Insight: SDN and the Evolution to Agile RAN

Posted by Mae Kowalke on Wednesday, August 12, 2015 with No comments

Although it's often painful in practice, technology evolution is an integral part of the telecom industry. Right now, much of that innovation is focused on broadband access solutions for mobile networks.

But what is the best way to adapt the current state of networks to an implementation that is more robust? However it’s accomplished, many factors must be considered:

  • Affordability
  • Scalability
  • Usability/reusability
  • Evolvability
  • Portability
  • Manageability
  • Security

Software-defined networking (SDN) is a promising framework to create the future of mobile networks. Applying it effectively, however, is a complex task because existing networks rely on many proprietary systems that must be modified or replaced to accommodate the open framework of SDN.

Alliances and collaboration between mobile operators and solutions vendors are vital if SDN is to achieve its full potential. Carriers, of course, look to invest strategically in a way that yields maximum potential for growth.

A first step might be to find synergies between wireline and wireless architectures, converging them into a new kind of network architecture.

Some of the elements needed to make that happen include:

  • Virtualized, software-based apps and services
  • Decoupled services and apps
  • Elimination of proprietary appliances
  • Use of commodity-based merchant silicon to reduce vendor lock-in and cost (for NFV, SDN white boxes)
  • Modular, reusable software
  • Fully interoperable, open platform
  • Open source, supplier-agnostic, and location-agnostic technology
  • Shared Standard Enhanced Control Orchestration Management and Policy (ECOMP) - a way to orchestrate the whole network and all its resources from a single framework
  • Agile development and operations
  • Comprehensive automation
  • Standardized SDN controllers
  • Disruptive technology that changes or eliminates legacy access platforms
The reality is that telecom operators use transport architecture to support a variety of services (data, voice, broadband, video, etc.) for business, residential, and mobile customers. That architecture may include passive optical networks (PON), IP aggregation (IPAG), and digital subscriber line (DSL). What needs to happen now is for wireless, copper, and fiber to become more integrated; that’s how to achieve access speeds beyond 100Gbps.

Mobility access, aka backhaul (transporting traffic from cell sites to core locations and back), is a good area to focus when understanding how that aggregation will happen, because its requirements are more robust than business or residential services.

Traditionally, backhaul was handled using point-to-point connections using Ethernet or TDM, from the wireline entity to the wireless entity, terminating at the mobility center.

The radio access network (RAN) used for backhaul is a collection of technologies, configurations, and architectures that may include distributed antenna systems (DAS), traditional distributed RAN (cRAN), heterogeneous networks (HetNets), and small cells. These radio networks are evolving toward a day when radio and base station units will be located separately. This transforms point-to-point backhaul into two components: fronthaul and backhaul.

This change is affecting operators architectures used to deliver business, residential, and mobility services. They are moving toward virtualized, software-defined architectures to create converged, intelligence access networks.

That evolution involves a variety of network-related aspects and technologies, including:
  • Fronthaul - Connection between the baseband unit (BBU) and remote radio unit (RRU). This is changing so the BBU can be centralized or virtualized, requiring ultra-low latency transport network. Technology option to make that happen include dark fiber pairs, WDM (or CWDM and for CPRI-based interfaces), micro/millimeter wave, and Free Space Optics (FSO).
  • Backhaul - Connection from the BBU central location to the core network. Typically achieved using Layer 2 Ethernet switched architecture.
  • IP Aggregation Platform (IPAG) - Core Ethernet infrastructure with edge and backbone components that may rely on fiber, copper, or high speed broadband.
  • xPON/FTTx - Termination of the Gigabit Passive Optical Network (GPON) to deliver last-mile voice and data signal, including for Plain Old Telephone Service (POTS).   
  • Copper-based broadband access - Used for xDSL and similar services in areas where optical fiber deployments aren’t practical.
  • Customer premises equipment (CPE) - Technology used to terminate services at the customer site. May involve switches/routers relying on optical, copper, or LTE antenna access.
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