As 5G begins to be deployed in earnest, it is plain to see that it is much more than a simple upgrade to the current 4G mobile networks. The three fundamental pillars of 5G; eMBB (Enhanced Mobile Broadband), MMTC (Massive Machine Type Communications) and URLLC (Ultra Reliable Low Latency Communications) clearly emphasises the importance of Massive IoT and Critical IoT into the overall 5G mix. Furthermore, 5G FWA (Fixed Wireless Access) and 5G as a transport network technology in the backhaul is also being deployed.
The introduction of 5G represents not just a new radio network infrastructure but also a significant change and investment to the core network. This is now based upon a Service Based Architecture incorporating NFV (Network Functions Virtualization) and SDN (Software Defined Network) technology to drive down the total cost of ownership and to drastically improve network utilization and system elasticity. These benefits are not solely confined to mobile networks and as such, could also be incorporated by the fixed network or wireline service providers. Thus, the 3GPP along with the Broadband Forum and CableLabs have developed a number of standards which support wireline access into the 5G core network. This is illustrated in Figure 1.
Figure 1 Wireline Access in 5G (5G RG)
The 5G RG (5G Residential Gateway) provides the connection between the networked equipment within a home or small office to the 5G core network and then on to a DN (Data Network) such as the Internet. Interestingly, the 5G RG could support both a wireless interface (Uu), similar to a FWA deployment and the wireline interface (Y4) towards the 5G core via the W-AGF (Wireline – Access Gateway Function). It is this which supports the standard 3GPP reference points N2 and N3 towards the AMF (Access and Mobility management Function) and UPF (User Plane Function) respectively in much the same way as a 5G base station or gNB. However, the 5G RG also supports the 3GPP N1 reference point which is used to pass NAS (Non Access Stratum) signalling between it and the AMF.
Therefore, before any data can be transferred across the wireline network, the 5G RG must first register with the AMF and trigger the establishment of a PDU Session. This may contain a number of QoS Flows to support the broad range of services that may wish to utilize this connection – IPTV, Voice, Internet and IoT etc. Furthermore, Network Slicing can also be supported across the wireline network. Thus, in the case of streaming video, the data will flow from the video server connected to the Data Network via the N6 reference point to the UPF. From here, it will be tunnelled to the W-AGF via the N3 reference point using the protocol GTP (GPRS Tunnelling Protocol) and finally across the wireline connection (Y4) to the 5G RG which in turn may transfer the information to the television using ethernet or Wi-Fi within the home network.
In addition to the 5G RG, an alternative endpoint has also been defined termed the FN RG (Fixed Network Residential Gateway). This operates in a similar way to the 5G RG however it does not support the 3GPP N1 reference point. As such, the W-AGF would need to deal with the NAS signalling on its behalf. This is illustrated in Figure 2
Figure 2 Wireline Access in 5G (FN RG)
Therefore with the introduction of wireline access in 5G, service providers will be able to offer a truly converged service over both the radio and fixed broadband / cable access networks.