LTE poses serious backhaul design challenges

John C. Tanner
15 Feb 2011

Carrier Ethernet is often touted as the ideal technology path for cellcos revamping their backhaul networks to cope with the ongoing spike in mobile data traffic growth, with the chief benefits ranging from capacity gains to cost savings. But thanks to the complexities of wireless network design – especially for cellcos migrating to LTE – realizing those benefits could take a lot of network engineering that takes service requirements into account.

“Before operators select a particular data plane, they need to understand the kind of service connectivity they would require across the backhaul – Ethernet services, for example – and how that scales across the data plane,” says Dr. Raghu Ranganathan, technology director at Ciena. “What you ultimately want to do is scale the capacity with increasingly lower cost per bit, but you need to choose the most suitable network deployment design to achieve that.”

That ability to decouple the backhaul from the cost of traffic is complex in a wireless scenario partly from tricky issues such as optimizing airtime usage (which is difficult thanks to smartphone apps constantly and inefficiently pinging the data network for updates), and partly from LTE altering 3G network architecture by creating a distributed architecture with the radio control shifted to the eNode B, Ranganathan says.

“Optimized backhaul can help, but it requires operators to think in terms matching the connectivity being provisioned across the network with the data traffic that wants to use that capacity,” he says.

An easy example is prioritized traffic like VoIP or video vs best-effort web traffic.

“If, for example, 80% of the traffic is best-effort traffic, it’s not a good idea to design the entire capacity of the network to meet the performance demands of the other 20%,” Ranganathan explains. “You’d end up penalizing the entire network with stringent performance requirements, whereas if you were to match the connectivity with the application or service you’re trying to deliver, then you have an opportunity to optimize the usage of that capacity.”

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