As 5G introduces new concepts & new network architectures that will have a deep impact on core, transport and radio network design, how will synchronisation be affected? More than half of the Communication Services Providers surveyed at Mobile World Congress this year said they were in the early stages of rolling out 5G, so timing & synchronisation options should be at the centre of architecture discussions now! In the same survey respondents said the most important requirement in switch/router hardware was "quality 5G timing & synchronisation".
5G's RAN functional decomposition brings some of the philosophies of NFV & SDN to 5G and its use of CPRI/eCPRI to fronthaul data brings its own synchronisation challenges, with IEEE & ITU liaisons looking at timing aspects of this part of the network. Time Alignment Errors proposed in the new 3GPP specifications for 5G are in some cases many orders of magnitude smaller than current requirements, with 65ns being the tightest requirement. (It is worth noting however that some of the most stringent tolerances are intra-node only, not transport/network wide requirements.) Many operators are still in the process of moving from frequency-only sync to providing time & phase sync distribution for existing 4G/LTE-A services.