Old Telco Central Offices Find New Life in DAS

The telephone switches used in central offices may be fading into history, but DAS providers are finding a new purpose for the iconic buildings.

To power the in-building wireless system in Pauley Pavilion, home of the UCLA Bruins, a central office is now being used for housing the latest DAS technology thanks to advances in fiber transport technology, according to John Spindler, director, product management, In-Building DAS.

“From the central office, fiber can connect a baseband or base station hotel with multiple end points to deploy a multi-band, multi-service solution, either driving an existing passive DAS or an all-active system,” Spindler said.

The key is to pick locations that have varying traffic patterns, such as an office building with people from 8 a.m. to 5 p.m., an arena, which normally has events at night or on weekends, and a mass transportation center where most traffic is going to be from 6 a.m. to 8 a.m. and 5 p.m. to 7 p.m.

“Now you have multiple endpoints and multiple venues that are all sharing the same capacity and really are not putting a strain on it because the traffic patterns are all different, instead of using dedicated capacity where you are just burning up a lot of capacity, which is a scarce resource,” he said.

Spindler hastens to note that the concept of distributing network architecture is not new. The company deployed a system in the London Tube 10 years ago, running a system off of four base station hotels that each supported around 25 or 30 stations.

Tony Lefebvre, director, product management, outdoor wireless products, added: “The reason [distributed network architecture] is coming of age now is that when you look at a typical football stadium today, you are putting in a minimum of 18 sectors, which was unheard of before. We have this tremendous capacity need, but the typical venue does not have the real estate to house all the equipment.”

Another reason distributed network architecture is becoming a reality is advances in technology, such as TE’s Serial Link Combiner, which provides 10 Gbps backbone that allows baseband pooling, digital RF and a direct digital interface to single fiber transport.

“Centralizing baseband resources to feed our DAS is a new concept,” Spindler said. “It is a money-saving concept, because you don’t need all those power amps in the base stations. They are costly, generate heat and consume electricity.”

Digital capability across the fiber allows fiber runs from the headend of up to 13 miles.

“That is pretty compelling because if you think about a 13-mile radius around a headend, you can reach a lot of end points,” Lefebvre said. “With digital transfer over fiber, we are able to take the baseband all the way out to our remote heads.”

In Barcelona, Spain, this week at the Mobile World Congress, TE Connectivity will announce the availability of the 10-Gbps optical transport product for small-cell networks called the Serial Link Combiner (SLC), which reduces the amount of fiber needed in a small-cell network from six fiber strands to two, lowering fiber leasing requirements  and reducing operational expenses.

Each SLC chassis supports four 10-Gbps links; each 10-Gbps link supports up to 225 megahertz of RF spectrum transported over a single 10-Gbps fiber pair.