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Mobile backhaul network primer

Understanding mobile backhaul

In mobile network architecture, the backhaul infrastructure carries voice and data traffic between a cell site and its mobile switching center using copper, microwave or fiber

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for transport.

Traditionally, mobile backhaul has relied on time division multiplexing (TDM) and used leased lines or microwave to transport traffic, depending on the geography and the accessibility of the cell site location. That architecture predominated in the voice-centric cell phone days of yore but began to change with the arrival of mobile broadband.

To support growing mobile broadband data loads, service providers have been supplementing TDM with IP and Ethernet for mobile backhaul. Now operators believe an all-IP/Ethernet backhaul network infrastructure will best meet their evolving needs, although that transition will take several years.

Why you need to know about mobile backhaul

The interest in and importance of mobile backhaul strategy has increased as broadband services have evolved. As more carriers recognized the value of supporting all-packet-based 4G Long-Term Evolution (LTE) services, they have begun to think differently about the transport portion of their networks. They now see mobile backhaul more as a strategic asset than a problem to be solved.

"Operators realize that if they have enough bandwidth capacity and quality of service (QoS) [capabilities] in the backhaul network, it can be a big differentiator for them. They can avoid issues like unhappy users, voids in service and periods of poor performance," said Glen Hunt, principal analyst, transport and routing infrastructure, with Current Analysis. "The backhaul network can be a fundamental, positive asset in enabling carriers to support the growing number of services."

What you need to know about mobile backhaul

Carriers are grappling with the best way to design their backhaul networks to ensure they're capable of handling anything that future LTE services throw their way. This is a thornier problem for legacy providers that rely heavily on traditional circuit technologies in the backhaul portion than it is for operators that have implemented an IP overlay. For emerging carriers or 4G WiMAX providers, like Clearwire, with no legacy infrastructure, it's a non-issue.

As little as a year ago, carriers centered their mobile backhaul plans around a dual/hybrid strategy, using the IP overlay for data traffic and the legacy circuit-switched network for traditional voice. But the all-IP network is now apparently in favor. In its biannual mobile backhaul market study, for example, Infonetics Research found that 65% of the 18 mobile operators and backhaul transport providers surveyed now have a strategy in place to move to an all-IP/Ethernet backhaul infrastructure.

Industry watchers see a few reasons for moving mobile backhaul infrastructure to IP/Ethernet. Financially, support for a dual-transport environment is more costly over the long term. The timing and synchronization concerns carriers originally had about carrying 2G and 3G traffic over an IP network have dissipated with technology advances. And as Hunt points out in a recent backhaul strategies report, "Many base stations will support LTE alongside 2G and 3G, resulting in a single packet-based Ethernet pipe from the base station. This will also tend to simplify the backhaul, since the traffic is encapsulated and transported as packets without the need for native TDM interfaces."

Vendor focus on mobile backhaul Fortunately, mobile network equipment providers have done a good job of keeping up with the changing times, which means carriers have plenty of equipment and professional services options for designing and provisioning their next-generation backhaul networks. Potential vendor equipment providers and partners include the usual suspects, such as Alcatel-Lucent, Ciena, Cisco, Ericsson and Nokia Siemens Networks (NSN), among others.

As mobile network architects consider their options, they must keep in mind how to apply packet-based technologies like Carrier Ethernet, scale from 10 to 100 Megabits per second (Mbps) capacity, use Multiprotocol Label Switching (MPLS) and MPLS signaling (for QoS and traffic management mechanisms), and transport errorless sessions, Hunt said. Understanding optical transport will become increasingly important over the long term as carriers' use of copper plant and microwave evolves to fiber, as appropriate.

"A well-designed backhaul network that takes into account all these parameters will probably not have to be re-architected in the future, although it will have to scale higher," he said. "What's going to be important is to scale the Ethernet-based services while accommodating the 2G and early 3G services."

About the author: Beth Schultz is an IT writer and editor based in Chicago.

This was first published in May 2011

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