Impacts of LTE on PTN Mobile Backhaul

March 27, 2014

Author: Babak Samimi

While carriers worldwide are embracing the new 4G/LTE era, PTN, the mobile backhaul technology, is in need of essential upgrades to address complex networking challenges. Some Network Diagram LTE Backhaulof the challenges might be big enough to spark a PTN technology revolution.

Carriers are moving to LTE for its much faster data rate to cope with ever-increasing mobile data traffic. So it’s no surprise that the backhaul network needs to scale up in capacity and performance to match LTE. With multiple simultaneous technology inflection points from radio to backhaul, the complexities introduced to address these needs are opening doors for innovation.

Layer 2 to Layer 3

Today’s PTN network is the result of the 2G to 3G transition to replace circuited switched networks. 2G/3G base station traffic is aggregated by a cell site aggregator and carried to a central location known as an RNC (Radio Network Controller). In this hub  or star topology, base station traffic is transported through a point-to-point connection which can be easily supported on a Layer 2 network, such as PTN, using pseudo-wire technology.

LTE has a flat IP mesh topology, so the central RNC is no longer needed, and cell site traffic doesn’t have to go to the same central location. Instead, the controller function is distributed across the base stations, which requires migration from Layer 2 to the introduction of Layer 3, into PTN mobile backhaul for 4G LTE.

3G/4G Co-Location

There are many ways to deploy LTE: new LTE cells can be created; new LTE base stations can be installed on an existing cell tower together with 2G and 3G base stations; or, a 3G base station can be upgraded to LTE through radio head and software changes.

Regardless of the method, carriers have to manage new 4G deployments co-located with existing 2G and 3G installations. Using the same cell site aggregator to support both LTE and 2G/3G backhaul is a great way for carriers to save on CAPEX, but the aggregator will need multi-service capabilities.

Adding to these issues, the large scale of LTE deployments makes backhaul network management more difficult. Technology to simplify this and reduce OPEX is in high demand; Software Defined Networking (SDN) is very promising because it allows for innovation in equipment control planes and network management systems so they can evolve to meet demands.

A solution that can scale backhaul network capacity, offer a smooth transition to Layer 3 in PTN, and address the need for co-location of 2G/3G with 4G LTE is clearly needed. Our team saw this as an opportunity to design a unique Carrier Ethernet Router-on-Chip silicon architecture that’s available in our new WinPATH4 mobile backhaul processor. Not only were we able to combine the switch and router functionality, but we also integrated the required IP that allows for simultaneous backhaul of 2G/3G and 4G/LTE in a single platform.

Our flexible pipeline architecture allows our customers to support SDN through OpenFlow today. The programmability of that pipeline also allows for smooth migration as OpenFlow standards evolve, ensuring seamless customization of their new mobile backhaul equipment.

What major challenges do you see in having to evolve mobile backhaul products into a 4G/LTE + SDN era?

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