IEEE Std 802.1CM-2018 pdf download – Local and metropolitan area networks- Time- Sensitive Networking for Fronthaul.
Fronthaul network requirements depend on the air interface supported by the BS and on the BS functional decomposition. This clause: Provides background information on aspects of the Evolved Universal Terrestrial Radio Access (E-UTRA) (3GPP TS 36.211 [B3]) technology supported by fronthaul standards that are closely related to this standard (6.1). Provides background information on the Common Public Radio Interface Specification [B4] (6.2). Defines Class 1 and describes Class 1 requirements (6.2), where the BS functional decomposition is according to the Common Public Radio Interface Specification [B4]. Provides background information on the eCPRI Interface Specification [B5] (6.3). Defines Class 2 and describes Class 2 requirements (6.3), where the BS functional decomposition is according to the eCPRI Interface Specification [B5]. 一 Describes time and frequency synchronization requirements (6.4) common to both Class 1 and Class 2. Clause 8 specifies bridge profiles and fronthaul bridged network design considerations that support the Class1 (6.2) and Class 2 (6.3) requirements. Clause 9 describes the applicability of synchronization methods (7.4) to the synchronization requirements (6.4).
6.1 Evolved Universal Terrestrial Radio Access background The Evolved Universal Terrestrial Radio Access (E-UTRA) specifications (e.g, 3GPP TS 36.211 [B3]) define precise time intervals for data transmission. E-UTRA time intervals are defined as multiples of the basic time unit: T。= 1/(15000 x 2048) s. E-UTRA uses Orthogonal Frequency Division Multiplexing (OFDM) where an OFDM symbol is the smallest element of an E-UTRA frame. The OF DM symbol time to carry data is 2048 x Ts. In addition, the full OFDM symbol time includes the time of the cyclic prefix (Tcp). In case of normal cyclic prefix, Tcp = 160 x Ts for the first symbol and Tcp= 144 x Ts for the following six symbols. In case of extended cyclic prefix, Tcp = 512 x Ts for each symbol. The timing of packet transmission at an eRE/RE and an eREC/REC in a fronthaul interface supporting E-UTRA is related to the OFDM symbol times explained above. NOTE一Frame refers to Ethernet frame in this document. OFDM frame refers to the OFDM frame structure (see 3GPP TS 36.211 [B3]). 6.2 Class 1 requirements Class 1 refers to fronthaul interfaces where the functional decomposition of an E-UTRA BS (see 3GPP TS 36.104 [B1]) jinto RE and REC is according to Common Public Radio Interface Specification V7.0 [B4] (Table lA),”7 and the different CPRI information flows are supported separately from each other by the fronthaul bridged network as described in 6.2.2. In the case of Class 1, RE and REC are connected by a bridged network as described in Clause 8.18 This subclause describes Class 1 and its requirements, which are explained in 6.2.3 and 6.2.4.