Anything But Convergence in Backhaul Synchronization

Rather than consolidating, approaches to synchronization of Ethernet backhaul from cell sites are proliferating

October 30, 2008

3 Min Read
Anything But Convergence in Backhaul Synchronization

Recent Ericsson AB (Nasdaq: ERIC) data shows that, on average, total traffic on its W-CDMA networks worldwide increased threefold in the 12 months to July 2008. Within that, on average, total data traffic increased fourfold, and total HSPA traffic increased sixfold. Amidst trends like that, there are indicators of cellular operators finally starting to commit to deploying Ethernet-based backhaul in volume to support these new traffic volumes more flexibly and at lower cost.

One of the biggest challenges in implementing Ethernet backhaul is introducing a new timing or synchronization solution. This is particularly true in the case of the GSM and W-CDMA standards, which rely on recovering timing from the present-day T1/E1 backhaul network. Replace that altogether with an Ethernet backhaul pipe, and you need an alternative form of synchronization or else the quality of the user experience of real-time service like voice is liable to deteriorate.

Some operators like BT Group plc (NYSE: BT; London: BTA) are yet to commit to any of the new standards. The Ethernet backhaul service that it is currently rolling out to the U.K.'s cellular operators over fiber still relies on leaving an E1 at the cell site for synchronization. This has the advantage of relying on a tried and trusted approach that all the customers for its Ethernet backhaul service – currently Vodafone UK , Telefónica UK Ltd. , T-Mobile (UK) , and Hutchison 3G UK Ltd. – can be equally confident will protect the quality of their basic voice service.

Where cellular operators are building out their own Ethernet backhaul, rather than relying on a third-party transport provider, the number of approaches to synchronization continues to proliferate. Some new deployments are still featuring proprietary adaptive clock recovery solutions, and this will continue to be reflected in upcoming announcements. The standards-based approaches are starting to see greater traction now, though.

For example, a reliable source from outside the vendor community relays that the Brilliant Telecommunications Inc. implementation of the IEEE 1588v2 standard in Vodafone Portugal is performing very well, paving the way for the operator to turn up Ethernet-over-fiber supporting voice and data service to several hundred cell sites in Oporto and Lisbon within the next six months. Symmetricom Inc. (Nasdaq: SYMM) and Nokia Networks also recently demonstrated interoperability between their 1588v2-compliant reference clock and base station implementations.

Alcatel-Lucent (NYSE: ALU) and Cisco Systems Inc. (Nasdaq: CSCO) recently launched new backhaul-focused cell site aggregation routers. Both vendors are committed to supporting multiple synchronization standards but made great play of early support for Synchronous Ethernet. In the CDMA world, of course, operators are able to leverage the timing capabilities of GPS. And some vendors continue to bring their own solutions to market.

One interesting implication of the Vodafone Portugal implementation is that it is being deployed in an Ericsson radio network. This suggests that within Vodafone, Ericsson may not be seeing as much traction as it would like for its own single-vendor RAN synchronization solution, which is based on an implementation of the Network Timing Protocol (NTP) standard. In the Ethernet-over-copper product category, Hatteras Networks Inc. has just introduced its own approach to hardening the timing capability of its cellular backhaul solution with its branded "Big Flexible Pipe" technology.

As I've forecasted in my "Ethernet Backhaul Quarterly Market Tracker," over time the bulk of the market will likely move to the two primary standards-based approaches: IEEE 1588v2 and Synchronous Ethernet. But in the meantime, expect diversity to continue. And with that, expect costs to remain unavoidably higher than they might be – be it the cost to vendors in terms of additional development spend to meet the diversity of operator requirements, or the opex cost to some operators where they make architectural choices that maintain E1s or T1s at the cell site for synchronization rather than moving to a pure Ethernet backhaul. Over time, early leaders in Ethernet synchronization solutions such as RAD Data Communications Ltd. and Tellabs Inc. (Nasdaq: TLAB; Frankfurt: BTLA) will also have the challenge of proving that their adaptive clock recovery implementations can indeed be upgraded to a standards-based solution with minimal cost.

— Patrick Donegan, Senior Analyst, Wireless, Heavy Reading

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