Standard-essential patent
A patent you cannot avoid if you want to implement a given technical standard — and therefore worth far more than the invention it describes.
When ETSI, the IEEE or the ITU settles a standard such as LTE, wifi or HEVC, it rests on inventions somebody has patented. Anyone building a compatible phone has no choice in the matter. The owner declares the patent essential and promises to license it on FRAND terms. Whether a patent really is essential is rarely tested; declarations are self-assessed, and studies have found that a large share do not hold up on closer inspection.
Outside telecoms things move even less smoothly. Video codecs are licensed through patent pools, and HEVC fragmented across several competing ones — part of the reason AV1 was built as a royalty-free alternative. In Huawei v. ZTE (2015) the EU Court of Justice set rules for when an SEP holder may seek an injunction. The European Commission's 2023 proposal for an SEP regulation was withdrawn in 2025.