BROADBAND COMMUNITIES is the leading source of information on digital and broadband technologies for buildings and communities. Our editorial aims to accelerate the deployment of Fiber-To-The-Home and Fiber-To-The-Premises.
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TECHNOLOGY for backhauling data to the Internet. Tose that are fiber con- nected are on metro fiber rings rather than on the passive op- tical networks used for most fiber-to-the-home connections because 4G wireless poses increasingly demanding timing con- straints on communication between network elements. Tis is particularly true as the software and spectrum management techniques used to prevent adjacent cell sites from interfering with one another become more sophisticated. "It's all about synchronizing the network," Shaddock says. From an outside-plant perspective, Shaddock says, deploy- ing fiber to a base station is not much different from deploying it to any other building, though because there are fewer con- nections to make, installers are likely to use traditional field clo- sures rather than plug-and-play technologies. "If you're looking at challenges and relative costs, hooking up fiber to a cell site is an easier proposition," he says. "Te ONT [optical network terminal] tends to be built into the fiber port on the base sta- tion. Te fiber looks like it's going inside a central office or a switching center with a fiber patch cord." FIBER TO THE ANTENNA Base station architectures are changing. Active antennas in macro cell sites now contain radios, and fiber cables carry digi- tal data from the base station at the bottom of a tower to the active antennas at the top, eliminating the heavy (and high- signal-loss) coaxial cables that run up towers today. Te fiber is combined in a single cable assembly with the power cable for the radios. Tis configuration saves space in the equipment cabinet at the base, allowing more options for location. In a small cell system, an active antenna is combined with a simple base station into one unit, which can be mounted al- most anywhere power and network connections are available, not just on a tower. Groups of small cells are connected by fiber to controllers in the network that manage them and also manage their coexistence with macro base stations. Still other base stations may be connected (again, via fiber) to a distrib- uted antenna system (DAS), yet another piece of the HetNet architecture for which TE offers solutions. Any base station has a limited amount of capacity, but small cells and DASs can increase that capacity by placing antennas closer to users, explains Shaddock. "In simple terms, imagine a base station with omnidirectional coverage," he continues. "As you get farther away from the center of the circle, the signal is decreasing, and the people at the edge of the cell get worse data performance. Conversely, if there are a lot of people at the edge, they're messing up service for the people in the middle. Te solution is to distribute antennas over the same area either with small cells or DASs." A DAS connects a centrally located base station to active antennas distributed around it. When signals are transported via fiber between a centralized base station and a remote an- tenna, which may be several miles away, they are digitized and then turned back into RF signals at the antenna. "Tat way, you can get coverage over a wide area without putting up a big cell tower," Shaddock says. Tis kind of setup is easily upgrad- able to 4G, so it is a future-proof investment. "Digital trans- port of RF doesn't care whether it's 3G or 4G," Shaddock says. "It just takes the signal and transports it. Tis lowers the total lifetime cost of the installation." Low-power DAS antennas are often used in stadiums, shopping malls, airports and campus environments, Shaddock explains – and he's excited about their future possibilities be- cause they offer a cost-effective way of adding capacity quickly, especially in places with very variable network usage. In a rural area, for example, a DAS may be used in the center of a small town. DASs are also becoming popular in places where aesthetics are paramount because they are much less obtrusive than cell towers. Tey can even be situated along highways that do not carry heavy traffic. "Rather than mount- ing a cell tower, you can put the base station at a convenient point and run fiber optic cables along the highway with a DAS and give yourself more coverage," Shaddock says. In the future, HetNets may automatically reconfigure themselves to meet changes in traffic. For example, in a down- town area or business park, as workers empty out of their office buildings at lunchtime, networks could reconfigure to shift capacity from the buildings to the streets; after lunch, when the capacity map changes again, the DAS could reconfigure to deliver more capacity inside the buildings. "It's still early days," says Shaddock. "I think there's a next generation of wireless that will allow flexible capacity." Y ::: */'6 &20 6$/(6#*/'6 &20 OCTOBER 2012 | www.broadbandcommunities.com | BROADBAND COMMUNITIES | 79