GPS/GNSS independent Time Transfer over Telco IP Core Networks using DTM overlay

Abstract

A major part of the 5G evolution is meeting the required phase and frequency demands. Networks based on time division duplex (TDD) and C-RAN and in the future, other techniques require accurate phase and frequency synchronization.Operators are trying to design networks capable of delivering these demands. To prepare 5G base stations requires very high accuracy on clocking, to a maximum of 1.5 microseconds.With these requirements, the use of PTP (Precision Time Protocol) for phase and time distribution was developed by IEEE (1588 and 1588v2).To meet the requirements for 5G, full timing support (FTS) using G.8275.1 is recommended, meaning all network elements in the network need to be upgraded or replaced. This can be a huge cost for an operator since current Telco Networks still have large portions of legacy equipment. Turk Telekom has also realized, this is not only applicable for the IP/MPLS routers, but also requires underlying optical nodes such as DWMD multiplexers to support PTP and not introduce jitter and asymmetric delays. Thus, significant investments would need to be made to meet the requirements of having full timing support in all nodes.Due to these required huge CAPEX investments, we have developed and tested a new approach that requires only a fraction of the CAPEX needed. Our approach to solving this critical issue for our 5G rollout will be to create a synchronization network overlay using a DTM layer over IP/MPLS networks which we have tested successfully on our live WAN IP/MPLS network without using any additional timing support. We call this Time Transfer overlay solution a Precise Timing Network.