21581 - SCTE Broadband August2022 COMPLETE v1

59 Vol. 44 No. 3 - September 2022 Issue technical n The ability to implement separate quality of service levels for specific applications over a single physical network (network slicing) These new technologies require testing to ensure the network can meet end user demands— and all of this must be achieved while supporting existing 4G and legacy infrastructure. In this white paper we will provide an overview of these technologies and their role in implementing a 5G network. The evolution from 4G to 5G At the end of December 2017, the 3GPP standards body approved an interim set of specifications for 5G networks focused on implementing enhanced mobile broadband (eMBB) features. This interim specification defined 5G new radio (5G NR) and a way of leveraging the existing 4G network to provide improved bandwidth and slightly improved latency. This 5G non- standalone (NSA) architecture allows a 5G NR to use 5G for radio to handset communication (downlink or DL) while relying on existing 4G communication for the handset to radio-head uplink (or UL) communication. eMBB features are the first that will be offered through 5G networks. The 5G NSA architecture will be followed by 5G standalone (SA), the architecture that will enable ultra low latency (uRLLC) and massive machine to machine communication (mMTC) applications. As shown in figure 2, this release will support the full core—supporting 5G on the UL and DL as well as providing even further improvements in latency and device connectivity. During the roll-out of 4G networks we witnessed the migration of the radio access network (RAN) architecture into a distributed radio access network (D-RAN) where copper co-axial cables were replaced by optical fibres—referred to as fibre-to-the- antenna (FTTA). This transformation implemented a split of the radio elements,—generally referred to as the remote radio head (RRH),—and the baseband functions, generally referred to as the baseband unit (BBU). These were connected together with one of two competing digital RF communication protocols: common public radio interface (CPRI) and open base station architecture initiative (OBSAI). These elements are typically referred to as fronthaul technology (see figure 3). This split of RRH and BBU functionality also allowed the grouping of several BBUs, from multiple cell sites, into a single location to save on infrastructure costs, creating a centralised RAN (C-RAN) architecture. 5G introduces a further split of the radio access architecture into three, rather than two elements. These are called the centralised unit (CU), the distributed unit (DU) and the radio unit (RU). The network designer can decide where to place network functionality within these building blocks to meet specific network requirements, such as latency and throughput (as seen in figure 4). The presence of the DU introduces a new network element between the DU and the CU, referred to as the midhaul. Together the backhaul, midhaul and fronthaul networks are referred to as the xhaul. Figure 2: 5G NSA to 5G SA migration