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Message: <blockquote data-quote="nagaya" data-source="post: 1897587" data-attributes="member: 23839">3G and 4G cellular phone systemsBoth major 3G systems, CDMA2000 and UMTS, compete with WiMAX. Both aim to offer DSL-class Internet access in addition to phone service. UMTS has also been enhanced to compete directly with WiMAX in the form of UMTS-TDD, which can use WiMAX oriented spectrum and provides a more consistent, if lower bandwidth at peak, user experience than WiMAX.3G cellular phone systems usually benefit from already having entrenched infrastructure, being upgraded from earlier systems. Users can usually fall back to older systems when they move out of range of upgraded equipment, often relatively seamlessly.The major cellular standards are being evolved to so-called 4G, high bandwidth, low latency, all-IP networks with voice services built on top. With GSM/UMTS, the move to 4G is the 3GPP Long Term Evolution effort. For AMPS/TIA derived standards such as CDMA2000, a replacement called Ultra Mobile Broadband is under development. In both cases, existing air interfaces are being discarded, in favour of OFDMA for the downlink and a variety of OFDM based solutions for the uplink, much akin to WiMAX.In some areas of the world the wide availability of UMTS and a general desire for standardization has meant spectrum has not been allocated for WiMAX: in July 2005, the EU-wide frequency allocation for WiMAX was blocked.<a href="http://en.wikipedia.org/wiki/WiMAX#3G_and_4G_cellular_phone_systems" target="_blank">http://en.wikipedia.org/wiki/WiMAX#3G_and_4G_cellular_phone_systems</a><a href="http://en.wikipedia.org/wiki/WiMAX" target="_blank">http://en.wikipedia.org/wiki/WiMAX</a><a href="http://en.wikipedia.org/wiki/4G" target="_blank">http://en.wikipedia.org/wiki/4G</a>SLT/Mobitel gives HSPA<a href="http://en.wikipedia.org/wiki/High-Speed_Packet_Access" target="_blank">http://en.wikipedia.org/wiki/High-Speed_Packet_Access</a>The two existing standards (HSDPA and HSUPA) in the family provide increased performance by using improved modulation schemes and by refining the protocols by which handsets and base stations communicate. These improvements lead to a better utilization of the existing radio bandwidth provided by UMTS.The number of commercial 3.5G networks--also known as High-Speed Downlink Packet Access, or HSDPA, networks--launched worldwide grew by 69 percent in 2007. There are now 174 commercial HSDPA networks in 76 countries. An additional 38 networks are committed to rollouts, which will bump the total to 211 HSDPA networks in 90 countries. Commercial HSDPA networks are widely available in Western Europe (61 networks), Southeast Asia (35), Eastern Europe (34), the Middle East and Africa (20), and the Americas and the Caribbean (16). Almost two-thirds (62 percent) of existing commercial HSDPA networks support downlink speeds of 3.6 Mbit/s or more, while more than a fifth (21 percent) support the peak downlink speed of 7.2 Mbit/s.[1]Many HSPA rollouts can be achieved by a software upgrade to existing 3G networks, giving 3.5G a headstart over WiMax, which requires dedicated network infrastructure. Rising sales of HSPA-enabled mobiles--aided by more-generous-than-expected operator subsidies of the hardware--are helping to drive the 3.5G market.[2]</blockquote>

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