l be ensured. Integrity protection of software transfer towards the small cell shall be ensured. The base station software update shall be verified before its installation (subclause 4.2.3.3.5 of TS 33.117). For the application use-case of industrial communication networks (private 5G), International Electrotechnical Commission (IEC) standards 62443 covers security aspects and should be used as a guideline at the system level, both for technical and process related aspects. In addition, IEC 63074 guides use of IEC 62443 with regards to functional safety. References 1. https://insideevs.com/news/376037/tesla-mcu-emmc-memory-issue/. 2. https://xenomai.org/. 3. https://www.enea.com/products/operating-systems/real-time-accelerated-linux/. 4. https://github.com/LITMUS-RT/cyclictest. 5. Varghese, G.; Lauck, A. Hashed and hierarchical timing wheels: efficient data structures for implementing a timer facility. IEEE/ACM Trans. Netw. 1997, 5 (6). 6. http://lwn.net/Articles/374424/ (Huge pages). 7. https://www.6wind.com/6windgate/. 8. https://en.wikipedia.org/wiki/Vector_Packet_Processing. 9. Osterbo, O.; Grondalen, O. Benefits of self-organizing networks (SON) for mobile operators. J. Computer Netw. Commun. 2012, 2012. 10. http://www.whitehats.nl. Further reading SCF. 5G FAPI: PHY API Specification, https://www.smallcellforum.org/5g-phy-api-release/ CPRI. eCPRI Specification v2.0. 'Common Public Radio Interface: eCPRI Interface Specification' May 2 2019. ETSI. NR; Base Station (BS) radio transmission and reception, 3GPP TS 38.104. ETSI. NR; Multiplexing and channel coding, 3GPP TS 38.212. ETSI. NR; Physical channels and modulation, 3GPP TS 38.211. ETSI. NR; Physical layer measurements, 3GPP TS 38.215. ETSI. NR; Physical layer procedures for control, 3GPP TS 38.213. ETSI. NR; Physical layer procedures for data, 3GPP TS 38.214. ETSI. NR; Requirements for support of radio resource management, 3GPP TS 38.133. User-plane application components This chapter outlines the key application components in the CU, DU and radio unit (RU