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The explosive growth of 3G and 4G applications has placed significant demands on mobile backhaul. Wireless service providers require 50 megabits to 100 Mb at large capacity sites today, growing to 300 Mb to 1 gigabit by 2015. Mobile backhaul planners and engineers have the dual challenge of satisfying the bandwidth scalability requirement and at the same time deliver significant capital expenses, operating expenses and leased backhaul cost efficiencies. 10GigE Ethernet multi-node rings clearly meet the performance and scalability requirements, but is 10GigE the right solution for every tower? The answer depends on location, time frame, and what type of cell tower.
Where: The amount of backhaul capacity needed at the tower is driven by the population density in the tower footprint. The largest requirements are in dense-urban locations. An urban center site typically requires three- to 10-times more bandwidth than a rural site; with a suburban site falling somewhere in-between.
When: While cell site bandwidth is growing dramatically, demand per cell has not reached 300 megabits per second … yet. However, a 2012 network deployment must be able to scale for multiple years. One of the largest wireless carriers requires 50 Mbps of capacity at every tower today and expects demand to grow to 200 Mbps to 300 Mbps in the largest sites by 2015. While 2015 may sound like a long time away, it’s not very far from the perspective of network architects and planners.
What type: Mobile backhaul providers need to consider the implications of multi-tenant locations. In North America, 50% of towers have more than one carrier on the tower. A tower may support up to six carriers, with the average tower hosting 2.7 carriers. 4G services require a higher density tower footprint, resulting in the need for more cell sites. This drives more multi-tenant towers, in places that were traditionally single tenant, and will increase the number of carriers on existing multi-tenant towers. The aggregate bandwidth requirement of multiple carriers results in a backhaul requirement of 500 Mb to 1GigE to a single tower site. Also, a radio-hub aggregation site which serves multiple remote towers via point-point radio requires 1GigE or more of backhaul capacity.
Backhaul providers reduce fiber consumption and improve hub switch port efficiency an order-of-magnitude by putting multiple towers on a G.8032 ring. Increased fiber efficiency is especially important when a carrier has limited fiber or is using leased fiber. 10GigE provides the additional benefit of more flexibility to handle the bandwidth scaling over time versus multiple 1GigE solutions.
Network planners want to deploy 10GigE to the largest possible footprint so they don’t have to change out equipment in a few years as capacity scales. To ensure an optimal design, they consider bandwidth growth requirements, fiber cost savings and equipment capex savings in their design modeling. Consider an example network where 16 towers are passed by a fiber route with a monthly fiber lease cost of $3,000 per pair. A 10GigE solution is more cost-effective than multiple 1GigE rings on separate fiber pairs once the average bandwidth per tower exceeds 125 Mb to 150 Mb.
As this example shows, 10GigE proves in at a fairly low bandwidth threshold. The mobile operator requires more than just attractive cost per bit however; they also require high performance, reliability and real-time service-level management and reporting. 10GigE Carrier Ethernet is up to the task, delivering important features including:
–99.999% reliability to deliver the same performance as SONET/SDH.
–50 millisecond protection switching with G.8032 Ethernet ring protection.
–Temperature hardened, compact and power efficient for the cell tower cabinet.
–Per-flow service level monitoring with Y.1731 for every service EVC.
–Differentiated services with hierarchical quality of service, and dynamic flexible queues.
–ENNI for connections between service providers with MEF26 ENNI.
Service providers focused on cost-effective scalability are already architecting 10GigE solutions for mobile backhaul. These carriers optimize capital expenditure efficiency by incorporating the three to five-year bandwidth growth projections, equipment capex and fiber costs into their design models to maximize their 10GigE footprint. This smart deployment of 10GigE ensures cost-effective and seamless scaling to handle the growing demand at the cell tower.
Scott Knox is Director of Solutions Development at Overture, http://www.overturenetworks.com.