Vendors get creative to face the challenges of mobile data and streaming

With customer use of data services on the rise, mobile operators face potential bottlenecks in their backhaul networks. Base station manufacturers have increased capacity, but the best approach to backhaul remains a matter of debate — and the answer may differ, depending on a wireless operator’s specific circumstances.

Complicating matters further are concerns about how best to handle latency-sensitive streaming traffic, particularly high-bandwidth video traffic. Another worry is that, although the majority of base station interfaces are TDM, operators now are looking to ease the eventual transition to 4G services by demanding equipment that also will support Ethernet.

“The big carriers are making sure they can take Ethernet into a cell site,” said Jim Orr, principal network architect for Fujitsu, who argued that migration to Ethernet also lets operators optimize their networks for streaming traffic.

“In a well-designed network, Ethernet can handle streaming better than T-1,” Orr said. A good design involves running Ethernet over Sonet to ensure that the network has plenty of capacity available. “The bigger the pipe, the better the performance,” he said.

Big pipes handle traffic peaks better because T-1 links are narrower and require more traffic shaping. “Any time you have to traffic shape and queue, you introduce delay,” Orr said. “The smaller the pipe, the smaller statistical pieces you have to manage.”
But not every cell site is reached by fiber. That’s why Atkino is betting carriers will be interested in a DSL-based solution that offers more bandwidth than traditional DSL-based offerings.

“Over 90% of cell sites in North America are fed by copper,” said Hossam Salib, senior vice president and co-founder of Atkino. “Primarily they’re still T-1 or DSL. There’s been a slow migration to Ethernet. We have products that provide both interfaces, but 90% are still TDM.”

Atkino’s solution relies on four to eight bonded copper pairs. To support the increase in streaming traffic, which tends to flow downstream, the company has added an asymmetric version of its product. “At 12,000 feet with 24-gauge copper in a binder, our asymmetrical offering can provide up to 7 Mb/s in the downstream direction,” Salib said.

Exalt Communications, meanwhile, is hoping that as backhaul capacity needs increase, some operators still will demand a microwave solution. The company offers high-capacity microwave backhaul equipment with an emphasis on flexibility.

“We have all TDM circuits natively in the product as well as IP,” said Amir Zoufonoun, founder and CEO of Exalt. “We have two pipes and they’re equal; the diameter is variable and under software control.”

Through remote downloads, operators will be able to upgrade capacity, add encryption and change the type of capacity. Exalt’s equipment works at a range of frequencies between 100 MHz and 2 GHz, both licensed and license-free.

North American wireless network operators currently spend about 25% of their operating expenses on backhaul — and where to target those dollars will be critical as demand for data and streaming traffic rises, said Bruce Peterson, founder and CEO of Velocent Systems.

Recognizing that, Velocent has created software that lets operators analyze network traffic to determine which base stations to upgrade first. By using deep packet inspection, Velocent’s solution can determine on an aggregate basis which users and what types of devices are using particular cell sites for particular purposes.

“We work off the same feed that the government takes for lawful intercept,” said Peterson. “It’s not real-time, but we process it every five minutes.”

Using Velocent’s data, Peterson said operators will be able to determine which cell sites are used most heavily by “VIP users” — the 20% of customers who generate 80% of all traffic — and target upgrades accordingly.

Despite Ethernet’s slow progress in North American backhaul networks to date, carriers have strong financial motivation to move to it, said Michael Howard, principal analyst and co-founder of Infonetics Research. He added that carriers also are interested in generating further efficiencies by moving TDM traffic onto Ethernet through circuit emulation or pseudowire technology.

All major North American mobile operators have done requests for proposal and requests for information for Ethernet backhaul, Howard said.

“The second half of this year we’ll start seeing real rollouts,” he said. Those rollouts, he added, will include fiber, copper and microwave implementations of Ethernet.

Whither pseudowire?

About 18 months ago there was a lot of hoopla over another wireless backhaul option: carrying T-1 traffic over Ethernet in packet form with pseudowire technology. By using network resources more efficiently, proponents argue that this approach can save money compared to using T-1 in its native form.

All major North American wireless carriers have traffic running over pseudowire, said Eitan Schwartz, vice president of pseudowire and Ethernet access for RAD. Reading between the lines, the majors’ use of pseudowire appears directly tied to connections they purchase on a wholesale basis from other carriers.

Pseudowire is an excellent solution for operators that offer backhaul on a wholesale basis to other carriers, Schwartz said. “The transport provider’s goal is to provide the mobile operator with cheaper, more scalable bandwidth that takes into account unpredictable behavior,” he said.

Although competitors question how well pseudowire works with streaming, Schwartz said it isn’t a problem. Noting that wireless HSDPA and UMTS standards are ATM-based, Schwartz said concerns can be addressed by appropriately configuring ATM parameters.

Outside North America, both BT and Telecom Italia have committed to using pseudowire for backhaul, said Michael Howard, principal analyst and co-founder of Infonetics Research. “Absolutely, they have streaming traffic,” he said.

Howard added that he expects to see some carriers adopt a hybrid approach, sending voice traffic over TDM but running video and data in packet form.