Priority 1: The Mobile Backhaul Network

The missing link, however, is the backhaul network, which in North America runs primarily over ATM. While ATM can approximate QOS, it does so by mapping categories onto three or four available service classes, which allows the network to prioritize voice over data but leaves little flexibility with different types of data traffic, said Steve Dyck, director of mobile solutions for Alcatel-Lucent.

But as carriers migrate to end-to-end IP-based networks and embrace Ethernet — either through hybrid approaches where data is offloaded from the ATM network or by overhauling their networks entirely to carry both data and voice over the same IP architecture — a new world of QOS options opens to them, giving them far more flexibility to handle data traffic, Dyck said. QOS classes applied in the core or the RAN could be expanded to the backhaul network, creating an end-to-end architecture that can prioritize traffic along its entire journey between handset and destination, Dyck said. What's more, that prioritization lessens the need for operators to throw more capacity onto their backhaul networks because certain traffic can be delayed until logjams clear and aggregation points can distribute overall network capacity to multiple cell sites, Dyck said.

“QOS allows the operator to overbook the network by optimizing it,” he said. “There is pressure on operators to reduce backhaul costs. They can't just keep throwing capacity at every cell site. … Bandwidth will always be limited, but QOS can help them manage it.”

How much capacity can be saved depends on the traffic type. If all services on a network are real-time, then QOS provides little benefit as every application receives the highest level of prioritization. But because much of the traffic increase is coming from Internet and e-mail, QOS can provide some significant advantages in capacity planning, said Stu Benington, director of global portfolio marketing for Tellabs. Assuming a network carries equal levels of voice and data, with a broad distribution of data types, advanced QOS wouldn't quite double the efficiency of a backhaul connection, but it could increase it by half, Benington said. As leased backhaul becomes the largest operational expense to wireless operators beyond payroll, that kind of capacity savings is substantial.

The full benefit of QOS comes when operators can use prioritization to offer service level agreements, creating “premium” plans for their customers, Benington said.

“In this competitive environment of scarce capacity, QOS is key to providing a better experience to their customers,” Benington said. “Today operators are looking more toward eliminating these capacity bottlenecks, but tomorrow they'll be able to leverage those capabilities to create offer new types of services.”

Source: Alcatel-Lucent