Cellular DAS and
Small Cells
Coverage and capacity solutions for in-building wireless networks
In the past decade, we have installed over one thousand two hundred Distributed Antenna System networks. (Yikes, that’s a lot - but that’s why we’re the benchmark in wireless!)
Our experience has allowed us to develop extensive consulting, engineering design and deployment capabilities that allows us to match the needs of service providers and their customers.
Cellular DAS
A DAS takes the radiofrequency (RF) signal from a standard third-party cellular base station and conveys it through a series of active and passive network elements via fiber, copper or coaxial cabling to an array of relatively low-power antennas throughout a building, venue or campus. Because the transmitting antennas may be located inside the building, they may deliver stronger signals than neighboring macro towers, whose transmissions must penetrate exterior and interior walls of the structure. The DAS base station also provides its own capacity, so intensive indoor use — for example in an airport or stadium — does not “rob” capacity from the surrounding macro network.
Small Cells
Traditionally deployed outdoors to supplement the macro network, small cells recently have been deployed for specific indoor and venue applications as well. These small cells are smaller, low-power versions of the larger “macro” base stations with their own radios and antennas that can be deployed indoors or around a building where coverage is needed. Small cells come in several types, but they can be grouped loosely into two categories, stand-alone and distributed. With stand-alone small cells, each access point is a fully self-contained base transceiver station (BTS) including a baseband unit (BBU), radio, and antenna. With distributed small cells, the baseband processing is mostly centralized for a large group of radio and antenna units distributed around the building.
A complete solution
Functionally, DAS and small cells solve the same problem, but their different architectures have important implications. Both DAS and small cells have now been in use for some time and as each evolves they have taken on the advantages of the other. Distributed small cells are more DAS-like in that they centralize the baseband processing and distribute the radio resources. Some DAS deployments, for their part, have begun using small cells as the RF signal source. In cases where the power and capacity of the small cell meet the venue’s requirements, small cells as a signal source can prove more cost-effective than DAS.
Types of DAS Signal Distribution Systems
Passive DAS
Uses passive radio frequency components like coaxial cables, splitters, taps, and couplers
Active DAS
Receives analog radio frequencies from the signal source., then a master unit converts the analog transmissions to digital signals. The digital signals are distributed through fiber optic or ethernet cables to remote radio units (RRUs). The RRUs convert digital signals back to analog.
Hybrid DAS
Is a mix between active and passive DAS. The distributed antenna system’s RRUs are separated from the antennas, enabling the use of both fiber optic and coaxial cables. RRUs on each floor convert digital signals to analog that connect to antennas on that floor via coaxial cables.
Digital Distributed DAS
Emerging technology and is relatively new under the Common Public Radio Interface (CPRI) specification. They use a Base Band Unit (BBU) to connect directly to a master unit without analog-to-digital conversions.
