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opposed to the version with 256 sub-carriers (of which 200 are used) in 802.16d. More advanced versions, including 802.16e, also bring Multiple Antenna Support through MIMO (Multi-In Multi-Out). This brings potential benefits in terms of coverage, self installation, power consumption, frequency re-use and bandwidth efficiency.
LTE and WiMax will probably address all market requirements for the next decade. After that, operators may deploy Fourth Generation (4G) networks using LTE-Advanced or WiMax II technology as a foundation. Currently, there are no official standards or formal definitions for 4G. Preliminary research is focused on technologies capable of delivering peak rates of 1 gigabit per second (Gbps) in hotspot type scenarios and 100 Mbps while mobile, being fully IP-based, and supporting full network agility for handovers between different types of networks (for example, 4G to 3G to WLAN). The high data rates for LTE will require radio channels wider than 20MHz, which is why the FCC recently auctioned blocks in the 700Mhz band in the USA. WiMax will continue in the 2.3-2.7Ghz, and 3.4-3.7Ghz ranges, although there may be future availability in the 500-800Mhz in the USA.
 Some companies are attempting to co-opt the term “4G” to refer to wireless systems that promise performance beyond current 3G systems. All of these systems are on par with HSPA/HSPA+ and LTE, however, and use of the term “4G” for them is inappropriate. ITU is the internationally recognized organization producing the official definition of next-generation wireless technologies. Through its Radio Communications Sector (ITU-R), ITU is currently working on a definition of 4G using the name IMT-Advanced.
The IMT-Advanced project schedule showed the requirements and evaluation criteria being published in 2008 with submissions to occur through 2009. 3GPP will address the
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Currently, there are no official standards or formal definitions for 4G. |
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requirements in a version of LTE called LTE Advanced for which specifications could become available in 2011. 3GPP will specify LTE Advanced in Release 10. WiMAX will address the IMT-Advanced requirements in a version called Mobile WiMAX 2.0, to be specified in IEEE 802.16m.
No details are available yet on these advanced technologies, but ideas under consideration include:
- Evolution of current OFDMA approaches
- High-order MIMO (e.g., 4X4)
- Wider radio channels (e.g., 50 to 100 MHz)
- Optimization in narrower bands (e.g., less than 20 MHz) due to spectrum
- constraints in some deployments
- Multi-channel operation in either same or different frequency bands
- Ability to share bands with other services
The Competition: LTE vs. WiMax
Whilst a number of analysts say that these technologies complement each other, there have been a number of changes in the schedules of networks looking to offer LTE, in response to the launch by Sprint and Clearwire of their WiMax networks. With Qualcomm opting to halt research in UMB, the choice may now come down to a straight subscriber number fight between mobile operators.
There are over 3 billion mobile subscribers today operating on GSM/UMTS, against less than 10 million in the world who are using WiMax. As the majority of network operators who have made a decision have opted for LTE as the future technology, and this represents the least amount of change for them in the way they manage their networks, the likelihood is that this will become the dominant technology. The economies of scale, and firm support for LTE from the majority of mobile vendors, along with a scarcity of WiMax capable handsets, (Nokia recently stopped production on their only one), will hamper the success of the WiMax standard, and may relegate it to more of a fixed wireless technology than mobile.
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