At the core of many enterprise wireless systems exists a network called a DAS or distributed antenna system. Typically a DAS is in place to spread or distribute signals throughout a building that is too large to cover with just one antenna head. You can think of a DAS as a wireless sprinkler system, able to spread wireless energy evenly over a large area, remembering that each antenna head is only able to cover a small area by itself. Relatively small areas that are on the order of 100,000 ft.² or less can typically be covered with a strong cellular repeater and a few antennas, maybe three to five fed with coaxial cables. This is called a “passive” distributed antenna system. Buildings with required coverage areas much larger than this will require a different type of DAS, one that can distribute R.F. (Radio Frequency) energy over much larger areas. This type of distributed antenna system is called an “active” DAS and can cover buildings up to two million square feet and even larger. The main difference between passive and active DAS is that passive does not require a powered antenna, is not easily expanded, and is relatively inexpensive. Active DAS requires powered antennas, is readily expandable, and generally more expensive. Obviously many factors come into play when defining the best DAS for a given application but three main elements are at the center of any decision for a given distributed antenna system deployment; 1) power, 2) cable type, and 3) frequency range.
Every active DAS has a limited amount of radio power it can provide to transmit from each antenna head in the network. Obviously the higher the individual antenna power capability, the fewer antennas needed to cover a given area. This general rule holds true up to a point where practical considerations of distance and area take over. The next factor is about what type of cable the DAS uses. Generally three main types exist; coaxial, fiber optic, or shielded category 5e/6 data cable. Both coaxial and Cat. 5e/6 systems generally send both power and radio signals across the same cable so only one cable is needed. Fiber based products use fiber optics for the radio signals and Cat. 5e/6 to carry power therefore they need two cables to operate.
The third prominent factor is the frequency range. As a general rule coaxial and data cable systems operate over relatively narrower frequencies than fiber systems. This is not always true so in some cases multiple cables are needed in order to serve 2G, 3G and 4G networks at the same time. Some innovative solutions can service many frequency bands simultaneously with one fiber optic cable. Such systems offer great promise in their scalability and flexibility, able to serve VHF, land mobile, LTE, cellular, PCS, advance wireless and WiFi across a common infrastructure. But with great flexibility come other trade-offs that must be considered when searching for the ideal solution.
Proximity Wireless has the expertise and experience to define the best distributed antenna system for your environment.