3G is a short term for third-generation wireless, and refers to near-future developments in personal and business wireless technology, especially mobile communications.

3G is include features such as:
·Enhanced multimedia (voice, data, video, and remote control)
·Usability on all popular modes (cellular telephone, e-mail, paging, fax, videoconferencing, and Web browsing)
·Broad bandwidth and high speed (upwards of 2 Mbps)
·Routing flexibility (repeater, satellite, LAN)
·Operation at approximately 2 GHz transmit and receive frequencies

3.5G is better than the much touted `3G' or third generation mobile networks where high speed data, voice and video can be exchanged.
The zippy new technology, is known as HSDPA — High Speed Data Downlink Packet Access — industry jargon which means the download speeds at which video or data can be sucked into a mobile phone could theoretically be as high as 10 mega bits per second (MBPS) — but in practice would be around a half to one-third this speed. It is the next evolutionary step in speeding up today's GSM or Global Services Mobile networks after it has upgraded to EDGE — Enhanced Data Rate for GSM and WCDMA — Wide Band Code Division Multiple Access.

some of famous 3.5g mobiles are nokia n95,nokia 6110 classic

What does the acronym UMTS stand for?
Universal Mobile Telephone System.

What is UMTS?
UMTS is one of the Third Generation (3G) mobile systems being developed within the ITU's IMT-2000 framework.