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Repeat Performance

By David Bolan

Wireless operators rolling out new networks want to see a return on investment before rounding out their coverage, but also need full coverage from the outset to lure subscribers. Repeater networks offer a cost-effective way of solving the dilemma. David Bolan, vice president of marketing, Repeater Technologies

Carriers continue to tout the benefits of enhanced services and features as they compete for new subscribers. Yet these advanced features are worthless to users if coverage is poor in the areas in which they make calls. As a result customers are quick to churn to other providers because of coverage problems and this has brought the role of repeaters to the fore.

The sophistication of today's digital cellular and personal communications services (PCS) systems, along with rapid growth in competition, demands that carriers deploy repeaters from the outset as part of their initial network buildout. A repeater network coverage scheme is arguably the best way to maximize initial coverage without expending huge chunks of capital for unnecessary base station capacity.

This strategy is starting to catch on. Seven PCS CDMA carriers in North America have recently begun deploying RepeaterHybrid Network (RHN) technology from Repeater Technologies in their respective markets. Clearnet has the challenge of providing coverage for the whole of Canada; Wireless Communications Venture is a PCS F-block player with the license for the St. Cloud, Minnesota market, covering 250,000 potential customers (pops) under the Lifecom name; and Central Wireless Partnership, conducting business as Via Wireless, is the F-block carrier for five BTAs in California's Central Valley.

Wireless North in Minnesota is covering 13 basic trading areas (BTAs) or 2.5 million pops in 110,000 square miles; the Virginia and West Virginia PCS Alliances, conducting business as Intelos, have 5.1 million POPS over 23 BTAs in 59,000 square miles; Amica Wireless in Illinois and Iowa has 13 BTAs and 1.9 million POPS to cover in 35,000 square miles; and Alaska DigiTel in Anchorage has 448,000 people in the country's largest BTA-344,000 square miles.

These carriers expect to save between 30 and 50 per cent on their network deployment costs by using RHN architecture. They are using repeaters at buildout to augment base stations and expand cell coverage while minimizing wasted capacity and real estate costs. This deployment strategy reduces their initial investment outlays, lowering capital requirements and freeing up money for operations and marketing.

Extending coverage

Clearnet decided to use repeaters in its network to hold the line on costs without having to sacrifice coverage. "By using repeaters, we can deploy cost-effective coverage solutions in a variety of scenarios on time and on budget," says Eros Spadotto, the company's vice president of networks and information systems. "This will allow our clients to utilize the benefits of our state-of-the-art digital network rather than roaming to the analogue network as often. Not only does that mean our clients can maintain access to all of our PCS features and services, but we are also able to control our analogue roaming costs."

Lifecom's general manager, Bill Casto concurs: "Why do we need to install 100 per cent base station units at higher cost when we can extend our coverage with repeaters and save on capital?" he asks. "By using a repeater, I don't need a backhaul connection, so I save on the costs of a T1 or microwave link. All I need is a line of sight with the repeater and an antenna back to the donor site and I'm ready to go. The hybrid repeater implementation reduced our capital outlay from the start and left us with more in our reserves."

David Nelson, general manager of Central Wireless, sees a similar picture. "Repeaters increase the effective coverage area of our cell sites," he says. "And they do it with a smaller footprint in terms of real estate, as well as less infrastructure."

This can be useful when it comes to coverage in small towns, says Rick Rapp, president and CEO of WirelessNorth. "Implementing a RepeaterHybrid Network is the only efficient and cost-effective way for us to deliver the coverage and capability for the many small towns in our markets and for the 200 miles of I-94 that is situated in our BTA." In addition, our Lifecom neighbor has already tested and proven this deployment strategy."
RHN technology can also provide coverage in difficult terrain. "Our aim is to provide wireless service to 70-80 per cent of the population in our markets over a five-year period," says Bud Zirkle, vice president of CFW Communications, the managing partner for both Virginia PCS Alliance and West Virginia PCS Alliance. "Given the nature of our terrain-which is heavily wooded and hilly- RepeaterHybrid Networks lend themselves to providing the coverage we need to meet our five-year service goal."

"We want to provide our customers with good-quality coverage at a cost-effective price," says Clayton Bodnarek, general manager of Amica Wireless Phone Service. "Our engineering group did an evaluation of Repeater Technologies' network repeaters and we believe they can help us reach that goal."

Proven solution

Coverage can be added through repeaters at a fraction of the cost of base stations. This means carriers can provide coverage in areas where previously they thought they could not afford to do so. Repeaters are a cost-effective and proven solution in markets that cannot justify the costs of conventional deployment.

The easiest way to demonstrate the cost savings of a RepeaterHybrid Network is to look at the case for rural highways. Traditional deployment dictates the use of base stations cascaded along a highway. In the example below, the first row illustrates three base stations along a highway. However, with the use of repeaters a carrier can replace two of the base stations with four repeaters.

Very quickly, then, the cost savings can add up. Instead of three base stations and three T1 or E1 lines for backhaul, you need just one of each. And with repeaters a fraction of the cost of a base station and having no backhaul requirement, cost savings can be as high as 50 per cent.

As can be seen in Figure 1, two architectures can be used for RepeaterHybrid Networks. The first cascades repeaters, which is useful in hilly and curvy terrain. The parallel configuration, on the other hand, is ideal for straighter and flatter terrain and also provides a greater degree of network reliability in the event of an equipment failure, because only one segment loses coverage.

Along a stretch of highway, this deployment strategy allows four repeaters between each base station, as shown over page.

RepeaterHybrid Networks such as these are in commercial operation today. Lifecom's deployment strategy relies on just six PCS base stations, with coverage extended by 24 repeaters. This RHN covers downtown St. Cloud as well as its suburbs and feeder highways-an area of nearly 3,200 square miles-and, according to Lifecom, has resulted in a 60 per cent cost saving when compared to an all-base-station buildout. Lifecom is the first CDMA network to deploy a ratio of four repeaters per base station, making it the most concentrated usage to date.

"The network facility requirements with repeaters are more cost-effective compared to base stations," says general manager Casto. "Repeaters are flexible and can be installed anywhere."

Central Wireless is also expecting to reap substantial savings with its RHN plan for interstate highway coverage in central California. By using over-the-air signals from four of its nearby cell sites in its Stockton, Modesto and Merced network, Central Wireless is able to cover some 70 miles of Interstate 5 with just eight repeaters. "Our decision to deploy repeaters instead of base stations will save us $2 million," says Nelson. "Repeaters allow us to blanket this highway economically."

Cost savings are critical to carriers, but ultimately it is network performance that determines the success of a strategy. It is no different with repeaters, particularly in CDMA networks. Here, repeater specifications are even more critical to network performance.

CDMA networks rely on a feature called 'receive diversity' to strengthen reception, maintain network capacity and increase handset talktime. Repeaters that incorporate receive diversity and higher output power offer greater signal range and no degradation in network performance. The critical requirement of frame error rate in both the forward and reverse direction is met with Repeater Technologies' diversity receiver.

When combined with high output power, receive diversity can significantly expand coverage. "Our units had 6.3 watts of output power," explains Lifecom's Bill Casto, "and we were able to get nearly eight miles of coverage on our feeder highways and a full mile in the core areas."

Remote control

As carriers add repeaters to their existing infrastructures and deploy them in new network buildouts, robust network management software becomes vital. Remote monitoring and control of individual repeaters can reduce network field time and prevent a lot of potential headaches, allowing operators to reconfigure a unit or upgrade software without being on site and without needing to take the unit out of service, for example.

A top-notch repeater software package will be able to manage thousands of repeaters from one regional controller. Some software packages still operate by way of a text interface, but the better ones have become more user-friendly by incorporating familiar Windows graphical user interfaces (GUIs) for easy point-and-click operation. That keeps busy design engineers from having to page through a thick manual just to figure out the software.
The hardware is also important. The software should be designed to run on a low-cost hardware platform-a Windows NT PC for instance.

Good network management software can go a long way towards minimizing downtime, maximizing minutes and simplifying network maintenance. But hardware and software are not the only important issues. A carrier needs to scrutinize the vendor behind it to make sure its engineers have all the support they might require. Carriers need to be able to rely on a vendor which can:

o engineer the path with the proper gain setting in reverse and forward directions;
o determine base station parameters and how to set them;
o understand antenna systems to use;
o and ascertain the expected coverage radius.

Cost and coverage are the driving factors in today's massive infrastructure development, and repeaters are answering these system and carrier requirements. CDMA PCS carriers are increasingly turning to over-the-air repeaters with diversity receive helping them to expand wireless coverage, accelerate deployment and cut capital costs.