Wireless backhaul's intelligence injection

ETHERNET ALSO TAKES ADVANTAGE of IP policies for creating different classes of service. This can be particularly appealing in a wireless broadband environment in which carriers might want to prioritize voice and an increasing amount of video traffic over other data traffic and less-latency sensitive applications that can be classified as best-effort.

“With broadband, you'll have all kinds of traffic converging at various base stations, and with Ethernet, you'll have an easier time aggregating all of that traffic,” Allen said.

Industry observers have noted that through all the technology upgrades in mobile access networks over the years — from analog to digital to 2G, 2.5G and now 3G, there have not been corresponding upgrades in backhaul technology. As traffic has grown, mobile carriers simply have leased more T-1s. Part of the reason they have continued to rely on TDM-based T-1s is because that is primarily what wireline telcos have made available to them, but as the major carriers are beginning to expand their availability of Ethernet services, that could be about to change, according to ABI's Arden.

“ILECs are starting to migrate to Ethernet services, and they also want to use Ethernet technology across their networks because of the cost savings and efficiency they'll get,” he said. “That's the driver for the ILECs [supplying the backhaul capacity] to change technologies.”

Arden added that in 2005, about three-quarters of the $10 billion in revenue total ILECs derived from backhaul came leases of TDM-based T-1s, but by 2011, only one-third of the projected $18 billion revenue will come from that source.

“Various Ethernet-based solutions will be replacing those T-1s,” Arden said. “It will be Ethernet over copper or Ethernet over fiber, and to a lesser extent, wireless and microwave radio.”

Regardless of the physical infrastructure involved, Ethernet seems to be the common goal among vendors with backhaul solutions. Michael O'Malley, group manager of portfolio marketing for Tellabs, said that most cell sites in 2G mobile networks have about five to seven T-1 connections each for backhaul capacity. Shields of GeoResults agreed with that numbers and said his research shows that average will grow to almost nine T-1s per cell site by 2010.

“You generally can count on adding a couple of T-1s per site for 2.5G services, and then, when you get to 3G, you want to look at adding more or migrating to something like Ethernet or Gigabit Ethernet,” O'Malley said.

Dave Stehlin, CEO of Ceterus Networks, a vendor of circuit-bonding solutions, added, “Every carrier has their own traffic engineering models that tell them when they are going to need to increase backhaul capacity. Right now, many of them need about 5 Mb/s to 7 Mb/s, and after that, you'll want to enable Ethernet out to those sites.”

O'Malley also cautioned that the 3G market is still in such an early phase that neither backhaul bandwidth requirements, nor the usage of T-1s to supply capacity are likely to change overnight.

“All the carriers right now are taking a close look at their engineering models,” he said. “We still don't yet really know what the adoption rate of 3G services will be, so the real need for Ethernet backhaul could be a couple of years away.”

For that reason, Dan Murray, vice president of marketing for Kentrox, said the transition is likely to characterized by the use of many different types of backhaul solutions in a single network environment and also by the employment bonded T-1s, pseudowires and the multilink point-to-point protocol to allow the merging of ATM and IP traffic into a single broad pipe.

“When you look at backhaul, it's going to be a bit of a hybrid world, and that transition is going to occur at the threshold of 8 Mb/s to 10 Mb/s,” he said. “Carriers will need to invest strategically.”