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 National Fire Alarm Signaling Code (NFPA 72), NYC Building Code Chapter 9, and NYC Fire Department Rule 3. In effect all large buildings in New York must now have a dedicated wireless two-way communications system for fire department use (FDNY ARCS).[ citation needed ] These systems allow on-scene communications throughout a building of any size.[ citation needed ]
Path loss, or path attenuation, is the reduction in power density (attenuation) of an electromagnetic wave as it propagates through space. Path loss is a major component in the analysis and design of the link budget of a telecommunication system.
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.
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.
Effective radiated power (ERP), synonymous with equivalent radiated power, is an IEEE standardized definition of directional radio frequency (RF) power, such as that emitted by a radio transmitter. It is the total power in watts that would have to be radiated by a half-wave dipole antenna to give the same radiation intensity as the actual source antenna at a distant receiver located in the direction of the antenna's strongest beam. ERP measures the combination of the power emitted by the transmitter and the ability of the antenna to direct that power in a given direction. It is equal to the input power to the antenna multiplied by the gain of the antenna. It is used in electronics and telecommunications, particularly in broadcasting to quantify the apparent power of a broadcasting station experienced by listeners in its reception area.
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.
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.
A base transceiver station (BTS) is a piece of equipment that facilitates wireless communication between user equipment (UE) and a network. UEs are devices like mobile phones (handsets), WLL phones, computers with wireless Internet connectivity, or antennas mounted on buildings or telecommunication towers. The network can be that of any of the wireless communication technologies like GSM, CDMA, wireless local loop, Wi-Fi, WiMAX or other wide area network (WAN) technology.
Radio masts and towers are typically tall structures designed to support antennas for telecommunications and broadcasting, including television. There are two main types: guyed and self-supporting structures. They are among the tallest human-made structures. Masts are often named after the broadcasting organizations that originally built them or currently use them.
Antenna diversity, also known as space diversity or spatial diversity, is any one of several wireless diversity schemes that uses two or more antennas to improve the quality and reliability of a wireless link. Often, especially in urban and indoor environments, there is no clear line-of-sight (LOS) between transmitter and receiver. Instead the signal is reflected along multiple paths before finally being received. Each of these bounces can introduce phase shifts, time delays, attenuations, and distortions that can destructively interfere with one another at the aperture of the receiving antenna.
A leaky feeder is a communications system used in underground mining and other tunnel environments. Manufacturers and cabling professionals use the term "radiating cable" as this implies that the cable is designed to radiate: something that coaxial cable is not generally supposed to do.
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.
Microwave transmission is the transmission of information by electromagnetic waves with wavelengths in the microwave frequency range of 300 MHz to 300 GHz of the electromagnetic spectrum. Microwave signals are normally limited to the line of sight, so long-distance transmission using these signals requires a series of repeaters forming a microwave relay network. It is possible to use microwave signals in over-the-horizon communications using tropospheric scatter, but such systems are expensive and generally used only in specialist roles.
Due to economy of scale property of telecommunication industry, sharing of telecom infrastructure among telecom service providers is becoming the requirement and process of business in the telecom industry where competitors are becoming partners in order to lower their increasing investments. The degree and method of infrastructure sharing can vary in each country depending on regulatory and competitive climate.
Fixed wireless is the operation of wireless communication devices or systems used to connect two fixed locations with a radio or other wireless link, such as laser bridge. Usually, fixed wireless is part of a wireless LAN infrastructure. The purpose of a fixed wireless link is to enable data communications between the two sites or buildings. Fixed wireless data (FWD) links are often a cost-effective alternative to leasing fiber or installing cables between the buildings.
Radio is the technology of signaling and communicating using radio waves. Radio waves are electromagnetic waves of frequency between 3 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmitter connected to an antenna which radiates the waves, and received by another antenna connected to a radio receiver. Radio is widely used in modern technology, in radio communication, radar, radio navigation, remote control, remote sensing, and other applications.
Radio over fiber (RoF) or RF over fiber (RFoF) refers to a technology whereby light is modulated by a radio frequency signal and transmitted over an optical fiber link. Main technical advantages of using fiber optical links are lower transmission losses and reduced sensitivity to noise and electromagnetic interference compared to all-electrical signal transmission.
An in-building cellular enhancement system, commonly implemented in conjunction with a distributed antenna system (DAS), is a telecommunications solution which is used to extend and distribute the cellular signal of a given mobile network operator within a building. In the United States, operators commonly supported by such solutions include AT&T Mobility, Verizon Wireless, Sprint Corporation, T-Mobile US, in addition to smaller regional carriers as required. Below ground level, large buildings and high rises are examples where mobile phones are unable to properly reach the carrier's macro or outdoor network. In these environments, the in-building cellular enhancement system will connect to the carrier's signal source which is typically a bi-directional amplifier or a base transceiver station. This signal source transmits the mobile network operator's licensed radio frequency. This frequency is then transported within the building using coaxial cable, optical fiber or Category 5e/Category 6 twisted pair cable. In-building coverage antennas are strategically placed to provide the best overall coverage for users.
Small cells are low-powered cellular radio access nodes that operate in spectrum that have a range of 10 meters to a few kilometers. They are base stations with low power consumption and cheap cost. They can provide high data rates by being deployed densely to achieve high spatial spectrum efficiency.
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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