One of the tricks to ensuring small cell deployment is worth the effort and expense involved is the use of new network planning models specifically designed for the new world of heterogenous networks (HetNets). With that in mind, engineers at AT&T (NYSE:T) Labs set out to identify radio-frequency propagation models that will help pinpoint optimal small cell placements.
The result of this research is AT&T's proprietary HetNet Analysis and Resource Planning (HARP) tool, which analyzes key data points to help network planners understand how RF waves behave in a small cell environment. Based upon a location's traffic demands, along with building floor plans or topography maps, HARP can determine expected coverage for both indoor and outdoor small cells and recommend the optimal number and placement of small cells.
"It identifies where small cells should be placed and recommends a backhaul solution--all with the goal of delivering an optimal customer experience and maximizing capacity and coverage," said John Donovan, senior executive vice president of AT&T technology and network operations, in a blog entry.
Such technology is crucial for AT&T, which has boldly committed to deploying more than 40,000 low-power small cells by the end of 2015 as part of Project Velocity IP (VIP), a multibillion-dollar overhaul program for both its wireless and wired network properties. But macro cell RF propagation differs considerably from small cell propagation, which has not been well studied.
To create a planning capability for small cells, RF propagation characteristics of indoor and outdoor small cells had to be understood, wrote Sarat Puthenpura, AT&T Labs executive director of service quality management research, in an article posted on the company website. Pathenpura was part of a five-member research crew that worked on the issue.
The team conducted outdoor experiments in Morristown, N.J., near their office location in Florham Park, N.J., as well as downtown Manhattan, using a van with a retractable mast that enabled tests of small cell propagation outdoors at various antenna heights. Additional measurements were collected from several major cities with the aid of a drive test vendor.
Testing of indoor small cell propagation models was conducted in the Florham Park office using a testing platform housed on a mobile rack.
Interestingly, researchers concluded that the fundamentals of RF propagation models for indoor and outdoor small cells were relatively similar, enabling creation of the same planning model for both.
Specific data analyzed by HARP includes "high-resolution geo-located demand, macro network RF and performance metrics, high-resolution clutter, 3D structure polygons, as well as building location level information," Puthenpura said. During candidate site selection, an algoritim evaluations transport availability and cost, enabling planners to focus on a smaller set of potential locations, allowing for more detailed design considerations, he added.
Donovan said HARP is already paying dividends for AT&T. For example, the carrier deployed more than 10 small cells across three floors of a Chicago high-rise to boost coverage and capacity for a customer. Hourly mobile traffic on AT&T's network at that location has increased significantly per hour and the operator now has nearly 100 percent usable coverage across the indoor area.
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