1 2 Page 2
Page 2 of 2

The International Telecommunication Union (ITU), a specialized agency of the United Nations, has attempted to coordinate these competing technologies to improve throughput and increase interoperability. The International Mobile Telecommunications 2000 standard is a third-generation digital communications specification from the ITU. And the European (i.e., GSM-based) implementation of IMT-2000 is UMTS, which is based on WCDMA. Previous cellular telephone data systems were mostly circuit-switched, requiring a dedicated connection. WCDMA is packet-switched, using the Internet Protocol. The first commercial WCDMA network was launched in Japan in 2001.

Technical Details

UMTS has been specified as an integrated application for mobile voice and data systems with wide-area coverage. Using globally harmonized spectrum in paired and unpaired bands, early implementations of UMTS offer theoretical bit rates of up to 384Kbit/sec. in situations where the mobile device is actually moving. The current goal is to achieve 2Mbit/sec. when both ends of the connection are (at least temporarily) stationary.

UMTS operates on radio frequencies identified by the ITU IMT-2000 specification document and licensed to operators, using a 5-MHz-wide channel that simplifies deployment for network providers that have been granted large, contiguous blocks of spectrum. Most UMTS systems use frequencies between 1,885 and 2,025 MHz.

UMTS assigns separate carrier frequencies to incoming and outbound signals, a process called frequency division duplexing (FDD). For symmetric traffic, such as two-way videophones, FDD is highly efficient, allowing uplink and download data rates to be equal, in contrast to technologies such as Asymmetric Digital Subscriber Line service, which typically offers upload rates that are much slower than its download rates. FDD reduces interference and wastes no bandwidth in switching from transmitting to receiving.

Ongoing work within the 3rd Generation Partnership Project promises increased throughput speeds over the WCDMA Radio Access Network. High-Speed Downlink Packet Access and High-Speed Uplink Packet Access technologies are already standardized, and commercial operators in Asia and North America are putting them through network trials. With theoretical download speeds as high as 14.4Mbit/sec. and uplink speeds of up to 5.8Mbit/sec., these technologies will make it possible for UMTS to offer data transmission speeds comparable to those of hard-wired Ethernet-based networks.

Kay is a Computerworld contributing writer in Worcester, Mass. You can contact him at

See additional Computerworld QuickStudies

Copyright © 2006 IDG Communications, Inc.

1 2 Page 2
Page 2 of 2
Bing’s AI chatbot came to work for me. I had to fire it.
Shop Tech Products at Amazon