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vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Steps_in_CDMA_modulation"> <div class="vector-toc-text"> <span class="vector-toc-numb">3</span> <span>Steps in CDMA modulation</span> </div> </a> <ul id="toc-Steps_in_CDMA_modulation-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Code-division_multiplexing_(synchronous_CDMA)" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Code-division_multiplexing_(synchronous_CDMA)"> <div class="vector-toc-text"> <span class="vector-toc-numb">4</span> <span>Code-division multiplexing (synchronous CDMA)</span> </div> </a> <button aria-controls="toc-Code-division_multiplexing_(synchronous_CDMA)-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Code-division multiplexing (synchronous CDMA) subsection</span> </button> <ul id="toc-Code-division_multiplexing_(synchronous_CDMA)-sublist" class="vector-toc-list"> <li id="toc-Example" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Example"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.1</span> <span>Example</span> </div> </a> <ul id="toc-Example-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Asynchronous_CDMA" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Asynchronous_CDMA"> <div class="vector-toc-text"> <span class="vector-toc-numb">5</span> <span>Asynchronous CDMA</span> </div> </a> <button aria-controls="toc-Asynchronous_CDMA-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Asynchronous CDMA subsection</span> </button> <ul id="toc-Asynchronous_CDMA-sublist" class="vector-toc-list"> <li id="toc-Advantages_of_asynchronous_CDMA_over_other_techniques" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Advantages_of_asynchronous_CDMA_over_other_techniques"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.1</span> <span>Advantages of asynchronous CDMA over other techniques</span> </div> </a> <ul id="toc-Advantages_of_asynchronous_CDMA_over_other_techniques-sublist" class="vector-toc-list"> <li id="toc-Efficient_practical_utilization_of_the_fixed_frequency_spectrum" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Efficient_practical_utilization_of_the_fixed_frequency_spectrum"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.1.1</span> <span>Efficient practical utilization of the fixed frequency spectrum</span> </div> </a> <ul id="toc-Efficient_practical_utilization_of_the_fixed_frequency_spectrum-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Flexible_allocation_of_resources" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Flexible_allocation_of_resources"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.1.2</span> <span>Flexible allocation of resources</span> </div> </a> <ul id="toc-Flexible_allocation_of_resources-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Spread-spectrum_characteristics_of_CDMA" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Spread-spectrum_characteristics_of_CDMA"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.2</span> <span>Spread-spectrum characteristics of CDMA</span> </div> </a> <ul id="toc-Spread-spectrum_characteristics_of_CDMA-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Collaborative_CDMA" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Collaborative_CDMA"> <div class="vector-toc-text"> <span class="vector-toc-numb">6</span> <span>Collaborative CDMA</span> </div> </a> <ul id="toc-Collaborative_CDMA-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-See_also" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#See_also"> <div class="vector-toc-text"> <span class="vector-toc-numb">7</span> <span>See also</span> </div> </a> <ul id="toc-See_also-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Notes" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Notes"> <div class="vector-toc-text"> <span class="vector-toc-numb">8</span> <span>Notes</span> </div> </a> <ul id="toc-Notes-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-References" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#References"> <div class="vector-toc-text"> <span class="vector-toc-numb">9</span> <span>References</span> </div> </a> <ul id="toc-References-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Further_reading" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Further_reading"> <div class="vector-toc-text"> <span class="vector-toc-numb">10</span> <span>Further reading</span> </div> </a> <ul id="toc-Further_reading-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-External_links" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#External_links"> <div class="vector-toc-text"> <span class="vector-toc-numb">11</span> <span>External links</span> </div> </a> <ul id="toc-External_links-sublist" class="vector-toc-list"> </ul> </li> </ul> </div> </div> </nav> </div> </div> <div class="mw-content-container"> <main id="content" class="mw-body"> <header class="mw-body-header vector-page-titlebar"> <nav aria-label="Contents" class="vector-toc-landmark"> <div id="vector-page-titlebar-toc" class="vector-dropdown vector-page-titlebar-toc vector-button-flush-left" title="Table of Contents" > <input type="checkbox" id="vector-page-titlebar-toc-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-page-titlebar-toc" class="vector-dropdown-checkbox " aria-label="Toggle the table of contents" > <label id="vector-page-titlebar-toc-label" for="vector-page-titlebar-toc-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-listBullet mw-ui-icon-wikimedia-listBullet"></span> <span class="vector-dropdown-label-text">Toggle the table of contents</span> </label> <div class="vector-dropdown-content"> <div id="vector-page-titlebar-toc-unpinned-container" class="vector-unpinned-container"> </div> </div> </div> </nav> <h1 id="firstHeading" class="firstHeading mw-first-heading"><span class="mw-page-title-main">Code-division multiple access</span></h1> <div id="p-lang-btn" class="vector-dropdown mw-portlet mw-portlet-lang" > <input type="checkbox" id="p-lang-btn-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-p-lang-btn" class="vector-dropdown-checkbox mw-interlanguage-selector" aria-label="Go to an article in another language. Available in 36 languages" > <label id="p-lang-btn-label" for="p-lang-btn-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--action-progressive mw-portlet-lang-heading-36" aria-hidden="true" ><span class="vector-icon mw-ui-icon-language-progressive mw-ui-icon-wikimedia-language-progressive"></span> <span class="vector-dropdown-label-text">36 languages</span> </label> <div class="vector-dropdown-content"> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li class="interlanguage-link interwiki-ar mw-list-item"><a href="https://ar.wikipedia.org/wiki/%D9%88%D8%B5%D9%88%D9%84_%D9%85%D8%AA%D8%B9%D8%AF%D8%AF_%D8%A8%D8%AA%D9%82%D8%B3%D9%8A%D9%85_%D8%A7%D9%84%D8%AA%D8%B1%D9%85%D9%8A%D8%B2" title="وصول متعدد بتقسيم الترميز – Arabic" lang="ar" hreflang="ar" data-title="وصول متعدد بتقسيم الترميز" data-language-autonym="العربية" data-language-local-name="Arabic" class="interlanguage-link-target"><span>العربية</span></a></li><li class="interlanguage-link interwiki-bn mw-list-item"><a href="https://bn.wikipedia.org/wiki/%E0%A6%95%E0%A7%8B%E0%A6%A1_%E0%A6%A1%E0%A6%BF%E0%A6%AD%E0%A6%BF%E0%A6%B6%E0%A6%A8_%E0%A6%AE%E0%A6%BE%E0%A6%B2%E0%A7%8D%E0%A6%9F%E0%A6%BF%E0%A6%AA%E0%A7%8D%E2%80%8C%E0%A6%B2_%E0%A6%85%E0%A7%8D%E0%A6%AF%E0%A6%BE%E0%A6%95%E0%A7%8D%E2%80%8C%E0%A6%B8%E0%A7%87%E0%A6%B8" title="কোড ডিভিশন মাল্টিপ্‌ল অ্যাক্‌সেস – Bangla" lang="bn" hreflang="bn" data-title="কোড ডিভিশন মাল্টিপ্‌ল অ্যাক্‌সেস" data-language-autonym="বাংলা" data-language-local-name="Bangla" class="interlanguage-link-target"><span>বাংলা</span></a></li><li class="interlanguage-link interwiki-ca mw-list-item"><a href="https://ca.wikipedia.org/wiki/CDMA" title="CDMA – Catalan" lang="ca" hreflang="ca" data-title="CDMA" data-language-autonym="Català" data-language-local-name="Catalan" class="interlanguage-link-target"><span>Català</span></a></li><li class="interlanguage-link interwiki-cs mw-list-item"><a href="https://cs.wikipedia.org/wiki/K%C3%B3dov%C3%BD_multiplex" title="Kódový multiplex – Czech" lang="cs" hreflang="cs" data-title="Kódový multiplex" data-language-autonym="Čeština" data-language-local-name="Czech" class="interlanguage-link-target"><span>Čeština</span></a></li><li class="interlanguage-link interwiki-de mw-list-item"><a href="https://de.wikipedia.org/wiki/Codemultiplexverfahren" title="Codemultiplexverfahren – German" lang="de" hreflang="de" data-title="Codemultiplexverfahren" data-language-autonym="Deutsch" data-language-local-name="German" class="interlanguage-link-target"><span>Deutsch</span></a></li><li class="interlanguage-link interwiki-et mw-list-item"><a href="https://et.wikipedia.org/wiki/Koodjaotusega_hulgip%C3%B6%C3%B6rdus" title="Koodjaotusega hulgipöördus – Estonian" lang="et" hreflang="et" data-title="Koodjaotusega hulgipöördus" data-language-autonym="Eesti" data-language-local-name="Estonian" class="interlanguage-link-target"><span>Eesti</span></a></li><li class="interlanguage-link interwiki-es mw-list-item"><a href="https://es.wikipedia.org/wiki/Acceso_m%C3%BAltiple_por_divisi%C3%B3n_de_c%C3%B3digo" title="Acceso múltiple por división de código – Spanish" lang="es" hreflang="es" data-title="Acceso múltiple por división de código" data-language-autonym="Español" data-language-local-name="Spanish" class="interlanguage-link-target"><span>Español</span></a></li><li class="interlanguage-link interwiki-fa mw-list-item"><a href="https://fa.wikipedia.org/wiki/%D8%AF%D8%B3%D8%AA%D8%B1%D8%B3%DB%8C_%DA%86%D9%86%D8%AF%DA%AF%D8%A7%D9%86%D9%87_%D8%AA%D9%82%D8%B3%DB%8C%D9%85_%DA%A9%D8%AF%DB%8C" title="دسترسی چندگانه تقسیم کدی – Persian" lang="fa" hreflang="fa" data-title="دسترسی چندگانه تقسیم کدی" data-language-autonym="فارسی" data-language-local-name="Persian" class="interlanguage-link-target"><span>فارسی</span></a></li><li class="interlanguage-link interwiki-fr mw-list-item"><a href="https://fr.wikipedia.org/wiki/Code_division_multiple_access" title="Code division multiple access – French" lang="fr" hreflang="fr" data-title="Code division multiple access" data-language-autonym="Français" data-language-local-name="French" class="interlanguage-link-target"><span>Français</span></a></li><li class="interlanguage-link interwiki-ko mw-list-item"><a href="https://ko.wikipedia.org/wiki/%EC%BD%94%EB%93%9C%EB%B6%84%ED%95%A0%EB%8B%A4%EC%A4%91%EC%A0%91%EC%86%8D" title="코드분할다중접속 – Korean" lang="ko" hreflang="ko" data-title="코드분할다중접속" data-language-autonym="한국어" data-language-local-name="Korean" class="interlanguage-link-target"><span>한국어</span></a></li><li class="interlanguage-link interwiki-hi mw-list-item"><a href="https://hi.wikipedia.org/wiki/%E0%A4%95%E0%A5%8B%E0%A4%A1_%E0%A4%A1%E0%A4%BF%E0%A4%B5%E0%A5%80%E0%A4%9C%E0%A4%A8_%E0%A4%AE%E0%A4%B2%E0%A5%8D%E0%A4%9F%E0%A5%80%E0%A4%AA%E0%A4%B2_%E0%A4%8F%E0%A4%95%E0%A5%8D%E0%A4%B8%E0%A5%87%E0%A4%B8" title="कोड डिवीजन मल्टीपल एक्सेस – Hindi" lang="hi" hreflang="hi" data-title="कोड डिवीजन मल्टीपल एक्सेस" data-language-autonym="हिन्दी" data-language-local-name="Hindi" class="interlanguage-link-target"><span>हिन्दी</span></a></li><li class="interlanguage-link interwiki-id mw-list-item"><a href="https://id.wikipedia.org/wiki/CDMA" title="CDMA – Indonesian" lang="id" hreflang="id" data-title="CDMA" data-language-autonym="Bahasa Indonesia" data-language-local-name="Indonesian" class="interlanguage-link-target"><span>Bahasa Indonesia</span></a></li><li class="interlanguage-link interwiki-it mw-list-item"><a href="https://it.wikipedia.org/wiki/Code_division_multiple_access" title="Code division multiple access – Italian" lang="it" hreflang="it" data-title="Code division multiple access" data-language-autonym="Italiano" data-language-local-name="Italian" class="interlanguage-link-target"><span>Italiano</span></a></li><li class="interlanguage-link interwiki-he mw-list-item"><a href="https://he.wikipedia.org/wiki/CDMA" title="CDMA – Hebrew" lang="he" hreflang="he" data-title="CDMA" data-language-autonym="עברית" data-language-local-name="Hebrew" class="interlanguage-link-target"><span>עברית</span></a></li><li class="interlanguage-link interwiki-ka mw-list-item"><a href="https://ka.wikipedia.org/wiki/CDMA" title="CDMA – Georgian" lang="ka" hreflang="ka" data-title="CDMA" data-language-autonym="ქართული" data-language-local-name="Georgian" class="interlanguage-link-target"><span>ქართული</span></a></li><li class="interlanguage-link interwiki-lv mw-list-item"><a href="https://lv.wikipedia.org/wiki/Koddales_daudzpiek%C4%BCuve" title="Koddales daudzpiekļuve – Latvian" lang="lv" hreflang="lv" data-title="Koddales daudzpiekļuve" data-language-autonym="Latviešu" data-language-local-name="Latvian" class="interlanguage-link-target"><span>Latviešu</span></a></li><li class="interlanguage-link interwiki-hu mw-list-item"><a href="https://hu.wikipedia.org/wiki/K%C3%B3doszt%C3%A1sos_t%C3%B6bbsz%C3%B6r%C3%B6s_hozz%C3%A1f%C3%A9r%C3%A9s" title="Kódosztásos többszörös hozzáférés – Hungarian" lang="hu" hreflang="hu" data-title="Kódosztásos többszörös hozzáférés" data-language-autonym="Magyar" data-language-local-name="Hungarian" class="interlanguage-link-target"><span>Magyar</span></a></li><li class="interlanguage-link interwiki-xmf mw-list-item"><a href="https://xmf.wikipedia.org/wiki/CDMA" title="CDMA – Mingrelian" lang="xmf" hreflang="xmf" data-title="CDMA" data-language-autonym="მარგალური" data-language-local-name="Mingrelian" class="interlanguage-link-target"><span>მარგალური</span></a></li><li class="interlanguage-link interwiki-my mw-list-item"><a href="https://my.wikipedia.org/wiki/%E1%80%85%E1%80%AE%E1%80%92%E1%80%AE%E1%80%A1%E1%80%99%E1%80%BA%E1%80%A1%E1%80%B1" title="စီဒီအမ်အေ – Burmese" lang="my" hreflang="my" data-title="စီဒီအမ်အေ" data-language-autonym="မြန်မာဘာသာ" data-language-local-name="Burmese" class="interlanguage-link-target"><span>မြန်မာဘာသာ</span></a></li><li class="interlanguage-link interwiki-nl mw-list-item"><a href="https://nl.wikipedia.org/wiki/Code-division_multiple_access" title="Code-division multiple access – Dutch" lang="nl" hreflang="nl" data-title="Code-division multiple access" data-language-autonym="Nederlands" data-language-local-name="Dutch" class="interlanguage-link-target"><span>Nederlands</span></a></li><li class="interlanguage-link interwiki-ja mw-list-item"><a href="https://ja.wikipedia.org/wiki/%E7%AC%A6%E5%8F%B7%E5%88%86%E5%89%B2%E5%A4%9A%E5%85%83%E6%8E%A5%E7%B6%9A" title="符号分割多元接続 – Japanese" lang="ja" hreflang="ja" data-title="符号分割多元接続" data-language-autonym="日本語" data-language-local-name="Japanese" class="interlanguage-link-target"><span>日本語</span></a></li><li class="interlanguage-link interwiki-pl mw-list-item"><a href="https://pl.wikipedia.org/wiki/CDMA" title="CDMA – Polish" lang="pl" hreflang="pl" data-title="CDMA" data-language-autonym="Polski" data-language-local-name="Polish" class="interlanguage-link-target"><span>Polski</span></a></li><li class="interlanguage-link interwiki-pt mw-list-item"><a href="https://pt.wikipedia.org/wiki/CDMA" title="CDMA – Portuguese" lang="pt" hreflang="pt" data-title="CDMA" data-language-autonym="Português" data-language-local-name="Portuguese" class="interlanguage-link-target"><span>Português</span></a></li><li class="interlanguage-link interwiki-ro mw-list-item"><a href="https://ro.wikipedia.org/wiki/CDMA" title="CDMA – Romanian" lang="ro" hreflang="ro" data-title="CDMA" data-language-autonym="Română" data-language-local-name="Romanian" class="interlanguage-link-target"><span>Română</span></a></li><li class="interlanguage-link interwiki-ru mw-list-item"><a href="https://ru.wikipedia.org/wiki/CDMA" title="CDMA – Russian" lang="ru" hreflang="ru" data-title="CDMA" data-language-autonym="Русский" data-language-local-name="Russian" class="interlanguage-link-target"><span>Русский</span></a></li><li class="interlanguage-link interwiki-su mw-list-item"><a href="https://su.wikipedia.org/wiki/CDMA" title="CDMA – Sundanese" lang="su" hreflang="su" data-title="CDMA" data-language-autonym="Sunda" data-language-local-name="Sundanese" class="interlanguage-link-target"><span>Sunda</span></a></li><li class="interlanguage-link interwiki-fi mw-list-item"><a href="https://fi.wikipedia.org/wiki/CDMA" title="CDMA – Finnish" lang="fi" hreflang="fi" data-title="CDMA" data-language-autonym="Suomi" data-language-local-name="Finnish" class="interlanguage-link-target"><span>Suomi</span></a></li><li class="interlanguage-link interwiki-sv mw-list-item"><a href="https://sv.wikipedia.org/wiki/CDMA" title="CDMA – Swedish" lang="sv" hreflang="sv" data-title="CDMA" data-language-autonym="Svenska" data-language-local-name="Swedish" class="interlanguage-link-target"><span>Svenska</span></a></li><li class="interlanguage-link interwiki-ta mw-list-item"><a href="https://ta.wikipedia.org/wiki/%E0%AE%9A%E0%AE%BF%E0%AE%9F%E0%AE%BF%E0%AE%8E%E0%AE%AE%E0%AF%8D%E0%AE%8F" title="சிடிஎம்ஏ – Tamil" lang="ta" hreflang="ta" data-title="சிடிஎம்ஏ" data-language-autonym="தமிழ்" data-language-local-name="Tamil" class="interlanguage-link-target"><span>தமிழ்</span></a></li><li class="interlanguage-link interwiki-th mw-list-item"><a href="https://th.wikipedia.org/wiki/Code_division_multiple_access" title="Code division multiple access – Thai" lang="th" hreflang="th" data-title="Code division multiple access" data-language-autonym="ไทย" data-language-local-name="Thai" class="interlanguage-link-target"><span>ไทย</span></a></li><li class="interlanguage-link interwiki-tr mw-list-item"><a href="https://tr.wikipedia.org/wiki/CDMA" title="CDMA – Turkish" lang="tr" hreflang="tr" data-title="CDMA" data-language-autonym="Türkçe" data-language-local-name="Turkish" class="interlanguage-link-target"><span>Türkçe</span></a></li><li class="interlanguage-link interwiki-uk mw-list-item"><a href="https://uk.wikipedia.org/wiki/Code_Division_Multiple_Access" title="Code Division Multiple Access – Ukrainian" lang="uk" hreflang="uk" data-title="Code Division Multiple Access" data-language-autonym="Українська" data-language-local-name="Ukrainian" class="interlanguage-link-target"><span>Українська</span></a></li><li class="interlanguage-link interwiki-ur mw-list-item"><a href="https://ur.wikipedia.org/wiki/%D8%B3%DB%8C_%DA%88%DB%8C_%D8%A7%DB%8C%D9%85_%D8%A7%DB%92" title="سی ڈی ایم اے – Urdu" lang="ur" hreflang="ur" data-title="سی ڈی ایم اے" data-language-autonym="اردو" data-language-local-name="Urdu" class="interlanguage-link-target"><span>اردو</span></a></li><li class="interlanguage-link interwiki-vi mw-list-item"><a href="https://vi.wikipedia.org/wiki/%C4%90a_truy_c%E1%BA%ADp_ph%C3%A2n_chia_theo_m%C3%A3" title="Đa truy cập phân chia theo mã – Vietnamese" lang="vi" hreflang="vi" data-title="Đa truy cập phân chia theo mã" 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dir="ltr"><div class="shortdescription nomobile noexcerpt noprint searchaux" style="display:none">Channel access method used by various radio communication technologies</div> <style data-mw-deduplicate="TemplateStyles:r1236090951">.mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}}</style><div role="note" class="hatnote navigation-not-searchable">This article is about a channel access method. For the mobile phone technology referred to as CDMA, see <a href="/wiki/CdmaOne" title="CdmaOne">cdmaOne</a> and <a href="/wiki/CDMA2000" title="CDMA2000">CDMA2000</a>.</div> <style data-mw-deduplicate="TemplateStyles:r1129693374">.mw-parser-output .hlist dl,.mw-parser-output .hlist ol,.mw-parser-output .hlist ul{margin:0;padding:0}.mw-parser-output .hlist dd,.mw-parser-output .hlist dt,.mw-parser-output .hlist li{margin:0;display:inline}.mw-parser-output .hlist.inline,.mw-parser-output .hlist.inline dl,.mw-parser-output .hlist.inline ol,.mw-parser-output .hlist.inline ul,.mw-parser-output .hlist dl dl,.mw-parser-output .hlist dl ol,.mw-parser-output .hlist dl ul,.mw-parser-output .hlist ol dl,.mw-parser-output .hlist ol ol,.mw-parser-output .hlist ol ul,.mw-parser-output .hlist ul dl,.mw-parser-output .hlist ul ol,.mw-parser-output .hlist ul ul{display:inline}.mw-parser-output .hlist .mw-empty-li{display:none}.mw-parser-output .hlist dt::after{content:": "}.mw-parser-output .hlist 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.sidebar-title-with-pretitle a{color:var(--color-progressive)!important}}@media print{body.ns-0 .mw-parser-output .sidebar{display:none!important}}</style><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><style data-mw-deduplicate="TemplateStyles:r886047488">.mw-parser-output .nobold{font-weight:normal}</style><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886047488"><table class="sidebar nomobile nowraplinks plainlist"><tbody><tr><th class="sidebar-title" style="background:#bdb; display:block;margin-bottom:0.5em;"><a href="/wiki/Multiplexing" title="Multiplexing">Multiplexing</a></th></tr><tr><td class="sidebar-image"><span typeof="mw:File"><a href="/wiki/File:Multiplexing_diagram.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/6/6f/Multiplexing_diagram.svg/150px-Multiplexing_diagram.svg.png" decoding="async" width="150" height="106" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/6/6f/Multiplexing_diagram.svg/225px-Multiplexing_diagram.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/6/6f/Multiplexing_diagram.svg/300px-Multiplexing_diagram.svg.png 2x" data-file-width="512" data-file-height="362" /></a></span></td></tr><tr><th class="sidebar-heading" style="background:#cfc;"> <a href="/wiki/Modulation#Analog_modulation_methods" title="Modulation">Analog modulation</a></th></tr><tr><td class="sidebar-content" style="padding:0.15em 1.0em 0.8em;"> <div class="hlist"> <ul><li><a href="/wiki/Amplitude_modulation" title="Amplitude modulation">AM</a></li> <li><a href="/wiki/Frequency_modulation" title="Frequency modulation">FM</a></li> <li><a href="/wiki/Phase_modulation" title="Phase modulation">PM</a></li> <li><a href="/wiki/Quadrature_amplitude_modulation" title="Quadrature amplitude modulation">QAM</a></li> <li><a href="/wiki/Space_modulation" title="Space modulation">SM</a></li> <li><a href="/wiki/Single-sideband_modulation" title="Single-sideband modulation">SSB</a></li></ul> </div></td> </tr><tr><th class="sidebar-heading" style="background:#cfc;"> <div style="display: inline-block; line-height: 1.2em; padding: .1em 0;"><a href="/wiki/Circuit_switching" title="Circuit switching">Circuit mode<br /><span class="nobold">(constant bandwidth)</span></a></div></th></tr><tr><td class="sidebar-content" style="padding:0.15em 1.0em 0.8em;"> <div class="hlist"> <ul><li><a href="/wiki/Time-division_multiplexing" title="Time-division multiplexing">TDM</a></li> <li><a href="/wiki/Frequency-division_multiplexing" title="Frequency-division multiplexing">FDM</a> / <a href="/wiki/Wavelength-division_multiplexing" title="Wavelength-division multiplexing">WDM</a></li> <li><a href="/wiki/Space-division_multiple_access" title="Space-division multiple access">SDMA</a></li> <li><a href="/wiki/Polarization-division_multiplexing" title="Polarization-division multiplexing">Polarization</a></li> <li><a href="/wiki/Spatial_multiplexing" title="Spatial multiplexing">Spatial</a></li> <li><a href="/wiki/Orbital_angular_momentum_multiplexing" title="Orbital angular momentum multiplexing">OAM</a></li></ul> </div></td> </tr><tr><th class="sidebar-heading" style="background:#cfc;"> <div style="display: inline-block; line-height: 1.2em; padding: .1em 0;"><a href="/wiki/Statistical_multiplexing" class="mw-redirect" title="Statistical multiplexing">Statistical multiplexing<br /><span class="nobold">(variable bandwidth)</span></a></div></th></tr><tr><td class="sidebar-content" style="padding:0.15em 1.0em 0.8em;"> <div class="hlist"> <ul><li><a href="/wiki/Packet_switching" title="Packet switching">Packet switching</a></li> <li><a href="/wiki/Time-division_multiple_access#Dynamic_TDMA" title="Time-division multiple access">Dynamic TDMA</a></li> <li><a href="/wiki/Frequency-hopping_spread_spectrum" title="Frequency-hopping spread spectrum">FHSS</a></li> <li><a href="/wiki/Direct-sequence_spread_spectrum" title="Direct-sequence spread spectrum">DSSS</a></li> <li><a href="/wiki/Orthogonal_frequency-division_multiple_access" title="Orthogonal frequency-division multiple access">OFDMA</a></li> <li><a href="/wiki/Single-carrier_frequency-division-multiplex" class="mw-redirect" title="Single-carrier frequency-division-multiplex">SC-FDM</a></li> <li><a href="/wiki/Multi-carrier_spread_spectrum" class="mw-redirect" title="Multi-carrier spread spectrum">MC-SS</a></li></ul> </div></td> </tr><tr><th class="sidebar-heading" style="background:#cfc;"> Related topics</th></tr><tr><td class="sidebar-content" style="padding:0.15em 1.0em 0.8em;"> <ul><li><a href="/wiki/Channel_access_method" title="Channel access method">Channel access methods</a></li> <li><a href="/wiki/Medium_access_control" title="Medium access control">Medium access control</a></li></ul></td> </tr><tr><td class="sidebar-navbar"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><style data-mw-deduplicate="TemplateStyles:r1239400231">.mw-parser-output .navbar{display:inline;font-size:88%;font-weight:normal}.mw-parser-output .navbar-collapse{float:left;text-align:left}.mw-parser-output .navbar-boxtext{word-spacing:0}.mw-parser-output .navbar ul{display:inline-block;white-space:nowrap;line-height:inherit}.mw-parser-output .navbar-brackets::before{margin-right:-0.125em;content:"[ "}.mw-parser-output .navbar-brackets::after{margin-left:-0.125em;content:" ]"}.mw-parser-output .navbar li{word-spacing:-0.125em}.mw-parser-output .navbar a>span,.mw-parser-output .navbar a>abbr{text-decoration:inherit}.mw-parser-output .navbar-mini abbr{font-variant:small-caps;border-bottom:none;text-decoration:none;cursor:inherit}.mw-parser-output .navbar-ct-full{font-size:114%;margin:0 7em}.mw-parser-output .navbar-ct-mini{font-size:114%;margin:0 4em}html.skin-theme-clientpref-night .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}@media(prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}}@media print{.mw-parser-output .navbar{display:none!important}}</style><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:Multiplex_techniques" title="Template:Multiplex techniques"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Multiplex_techniques" title="Template talk:Multiplex techniques"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Multiplex_techniques" title="Special:EditPage/Template:Multiplex techniques"><abbr title="Edit this template">e</abbr></a></li></ul></div></td></tr></tbody></table> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Not to be confused with <a href="/wiki/Carrier-sense_multiple_access" title="Carrier-sense multiple access">Carrier-sense multiple access</a>.</div> <p><b>Code-division multiple access</b> (<b>CDMA</b>) is a <a href="/wiki/Channel_access_method" title="Channel access method">channel access method</a> used by various <a href="/wiki/Radio" title="Radio">radio</a> communication technologies. CDMA is an example of <a href="/wiki/Channel_access_method" title="Channel access method">multiple access</a>, where several transmitters can send information simultaneously over a single communication channel. This allows several users to share a band of frequencies (see <a href="/wiki/Bandwidth_(signal_processing)" title="Bandwidth (signal processing)">bandwidth</a>). To permit this without undue interference between the users, CDMA employs <a href="/wiki/Spread_spectrum" title="Spread spectrum">spread spectrum</a> technology and a special coding scheme (where each transmitter is assigned a code).<sup id="cite_ref-ref_1_1-0" class="reference"><a href="#cite_note-ref_1-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-ref_2_2-0" class="reference"><a href="#cite_note-ref_2-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> </p><p>CDMA optimizes the use of available bandwidth as it transmits over the entire frequency range and does not limit the user's frequency range. </p><p>It is used as the access method in many <a href="/wiki/Mobile_phone_standards" class="mw-redirect" title="Mobile phone standards">mobile phone standards</a>. <a href="/wiki/CdmaOne" title="CdmaOne">IS-95</a>, also called "cdmaOne", and its <a href="/wiki/3G" title="3G">3G</a> evolution <a href="/wiki/CDMA2000" title="CDMA2000">CDMA2000</a>, are often simply referred to as "CDMA", but <a href="/wiki/UMTS" title="UMTS">UMTS</a>, the 3G standard used by <a href="/wiki/GSM" title="GSM">GSM</a> carriers, also uses "wideband CDMA", or W-CDMA, as well as TD-CDMA and TD-SCDMA, as its radio technologies. Many carriers (such as <a href="/wiki/AT%26T_Corporation" title="AT&T Corporation">AT&T</a>, <a href="/wiki/U.S._Cellular" title="U.S. Cellular">UScellular</a> and <a href="/wiki/Verizon_(mobile_network)" class="mw-redirect" title="Verizon (mobile network)">Verizon</a>) shut down 3G CDMA-based networks in 2022 and 2024, rendering handsets supporting only those protocols unusable for calls, even to <a href="/wiki/9-1-1" class="mw-redirect" title="9-1-1">911</a>.<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><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> </p><p>It can be also used as a channel or medium access technology, like <a href="/wiki/ALOHA" class="mw-redirect" title="ALOHA">ALOHA</a> for example or as a permanent pilot/signalling channel to allow users to synchronize their local oscillators to a common system frequency, thereby also estimating the channel parameters permanently. </p><p>In these schemes, the message is modulated on a longer spreading sequence, consisting of several chips (0es and 1es). Due to their very advantageous auto- and crosscorrelation characteristics, these spreading sequences have also been used for radar applications for many decades, where they are called <a href="/wiki/Barker_code" title="Barker code">Barker codes</a> (with a very short sequence length of typically 8 to 32). </p><p>For space-based communication applications, CDMA has been used for many decades due to the large path loss and Doppler shift caused by satellite motion. CDMA is often used with <a href="/wiki/Binary_phase-shift_keying" class="mw-redirect" title="Binary phase-shift keying">binary phase-shift keying</a> (BPSK) in its simplest form, but can be combined with any modulation scheme like (in advanced cases) <a href="/wiki/Quadrature_amplitude_modulation" title="Quadrature amplitude modulation">quadrature amplitude modulation</a> (QAM) or <a href="/wiki/Orthogonal_frequency-division_multiplexing" title="Orthogonal frequency-division multiplexing">orthogonal frequency-division multiplexing</a> (OFDM), which typically makes it very robust and efficient (and equipping them with accurate ranging capabilities, which is difficult without CDMA). Other schemes use subcarriers based on <a href="/wiki/Binary_offset_carrier_modulation" title="Binary offset carrier modulation">binary offset carrier modulation</a> (BOC modulation), which is inspired by <a href="/wiki/Manchester_code" title="Manchester code">Manchester codes</a> and enable a larger gap between the virtual center frequency and the subcarriers, which is not the case for OFDM subcarriers. </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="History">History</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Code-division_multiple_access&action=edit&section=1" title="Edit section: History"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The technology of code-division multiple access channels has long been known. </p> <div class="mw-heading mw-heading3"><h3 id="United_States">United States</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Code-division_multiple_access&action=edit&section=2" title="Edit section: United States"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>In the US, one of the earliest descriptions of CDMA can be found in the summary report of Project Hartwell on "The Security of Overseas Transport", which was a summer research project carried out at the <a href="/wiki/Massachusetts_Institute_of_Technology" title="Massachusetts Institute of Technology">Massachusetts Institute of Technology</a> from June to August 1950.<sup id="cite_ref-Scholtz_1982May_IEEE_5-0" class="reference"><a href="#cite_note-Scholtz_1982May_IEEE-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> Further research in the context of <a href="/wiki/Radio_jamming" title="Radio jamming">jamming</a> and <a href="/wiki/Electronic_counter-countermeasure" title="Electronic counter-countermeasure">anti-jamming</a> was carried out in 1952 at <a href="/wiki/MIT_Lincoln_Laboratory" title="MIT Lincoln Laboratory">Lincoln Lab</a>.<sup id="cite_ref-Price_Shannon_19820728_6-0" class="reference"><a href="#cite_note-Price_Shannon_19820728-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Soviet_Union">Soviet Union</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Code-division_multiple_access&action=edit&section=3" title="Edit section: Soviet Union"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>In the <a href="/wiki/Soviet_Union" title="Soviet Union">Soviet Union</a> (USSR), the first work devoted to this subject was published in 1935 by <a href="/wiki/Dmitry_Vasiliyevich_Ageev" class="mw-redirect" title="Dmitry Vasiliyevich Ageev">Dmitry Ageev</a>.<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> It was shown that through the use of linear methods, there are three types of signal separation: frequency, time and compensatory.<sup class="noprint Inline-Template" style="margin-left:0.1em; white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Please_clarify" title="Wikipedia:Please clarify"><span title="No such thing. (August 2020)">clarification needed</span></a></i>]</sup> The technology of CDMA was used in 1957, when the young military radio engineer <a href="/wiki/Leonid_Kupriyanovich" title="Leonid Kupriyanovich">Leonid Kupriyanovich</a> in Moscow made an experimental model of a wearable automatic mobile phone, called LK-1 by him, with a base station.<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> LK-1 has a weight of 3 kg, 20–30 km operating distance, and 20–30 hours of battery life.<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><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> The base station, as described by the author, could serve several customers. In 1958, Kupriyanovich made the new experimental "pocket" model of mobile phone. This phone weighed 0.5 kg. To serve more customers, Kupriyanovich proposed the device, which he called "correlator."<sup id="cite_ref-11" class="reference"><a href="#cite_note-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-12" class="reference"><a href="#cite_note-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup> In 1958, the USSR also started the development of the "<a href="/wiki/Altai_(mobile_telephone_system)" title="Altai (mobile telephone system)">Altai</a>" national civil mobile phone service for cars, based on the Soviet MRT-1327 standard. The phone system weighed 11 kg (24 lb). It was placed in the trunk of the vehicles of high-ranking officials and used a standard handset in the passenger compartment. The main developers of the Altai system were VNIIS (Voronezh Science Research Institute of Communications) and GSPI (State Specialized Project Institute). In 1963 this service started in Moscow, and in 1970 Altai service was used in 30 USSR cities.<sup id="cite_ref-13" class="reference"><a href="#cite_note-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Uses">Uses</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Code-division_multiple_access&action=edit&section=4" title="Edit section: Uses"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Au_CDMA_1X_WIN_W31SAII_gravelly_silver_expansion.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Au_CDMA_1X_WIN_W31SAII_gravelly_silver_expansion.jpg/220px-Au_CDMA_1X_WIN_W31SAII_gravelly_silver_expansion.jpg" decoding="async" width="220" height="293" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Au_CDMA_1X_WIN_W31SAII_gravelly_silver_expansion.jpg/330px-Au_CDMA_1X_WIN_W31SAII_gravelly_silver_expansion.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Au_CDMA_1X_WIN_W31SAII_gravelly_silver_expansion.jpg/440px-Au_CDMA_1X_WIN_W31SAII_gravelly_silver_expansion.jpg 2x" data-file-width="1298" data-file-height="1730" /></a><figcaption>A CDMA2000 <a href="/wiki/Mobile_phone" title="Mobile phone">mobile phone</a></figcaption></figure> <ul><li>Synchronous CDM (code-division 'multiplexing', an early generation of CDMA) was implemented in the <a href="/wiki/Global_Positioning_System" title="Global Positioning System">Global Positioning System</a> (GPS). This predates and is distinct from its use in <a href="/wiki/Mobile_phone" title="Mobile phone">mobile phones</a>.</li> <li>The <a href="/wiki/Qualcomm" title="Qualcomm">Qualcomm</a> standard <a href="/wiki/IS-95" class="mw-redirect" title="IS-95">IS-95</a>, marketed as cdmaOne.</li> <li>The Qualcomm standard <a href="/wiki/IS-2000" class="mw-redirect" title="IS-2000">IS-2000</a>, known as CDMA2000, is used by several mobile phone companies, including the <a href="/wiki/Globalstar" title="Globalstar">Globalstar</a> network.<sup id="cite_ref-15" class="reference"><a href="#cite_note-15"><span class="cite-bracket">[</span>nb 1<span class="cite-bracket">]</span></a></sup></li> <li>The <a href="/wiki/UMTS" title="UMTS">UMTS</a> 3G mobile phone standard, which uses <a href="/wiki/W-CDMA" class="mw-redirect" title="W-CDMA">W-CDMA</a>.<sup id="cite_ref-19" class="reference"><a href="#cite_note-19"><span class="cite-bracket">[</span>nb 2<span class="cite-bracket">]</span></a></sup></li> <li>CDMA has been used in the <b>OmniTRACS</b> satellite system for transportation <a href="/wiki/Logistics" title="Logistics">logistics</a>.</li></ul> <div class="mw-heading mw-heading2"><h2 id="Steps_in_CDMA_modulation">Steps in CDMA modulation</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Code-division_multiple_access&action=edit&section=5" title="Edit section: Steps in CDMA modulation"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>CDMA is a spread-spectrum multiple-access technique. A spread-spectrum technique spreads the bandwidth of the data uniformly for the same transmitted power. A spreading code is a <a href="/wiki/Pseudorandom_binary_sequence" title="Pseudorandom binary sequence">pseudo-random code</a> in the time domain that has a narrow <a href="/wiki/Ambiguity_function" title="Ambiguity function">ambiguity function</a> in the frequency domain, unlike other narrow pulse codes. In CDMA a locally generated code runs at a much higher rate than the data to be transmitted. Data for transmission is combined by bitwise <a href="/wiki/XOR#Bitwise_operation" class="mw-redirect" title="XOR">XOR</a> (exclusive OR) with the faster code. The figure shows how a spread-spectrum signal is generated. The data signal with pulse duration of <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle T_{b}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>T</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>b</mi> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle T_{b}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/74c8b2d230dda9ccb7e55c237c918a935037c9d1" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:2.295ex; height:2.509ex;" alt="{\displaystyle T_{b}}"></span> (symbol period) is XORed with the code signal with pulse duration of <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle T_{c}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>T</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>c</mi> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle T_{c}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/66261e3cbed8035b2bf7a9ccb878c786cf7556c6" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:2.302ex; height:2.509ex;" alt="{\displaystyle T_{c}}"></span> (chip period). (Note: <a href="/wiki/Bandwidth_(signal_processing)" title="Bandwidth (signal processing)">bandwidth</a> is proportional to <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle 1/T}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mn>1</mn> <mrow class="MJX-TeXAtom-ORD"> <mo>/</mo> </mrow> <mi>T</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle 1/T}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/ee06bfe8f48b840ea1c11f78977a90f661f2375e" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:3.961ex; height:2.843ex;" alt="{\displaystyle 1/T}"></span>, where <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle T}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>T</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle T}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/ec7200acd984a1d3a3d7dc455e262fbe54f7f6e0" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.636ex; height:2.176ex;" alt="{\displaystyle T}"></span> = bit time.) Therefore, the bandwidth of the data signal is <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle 1/T_{b}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mn>1</mn> <mrow class="MJX-TeXAtom-ORD"> <mo>/</mo> </mrow> <msub> <mi>T</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>b</mi> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle 1/T_{b}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/1adf0d24450449d4888684b6a011b3babb3ddf66" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:4.62ex; height:2.843ex;" alt="{\displaystyle 1/T_{b}}"></span> and the bandwidth of the spread spectrum signal is <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle 1/T_{c}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mn>1</mn> <mrow class="MJX-TeXAtom-ORD"> <mo>/</mo> </mrow> <msub> <mi>T</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>c</mi> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle 1/T_{c}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/8c15876f402ca7d45e5ad4c63c5a5bccb5c0edf9" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:4.627ex; height:2.843ex;" alt="{\displaystyle 1/T_{c}}"></span>. Since <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle T_{c}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>T</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>c</mi> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle T_{c}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/66261e3cbed8035b2bf7a9ccb878c786cf7556c6" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:2.302ex; height:2.509ex;" alt="{\displaystyle T_{c}}"></span> is much smaller than <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle T_{b}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>T</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>b</mi> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle T_{b}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/74c8b2d230dda9ccb7e55c237c918a935037c9d1" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:2.295ex; height:2.509ex;" alt="{\displaystyle T_{b}}"></span>, the bandwidth of the spread-spectrum signal is much larger than the bandwidth of the original signal. The ratio <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle T_{b}/T_{c}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>T</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>b</mi> </mrow> </msub> <mrow class="MJX-TeXAtom-ORD"> <mo>/</mo> </mrow> <msub> <mi>T</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>c</mi> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle T_{b}/T_{c}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/90b2f3a80695a91db9d86eb586bbcc3d029d7d3b" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:5.759ex; height:2.843ex;" alt="{\displaystyle T_{b}/T_{c}}"></span> is called the spreading factor or processing gain and determines to a certain extent the upper limit of the total number of users supported simultaneously by a base station.<sup id="cite_ref-ref_1_1-1" class="reference"><a href="#cite_note-ref_1-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-ref_2_2-1" class="reference"><a href="#cite_note-ref_2-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> </p> <figure class="mw-halign-center" typeof="mw:File/Thumb"><a href="/wiki/File:Generation_of_CDMA.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/7/7e/Generation_of_CDMA.svg/500px-Generation_of_CDMA.svg.png" decoding="async" width="500" height="207" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/7/7e/Generation_of_CDMA.svg/750px-Generation_of_CDMA.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/7/7e/Generation_of_CDMA.svg/1000px-Generation_of_CDMA.svg.png 2x" data-file-width="760" data-file-height="315" /></a><figcaption>Generation of a CDMA signal</figcaption></figure> <p>Each user in a CDMA system uses a different code to modulate their signal. Choosing the codes used to modulate the signal is very important in the performance of CDMA systems. The best performance occurs when there is good separation between the signal of a desired user and the signals of other users. The separation of the signals is made by <a href="/wiki/Cross-correlation" title="Cross-correlation">correlating</a> the received signal with the locally generated code of the desired user. If the signal matches the desired user's code, then the correlation function will be high and the system can extract that signal. If the desired user's code has nothing in common with the signal, the correlation should be as close to zero as possible (thus eliminating the signal); this is referred to as <a href="/wiki/Cross-correlation" title="Cross-correlation">cross-correlation</a>. If the code is correlated with the signal at any time offset other than zero, the correlation should be as close to zero as possible. This is referred to as auto-correlation and is used to reject multi-path interference.<sup id="cite_ref-ref_3_20-0" class="reference"><a href="#cite_note-ref_3-20"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-ref_4_21-0" class="reference"><a href="#cite_note-ref_4-21"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup> </p><p>An analogy to the problem of multiple access is a room (channel) in which people wish to talk to each other simultaneously. To avoid confusion, people could take turns speaking (time division), speak at different pitches (frequency division), or speak in different languages (code division). CDMA is analogous to the last example where people speaking the same language can understand each other, but other languages are perceived as <a href="/wiki/Noise" title="Noise">noise</a> and rejected. Similarly, in radio CDMA, each group of users is given a shared code. Many codes occupy the same channel, but only users associated with a particular code can communicate. </p><p>In general, CDMA belongs to two basic categories: synchronous (orthogonal codes) and asynchronous (pseudorandom codes). </p> <div class="mw-heading mw-heading2"><h2 id="Code-division_multiplexing_(synchronous_CDMA)"><span id="Code-division_multiplexing_.28synchronous_CDMA.29"></span>Code-division multiplexing (synchronous CDMA)</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Code-division_multiple_access&action=edit&section=6" title="Edit section: Code-division multiplexing (synchronous CDMA)"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The digital modulation method is analogous to those used in simple radio transceivers. In the analog case, a low-frequency data signal is time-multiplied with a high-frequency pure sine-wave carrier and transmitted. This is effectively a frequency convolution (<a href="/wiki/Wiener%E2%80%93Khinchin_theorem" title="Wiener–Khinchin theorem">Wiener–Khinchin theorem</a>) of the two signals, resulting in a carrier with narrow sidebands. In the digital case, the sinusoidal carrier is replaced by <a href="/wiki/Walsh_function" title="Walsh function">Walsh functions</a>. These are binary square waves that form a complete orthonormal set. The data signal is also binary and the time multiplication is achieved with a simple XOR function. This is usually a <a href="/wiki/Gilbert_cell" title="Gilbert cell">Gilbert cell</a> mixer in the circuitry. </p><p>Synchronous CDMA exploits mathematical properties of <a href="/wiki/Orthogonality" title="Orthogonality">orthogonality</a> between <a href="/wiki/Coordinate_vector" title="Coordinate vector">vectors</a> representing the data strings. For example, the binary string <i>1011</i> is represented by the vector (1, 0, 1, 1). Vectors can be multiplied by taking their <a href="/wiki/Dot_product" title="Dot product">dot product</a>, by summing the products of their respective components (for example, if <b>u</b> = (<i>a</i>, <i>b</i>) and <b>v</b> = (<i>c</i>, <i>d</i>), then their dot product <b>u</b>·<b>v</b> = <i>ac</i> + <i>bd</i>). If the dot product is zero, the two vectors are said to be <i>orthogonal</i> to each other. Some properties of the dot product aid understanding of how <a href="/wiki/W-CDMA" class="mw-redirect" title="W-CDMA">W-CDMA</a> works. If vectors <b>a</b> and <b>b</b> are orthogonal, then <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \mathbf {a} \cdot \mathbf {b} =0}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="bold">a</mi> </mrow> <mo>⋅</mo> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="bold">b</mi> </mrow> <mo>=</mo> <mn>0</mn> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle \mathbf {a} \cdot \mathbf {b} =0}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/c416b33910828e0941fec78eec1170c79e7ca146" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:8.725ex; height:2.176ex;" alt="{\displaystyle \mathbf {a} \cdot \mathbf {b} =0}"></span> and: </p> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \mathbf {a} \cdot (\mathbf {a} +\mathbf {b} )=\|\mathbf {a} \|^{2},\ {\text{since}}\ \mathbf {a} \cdot \mathbf {a} +\mathbf {a} \cdot \mathbf {b} =\|\mathbf {a} \|^{2}+0,}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="bold">a</mi> </mrow> <mo>⋅</mo> <mo stretchy="false">(</mo> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="bold">a</mi> </mrow> <mo>+</mo> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="bold">b</mi> </mrow> <mo stretchy="false">)</mo> <mo>=</mo> <mo fence="false" stretchy="false">‖</mo> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="bold">a</mi> </mrow> <msup> <mo fence="false" stretchy="false">‖</mo> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msup> <mo>,</mo> <mtext> </mtext> <mrow class="MJX-TeXAtom-ORD"> <mtext>since</mtext> </mrow> <mtext> </mtext> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="bold">a</mi> </mrow> <mo>⋅</mo> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="bold">a</mi> </mrow> <mo>+</mo> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="bold">a</mi> </mrow> <mo>⋅</mo> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="bold">b</mi> </mrow> <mo>=</mo> <mo fence="false" stretchy="false">‖</mo> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="bold">a</mi> </mrow> <msup> <mo fence="false" stretchy="false">‖</mo> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msup> <mo>+</mo> <mn>0</mn> <mo>,</mo> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle \mathbf {a} \cdot (\mathbf {a} +\mathbf {b} )=\|\mathbf {a} \|^{2},\ {\text{since}}\ \mathbf {a} \cdot \mathbf {a} +\mathbf {a} \cdot \mathbf {b} =\|\mathbf {a} \|^{2}+0,}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/b5ac33e7c151f5eb8508fccd2e5305ec34da894b" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:49.315ex; height:3.176ex;" alt="{\displaystyle \mathbf {a} \cdot (\mathbf {a} +\mathbf {b} )=\|\mathbf {a} \|^{2},\ {\text{since}}\ \mathbf {a} \cdot \mathbf {a} +\mathbf {a} \cdot \mathbf {b} =\|\mathbf {a} \|^{2}+0,}"></span></dd> <dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \mathbf {a} \cdot (-\mathbf {a} +\mathbf {b} )=-\|\mathbf {a} \|^{2},\ {\text{since}}\ {-\mathbf {a} }\cdot \mathbf {a} +\mathbf {a} \cdot \mathbf {b} =-\|\mathbf {a} \|^{2}+0,}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="bold">a</mi> </mrow> <mo>⋅</mo> <mo stretchy="false">(</mo> <mo>−</mo> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="bold">a</mi> </mrow> <mo>+</mo> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="bold">b</mi> </mrow> <mo stretchy="false">)</mo> <mo>=</mo> <mo>−</mo> <mo fence="false" stretchy="false">‖</mo> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="bold">a</mi> </mrow> <msup> <mo fence="false" stretchy="false">‖</mo> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msup> <mo>,</mo> <mtext> </mtext> <mrow class="MJX-TeXAtom-ORD"> <mtext>since</mtext> </mrow> <mtext> </mtext> <mrow class="MJX-TeXAtom-ORD"> <mo>−</mo> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="bold">a</mi> </mrow> </mrow> <mo>⋅</mo> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="bold">a</mi> </mrow> <mo>+</mo> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="bold">a</mi> </mrow> <mo>⋅</mo> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="bold">b</mi> </mrow> <mo>=</mo> <mo>−</mo> <mo fence="false" stretchy="false">‖</mo> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="bold">a</mi> </mrow> <msup> <mo fence="false" stretchy="false">‖</mo> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msup> <mo>+</mo> <mn>0</mn> <mo>,</mo> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle \mathbf {a} \cdot (-\mathbf {a} +\mathbf {b} )=-\|\mathbf {a} \|^{2},\ {\text{since}}\ {-\mathbf {a} }\cdot \mathbf {a} +\mathbf {a} \cdot \mathbf {b} =-\|\mathbf {a} \|^{2}+0,}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/912606ea626c1650f13c67d9a1a6d863dbea09a1" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:56.548ex; height:3.176ex;" alt="{\displaystyle \mathbf {a} \cdot (-\mathbf {a} +\mathbf {b} )=-\|\mathbf {a} \|^{2},\ {\text{since}}\ {-\mathbf {a} }\cdot \mathbf {a} +\mathbf {a} \cdot \mathbf {b} =-\|\mathbf {a} \|^{2}+0,}"></span></dd> <dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \mathbf {b} \cdot (\mathbf {a} +\mathbf {b} )=\|\mathbf {b} \|^{2},\ {\text{since}}\ \mathbf {b} \cdot \mathbf {a} +\mathbf {b} \cdot \mathbf {b} =0+\|\mathbf {b} \|^{2},}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="bold">b</mi> </mrow> <mo>⋅</mo> <mo stretchy="false">(</mo> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="bold">a</mi> </mrow> <mo>+</mo> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="bold">b</mi> </mrow> <mo stretchy="false">)</mo> <mo>=</mo> <mo fence="false" stretchy="false">‖</mo> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="bold">b</mi> </mrow> <msup> <mo fence="false" stretchy="false">‖</mo> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msup> <mo>,</mo> <mtext> </mtext> <mrow class="MJX-TeXAtom-ORD"> <mtext>since</mtext> </mrow> <mtext> </mtext> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="bold">b</mi> </mrow> <mo>⋅</mo> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="bold">a</mi> </mrow> <mo>+</mo> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="bold">b</mi> </mrow> <mo>⋅</mo> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="bold">b</mi> </mrow> <mo>=</mo> <mn>0</mn> <mo>+</mo> <mo fence="false" stretchy="false">‖</mo> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="bold">b</mi> </mrow> <msup> <mo fence="false" stretchy="false">‖</mo> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msup> <mo>,</mo> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle \mathbf {b} \cdot (\mathbf {a} +\mathbf {b} )=\|\mathbf {b} \|^{2},\ {\text{since}}\ \mathbf {b} \cdot \mathbf {a} +\mathbf {b} \cdot \mathbf {b} =0+\|\mathbf {b} \|^{2},}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/813662c13436da6b0d1ac81794f2b6153b43b91e" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:50.244ex; height:3.176ex;" alt="{\displaystyle \mathbf {b} \cdot (\mathbf {a} +\mathbf {b} )=\|\mathbf {b} \|^{2},\ {\text{since}}\ \mathbf {b} \cdot \mathbf {a} +\mathbf {b} \cdot \mathbf {b} =0+\|\mathbf {b} \|^{2},}"></span></dd> <dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \mathbf {b} \cdot (\mathbf {a} -\mathbf {b} )=-\|\mathbf {b} \|^{2},\ {\text{since}}\ \mathbf {b} \cdot \mathbf {a} -\mathbf {b} \cdot \mathbf {b} =0-\|\mathbf {b} \|^{2}.}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="bold">b</mi> </mrow> <mo>⋅</mo> <mo stretchy="false">(</mo> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="bold">a</mi> </mrow> <mo>−</mo> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="bold">b</mi> </mrow> <mo stretchy="false">)</mo> <mo>=</mo> <mo>−</mo> <mo fence="false" stretchy="false">‖</mo> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="bold">b</mi> </mrow> <msup> <mo fence="false" stretchy="false">‖</mo> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msup> <mo>,</mo> <mtext> </mtext> <mrow class="MJX-TeXAtom-ORD"> <mtext>since</mtext> </mrow> <mtext> </mtext> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="bold">b</mi> </mrow> <mo>⋅</mo> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="bold">a</mi> </mrow> <mo>−</mo> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="bold">b</mi> </mrow> <mo>⋅</mo> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="bold">b</mi> </mrow> <mo>=</mo> <mn>0</mn> <mo>−</mo> <mo fence="false" stretchy="false">‖</mo> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="bold">b</mi> </mrow> <msup> <mo fence="false" stretchy="false">‖</mo> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msup> <mo>.</mo> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle \mathbf {b} \cdot (\mathbf {a} -\mathbf {b} )=-\|\mathbf {b} \|^{2},\ {\text{since}}\ \mathbf {b} \cdot \mathbf {a} -\mathbf {b} \cdot \mathbf {b} =0-\|\mathbf {b} \|^{2}.}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/26c2776779006d52a1a7f74012c9639d3dd5a997" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:52.052ex; height:3.176ex;" alt="{\displaystyle \mathbf {b} \cdot (\mathbf {a} -\mathbf {b} )=-\|\mathbf {b} \|^{2},\ {\text{since}}\ \mathbf {b} \cdot \mathbf {a} -\mathbf {b} \cdot \mathbf {b} =0-\|\mathbf {b} \|^{2}.}"></span></dd></dl> <p>Each user in synchronous CDMA uses a code orthogonal to the others' codes to modulate their signal. An example of 4 mutually orthogonal digital signals is shown in the figure below. Orthogonal codes have a cross-correlation equal to zero; in other words, they do not interfere with each other. In the case of IS-95, 64-bit <a href="/wiki/Walsh_code" class="mw-redirect" title="Walsh code">Walsh codes</a> are used to encode the signal to separate different users. Since each of the 64 Walsh codes is orthogonal to all other, the signals are channelized into 64 orthogonal signals. The following example demonstrates how each user's signal can be encoded and decoded. </p> <div class="mw-heading mw-heading3"><h3 id="Example">Example</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Code-division_multiple_access&action=edit&section=7" title="Edit section: Example"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:Cdma_orthogonal_signals.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/2/25/Cdma_orthogonal_signals.png/220px-Cdma_orthogonal_signals.png" decoding="async" width="220" height="374" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/2/25/Cdma_orthogonal_signals.png/330px-Cdma_orthogonal_signals.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/2/25/Cdma_orthogonal_signals.png/440px-Cdma_orthogonal_signals.png 2x" data-file-width="602" data-file-height="1024" /></a><figcaption>An example of 4 mutually orthogonal digital signals</figcaption></figure> <p>Start with a set of vectors that are mutually <a href="/wiki/Orthogonality" title="Orthogonality">orthogonal</a>. (Although mutual orthogonality is the only condition, these vectors are usually constructed for ease of decoding, for example columns or rows from <a href="/wiki/Walsh_matrix" title="Walsh matrix">Walsh matrices</a>.) An example of orthogonal functions is shown in the adjacent picture. These vectors will be assigned to individual users and are called the <i>code</i>, <i><a href="/wiki/Chip_(CDMA)" title="Chip (CDMA)">chip</a> code</i>, or <i>chipping code</i>. In the interest of brevity, the rest of this example uses codes <b>v</b> with only two bits. </p><p>Each user is associated with a different code, say <b>v</b>. A 1 bit is represented by transmitting a positive code <b>v</b>, and a 0 bit is represented by a negative code <b>−v</b>. For example, if <b>v</b> = (<i>v</i><sub>0</sub>, <i>v</i><sub>1</sub>) = (1, −1) and the data that the user wishes to transmit is (1, 0, 1, 1), then the transmitted symbols would be </p> <dl><dd>(<b>v</b>, <b>−v</b>, <b>v</b>, <b>v</b>) = (<i>v</i><sub>0</sub>, <i>v</i><sub>1</sub>, −<i>v</i><sub>0</sub>, −<i>v</i><sub>1</sub>, <i>v</i><sub>0</sub>, <i>v</i><sub>1</sub>, <i>v</i><sub>0</sub>, <i>v</i><sub>1</sub>) = (1, −1, −1, 1, 1, −1, 1, −1).</dd></dl> <p>For the purposes of this article, we call this constructed vector the <i>transmitted vector</i>. </p><p>Each sender has a different, unique vector <b>v</b> chosen from that set, but the construction method of the transmitted vector is identical. </p><p>Now, due to physical properties of interference, if two signals at a point are in phase, they add to give twice the amplitude of each signal, but if they are out of phase, they subtract and give a signal that is the difference of the amplitudes. Digitally, this behaviour can be modelled by the addition of the transmission vectors, component by component. </p><p>If sender0 has code (1, −1) and data (1, 0, 1, 1), and sender1 has code (1, 1) and data (0, 0, 1, 1), and both senders transmit simultaneously, then this table describes the coding steps: </p> <table style="border: 1px #aaaaaa solid; background-color: #f7f8ff; margin-left: auto; margin-right: auto;"> <tbody><tr> <td align="center" bgcolor="#CCCCCC">Step </td> <td align="center" bgcolor="#CCCCCC">Encode sender0 </td> <td align="center" bgcolor="#CCCCCC">Encode sender1 </td></tr> <tr> <td valign="top">0 </td> <td>code0 = (1, −1), data0 = (1, 0, 1, 1) </td> <td>code1 = (1, 1), data1 = (0, 0, 1, 1) </td></tr> <tr> <td valign="top">1 </td> <td>encode0 = 2(1, 0, 1, 1) − (1, 1, 1, 1) = (1, −1, 1, 1) </td> <td>encode1 = 2(0, 0, 1, 1) − (1, 1, 1, 1) = (−1, −1, 1, 1) </td></tr> <tr> <td valign="top">2 </td> <td>signal0 = encode0 ⊗ code0<br />= (1, −1, 1, 1) ⊗ (1, −1)<br />= (1, −1, −1, 1, 1, −1, 1, −1) </td> <td>signal1 = encode1 ⊗ code1<br />= (−1, −1, 1, 1) ⊗ (1, 1)<br />= (−1, −1, −1, −1, 1, 1, 1, 1) </td></tr></tbody></table> <p>Because signal0 and signal1 are transmitted at the same time into the air, they add to produce the raw signal </p> <dl><dd>(1, −1, −1, 1, 1, −1, 1, −1) + (−1, −1, −1, −1, 1, 1, 1, 1) = (0, −2, −2, 0, 2, 0, 2, 0).</dd></dl> <p>This raw signal is called an interference pattern. The receiver then extracts an intelligible signal for any known sender by combining the sender's code with the interference pattern. The following table explains how this works and shows that the signals do not interfere with one another: </p> <table style="border: 1px #aaaaaa solid; background-color: #f7f8ff; margin-left: auto; margin-right: auto;"> <tbody><tr> <td align="center" bgcolor="#CCCCCC">Step </td> <td align="center" bgcolor="#CCCCCC">Decode sender0 </td> <td align="center" bgcolor="#CCCCCC">Decode sender1 </td></tr> <tr> <td>0 </td> <td>code0 = (1, −1), signal = (0, −2, −2, 0, 2, 0, 2, 0) </td> <td>code1 = (1, 1), signal = (0, −2, −2, 0, 2, 0, 2, 0) </td></tr> <tr> <td>1 </td> <td>decode0 = pattern.vector0 </td> <td>decode1 = pattern.vector1 </td></tr> <tr> <td>2 </td> <td>decode0 = ((0, −2), (−2, 0), (2, 0), (2, 0)) · (1, −1) </td> <td>decode1 = ((0, −2), (−2, 0), (2, 0), (2, 0)) · (1, 1) </td></tr> <tr> <td>3 </td> <td>decode0 = ((0 + 2), (−2 + 0), (2 + 0), (2 + 0)) </td> <td>decode1 = ((0 − 2), (−2 + 0), (2 + 0), (2 + 0)) </td></tr> <tr> <td>4 </td> <td>data0=(2, −2, 2, 2), meaning (1, 0, 1, 1) </td> <td>data1=(−2, −2, 2, 2), meaning (0, 0, 1, 1) </td></tr></tbody></table> <p>Further, after decoding, all values greater than 0 are interpreted as 1, while all values less than zero are interpreted as 0. For example, after decoding, data0 is (2, −2, 2, 2), but the receiver interprets this as (1, 0, 1, 1). Values of exactly 0 mean that the sender did not transmit any data, as in the following example: </p><p>Assume signal0 = (1, −1, −1, 1, 1, −1, 1, −1) is transmitted alone. The following table shows the decode at the receiver: </p> <table style="border: 1px #aaaaaa solid; background-color: #f7f8ff; margin-left: auto; margin-right: auto;"> <tbody><tr> <td align="center" bgcolor="#CCCCCC">Step </td> <td align="center" bgcolor="#CCCCCC">Decode sender0 </td> <td align="center" bgcolor="#CCCCCC">Decode sender1 </td></tr> <tr> <td>0 </td> <td>code0 = (1, −1), signal = (1, −1, −1, 1, 1, −1, 1, −1) </td> <td>code1 = (1, 1), signal = (1, −1, −1, 1, 1, −1, 1, −1) </td></tr> <tr> <td>1 </td> <td>decode0 = pattern.vector0 </td> <td>decode1 = pattern.vector1 </td></tr> <tr> <td>2 </td> <td>decode0 = ((1, −1), (−1, 1), (1, −1), (1, −1)) · (1, −1) </td> <td>decode1 = ((1, −1), (−1, 1), (1, −1), (1, −1)) · (1, 1) </td></tr> <tr> <td>3 </td> <td>decode0 = ((1 + 1), (−1 − 1), (1 + 1), (1 + 1)) </td> <td>decode1 = ((1 − 1), (−1 + 1), (1 − 1), (1 − 1)) </td></tr> <tr> <td>4 </td> <td>data0 = (2, −2, 2, 2), meaning (1, 0, 1, 1) </td> <td>data1 = (0, 0, 0, 0), meaning no data </td></tr></tbody></table> <p>When the receiver attempts to decode the signal using sender1's code, the data is all zeros; therefore the cross-correlation is equal to zero and it is clear that sender1 did not transmit any data. </p> <div class="mw-heading mw-heading2"><h2 id="Asynchronous_CDMA">Asynchronous CDMA</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Code-division_multiple_access&action=edit&section=8" title="Edit section: Asynchronous CDMA"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">See also: <a href="/wiki/Direct-sequence_spread_spectrum" title="Direct-sequence spread spectrum">Direct-sequence spread spectrum</a> and <a href="/wiki/Near%E2%80%93far_problem" title="Near–far problem">near–far problem</a></div> <p>When mobile-to-base links cannot be precisely coordinated, particularly due to the mobility of the handsets, a different approach is required. Since it is not mathematically possible to create signature sequences that are both orthogonal for arbitrarily random starting points and which make full use of the code space, unique "pseudo-random" or "pseudo-noise" sequences called spreading sequences are used in <i>asynchronous</i> CDMA systems. A spreading sequence is a binary sequence that appears random but can be reproduced in a deterministic manner by intended receivers. These spreading sequences are used to encode and decode a user's signal in asynchronous CDMA in the same manner as the orthogonal codes in synchronous CDMA (shown in the example above). These spreading sequences are statistically uncorrelated, and the sum of a large number of spreading sequences results in <i>multiple access interference</i> (MAI) that is approximated by a Gaussian noise process (following the <a href="/wiki/Central_limit_theorem" title="Central limit theorem">central limit theorem</a> in statistics). <a href="/wiki/Gold_code" title="Gold code">Gold codes</a> are an example of a spreading sequence suitable for this purpose, as there is low correlation between the codes. If all of the users are received with the same power level, then the variance (e.g., the noise power) of the MAI increases in direct proportion to the number of users. In other words, unlike synchronous CDMA, the signals of other users will appear as noise to the signal of interest and interfere slightly with the desired signal in proportion to number of users. </p><p>All forms of CDMA use the <a href="/wiki/Spread-spectrum" class="mw-redirect" title="Spread-spectrum">spread-spectrum</a> <a href="/wiki/Spreading_factor" class="mw-redirect" title="Spreading factor">spreading factor</a> to allow receivers to partially discriminate against unwanted signals. Signals encoded with the specified spreading sequences are received, while signals with different sequences (or the same sequences but different timing offsets) appear as wideband noise reduced by the spreading factor. </p><p>Since each user generates MAI, controlling the signal strength is an important issue with CDMA transmitters. A CDM (synchronous CDMA), TDMA, or FDMA receiver can in theory completely reject arbitrarily strong signals using different codes, time slots or frequency channels due to the orthogonality of these systems. This is not true for asynchronous CDMA; rejection of unwanted signals is only partial. If any or all of the unwanted signals are much stronger than the desired signal, they will overwhelm it. This leads to a general requirement in any asynchronous CDMA system to approximately match the various signal power levels as seen at the receiver. In CDMA cellular, the base station uses a fast closed-loop power-control scheme to tightly control each mobile's transmit power. </p><p>In 2019, schemes to precisely estimate the required length of the codes in dependence of Doppler and delay characteristics have been developed.<sup id="cite_ref-22" class="reference"><a href="#cite_note-22"><span class="cite-bracket">[</span>20<span class="cite-bracket">]</span></a></sup> Soon after, machine learning based techniques that generate sequences of a desired length and spreading properties have been published as well. These are highly competitive with the classic Gold and Welch sequences. These are not generated by linear-feedback-shift-registers, but have to be stored in lookup tables. </p> <div class="mw-heading mw-heading3"><h3 id="Advantages_of_asynchronous_CDMA_over_other_techniques">Advantages of asynchronous CDMA over other techniques</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Code-division_multiple_access&action=edit&section=9" title="Edit section: Advantages of asynchronous CDMA over other techniques"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <div class="mw-heading mw-heading4"><h4 id="Efficient_practical_utilization_of_the_fixed_frequency_spectrum">Efficient practical utilization of the fixed frequency spectrum</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Code-division_multiple_access&action=edit&section=10" title="Edit section: Efficient practical utilization of the fixed frequency spectrum"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>In theory CDMA, TDMA and FDMA have exactly the same spectral efficiency, but, in practice, each has its own challenges – power control in the case of CDMA, timing in the case of TDMA, and frequency generation/filtering in the case of FDMA. </p><p>TDMA systems must carefully synchronize the transmission times of all the users to ensure that they are received in the correct time slot and do not cause interference. Since this cannot be perfectly controlled in a mobile environment, each time slot must have a guard time, which reduces the probability that users will interfere, but decreases the spectral efficiency. </p><p>Similarly, FDMA systems must use a guard band between adjacent channels, due to the unpredictable <a href="/wiki/Doppler_effect" title="Doppler effect">Doppler shift</a> of the signal spectrum because of user mobility. The guard bands will reduce the probability that adjacent channels will interfere, but decrease the utilization of the spectrum. </p> <div class="mw-heading mw-heading4"><h4 id="Flexible_allocation_of_resources">Flexible allocation of resources</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Code-division_multiple_access&action=edit&section=11" title="Edit section: Flexible allocation of resources"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Asynchronous CDMA offers a key advantage in the flexible allocation of resources i.e. allocation of spreading sequences to active users. In the case of CDM (synchronous CDMA), TDMA, and FDMA the number of simultaneous orthogonal codes, time slots, and frequency slots respectively are fixed, hence the capacity in terms of the number of simultaneous users is limited. There are a fixed number of orthogonal codes, time slots or frequency bands that can be allocated for CDM, TDMA, and FDMA systems, which remain underutilized due to the bursty nature of telephony and packetized data transmissions. There is no strict limit to the number of users that can be supported in an asynchronous CDMA system, only a practical limit governed by the desired bit error probability since the SIR (signal-to-interference ratio) varies inversely with the number of users. In a bursty traffic environment like mobile telephony, the advantage afforded by asynchronous CDMA is that the performance (bit error rate) is allowed to fluctuate randomly, with an average value determined by the number of users times the percentage of utilization. Suppose there are 2<i>N</i> users that only talk half of the time, then 2<i>N</i> users can be accommodated with the same <i>average</i> bit error probability as <i>N</i> users that talk all of the time. The key difference here is that the bit error probability for <i>N</i> users talking all of the time is constant, whereas it is a <i>random</i> quantity (with the same mean) for 2<i>N</i> users talking half of the time. </p><p>In other words, asynchronous CDMA is ideally suited to a mobile network where large numbers of transmitters each generate a relatively small amount of traffic at irregular intervals. CDM (synchronous CDMA), TDMA, and FDMA systems cannot recover the underutilized resources inherent to bursty traffic due to the fixed number of <a href="/wiki/Orthogonal" class="mw-redirect" title="Orthogonal">orthogonal</a> codes, time slots or frequency channels that can be assigned to individual transmitters. For instance, if there are <i>N</i> time slots in a TDMA system and 2<i>N</i> users that talk half of the time, then half of the time there will be more than <i>N</i> users needing to use more than <i>N</i> time slots. Furthermore, it would require significant overhead to continually allocate and deallocate the orthogonal-code, time-slot or frequency-channel resources. By comparison, asynchronous CDMA transmitters simply send when they have something to say and go off the air when they do not, keeping the same signature sequence as long as they are connected to the system. </p> <div class="mw-heading mw-heading3"><h3 id="Spread-spectrum_characteristics_of_CDMA">Spread-spectrum characteristics of CDMA</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Code-division_multiple_access&action=edit&section=12" title="Edit section: Spread-spectrum characteristics of CDMA"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Most modulation schemes try to minimize the bandwidth of this signal since bandwidth is a limited resource. However, spread-spectrum techniques use a transmission bandwidth that is several orders of magnitude greater than the minimum required signal bandwidth. One of the initial reasons for doing this was military applications including guidance and communication systems. These systems were designed using spread spectrum because of its security and resistance to jamming. Asynchronous CDMA has some level of privacy built in because the signal is spread using a pseudo-random code; this code makes the spread-spectrum signals appear random or have noise-like properties. A receiver cannot demodulate this transmission without knowledge of the pseudo-random sequence used to encode the data. CDMA is also resistant to jamming. A jamming signal only has a finite amount of power available to jam the signal. The jammer can either spread its energy over the entire bandwidth of the signal or jam only part of the entire signal.<sup id="cite_ref-ref_3_20-1" class="reference"><a href="#cite_note-ref_3-20"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-ref_4_21-1" class="reference"><a href="#cite_note-ref_4-21"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup> </p><p>CDMA can also effectively reject narrow-band interference. Since narrow-band interference affects only a small portion of the spread-spectrum signal, it can easily be removed through notch filtering without much loss of information. <a href="/wiki/Convolution_encoding" class="mw-redirect" title="Convolution encoding">Convolution encoding</a> and <a href="/wiki/Forward_error_correction#Interleaving" class="mw-redirect" title="Forward error correction">interleaving</a> can be used to assist in recovering this lost data. CDMA signals are also resistant to multipath fading. Since the spread-spectrum signal occupies a large bandwidth, only a small portion of this will undergo fading due to multipath at any given time. Like the narrow-band interference, this will result in only a small loss of data and can be overcome. </p><p>Another reason CDMA is resistant to multipath interference is because the delayed versions of the transmitted pseudo-random codes will have poor correlation with the original pseudo-random code, and will thus appear as another user, which is ignored at the receiver. In other words, as long as the multipath channel induces at least one chip of delay, the multipath signals will arrive at the receiver such that they are shifted in time by at least one chip from the intended signal. The correlation properties of the pseudo-random codes are such that this slight delay causes the multipath to appear uncorrelated with the intended signal, and it is thus ignored. </p><p>Some CDMA devices use a <a href="/wiki/Rake_receiver" title="Rake receiver">rake receiver</a>, which exploits multipath delay components to improve the performance of the system. A rake receiver combines the information from several correlators, each one tuned to a different path delay, producing a stronger version of the signal than a simple receiver with a single correlation tuned to the path delay of the strongest signal.<sup id="cite_ref-ref_1_1-2" class="reference"><a href="#cite_note-ref_1-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-ref_2_2-2" class="reference"><a href="#cite_note-ref_2-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> </p><p>Frequency reuse is the ability to reuse the same radio channel frequency at other cell sites within a cellular system. In the FDMA and TDMA systems, frequency planning is an important consideration. The frequencies used in different cells must be planned carefully to ensure signals from different cells do not interfere with each other. In a CDMA system, the same frequency can be used in every cell, because channelization is done using the pseudo-random codes. Reusing the same frequency in every cell eliminates the need for frequency planning in a CDMA system; however, planning of the different pseudo-random sequences must be done to ensure that the received signal from one cell does not correlate with the signal from a nearby cell.<sup id="cite_ref-ref_1_1-3" class="reference"><a href="#cite_note-ref_1-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> </p><p>Since adjacent cells use the same frequencies, CDMA systems have the ability to perform soft hand-offs. Soft hand-offs allow the mobile telephone to communicate simultaneously with two or more cells. The best signal quality is selected until the hand-off is complete. This is different from hard hand-offs utilized in other cellular systems. In a hard-hand-off situation, as the mobile telephone approaches a hand-off, signal strength may vary abruptly. In contrast, CDMA systems use the soft hand-off, which is undetectable and provides a more reliable and higher-quality signal.<sup id="cite_ref-ref_2_2-3" class="reference"><a href="#cite_note-ref_2-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Collaborative_CDMA">Collaborative CDMA</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Code-division_multiple_access&action=edit&section=13" title="Edit section: Collaborative CDMA"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>A novel collaborative multi-user transmission and detection scheme called collaborative CDMA<sup id="cite_ref-23" class="reference"><a href="#cite_note-23"><span class="cite-bracket">[</span>21<span class="cite-bracket">]</span></a></sup> has been investigated for the uplink that exploits the differences between users' fading channel signatures to increase the user capacity well beyond the spreading length in the MAI-limited environment. The authors show that it is possible to achieve this increase at a low complexity and high <a href="/wiki/Bit_error_rate" title="Bit error rate">bit error rate</a> performance in flat fading channels, which is a major research challenge for overloaded CDMA systems. In this approach, instead of using one sequence per user as in conventional CDMA, the authors group a small number of users to share the same spreading sequence and enable group spreading and despreading operations. The new collaborative multi-user receiver consists of two stages: group multi-user detection (MUD) stage to suppress the MAI between the groups and a low-complexity maximum-likelihood detection stage to recover jointly the co-spread users' data using minimal Euclidean-distance measure and users' channel-gain coefficients. An enhanced CDMA version known as interleave-division multiple access (IDMA) uses the orthogonal interleaving as the only means of user separation in place of signature sequence used in CDMA system. </p> <div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Code-division_multiple_access&action=edit&section=14" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1184024115">.mw-parser-output .div-col{margin-top:0.3em;column-width:30em}.mw-parser-output .div-col-small{font-size:90%}.mw-parser-output .div-col-rules{column-rule:1px solid #aaa}.mw-parser-output .div-col dl,.mw-parser-output .div-col ol,.mw-parser-output .div-col ul{margin-top:0}.mw-parser-output .div-col li,.mw-parser-output .div-col dd{page-break-inside:avoid;break-inside:avoid-column}</style><div class="div-col" style="column-width: 25em;"> <ul><li><a href="/wiki/CDMA_spectral_efficiency" title="CDMA spectral efficiency">CDMA spectral efficiency</a></li> <li><a href="/wiki/CDMA2000" title="CDMA2000">CDMA2000</a></li> <li><a href="/wiki/Comparison_of_mobile_phone_standards" title="Comparison of mobile phone standards">Comparison of mobile phone standards</a></li> <li><a href="/wiki/CdmaOne" title="CdmaOne">cdmaOne</a></li> <li><a href="/wiki/Orthogonal_variable_spreading_factor" class="mw-redirect" title="Orthogonal variable spreading factor">Orthogonal variable spreading factor</a> (OVSF), an implementation of CDMA</li> <li><a href="/wiki/Pseudorandom_noise" title="Pseudorandom noise">Pseudorandom noise</a></li> <li><a href="/wiki/Quadrature-division_multiple_access" title="Quadrature-division multiple access">Quadrature-division multiple access</a> (QDMA), an implementation of CDMA</li> <li><a href="/wiki/Rise_over_thermal" title="Rise over thermal">Rise over thermal</a></li> <li><a href="/wiki/Spread_spectrum" title="Spread spectrum">Spread spectrum</a></li> <li><a href="/wiki/W-CDMA" class="mw-redirect" title="W-CDMA">W-CDMA</a></li></ul> </div> <div class="mw-heading mw-heading2"><h2 id="Notes">Notes</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Code-division_multiple_access&action=edit&section=15" title="Edit section: Notes"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist"> <div class="mw-references-wrap"><ol class="references"> <li id="cite_note-15"><span class="mw-cite-backlink"><b><a href="#cite_ref-15">^</a></b></span> <span class="reference-text">Globalstar uses elements of CDMA, <a href="/wiki/Time-division_multiple_access" title="Time-division multiple access">TDMA</a> and <a href="/wiki/FDMA" class="mw-redirect" title="FDMA">FDMA</a> combining with satellite multiple beam antennas.<sup id="cite_ref-14" class="reference"><a href="#cite_note-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup></span> </li> <li id="cite_note-19"><span class="mw-cite-backlink"><b><a href="#cite_ref-19">^</a></b></span> <span class="reference-text">The UMTS networks and other CDMA based systems are also known as a kind of <i>interference-limited</i> systems.<sup id="cite_ref-16" class="reference"><a href="#cite_note-16"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-17" class="reference"><a href="#cite_note-17"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup> This relates to the properties of the CDMA technology: all users operate in the same frequency range that impacts <a href="/wiki/Signal-to-interference-plus-noise_ratio" title="Signal-to-interference-plus-noise ratio">SINR</a> and, hence, reduces coverage and capacity.<sup id="cite_ref-Walke-Seidenberg-Althoff_2003_18-0" class="reference"><a href="#cite_note-Walke-Seidenberg-Althoff_2003-18"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup></span> </li> </ol></div></div> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Code-division_multiple_access&action=edit&section=16" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1239543626"><div class="reflist reflist-columns references-column-width" style="column-width: 30em;"> <ol class="references"> <li id="cite_note-ref_1-1"><span class="mw-cite-backlink">^ <a href="#cite_ref-ref_1_1-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-ref_1_1-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-ref_1_1-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-ref_1_1-3"><sup><i><b>d</b></i></sup></a></span> <span class="reference-text"><style data-mw-deduplicate="TemplateStyles:r1238218222">.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("//upload.wikimedia.org/wikipedia/commons/6/65/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("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/4/4c/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}}</style><cite id="CITEREFTorrieri2018" class="citation book cs1">Torrieri, Don (2018). <i>Principles of Spread-Spectrum Communication Systems, 4th ed</i>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Principles+of+Spread-Spectrum+Communication+Systems%2C+4th+ed.&rft.date=2018&rft.aulast=Torrieri&rft.aufirst=Don&rfr_id=info%3Asid%2Fen.wikipedia.org%3ACode-division+multiple+access" class="Z3988"></span></span> </li> <li id="cite_note-ref_2-2"><span class="mw-cite-backlink">^ <a href="#cite_ref-ref_2_2-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-ref_2_2-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-ref_2_2-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-ref_2_2-3"><sup><i><b>d</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFStuber2017" class="citation book cs1">Stuber, Gordon L. (2017). <i>Principles of Mobile Communication, 4th ed</i>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Principles+of+Mobile+Communication%2C+4th+ed.&rft.date=2017&rft.aulast=Stuber&rft.aufirst=Gordon+L.&rfr_id=info%3Asid%2Fen.wikipedia.org%3ACode-division+multiple+access" class="Z3988"></span></span> </li> <li id="cite_note-3"><span class="mw-cite-backlink"><b><a href="#cite_ref-3">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFKelly2022" class="citation web cs1">Kelly, Samantha Murphy (February 22, 2022). <a rel="nofollow" class="external text" href="https://www.cnn.com/2022/02/22/tech/att-3g-network-shutdown/index.html">"AT&T is shutting down its 3G network. Here's how it could impact you"</a>. <i><a href="/wiki/CNN" title="CNN">CNN</a></i>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=CNN&rft.atitle=AT%26T+is+shutting+down+its+3G+network.+Here%27s+how+it+could+impact+you&rft.date=2022-02-22&rft.aulast=Kelly&rft.aufirst=Samantha+Murphy&rft_id=https%3A%2F%2Fwww.cnn.com%2F2022%2F02%2F22%2Ftech%2Fatt-3g-network-shutdown%2Findex.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3ACode-division+multiple+access" class="Z3988"></span></span> </li> <li id="cite_note-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-4">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFJohnson2021" class="citation web cs1">Johnson, Allison (2021-03-30). <a rel="nofollow" class="external text" href="https://www.theverge.com/2021/3/30/22358628/verizon-3g-cdma-shutdown-date-2022">"Verizon will shutter its 3G CDMA by the end of 2022"</a>. <i>The Verge</i><span class="reference-accessdate">. Retrieved <span class="nowrap">2021-10-09</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=The+Verge&rft.atitle=Verizon+will+shutter+its+3G+CDMA+by+the+end+of+2022&rft.date=2021-03-30&rft.aulast=Johnson&rft.aufirst=Allison&rft_id=https%3A%2F%2Fwww.theverge.com%2F2021%2F3%2F30%2F22358628%2Fverizon-3g-cdma-shutdown-date-2022&rfr_id=info%3Asid%2Fen.wikipedia.org%3ACode-division+multiple+access" class="Z3988"></span></span> </li> <li id="cite_note-Scholtz_1982May_IEEE-5"><span class="mw-cite-backlink"><b><a href="#cite_ref-Scholtz_1982May_IEEE_5-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFRobert_A._Scholtz1982" class="citation journal cs1">Robert A. Scholtz (May 1982). <a rel="nofollow" class="external text" href="https://ieeexplore.ieee.org/document/1095547">"The Origins of Spread-Spectrum Communications"</a>. <i><a href="/wiki/IEEE_Transactions_on_Communications" title="IEEE Transactions on Communications">IEEE Transactions on Communications</a></i>. <b>30</b> (5): <span class="nowrap">822–</span>854. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1109%2FTCOM.1982.1095547">10.1109/TCOM.1982.1095547</a><span class="reference-accessdate">. Retrieved <span class="nowrap">30 January</span> 2022</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=IEEE+Transactions+on+Communications&rft.atitle=The+Origins+of+Spread-Spectrum+Communications&rft.volume=30&rft.issue=5&rft.pages=%3Cspan+class%3D%22nowrap%22%3E822-%3C%2Fspan%3E854&rft.date=1982-05&rft_id=info%3Adoi%2F10.1109%2FTCOM.1982.1095547&rft.au=Robert+A.+Scholtz&rft_id=https%3A%2F%2Fieeexplore.ieee.org%2Fdocument%2F1095547&rfr_id=info%3Asid%2Fen.wikipedia.org%3ACode-division+multiple+access" class="Z3988"></span></span> </li> <li id="cite_note-Price_Shannon_19820728-6"><span class="mw-cite-backlink"><b><a href="#cite_ref-Price_Shannon_19820728_6-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFRobert_Price1982" class="citation web cs1">Robert Price (28 July 1982). <a rel="nofollow" class="external text" href="https://ethw.org/Oral-History:Claude_E._Shannon">"Oral-History: Claude E. Shannon"</a>. <a href="/wiki/Engineering_and_Technology_History_Wiki" title="Engineering and Technology History Wiki">Engineering and Technology History Wiki</a><span class="reference-accessdate">. Retrieved <span class="nowrap">30 January</span> 2022</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Oral-History%3A+Claude+E.+Shannon&rft.pub=Engineering+and+Technology+History+Wiki&rft.date=1982-07-28&rft.au=Robert+Price&rft_id=https%3A%2F%2Fethw.org%2FOral-History%3AClaude_E._Shannon&rfr_id=info%3Asid%2Fen.wikipedia.org%3ACode-division+multiple+access" class="Z3988"></span></span> </li> <li id="cite_note-7"><span class="mw-cite-backlink"><b><a href="#cite_ref-7">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFAgeev1935" class="citation journal cs1">Ageev, D. V. (1935). "Bases of the Theory of Linear Selection. Code Demultiplexing". <i>Proceedings of the Leningrad Experimental Institute of Communication</i>: <span class="nowrap">3–</span>35.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Proceedings+of+the+Leningrad+Experimental+Institute+of+Communication&rft.atitle=Bases+of+the+Theory+of+Linear+Selection.+Code+Demultiplexing&rft.pages=%3Cspan+class%3D%22nowrap%22%3E3-%3C%2Fspan%3E35&rft.date=1935&rft.aulast=Ageev&rft.aufirst=D.+V.&rfr_id=info%3Asid%2Fen.wikipedia.org%3ACode-division+multiple+access" class="Z3988"></span></span> </li> <li id="cite_note-8"><span class="mw-cite-backlink"><b><a href="#cite_ref-8">^</a></b></span> <span class="reference-text"><style data-mw-deduplicate="TemplateStyles:r1041539562">.mw-parser-output .citation{word-wrap:break-word}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}</style><span class="citation patent" id="CITEREFКуприянович_(Leonid_Kupriyanovich)1957"><a rel="nofollow" class="external text" href="https://patents.su/7-115494-ustrojjstva-vyzova-i-kommutacii-kanalov-radiotelefonnojj-svyazi.html">Soviet Union 115494</a>, Куприянович (Leonid Kupriyanovich), "Устройства вызова и коммутации каналов радиотелефонной связи (Devices for calling and switching radio communication channels)", published 1957-11-04</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Apatent&rft.number=115494&rft.cc=Soviet Union&rft.title=%D0%A3%D1%81%D1%82%D1%80%D0%BE%D0%B9%D1%81%D1%82%D0%B2%D0%B0+%D0%B2%D1%8B%D0%B7%D0%BE%D0%B2%D0%B0+%D0%B8+%D0%BA%D0%BE%D0%BC%D0%BC%D1%83%D1%82%D0%B0%D1%86%D0%B8%D0%B8+%D0%BA%D0%B0%D0%BD%D0%B0%D0%BB%D0%BE%D0%B2+%D1%80%D0%B0%D0%B4%D0%B8%D0%BE%D1%82%D0%B5%D0%BB%D0%B5%D1%84%D0%BE%D0%BD%D0%BD%D0%BE%D0%B9+%D1%81%D0%B2%D1%8F%D0%B7%D0%B8+%28Devices+for+calling+and+switching+radio+communication+channels%29&rft.inventor=%D0%9A%D1%83%D0%BF%D1%80%D0%B8%D1%8F%D0%BD%D0%BE%D0%B2%D0%B8%D1%87+%28Leonid+Kupriyanovich%29&rft.pubdate=1957-11-04"><span style="display: none;"> </span></span></span> </li> <li id="cite_note-9"><span class="mw-cite-backlink"><b><a href="#cite_ref-9">^</a></b></span> <span class="reference-text"><i><a href="/wiki/Nauka_i_Zhizn" title="Nauka i Zhizn">Nauka i Zhizn</a></i> 8, 1957, p. 49.</span> </li> <li id="cite_note-10"><span class="mw-cite-backlink"><b><a href="#cite_ref-10">^</a></b></span> <span class="reference-text"><i>Yuniy technik</i> 7, 1957, p. 43–44.</span> </li> <li id="cite_note-11"><span class="mw-cite-backlink"><b><a href="#cite_ref-11">^</a></b></span> <span class="reference-text"><i>Nauka i Zhizn</i> 10, 1958, p. 66.</span> </li> <li id="cite_note-12"><span class="mw-cite-backlink"><b><a href="#cite_ref-12">^</a></b></span> <span class="reference-text"><i><a href="/wiki/Tekhnika_Molodezhi" title="Tekhnika Molodezhi">Tekhnika Molodezhi</a></i> 2, 1959, p. 18–19.</span> </li> <li id="cite_note-13"><span class="mw-cite-backlink"><b><a href="#cite_ref-13">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://englishrussia.com/2006/09/18/first-russian-mobile-phone/">"First Russian Mobile Phone"</a>. September 18, 2006.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=First+Russian+Mobile+Phone&rft.date=2006-09-18&rft_id=http%3A%2F%2Fenglishrussia.com%2F2006%2F09%2F18%2Ffirst-russian-mobile-phone%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3ACode-division+multiple+access" class="Z3988"></span></span> </li> <li id="cite_note-14"><span class="mw-cite-backlink"><b><a href="#cite_ref-14">^</a></b></span> <span class="reference-text">M. Mazzella, M. Cohen, D. Rouffet, M. Louie and K. S. Gilhousen, "Multiple access techniques and spectrum utilisation of the GLOBALSTAR mobile satellite system," Fourth IEE Conference on Telecommunications 1993, Manchester, UK, 1993, pp. 306-311.</span> </li> <li id="cite_note-16"><span class="mw-cite-backlink"><b><a href="#cite_ref-16">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFHolmaToskala2007" class="citation book cs1">Holma, H.; Toskala, A., eds. (2007). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=7m-MnwW_o7AC&q=lte+umts+are+interference+limited&pg=PT439"><i>WCDMA for UMTS: HSPA Evolution and LTE</i></a>. <a href="/wiki/Wiley_(publisher)" title="Wiley (publisher)">John Wiley & Sons</a>. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/9781119991908" title="Special:BookSources/9781119991908"><bdi>9781119991908</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=WCDMA+for+UMTS%3A+HSPA+Evolution+and+LTE&rft.pub=John+Wiley+%26+Sons&rft.date=2007&rft.isbn=9781119991908&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3D7m-MnwW_o7AC%26q%3Dlte%2Bumts%2Bare%2Binterference%2Blimited%26pg%3DPT439&rfr_id=info%3Asid%2Fen.wikipedia.org%3ACode-division+multiple+access" class="Z3988"></span></span> </li> <li id="cite_note-17"><span class="mw-cite-backlink"><b><a href="#cite_ref-17">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFLaihoWackerNovosad2002" class="citation book cs1">Laiho, J.; Wacker, A.; Novosad, T., eds. (2002). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=9RE32TlXZBQC&q=is+umts+interference+limited+systems&pg=PA303"><i>Radio Network Planning and Optimisation for UMTS (Vol. 2)</i></a>. New York: <a href="/wiki/Wiley_(publisher)" title="Wiley (publisher)">John Wiley & Sons</a>. p. 303. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/9780470031391" title="Special:BookSources/9780470031391"><bdi>9780470031391</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Radio+Network+Planning+and+Optimisation+for+UMTS+%28Vol.+2%29&rft.place=New+York&rft.pages=303&rft.pub=John+Wiley+%26+Sons&rft.date=2002&rft.isbn=9780470031391&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3D9RE32TlXZBQC%26q%3Dis%2Bumts%2Binterference%2Blimited%2Bsystems%26pg%3DPA303&rfr_id=info%3Asid%2Fen.wikipedia.org%3ACode-division+multiple+access" class="Z3988"></span></span> </li> <li id="cite_note-Walke-Seidenberg-Althoff_2003-18"><span class="mw-cite-backlink"><b><a href="#cite_ref-Walke-Seidenberg-Althoff_2003_18-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFWalkeSeidenbergAlthoff2003" class="citation book cs1"><a href="/wiki/Bernhard_Walke" title="Bernhard Walke">Walke, Bernhard H.</a>; Seidenberg, Peter; Althoff, Marc Peter (March 2003) [2001]. <a rel="nofollow" class="external text" href="https://books.google.com/books?id=KRlUvPWeTYQC&pg=PA18"><i>UMTS: The Fundamentals</i></a>. Translated by von Schmoeger, Hedwig Jourdan (First English ed.). <a href="/wiki/John_Wiley_%26_Sons,_Ltd" class="mw-redirect" title="John Wiley & Sons, Ltd">John Wiley & Sons, Ltd</a>. pp. <span class="nowrap">18–</span>19. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-470-84557-0" title="Special:BookSources/0-470-84557-0"><bdi>0-470-84557-0</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=UMTS%3A+The+Fundamentals&rft.pages=%3Cspan+class%3D%22nowrap%22%3E18-%3C%2Fspan%3E19&rft.edition=First+English&rft.pub=John+Wiley+%26+Sons%2C+Ltd&rft.date=2003-03&rft.isbn=0-470-84557-0&rft.aulast=Walke&rft.aufirst=Bernhard+H.&rft.au=Seidenberg%2C+Peter&rft.au=Althoff%2C+Marc+Peter&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DKRlUvPWeTYQC%26pg%3DPA18&rfr_id=info%3Asid%2Fen.wikipedia.org%3ACode-division+multiple+access" class="Z3988"></span> (NB. Based on the 2001 German edition.)</span> </li> <li id="cite_note-ref_3-20"><span class="mw-cite-backlink">^ <a href="#cite_ref-ref_3_20-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-ref_3_20-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFSklarRay2014" class="citation book cs1">Sklar, Bernard; Ray, Pabitra K. (2014). <i>Digital Communications: Fundamentals and Applications, 2nd ed</i>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Digital+Communications%3A+Fundamentals+and+Applications%2C+2nd+ed.&rft.date=2014&rft.aulast=Sklar&rft.aufirst=Bernard&rft.au=Ray%2C+Pabitra+K.&rfr_id=info%3Asid%2Fen.wikipedia.org%3ACode-division+multiple+access" class="Z3988"></span></span> </li> <li id="cite_note-ref_4-21"><span class="mw-cite-backlink">^ <a href="#cite_ref-ref_4_21-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-ref_4_21-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFMolisch2010" class="citation book cs1">Molisch, Andreas (2010). <i>Wireless Communications, 2nd ed</i>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Wireless+Communications%2C+2nd+ed.&rft.date=2010&rft.aulast=Molisch&rft.aufirst=Andreas&rfr_id=info%3Asid%2Fen.wikipedia.org%3ACode-division+multiple+access" class="Z3988"></span></span> </li> <li id="cite_note-22"><span class="mw-cite-backlink"><b><a href="#cite_ref-22">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFEnneking,_Antreich,_Appel,_Almeida2019" class="citation conference cs1">Enneking, Antreich, Appel, Almeida (2019). <a rel="nofollow" class="external text" href="https://www.researchgate.net/publication/331065214">"Pure Pilot Signals: How short can we choose GNSS spreading codes?"</a>. <i>Proceedings of the 2019 International Technical Meeting of the Institute of Navigation</i>. pp. <span class="nowrap">925–</span>935. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.33012%2F2019.16737">10.33012/2019.16737</a>. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-936406-21-3" title="Special:BookSources/978-0-936406-21-3"><bdi>978-0-936406-21-3</bdi></a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:86666944">86666944</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=conference&rft.atitle=Pure+Pilot+Signals%3A+How+short+can+we+choose+GNSS+spreading+codes%3F&rft.btitle=Proceedings+of+the+2019+International+Technical+Meeting+of+the+Institute+of+Navigation&rft.pages=%3Cspan+class%3D%22nowrap%22%3E925-%3C%2Fspan%3E935&rft.date=2019&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A86666944%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.33012%2F2019.16737&rft.isbn=978-0-936406-21-3&rft.au=Enneking%2C+Antreich%2C+Appel%2C+Almeida&rft_id=https%3A%2F%2Fwww.researchgate.net%2Fpublication%2F331065214&rfr_id=info%3Asid%2Fen.wikipedia.org%3ACode-division+multiple+access" class="Z3988"></span><span class="cs1-maint citation-comment"><code class="cs1-code">{{<a href="/wiki/Template:Cite_conference" title="Template:Cite conference">cite conference</a>}}</code>: CS1 maint: multiple names: authors list (<a href="/wiki/Category:CS1_maint:_multiple_names:_authors_list" title="Category:CS1 maint: multiple names: authors list">link</a>)</span></span> </li> <li id="cite_note-23"><span class="mw-cite-backlink"><b><a href="#cite_ref-23">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFShakya2011" class="citation news cs1">Shakya, Indu L. (2011). "High User Capacity Collaborative CDMA". IET Communications.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=High+User+Capacity+Collaborative+CDMA&rft.date=2011&rft.aulast=Shakya&rft.aufirst=Indu+L.&rfr_id=info%3Asid%2Fen.wikipedia.org%3ACode-division+multiple+access" class="Z3988"></span></span> </li> </ol></div> <div class="mw-heading mw-heading2"><h2 id="Further_reading">Further reading</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Code-division_multiple_access&action=edit&section=17" title="Edit section: Further reading"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li>Papathanassiou, A., Salkintzis, A. K., & Mathiopoulos, P. T. (2001). <a rel="nofollow" class="external text" href="https://www.researchgate.net/publication/3344159_A_comparison_study_of_the_uplink_performance_of_W-CDMA_and_OFDM_for_mobile_multimedia_communications_via_LEO_satellites">"A comparison study of the uplink performance of W-CDMA and OFDM for mobile multimedia communications via LEO satellites"</a>. <i>IEEE Personal Communications</i>, 8(3), 35–43.</li></ul> <div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Code-division_multiple_access&action=edit&section=18" title="Edit section: External links"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1235681985">.mw-parser-output .side-box{margin:4px 0;box-sizing:border-box;border:1px solid #aaa;font-size:88%;line-height:1.25em;background-color:var(--background-color-interactive-subtle,#f8f9fa);display:flow-root}.mw-parser-output .side-box-abovebelow,.mw-parser-output .side-box-text{padding:0.25em 0.9em}.mw-parser-output .side-box-image{padding:2px 0 2px 0.9em;text-align:center}.mw-parser-output .side-box-imageright{padding:2px 0.9em 2px 0;text-align:center}@media(min-width:500px){.mw-parser-output .side-box-flex{display:flex;align-items:center}.mw-parser-output .side-box-text{flex:1;min-width:0}}@media(min-width:720px){.mw-parser-output .side-box{width:238px}.mw-parser-output .side-box-right{clear:right;float:right;margin-left:1em}.mw-parser-output .side-box-left{margin-right:1em}}</style><style data-mw-deduplicate="TemplateStyles:r1237033735">@media print{body.ns-0 .mw-parser-output .sistersitebox{display:none!important}}@media screen{html.skin-theme-clientpref-night .mw-parser-output .sistersitebox img[src*="Wiktionary-logo-en-v2.svg"]{background-color:white}}@media 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style="font-weight: bold; font-style: italic;"><a href="https://commons.wikimedia.org/wiki/Category:CDMA" class="extiw" title="commons:Category:CDMA">CDMA</a></span>.</div></div> </div> <ul><li><a rel="nofollow" class="external text" href="http://video.ias.edu/goresky-lecture-4-13">Talk at Princeton Institute for Advanced Study on Solomon Golomb's work on pseudorandom sequences</a></li></ul> <div class="navbox-styles"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><style data-mw-deduplicate="TemplateStyles:r1236075235">.mw-parser-output .navbox{box-sizing:border-box;border:1px solid #a2a9b1;width:100%;clear:both;font-size:88%;text-align:center;padding:1px;margin:1em auto 0}.mw-parser-output .navbox .navbox{margin-top:0}.mw-parser-output .navbox+.navbox,.mw-parser-output .navbox+.navbox-styles+.navbox{margin-top:-1px}.mw-parser-output .navbox-inner,.mw-parser-output .navbox-subgroup{width:100%}.mw-parser-output .navbox-group,.mw-parser-output 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rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1239400231"><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:CDMA" title="Template:CDMA"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:CDMA" title="Template talk:CDMA"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:CDMA" title="Special:EditPage/Template:CDMA"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="Spread_spectrum_in_digital_communications293" style="font-size:114%;margin:0 4em"><a href="/wiki/Spread_spectrum" title="Spread spectrum">Spread spectrum</a> in digital communications</div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%">Main articles</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Spread_spectrum" title="Spread spectrum">Spread spectrum</a></li> <li><a class="mw-selflink selflink">Code-division multiple access (CDMA)</a></li></ul> <dl><dt>History</dt> <dd><a href="/wiki/Spread_spectrum#Commercial_use" title="Spread spectrum">Commercial use</a></dd> <dd><a href="/wiki/Spread_spectrum#History" title="Spread spectrum">More...</a></dd></dl> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Spread spectrum <i>methods</i></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Direct-sequence_spread_spectrum" title="Direct-sequence spread spectrum">Direct-sequence spread spectrum</a> (DSSS)</li> <li><a href="/wiki/Frequency-hopping_spread_spectrum" title="Frequency-hopping spread spectrum">Frequency-hopping spread spectrum</a> (FHSS)</li> <li><a href="/wiki/Chirp_spread_spectrum" title="Chirp spread spectrum">Chirp spread spectrum</a> (CSS)</li> <li><a href="/wiki/Time-hopping" title="Time-hopping">Time-hopping spread spectrum</a> (THSS)</li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">CDMA <i>schemes</i></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/W-CDMA" class="mw-redirect" title="W-CDMA">W-CDMA</a></li> <li><a href="/wiki/TD-CDMA" class="mw-redirect" title="TD-CDMA">TD-CDMA</a></li> <li><a href="/wiki/TD-SCDMA" class="mw-redirect" title="TD-SCDMA">TD-SCDMA</a></li> <li><a href="/wiki/Direct-sequence_CDMA" class="mw-redirect" title="Direct-sequence CDMA">DS-CDMA</a></li> <li><a href="/wiki/Frequency-hopping_spread_spectrum" title="Frequency-hopping spread spectrum">FH-CDMA</a></li> <li><a href="/wiki/Multi-carrier_code-division_multiple_access" title="Multi-carrier code-division multiple access">MC-CDMA</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Major implementations</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Space_Network" title="Space Network">Space Network</a> (NASA)</li> <li><a href="/wiki/Global_Positioning_System" title="Global Positioning System">GPS</a></li> <li><a href="/wiki/Galileo_(satellite_navigation)" title="Galileo (satellite navigation)">Galileo</a></li> <li><a href="/wiki/GLONASS" title="GLONASS">GLONASS</a></li> <li><a href="/wiki/Bluetooth" title="Bluetooth">Bluetooth</a></li> <li><a href="/wiki/Cordless_telephone" title="Cordless telephone">Cordless phones</a>: <a href="/wiki/Digital_Enhanced_Cordless_Telecommunications" class="mw-redirect" title="Digital Enhanced Cordless Telecommunications">DECT</a></li></ul> <dl><dt><a href="/wiki/Mobile_phone" title="Mobile phone">Cellular</a></dt> <dd><a href="/wiki/Evolution-Data_Optimized" title="Evolution-Data Optimized">EV-DO</a> Mobile</dd> <dd><a href="/wiki/CdmaOne" title="CdmaOne">IS-95</a> (aka cdmaOne)</dd> <dd><a href="/wiki/CDMA2000" title="CDMA2000">CDMA2000</a> (aka IS-2000)</dd> <dt>Also</dt> <dd><a href="/wiki/Qualcomm" title="Qualcomm">Qualcomm</a></dd> <dd><a href="/wiki/Verizon_Wireless#Network" class="mw-redirect" title="Verizon Wireless">Verizon</a></dd></dl> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Major concepts</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Pseudorandom_noise#PN_Code" title="Pseudorandom noise">PN (pseudorandom noise) code</a></li> <li><a href="/wiki/Chip_(CDMA)" title="Chip (CDMA)">Chip</a></li> <li><a href="/wiki/Near%E2%80%93far_problem" title="Near–far problem">Near–far problem</a></li> <li><a href="/wiki/Spectral_density" title="Spectral density">Power spectral density</a> (PSD)</li> <li><a href="/wiki/Process_gain" title="Process gain">Process gain</a></li> <li><a href="/wiki/Rake_receiver" title="Rake receiver">Rake receiver</a></li> <li><a href="/wiki/Low_probability_of_intercept" class="mw-redirect" title="Low probability of intercept">Low probability of intercept</a></li></ul> </div></td></tr><tr><td class="navbox-abovebelow" colspan="2"><div> <dl><dt>See also</dt> <dd><a href="/wiki/Data_transmission" class="mw-redirect" title="Data transmission">Digital communication</a></dd> <dd><a href="/wiki/Modulation" title="Modulation">Modulation</a></dd> <dd><a href="/wiki/Statistical_time-division_multiplexing" title="Statistical time-division multiplexing">Statistical multiplexing</a></dd> <dd><a href="/wiki/Waveform" title="Waveform">Waveform</a></dd></dl> </div></td></tr></tbody></table></div> <div class="navbox-styles"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236075235"></div><div role="navigation" class="navbox" aria-labelledby="Channel_access_methods_and_media_access_control194" style="padding:3px"><table class="nowraplinks mw-collapsible autocollapse navbox-inner" style="border-spacing:0;background:transparent;color:inherit"><tbody><tr><th scope="col" class="navbox-title" colspan="2"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1239400231"><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:Channel_access_methods" title="Template:Channel access methods"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Channel_access_methods" title="Template talk:Channel access methods"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Channel_access_methods" title="Special:EditPage/Template:Channel access methods"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="Channel_access_methods_and_media_access_control194" style="font-size:114%;margin:0 4em"><a href="/wiki/Channel_access_method" title="Channel access method">Channel access methods</a> and <a href="/wiki/Medium_access_control" title="Medium access control">media access control</a></div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Circuit_switching" title="Circuit switching">Channel-based</a></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Frequency-division_multiple_access" title="Frequency-division multiple access">FDMA</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Frequency-division_multiplexing" title="Frequency-division multiplexing">FDM</a> <ul><li><a href="/wiki/Orthogonal_frequency-division_multiple_access" title="Orthogonal frequency-division multiple access">OFDMA</a></li> <li><a href="/wiki/Single-carrier_FDMA" title="Single-carrier FDMA">SC-FDMA</a></li></ul></li> <li><a href="/wiki/Wavelength-division_multiplexing" title="Wavelength-division multiplexing">WDM</a> <ul><li><a href="/wiki/Wavelength-division_multiple_access" class="mw-redirect" title="Wavelength-division multiple access">WDMA</a></li></ul></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Time-division_multiple_access" title="Time-division multiple access">TDMA</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Multi-frequency_time-division_multiple_access" title="Multi-frequency time-division multiple access">MF-TDMA</a></li> <li><a href="/wiki/Self-organized_time-division_multiple_access" title="Self-organized time-division multiple access">STDMA</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a class="mw-selflink selflink">CDMA</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/W-CDMA" class="mw-redirect" title="W-CDMA">W-CDMA</a></li> <li><a href="/wiki/TD-CDMA" class="mw-redirect" title="TD-CDMA">TD-CDMA</a></li> <li><a href="/wiki/TD-SCDMA" class="mw-redirect" title="TD-SCDMA">TD-SCDMA</a></li> <li><a href="/wiki/Direct-sequence_spread_spectrum" title="Direct-sequence spread spectrum">DS-CDMA</a></li> <li><a href="/wiki/Frequency-hopping_spread_spectrum" title="Frequency-hopping spread spectrum">FH-CDMA</a></li> <li><a href="/wiki/Multi-carrier_code-division_multiple_access" title="Multi-carrier code-division multiple access">MC-CDMA</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Space-division_multiple_access" title="Space-division multiple access">SDMA</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/IBurst" class="mw-redirect" title="IBurst">HC-SDMA</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Polarization-division_multiple_access" title="Polarization-division multiple access">PDMA</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li class="mw-empty-elt"></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Pulse-address_multiple_access" title="Pulse-address multiple access">PAMA</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li class="mw-empty-elt"></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Packet_switching" title="Packet switching">Packet-based</a></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Contention_(telecommunications)" title="Contention (telecommunications)">Collision recovery</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/ALOHAnet#The_ALOHA_protocol" title="ALOHAnet">ALOHA</a></li> <li><a href="/wiki/ALOHAnet" title="ALOHAnet">Slotted ALOHA</a></li> <li><a href="/wiki/Reservation_ALOHA" class="mw-redirect" title="Reservation ALOHA">R-ALOHA</a></li> <li><a href="/wiki/AX.25" title="AX.25">AX.25</a></li> <li><a href="/wiki/Carrier-sense_multiple_access_with_collision_detection" title="Carrier-sense multiple access with collision detection">CSMA/CD</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Contention_(telecommunications)" title="Contention (telecommunications)">Collision avoidance</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Multiple_Access_with_Collision_Avoidance" class="mw-redirect" title="Multiple Access with Collision Avoidance">MACA</a></li> <li><a href="/wiki/Multiple_Access_with_Collision_Avoidance_for_Wireless" title="Multiple Access with Collision Avoidance for Wireless">MACAW</a></li> <li><a href="/wiki/Carrier-sense_multiple_access" title="Carrier-sense multiple access">CSMA</a></li> <li><a href="/wiki/Carrier-sense_multiple_access_with_collision_avoidance" title="Carrier-sense multiple access with collision avoidance">CSMA/CA</a></li> <li><a href="/wiki/Distributed_coordination_function" title="Distributed coordination function">DCF</a></li> <li><a href="/wiki/Point_coordination_function" title="Point coordination function">PCF</a></li> <li><a href="/wiki/IEEE_802.11e-2005#802.11e_MAC_protocol_operation" title="IEEE 802.11e-2005">HCF</a></li> <li><a href="/wiki/CSMA/CARP" class="mw-redirect" title="CSMA/CARP">CSMA/CARP</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Collision_domain" title="Collision domain">Collision-free</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Token_Ring" title="Token Ring">Token Ring</a></li> <li><a href="/wiki/Token_bus_network" title="Token bus network">Token bus</a></li> <li><a href="/wiki/Mobile_Slotted_Aloha" title="Mobile Slotted Aloha">MS-ALOHA</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Delay and disruption tolerant</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Mobile_ad_hoc_network" class="mw-redirect" title="Mobile ad hoc network">MANET</a></li> <li><a href="/wiki/Vehicular_ad-hoc_network" class="mw-redirect" title="Vehicular ad-hoc network">VANET</a></li> <li><a href="/wiki/Delay-tolerant_networking" title="Delay-tolerant networking">DTN</a></li> <li><a href="/wiki/Dynamic_Source_Routing" title="Dynamic Source Routing">Dynamic Source Routing</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Duplex_(telecommunications)" title="Duplex (telecommunications)">Duplexing methods</a></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Duplex_(telecommunications)#Time-division_duplexing" title="Duplex (telecommunications)">TDD</a></li> <li><a href="/wiki/Duplex_(telecommunications)#Frequency-division_duplexing" title="Duplex (telecommunications)">FDD</a></li></ul> </div></td></tr></tbody></table></div> <div class="navbox-styles"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236075235"></div><div role="navigation" class="navbox authority-control" aria-labelledby="Authority_control_databases_frameless&#124;text-top&#124;10px&#124;alt=Edit_this_at_Wikidata&#124;link=https&#58;//www.wikidata.org/wiki/Q233394#identifiers&#124;class=noprint&#124;Edit_this_at_Wikidata939" style="padding:3px"><table 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