in- terfaces as proprietary. 5G introduced new features, increased performance, and a need for more flexible deployment scen- arios, which requires an improved specification for CPRI. In August 2017, CPRI published the first version of the enhanced CPRI specification, known as eCPRI, with several advantages: Tenfold reduction in the front-haul interface bandwidth Statistical multiplexing benefits Support of packet-based transport such as Ethernet Support for real-time user applications using sophisticated coordination algorithms to guarantee radio performance Provision to add new functionality by software updates In May 2019, CPRI released eCPRI version 2.0, a specification to support legacy CPRI (version 7.0) over Ethernet, allowing for CPRI and eCPRI interworking. Chapter 10 covers CPRI and eCPRI in some detail. The eCPRI specifications became a foundation for many alliances wishing to define open packet- based front-haul interfaces for 5G deployments. The move toward open specifications makes it easier for operators to mix and match vendor equipment and accelerate innovation in their 5G RAN networks. 4.6.1 xRAN and O-RAN Alliance The xRAN Forum was formed in 2016 with the goal of developing, standardizing, and promoting a software-based extensible RAN (xRAN). The xRAN Forum gained tremendous industry mo- mentum with leadership from operators AT&T, Deutsche Telecom, KDDI, NTT DOCOMO, SK Telecom, Telstra, and Verizon. At the same time, the xRAN Forum has added contributing members from suppliers, innovators, and research leaders including Intel, Texas Instruments, Mavenir, Cisco, Altiostar, Fujitsu, NEC, leading universities, and SO forth. Researchers from this grouping focused on three areas: Decoupling the RAN control plane from the user plane Building a modular base station software stack that uses COTS hardware Publishing open northbound and southbound interfaces On April 12, 2018, the xRAN Forum released its first specification, "xRAN front-haul Specification version 1.0," dedicated to virtualizing the fron