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Distributed antenna systems: From niche to necessity

05 марта 2010

Over the past few years, distributed antenna systems have quietly emerged as a powerful tool for wireless carriers looking to bolster their coverage and boost their capacity--key concerns in the age of smartphones and 3G.

DAS technologies can be used for indoor locations--mainly to boost signal coverage in large buildings and at stadiums and shopping malls--as well as for outdoor purposes. Essentially, DAS is a collection of small antennas spread over a specific geographic area and connected by fiber back to a central location or power source, usually a base station.

The benefits of DAS are two-fold: The technology allows carriers to fill in coverage gaps and dead spots in their macro network; and, by breaking down the macro cell site into smaller pieces, it helps add much-needed capacity to operators' networks.

"It's used to fill in gaps where the big cells may not reach, but going forward it will probably replace a lot of big cells in a lot of situations where they need high capacity," said Allen Nogee, an analyst at In-Stat. "It's getting to be more about capacity."

A growing market
"Up until the last couple of years, it had been a niche market," said Dave Cutrer, the CEO of NextG, an outdoor DAS provider. "Carriers would use it solve specific problems."

The technology behind DAS is not new, and carriers have been using it for years. But lately, due to subscribers' skyrocketing mobile data demands, operators have turned to DAS as a much-needed boost to capacity.

Nogee said today there are eight or nine major players in the DAS market, including ADC, NextG, Newpath Networks and larger tower companies such as American Tower and Crown Castle. They're all trying to meet the needs of carriers that want to get their signal closer to where users actually are, he said.

PCIA's Connie Durcsak said DAS is primarily used as a surgical solution to enhance coverage in a specific area. But engineering the network to enhance capacity is becoming just as important. "It has really evolved from a deployment need to an engineering need," said Durcsak, who is executive director of the DAS Forum within PCIA, a wireless infrastructure industry trade group.

The DAS market is still nascent, and there are no precise figures on how large it is. Durcsak said PCIA does not keep track of exact figures because it's difficult to track the differences between indoor and outdoor DAS systems. However, she added that the industry has "probably evolved exponentially."

Cutrer of NextG said the outdoor DAS market is probably a $500 million market. Tony Lefebvre, ADC's director of product management for outdoor DAS products, said the market is probably between $400 million and $450 million for outdoor DAS

Lefebvre estimated there are roughly 10,000 outdoor DAS nodes, or site deployments, in the United States. Recently, NextG said it crossed the 5,000 deployment mark. And the market for indoor DAS, or in-building wireless deployments, is even larger. John Spindler, ADC's vice president of product management, cited a recent ABI Research report predicting 89,000 indoor DAS deployments worldwide this year.

Carrier connection
Shuaib Porjosh, Sprint Nextel's director of radio frequency engineering, said he thinks more carriers are turning to DAS "just because the solutions are becoming more surgical."

When evaluating a possible DAS deployment, Porjosh said Sprint considers the location's geography and topography, the size of the area, and whether the company needs to build the system from scratch or can hop onto an existing, neutrally hosted DAS system.

Neutrally hosted DAS systems are analogous to tower sites that support multiple antennas for different carriers. Durcsak said the preponderance of outdoor DAS systems will be neutrally hosted sites. Porjosh said the estimate of 10,000 outdoor DAS nodes sounded accurate, and said Sprint has deployed roughly 1,500 such sites.

Verizon Wireless spokesman Tom Pica said the carrier uses DAS today to serve large customers where they need a better signal--such as arenas and airports. He said that when Verizon launches its LTE network, it will continue to use DAS in that way.

T-Mobile USA declined to comment on its use of DAS and an AT&T Mobility spokeswoman did not respond to requests for comment for this article.

For in-building coverage, Porjosh said Sprint generally leverages its relationship with a landlord to have a DAS system installed. For outdoor DAS systems--as with regular cell towers--carriers must get approval from local municipalities. In-Stat's Nogee noted carriers have been turning to DAS technologies as a way to overcome strict zoning requirements, since the antennas for outdoor DAS systems can be placed on telephone poles and lamp posts. Lefebvre said they can be hidden in street furniture or placed as a piece of fake cactus.

DAS drawbacks
DAS is more expensive than putting in a regular base station, Nogee said. Cutrer of NextG conceded that installing a DAS system is initially pricey, but argued DAS can be effective if carriers look at total cost of ownership over the life of the contract.

"I really wouldn't say it's the preferred solution," said Michael Saperstein, PCIA's director of government affairs. "It's very expensive."

Cutrer said NextG can typically install an outdoor DAS system in nine to 12 months, but the timing largely depends on scoring leases from local municipalities.

"If the objectives are such that the economics don't make it worth it from [a return on investment] standpoint from the carriers' perspective, they'll walk away," PCIA's Durcsak said.

Despite the difficulties, DAS is coming to be viewed as a key element of network deployment for carriers.

"We're definitely seeing an uptick," Sprint's Porjosh said. "And I think the more the networks mature, DAS becomes a more and more important tool in the toolbox."

Источник: FierceWireless

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