Editing 4G (section)

== Technical overview ==
In November 2008, the [[ITU-R|International Telecommunication Union-Radio communications sector]] (ITU-R) specified a set of requirements for 4G standards, named the International Mobile Telecommunications Advanced (IMT-Advanced) specification, setting peak speed requirements for 4G service at 100 [[megabits per second]] (Mbit/s)(=12.5 megabytes per second) for high mobility communication (such as from trains and cars) and 1 [[gigabit per second]] (Gbit/s) for low mobility communication (such as pedestrians and stationary users).<ref name="IMT-Advanced-requirements">[[ITU-R]], [http://www.itu.int/pub/R-REP-M.2134-2008/en Report M.2134, Requirements related to technical performance for IMT-Advanced radio interface(s)], Approved in November 2008</ref>

Since the first-release versions of [[Mobile WiMAX]] and [[Long Term Evolution|LTE]] support much less than 1&nbsp;Gbit/s peak bit rate, they are not fully IMT-Advanced compliant, but are often branded 4G by service providers. According to operators, a generation of the network refers to the deployment of a new non-backward-compatible technology. On December 6, 2010, ITU-R recognized that these two technologies, as well as other beyond-3G technologies that do not fulfill the IMT-Advanced requirements, could nevertheless be considered "4G", provided they represent forerunners to IMT-Advanced compliant versions and "a substantial level of improvement in performance and capabilities with respect to the initial third generation systems now deployed". Both the original LTE and WiMAX standards had previously sometimes been referred to as 3.9G/3.95G.<ref name=":0">{{Cite web |last=updated |first=Dale Walker last |date=2019-09-25 |title=What is LTE? |url=https://www.itpro.com/network-internet/34492/what-is-lte |access-date=2025-02-26 |website=ITPro |language=en}}</ref><ref name=":1">{{Cite web |last=admin-ectnews |date=2008-07-23 |title=The Road to 4G: WiMax Leads the Way |url=https://www.technewsworld.com/story/the-road-to-4g-wimax-leads-the-way-63903.html |access-date=2025-02-26 |website=TechNewsWorld |language=en-US}}</ref> The ITU's new definition for 4G also included [[Evolved High Speed Packet Access]] (HSPA+).<ref>{{cite web |date=December 18, 2010 |title=ITU says LTE, WiMax and HSPA+ are now officially 4G |url=https://www.phonearena.com/news/ITU-says-LTE-WiMax-and-HSPA--are-now-officially-4G_id15435 |access-date=19 June 2022 |website=phonearena.com}}</ref> 

[[Mobile WiMAX Release 2]] (also known as ''WirelessMAN-Advanced'' or ''IEEE 802.16m'') and [[LTE Advanced]]
(LTE-A) are IMT-Advanced compliant backwards compatible versions of the above two systems, standardized during the spring 2011,{{citation needed|date=March 2012}} and promising speeds in the order of 1&nbsp;Gbit/s. In January 2012, the ITU backtracked on its previous definition for 4G, claiming that Mobile WiMAX 2 and LTE Advanced are "true 4G" while their predecessors are "transitional" 3G-4G.<ref name=":2">{{Cite web |last=Gompa |first=Neal |date=2012-01-23 |title=ITU designates LTE-Advanced as "True 4G" |url=https://www.extremetech.com/internet/114953-itu-designates-lte-advanced-as-true-4g |access-date=2025-02-26 |website=ExtremeTech |language=en}}</ref>

As opposed to earlier generations, a 4G system does not support traditional [[circuit-switched]] telephony service, but instead relies on all-[[Internet Protocol]] (IP) based communication such as [[IP telephony]]. As seen below, the [[spread spectrum]] radio technology used in 3G systems is abandoned in all 4G candidate systems and replaced by [[OFDMA]] [[multi-carrier]] transmission and other [[single-carrier FDMA|frequency-domain equalization]] (FDE) schemes, making it possible to transfer very high bit rates despite extensive [[multipath propagation|multi-path radio propagation]] (echoes). The peak bit rate is further improved by [[smart antenna]] arrays for [[MIMO|multiple-input multiple-output]] (MIMO) communications.