Syntonization and synchronization: essential for all mobile networks--especially LTE

As operators migrate to LTE and LTE-Advanced, mobile backhaul synchronization becomes more important than ever.

In 2G and 3G networks, mobile operators were able to syntonize base stations from native TDM networks. The nature of the backhaul network provided an easy source of timing. Today these mobile networks have grown, and most of the traffic is carried over Ethernet.

Syntonization and synchronization defined
Syntonization is the alignment of clocks to the same frequency. Syntonization enables base stations to stay within their allocated spectrum and avoid interfering with other cells.

Synchronization is the alignment of clocks to a common instant. There are 2 different components in synchronization: phase alignment and time-of-day information:

  • Clocks that tick at exactly the same moment, are said to be phase aligned.
  • Phase synchronous clocks may also have a common epoch or time origin. This is called time of day synchronization. Clocks tick at the same speed, in the same phase, and all clocks are aware of the time and date information.

Synchronization and Syntonization in Mobile Networks
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Migration to more efficient and higher capacity mobile networks
In some cases the legacy TDM network still provides syntonization. But in more and more cases operators are replacing TDM lines with synchronous Ethernet and packet clocks using IEEE1588v2. Both SyncE and IEEE1588v2 are additions to the data network, and provide syntonization (timing) as a service to the mobile networks. Backhaul networks already require syntonization, and as this trend is continuing to include synchronization.

LTE is evolving to meet the ever increasing demand for mobile data. Some applications require accurate synchronization to better than 1 microsecond.

Some examples of these applications are LTE-TDD (Time Division Duplex) mode and Coordinated MultiPoint (CoMP). LTE-TDD shares the same frequency for uplink and downlink transmissions, and the switch between uplink and downlink needs to occur at a common instant across the network.

Synchronization also enables location-based services. If a network's base stations are synchronized well, operators can better locate a mobile phone geographically in their network--which could be life-saving in the case of emergency calls.

Operators need cost-efficient, accurate synchronization
How can thousands of base stations across the country be kept in sync to within a fraction of a microsecond in a cost-efficient way?

That is one of the questions that I address our new white paper, LTE Stretches Synchronization to New Limits. The paper explores how to migrate smoothly to IEEE 1588v2-based syntonization and how to support phase synchronization once final standards emerge.

Tellabs sees the backhaul network playing a major role in providing synchronization to future mobile networks. The cost and difficulty of requiring GPS on every cell-site makes synchronization distribution via Ethernet backhaul very attractive—even more so with the increase in the number of cell sites in dense deployments. Synchronization is truly becoming a service of the transport network—starting on the edge and working into the core.

Also, take a look at the new enhancements we've made to the Tellabs® 8600 Managed Edge System. As part of our Mobile Backhaul solution, Tellabs 8600 system simplifies the evolution to LTE and LTE-Advanced networks, including multiple built-in synchronization and syntonization schemes for LTE.