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DECT or Digital Enhanced (formerly European) Cordless Telecommunications is an ETSI standard for digital portable phones, commonly used for domestic or corporate purposes. DECT can also be used for wireless data transfers. DECT is recognised by the ITU as fulfilling the IMT-2000 requirements and thus qualifies as a 3G system. Within the IMT-2000 group of technologies, DECT is referred to as IMT-FT (Frequency Time).

DECT was developed by ETSI but has since been adopted by many countries all over the world. DECT is used in all countries in Europe, outside Europe it is used in most of Asia, Australia and South-America. As of 2005, the American Federal Communications Commission changed channelization and licensing costs in a portion of 1900 MHz range spectrum which allowed DECT devices to be used without expensive changes. DECT will operate as Unlicensed Personal Communications Services (UPCS).

Contents 1 Application 2 Features 3 Technical details 4 DECT for Data Networks 5 See also 6 References 7 External links

Connections with DECT is just for the communication between near located points and is not describing the network which is mostly behind. The connection to the network is realized with a gateway which is often named as base station. In most of the cases the connection is to the public switched telephone network. Also newer technologies like Voice over IP are known in the market. There are also devices available—like baby monitors—that do not need a gateway.

Typical abilities of a domestic DECT Generic access profile (GAP) system include:

• Multiple handsets to one base station and one phone line socket. Additional handsets usually have a battery charger station instead of a base station. The additional handsets do not require additional telephone sockets nor additional transceivers.

• Interference-free wireless operation to around 100 metres outdoors. Operates clearly in common congested domestic radio traffic situations. For instance, generally immune to interference from WiFi or video senders.

• Ability to make internal (intercom) calls between handsets.

Many DECT systems also include additional features such as Caller ID or a shared phonebook, but these are not standardized and may not work across different handset types.

Some DECT properties:

• Audio codec: G.726
• Net bit rate: 32 kbit/s
• Frequency: 1880-1900 MHz in Europe, 1920-1930MHz in the US
• Carriers: 10 (1,728 kHz spacing) in Europe, 5 (1,728 kHz spacing) in the US
• Time slots: 2 x 12 (up and down stream)
• Channel allocation: dynamic
• Average transmission power: 10 mW (250 mW peak) in Europe, 4 mW (100 mW peak) in the US

The DECT physical layer uses:

• Frequency division multiple access (FDMA),
• Time division multiple access (TDMA) and
• Time division duplex (TDD)

This means that the radio spectrum is divided into physical channels in two dimensions: frequency and time.

The maximum allowed power for portable equipment as well as base stations is 250mW. On average, however, a portable device radiates about 10mW during a call as it is only using one of 24 time slots to transmit.

The DECT media access control layer is the layer which controls the physical layer and provides connection oriented, connectionless and broadcast services to the higher layers. It also provides encryption services with the DECT Standard Cipher (DSC). The encryption is fairly weak, using a 35-bit initialization vector and encrypting the voice stream with 64-bit encryption.

The DECT data link layer uses a variant of the ISDN data link protocol called LACP. They are based on HDLC.

The DECT network layer always contains the following protocol entities:

• Call Control (CC)
• Mobility Management (MM)

Optionally it may also contain others:

• Call Independent Supplementary Services (CISS)
• Connection Oriented Message Service (COMS)
• Connectionless Message Service (CLMS)

All these communicate through a Link Control Entity (LCE).

The call control protocol is derived from ISDN DSS1, which is a Q.931 derived protocol. Many DECT-specific changes have been made.

There are four application areas in use in Europe:

• Domestic DECTs are connected to a base (radio fixed parts) connected to the PSTN. A base can accept more DECT handsets.
• Business DECTs connected to PBX. In such cases, there are many radio fixed parts. The DECT handsets dynamically connect to these using a handover feature.
• Public DECT connected to the PSTN (very rare). A high density alternative to GSM.
• Local loop (very rare). In this case, a DECT radio link replaces the normally wired connection between the final PSTN distribution point to the subscriber.

DECT GAP is an interoperability profile for DECT. The intent is that two different products from different manufacturers that both conform not only to the DECT standard, but also to the GAP profile defined within the DECT standard, are able to interoperate for basic calling.

Other interoperability profiles exist in the DECT suite of standards, and in particular the DPRS (DECT Packet Radio Services) bring together a number of prior interoperability profiles for the use of DECT as a wireless LAN and wireless internet access service. With good range (up to 200m indoors and 6km using directional antennae outdoors), dedicated spectrum, high interference immunity, open interoperability and data speeds of around 500kb/s, DECT appeared at one time to be a superior alternative to WiFi. The protocol capabilities built into the DECT networking protocol standards were particularly good at supporting fast roaming in the public space, between hotspots operated by competing but connected providers. The first DECT product to reach the market, Olivetti's Net³, was a wireless LAN, and German firms Dosch & Amand and Hoeft & Wessel built niche businesses on the supply of data transmission systems based on DECT.

However the timing of the availability of DECT - in the mid 1990's - was too early to find wide application for wireless data outside niche industrial applications. Whilst contemporary providers of WiFi struggled with the same issues, providers of DECT retreated to the more immediately lucrative market for cordless telephones. A key weakness was also the inaccessibility of the US market, due to FCC spectrum restrictions. By the time mass applications for wireless internet had emerged, and the US had opened up to DECT, well into the new century, the industry had moved far ahead in terms of performance and DECT's time as a wireless data transport was past.

• Generic access profile (GAP)
• GSM Interworking Profile (GIP)
• CorDECT
• Unlicensed Personal Communications Services
• Wireless local loop
• Microcell
• CT2 (DECT's predecessor)
• WDECT
• Net³

• Book: Cordless Telecommunications Worldwide, pub Springer 1996, ed WHW Tuttlebee
• Book: Personal Wireless Communication with DECT and PWT, pub Artech 1998, J Philips & G MacNamee
• Rechnernetze - The DECT Standard. (a summary of the DECT standard)

• DECT Forum at dect.org
• DECT information at ETSI
• DECTWeb
• DECT reaches a New Generation
• DECT technical info from GN Netcom