International Mobile Telecommunications-Advanced (IMT-Advanced) are requirements issued by the ITU-R of the International Telecommunication Union (ITU) in 2008 for what is marketed as 4G mobile phone and Internet access service.
An IMT-Advanced system is expected to provide a comprehensive and secure all-IP based mobile broadband solution to laptop computer wireless modems, smartphones, and other mobile devices. Facilities such as ultra-broadband Internet access, IP telephony, gaming services, and streamed multimedia may be provided to users.
IMT-Advanced intended to accommodate the quality of service (QoS) and rate requirements set by further development of applications like mobile broadband access, Multimedia Messaging Service (MMS), video chat, mobile TV, but also new services like High-definition television (HDTV). 4G may allow roaming with wireless local area networks, and may interact with digital video broadcasting systems. It was meant to go beyond the International Mobile Telecommunications-2000 requirements, which specify mobile phones systems marketed as 3G.
Specific requirements of the IMT-Advanced report included:
- Based on an all-Internet Protocol (IP) packet switched network
- Interoperability with existing wireless standards
- A nominal data rate of 100 Mbit/s while the client physically moves at high speeds relative to the station, and 1 Gbit/s while client and station are in relatively fixed positions.
- Dynamically share and use the network resources to support more simultaneous users per cell.
- Scalable channel bandwidth 5–20 MHz, optionally up to 40 MHz
- Peak link spectral efficiency of 15 bit/s/Hz in the downlink, and 6.75 bit/s/Hz in the uplink (meaning that 1 Gbit/s in the downlink should be possible over less than 67 MHz bandwidth)
- System spectral efficiency of up to 3 bit/s/Hz/cell in the downlink and 2.25 bit/s/Hz/cell for indoor usage
- Seamless connectivity and global roaming across multiple networks with smooth handovers
- Ability to offer high quality of service for multimedia support
The first set of 3GPP requirements on LTE Advanced was approved in June 2008.
A summary of the technologies that have been studied as the basis for LTE Advanced is included in a technical report.
While the ITU adopts requirements and recommendations for technologies that would be used for future communications, they do not actually perform the development work themselves, and countries do not consider them binding standards. Other trade groups and standards bodies such as the Institute of Electrical and Electronics Engineers (IEEE), the WiMAX Forum and 3GPP also have a role.
Physical layer transmission techniques expected to be used include:
- MIMO: To attain ultra high spectral efficiency by means of spatial processing including multi-antenna and multi-user MIMO
- Frequency-domain-equalization, for example Multi-carrier modulation (OFDM) in the downlink or single-carrier frequency-domain-equalization (SC-FDE) in the uplink: To exploit the frequency selective channel property without complex equalization.
- Frequency-domain statistical multiplexing, for example (OFDMA) or (Single-carrier FDMA) (SC-FDMA, Linearly precoded OFDMA, LP-OFDMA) in the uplink: Variable bit rate by assigning different sub-channels to different users based on the channel conditions
- Turbo principle error-correcting codes: To minimize the required SNR at the reception side
- Channel-dependent scheduling: To utilize the time-varying channel.
- Link adaptation: Adaptive modulation and error-correcting codes
- Relaying, including fixed relay networks (FRNs), and the cooperative relaying concept, known as multi-mode protocol
LTE has a theoretical net bit rate capacity of up to 100 Mbit/s in the downlink and 50 Mbit/s in the uplink if a 20 MHz channel is used — and more if multiple-input multiple-output (MIMO) antenna arrays, are used.
The CDMA spread spectrum radio technology used in 3G systems and IS-95 is abandoned and replaced by OFDMA and other frequency-domain equalization schemes. This is combined with MIMO (Multiple In Multiple Out), antenna arrays, dynamic channel allocation and channel-dependent scheduling.
The first publicly available LTE service was opened in the two Scandinavian capitals Stockholm (Ericsson system) and Oslo (a Huawei system) on 14 December 2009, and branded 4G. The user terminals were manufactured by Samsung. Currently, the three publicly available LTE services in the United States are provided by MetroPCS, Verizon Wireless, and AT&T Mobility.
In South Korea, SK Telecom and LG U+ have enabled access to LTE service since July 2011 for data devices, slated to go nationwide by 2012.
Mobile WiMAX (IEEE 802.16e)
The Mobile WiMAX (IEEE 802.16e-2005) mobile wireless broadband access (MWBA) standard (marketed as WiBro in South Korea) is sometimes branded 4G, and offers peak data rates of 128 Mbit/s downlink and 56 Mbit/s uplink over 20 MHz wide channels.
|Peak Download||128 Mbit/s|
|Peak Upload||56 Mbit/s|
Ultra Mobile Broadband
Ultra Mobile Broadband (UMB) was the brand name for a discontinued 4G project within the 3GPP2 standardization group to improve the CDMA2000 mobile phone standard for next generation applications and requirements. In November 2008, Qualcomm, UMB's lead sponsor, announced it was ending development of the technology, favouring LTE instead. The objective was to achieve data speeds over 275 Mbit/s downstream and over 75 Mbit/s upstream.
At an early stage the Flash-OFDM system was expected to be further developed into a 4G standard.
iBurst and MBWA
The iBurst technology, using High Capacity Spatial Division Multiple Access (HC-SDMA), was at an early stage considered as a 4G predecessor. It was incorporated by the Mobile Broadband Wireless Access (MBWA) working group into the IEEE 802.20 standard in 2008.
In October 2010, ITU-R Working Party 5D approved two industry-developed technologies. On December 6, 2010, ITU noted that while current versions of LTE, WiMax and other evolved 3G technologies do not fulfill IMT-Advanced requirements for 4G, some may use the term "4G" in an "undefined" fashion to represent forerunners to IMT-Advanced that show "a substantial level of improvement in performance and capabilities with respect to the initial third generation systems now deployed."
LTE Advanced (Long-term-evolution Advanced) was formally submitted by the 3GPP organization to ITU-T in the fall 2009, and expected to be released in 2012. The target of 3GPP LTE Advanced was to reach and surpass the ITU requirements. LTE Advanced is an improvement on the existing LTE network. Release 10 of LTE is expected to achieve the LTE Advanced speeds. Release 8 in 2009 supported up to 300 Mbit/s download speeds which was still short of the IMT-Advanced standards.
WiMAX Release 2 (IEEE 802.16m)
The WirelessMAN-Advanced evolution of IEEE 802.16e was published in May 2011 as standard IEEE 802.16m-2011. The relevant industry promoting the technology gave it the marketing name of WiMAX Release 2. It had an objective to fulfill the IMT-Advanced criteria. The IMT-Advanced group formally approved this technology as meeting its criteria in October 2010.
The following table shows a comparison of IMT-Advanced candidate systems as well as other competing technologies.
|Family||Primary Use||Radio Tech||Downstream
|HSPA+ is widely deployed. Revision 11 of the 3GPP states that HSPA+ is expected to have a throughput capacity of 672 Mbit/s.|
|LTE||3GPP||General 4G||OFDMA/MIMO/SC-FDMA||100 Cat3
(in 20 MHz FDD) 
(in 20 MHz FDD)
|LTE-Advanced update expected to offer peak rates up to 1 Gbit/s fixed speeds and 100 Mb/s to mobile users.|
|WiMax rel 1||802.16||WirelessMAN||MIMO-SOFDMA||37 (10 MHz TDD)||17 (10 MHz TDD)||With 2x2 MIMO.|
|WiMax rel 1.5||802.16-2009||WirelessMAN||MIMO-SOFDMA||83 (20 MHz TDD)
141 (2x20 MHz FDD)
|46 (20 MHz TDD)
138 (2x20 MHz FDD)
|With 2x2 MIMO.Enhanced with 20 MHz channels in 802.16-2009|
|WiMAX rel 2||802.16m||WirelessMAN||MIMO-SOFDMA||2x2 MIMO
110 (20 MHz TDD)
183 (2x20 MHz FDD)
219 (20 MHz TDD)
365 (2x20 MHz FDD)
70 (20 MHz TDD)
188 (2x20 MHz FDD)
140 (20 MHz TDD)
376 (2x20 MHz FDD)
|Also, low mobility users can aggregate multiple channels to get a download throughput of up to 1 Gbit/s|
mobility up to 200 mph (350 km/h)
|Mobile range 30 km (18 miles)
extended range 55 km (34 miles)
|Mobile Internet||OFDM/MIMO||288.8 (using 4x4 configuration in 20 MHz bandwidth) or 600 (using 4x4 configuration in 40 MHz bandwidth)|
|iBurst||802.20||Mobile Internet||HC-SDMA/TDD/MIMO||95||36||Cell Radius: 3–12 km
Speed: 250 km/h
Spectral Efficiency: 13 bits/s/Hz/cell
Spectrum Reuse Factor: "1"
|EDGE Evolution||GSM||Mobile Internet||TDMA/FDD||1.6||0.5||3GPP Release 7|
|HSDPA is widely deployed. Typical downlink rates today 2 Mbit/s, ~200 kbit/s uplink; HSPA+ downlink up to 56 Mbit/s.|
|UMTS-TDD||UMTS/3GSM||Mobile Internet||CDMA/TDD||16||Reported speeds according to IPWireless using 16QAM modulation similar to HSDPA+HSUPA|
|EV-DO Rel. 0
|Rev B note: N is the number of 1.25 MHz carriers used. EV-DO is not designed for voice, and requires a fallback to 1xRTT when a voice call is placed or received.|
Notes: All speeds are theoretical maximums and will vary by a number of factors, including the use of external antennas, distance from the tower and the ground speed (e.g. communications on a train may be poorer than when standing still). Usually the bandwidth is shared between several terminals. The performance of each technology is determined by a number of constraints, including the spectral efficiency of the technology, the cell sizes used, and the amount of spectrum available. For more information, see Comparison of wireless data standards.
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