n described the CPRI and eCPRI interfaces, which are commonly used to convey user data to the RF/antenna component (often referred to as RRH or RRU) and the Iuant, AISG, and other interfaces that are used to control the antenna. We then discussed that the "monolithic" architecture proved to be too limiting to cater to all relevant deployment scenarios. To this end, 3GPP (and other SDOs and industry fora) studied various functional splits, some of which have been standardized and are described in the following sections of this chapter. 4.1.6 Further Reading Most of the topics mentioned in this section are described in more detail in the book. However, there are some detailed descriptions of what (beyond what appears in the present section) was considered out of scope, specifically: CPRI and eCPRI Antenna interfaces. Readers interested in more detailed description of the former should consider reading the relevant specifications provided by CPRI - CPRI v7.0 and eCPRI v2.0. Readers interested in historical perspective about standardization activities related to fronthaul interfaces may consider reading ETSI ORI and OBSAI specifications. For details about antenna interfaces, refer to Iuant 3GPP specifications (3GPP TS 37.460 and TS 37.466) and AISG specifications (AISG v3.0, AISG ST-RET and AISG ST-TMA). References 3GPP Technical Report 25.802 (2004). Remote control of electrical tilting antennas. Available at: www.3gpp.org (accessed May 29, 2020). 3GPP Technical Report 28.540 (2019). Management and orchestration; 5G Network Resource Model (NRM); Stage 1. Available at: www.3gpp.org (accessed May 29, 2020). 3GPP Technical Report 28.541 (2019). Management and orchestration; 5G Network Resource Model (NRM); Stage 2 and stage 3. Availake at: www.3gpp.org (accessed May 29, 2020). 3GPP Technical Specification 23.501 (2019). System architecture for the 5G System (5GS). Available at: www.3gpp.org (accessed May 29, 2020). 3GPP Technical Specification 23.502 (2019). .Procedures for the 5G System (5GS). Available at: www.3gpp.o