Integrated Digital Enhanced Network

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. 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).

History

The iDEN project originally began as MIRS (Motorola Integrated Radio System)in the 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 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 by Roger Wood, a young product marketing manager leading the branding effort who also gave the handsets their distinctive "chirp" and industrial design.

Operating frequencies

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.^[1]

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.

Hardware

The first commercial iDEN handset was Motorola's L3000, which was released in 1994. Most modern iDEN handsets use SIM cards, similar to, but incompatible with GSM handsets' SIM cards. Early iDEN models such as the i1000plus stored all subscriber information inside the handset itself, requiring the data to be downloaded and transferred should the subscriber want to switch handsets. Newer handsets using SIM technology make upgrading or changing handsets as easy as swapping the SIM card. Four different sized SIM cards exist, "Endeavor" SIMs are used only with the i2000 without data, "Condor" SIMs are used with the two-digit models (i95cl, for example) using a SIM with less memory than the three-digit models (i730, i860), "Falcon" SIMs are used in the three-digit phones, (i530, i710) and will read the smaller SIM for backward compatibility, but some advanced features such as extra contact information is not supported by the older SIM cards. There is also the "Falcon 128" SIM, which is the same as the original "Falcon", but doubled in memory size, which is used on new 3 digit phones (i560, i930).

The interconnect-side of the iDEN network uses GSM signalling for call set-up and mobility management, with the Abis protocol stack modified to support iDEN's additional features. Motorola has named this modified stack 'Mobis'.

Each base site requires precise timing and location information to synchronize data across the network. To obtain and maintain this information each EBTS uses GPS satellites to receive a precise timing reference .

Operators

In the United States of America there are two large public iDEN service providers: Sprint Nextel and SouthernLINC Wireless, and several small public and private iDEN service providers. Numerous private systems exist, including one run by ARINC, covering all major airports. Countries which have operating iDEN networks include Canada, Argentina, Peru, Mexico, Brazil, Jordan, Chile, Israel, Philippines, Singapore, Saudi Arabia, Japan, El Salvador, China and most recently India and Guatemala. Full Roaming is available between Sprint/Nextel in the US, Telus (Canada), and NII (Mexico and S. American markets) Data/Voice/Radio. For markets not controlled by NII Holdings, Inc., the roaming is for voice telephony only.

Motorola is committed to support of iDEN technology despite the Sprint buyout of Nextel and Sprint/Nextel's supposed eventual conversion to Sprint's CDMA system. Nextel has stated they will support iDEN until at least 2010 and Sprint has recently released new iDEN handsets and maintained their iDEN holdings with the purchase of the Sprint CDMA affiliate network, iPCS, for $426 million, which Sprint was repeatedly engaged in lawsuits with over non-compete agreement violations stemming from the 2005 purchase of Nextel and the later purchase of Nextel Partners. Other iDEN carriers have no foreseeable expiration date for their services. The speed of iDEN's push-to-talk (a.k.a dispatch) feature remains the fastest in the industry as compared to Sprint Qchat [Qualcomm PTT over EVDO Rev. A] and Verizon PTT [requiring at least 1XRTT data] in the US.

There is a smaller subset of the iDEN network called "Harmony Wireless Communications System". With Small System Release 7.0, it supports a maximum site count of 160 or 576 individual cells. Harmony has the ability to interface with a full iDEN system, and has the ability to support interconnect, dispatch, and packet data. SSR7.1 is the latest Harmony release.

Countries operating iDEN networks

See also

• Motorola iDEN phone models
• Push to Talk over Cellular
• Radio Service Software
• WiDEN

References

1. ^ Motorola iDEN Technical Overview

External links

• Motorola iDEN phones
• List of iDEN providers globally
• List of Urban ID codes