IP Multimedia Subsystem

The IP Multimedia Subsystem or IP Multimedia Core Network Subsystem (IMS) is a standardised <a href="/facts/Architectural_Framework/kq1FCjjT">architectural framework</a> for delivering IP <a href="/facts/Multimedia/PtJteq27">multimedia</a> services. Historically, mobile phones have provided voice call services over a <a href="/facts/Circuit_switching/fJ3vdmAB">circuit-switched</a>-style network, rather than strictly over an IP <a href="/facts/Packet_switching/olDlDP1R">packet-switched</a> network. Various <a href="/facts/Voice_over_IP/5QGBbXYg">voice over IP</a> technologies are available on smartphones; IMS provides a standard protocol across vendors.
IMS was originally designed by the wireless <a href="/facts/Standardization/vS9AhNMS">standards</a> body <a href="/facts/3rd_Generation_Partnership_Project/TBrQYKFF">3rd Generation Partnership Project</a> (3GPP), as a part of the vision for evolving mobile networks beyond <a href="/facts/GSM/Sw8QYaLE">GSM</a>. Its original formulation (3GPP Rel-5) represented an approach for delivering Internet services over <a href="/facts/GPRS/c4SJD7ov">GPRS</a>. This vision was later updated by 3GPP, <a href="/facts/3GPP2/6bNoq0n6">3GPP2</a> and <a href="/facts/European_Telecommunications_Standards_Institute/8rJbbhPg">ETSI</a> <a href="/facts/TISPAN/s6cW2V2X">TISPAN</a> by requiring support of networks other than <a href="/facts/GPRS/c4SJD7ov">GPRS</a>, such as <a href="/facts/Wireless_LAN/ooq0WA45">Wireless LAN</a>, <a href="/facts/CDMA2000/yF4B3rfl">CDMA2000</a> and fixed lines.
IMS uses <a href="/facts/IETF/tIcCsFhX">IETF</a> protocols wherever possible, e.g., the <a href="/facts/Session_Initiation_Protocol/cbjUoNqP">Session Initiation Protocol</a> (SIP). According to the 3GPP, IMS is not intended to standardize applications, but rather to aid the access of multimedia and voice applications from wireless and wireline terminals, i.e., to create a form of <a href="/facts/Fixed%25E2%2580%2593mobile_convergence/MjWyo6IJ">fixed-mobile convergence</a> (FMC). This is done by having a horizontal control layer that isolates the access network from the <a href="/facts/Service_layer/JPBlfdIH">service layer</a>. From a logical architecture perspective, services need not have their own control functions, as the control layer is a common horizontal layer. However, in implementation this does not necessarily map into greater reduced cost and complexity.
Alternative and overlapping technologies for access and provisioning of services across wired and wireless networks include combinations of <a href="/facts/Generic_Access_Network/M9feWpTK">Generic Access Network</a>, <a href="/facts/Softswitch/zffbQ7h5">softswitches</a> and "naked" SIP.
Since it is becoming increasingly easier to access content and contacts using mechanisms outside the control of traditional wireless/fixed operators, the interest of IMS is being challenged.
Examples of global standards based on IMS are <a href="/facts/Multimedia_telephony/zq0eGV2G">MMTel</a> which is the basis for Voice over LTE (<a href="/facts/VoLTE/Rp3slvPE">VoLTE</a>), <a href="/facts/Generic_Access_Network/M9feWpTK">Wi-Fi Calling</a> (VoWIFI), <a href="/facts/Video_over_LTE/lTVMucg4">Video over LTE</a> (ViLTE), SMS/MMS over WiFi and LTE, <a href="/facts/USSD/2ACw7CYY">Unstructured Supplementary Service Data</a> (USSD) over LTE, and <a href="/facts/Rich_Communication_Services/sI5UAdvy">Rich Communication Services</a> (RCS), which is also known as joyn or Advanced Messaging, and now RCS is operator's implementation. RCS also further added Presence/EAB (enhanced address book) functionality.

IP Multimedia Subsystem open-in-new

IP Multimedia Subsystem