Breaking New Ground in Central Texas

Posted: 07/1999

Breaking New Ground in Central Texas
Wireless Cable Comes to the Lone Star State
By Ted Cook

A little telephone cooperative is breaking new ground in central Texas. But it didn't have to break ground to do it.

Instead of digging to install new fiber, Goldthwaite, Texas-based Central Texas Telephone Cooperative is using broadband wireless technology.

As a cooperative, any person who receives telephone services and holds a membership certificate is considered a co-owner. The cooperative's service area is divided into districts and a member from each district is elected to sit on its board of directors. This "customer-owner" relationship helps drive the improvement and expansion of the cooperative's operations. As demand for sophisticated networking services increases, new technologies are sought to enhance service delivery to its customer base.

Central Texas operates in what CEO and General Manager Delbert Wilson defines as a rural area more than 45 minutes from a department store. Deeply rooted in the community, the cooperative began in 1951 by offering affordable telephone services to people living in rural, central Texas. At the time, it had only 614 members. Central Texas now has more than 6,700 access lines covering 3,302 square miles, with fiber optic facilities between each of its 17 exchanges. It uses various network technologies to provide a broad range of telecommunications services including Internet access, local and long distance telephony, cellular services, multichannel multipoint distribution service (MMDS), distance learning with eight rural schools and a telemedicine project planned for three rural medical clinics.

A Big Move

After studying and tracking the potential of local multi-point distribution service (LMDS) broadband wireless technology for many months, Central Texas in 1997 decided to participate in the oft-delayed Federal Communications Commission (FCC) auction of LMDS spectrum rights. The cooperative recognized it could use LMDS to expand its network and deliver high-speed, high-bandwidth services over the air at millimeter-wave frequencies. Using broadband wireless, the cooperative could provide last-mile connections to new customers and enhance service delivery to existing customers. Deploying this technology also would be more cost-effective than investing in new fiber to expand its existing network.

When the auction was finalized in March 1998, Central Texas had won its bids for both A and B block licenses in the 28-gigahertz (gHz) and 31gHz bands for two basic trading areas (BTAs). An A license allows 1,150 megahertz (mHz) of bandwidth, while B licenses allow 150mHz. By capturing both licenses, the cooperative ensured it would be the only service provider using LMDS in its coverage area.

Once it secured the licenses, Central Texas faced the challenge of integrating the new technology throughout the 380 miles of fiber already connecting both BTAs and the existing access tandem switch. Because the company was already delivering cellular services to San Angelo, the largest city in its two BTAs, it decided that, in addition to expanding networking services and coverage areas via LMDS, it also would overlay its circuit-based shared network with an asynchronous transfer mode (ATM)-based backbone.

ATM would extend from its backbone through the wireless access portion of the network.

"Central Texas spent a lot of time researching LMDS, looking at the products, availability and architectural design concepts," Wilson explains. "For our purposes, we wanted to optimize our use of both broadband wireless and ATM to achieve our business objectives. One of our main priorities was securing an end-to-end solution."

Showing Some Backbone

Central Texas already has installed several of the 17 ATM switches that ultimately will make up its network backbone. The switches are scaleable from 800 megabits per second (mbps) to 51.2 gigabits per second (gbps). They support permanent and switched virtual circuits (VCs) to enable service offerings such as cell relay, frame relay, circuit emulation and internetworking. They also offer redundant protection of the switching fabric, power supplies, synchronization, control, call processing, and line and trunk interfaces. The same switches also provide radio interface to support the broadband wireless portion of the network.

This approach to broadband wireless allows Central Texas to consolidate multiple networking services, enable dynamic bandwidth and ensure guaranteed quality of service (QoS) for its business customers. With the ATM-based backbone, the cooperative also can offer other value-added applications, such as virtual private networks (VPNs), encryption, teleconferencing, voice over Internet protocol (VoIP) and distance learning, as well as QoS billing, statistics gathering and maintenance support. By exploiting ATM functionality to the edge of its network, Central Texas has ensured its service delivery portfolio is flexible, robust and relatively future proof (see diagram, "Central Texas ATM Network Overlay and LMDS Coverage," below).

Image: Central Texas ATM Network Overlay and LMDS Coverage

San Angelo, the largest city in its coverage area, will be the pilot location for the delivery of Central Texas' last-mile broadband wireless services. The first phase of the LMDS network will be launched later this year following detailed planning of the four initial cells. Strategically located buildings and towers throughout the San Angelo coverage area will serve as the platforms for base station transmitters and receivers. Three-dimensional aerial blueprints of six other Texas cities, including Ballinger, Brady, Brownwood, Comanche and Goldthwaite, also have already been completed (see diagram, "Central Texas LMDS Architecture," below).

Image: Central Texas LMDS Architecture

The cell-planning process helps determine cell layout, size and sectors. Cells are being designed to accommodate both present and future service requirements of the network. Because LMDS can be built out as demand warrants, its design to address future requirements increases the operational and cost effectiveness of the network without increasing the overall cost. Potential rainfall effects, line-of-sight requirements, and inter/intracell interference suppression are all being factored into the final cell plan.

Demographic data on coverage areas is used to help determine an appropriate mix of dedicated and shared access services using both time-division multiple access (TDMA) and frequency-division multiple access (FDMA). FDMA is used for dedicated bandwidth connections of fractional or full OC-3c/STM-1. For T1/E1 (full or fractional), 10BaseT Ethernet and plain old telephone service (POTS), TDMA is generally employed.

Use of both access methods enables Central Texas to manage bandwidth resource efficiently and cost effectively while accommodating both TDM (such as T1, leased line, telephony etc.) and bursty (such as Ethernet) traffic from a common infrastructure.

The Central Texas LMDS network is based on a distributed architecture whereby intracell switching functions are performed in the base station to minimize backhaul requirements. The base stations also are able to accommodate interconnection with various points of presence (POPs) throughout the network, which facilitates the planning process.

Delivering the Goods

Central Texas is employing a network management system (NMS) that manages both its wireline and wireless network components end to end. Three-dimensional information gathered from the aerial surveys is being incorporated into the NMS to allow Central Texas to determine line-of-sight availability to new customers immediately. Services then can be activated within hours of the request.

Central Texas will offer high-speed voice, data, Internet, multimedia and videoconferencing services with its wireless last-mile connections. While the initial focus is on business customers, the cooperative also is including residential and smaller community markets in its future plans.

"Many of the smaller communities within our coverage areas are hungry for new services," Wilson says. "As our LMDS deployment progresses, we will continue to evaluate the economies of these niche-market opportunities for broadband wireless access."

The cooperative also will continue to work with rural schools and medical clinics by offering its networking support to distance-learning, telemedicine and Internet-access projects.

In addition to LMDS, Central Texas provides wireless cable services to about 3,000 subscribers using MMDS. Now that the FCC is authorizing two-way applications in that band, Central Texas also is considering the future role of MMDS in its network strategy.

"You can't predict the future," Wilson says about the company's decision to be the first U.S. LMDS licensee to go public with its choice of architecture, "but you can help create it."

Ted Cook is business development manager for Newbridge Networks Inc., Herndon, Va. He can be reached at tcook@newbridge.com.

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