Time and Phase Synchronization in Telecom Applications



Meinberg LANTIME NTP servers have been designed to fulfill the synchronization requirements of modern 4G/LTE networks. A LANTIME time server is capable to act as a Primary Reference Time Clock (PRTC) and, because of its unmatched flexibility, can be deployed in different scenarios. The modularity of the IMS platform (Intelligent Modular System) allows the LANTIME to be configured for all areas of a mobile backhaul network: in the core, metro or access levels.

Depending on the installed modules and the selected synchronization sources, a rackmount or rail mounted LANTIME time server can play different roles. By supporting multiple input sources utilizing Meinberg‘s IRSA (Intelligent Reference Switching Algorithm) technology, the LANTIME accepts GPS, GLONASS, Galileo, BeiDou, PTP, NTP, SyncE, 1PPS or E1/T1 as possible synchronization inputs to be able to act as an Edge Grandmaster Clock. IRSA is useful to bridge potential GNSS outages or, if desired, to completely avoid the availability of the GNSS signals. A highly stable oscillator ensures a holdover period of several hours or days (depending on the target application), even if no synchronization source is available anymore. Using an external PRC allows to extend the holdover capabilities to the required level at a certain point in the network.

The PTP implementation supports both ITU-T profiles, ITU-T G.8265.1 for frequency and ITU-T G.8275.1 for frequency and phase. This allows to provide accurate frequency and phase synchronization over packet networks to all network elements requiring synchronization, including 2G/3G/4G base stations as well as LTE advanced networks. A LANTIME system can act as a Telecom Grandmaster for thousands of clients.

For NTP-based synchronization, each of the PTP module network interfaces of a LANTIME IMS system can be configured to act as a carrier grade NTP server with 8 ns time stamp accuracy, serving up to 400,000 NTP requests per second on each port.

The modular approach of the IMS platform allows field-replacement and hot-swap capabilities for IO modules and power supplies. This concept ensures future-flexibility and expandability by allowing to add or replace modules when new technologies or interfaces are required and makes this product one of the most scalable and flexible synchronization solution on the market.


PTP Telecom Profile for Frequency Synchronization

Source: Meinberg Blog - The PTP Telecom Profile for Frequency Synchronization by Doug Arnold

The Precision Time Protocol Telecom Profile for Frequency Synchronization was created by the International Telecommunication Union, or ITU, for transferring precise frequency through a packet switched network which does not have any support for PTP. Don’t let the name fool you though, you can transfer time as well as frequency with this profile.

The IEEE 1588 PTP Telecom Profile for Frequency Synchronization is developed for telecommunications, but has been used in other systems as well, for example power grids, which have traditionally made use of telecom network technology to connect all the sub-stations to the monitoring and control centers.

Why does the title indicate only frequency transfer when it could be used for time transfer? The answer is that the ITU committee which specified the profile realized that the ability to transfer time with an accuracy in the order of 1 us, is limited when the switches and routers do not have PTP support. Typically, time transfer accuracy on the order of 1us can be achieved through about five busy routers/managed switches when these devices lack PTP support, i.e. they are not boundary clocks or transparent clocks. Some typical telecom applications are shown below. Some typical telecom applications are described in our blog News and Tutorials - The PTP Telecom Profile for Frequency Synchronization.

The details of the profile are described in the document G.8265.1, which is available at the agreeable price of free from the ITU. The profile uses exclusively the PTP unicast mode and end to end delay measurement. All messages are sent as UDP/IP packets. The only allowed device types are ordinary clocks which are either always slaves or always masters. For many telecom applications they would rather get a fault condition than allow one of the slaves to try to synchronize the network. The allowed values of the message rates are shown in our Blog News and Tutorials.

Meinberg Systems for Telecom Applications

The M1000 provides ITU-T G.8265.1 for frequency and ITU-T G.8275.1 for frequency and phase

The M1000 provides ITU-T G.8265.1 for frequency and ITU-T G.8275.1 for frequency and phase

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NTP server and PTP Grandmaster with 8 ns time stamp accuracy, serving up to 400,000 NTP requests per second.

NTP server and PTP Grandmaster with 8 ns time stamp accuracy, serving up to 400,000 NTP requests per second.

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