DECT-2020 NR Conformance testing: Testing for MAC layer

Abstract

Before placing any products on the EU market, a manufacturer must ensure that its products comply with essential requirements. To ensure that a product complies with its requirements, a conformity assessment is carried out, where the product is tested according to the methods or against the requirements defined in the related standards. This thesis concentrates on testing of a radio protocol standard. The reason why testing for radio equipment is done in the first place is for the final product to get real use in the world. The requirements for radio equipment in the European economic area come from the Radio Equipment Directive which regulates the use of radio devices and their marketing. The EU supports its members to fulfil the objectives of the directive by providing harmonised standards. Secondly, testing should also be done to conform with the relevant requirements specified in the standard specifications. These specifications provide detailed rules and procedures on how the radio devices implementing the standard should communicate and behave. Having a common standard as a baseline for all implementations raises the quality, and most importantly enables the interoperability of implementations between manufacturers. The technology for which the testing in this thesis is intended is the DECT-2020 NR radio technology, designed for massive-scale IoT having applications such as smart metering, lightning etc, capable of being implemented by utilizing its mesh operation mode. On the physical layer, the DECT-2020 NR is a CP-OFDM-based non-cellular radio technology operating on the 1900 MHz licence-exempt band originally intended for the use of the legacy DECT, by co-existing with it by deploying autonomous spectrum sensing capabilities for interference avoidance. This thesis tested a product implementation of DECT-2020 NR according to the test methods defined in the ETSI EN 301 406-2 harmonised standard. The thesis shows what kind of results shall be obtained for a product to conform with the requirements of the harmonised standard and thus with the related requirement of the directive. The testing was focused on the channel access tests in a random-access manner, where the functionality is provided by the MAC protocol layer. At the time of writing this thesis, the harmonised standard has not yet been referenced in the official journal of the European Union. However, ETSI released the harmonised standard under the Radio Equipment Directive in August 2023, meaning that listing to the OJEU will happen in the near future, after which it is allowed to be used as a direct proof of compliance with the directive. Before this, a notified body may always perform the conformity assessment. As the DECT-2020 NR radio technology is a relatively new standard, there are no standardised test specifications available. In this thesis, an initial set of test purposes for the use of the conformance specification were defined. The test purposes were derived directly from the core specification focusing on the MAC layer procedures. In addition to defining test purposes, this thesis also showed examples of proving conformity with the standard by using packet captures acquired from system simulations and inspecting them by using a network protocol analysing tool, where the message sequences and their internal bit content could be inspected for defining a test verdict. As another option, physical test setups using RF measurement equipment were used for the purpose of conformance testing, although found to be usable only for a limited set of features. In conclusion, the thesis has turned out to be a study of standardised and regulatory testing of a new radio technology which is still under development, while showing examples of how the testing for an early implementation may be done.