type of connection between the modems and the diplexers but not the fact that the modems are coupled to the diplexers. The bidirectional arrows do therefore not affect the overall disclosure of DI1 as far as it is the basis for the above conclusions.

1.4 The board therefore concludes that claim 1 of the main request lacks novelty having regard to DI1 and that the main request is thus not allowable under Article 54 EPC.

2. First auxiliary request - novelty (Article 54 EPC)

2.1 Claim 1 of the first auxiliary request differs from claim 1 of the main request in that it further specifies that each "frequency multiplexer" is a "single frequency diplexer".

2.2 According to the skilled reader's common general knowledge, a "diplexer" is understood as a device which couples a first port via a first filter to a second port and via a second filter to a third port, both filters having a different frequency response in order to achieve frequency multiplexing. The board notes in this respect that the frequency-dependent coupling between the data transmission line and the low- and the high-frequency modems respectively is already specified in features 11) and 12) of claim 1 of the main request.

2.3 Blocks 3/3a, 4/4a and 6/6a, as shown in Figure 1 of DI1, provide the effect of a frequency-dependent coupling of the signals on the data transmission line either to the low-speed modem or to the high-speed modem (see point 1.1 above). Thus, blocks 3, 4 and 6 form together a functional entity that indeed provides the function of a single diplexer. The same applies for blocks 3a, 4a, and 6a. Hence, diplexers 3 and 6 of DI1 correspond to the "topside frequency multiplexer" as claimed, while diplexers 3a and 6a correspond to the "subsea frequency multiplexer" as claimed. As a consequence, DI1 in fact teaches that the frequency multiplexers are formed by single diplexers in accordance with present claim 1.

2.4 The proprietor argued that DI1 disclosed several diplexers and that elements 4 and 6 in DI1 could not be understood as forming a single diplexer, since otherwise a diplexer would be coupled to another diplexer ("diplexer 3") resulting in an element with four interfaces whereas a typical diplexer element only comprised three interfaces.

2.5 The board is not persuaded. Using the above understanding of the term "diplexer" (cf. point 2.2 above), elements 3 and 6 of DI1 are not diplexers, at least for the simple reason that they do not provide paths with different frequency responses. Rather, the skilled person would understand that a "diplexer" in the above sense requires the combination of elements 4 and 6 and that the capacitors provide a high-pass filter for element 6.

2.6 The board therefore concludes that the subject-matter of claim 1 of the first auxiliary request is not new having regard to DI1 and that the first auxiliary request is thus also not allowable under Article 54 EPC.

3. Second auxiliary request - inventive step (Article 56 EPC)

3.1 Claim 1 of the second auxiliary request further specifies that, on the subsea side, there are multiple low-frequency modems and multiple high-frequency modems. The low-frequency modem are arranged in a "multi-drop configuration" and the high-frequency modems are arranged in a "point-to-point configuration" by means of an "access multiplier".

3.2 Document DI1 is undisputedly the most suitable starting point for assessing inventive step as regards present claim 1. It already addresses the upgrading or extension of an existing subsea well complex (page 4, lines 7 and 8).

The claimed system differs from the system of DI1 essentially in features 13) to 16) (see point V above), i.e. in that (board's emphasis)

(i) multiple subsea low- and high-frequency modems are provided;

(ii) the subsea low-frequency modems implement a multidrop communication scheme;

(iii) the subsea distribution module comprises an access multiplier adapted to enable a point-to-point communication between the topside high-frequency modem and the subsea high-frequency modems.

As to the understanding of the terms recited in the distinguishing features, the proprietor stated that a "point-to-point communication" was an end-to-end communication and that, in the "multidrop communication scheme", all subsea modems were supposed to receive a message but only one had to respond. Furthermore, the claimed access multiplier was to be understood as some sort of router.

3.3 The technical effect resulting from those distinguishing features was extensively discussed during the oral proceedings before the board. In that regard, from the patent specification itself, it could merely be derived that an access multiplier "may itself act as a modem on each of its interfaces" (cf. paragraph [0057]) and that data communications between the topside high-frequency modem and each of the subsea high-frequency modems "may occur without the use of an access multiplier 41, e.g. by using other communications schemes, such as a multidrop scheme". Hence, it could be inferred from that teaching that multidrop and point-to-point communication schemes for high-frequency communications correspond to equally likely alternatives, the selection of which depends on the practical constraints.

3.4 In the proprietor's favour, the board adopts the objective technical problem as framed by the proprietor at the oral proceedings, namely "how to find an efficient way to update the subsea communication system of DI1 with new components having different frequency and bandwidth characteristics".

3.5 The board holds that the mere use of a multidrop configuration in the low-frequency range and of a point-to-point configuration with an access multiplier in the high-frequency range does not yield a synergistic technical effect that goes beyond the individual effects arising from a juxtaposition of said specific configurations. Taking further into account that, in the system of DI1, the data communications over the two frequency ranges do not causally affect each other (see e.g. abstract), the problem of upgrading the system of DI1 can thus be treated independently for both available frequency ranges.

3.6 For upgrading the data communication scheme in the high-frequency range according to the above objective problem, the person skilled in the field of subsea data communication systems would have consulted prior-art document DI7 which also addresses the problem of upgrading the communication schemes of existing subsea fields (cf. page 3, section 3.3, first paragraph: "Extensions and changes to existing subsea installations"). DI7 discloses, for this purpose, a "LongSpeed powerline modem" that enables a

point-to-point topology at a data rate of 33,6 kbit/s (page 5, first ten lines of the section entitled "LongSpeed powerline modem"). The "LongSpeed" modem can coexist on the same power-pair with powerline modems called "PLMS160" with a lower data rate of 2,4 kbit/s. The "LongSpeed" modem can therefore be regarded as a

high-frequency modem. In addition, each subsea module has space for two "LongSpeed" modems (page 5, last paragraph). Moreover, the communication protocol used in the "new communication systems", which also refers to the "LongSpeed" system, is TCP/IP that implies a router or, in other words, an access multiplier as claimed.

As regards the low-frequency modem, DI1 discloses a typical data rate of 1,2 kbit/s. This very low data rate implies the use of legacy equipment, like for example the "Bell 202 modem" which operates at this data rate. This equipment had become an early standard in subsea communications and is also mentioned in the opposed patent itself (see paragraph [0004]). At the priority date of the opposed patent, it was, however, common general knowledge to connect multiple

low-frequency modems according to a multidrop communication scheme. It was likewise known that a multidrop communication scheme was very simply implemented by connecting the modems in parallel or in series. Its drawback, namely that all connected modems have typically to share the overall system data rate, is evidently alleviated by the use of high-frequency modems in a point-to-point configuration as known from DI7, and would not have deterred the skilled person from adopting the multidrop configuration for the

low-frequency modems.

3.7 In conclusion, the skilled person would, starting out from DI1 and applying the teaching of DI7, have arrived at a system according to present claim 1, without exercising any inventive skills.

3.8 The proprietor argued that upgrading an existing system is costly and the skilled person would have replaced the whole system if new components were added.

However, DI1 already discloses that, in the case of upgrading an existing subsea system, the low-speed system remains in place and may continue to operate alongside the added high-speed system (page 4, lines 5 to 8). This argument is therefore moot.

3.9 Furthermore, the proprietor submitted that neither DI1 nor other documents on file provided a hint towards the use of different communication schemes over the different frequency ranges. As regards the use of the point-to-point configuration for the high-frequency modems, the proprietor merely stated that, in the

high-frequency range, a multidrop configuration could not be easily implemented and that a point-to-point scheme like TCP/IP was generally better.

The board however finds that no synergistic effect can credibly be derived from merely having two different communication schemes and that DI1 is silent as to the communication scheme to be deployed in each frequency range. Hence, the skilled person would have been expected to take a decision as to the communication scheme for each frequency range separately. There was no reason preventing the skilled person from implementing different communication schemes. In the mentioned case, in which an existing system including only a low-frequency modem is upgraded (page 4, lines 5 to 8), the skilled person would have indeed considered different communication schemes for the high-frequency modems independently of the existing communication scheme applied in the low-frequency range.

3.10 In view of the above, the board concludes that claim 1 of the second auxiliary request lacks an inventive step, having regard to documents DI1 and DI7. The second auxiliary request is therefore not allowable under Article 56 EPC.

4. As there is no allowable set of claims, it follows that the patent is to be revoked.