IMT Advanced incorporates two different 4G standards, one based on WiMax and one based on LTE.
LTE-Advanced” (based on LTE) and WirelessMAN-Advanced” (based on WiMAX), have been accorded the official designation of IMT-Advanced, qualifying them as true 4G technologies.
LTE and WiMAX are often called “4G”, but they are not really “official” 4G standards, insists the ITU. IMT Advanced is the first “real” 4G standard – the next step in global wireless broadband communications beyond 3G.
|Core networks||IP based|
|Data rates||100 Mbps to 1 GHz|
|Access methods||OFDMA, SC- FDMA, OFDM-TDMA|
|Radio Interface||Cognitive radios, software defined radios.|
|Modulation||QPSK, 16QAM, 64QAM, DAPSK|
|Services provided||Rich multimedia, voice, high speed data.|
|Duplex methods||FDD(paired, unpaired), TDD|
|Error control||LDPC, turbo codes, HARQ|
|Handover||Seamless, vertical, horizontal, hard, soft|
UMTS and CDMA2000 are the international 3G standards. The ITU requires 100 Mbps (mobile) and 1 Gbps (fixed) speeds, among other criteria, to qualify as true “4G”. That’s about 3 times the speed of today’s LTE and WiMAX systems. IMT-Advanced also features many technical refinements enabling more flexible and cost/effective wireless broadband.
IMT-Advanced technologies use spectrum more efficiently, can gang different frequency bands together, and can utilize 4X4 MIMO (even 8×8) antennas for faster speeds and more capacity.
The ITU is a United Nations telecommunications body that gives final approval for global telecommunications standards. Equipment makers will now be able to build to the more advanced standards.
LTE Advanced was formally submitted as a candidate 4G system to ITU-T in late 2009, and IMT-Advanced was finalized by 3GPP in March 2011.
Clearwire said it will deploy LTE Advanced in a TDD-LTE overlay on top of its mobile WiMAX network. Sprint Nextel said in October it will deploy LTE Advanced on its 800 MHz spectrum by the first half of 2013. AT&T Mobility has said it will launch LTE Advanced in 2013. Verizon Wireless has not yet announced when it might deploy LTE Advanced.
LTE-Advanced (LTE-A) comes in both Time Division (TD-LTE) and Frequency Division (FD-LTE) flavors. The standard also incorporates important features such “relay stations”, that can act as repeaters, that use part of their 4G spectrum to “self-backhaul”.
AT&T likes LTE-A because it allows “carrier aggregation” so it can combine its current 700 MHz LTE service with their nationwide 6 MHz downstream-only channel that it bought from Qualcomm. LTE-A lets carriers like Sprint use spectrum more flexibility and efficiently.
Clearwire and China Mobile, the world’s largest mobile network, are members of the Global TD-LTE Initiative which plan globally harmonized TD-LTE devices using the 2.3GHz and 2.7GHz frequency bands. Clearwire expects to to offer IMT-Advanced services later this year.
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