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UK – Mitsubishi Electric Corporation v. Oneplus Technology

22 Jul 2021

Mitsubishi Electric Corporation and others v. Oneplus Technology (Shenzhen) Co Ltd and others, 26 April 2021, Case No. [2021] EWHC 1048 (Pat)

In this judgment of the Patents Court, Mellor J dismissed the infringement claim of the Claimants in the first technical trial in these proceedings, holding that the declared standard essential patent in issue was not essential and was not infringed.

Mitsubishi Electric Corporation (“Mitsubishi”) and Sisvel International SA (“Sisvel”) (together the “Claimants”) brought infringement proceedings against multiple parties in relation to a pool (“the MCP Pool”) of their standard essential patents (“SEPs”), including entities in the OnePlus/Oppo and Xiaomi groups of companies (the “Defendants”). This trial was the first technical trial in the FRAND licence dispute relating the MCP Pool of SEPs.

The SEP in issue, owned and declared to be essential by Sisvel, was EP 1,925,142 (“EP142”). The Claimants alleged that EP142 is essential to version 10.0.0 and all subsequent versions of TS36.322 of the 4th generation 3GPP Long-Term Evolution (“LTE/4G”) standard for wireless broadband communication for mobile devices.

The Defendants denied essentiality, thereby denying infringement, but also ran a series of squeeze arguments to the effect that if EP142 were essential to the LTE/4G standard, the it would be invalid on several grounds (although Mellor J ultimately decided that there was no need to deal with the invalidity arguments in his judgment).

Continuing a recent trend in the Patents Court, Mellor J had ordered the parties to produce a statement of agreed CGK (and included much of that document in his judgment).

The Claims
Claim 1 of EP142 as granted reads as follows:

A method comprising: inserting, in a radio link control, RLC, entity, at least one service data unit, SDU, to a protocol data unit, PDU, of an appropriate size; characterized in that it further comprises: providing at least one indicator including a length indicator for indicating that a first data octet of the protocol data unit, PDU, is a first octet of a first service data unit and at least one other octet of the protocol data unit, PDU, is the last octet of another service data unit, the first service data unit being either the same or different from the other service data unit, wherein the at least one other octet is the last octet of the protocol data unit, PDU.

The case turned on the meaning and scope of the term “length indicator” in this claim.

The alleged infringement
Mellor J started by summarising that “[a]lthough it is well established that the alleged infringement cannot be allowed to influence the interpretation of the claims in the Patent, in the circumstances of this case it is instructive to have the alleged infringement in mind in order to detect whether the alleged infringement is illegitimately influencing the arguments on claim scope”.

The approach taken to Radio Link Control (“RLC”) Protocol Data Units (“PDUs”) in LTE has a number of similarities but also some differences to the approach taken in the Universal Mobile Telecommunication System (“UMTS”) (the latter being a third generation (“3G”) cellular communication system). The most significant difference of all is that in LTE there is no constraint of a set of fixed PDU sizes for a given session. Instead, LTE uses fully flexible PDUs such that every PDU can be shrink fitted to the Service Data Units (“SDU”) payload.

The other differences and similarities are best illustrated by reference to one of the basic structures of an RLC PDU in LTE in which a 5-bit sequence number is used. In the Unacknowledged Mode Data (“UMD”) of the RLC, the PDU header (the so called “first octet”) starts with the 2-bit Framing Indicator (“FI”) field, followed by a single E-bit, and a 5-bit Sequence Number (“SN”). In the optional part of the header there then follows pairs of a single E-bit with a 11-bit Length Indicator (“LI”). Because each LI is longer than 8 bits, each LI occupies more than one octet and if there are an odd number of LIs, 4 bits of padding must be included at the end of the header, as illustrated. Thus, the only use of padding in LTE is at the end of the header. Padding is never needed at the end of the data payload, because the PDU is automatically fitted to the payload, which is always a whole number of octets.

The Claimants’ infringement case relied on the FI=00 value when inserted into the FI field. The Claimants alleged that:

i) The FI=00 value is a length indicator on the proper construction of that term in claim 1 of EP’142. The case is advanced on the basis that the FI=00 value is an element in the PDU header that provides control information describing the payload, which allows the receiving entity to separate the RLC SDUs contained in the data part of the PDU (the judge’s emphasis). Thus, the Claimants alleged, it has all the characteristics of what a Skilled Person would understand by a ‘length indicator’ in claim 1.

ii) In the alternative, if the FI=00 does not infringe on a normal interpretation, the Claimants allege that the Actavis questions ([2017] UKSC 48) must be answered: 1: yes; 2: yes; and 3: no, so the FI=00 value infringes on the basis of equivalents.


Normal Construction

The key issue was the meaning of “length indicator” in claim 1, in relation to which the judge commented that both parties’ contentions were “quite elaborate”.

The judge explained that the Claimants needed the term ‘length indicator’ (which includes both (1) ordinary length indicators and (2) the special length indicators of EP142) to exclude (3) the single alternative E-bit but include (4) the 2-bit value FI=00. All four provide structure information about the SDU(s) in the PDU or, to use the Claimants’ phrase ‘control information about the payload’. The distinguishing feature of (3) and (4) is that they only provide structure information and are not capable of directly acting as length indicators in the traditional sense of specifying the position in the PDU where an SDU ends. Hence, neither the alternative E-bit (when set to 0 in the first octet) nor the field FI=00 in LTE is a length indicator within the meaning of claim 1 of EP142.

Accordingly, the judge found that there was no infringement on a normal interpretation of claim 1 of EP142.


Mellor J set out the key questions in Actavis; the Claimants requiring them to be answered (i) yes; (ii) yes; and (iii) no:

i. Does the variant achieve substantially the same result in substantially the same way as the invention, i.e. the inventive concept revealed by the patent?

ii. Would it be obvious to the skilled person, reading the patent at the priority date, that the variant achieved the same result in substantially the same way as the invention?

iii. Would the skilled person have understood that the patentee nonetheless intended strict compliance with the literal meaning of the claims as an essential requirement of the invention?

On (i), the judge held the answer to be “no”. The variant (i.e. when the FI field is set to 00) achieves the same result in a different way because it is not a length indicator.

Similarly, the judge held that the answer to (ii) was also “no”. It would not have been obvious that the variant achieves the same result in substantially the same way, because the Skilled Person would immediately understand that the variant is not a length indicator. The Skilled Person would also understand that the use of the FI=00 value is a different way of achieving the result.

Finally, the judge held the answer to (iii) to be yes, for the same reason again. The Skilled Person would have concluded that the patentee used the term “a length indicator” to exclude the alternative E-bit from the scope of the claim and therefore what the judge had found to be the normal interpretation of “a length indicator” was an essential requirement of the invention.

The judge noted that the answers to all three Actavis questions depended on the normal interpretation of “length indicator”, but found that this did not indicate any error in the approach. Even if he had found the first two questions to yield positive answers, he noted that in the circumstances of this case, question 3 would still require the answer “Yes”.

Accordingly, EP142 was found not to be infringed on the basis of the doctrine of equivalents.

The Claimants’ claim for infringement failed and accordingly EP142 was held not be essential to the LTE/4G standard. The alleged infringement fell outside the scope of claim 1 of EP142, whether on a normal interpretation or on the basis of the doctrine of equivalents.

The full judgment can be accessed here.

Headnote and summary: Adam Mackinnon and Amy Crouch, Simmons & Simmons LLP