Finger Pointing in Backhaul

As a vulnerable spot in the network, avoiding backhaul issues can eliminate the finger pointing.

It's like a sprained ankle that just won't heal. Whether delivered via microwave or fiber, voice and data traffic back to the main switch - otherwise known as back-haul - remains the primary cause of outages in wireless networks.

Backhaul failings crop up often, and often fall into a no-man's land of finger pointing and lack of accountability. For starters, many providers lease rather than own that portion of the network. And even when a provider does operate its own microwave or fiber ring, maintaining those systems still is not a core part of the company's business.

"The backbone is still viewed as a sore spot in the network when you're talking about outages," said Don Coover, V-Comm vice president, which provides network engineering services. "There's been a lack of control in that part of the network, combined with rapid industry growth. You build something you think is going to last the next 24 months, and then you run out of capacity."

Much of the trouble is inherent in a business that rushed to build out capacity without paying much heed to network redundancy and repair time.

"The original cellular providers needed to turn networks up as fast as possible, and everything was point to point, which is not very fault tolerant," Coover said.

And although the evolution of SONET rings and the practice of leasing private networks have helped, they bring baggage of their own.

"Having a private microwave network has added a layer of complexity for the operator folks," Coover said. "They are already maintaining a switch and a base station, and now they have to maintain the transmission backbone and manage the capacity of that backbone."

Despite backhaul's bad reputation, help is available today, and more is on the way. Service providers large and small are beginning to implement a host of fault-management solutions that can obliterate, if not compensate for, trouble on the line.

Much of the compensatory equipment and software is concentrated in the T1 environment, home to a potential Pandora's box of issues for traffic traveling back to the main switch. One way to increase reliability is to simplify the system by cutting back on the number of T1 lines in use, a concept that also jibes with providers' recent realization they need to pare down network costs.

Bayly Communications sells equipment that consolidates traffic from multiple partially-used T1s into one full-capacity line. It can cut down the number of lines a provider uses by half and dramatically reduce backhaul network costs, according to Brian Sherk, Bayly sales manager.

The equipment also incorporates a performance monitoring capability that enables providers to observe their T1 links in real time, a benefit Sherk said has contributed to a steady rise in sales during the past 12 months.

"The operator can pro-actively look for a degrading T1 that might cause an outage and get to it before it wipes the network out," he said.

AirNet Communications offers another way to reduce the number of T1s via an integrated point-to-multipoint radio system housed within the base-station infrastructure. Use of the Air-Net packet-radio equipment also typically saves a provider 70% to 80% in T1 costs, according to Bennet Wong, director of technical sales.

The product has garnered some 15 communications clients during the three years it has been available in the United States, and it's now making a play for the international market, according to Wong, who said it is gaining one contract a month internationally. To make it more attractive, AirNet recently integrated billing functions.

Even the most streamlined system can't always beat mother nature. Lightning and other foul weather are formidable enemies of traffic traveling back to the switching center, particularly in the rural and suburban areas where so many wireless providers are looking to expand. In these areas, the practice of daisy-chaining - or stringing a single T1 line over up to 24 remote cell sites to cover a broader area - is common, leaving the network particularly vulnerable.

ADC Telecommunications has been conducting field trials of its new CrossPATH Max modular box, which enables wireless companies to protect their circuits without laying down a fully redundant network. CrossPATH lets providers set parameters whereby the modules will reconfigure - automatically or manually, depending on the provider's needs - should an outage occur. The product is slated to ship commercially this month.

"Companies are trying to reach rural areas more and more, and this is really going to help in those areas as well as with the growing home office market," said Larry Singletary, ADC Access Products Division senior marketing manager.

In metropolitan areas where new applications quickly swallow up bandwidth, ADC's Smart ByPass offers a way to ensure critical traffic still gets through in the event of a network outage. Providers can program prebit mapping to recognize traffic such as CDPD or billing calls, which within seconds of an outage will reroute through an available T1.

"Carriers can designate whatever traffic they want," Singletary said. "It is pure backhaul, so it's not independent of particular data. It provides not only circuit protection but application protection for real time."

Whither 3G? Still muddled in its present condition, backhaul complications are poised to be magnified in the IP-based environment. Increased data applications coupled with more subscribers spending more time on a mobile network likely will put even minor blips under a microscope.

"We come up against a real challenge in moving to 3G because in the past we were talking about penetration in the range of 10% to 20%," AirNet's Wong said. "Now in the United States, we are moving into the 40% range and internationally the 60% to 70% range. For operators, it could prove to be a big financial strain if they have to put in completely new infrastructure as they have in the past."

To be sure, just because a provider offers 3G services does not mean it will do away with current handsets and subscribers. Because most will stick with 2G handsets for at least a portion of their service area, finding a solution that seamlessly addresses legacy infrastructure as well as future network operations is the chief concern of wireless providers' engineering teams.

"There's already a lot of investment in infrastructure, whether it's physical stations or towers and associated leases," V-Comm's Coover said. "You're going to see a lot of people trying to model out capabilities of 3G."

"You're really going to see a relook at network architecture as it exists today and a migration to other backbone capabilities. Most prevalent will be some sort of IP, probably an ATM network for backbone transport."

While all eyes are on mobile Internet applications, ADC's Singletary warns that Web-based network management is not a foregone conclusion for 3G.

"We are keeping it in mind, but Web-based is probably not going to be a viable solution because you could obsolete it before the network is even built," he said.