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Mobile & Wireless
Finding fiber-based cell backhaul success
Service providers need to adopt a unified access network
by Andrew Freeman, Solutions Marketing Director, Calix
The North American cellular backhaul market has reached an inflection point. A confluence of new fiber-based technologies, service demands, and viable competitors is causing cellular operators to reevaluate their options, and a significant reshuffling of market share among existing service providers is now taking place.
Throughout North America, cellular operators are beginning to migrate their cellular base stations away from copper transport to fiber-based transport. Fiber-based transport is desirable for two reasons:
1) It provides a natural, scalable migration path to high-bandwidth Ethernet transport for high-bandwidth, all-Ethernet wireless protocols such as long-term evolution (LTE).
2) It provides cellular operators with the greatly enhanced service reliability of existing TDM T1 transport, which will remain in service for many years as legacy wireless protocols gradually give way to newer, higher-bandwidth protocols such as LTE.
While this migration appears to be an opportunity for service providers, it can also be a threat to incumbent service providers due to the intense competition in the telecom industry, especially in urban and suburban areas. Cellular operators are taking full advantage of the competitive landscape by requesting proposals from a wide variety of transport carriers, including ILECs, cable MSOs, public utilities with fiber networks, IXCs, and facilities-based CLECs. The high degree of competition for this business is drawing attention to the need for a more cost-effective approach to the twin requirements of SONET-grade, fiber-fed T1s and scalable Ethernet. With the traditional approach of using separate equipment for TDM and Ethernet services proving to be cost prohibitive, a Unified Access Infrastructure which spans both technologies ensures competitive viability and service reliability.
A Unified Access Infrastructure utilizes a common, scalable, service-delivery platform for high-volume residential services and low-volume, specialized business services. With a single management platform for all services, robust service management capabilities for Metro Ethernet services, and exacting synchronization compliance of T1 services, a Unified Access Infrastructure holds the key for successfully competing for the growing and lucrative fiber-based mobile backhaul business. The basic nature of a Unified Access Infrastructure enables cost-effective initial deployments for mostly TDM traffic (T1s), and enables a zero-cost Ethernet upgrade with integrated auto-sensing Fast Ethernet/Gigabit Ethernet ports for the inevitable upgrade to 4G wireless protocols such as LTE.
With the transition from TDM to Ethernet in full swing, carriers are caught in a paradox. Because the delivery of Metro Ethernet services using traditional, enterprise-oriented Ethernet technologies requires nailing-up dedicated fibers on a per customer basis, a successful marketing and sales strategy will inevitably exhaust the limited fibers available in the outside plant fiber distribution network. Hence the paradox – success in delivering fiber-based services can lead to ever accelerating costs of fiber reinforcement. And at $10 per foot or more to trench new fiber in urban environments, any technology that eliminates the need to reinforce existing fiber runs can generate over $50,000 per route-mile in operational cost avoidance. For that reason, a commonly used technology in an effective Unified Access Infrastructure is GPON. One of the most appealing features of GPON is its ability to feed up to 64 customers from a single strand of fiber. The use of GPON extends the useful life of installed fiber plant, allowing carriers to focus their capital budget on last mile fiber builds for new revenue opportunities.
GPON is also appealing due to the fact that some advanced vendor implementations support differential timing and SONET grade latency and jitter characteristics of T1 services. It is this simultaneous support for SONET-grade T1s and scalable, high bandwidth Metro Ethernet services that makes GPON an ideal choice for fiber-based mobile backhaul. Whichever service triggers the initial build-out to the cell site (usually T1-over-fiber for reliability improvement), the second service (usually Metro Ethernet services for 4G Wireless) is enabled simply by cabling the ports to the customer equipment in the base station. Finally, the latest generation of GPON ONTs can train-up in GPON or Active Ethernet mode, thus providing service providers with an important option in dealing with any future cell site bandwidth demands.
To understand the unique operational requirements of cell site transport and the importance of a Unified Access Infrastructure, it is necessary to understand the ownership structure and layout of a typical cell tower. Cell towers are generally not owned or even maintained by cellular operators. Tower operating companies own and operate most cell towers, and multiple cellular operators are frequently co-located on these towers.
Figure 1.
The tower in Figure 1 hosts five cellular operators, each with its own hut or cabinet housing base station equipment, and each locked in fierce competition with each other. In a classic example of what economists refer to as the “tragedy of the commons,” no cellular operator will willingly invest in an infrastructure upgrade that provides any benefit to its competitors. A cellular operator will invest, however, in an infrastructure upgrade that provides a competitive advantage relative to their competitors. A fiber-based transport upgrade provides just such a competitive advantage. Service providers are now able to negotiate a mutually beneficial contract that gives the cellular operator high-quality and reliable fiber transport, yet compensates the service provider through higher rates and long-term contracts that recoup the cost of trenching fiber to a cell site.
Because each cellular operator prefers dedicated equipment, the transport equipment utilized in the delivery of fiber-based services to the cellular operator must be inexpensive and scalable with support for both TDM T1s and Ethernet. The nature of a typical cell-site cabinet dictates that the equipment used must be extremely small with flexible mounting options. For example, the transport equipment must be wall-mountable to fit easily into the non-environmentally controlled enclosure on the cellular base station easement that is typically used for service provider interconnect equipment (see figure 2).
Figure 2.
Operational Requirements of Cell-Site Transport Equipment
For operational reasons, carriers should be able to deploy a cell-site transport solution across a wide variety of environments, including the following:
- Wall mount in a non-environmentally controlled “telco interconnect” enclosure
- Wall mount on an H-Frame or backboard
- Rack mount in an environmentally controlled hut
- Rack mount in a GR487-type cabinet (extended temperature operation)
Solutions for cellular base stations that can be installed at a cell site with a minimum of equipment and site preparation, and that require no easements, concrete pads, power pedestals, or GR487 cabinets, can lead to cost savings as high as $20,000 per base station.
More than ever before, service providers enjoy a wealth of options in selecting the right equipment for a Unified Access Infrastructure. Taking advantage of the unique opportunity and meeting the stringent requirements of mobile backhaul are proving to be a critical complement to most service provider business strategies.
The right choice of a Unified Access Infrastructure allows the service provider to leverage investments in either residential or business access infrastructure for multiple purposes. With residential construction in a deep slump right now, deploying a Unified Access Infrastructure for the delivery of business services such as mobile backhaul sets the stage for a low cost, high bandwidth response to increased demand for residential services when the slump finally ends. With capital budgets under unprecedented pressure, the deployment of a Unified Access Infrastructure is a key strategy for a service provider to establish a durable competitive advantage.
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