However, regulations have been getting promulgated at the state and federal level, with Midwest states leading the way with state level regulations. Historical regulatory challenges arise at the federal, state and municipal levels. Systems are also placed in the utility right of way on top of utility poles, street light poles and traffic signal poles. Often they are placed within large structures such as stadiums or corporate headquarters. Placement of distributed antenna systems ĭistributed antenna systems may be placed inside buildings for increasing wireless signals within buildings. It is estimated that only about 5% of commercial WiFi use a distributed antenna system. Using a distributed antenna system to create an area of wireless coverage, it is possible to use this technique to propagate indoor WiFi for commercial uses. Prior to the invention by Saleh et al., tunnel transmitters and leaky feeders had been used to provide radio reception in tunnels, mines, subway lines, and other indoor and underground spaces.

As an alternative, the total area covered could be extended for a given limit of effective radiated power, which may be important to ensure compliance with safety limits on radiation into the human body. If a given area is covered by many distributed antenna elements rather than a single antenna, then the total radiated power is reduced by approximately a factor N 1–n/2 and the power per antenna is reduced by a factor N n/2 where a simple power-law path-loss model with path-loss exponent n is assumed. This artificially increases delay spread in areas of overlapped coverage, permitting quality improvements via time diversity. In systems where equalization is applied, it may be desirable to introduce delays between the antenna elements. The idea works because less power is wasted in overcoming penetration and shadowing losses, and because a line-of-sight channel is present more frequently, leading to reduced fade depths and reduced delay spread.Ī distributed antenna system can be implemented using passive splitters and feeders, or active- repeater amplifiers can be included to overcome the feeder losses. DAS is often used in scenarios where alternate technologies are infeasible due to terrain or zoning challenges. These antennas have recently been employed by several service providers in many areas around the United States. The idea was described in a paper by Saleh et al. A single antenna radiating at high power (a) is replaced by a group of low-power antennas to cover the same area (b). 4 Placement of distributed antenna systemsĪs illustrated in the figure, the idea is to split the transmitted power among several antenna elements, separated in space so as to provide coverage over the same area as a single antenna but with reduced total power and improved reliability.

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