iDEN, which stands for Integrated Digital Enhanced Network, is a wireless telecommunications technology which offers the benefits of a trunked radio and a mobile phone to its subscribers. It was developed by Motorola and released in 1994.
In comparison to analog cellular and two-way radio systems, iDEN is able to place more users in a given spectral space through the use of time-division multiple access (TDMA) and speech compression. The Push-to-Talk feature offered by iDEN is the fastest in the industry.
The iDEN network also has a subset known as Harmony Wireless Communications System, with Small System Release 5.0. This technology is able to support up to the maximum limit of 192 sites. Through Small System Release 6.1, however, the technology is now able to interface with a full iDEN system.
iDEN has been designed and licensed to operate on individual frequencies that may or may not be contiguous. Although it only occupies 20 kHz, it operates on 25 kHz channels in order to provide interference protection through the use of guard bands.
TDMA Cellular (IS-54 and IS-136), on the other hand, occupies 30 kHz channels but occupies 40 kHz, even though it may serve the same number of users as iDEN. Frequency-division duplexing is used to keep transmitted signals and received signals separate by 39 MHz, 45 MHz or 48 MHz depending on what frequency is being used.
Through the use of TDMA, iDEN is able to support either three or six mobile phone users per channel, and six push-to-talk users per channel. TDMA ensures that the transmit and receive time slots allotted to each user are deliberately offset so that a single user will not have to need to transmit and receive at the same time. As a result of the option of time-division duplexing of radio frequency (RF) section usage, duplexers are no longer necessary for mobile phones.
In North America, Sprint Nextel and SouthernLINC Wireless are the two main public iDEN service providers, although there are also several small public and private iDEN service providers. Most major airports contain private iDEN systems.
Included among the countries which feature operating iDEN networks are Canada, China, Argentina, Peru, Mexico, Philippines, Singapore, Brazil, Jordan, Chile, Israel, Saudi Arabia, El Salvador and Japan. Sprint Nextel in North America, Telus in Canada and NII in Mexico and South America all feature full roaming.