A Distributed Antenna System, or DAS, is a network of smaller, spatially separated antenna nodes connected to the communications network.
A DAS network splits the transmitted signal among several smaller antennas to provide coverage and reliability over the same area as a single cell tower antenna. DAS networks are effective in areas with difficult topography, structural impediments (e.g. buildings, or within buildings), or in locations where, for a variety of reasons, it is not optimal to build a traditional macro sites.
How AT&T is using small antennas to fix big problems | MuniWireless:
If all goes according to AT&T’s wishes, the city of Palo Alto may soon become the premier testing spot for Ma Bell’s plan to boost its cellular network power by installing a large number of small cellular antennas around town. Ostensibly billed as a method for AT&T to overcome terrestrial and urban challenges in Palo Alto, the small-antenna plan for Silicon Valley’s cultural nexus is also part of a big nationwide push of Distributed Antenna System (DAS) technology deployment by AT&T to help Ma Bell get its overtaxed cellular network back up to speed.
Historically used to improve cellular coverage inside buildings, DAS is basically a method to deploy a series of synchronized smaller antennas instead of a larger, cellular antenna array, such as those found atop buildings or on the unsightly antenna towers that are now a common part of the urban landscape. Inside a building, a DAS can help improve cellular reception by bringing small antennas closer to users inside, who then don’t have to connect their cell phones through walls or windows. A typical DAS system might then route the internal antenna connections to a stronger antenna connection on the roof to link to the parent cellular network, improving throughput while conserving device and antenna power.
In Palo Alto AT&T is proposing to build out about 80 new DAS tower sites, placing them atop regular utility poles in and around Palo Alto’s leafy downtown area. If the plan wins city approval Palo Alto’s AT&T customers should see marked improvement in cellular connectivity, simply due to the increased number of available towers that can connect iPhones and other devices back to AT&T’s network. According to AT&T’s extensive Palo Alto wireless information web site, the proposal has been submitted to the city but no decision has yet been made.