C_ID PC_ID RTC ID SEQ_ID SEQ_ID SEQ_ID User data IQ samples (1st octet) User data bit sequence (1st octet) Real-time control data (1st octet) User data IQ samples (Lth octet) User data bit sequence (Lth octet) Real-time control data (Lth octet) Bit sequence transfer message Real time control data message IQ data transfer message format format format Figure 1.34 eCPRI user-plane message formats [76]. information flow are out of the scope of the eCPRI specification. This flexibility implies that there is additional work required to realize multi-vendor interoperable solutions. IEEE 1914.3 Radio-Over-Ethernet Transport As we mentioned earlier, the TSN has been designed to ensure timely transport of delay-sensitive packetized streams such as CPRI-over- Ethernet; however, it does not deal with the encapsulation of various fronthaul transport pay- loads. RoE is a standard for radio transport over Ethernet including specification of encapsula- tions and mappings developed by IEEE 1914.3 working group. 46 It enables transport data over Ethernet (i.e., native RoE packet mapper) as well as support of structure-aware and structure-agnostic mappers for CPRI and other data formats. The work targeted among others definition of a native RoE encapsulation and mapper transport format for both digitized radio payload (I/Q data) and management and control data. The Ethernet packet format itself is not changed and neither is the MAC protocol, as shown in Fig. 1.35. The RoE defines a native encapsulation header format for transporting time-sensitive radio data and control information. The definition of protocol primitives allows multiplexing of independent streams, for example, antenna and carriers; time stamping or sequence number- ing to enable time synchronization of RoE packets and timing alignment of the streams; control protocol for auxiliary non-data streams and for link and RoE endpoint management; and mapper(s) for existing CPRI framing standards to a native RoE encapsulation and trans- port. There is also focus on enabling 