It can be very confusing to work out which ITU-T synchronisation standards apply to which types of network deployment. Since the current generation of synchronisation standardisation started in 2004, the ITU-T has produced 24 separate synchronisation standards. These standards are primarily aimed at enabling the operation of the mobile telecommunications network, by providing synchronisation to the mobile basestations over a packet-based transport network.
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- Standards aimed at delivering accurate frequency, to better than 50ppb
Main use case: 2G, 3G and 4G cellular mobile radio using Frequency Division Duplexing, FDD
Methods include:- Physical layer synchronisation using Synchronous Ethernet (SyncE)
- Packet-based synchronisation using Precision Time Protocol (PTP)
- Standards aimed at delivering accurate time and phase, to better than 1.5us
Main use case: 3G, 4G and 4G 5G cellular mobile radio using Time Division Duplexing, TDD
Methods include:- Combined PTP/SyncE, using boundary clocks (BCs) or transparent clocks (TCs) at every node in the network (full timing support, FTS)
- Combined GNSS and PTP, operating over existing networks, where not all the nodes in the network contain BCs or TCs (assisted partial timing support, APTS)
- PTP alone, operating over existing networks, where not all the nodes in the network contain BCs or TCs (partial timing support, PTS)
- Standards aimed at delivering very accurate time and phase , for use in fronthaul (e.g. with relative Time Error better than 260ns or 130ns)
Main use case: 5G cellular mobile radio using co-operative processing techniques (e.g., Carrier Aggregation, Coordinated multipoint trans-mission/reception (CoMP)), typically used in fronthaul. Support for positioning.
Methods include:- Combined PTP/enhanced SyncE, using boundary clocks (BCs) or transparent clocks (TCs) at every node in the network (full timing support, FTS)
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