Insights High Court finds that defendants had not infringed telecoms packet switching patent and that the patent was not essential



In this FRAND case, the claimants (Mitsubishi Electric Corporation and Sisvel International SA) sought to persuade the defendants, Oneplus Technology (Shenzhen) Co Ltd and others, to take FRAND licences of a pool of patents (the Pool) administered by Sisvel, which were alleged to be essential to one or more telecoms standards.

This first technical trial concerned a European Patent, entitled “Radio Link Control (RLC) Unacknowledged Mode (UM) Header Optimization” (the Patent) owned by Sisvel. The Patent was written in the context of the Universal Mobile Telecommunication System (UMTS) standard, but Sisvel claimed that it was essential to the Long-Term Evolution standard (LTE).

Sisvel said that the defendants, without a FRAND licence from Sisvel, had infringed the Patent.

The defendants denied essentiality, thereby denying infringement.

In line with its title, the Patent defines the field of the invention as relating to optimizing RLC UM PDU headers, for example, to better support packet switched voice transmissions or transmission of other real time packet switched services over Wideband CDMA air interface.

According to the specification, the problem the Patent is addressing is the situation where the one or more complete Service Data Units (SDUs) are two octets (or “bytes”) smaller than the Protocol Data Units, i.e. the units into which the SDUs need to be packaged for onward transmission to the Medium Access Control (MAC).

The consequence of the invention is that all the information required by the receiver to unpack and process the data in the PDU is contained in that PDU and none is missing.

Claim 1 describes the method as 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” (emphasis added).

The claimants’ said that the defendants’ use of the 2-bit FI=00 value when inserted into the Framing Indicator field in the PDU header, as in a basic structure of an RLC PDU in LTE, infringed the Patent because:

  1. the 2-bit FI=00 value is a “length indicator” on the proper construction of that term in claim 1 of the Patent since it 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. In other words, it has all the characteristics of what a skilled person would understand by a “length indicator” in claim 1;
  2. in the alternative, if the FI=00 did not infringe on a normal interpretation, they alleged that the FI=00 value infringed on the basis of Actavis

The case therefore turned on the meaning and scope of the term “length indicator” in claim 1.


Mr Justice Mellor noted that, because the purpose of a PDU is to carry SDU payload, when an RLC PDU arrives at the relevant level of the receiver, the receiver needs to know how the various SDUs or SDU segments are packed in the PDU or PDUs, so that it can separate out each SDU and send each one for further processing in the next layer. In the context of the Patent, such information was conveyed in various ways:

  1. ordinary length indicators, which indicate the position in the PDU of the final octet of a particular SDU;
  2. special length indicators, which indicated more elaborate information than that conveyed by an ordinary length indicator depending on the configuration of the values (e.g. FI=00); and
  • information that can be conveyed by the alternative E-bit (which was introduced into the UMTS standard in 2005), which indicates both start and end information of an SDU.

Mellor J found that the term “indicator” or even “structure indicator” in the context of an RLC UM PDU header in UMTS would be sufficiently general to cover ordinary length indicators, special length indicators and the alternative E-bit. This showed that the term “length indicator” was used in claim 1 to exclude the alternative E-bit, there being no other words in the claim which could perform that role.

Accordingly, Mellor J said, to fall within the term “length indicator” in the Patent, the field in question must be capable of specifying the position in the RLC PDU where an SDU ends. If the field in question is not so capable, then it is not a “length indicator”. The alternative E-bit and the FI=00 value only provide structure information and are not capable of specifying the position in the PDU where the SDU ends. Therefore, Mellor J found, neither the alternative E-bit nor the FI=00 value in LTE is a length indicator within the meaning of claim 1. Accordingly, there was no infringement on a normal interpretation of claim 1.

As for the Actavis questions, Mellor J said that the answer to all three, was “no”: (i) the invention achieved the result by using a “length indicator” and the FI=00 value achieved the same result in a different way because it was not a “length indicator”; (ii) the skilled person would immediately understand that the variant was not a “length indicator” and that the use of the FI=00 value was a different way of achieving the result; and (iii) the skilled person reading the Patent at the priority date would conclude that the patentee was using the term “length indicator” to exclude the alternative E-bit from the scope of the claim and therefore that the normal interpretation of “length indicator” was an essential requirement of the invention. Accordingly, there was no infringement on the basis of equivalents.

Mellor J concluded by saying that the term “length indicator” was used in claim 1 as granted to exclude the alternative E-bit, in order to avoid Samsung prior art, amongst other reasons. Although the alleged infringement, the FI=00 value, was not identical to the alternative E-bit, it had considerable similarities. In particular, neither was capable of acting as an ordinary length indicator. Accordingly, if “length indicator” was construed so as to exclude the alternative E-bit, it also had to exclude the FI=00 from the scope of the claim, whether on a normal interpretation or on the basis of equivalents.

The Patent was not infringed and was also not essential to LTE. (Mitsubishi Electric Corporation v Oneplus Technology (Shenzhen) Co Ltd [2021] EWHC 1048 (Pat) (26 April 2021) — to read the judgment in full, click here).