The CoS factor
But even as operators look to deal with hetnets in terms of managing connectivity on the access side, hetnets create new challenges in the backhaul side of the network as well.
Much of the backhaul challenge stems from the trend of operators deploying Carrier Ethernet as a backhaul solution to deal with mobile data growth, which is cheaper and more efficient compared to adding old-school E1 links to each base station, but becomes expensive for operators shifting from a macro cell to a small-cell architecture.
And it gets even less impractical once operators start factoring in CoS, which has become a crucial metric in the mobile broadband game. The changing nature of mobile data itself and the increasing importance being placed on the customer experience means cellcos need the ability to prioritize traffic in their backhaul links to ensure that low-latency apps like video and games run at optimum performance without resorting to throwing more bandwidth at the backhaul.
"Traditionally, when a service provider offered metro Ethernet, there was only one CoS for each circuit," says Aaron Tong, senior consulting specialist for mobility, Asia Pacific, at Juniper Networks. "So if a customer required multiple-CoS, they needed to lease multiple circuits, then map different types of traffic onto those circuits, which is more costly because the customer has to buy multiple circuits, and then they have to manage those circuits."
Udi Gordon, executive VP of marketing and business development for Ceragon Networks, adds that this becomes even more unmanageable under a hetnet scenario because service providers have to maintain CoS not only for different access networks, but also for the different services and applications running on each of them.
"If you have to maintain tens or hundreds of different services on your network and make sure every one of them has a unique service profile, that makes it much more complex and difficult to manage," Gordon explains. "If you just had a mobile access network, in many cases the base station was aggregating different users, and at the output end of the base station you can see your web users, your video users, and so on. But with a hetnet you have one base station that's 2G, one base station that's 4G, one Wi-Fi, one business access - each of which has different classes of service and you have to support them all."
In February the Metro Ethernet Forum addressed the problem with the release of its MEF 23.1 Multi-CoS Implementation Agreement (IA) for mobile backhaul - which itself is part of a broader release dubbed Carrier Ethernet 2.0 - that essentially standardizes ways for cellcos to implement multiple-CoS within a single Carrier Ethernet backhaul link. The MEF says this makes backhaul links lower-cost and easier to manage.
MEF 23.1 doesn't come without creating new challenges, of course. For a start, says Tong of Juniper, one element not laid out specifically under the new specs is how to define service attributes, especially SLAs, for things like latency and jitter, for instance.