A distributed antenna system (DAS) is a network of spatially separated antenna nodes connected to a common source via a transport medium that provides wireless service within a geographic area or structure. DAS antenna elevations are generally at or below the clutter level, and node installations are compact. A distributed antenna system may be deployed indoors (an iDAS) or outdoors (an oDAS). [1]
As 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. A single antenna radiating at high power (a) is replaced by a group of low-power antennas to cover the same area (b). The idea was described in a paper by Saleh et al. [2] in 1987. These antennas have recently been employed by several service providers in many areas around the United States. DAS is often used in scenarios where alternate technologies are infeasible due to terrain or zoning challenges.
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.
A distributed antenna system can be implemented using passive splitters and feeders, or active-repeater amplifiers can be included to overcome the feeder losses. In systems where equalization is applied, it may be desirable to introduce delays between the antenna elements. This artificially increases delay spread in areas of overlapped coverage, permitting quality improvements via time diversity.
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 N1–n/2 and the power per antenna is reduced by a factor Nn/2 where a simple power-law path-loss model with path-loss exponent n is assumed. 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.
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.[ citation needed ]
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. It is estimated that only about 5% of commercial WiFi use a distributed antenna system. [3]
Distributed antenna systems may be placed inside buildings for increasing wireless signals within buildings. Often they are placed within large structures such as stadiums or corporate headquarters.
Systems are also placed in the utility right of way on top of utility poles, street light poles and traffic signal poles.
Historical regulatory challenges arise at the federal, state and municipal levels. However, regulations have been getting promulgated at the state and federal level, with Midwest states leading the way with state level regulations. [4] [5] Industry resources like The HetNet Forum (formerly The DAS Forum) also address regulatory issues in their conferences and communicate the outcome through their websites. [6]
Federal Communications Commission Rules: The FCC has promulgated the FCC Pole Attachment Order 11-50. [7]
Michigan : The METRO Authority, which regulates access to the utility right-of-way determined in 2004 that Distributed Antennae Network Systems are part of the landline infrastructure, and hence are subject to state regulation via an administrative determination. [8]
Ohio : The Public Utilities Commission of Ohio has issued a pole attachment rulings which require the utility to allow Distributed Antenna Systems in the utility right-of-way in August 2014.
New York: In the aftermath of the 9/11 attacks on the World Trade Center in New York, all public safety agencies understood the importance of radio systems. The solution was codified by the NYC Building Code Chapter 9, and NYC Fire Department Rule 3. All high-rise buildings in New York must have a dedicated wireless two-way communications system for fire department use. This system is called FDNY Auxiliary Radio Communication System (commonly Referred to as ARCS). [9] . Such systems are required under Section 907.2.13.2 of the New York City 2014 Building Code. These systems allow on-scene communications throughout a building of any size. [10]
The Industry designs and builds DAS systems in line with the joint operator document known as the Multi Carrier Forum (MCF). Currently the industry operates under MCF2018, although there was a draft released in 2023 for the next iteration to include 5G. It's important to note that the terminology in Australia to describe types of DAS somewhat differs to other regions. For example a 'Passive DAS" globally often refers to an offair repeater based system, whereas in Australia that is not the case.
In telecommunications, a repeater is an electronic device that receives a signal and retransmits it. Repeaters are used to extend transmissions so that the signal can cover longer distances or be received on the other side of an obstruction. Some types of repeaters broadcast an identical signal, but alter its method of transmission, for example, on another frequency or baud rate.
In telecommunication, especially radio communication, spread spectrum are techniques by which a signal generated with a particular bandwidth is deliberately spread in the frequency domain over a wider frequency band. Spread-spectrum techniques are used for the establishment of secure communications, increasing resistance to natural interference, noise, and jamming, to prevent detection, to limit power flux density, and to enable multiple-access communications.
Ultra high frequency (UHF) is the ITU designation for radio frequencies in the range between 300 megahertz (MHz) and 3 gigahertz (GHz), also known as the decimetre band as the wavelengths range from one meter to one tenth of a meter. Radio waves with frequencies above the UHF band fall into the super-high frequency (SHF) or microwave frequency range. Lower frequency signals fall into the VHF or lower bands. UHF radio waves propagate mainly by line of sight; they are blocked by hills and large buildings although the transmission through building walls is strong enough for indoor reception. They are used for television broadcasting, cell phones, satellite communication including GPS, personal radio services including Wi-Fi and Bluetooth, walkie-talkies, cordless phones, satellite phones, and numerous other applications.
Radio propagation is the behavior of radio waves as they travel, or are propagated, from one point to another in vacuum, or into various parts of the atmosphere. As a form of electromagnetic radiation, like light waves, radio waves are affected by the phenomena of reflection, refraction, diffraction, absorption, polarization, and scattering. Understanding the effects of varying conditions on radio propagation has many practical applications, from choosing frequencies for amateur radio communications, international shortwave broadcasters, to designing reliable mobile telephone systems, to radio navigation, to operation of radar systems.
The Family Radio Service (FRS) is an improved walkie-talkie radio system authorized in the United States since 1996. This personal radio service uses channelized frequencies around 462 and 467 MHz in the ultra high frequency (UHF) band. It does not suffer the interference effects found on citizens' band (CB) at 27 MHz, or the 49 MHz band also used by cordless telephones, toys, and baby monitors. FRS uses frequency modulation (FM) instead of amplitude modulation (AM). Since the UHF band has different radio propagation characteristics, short-range use of FRS may be more predictable than the more powerful license-free radios operating in the HF CB band.
Automatic meter reading (AMR) is the technology of automatically collecting consumption, diagnostic, and status data from water meter or energy metering devices and transferring that data to a central database for billing, troubleshooting, and analyzing. This technology mainly saves utility providers the expense of periodic trips to each physical location to read a meter. Another advantage is that billing can be based on near real-time consumption rather than on estimates based on past or predicted consumption. This timely information coupled with analysis can help both utility providers and customers better control the use and production of electric energy, gas usage, or water consumption.
The General Mobile Radio Service (GMRS) is a land-mobile FM UHF radio service designed for short-range two-way voice communication and authorized under part 95 of the US FCC code. It requires a license in the United States, but some GMRS compatible equipment can be used license-free in Canada. The US GMRS license is issued for a period of 10 years. The United States permits use by adult individuals who possess a valid GMRS license, as well as their immediate family members. Immediate relatives of the GMRS system licensee are entitled to communicate among themselves for personal or business purposes, but employees of the licensee who are not family members are not covered by the license. Non-family members must be licensed separately.
Base station is – according to the International Telecommunication Union's (ITU) Radio Regulations (RR) – a "land station in the land mobile service."
A cell site, cell phone tower, cell base tower, or cellular base station is a cellular-enabled mobile device site where antennas and electronic communications equipment are placed to create a cell, or adjacent cells, in a cellular network. The raised structure typically supports antenna and one or more sets of transmitter/receivers transceivers, digital signal processors, control electronics, a GPS receiver for timing, primary and backup electrical power sources, and sheltering.
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A cellular repeater is a type of bi-directional amplifier used to improve cell phone reception. A cellular repeater system commonly consists of a donor antenna that receives and transmits signal from nearby cell towers, coaxial cables, a signal amplifier, and an indoor rebroadcast antenna.
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Communications law refers to the regulation of electronic communications by wire or radio. It encompasses regulations governing broadcasting, telephone and telecommunications service, cable television, satellite communications, wireless telecommunications, and the Internet.
The Wireless Infrastructure Association (WIA), formerly known as PCIA, is an American trade association for wireless providers and companies that build cell phone towers, rooftop wireless sites, and other facilities that transmit wireless communication signals. The Washington Post described the industry as "the people who build all those cell towers so you can actually make those calls, download that data." These technologies are collectively referred to as "wireless telecommunications infrastructure."
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