Introduced in 1994 by Motorola, Integrated Digital Enhanced Network (iDEN) is a wireless network technology designed for vertical market mobile business applications. iDEN operates in the 800-MHz, 900-MHz, and 1.5-GHz bands and is based on Time Division Multiple Access (TDMA) and Global System for Mobile (GSM) architectures.
It uses Motorola’s Vector Sum Excited Linear Predictors (VSELP) voice encoder for compression and quadrature amplitude modulation (QAM) to deliver 64 kbps over a 25-kHz channel. iDEN is promoted as being “four-in-one,” allowing users to take advantage of two-way digital radio, digital wireless phone, alphanumeric messaging, and data, fax, and Internet capabilities with one pocket-sized digital handset.
This eliminates the need to carry around multiple communication devices and the time-consuming task of synchronizing them. The iDEN phones are full-featured business phones that provide features such as call forwarding, call hold, automatic answer, and speakerphone. Using the group call feature, users can communicate with one or hundreds of people with the push of a single button without having to set up a conference call or waste time with costly individual calls.
The data-ready phones also provide fax and e-mail capabilities and access to the Internet. Motorola iDEN phones incorporate a number of valuable messaging services, including voice messaging, text messaging, and alphanumeric paging. This gives the user the ability to receive messages even when the phone is turned off. Some iDEN phones are voice-activated and allow the user to record voice memos for playback later.
The newest phones, such as the i90c, feature J2ME technology, enabling users to download interactive content and applications—from business tools to graphically rich games. Users select “Java Apps” from the phone’s main menu, and the applications execute directly on the handset instead of on a server within the network, as is the case with applications based on the complementary Wireless Application Protocol (WAP).
When a mobile radio places a call on an iDEN system, it goes through a series of system handshakes to establish the call as follows:
- When the mobile radio is powered up, it scans and locks onto a control channel.
- The mobile radio registers on the system.
- When it initiates a call, the mobile radio places a service request on the control channel.
- The fixed end system assigns the mobile radio to the dedicated control channel.
- The mobile radio uses the dedicated control channel to transmit the information required by the fixed end system to complete the call.
- The fixed end system assigns the mobile radio to a traffic channel that is used for communication of voice or data.
Each time the mobile radio initiates or receives a call, it measures the strength of the received signal. Based on this measurement and the power control constant defined on the control channel, it adjusts its transmit power level to a level just high enough to ensure clear reception of its signal by the intended recipients.
In keeping with the industry trend of upgrading wireless networks to third-generation (3G) technologies, Nextel and Motorola are working to double the voice capacity of iDEN and implement data compression on the network. The two most important factors driving carriers to upgrade to 3G technologies are the need to increase voice capacity and deliver packet data service at acceptable speeds.
After considering its various technology and strategic options, Nextel decided to leverage its existing infrastructure by making enhancements to its iDEN network rather than overlay a standards-based technology onto the proprietary Motorola iDEN platform. Nextel also expects to provide a two- to fivefold increase in the end-user experience of most Web-enabled and general office data applications.
While 2.5G technologies like General Packet Radio Service (GPRS) are capable of achieving up to 115 or 144 kbps with extensions to TDMAor CDMA, respectively, Nextel expects to achieve data speeds up to 60 to 70 kbps with the addition of data compression.
iDEN is designed to give the mobile user quick access to information without having to carry around several devices. Currently, iDEN systems work in more than a dozen countries, but only two service providers in the United States use iDEN in their wireless networks: Nextel and Southern Company.