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<span id="openzim-page-title" class="mw-page-title-main"><span class="mw-page-title-main">Distributed antenna system</span></span>

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<p>A <b>distributed antenna system</b> (<b>DAS</b>) is a network of spatially separated <a href="Antenna_(radio)" title="Antenna (radio)">antenna</a> 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 <a href="Clutter_(radar)" title="Clutter (radar)">clutter</a> level, and <a href="Node_(networking)" title="Node (networking)">node</a> installations are compact. A distributed antenna system may be deployed indoors (an iDAS) or outdoors (an oDAS).<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup>

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<div class="mw-heading mw-heading2"><h2 id="Concept">Concept</h2></div>

<p>As illustrated in the figure, the idea is to split the transmitted power among several <a href="Antenna_(radio)" title="Antenna (radio)">antenna</a> 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.<sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> 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.

</p><p>The idea works because less power is wasted in overcoming penetration and shadowing losses, and because a <a href="Line-of-sight_propagation" title="Line-of-sight propagation">line-of-sight</a> channel is present more frequently, leading to reduced <a href="Fading" title="Fading">fade depths</a> and reduced delay spread.

</p><p>A distributed antenna system can be implemented using passive <a href="DSL_filter" title="DSL filter">splitters</a> and feeders, or active-<a href="Repeater" title="Repeater">repeater</a> <a href="Amplifier" title="Amplifier">amplifiers</a> 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.

</p><p>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 <i>N</i><sup><i>1–n/2</i></sup> and the power per antenna is reduced by a factor <i>N</i><sup><i>n/2</i></sup> where a simple <a href="Power-law" class="mw-redirect" title="Power-law">power-law</a> <a href="Path_loss" title="Path loss">path-loss</a> model with path-loss exponent <i>n</i> 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 <a href="Radiation" title="Radiation">radiation</a> into the human body.

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<div class="mw-heading mw-heading2"><h2 id="Precursors">Precursors</h2></div>

<p>Prior to the invention by Saleh <i>et al.</i>, <a href="Tunnel_transmitter" title="Tunnel transmitter">tunnel transmitters</a> and <a href="Leaky_feeder" title="Leaky feeder">leaky feeders</a> had been used to provide radio reception in tunnels, mines, <a href="Rapid_transit" title="Rapid transit">subway</a> lines, and other indoor and underground spaces.

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<div class="mw-heading mw-heading2"><h2 id="Use_in_WiFi_networks">Use in WiFi networks</h2></div>

<p>Using a distributed antenna system to create an area of wireless coverage, it is possible to use this technique to propagate indoor <a href="WiFi" class="mw-redirect" title="WiFi">WiFi</a> for commercial uses. It is estimated that only about 5% of commercial WiFi use a distributed antenna system.<sup id="cite_ref-3" class="reference"><a href="#cite_note-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup>

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<div class="mw-heading mw-heading2"><h2 id="Placement_of_distributed_antenna_systems">Placement of distributed antenna systems</h2></div>

<p>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.

</p><p>Systems are also placed in the utility right of way on top of utility poles, street light poles and traffic signal poles.

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<div class="mw-heading mw-heading2"><h2 id="Regulations">Regulations</h2></div>

<div class="mw-heading mw-heading3"><h3 id="United_States">United States</h3></div>

<p>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.<sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-5" class="reference"><a href="#cite_note-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> Industry resources like <a href="PCIA_-_The_Wireless_Infrastructure_Association" class="mw-redirect" title="PCIA - The Wireless Infrastructure Association">The HetNet Forum</a> (formerly The DAS Forum) also address regulatory issues in their conferences and communicate the outcome through their websites.<sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup>

</p><p><a href="Federal_Communications_Commission" title="Federal Communications Commission">Federal Communications Commission</a> Rules: The FCC has promulgated the FCC Pole Attachment Order 11-50.<sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup>

</p><p><b><a href="Michigan" title="Michigan">Michigan</a></b>: The METRO Authority, which regulates access to the utility right-of-way determined in 2004 that Distributed Antennae Network Systems are part of the <a href="Landline" title="Landline">landline</a> infrastructure, and hence are subject to state regulation via an administrative determination.<sup id="cite_ref-8" class="reference"><a href="#cite_note-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup>

</p><p><b><a href="Ohio" title="Ohio">Ohio</a></b>: The <a href="Public_Utilities_Commission_of_Ohio" title="Public Utilities Commission of Ohio">Public Utilities Commission of Ohio</a> has issued a pole attachment rulings which require the utility to allow Distributed Antenna Systems in the utility right-of-way in August 2014.

</p><p><a href="New_York_City" title="New York City"><b>New York</b></a>: 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 <a href="Tower_block" title="Tower block">high-rise buildings</a> in New York must have a dedicated wireless two-way communications system for fire department use. This system is called <a href="New_York_City_Fire_Department" title="New York City Fire Department">FDNY</a> Auxiliary Radio Communication System (commonly Referred to as ARCS).<sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> 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.<sup id="cite_ref-10" class="reference"><a href="#cite_note-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup>

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<div class="mw-heading mw-heading3"><h3 id="Australia">Australia</h3></div>

<p>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 <a rel="nofollow" class="external text" href="https://wirelesscoverage.com.au/mcf2025-das/">MCF2025</a>, although there was a 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 <a rel="nofollow" class="external text" href="https://wirelesscoverage.com.au/active-das-distributed-antenna-system/">case</a>.

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<ul><li><a href="Macrodiversity" title="Macrodiversity">Macrodiversity</a></li>

<li><a href="Microconnect_distributed_antenna" title="Microconnect distributed antenna">Microconnect distributed antenna</a></li></ul>

<div class="mw-heading mw-heading2"><h2 id="References">References</h2></div>

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.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("./mw/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("./mw/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("./mw/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("./mw/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}

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</style><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.waveform.com/pages/das-distributed-antenna-systems">"The Complete Guide to Distributed Antenna Systems (DAS)"</a>.</cite></span>

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<li id="cite_note-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-2">^</a></b></span> <span class="reference-text">A. A. M. Saleh, A. J. Rustako and R. S. Roman, <a rel="nofollow" class="external text" href="https://ieeexplore.ieee.org/document/1096716/;jsessionid=246066223E2E463D991A75972152CE90?arnumber=1096716">Distributed Antennas for Indoor Radio Communications</a>, <i>IEEE Transactions on Commun.</i>, vol. 35, pp. 1245-1251, Dec. 1987</span>

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<li id="cite_note-3"><span class="mw-cite-backlink"><b><a href="#cite_ref-3">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20160303223227/http://lcommglobal.com/Distrubuted_Antenna.php">"Estimate made by LComm Global"</a>. Lcommglobal.com. Archived from <a rel="nofollow" class="external text" href="http://lcommglobal.com/Distrubuted_Antenna.php">the original</a> on 2016-03-03<span class="reference-accessdate">. Retrieved <span class="nowrap">2012-10-24</span></span>.</cite></span>

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<li id="cite_note-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-4">^</a></b></span> <span class="reference-text"><cite id="CITEREFKannan_Ramachandran2008" class="citation web cs1">Kannan Ramachandran, Srividya (15 July 2008). "Establishing a Regulatory Framework for Distributed Antenna Systems". Ssrn.com. <a href="SSRN_(identifier)" class="mw-redirect" title="SSRN (identifier)">SSRN</a> <a rel="nofollow" class="external text" href="https://papers.ssrn.com/sol3/papers.cfm?abstract_id=1161209">1161209</a>.</cite> <span class="cs1-visible-error citation-comment"><code class="cs1-code">{{cite web}}</code>: </span><span class="cs1-visible-error citation-comment">Missing or empty <code class="cs1-code">|url=</code> (help)</span></span>

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<li id="cite_note-5"><span class="mw-cite-backlink"><b><a href="#cite_ref-5">^</a></b></span> <span class="reference-text"><cite id="CITEREFRamachandran2009" class="citation book cs1">Ramachandran, Srividya Kannan (June 2009). <i>Distributed Antenna Systems - Establishing a Regulatory Framework Available</i>. VDM. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-3639168839</bdi>.</cite></span>

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<li id="cite_note-6"><span class="mw-cite-backlink"><b><a href="#cite_ref-6">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://TheDASForum.org">"The Distributed Antenna Systems Online Community"</a>. The DAS Forum. 2012-08-17<span class="reference-accessdate">. Retrieved <span class="nowrap">2012-08-22</span></span>.</cite></span>

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<li id="cite_note-7"><span class="mw-cite-backlink"><b><a href="#cite_ref-7">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://apps.fcc.gov/edocs_public/attachmatch/FCC-11-50A1.pdf">"FCC Order 11-50"</a> <span class="cs1-format">(PDF)</span>. FCC<span class="reference-accessdate">. Retrieved <span class="nowrap">2014-09-25</span></span>.</cite></span>

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<li id="cite_note-8"><span class="mw-cite-backlink"><b><a href="#cite_ref-8">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.michigan.gov/documents/Distributed_Antennae_Network_Systems_126177_7.pdf">"Metro Authority Determination Number 1"</a> <span class="cs1-format">(PDF)</span>. www.michigan.gov<span class="reference-accessdate">. Retrieved <span class="nowrap">2014-09-24</span></span>.</cite></span>

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<li id="cite_note-9"><span class="mw-cite-backlink"><b><a href="#cite_ref-9">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.nyc.gov/site/fdny/business/all-certifications/certificates-auxiliary-radio-comm.page">"certificates-auxiliary-radio-comm"</a>. <i>www.nyc.gov</i><span class="reference-accessdate">. Retrieved <span class="nowrap">2024-07-18</span></span>.</cite></span>

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<li id="cite_note-10"><span class="mw-cite-backlink"><b><a href="#cite_ref-10">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://nyc-business.nyc.gov/nycbusiness/description/auxiliary-radio-communication-system-application">"Auxiliary Radio Communication System Application | City of New York"</a>. <i>nyc-business.nyc.gov</i><span class="reference-accessdate">. Retrieved <span class="nowrap">2024-07-18</span></span>.</cite></span>

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