of a new Ethernet-based technology which ensures sub-nanosecond synchronization and deterministic data transfer. The project uses an open-source paradigm for the development of its hardware and software components (https://www.ohwr.org/projects/ white-rabbit/wiki/). Synchronous Ethernet is an ITU-T standard for computer networking that facilitates the transfer of clock sig- nals over the Ethernet physical layer. This signal can then be made traceable to an external clock. 5G Network Architecture 75 CPRI Transport The CPRI is an industry forum defining a publicly available specification for the interface between a radio equipment control (REC) and a radio equipment (RE) in wireless networks. CPRI specifies a digitized serial interface between a base station referred to as REC in CPRI terminology and an RRH or RE. The specifications cover the user- plane, the control-plane transport mechanisms, as well as the synchronization schemes. The specification supports both electrical and optical interfaces as well as point-to-point, star, ring, daisy-chain topologies. The CPRI interface provides a physical connection for I/Q samples transport as well as radio unit management, control signaling, and synchronization such as clock frequency and timing synchronization [75]. CPRI transports I/Q samples to/from a particular antenna port and RF carrier. This is called an antenna-carrier (AxC) and is the amount of digital baseband (I/Q) user-plane data neces- sary for either reception or transmission of only one carrier at one independent antenna ele- ment. An AxC group is an aggregation of multiple AxC streams with the same sample rate, the same sample width, and the same destination. An AxC container consists of a number of AxCs and is a part of a basic CPRI frame (see Fig. 1.28). Data is organized into basic frames of 16 words. The first word of each basic frame is the control word. Each word can be 8, 16, or 32 bits, depending on the width of the I/Q samples. The width of the word depends on the CPRI line rate. For example, in