Samsung v ZTE: 5G synchronisation patent survives obviousness and collocation attack

The Patents Court has upheld the validity of a Samsung patent essential to the 5G standard, finding that a proposal circulated to standards delegates a fortnight before the priority date fell short of rendering the claimed invention obvious, and that criticism of an expert's reasoning, rather than any legal principle, decided the case.

In Samsung Electronics Co Ltd v ZTE Corporation [2026] EWHC 2235 (Pat), handed down on 28 August 2026 following a trial in March, Mr Justice Mellor dismissed ZTE's counterclaim for revocation of EP(UK) 3,934,154, which concerns the design of the synchronisation signal block used by handsets to locate and lock onto a 5G cell during initial access. Essentiality and infringement were admitted, so validity was the sole issue, argued on three fronts: obviousness over a 3GPP discussion document known as LG 434, an allegation that the claim was an impermissible collocation of two independent ideas, and a contention that it made no genuine technical contribution.

Identifying the skilled person proved pivotal

Before reaching invalidity, the judgement resolved a dispute over the notional skilled person. ZTE's expert proposed someone closely tied to the RAN1 standards working group and its published agreements; Samsung's expert proposed a broader physical layer engineer developing implementation building blocks ahead of finalisation. Applying the established field approach from Illumina Cambridge v Latvia MGI Tech [2021] EWHC 57 (Pat) and its application in Nokia v Oneplus [2023] EWHC 23 (Pat), the judge found the real dispute lay less in the skillset than in the scope of common general knowledge each side's expert brought to the CGK dispute, and proceeded on the RAN1-based expert's evidence, giving ZTE the more favourable starting point.

Even so, the obviousness case failed. LG 434 had proposed, conditionally, using an additional signal for the dual purpose of demodulating the broadcast channel and indicating a block index, an idea the judge accepted the skilled reader would regard as worth pursuing. But the further steps said to lead to the claim, including interleaving a self-contained reference signal into the broadcast channel and giving it a wider bandwidth than the synchronisation signals, rested on reasoning the judge found unconvincing and, in places, technically incorrect. A comparison drawn with reference signalling in 4G networks was accepted by the expert under cross-examination to be inapt once its true operation was explored, and an argument that combining signals must mathematically increase bandwidth was similarly conceded to be wrong.

Hindsight featured prominently. The judge noted that the expert knew, before instruction, precisely how the eventual 5G standard had resolved every element of the claim, yet his evidence gave no indication that this had been factored into his approach, contrary to the guidance in Fisher & Paykel v Flexicare [2020] EWHC 3282 (Pat) that an expert already familiar with an invention must identify how and when that knowledge arose and discipline themselves against its influence. Combined with the absence of sufficiently reasoned justification for several individual steps, the cumulative effect fell short of establishing obviousness, even on evenly balanced facts.

Collocation and technical contribution rejected together

ZTE's fallback case sought to split the claim into a bandwidth and multiplexing feature and a separate indexing feature, attacking each independently under the principle in SABAF v MFI Furniture Centres [2004] UKHL 45 that integers performing their functions independently cannot be rescued from obviousness by mere juxtaposition. The judge held the two could not be prised apart: the reference signal in the claim performs a genuinely dual role, demodulating the broadcast channel while also carrying the sequence that indicates the block index, so that the nature of the signal required by one part of the claim is shaped by the requirement in another. That was enough to treat the claim as a single invention.

The technical contribution challenge, run by reference to Takeda v Roche [2019] RPC 18, was rejected on a similarly short footing: since the claim survived as one invention essential to the 5G standard, dissecting individual integers for separate technical justification was the wrong exercise. The patent was declared valid, essential and infringed.