Insights High Court finds two telecoms patents essential to LTE standard and valid



In this FRAND case, the claimants (Mitsubishi Electric Corporation and Sisvel International SA) are seeking 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 are alleged to be essential to one or more telecoms standards.

The first technical trial, on which we reported in April 2021, concerned a European Patent, entitled “Radio Link Control Unacknowledged Mode Header Optimization” owned by Sisvel. Mr Justice Mellor found that that patent was not infringed and was also not essential to LTE.

This second technical trial concerned another two European Patents in the Pool, this time in relation to the use of pilot signals to request uplink resources in a telecoms network and the transfer of the signals to a telecoms device. One is the parent of the other and they both have the same title: “Method and device for transferring signals representative of a pilot symbol pattern”.

Only Claim 1, which also features the wording of the patent titles, was relevant to this technical trial. Claim 1 of the parent patent relates to the use of information based on pilot symbols/signals to indicate the need (or not) for uplink resources. Claim 1 of the progeny patent relates to the use of pilot symbols/signals to request uplink resources.

In this technical trial, Mellor J had to decide whether: (i) the patents were essential to the aspect of Release 8 of the LTE (4G) technical standard concerned with transmission of a scheduling request (SR) to request uplink resources; (ii) the patents were invalid for obviousness over the prior art; and (iii) the parent patent was invalid for added matter. A trial to consider the relief claimed by the claimants, which will include a determination of the FRAND terms for licensing the Pool, is set to be heard in October 2021.



Mellor J agreed with the claimants that the term “pilot symbol” bore the ordinary meaning of a pilot or reference signal i.e., a pre-defined signal known to both transmitter and receiver. It was not a mere request message, as argued by the defendants, nor should it be understood as referring to something used not only as a request for uplink resources but also for its conventional purpose of channel quality determination. There was no hint at all in the Claims to “channel quality pilot”, therefore “pilot symbol” was not being used in any special sense, but simply in its ordinary sense of a pilot or reference signal.

Mellor J also noted at this point in the judgment that, whereas, traditionally, reference or pilot signals did not convey information from higher layers in a telecoms network system, the new use proposed in the patents was that reference signals were used to convey information from higher layers: specifically, a need for uplink resources.

As for the “not need” element in Claim 1 of the parent patent, Mellor J found that, as the claimants argued, it could be indicated by silence.


The question was whether Claims 1 were essential to the functionality of the aspect of Release 8 LTE standard concerned with the transmission by the User Equipment (UE) of a SR by signals on the PUCCH channel (Physical Uplink Control Channel, which carries only uplink control signalling), known as PUCCH format 1, PUCCH format 1a and PUCCH format 1b. These PUCCH formats are used to convey the different control information types or combinations of types and are sent by the UE on a resource known as sr-PUCCH. The claimants said that they were essential.

In his judgment, Mellor J provided a comprehensive analysis of the LTE standard. He then went on to consider the parties’ arguments.

Mellor J noted that there was no dispute as to how the signals in question were constructed or transmitted. The issue concerned the correct characterisation of various parts of these signals. Mellor J explained that each of the PUCCH format 1/1a/1b signals is made up of DeModulation Reference Signals (DMRS) and PUCCH data symbols.

The defendants relied on the language used in the LTE standard and (i) the way in which it describes the DMRS separately from the PUCCH; and (ii) that it states that it is the PUCCH, not the pilot signal/symbol that signals the SR.

The claimants said that the language on which the defendants relied was loose and that one had to look at the signal that the specification in the patents said must be sent (e.g., signal X), and if signal X was in fact a signal of the type required by the Claims, then the fact that the standard might describe signal X differently was irrelevant. In essence, the claimants’ case was that a positive SR is signalled by the presence of a PUCCH format 1, 1a or 1b signal on its assigned sr-PUCCH resource. Conversely, the absence of a signal on that resource indicates a negative SR. The claimants said that the whole of a PUCCH format 1/1a/1b signal is a pilot symbol/signal or comprises such a signal.

Mellor J agreed with the claimants, finding that the defendants were wrong to say that the DMRS was separate to, and not “part of”, the PUCCH format 1/1a/1b signal. The defendants had also mixed up the PUCCH itself with the actual signal by which an SR is transmitted on the PUCCH. Mellor J said that it is the presence or absence of a PUCCH format 1/1a/1b signal on the assigned sr-PUCCH resource that indicates a positive or negative SR. Therefore, splitting the PUCCH format 1/1a/1b signals into separate signals was incorrect. For example, Mellor J said, the standard specifies that a particular form of signal is sent to request uplink resources. It is either a PUCCH format 1 signal or a PUCCH format 1a/1b. Those are the signals that are required to be sent in order to signal a SR. In either case, it was clear that the signal comprises both the PUCCH data symbols and the DMRS and it was artificial and wrong to isolate one part of the signal from its other constituent parts.

Considering LTE, in particular the PUCCH channel and the different PUCCH formats, Mellor J found that signalling SR by a PUCCH format 1, 1a or 1b signal, which he had found did constitute pilot symbols/signals, on the sr-PUCCH resource satisfied Claim 1 of the progeny patent. Equally, the presence or absence of a PUCCH format 1, 1a or 1b signal on that resource indicated a need or no need for uplink resources, and so Claim 1 of the parent patent was also satisfied. Therefore, if valid, both patents were essential to the LTE standard.


The prior art, called Kwon, cited by the defendants was a 3GPP Working Group 1 TDoc entitled “Uplink scheduling procedure”. It was submitted by Samsung to RAN WG1 meeting 43 held in Seoul in November 2005. The document was a proposal for an uplink scheduling procedure for LTE.

Mellor J said that contrary to the defendants’ arguments, the pilot accompanying the step (1) message in Kwon did not indicate a need for resources. It was the data in the step (1) message which conveyed the mobile’s need for resources, not the accompanying pilot signal, which was there simply to enable the request to be decoded and understood. The pilot signal described in the patents, however, conveyed the mobile’s need for resources. Accordingly, the validity attack based on Kwon failed.

Added matter

The defendants argued that the new information in the parent patent as granted was the concept of transmitting a positive signal indicating that the mobile did not need an uplink resource. They said that this new information was contained within Claim 1 of the parent patent as granted.

Mellor J had already found in favour of the claimants in relation to the construction of Claim 1, finding that the Claim covers a mobile that does not need uplink resources, indicating so by silence, i.e., via a signal with a power set to null. Accordingly, on the question of added matter, the defendants’ argument also failed.


Claim 1 of each of the patents was therefore valid and essential to the LTE standard. (Mitsubishi Electric Corporation v Oneplus Technology (Shenzhen) Co Ltd [EWHC] 1639 (Pat) (16 June 2021) — to read the judgment in full, click here).