Today’s mobile network operators face a more challenging set of decisions than ever before.
For many years, frequency synchronization delivered by TDM-based technologies was sufficient for the timing demands of mobile networks. Then came the evolution to packet- and Ethernet-based networks, which required additional features, such as the ability to transport timing information in packets.
Now, however, rapid increases in demand coupled with several new features within the mobile standard mean that frequency alignment alone is no longer enough to keep networks in sync. Now phase and time-of-day synchronization is also required to take spectrum utilization to new levels and leverage the full capabilities of the 4G environment as well as upcoming 5G applications.
But, while there’s wide-spread agreement that mobile networks require adjacent cells to be aligned in absolute time and phase, the question is: What’s the most efficient and future-proof way to achieve this?
Two paths to cell site synchronization
Standards bodies working together with technology suppliers and operators have been looking at different ways to deliver highly accurate time and phase synchronization. Currently there are two established routes to providing the timing information that cell sites need.
Option one is to install an individual Global Navigation Satellite System (GNSS) antenna at every cell site. This is a simple solution in terms of design and, if environments are consistent, it can ensure the necessary time accuracy. But, while it’s certainly cheap to deploy GNSS-based synchronization on an individual installation basis, it presents major cost challenge when scaling it to thousands of cell sites.
This approach also runs into difficulties where there is no clear view of satellites. What’s more, solutions relying on GNSS-based synchronization alone are vulnerable to accidental events, such as lightning strikes or satellite constellation operational problems, or deliberate interference such as jamming or spoofing attacks.
The second option is network-based timing. This offers a very cost effective alternative to, as well as a complimentary option for GNSS-based timing. For indoor small cells this solution is the only one that can work since it is not possible to connect every indoor small cell to the GNSS.
One advantage of this method is that the same solution is utilized throughout the network and so it’s naturally consistent. It’s resilient as it uses various sources and locations to provide synchronization. Scalability is another strength as new features can be rolled out easily across the simplified network as well as any fixes required as technologies change. With network-based timing, smaller sites are also protected by the higher levels of security in the network and site security problems of GNSS solutions in specific locations are removed.
The other key consideration is monitoring and assurance and this is another reason why network-based timing could be crucial. Deploying a solution that continually monitors network feeds for a real-time view of the entire synchronization network can dramatically reduce faults and expense. Operators may also consider monitoring strategic points in the network in order to take preventative action if potential issues occur.
Best of both worlds
For many operators, a combination of GNSS and network back-up feeds will be optimal. Getting the balance right to ensure required levels of time integrity along with cost efficiency and scale is the challenge.
The only certainties are that demand is growing rapidly and continuously and the requirements of 4G and 5G mean that timing is more critical than ever. Whichever way they choose to turn, operators need to decide on a course of action sooner rather than later.
To find out more about delivering precise, reliable and cost-effective synchronization to align frequency, phase and time of day in mobile networks, please check out this new white paper that we developed with BT. Click here to download it.