4G will be technically defined by what the ITU qualifies as IMT-Advanced (with IMT 2000 being 3G), neither LTE nor WiMAX look to actually be 4G.
802.16m (802.16m Advanced Air Interface with data rates of 100 Mbit/s mobile & 1 Gbit/s fixed is an in progress standard) and LTE-AdvancedA will make the grade as true 4G.
LTE Advanced is a preliminary mobile communication standard, formally submitted as a candidate 4G systems to ITU-T in the fall 2009, and expected to be finalized in 2011. It is standardized by the 3rd Generation Partnership Project (3GPP) as a major enhancement of the pre-4G 3GPP Long Term Evolution (LTE) standard. A first set of 3GPP requirements on LTE Advanced has been approved in June 2008. Besides the peak data rate 1 Gbit/s that fully supports the 4G requirements as defined by the ITU-R, it also targets faster switching between power states and improved performance at the cell edge. LTE Advanced introduces multicarrier to be able to leverage ultra wide bandwidth, up to 100 MHz of spectrum supporting very high data rates. One of the important LTE Advanced benefits is the ability to leverage advanced topology networks; optimized heterogeneous networks with a mix of macros with low power nodes such as picocells, femtocells and new relay nodes.
Here is some more info about LTE advanced.
Currently some of the main headline aims for LTE Advanced can be seen below:
1.Peak data rates: downlink – 1 Gbps; uplink – 500 Mbps.
2.Spectrum efficiency: 3 times greater than LTE.
3.Peak spectrum efficiency: downlink – 30 bps/Hz; uplink – 15 bps/Hz.
4.Spectrum use: the ability to support scalable bandwidth use and spectrum aggregation where non-contiguous spectrum needs to be used.
5.Latency: from Idle to Connected in less than 50 ms and then shorter than 5 ms one way for individual packet transmission.
6.Cell edge user throughput to be twice that of LTE.
7.Average user throughput to be 3 times that of LTE.
8.Mobility: Same as that in LTE
9.Compatibility: LTE Advanced shall be capable of interworking with LTE and 3GPP legacy systems.