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Digital enhanced cordless telecommunications (Digital European cordless telecommunications), usually known by the
acronym An acronym is a word or name formed from the initial components of a longer name or phrase. Acronyms are usually formed from the initial letters of words, as in '' NATO'' (''North Atlantic Treaty Organization''), but sometimes use syllables, a ...
DECT, is a standard primarily used for creating
cordless telephone A cordless telephone or portable telephone has a portable telephone handset that connects by radio to a base station connected to the public telephone network. The operational range is limited, usually to the same building or within some shor ...
systems. It originated in
Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a subcontinent of Eurasia and it is located enti ...
, where it is the common standard, replacing earlier cordless phone standards, such as 900  MHz
CT1 CT1 stands for ''Cordless telephone generation 1'' and is an analog cordless telephone standard that was standardized by the European Conference of Postal and Telecommunications Administrations (CEPT) in 1984 and deployed in eleven European coun ...
and
CT2 CT2 is a cordless telephony standard that was used in the early 1990s to provide short-range proto-mobile phone service in some countries in Europe. It is considered the precursor to the more successful DECT system. CT2 was also referred to by its ...
. Beyond Europe, it has been adopted by Australia and most countries in
Asia Asia (, ) is one of the world's most notable geographical regions, which is either considered a continent in its own right or a subcontinent of Eurasia, which shares the continental landmass of Afro-Eurasia with Africa. Asia covers an ...
and
South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the souther ...
. North American adoption was delayed by
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., federal district, five ma ...
radio-frequency regulations. This forced development of a variation of DECT called DECT 6.0, using a slightly different frequency range, which makes these units incompatible with systems intended for use in other areas, even from the same manufacturer. DECT has almost completely replaced other standards in most countries where it is used, with the exception of North America. DECT was originally intended for fast roaming between networked base stations, and the first DECT product was Net3 wireless LAN. However, its most popular application is single-cell cordless phones connected to traditional analog telephone, primarily in home and small-office systems, though gateways with multi-cell DECT and/or DECT repeaters are also available in many
private branch exchange A business telephone system is a multiline telephone system typically used in business environments, encompassing systems ranging in technology from the key telephone system (KTS) to the private branch exchange (PBX). A business telephone syst ...
(PBX) systems for medium and large businesses, produced by
Panasonic formerly between 1935 and 2008 and the first incarnation of between 2008 and 2022, is a major Japanese multinational conglomerate corporation, headquartered in Kadoma, Osaka. It was founded by Kōnosuke Matsushita in 1918 as a lightbulb ...
,
Mitel Mitel Networks Corporation is a Canadian telecommunications company. The company previously produced TDM PBX systems and applications, but after a change in ownership in 2001, now focuses almost entirely on Voice-over-IP (VoIP) products. Mitel ...
, Gigaset,
Cisco Cisco Systems, Inc., commonly known as Cisco, is an American-based multinational corporation, multinational digital communications technology conglomerate (company), conglomerate corporation headquartered in San Jose, California. Cisco develo ...
,
Grandstream Founded in 2002, Grandstream Networks is a manufacturer of IP voice and video communications equipment, video surveillance, gateways and analog telephone adapters (ATAs), and Asterisk-based IP-PBX appliances. Grandstream supplies small and medi ...
, Snom, Spectralink, and RTX Telecom. DECT can also be used for purposes other than cordless phones, such as baby monitors and industrial sensors. The ULE Alliance's DECT ULE and its "HAN FUN" protocol are variants tailored for home security, automation, and the
internet of things The Internet of things (IoT) describes physical objects (or groups of such objects) with sensors, processing ability, software and other technologies that connect and exchange data with other devices and systems over the Internet or other com ...
(IoT). The DECT standard includes the generic access profile (GAP), a common interoperability profile for simple telephone capabilities, which most manufacturers implement. GAP-conformance enables DECT handsets and bases from different manufacturers to interoperate at the most basic level of functionality, that of making and receiving calls. Japan uses its own DECT variant, J-DECT, which is supported by the DECT forum. The New Generation DECT (NG-DECT) standard, marketed as
CAT-iq Cordless Advanced Technology—internet and quality (CAT-iq) is a technology initiative from the Digital Enhanced Cordless Telecommunications (DECT) Forum, based on ETSI TS 102 527 New Generation DECT (NG-DECT) European standard series. NG-DECT ...
by the DECT Forum, provides a common set of advanced capabilities for handsets and base stations. CAT-iq allows interchangeability across IP-DECT base stations and handsets from different manufacturers, while maintaining backward compatibility with GAP equipment. It also requires mandatory support for
wideband audio Wideband audio, also known as wideband voice or HD voice, is high definition voice quality for telephony audio, contrasted with standard digital telephony "toll quality". It extends the frequency range of audio signals transmitted over telephone ...
. DECT-2020 New Radio, marketed as NR+ (New Radio plus), is a 5G data transmission protocol which meets ITU-R IMT-2020 requirements for ultra-reliable low-latency and massive machine-type communications, and can co-exist with earlier DECT devices.ETSI TR 103 810 V1.1.1 (2021-11). Final Evaluation Report on DECT-2020 NR.
ETSI, 23 November 2021.


Standards history

The DECT standard was developed by
ETSI The European Telecommunications Standards Institute (ETSI) is an independent, not-for-profit, standardization organization in the field of information and communications. ETSI supports the development and testing of global technical standard ...
in several phases, the first of which took place between 1988 and 1992 when the first round of standards were published. These were the ETS 300-175 series in nine parts defining the air interface, and ETS 300-176 defining how the units should be type approved. A technical report, ETR-178, was also published to explain the standard. Subsequent standards were developed and published by ETSI to cover interoperability profiles and standards for testing. Named Digital European Cordless Telephone at its launch by CEPT in November 1987; its name was soon changed to Digital European Cordless Telecommunications, following a suggestion by Enrico Tosato of Italy, to reflect its broader range of application including data services. In 1995, due to its more global usage, the name was changed from European to Enhanced. DECT is recognized by the ITU as fulfilling the
IMT-2000 IMT-2000 (International Mobile Telecommunications-2000) is the global standard for third generation ( 3G) wireless communications as defined by the International Telecommunication Union. In 1999 ITU approved five radio interfaces for IMT-2000 as a ...
requirements and thus qualifies as a 3G system. Within the IMT-2000 group of technologies, DECT is referred to as IMT-2000 Frequency Time (IMT-FT). DECT was developed by ETSI but has since been adopted by many countries all over the World. The original DECT frequency band (1880–1900 MHz) is used in all countries in
Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a subcontinent of Eurasia and it is located enti ...
. Outside Europe, it is used in most of
Asia Asia (, ) is one of the world's most notable geographical regions, which is either considered a continent in its own right or a subcontinent of Eurasia, which shares the continental landmass of Afro-Eurasia with Africa. Asia covers an ...
, Australia and
South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the souther ...
. In the
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., federal district, five ma ...
, the
Federal Communications Commission The Federal Communications Commission (FCC) is an independent agency of the United States federal government that regulates communications by radio, television, wire, satellite, and cable across the United States. The FCC maintains jurisd ...
in 2005 changed channelization and licensing costs in a nearby band (1920–1930 MHz, or 1.9  GHz), known as Unlicensed Personal Communications Services (UPCS), allowing DECT devices to be sold in the U.S. with only minimal changes. These channels are reserved exclusively for voice communication applications and therefore are less likely to experience interference from other wireless devices such as baby monitors and
wireless network A wireless network is a computer network that uses wireless data connections between network nodes. Wireless networking is a method by which homes, telecommunications networks and business installations avoid the costly process of introducing c ...
s. The New Generation DECT ( NG-DECT) standard was first published in 2007; it was developed by ETSI with guidance from the
Home Gateway Initiative The Home Gateway Initiative (HGI) was a nonprofit trade organization to discuss the key specifications and standards of residential gateways, also known as home gateways. It was founded by telephone companies (Belgacom, BT, Deutsche Telekom, Fran ...
through the DECT Forum to support IP-DECT functions in home gateway/ IP-PBX equipment. The ETSI TS 102 527 series comes in five parts and covers wideband audio and mandatory interoperability features between handsets and base stations. They were preceded by an explanatory technical report, ETSI TR 102 570. The DECT Forum maintains the
CAT-iq Cordless Advanced Technology—internet and quality (CAT-iq) is a technology initiative from the Digital Enhanced Cordless Telecommunications (DECT) Forum, based on ETSI TS 102 527 New Generation DECT (NG-DECT) European standard series. NG-DECT ...
trademark and certification program; CAT-iq wideband voice profile 1.0 and interoperability profiles 2.0/2.1 are based on the relevant parts of ETSI TS 102 527. The DECT Ultra Low Energy (DECT ULE) standard was announced in January 2011 and the first commercial products were launched later that year by Dialog Semiconductor. The standard was created to enable
home automation Home automation or domotics is building automation for a home, called a smart home or smart house. A home automation system will monitor and/or control home attributes such as lighting, climate, entertainment systems, and appliances. It ...
, security, healthcare and energy monitoring applications that are battery powered. Like DECT, DECT ULE standard uses the 1.9 GHz band, and so suffers less interference than
Zigbee Zigbee is an IEEE 802.15.4-based specification for a suite of high-level communication protocols used to create personal area networks with small, low-power digital radios, such as for home automation, medical device data collection, and ...
,
Bluetooth Bluetooth is a short-range wireless technology standard that is used for exchanging data between fixed and mobile devices over short distances and building personal area networks (PANs). In the most widely used mode, transmission power is limit ...
, or
Wi-Fi Wi-Fi () is a family of wireless network protocols, based on the IEEE 802.11 family of standards, which are commonly used for local area networking of devices and Internet access, allowing nearby digital devices to exchange data by radio w ...
from microwave ovens, which all operate in the unlicensed 2.4 GHz
ISM band The ISM radio bands are portions of the radio spectrum reserved internationally for industrial, scientific and medical (ISM) purposes, excluding applications in telecommunications. Examples of applications for the use of radio frequency (RF) en ...
. DECT ULE uses a simple star network topology, so many devices in the home are connected to a single control unit. A new low-complexity audio codec, LC3plus, has been added as an option to the 2019 revision of the DECT standard. This codec is designed for high-quality voice and music applications, and supports scalable narrowband, wideband, super wideband, and fullband coding, with sample rates of 8, 16, 24, 32 and 48 kHz and audio bandwidth of up to 20 kHz. DECT-2020 New Radio protocol was published in July 2020; it defines a new physical interface based on
cyclic prefix In telecommunications, the term cyclic prefix refers to the prefixing of a symbol, with a repetition of the end. The receiver is typically configured to discard the cyclic prefix samples, but the cyclic prefix serves two purposes: * It provides a ...
orthogonal frequency-division multiplexing (CP-
OFDM In telecommunications, orthogonal frequency-division multiplexing (OFDM) is a type of digital transmission and a method of encoding digital data on multiple carrier frequencies. OFDM has developed into a popular scheme for wideband digital comm ...
) capable of up to 1.2Gbit/s transfer rate with QAM-1024 modulation. The updated standard supports multi-antenna
MIMO In radio, multiple-input and multiple-output, or MIMO (), is a method for multiplying the capacity of a radio link using multiple transmission and receiving antennas to exploit multipath propagation. MIMO has become an essential element of w ...
and
beamforming Beamforming or spatial filtering is a signal processing technique used in sensor arrays for directional signal transmission or reception. This is achieved by combining elements in an antenna array in such a way that signals at particular angles ...
, FEC channel coding, and hybrid
automatic repeat request Automatic repeat request (ARQ), also known as automatic repeat query, is an error-control method for data transmission that uses acknowledgements (messages sent by the receiver indicating that it has correctly received a packet) and timeout ...
. There are 17 radio channel frequencies in the range from 450MHz up to 5,875MHz, and channel bandwidths of 1,728, 3,456, or 6,912kHz. Direct communication between end devices is possible with a
mesh network A mesh network is a local area network topology in which the infrastructure nodes (i.e. bridges, switches, and other infrastructure devices) connect directly, dynamically and non-hierarchically to as many other nodes as possible and cooperate wit ...
topology. In October 2021, DECT-2020 NR was approved for the IMT-2020 standard,World’s first non-cellular 5G technology, ETSI DECT-2020, gets ITU-R approval, setting example of new era connectivity
ETSI, 19 October 2021
for use in Massive Machine Type Communications (MMTC) industry automation, Ultra-Reliable Low-Latency Communications (URLLC), and professional
wireless audio Wireless communication (or just wireless, when the context allows) is the transfer of information between two or more points without the use of an electrical conductor, optical fiber or other continuous guided medium for the transfer. The most ...
applications with point-to-point or
multicast In computer networking, multicast is group communication where data transmission is addressed to a group of destination computers simultaneously. Multicast can be one-to-many or many-to-many distribution. Multicast should not be confused wit ...
communications; the proposal was fast-tracked by ITU-R following real-world evaluations. The new protocol will be marketed as NR+ (New Radio plus) by the DECT Forum.
OFDMA Orthogonal frequency-division multiple access (OFDMA) is a multi-user version of the popular orthogonal frequency-division multiplexing (OFDM) digital modulation scheme. Multiple access is achieved in OFDMA by assigning subsets of subcarrier ...
and SC-FDMA modulations were also considered by the ESTI DECT committee. OpenD is an open-source framework designed to provide a complete software implementation of DECT ULE protocols on reference hardware from Dialog Semiconductor and
DSP Group DSP Group, Inc. was an American company that manufactured chipsets for VoIP, multimedia, and digital cordless applications. Founded in 1987 with headquarters in San Jose, California, DSP Group employed over 400 people at three US sites and offices ...
; the project is maintained by the DECT forum.


Application

The DECT standard originally envisaged three major areas of application: * Domestic cordless telephony, using a single base station to connect one or more handsets to the public telecommunications network. * Enterprise premises cordless PABXs and wireless LANs, using many base stations for coverage. Calls continue as users move between different coverage cells, through a mechanism called handover. Calls can be both within the system and to the public telecommunications network. * Public access, using large numbers of base stations to provide high capacity building or urban area coverage as part of a public telecommunications network. Of these, the domestic application (cordless home telephones) has been extremely successful. The enterprise
PABX A business telephone system is a multiline telephone system typically used in business environments, encompassing systems ranging in technology from the key telephone system (KTS) to the private branch exchange (PBX). A business telephone syst ...
market had some success, and all the major PABX vendors have offered DECT access options. The public access application did not succeed, since public cellular networks rapidly out-competed DECT by coupling their ubiquitous coverage with large increases in capacity and continuously falling costs. There has been only one major installation of DECT for public access: in early 1998
Telecom Italia Gruppo TIM, legally TIM S.p.A. (formerly Telecom Italia S.p.A.), also known as the TIM Group in English, is an Italian telecommunications company with headquarters in Rome, Milan, and Naples, (with the Telecom Italia Tower) which provides fix ...
launched a wide-area DECT network known as "Fido" after much regulatory delay, covering major cities in Italy. The service was promoted for only a few months and, having peaked at 142,000 subscribers, was shut down in 2001. DECT has been used for wireless local loop as a substitute for copper pairs in the "last mile" in countries such as India and South Africa. By using directional antennas and sacrificing some traffic capacity, cell coverage could extend to over . One example is the corDECT standard. The first data application for DECT was Net3 wireless LAN system by Olivetti, launched in 1993 and discontinued in 1995. A precursor to Wi-Fi, Net3 was a micro-cellular data-only network with fast roaming between base stations and 520 kbit/s transmission rates. Data applications such as electronic cash terminals, traffic lights, and remote door openers also exist, but have been eclipsed by
Wi-Fi Wi-Fi () is a family of wireless network protocols, based on the IEEE 802.11 family of standards, which are commonly used for local area networking of devices and Internet access, allowing nearby digital devices to exchange data by radio w ...
, 3G and 4G which compete with DECT for both voice and data.


DECT 6.0

DECT 6.0 is a North American marketing term for DECT devices manufactured for the United States and Canada operating at 1.9 GHz. The "6.0" does not equate to a spectrum band; it was decided the term DECT 1.9 might have confused customers who equate larger numbers (such as the 2.4 and 5.8 in existing 2.4 GHz and 5.8 GHz cordless telephones) with later products. The term was coined by Rick Krupka, marketing director at Siemens and the DECT USA Working Group / Siemens ICM. In North America, DECT suffers from deficiencies in comparison to DECT elsewhere, since the
UPCS band Unlicensed Personal Communications Services or UPCS band is the 1920–1930 MHz frequency band allocated by the United States Federal Communications Commission (FCC) for short range Personal Communications Services (PCS) applications in the United ...
(1920–1930 MHz) is not free from heavy interference. Bandwidth is half as wide as that used in Europe (1880–1900 MHz), the 4 mW average transmission power reduces range compared to the 10 mW permitted in Europe, and the commonplace lack of GAP compatibility among US vendors binds customers to a single vendor. Before 1.9 GHz band was approved by the FCC in 2005, DECT could only operate in unlicensed 2.4 GHz and 900 MHz Region 2
ISM band The ISM radio bands are portions of the radio spectrum reserved internationally for industrial, scientific and medical (ISM) purposes, excluding applications in telecommunications. Examples of applications for the use of radio frequency (RF) en ...
s; some users of Uniden WDECT 2.4 GHz phones reported interoperability issues with
Wi-Fi Wi-Fi () is a family of wireless network protocols, based on the IEEE 802.11 family of standards, which are commonly used for local area networking of devices and Internet access, allowing nearby digital devices to exchange data by radio w ...
equipment. North-American products may not be used in Europe, Pakistan, Sri Lanka, and Africa, as they cause and suffer from interference with the local cellular networks. Use of such products is prohibited by European Telecommunications Authorities, PTA, Telecommunications Regulatory Commission of Sri Lanka and the Independent Communication Authority of South Africa. European DECT products may not be used in the United States and Canada, as they likewise cause and suffer from interference with American and Canadian cellular networks, and use is prohibited by the
Federal Communications Commission The Federal Communications Commission (FCC) is an independent agency of the United States federal government that regulates communications by radio, television, wire, satellite, and cable across the United States. The FCC maintains jurisd ...
and
Industry Canada Innovation, Science and Economic Development Canada (ISED; french: Innovation, Sciences et Développement économique Canada; french: ISDE, label=none)''Innovation, Science and Economic Development Canada'' is the applied title under the Federal ...
. DECT 8.0 HD is a marketing designation for North American DECT devices certified with CAT-iq 2.0 "Multi Line" profile.


NG-DECT/CAT-iq

Cordless Advanced Technology—internet and quality (CAT-iq) is a certification program maintained by the DECT Forum. It is based on New Generation DECT (NG-DECT) series of standards from ETSI. NG-DECT/CAT-iq contains features that expand the generic GAP profile with mandatory support for high quality wideband voice, enhanced security, calling party identification, multiple lines, parallel calls, and similar functions to facilitate
VoIP Voice over Internet Protocol (VoIP), also called IP telephony, is a method and group of technologies for the delivery of voice communications and multimedia sessions over Internet Protocol (IP) networks, such as the Internet. The terms Interne ...
calls through SIP and H.323 protocols. There are several CAT-iq profiles which define supported voice features: * CAT-iq 1.0 "HD Voice" (ETSI TS 102 527-1): wideband audio, calling party line and name identification (CLIP/CNAP) * CAT-iq 2.0 "Multi Line" (ETSI TS 102 527-3): multiple lines, line name, call waiting, call transfer, phonebook, call list, DTMF tones, headset, settings * CAT-iq 2.1 "Green" (ETSI TS 102 527-5): 3-party conference, call intrusion, caller blocking (CLIR), answering machine control, SMS, power-management * CAT-iq Data light data services, software upgrade over the air (SUOTA) (ETSI TS 102 527-4) * CAT-iq IOT Smart Home connectivity (IOT) with DECT Ultra Low Energy (ETSI TS 102 939) CAT-iq allows any DECT handset to communicate with a DECT base from a different vendor, providing full interoperability. CAT-iq 2.0/2.1 feature set is designed to support IP-DECT base stations found in office IP-PBX and home gateways.


Technical features

The DECT standard specifies a means for a
portable phone A cordless telephone or portable telephone has a portable telephone handset that connects by radio to a base station connected to the public telephone network. The operational range is limited, usually to the same building or within some short ...
or "Portable Part" to access a fixed telephone network via radio.
Base station Base station (or base radio station) is – according to the International Telecommunication Union's (ITU) Radio Regulations (RR) – a " land station in the land mobile service." The term is used in the context of mobile telephony, wireless c ...
or "Fixed Part" is used to terminate the radio link and provide access to a fixed line. A gateway is then used to connect calls to the fixed network, such as
public switched telephone network The public switched telephone network (PSTN) provides infrastructure and services for public telecommunication. The PSTN is the aggregate of the world's circuit-switched telephone networks that are operated by national, regional, or local telep ...
(telephone jack), office PBX, ISDN, or VoIP over Ethernet connection. Typical abilities of a domestic DECT Generic Access Profile (GAP) system include multiple handsets to one base station and one phone line socket. This allows several cordless telephones to be placed around the house, all operating from the same telephone jack. Additional handsets have a battery charger station that does not plug into the telephone system. Handsets can in many cases be used as
intercom An intercom, also called an intercommunication device, intercommunicator, or interphone, is a stand-alone voice communications system for use within a building or small collection of buildings which functions independently of the public telepho ...
s, communicating between each other, and sometimes as
walkie-talkie A walkie-talkie, more formally known as a handheld transceiver (HT), is a hand-held, portable, two-way radio transceiver. Its development during the Second World War has been variously credited to Donald Hings, radio engineer Alfred J. Gros ...
s, intercommunicating without telephone line connection. DECT operates in the 1880–1900 MHz band and defines ten frequency channels from 1881.792 MHz to 1897.344 MHz with a band gap of 1728 kHz. DECT operates as a multicarrier
frequency-division multiple access Frequency-division multiple access (FDMA) is a channel access method used in some multiple-access protocols. FDMA allows multiple users to send data through a single communication channel, such as a coaxial cable or microwave beam, by dividi ...
(FDMA) and
time-division multiple access Time-division multiple access (TDMA) is a channel access method for shared-medium networks. It allows several users to share the same frequency channel by dividing the signal into different time slots. The users transmit in rapid succession, ...
(TDMA) system. This means that the
radio spectrum The radio spectrum is the part of the electromagnetic spectrum with frequencies from 0  Hz to 3,000  GHz (3  THz). Electromagnetic waves in this frequency range, called radio waves, are widely used in modern technology, particul ...
is divided into physical carriers in two dimensions: frequency and time. FDMA access provides up to 10 frequency channels, and TDMA access provides 24 time slots per every frame of 10ms. DECT uses
time-division duplex A duplex communication system is a point-to-point system composed of two or more connected parties or devices that can communicate with one another in both directions. Duplex systems are employed in many communications networks, either to allow ...
(TDD), which means that down- and uplink use the same frequency but different time slots. Thus a base station provides 12 duplex speech channels in each frame, with each time slot occupying any available channel thus 10 × 12 = 120 carriers are available, each carrying 32 kbit/s. DECT also provides
frequency-hopping spread spectrum Frequency-hopping spread spectrum (FHSS) is a method of transmitting radio signals by rapidly changing the carrier frequency among many distinct frequencies occupying a large spectral band. The changes are controlled by a code known to both tr ...
over TDMA/TDD structure for ISM band applications. If frequency-hopping is avoided, each base station can provide up to 120 channels in the DECT spectrum before frequency reuse. Each timeslot can be assigned to a different channel in order to exploit advantages of frequency hopping and to avoid interference from other users in asynchronous fashion. DECT allows interference-free wireless operation to around outdoors. Indoor performance is reduced when interior spaces are constrained by walls. DECT performs with fidelity in common congested domestic radio traffic situations. It is generally immune to interference from other DECT systems,
Wi-Fi Wi-Fi () is a family of wireless network protocols, based on the IEEE 802.11 family of standards, which are commonly used for local area networking of devices and Internet access, allowing nearby digital devices to exchange data by radio w ...
networks, video senders,
Bluetooth Bluetooth is a short-range wireless technology standard that is used for exchanging data between fixed and mobile devices over short distances and building personal area networks (PANs). In the most widely used mode, transmission power is limit ...
technology, baby monitors and other wireless devices.


Technical properties

ETSI standards documentation ETSI EN 300 175 parts 1–8 (DECT), ETSI EN 300 444 (GAP) and ETSI TS 102 527 parts 1–5 (NG-DECT) prescribe the following technical properties: * Audio codec: ** mandatory: *** 32kbit/s G.726 ADPCM (narrow band), *** 64kbit/s G.722 sub-band ADPCM (wideband) ** optional: *** 64kbit/s G.711 μ-law/A-law PCM (narrow band), *** 32kbit/s G.729.1 (wideband), *** 32kbit/s MPEG-4 ER AAC-LD (wideband), *** 64kbit/s MPEG-4 ER AAC-LD (super-wideband) * Frequency: the DECT physical layer specifies RF carriers for the frequency ranges 1880 MHz to 1980 MHz and 2010 MHz to 2025 MHz, as well as 902 MHz to 928 MHz and 2400 MHz to 2483,5 MHz
ISM band The ISM radio bands are portions of the radio spectrum reserved internationally for industrial, scientific and medical (ISM) purposes, excluding applications in telecommunications. Examples of applications for the use of radio frequency (RF) en ...
with frequency-hopping for the U.S. market. The most common spectrum allocation is 1880 MHz to 1900 MHz; outside Europe, 1900 MHz to 1920 MHz and 1910 MHz to 1930 MHz spectrum is available in several countries. ** in Europe, as well as South Africa, Asia, Hong Kong, Australia, and New Zealand ** in Korea ** in Taiwan ** (J-DECT) in Japan ** in China (until 2003) ** in Brazil ** in Latin America ** (DECT 6.0) in the United States and Canada * Carriers (1.728 MHz spacing): ** 10 channels in Europe and Latin America ** 8 channels in Taiwan ** 5 channels in the US, Brazil, Japan ** 3 channels in Korea * Time slots: 2 × 12 (up and down stream) * Channel allocation: dynamic * Average transmission power: 10 mW (250 mW peak) in Europe & Japan, 4 mW (100 mW peak) in the US


Physical layer

The DECT
physical layer In the seven-layer OSI model of computer networking, the physical layer or layer 1 is the first and lowest layer; The layer most closely associated with the physical connection between devices. This layer may be implemented by a PHY chip. Th ...
uses FDMA/TDMA access with TDD. Gaussian frequency-shift keying (GFSK) modulation is used: the binary one is coded with a frequency increase by 288 kHz, and the binary zero with frequency decrease of 288 kHz. With high quality connections, 2-, 4- or 8-level differential PSK modulation (DBPSK, DQPSK or D8PSK), which is similar to QAM-2, QAM-4 and QAM-8, can be used to transmit 1, 2, or 3 bits per each symbol. QAM-16 and QAM-64 modulations with 4 and 8 bits per symbol can be used for user data (B-field) only, with resulting transmission speeds of up to 5,068Mbit/s. DECT provides dynamic channel selection and assignment; the choice of transmission frequency and time slot is always made by the mobile terminal. In case of interference in the selected frequency channel, the mobile terminal (possibly from suggestion by the base station) can initiate either intracell handover, selecting another channel/transmitter on the same base, or intercell handover, selecting a different base station altogether. For this purpose, DECT devices scan all idle channels at regular 30s intervals to generate a received signal strength indication (RSSI) list. When a new channel is required, the mobile terminal (PP) or base station (FP) selects a channel with the minimum interference from the RSSI list. The maximum allowed power for portable equipment as well as base stations is 250 mW. A portable device radiates an average of about 10 mW during a call as it is only using one of 24 time slots to transmit. In Europe, the power limit was expressed as
effective radiated power Effective radiated power (ERP), synonymous with equivalent radiated power, is an IEEE standardized definition of directional radio frequency (RF) power, such as that emitted by a radio transmitter. It is the total power in watts that would ...
(ERP), rather than the more commonly used equivalent isotropically radiated power (EIRP), permitting the use of high-gain directional antennas to produce much higher EIRP and hence long ranges.


Data link layer

The DECT
media access control In IEEE 802 LAN/MAN standards, the medium access control (MAC, also called media access control) sublayer is the layer that controls the hardware responsible for interaction with the wired, optical or wireless transmission medium. The MAC subla ...
layer controls the physical layer and provides connection oriented, connectionless and
broadcast Broadcasting is the distribution (business), distribution of sound, audio or video content to a dispersed audience via any electronic medium (communication), mass communications medium, but typically one using the electromagnetic spectrum (radio ...
services to the higher layers. The DECT
data link layer The data link layer, or layer 2, is the second layer of the seven-layer OSI model of computer networking. This layer is the protocol layer that transfers data between nodes on a network segment across the physical layer. The data link layer ...
uses Link Access Protocol Control (LAPC), a specially designed variant of the
ISDN Integrated Services Digital Network (ISDN) is a set of communication standards for simultaneous digital transmission of voice, video, data, and other network services over the digitalised circuits of the public switched telephone network. Wor ...
data link protocol called LAPD. They are based on
HDLC High-Level Data Link Control (HDLC) is a bit-oriented code-transparent synchronous data link layer protocol developed by the International Organization for Standardization (ISO). The standard for HDLC is ISO/IEC 13239:2002. HDLC provides both ...
. GFSK modulation uses a bit rate of 1152 kbit/s, with a frame of 10ms (11520bits) which contains 24 time slots. Each slots contains 480 bits, some of which are reserved for physical packets and the rest is guard space. Slots 0–11 are always used for downlink (FP to PP) and slots 12–23 are used for uplink (PP to FP). There are several combinations of slots and corresponding types of physical packets with GFSK modulation: * Basic packet (P32) 420 or 424 bits "full slot", used for normal speech transmission. User data (B-field) contains 320 bits. * Low-capacity packet (P00) 96 bits at the beginning of the time slot ("short slot"). This packet only contains 64-bit header (A-field) used as a dummy bearer to broadcast base station identification when idle. * Variable capacity packet (P00''j'') 100 + ''j'' or 104 + ''j'' bits, either two half-slots (0 ≤ ''j'' ≤ 136) or "long slot" (137 ≤ ''j'' ≤ 856). User data (B-field) contains ''j'' bits. ** P64 (''j'' = 640), P67 (''j'' = 672) "long slot", used by NG-DECT/CAT-iq wideband voice and data. * High-capacity packet (P80) 900 or 904 bits, "double slot". This packet uses two time slots and always begins in an even time slot. The B-field is increased to 800 bits.. The 420/424 bits of a GFSK basic packet (P32) contain the following fields: * 32 bits synchronization code (S-field): constant bit string AAAAE98AH for FP transmission, 55551675H for PP transmission * 388 bits data (D-field), including ** 64 bits header (A-field): control traffic in logical channels C, M, N, P, and Q ** 320 bits user data (B-field): DECT payload, i.e. voice data ** 4 bits error-checking (X-field): CRC of the B-field * 4 bits collision detection/channel quality (Z-field): optional, contains a copy of the X-field The resulting full data rate is 32 kbit/s, available in both directions.


Network layer

The DECT
network layer In the seven-layer OSI model of computer networking, the network layer is layer 3. The network layer is responsible for packet forwarding including routing through intermediate routers. Functions The network layer provides the means of trans ...
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 Integrated Services Digital Network (ISDN) is a set of communication standards for simultaneous digital transmission of voice, video, data, and other network services over the digitalised circuits of the public switched telephone network. Wor ...
DSS1, which is a Q.931-derived protocol. Many DECT-specific changes have been made. The mobility management protocol includes the management of identities, authentication, location updating, on-air subscription and key allocation. It includes many elements similar to the GSM protocol, but also includes elements unique to DECT. Unlike the GSM protocol, the DECT network specifications do not define cross-linkages between the operation of the entities (for example, Mobility Management and Call Control). The architecture presumes that such linkages will be designed into the interworking unit that connects the DECT access network to whatever mobility-enabled fixed network is involved. By keeping the entities separate, the handset is capable of responding to any combination of entity traffic, and this creates great flexibility in fixed network design without breaking full interoperability. 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. The DECT standard includes full testing suites for GAP, and GAP products on the market from different manufacturers are in practice interoperable for the basic functions.


Security

The DECT media access control layer includes authentication of handsets to the base station using the DECT Standard Authentication Algorithm (DSAA). When registering the handset on the base, both record a shared 128-bit Unique Authentication Key (UAK). The base can request authentication by sending two random numbers to the handset, which calculates the response using the shared 128-bit key. The handset can also request authentication by sending a 64-bit random number to the base, which chooses a second random number, calculates the response using the shared key, and sends it back with the second random number. The standard also provides
encryption In cryptography, encryption is the process of encoding information. This process converts the original representation of the information, known as plaintext, into an alternative form known as ciphertext. Ideally, only authorized parties can dec ...
services with the DECT Standard Cipher (DSC). The encryption is fairly weak, using a 35-bit
initialization vector In cryptography, an initialization vector (IV) or starting variable (SV) is an input to a cryptographic primitive being used to provide the initial state. The IV is typically required to be random or pseudorandom, but sometimes an IV only needs to ...
and encrypting the voice stream with 64-bit encryption. While most of the DECT standard is publicly available, the part describing the DECT Standard Cipher was only available under a
non-disclosure agreement A non-disclosure agreement (NDA) is a legal contract or part of a contract between at least two parties that outlines confidential material, knowledge, or information that the parties wish to share with one another for certain purposes, but wis ...
to the phones' manufacturers from
ETSI The European Telecommunications Standards Institute (ETSI) is an independent, not-for-profit, standardization organization in the field of information and communications. ETSI supports the development and testing of global technical standard ...
. The properties of the DECT protocol make it hard to intercept a frame, modify it and send it later again, as DECT frames are based on time-division multiplexing and need to be transmitted at a specific point in time. Unfortunately very few DECT devices on the market implemented authentication and encryption proceduresDr. DECT Secturity: Present, Past, Future
DECT World 2016 Presentations
. Erik Tews, University of Birmingham. 31 May 2016.
and even when encryption was used by the phone, it was possible to implement a
man-in-the-middle attack In cryptography and computer security, a man-in-the-middle, monster-in-the-middle, machine-in-the-middle, monkey-in-the-middle, meddler-in-the-middle, manipulator-in-the-middle (MITM), person-in-the-middle (PITM) or adversary-in-the-middle (AiTM) ...
impersonating a DECT base station and revert to unencrypted mode which allows calls to be listened to, recorded, and re-routed to a different destination.Lucks, Stefan; Schuler, Andreas; Tews, Erik; Weinmann, Ralf-Philipp; Wenzel, Matthias
Attacks on the DECT Authentication Mechanisms
Fischlin, Marc (Ed.): Topics in Cryptology CT-RSA 2009, The Cryptographers' Track at the RSA Conference 2009, San Francisco, CA, USA, April 20–24, 2009.
Erik Tews
DECT Security Analysis (Ph.D. Thesis)
Technische Universität Darmstadt
After an unverified report of a successful attack in 2002, members of the deDECTed.org project actually did reverse engineer the DECT Standard Cipher in 2008, and as of 2010 there has been a viable attack on it that can recover the key. In 2012, an improved authentication algorithm, the DECT Standard Authentication Algorithm 2 (DSAA2), and improved version of the encryption algorithm, the DECT Standard Cipher 2 (DSC2), both based on
AES AES may refer to: Businesses and organizations Companies * AES Corporation, an American electricity company * AES Data, former owner of Daisy Systems Holland * AES Eletropaulo, a former Brazilian electricity company * AES Andes, formerly AES Gener ...
128-bit encryption, were included as optional in the NG-DECT/CAT-iq suite. DECT Forum also launched the DECT Security certification program which mandates the use of previously optional security features in the GAP profile, such as early encryption and base authentication.


Profiles

Various access profiles have been defined in the DECT standard: * Public Access Profile (PAP) (deprecated) * Generic Access Profile (GAP) ETSI EN 300 444 * Cordless Terminal Mobility (CTM) Access Profile (CAP) ETSI EN 300 824 * Data access profiles ** DECT Packet Radio System (DPRS) ETSI EN 301 649 ** DECT Multimedia Access Profile (DMAP) ** Multimedia in the Local Loop Access Profile (MRAP) ** Open Data Access Profile (ODAP) ** Radio in the Local Loop (RLL) Access Profile (RAP) ETSI ETS 300 765 * Interworking profiles (IWP) ** DECT/
ISDN Integrated Services Digital Network (ISDN) is a set of communication standards for simultaneous digital transmission of voice, video, data, and other network services over the digitalised circuits of the public switched telephone network. Wor ...
Interworking Profile (IIP) ETSI EN 300 434 ** DECT/ GSM Interworking Profile (GIP) ETSI EN 301 242 ** DECT/
UMTS The Universal Mobile Telecommunications System (UMTS) is a third generation mobile cellular system for networks based on the GSM standard. Developed and maintained by the 3GPP (3rd Generation Partnership Project), UMTS is a component of the In ...
Interworking Profile (UIP) ETSI TS 101 863


DECT for data networks

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 indoors and using directional antennae outdoors), dedicated spectrum, high interference immunity, open interoperability and data speeds of around 500 kbit/s, DECT appeared at one time to be a superior alternative to
Wi-Fi Wi-Fi () is a family of wireless network protocols, based on the IEEE 802.11 family of standards, which are commonly used for local area networking of devices and Internet access, allowing nearby digital devices to exchange data by radio w ...
. 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-1990s, was too early to find wide application for wireless data outside niche industrial applications. Whilst contemporary providers of Wi-Fi 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 U.S. market, due to FCC spectrum restrictions at that time. By the time mass applications for wireless Internet had emerged, and the U.S. 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 technically competitive wireless data transport had passed.


Health and safety

DECT uses
UHF Ultra high frequency (UHF) is the ITU designation for radio frequencies in the range between 300 megahertz (MHz) and 3 gigahertz (GHz), also known as the decimetre band as the wavelengths range from one meter to one tenth of a meter (on ...
radio, similar to mobile phones, baby monitors, Wi-Fi, and other cordless telephone technologies. The UK
Health Protection Agency The Health Protection Agency (HPA) was a non-departmental public body in the United Kingdom. It was an organisation that was set up by the UK government in 2003 to protect the public from threats to their health from infectious diseases and env ...
(HPA) claims that due to a mobile phone's adaptive power ability, a DECT cordless phone's radiation could actually exceed the radiation of a mobile phone. A DECT cordless phone's radiation has an average output power of 10 mW but is in the form of 100 bursts per second of 250 mW, a strength comparable to some mobile phones. Most studies have been unable to demonstrate any link to health effects, or have been inconclusive.
Electromagnetic field An electromagnetic field (also EM field or EMF) is a classical (i.e. non-quantum) field produced by (stationary or moving) electric charges. It is the field described by classical electrodynamics (a classical field theory) and is the classica ...
s may have an effect on protein expression in laboratory settings but have not yet been demonstrated to have clinically significant effects in real-world settings. The World Health Organization has issued a statement on medical effects of mobile phones which acknowledges that the longer term effects (over several decades) require further research.


See also

* GSM Interworking Profile (GIP) * IP-DECT *
CT2 CT2 is a cordless telephony standard that was used in the early 1990s to provide short-range proto-mobile phone service in some countries in Europe. It is considered the precursor to the more successful DECT system. CT2 was also referred to by its ...
(DECT's predecessor in Europe) * Net3 * CorDECT * WDECT * Unlicensed Personal Communications Services *
Microcell A microcell is a cell in a mobile phone network served by a low power cellular base station (tower), covering a limited area such as a mall, a hotel, or a transportation hub. A microcell is usually larger than a picocell, though the distinction ...
* Wireless local loop


References


Standards

; ETSI EN 300 175 V2.9.1 (2022-03). Digital Enhanced Cordless Telecommunications (DECT) Common Interface (CI): ;ETSI TS 102 939. Digital Enhanced Cordless Telecommunications (DECT) Ultra Low Energy (ULE) Machine to Machine Communications: ; ETSI TS 102 527. Digital Enhanced Cordless Telecommunications (DECT) New Generation DECT: ;ETSI TS 103 636 v1.3.1 (2021-12). DECT-2020 New Radio (NR): ;Digital Enhanced Cordless Telecommunications (DECT):


Further reading

* * *
Technical Report: Multicell Networks based on DECT and CAT-iq
. Dosch & Amand Research


External links


DECT Forum
at dect.org
DECT information
at
ETSI The European Telecommunications Standards Institute (ETSI) is an independent, not-for-profit, standardization organization in the field of information and communications. ETSI supports the development and testing of global technical standard ...

DECTWeb.com

Open source implementation of a DECT stack
{{Authority control Broadband Local loop Mobile telecommunications standards Software-defined radio Wireless communication systems