IDEN

Integrated Digital Enhanced Network (iDEN) is a mobile telecommunications technology, developed by Motorola, which provides its users the benefits of a trunked radio and a cellular telephone. It was called the first mobile social network by many technology industry analysts. iDEN places more users in a given spectral space, compared to analog cellular and two-way radio systems, by using speech compression and time division multiple access (TDMA).

The iDEN project originally began as MIRS (Motorola Integrated Radio System) in early 1991. The project was a software lab experiment focused on the utilization of discontiguous spectrum for GSM wireless. GSM systems typically require 24 contiguous voice channels, but the original MIRS software platform dynamically selected fragmented channels in the radio frequency (RF) spectrum in such a way that a GSM telecom switch could commence a phone call the same as it would in the contiguous channel scenario. The original MIRS System was renamed IDEN in 1994 by Roger Cameron Wood, a young engineering program manager leading the product development effort who also gave the handsets their distinctive industrial design, group software features, and "chirp" audio.

iDEN is designed and licensed to operate on individual frequencies that may not be contiguous. iDEN operates on 25 kHz channels, but only occupies 20 kHz in order to provide interference protection via guard bands. By comparison, TDMA Cellular (Digital AMPS) is licensed in blocks of 30 kHz channels, but each emission occupies 40 kHz, and is capable of serving the same number of subscribers per channel as iDEN. iDEN uses frequency-division duplexing to transmit and receive signals separately, with transmit and receive bands separated by 39 MHz, 45 MHz, or 48 MHz depending on the frequency band being used.

iDEN supports either three or six interconnect users (phone users) per channel, and six dispatch users (push-to-talk users) per channel, using time division multiple access. The transmit and receive time slots assigned to each user are deliberately offset in time so that a single user never needs to transmit and receive at the same time. This eliminates the need for a duplexer at the mobile end, since time-division duplexing of RF section usage can be performed.

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