Terrestrial Trunked Radio
Overview
 
Terrestrial Trunked Radio (TETRA) (formerly known as Trans-European Trunked Radio) is a professional mobile radio
Professional Mobile Radio
Professional mobile radio are field radio communications systems which use portable, mobile, base station, and dispatch console radios...

 and two-way transceiver (colloquially known as a walkie talkie) specification. TETRA was specifically designed for use by government agencies, emergency services, (police
Police
The police is a personification of the state designated to put in practice the enforced law, protect property and reduce civil disorder in civilian matters. Their powers include the legitimized use of force...

 forces, fire departments, ambulance
Ambulance
An ambulance is a vehicle for transportation of sick or injured people to, from or between places of treatment for an illness or injury, and in some instances will also provide out of hospital medical care to the patient...

) for public safety network
Public safety network
A public safety network is a wireless communications network used by emergency services organizations, such as police, fire and emergency medical services, to prevent or respond to incidents that harm or endanger persons or property....

s, rail transportation staff for train radios, transport services and the military
Military
A military is an organization authorized by its greater society to use lethal force, usually including use of weapons, in defending its country by combating actual or perceived threats. The military may have additional functions of use to its greater society, such as advancing a political agenda e.g...

.

TETRA is an European Telecommunications Standards Institute
European Telecommunications Standards Institute
The European Telecommunications Standards Institute is an independent, non-profit, standardization organization in the telecommunications industry in Europe, with worldwide projection...

 (ETSI) standard, first version published 1995; it is mentioned by the European Radiocommunications Committee (ERC).
TETRA uses Time Division Multiple Access
Time division multiple access
Time division multiple access 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, one after the other, each using its own time slot. This...

 (TDMA) with four user channels on one radio carrier
Carrier wave
In telecommunications, a carrier wave or carrier is a waveform that is modulated with an input signal for the purpose of conveying information. This carrier wave is usually a much higher frequency than the input signal...

 and 25 kHz spacing between carriers.
Encyclopedia
Terrestrial Trunked Radio (TETRA) (formerly known as Trans-European Trunked Radio) is a professional mobile radio
Professional Mobile Radio
Professional mobile radio are field radio communications systems which use portable, mobile, base station, and dispatch console radios...

 and two-way transceiver (colloquially known as a walkie talkie) specification. TETRA was specifically designed for use by government agencies, emergency services, (police
Police
The police is a personification of the state designated to put in practice the enforced law, protect property and reduce civil disorder in civilian matters. Their powers include the legitimized use of force...

 forces, fire departments, ambulance
Ambulance
An ambulance is a vehicle for transportation of sick or injured people to, from or between places of treatment for an illness or injury, and in some instances will also provide out of hospital medical care to the patient...

) for public safety network
Public safety network
A public safety network is a wireless communications network used by emergency services organizations, such as police, fire and emergency medical services, to prevent or respond to incidents that harm or endanger persons or property....

s, rail transportation staff for train radios, transport services and the military
Military
A military is an organization authorized by its greater society to use lethal force, usually including use of weapons, in defending its country by combating actual or perceived threats. The military may have additional functions of use to its greater society, such as advancing a political agenda e.g...

.

TETRA is an European Telecommunications Standards Institute
European Telecommunications Standards Institute
The European Telecommunications Standards Institute is an independent, non-profit, standardization organization in the telecommunications industry in Europe, with worldwide projection...

 (ETSI) standard, first version published 1995; it is mentioned by the European Radiocommunications Committee (ERC).

Description

TETRA uses Time Division Multiple Access
Time division multiple access
Time division multiple access 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, one after the other, each using its own time slot. This...

 (TDMA) with four user channels on one radio carrier
Carrier wave
In telecommunications, a carrier wave or carrier is a waveform that is modulated with an input signal for the purpose of conveying information. This carrier wave is usually a much higher frequency than the input signal...

 and 25 kHz spacing between carriers. Both point-to-point and point-to-multipoint transfer can be used. Digital data transmission is also included in the standard though at a low data rate.

TETRA Mobile Stations (MS) can communicate direct-mode operation (DMO) or using trunked-mode operation (TMO) using switching and management infrastructure (SwMI) made of TETRA base stations (TBS). As well as allowing direct communications in situations where network coverage is not available, DMO also includes the possibility of using a sequence of one or more TETRA terminals as relays. This functionality is called DMO gateway (from DMO to TMO) or DMO repeater (from DMO to DMO). In emergency situations this feature allows direct communications underground or in areas of bad coverage.

In addition to voice and dispatch services, the TETRA system supports several types of data communication. Status messages and short data services (SDS) are provided over the system's main control channel, while packet-switched data or circuit-switched data communication uses specifically assigned traffic channels.

TETRA provides for authentication of terminals towards infrastructure and vice versa. For protection against eavesdropping; air interface encryption and end-to-end encryption is available.

The common mode of operation is in a group calling mode
Group call
Group-calling, similar to Conference call, is a means of communication where the calling party wishes to involve multiple parties. In comparison to conference calling, all parties involved in a call always have the opportunity to participate actively. Alternatively, group calling also functions as...

 in which a single button push will connect the user to the users in a selected call group and/or a dispatcher
Dispatcher
Dispatchers are communications personnel responsible for receiving and transmitting pure and reliable messages, tracking vehicles and equipment, and recording other important information...

. It is also possible for the terminal to act as a one-to-one walkie talkie but without the normal range limitation since the call still uses the network. TETRA terminals can act as mobile phone
Mobile phone
A mobile phone is a device which can make and receive telephone calls over a radio link whilst moving around a wide geographic area. It does so by connecting to a cellular network provided by a mobile network operator...

s (cell phones), with a full-duplex direct connection to other TETRA Users or the PSTN. Emergency buttons, provided on the terminals, enable the users to transmit emergency signals, to the dispatcher
Dispatcher
Dispatchers are communications personnel responsible for receiving and transmitting pure and reliable messages, tracking vehicles and equipment, and recording other important information...

, overriding any other activity taking place at the same time.

Advantages of TETRA

The main advantages of TETRA over other technologies (such as GSM) are:
  • The much lower frequency used gives longer range, which in turn permits very high levels of geographic coverage with a smaller number of transmitters, thus cutting infrastructure costs.
  • High spectral efficiency - 4 channels in 25 kHz and no guard bands, compared to GSM with 8 channels in 200 kHz and guard bands.
  • Very fast call set-up - a one to many group call is generally set-up within 0.5 seconds (typical less than 250 msec for a single node call) compared with the many seconds (typically 7 to 10s) that are required for a GSM network.
  • Works at high relative speeds >400 km/h. TETRA was used during the French TGV train speed record on 3 April 2007 at 574.8 km/h.
  • The system contains several mechanisms, designed into the protocols
    Communications protocol
    A communications protocol is a system of digital message formats and rules for exchanging those messages in or between computing systems and in telecommunications...

     and radio parameters, to ensure communication success even during overload situations (e.g., during major public events or disaster situations), thus calls will always get through unlike in cellular systems. The system also supports a range of emergency calling modes.
  • TETRA infrastructure is usually separate from (but connected to) that of the public (mobile) phone networks, resulting in (normally) no call charges for the system owners, substantially more diverse and resilient communications and it is easy to customise and integrate with data applications (vehicle location, GIS databases, dispatch systems, etc.).
  • Unlike most cellular technologies, TETRA networks typically provide a number of fall-back modes such as the ability for a base station to process local calls. So called 'mission critical' networks can be built with TETRA where all aspects are fail-safe/multiple-redundant.
  • In the absence of a network mobiles/portables can use 'direct mode' whereby they share channels directly (walkie-talkie mode).
  • Gateway mode - where a single mobile with connection to the network can act as a relay for other nearby mobiles that are out of range of the infrastructure.
  • TETRA also provides a point-to-point function that traditional analogue emergency services radio systems did not provide. This enables users to have a one-to-one trunked 'radio' link between sets without the need for the direct involvement of a control room operator/dispatcher.
  • Unlike cellular technologies, which connect one subscriber to one other subscriber (one-to-one), TETRA is built to do one-to-one, one-to-many and many-to-many
    Many-to-many
    Many-to-many is a term that describes a communication paradigm and an associated media form. It is the third of three major Internet computing paradigms...

    . These operational modes are directly relevant to the public safety and professional users.
  • TETRA supports both air-interface encryption and end-to-end encryption
    End-to-end encryption
    End-to-end encryption encrypts clear data at source with knowledge of the intended recipient, allowing the encrypted data to travel safely through vulnerable channels End-to-end encryption (E2EE) encrypts clear (red) data at source with knowledge of the intended recipient, allowing the encrypted...

  • Rapid deployment (transportable) network solutions are available for disaster relief and temporary capacity provision.
  • Equipment is available from many suppliers around the world, thus providing the benefits of interoperable competition.
  • Network solutions are available in both the older circuit-switched (telephone like) architectures and flat, IP architectures with soft (software) switches.


Further information is available from the TETRA Association (formerly TETRA MoU) and the standards can be downloaded for free from ETSI.

Disadvantages of TETRA

Its main disadvantages are:
  • Requires a linear amplifier
    Linear amplifier
    A linear amplifier is an electronic circuit whose output is proportional to its input, but capable of delivering more power into a load. The term usually refers to a type of radio-frequency power amplifier, some of which have output power measured in kilowatts, and are used in amateur radio...

     to meet the stringent RF specifications that allow it to exist alongside other radio services.
  • Handsets are more expensive than cellular. This is due to the more difficult technology, smaller economies of scale, and different business model (e.g., need for security, high powers and robustness).
  • Data transfer is efficient and long range (many km), but slow by modern standards at 7.2 kbit/s per timeslot (3.5 kbit/slot net packet data throughput), although the Tetra standard states that up to 4 timeslots can be combined into a single data channel to achieve higher rates whilst still fitting into a single 25 kHz bandwidth channel. Albeit there are no deployed networks where this data rate has reportedly been achieved from mobile users (hand portables or vehicle mobiles). Latest version of standard supports 115.2 kbit/s in 25 kHz or up to 691.2 kbit/s in an expanded 150 kHz channel. But again, no deployed networks supporting such data rates are currently in operation.
  • Due to the pulsed nature of TDMA employed by the protocol and higher powers than cellular, handsets (only) can sometimes interfere with badly designed (usually old) or sensitive electronic devices such as broadcast (TV) receivers, hospital equipment, speed cameras. This has prompted some concerns from users of sensitive devices such as heart pacemakers but there are no documented reports of problems even though used regularly by many ambulance crews. As a precaution, users of these equipments should take care with any RF transmitting equipment when used in close proximity (e.g., < 1 metre distance.)

TETRA usage

there were 114 countries using TETRA systems in Western Europe, Eastern Europe, Middle East, Africa, Asia Pacific, Caribbean and Latin America.

The TETRA-system is in use by the public sector in the following countries. Only TETRA network infrastructure installations are listed. TETRA being an open standard, each of these networks can use any mix of TETRA mobile terminals from a wide range if suppliers.
Continent Country Supplier Name Agency Status
Asia China Mainland EADS / Cassidian Shenyang Metro
Shenyang Metro
Shenyang Metro is a metro system in the city of Shenyang, Liaoning province in China. This is the the 7th operating subway system in Mainland China and the first in Northeast China.-Network:...

Transport In use: Linie 1
Rolling out: Line 2
EADS / Cassidian Shenzhen Metro
Shenzhen Metro
The Shenzhen Metro is the subway or underground system for the city of Shenzhen in Guangdong province, China. The system opened on 28 December 2004, making Shenzhen the seventh city in mainland China to have a subway after Beijing, Tianjin, Shanghai, Guangzhou, Dalian, and Wuhan. The Shenzhen...

Transport Ordered 5/2010
EADS / Cassidian Guangzhou
Guangzhou
Guangzhou , known historically as Canton or Kwangchow, is the capital and largest city of the Guangdong province in the People's Republic of China. Located in southern China on the Pearl River, about north-northwest of Hong Kong, Guangzhou is a key national transportation hub and trading port...

16th Asian Games in 2010 Ordered 2010
Hong Kong EADS / Cassidian Hong Kong International Airport (HKIA) 2008 Beijing Olympics and Paralympic Games (Hong Kong Equestrian Event) Used from July 2008 to October 2008
EADS / Cassidian Hong Kong Fire Services Department Fire service and ambulance In use.
Motorola / Dimetra
Dimetra
DIMETRA IP is the brand name under which Motorola markets its implementation of the TETRA digital radio communications standard.-Overview:Tetra is a scalable radio network technology typically used by emergency services and other Government agencies...

Hong Kong Police Force Police In use.
Artevea
Artevea
Artevea Digital is a TETRA infrastructure manufacturer.-Product range:Artevea designs, develops and supplies digital trunking systems worldwide for the public safety market, which includes, military, paramilitary forces, police, fire service, ports, oil and gas, ambulance or any mission critical...

Mass Transit Railway (MTR
MTR
Mass Transit Railway is the rapid transit railway system in Hong Kong. Originally opened in 1979, the system now includes 211.6 km of rail with 155 stations, including 86 railway stations and 69 light rail stops...

)
Transport In use.
Motorola / Dimetra
Dimetra
DIMETRA IP is the brand name under which Motorola markets its implementation of the TETRA digital radio communications standard.-Overview:Tetra is a scalable radio network technology typically used by emergency services and other Government agencies...

Hong Kong International Airport (HKIA) Transport In use since Feb 2009
India Military College of Telecommunication Engineering (MCTE) Indian Army In use since 2004 at Mhow, Indore, Madhya Pradesh.
Motorola / Dimetra
Dimetra
DIMETRA IP is the brand name under which Motorola markets its implementation of the TETRA digital radio communications standard.-Overview:Tetra is a scalable radio network technology typically used by emergency services and other Government agencies...

Delhi Metro Rail Corporation Ltd Transport In use since 2002. The First TETRA in India.
C-DAC TETRA with Automatic Dial 100 (AD100). Kerala Police. In use by police, Trivandrum city. Since 2008.
Sepura / Rohde and Schwarz TETRA with Automatic Dial 100 (AD100). Gurgaon Police. In use by police, Gurgaon city. Since 2009.
In Salem from Aug 2011.
Indonesia Motorola / Dimetra
Dimetra
DIMETRA IP is the brand name under which Motorola markets its implementation of the TETRA digital radio communications standard.-Overview:Tetra is a scalable radio network technology typically used by emergency services and other Government agencies...

, installed by PT. Mobilkom Telekomindo
SCADA PT. Chevron Pacific Indonesia HOOU In use since 2009 at Duri, Riau, Indonesia.
Macao Artevea
Artevea
Artevea Digital is a TETRA infrastructure manufacturer.-Product range:Artevea designs, develops and supplies digital trunking systems worldwide for the public safety market, which includes, military, paramilitary forces, police, fire service, ports, oil and gas, ambulance or any mission critical...

Melco-Crown Entertainment Casino-Hotels: Altira (formerly Crown Macau), and City of Dreams In use since 2007.
Forças de Segurança de Macau All emergency services. In use.
Malaysia EADS Segi Maju (SEGI) Public operator In use.
Pakistan Ministry of Interior Police In use, nationwide.
South Korea EADS Korea Electric Power Corporation (KEPCO) Electricity In use.
Taiwan [行車調度無線電話], Taiwan Railways Administration, Railway Police Bureau In use.
Africa Morocco Rohill ADM
Société Nationale des Autoroutes du Maroc
The Société Nationale des Autoroutes du Maroc is the Morocco's national authority for the management of over 850 km of Moroccan expressways. ADM is based in Rabat....

Highway authority Rolling out.
South Africa Police, Traffic Police SAPS Gauteng Gauteng Province
Municipality, fire, and ambulance. City of Cape Town Cape Peninsula
Rohill Mbombela Local Municipality Nelpruit Mpumalanga
Sudan Artevea
Artevea
Artevea Digital is a TETRA infrastructure manufacturer.-Product range:Artevea designs, develops and supplies digital trunking systems worldwide for the public safety market, which includes, military, paramilitary forces, police, fire service, ports, oil and gas, ambulance or any mission critical...

Ministry of Interior Police In use, Nationwide.
Europe Austria Motorola / Dimetra
Dimetra
DIMETRA IP is the brand name under which Motorola markets its implementation of the TETRA digital radio communications standard.-Overview:Tetra is a scalable radio network technology typically used by emergency services and other Government agencies...

TETRON Police, fire, ambulance, and local train company. In use, in all states except Tyrol and Vorarlberg (still rolling out).
Belgium EADS/Since 1998 A.S.T.R.I.D. Police, fire, ambulance, customs, coast guard, hospitals, Red Cross, department of Justice, utility companies, airports, ports, lifeguard service, military. Nation-wide network.
Rohde & Schwarz since 2011/ ACCESSNET-T ENTROPIA DIGITAL Commercial & Private Security users. (www.entropia.eu) Flanders & Brussels/Roaming with Nationwide The Netherlands
Denmark Motorola / Dimetra
Dimetra
DIMETRA IP is the brand name under which Motorola markets its implementation of the TETRA digital radio communications standard.-Overview:Tetra is a scalable radio network technology typically used by emergency services and other Government agencies...

SINE All amergency authorities, incl. police, fire, and ambulance. Nationwide coverage (99,5%) in use.
Estonia Police, fire, ambulance, and customs Rolling out.
Finland Nokia; now EADS VIRVE
VIRVE
VIRVE is the Finnish authorities' telecommunications network. It is based on the Terrestrial Trunked Radio standard. It is one of few nation-wide TETRA networks in the world....

Police, fire, ambulance, customs, defence forces, and border guard. Nation-wide network.
HelenNet Energy company Helsingin Energia
Helsingin Energia
Helsingin Energia , Helsingfors Energi , founded in 1909 and based in Helsinki, is one of the largest energy companies in Finland...

, tram operator HKL-Raitioliikenne
Helsinki City Transport
Helsinki City Transport or HKL is the official city-owned public transport company in Helsinki, Finland. It operates the Helsinki metro, Helsinki tram and ferry boat traffic...

, and several bus operators on HRTA's lines. Also used by some security guard companies, mostly securing HRTA's transport. Available for lease for various short-term uses.
In use, covers greater Helsinki region.
Germany EADS BOSNET Police, fire, ambulance, customs, and coast guard. Nationwide
Greece C4I Police, fire, and coast guard. Attica region
OTE Tetra Services Fully commercial network, emergency services, utility companies, and private users. Nationwide (partial coverage).
Hungary Pro-M Ltd. EDR (acronym for Unified Digital Radiosystem) Ambulance, army, Central Office for Administrative and Electronic Public Services, Civil Defence, Hungarian Prison Service, Hungarian Customs and Finance Guard, Disaster Management, fire, Hungarian Secret Services, Ministry of Environment and Water, and police. In-use.
Iceland TETRA Iceland All emergency services, most utility companies, and private users. In-use.
Ireland Motorola / Dimetra
Dimetra
DIMETRA IP is the brand name under which Motorola markets its implementation of the TETRA digital radio communications standard.-Overview:Tetra is a scalable radio network technology typically used by emergency services and other Government agencies...

TETRA Ireland Garda Siochana, HSE National Ambulance Service Nation-wide roll-out network in progress. Roll out has begun on the HSE National Ambulance Service. The fire services are planning to implement in the coming years. As of July 2011, TETRA Ireland now operates the national Paging System.
Italy SELEX Rete Interpolizie Polizia di Stato (Italian state police), the Carabinieri (military police), the Guardia di Finanza (customs police), the Polizia Penitenziaria (prison police), and for the Corpo Forestale Italiano (Italian forest brigades) Rolling out.
Latvia Artevea
Artevea
Artevea Digital is a TETRA infrastructure manufacturer.-Product range:Artevea designs, develops and supplies digital trunking systems worldwide for the public safety market, which includes, military, paramilitary forces, police, fire service, ports, oil and gas, ambulance or any mission critical...

Ventamonjaks Serviss Ltd, Ventspils Oil and gas. In use since 2007.
Netherlands Motorola / Dimetra
Dimetra
DIMETRA IP is the brand name under which Motorola markets its implementation of the TETRA digital radio communications standard.-Overview:Tetra is a scalable radio network technology typically used by emergency services and other Government agencies...

T2000 Police, fire, and ambulance. Nation-wide network.
Motorola since 2007/ Dimetra
Dimetra
DIMETRA IP is the brand name under which Motorola markets its implementation of the TETRA digital radio communications standard.-Overview:Tetra is a scalable radio network technology typically used by emergency services and other Government agencies...

ENTROPIA DIGITAL Commercial users.(www.entropia.eu) Nation-wide network /Roaming with Entropia Digital in Belgium
Rohde & Schwarz since 2010/ ACCESSNET-T ENTROPIA DIGITAL Cityguards and commercial use. (www.entropia.eu) Rotterdam area network /Roaming with Entropia Digital in Belgium
Norway Motorola / Dimetra
Dimetra
DIMETRA IP is the brand name under which Motorola markets its implementation of the TETRA digital radio communications standard.-Overview:Tetra is a scalable radio network technology typically used by emergency services and other Government agencies...

Norwegian Public Safety Radio
Norwegian Public Safety Radio
The Norwegian Public Safety Radio is a public safety network system based on Terrestrial Trunked Radio which is being implemented by the Directorate for Emergency Communication throughout Norway...

Police, fire, ambulance, and search and rescue. Roll-out
Portugal SIRESP Police, fire, and ambulance. Nation-wide roll-out; in use since 2007.
Poland Motorola Ministry of Interior, Polish army, and Warsaw police. Police, fire, public transport, airports, and army. Local TETRA Networks in use since 2000; national roll-out expected to start in 2011.
Romania Motorola / Dimetra
Dimetra
DIMETRA IP is the brand name under which Motorola markets its implementation of the TETRA digital radio communications standard.-Overview:Tetra is a scalable radio network technology typically used by emergency services and other Government agencies...

Special Telecommunications Service (STS) Police, fire, and search and rescue. Nation-wide
Motorola Dimetra
Dimetra
DIMETRA IP is the brand name under which Motorola markets its implementation of the TETRA digital radio communications standard.-Overview:Tetra is a scalable radio network technology typically used by emergency services and other Government agencies...

Ministry of Administration and Interior (MAI) / Romanian Border Police (RBP) In use since 2008 for police, emergency and search and rescue agencies from Romanian border counties-wide.
Cassidian TETRA EADS Ministry of Administration and Interior (MAI) / Romanian Border Police (RBP) In use since 2010 for police, emergency and search and rescue agencies from Romanian border counties-wide.
Serbia Ministry of Interior Police special units
Slovenia Ministry of Interior Police In central Slovenia.
Sweden EADS / Sepura RAKEL Mainly police (including prison authorities), fire, ambulance, and customs authority. Also used by the military, coast guard, private security companies and several state and regional authorities. Roll-out
United Kingdom Motorola / Dimetra
Dimetra
DIMETRA IP is the brand name under which Motorola markets its implementation of the TETRA digital radio communications standard.-Overview:Tetra is a scalable radio network technology typically used by emergency services and other Government agencies...

 / Sepura
Airwave
Airwave (communications network)
The Airwave network is a mobile communications network dedicated for the use by the emergency services in the United Kingdom. Designed to be both secure and resilient it allows multiple agencies integrated communications through a nationwide network. It is a secure digital, encrypted network and...

Police, fire, NHS
National Health Service
The National Health Service is the shared name of three of the four publicly funded healthcare systems in the United Kingdom. They provide a comprehensive range of health services, the vast majority of which are free at the point of use to residents of the United Kingdom...

, armed forces, Highways Agency Traffic Officers
Highways Agency Traffic Officers
The Highways Agency Traffic Officer Service is an operational unit within the Highways Agency in England. In April 2004, Highways Agency Traffic Officers began working alongside police on motorways in the West Midlands. The roll out of traffic officers was completed on 18 July 2006 and they now...

, Civil Contingency Services, HM Coastguard, Red Cross, and misc. emergency services.
Full roll out nearly complete, with a few fire/ambulance services remaining.
Motorola / Dimetra
Dimetra
DIMETRA IP is the brand name under which Motorola markets its implementation of the TETRA digital radio communications standard.-Overview:Tetra is a scalable radio network technology typically used by emergency services and other Government agencies...

CONNECT
Connect Project
The Connect Project is a project name for a radio communications system developed for Transport for London. The system will introduce Terrestrial Trunked Radio technology to the London Underground.-Overview:...

Transport for London (London Underground
London Underground
The London Underground is a rapid transit system serving a large part of Greater London and some parts of Buckinghamshire, Hertfordshire and Essex in England...

)
Used by all Tube
London Underground
The London Underground is a rapid transit system serving a large part of Greater London and some parts of Buckinghamshire, Hertfordshire and Essex in England...

 staff and relaying Airwave
Airwave (communications network)
The Airwave network is a mobile communications network dedicated for the use by the emergency services in the United Kingdom. Designed to be both secure and resilient it allows multiple agencies integrated communications through a nationwide network. It is a secure digital, encrypted network and...

 for BTP
British Transport Police
The British Transport Police is a special police force that polices those railways and light-rail systems in Great Britain for which it has entered into an agreement to provide such services...

 when underground.
Middle East Israel Motorola. Mountain Rose. Israel Defense Forces (IDF). In use by IDF, country-wide.
United Arab Emirates Nedaa Police, emergency services, and professional communications. Dubai
Dubai
Dubai is a city and emirate in the United Arab Emirates . The emirate is located south of the Persian Gulf on the Arabian Peninsula and has the largest population with the second-largest land territory by area of all the emirates, after Abu Dhabi...

, Sharjah, Ajman
Ajman
Ajman , also spelt Ujman, is one of the seven emirates constituting the United Arab Emirates . With an area of just 260 square kilometres , Ajman is the smallest emirate by area...

, Umm Al-Qaiwain, Ras Al-Khaimah
Ras al-Khaimah
Ras al-Khaimah is one of the emirates of the United Arab Emirates , in the east of the Persian Gulf. It is in the northern part of the UAE bordering Oman's exclave. The capital city and home of most residents is also called Ras al-Khaimah. The city has a population of 263,217 as of 2008. The city...

, and Fujairah
Fujairah
Fujairah is one of the seven emirates that make up the United Arab Emirates, and the only one on the Gulf of Oman in the country's east instead of Persian Gulf .-History:...

 operational.
Polikom Police, emergency services, and professional communications. Abu Dhabi
Abu Dhabi
Abu Dhabi , literally Father of Gazelle, is the capital and the second largest city of the United Arab Emirates in terms of population and the largest of the seven member emirates of the United Arab Emirates. Abu Dhabi lies on a T-shaped island jutting into the Persian Gulf from the central western...

Latin America Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...

Rohde & Schwarz / Sepura Mazatlán, Sinaloa Police & Emergency Services Police, Emergency Services operational. Operational
Caribbean Windward Islands
Windward Islands
The Windward Islands are the southern islands of the Lesser Antilles, within the West Indies.-Name and geography:The Windward Islands are called such because they were more windward to sailing ships arriving in the New World than the Leeward Islands, given that the prevailing trade winds in the...

 and Leeward Islands
Leeward Islands
The Leeward Islands are a group of islands in the West Indies. They are the northern islands of the Lesser Antilles chain. As a group they start east of Puerto Rico and reach southward to Dominica. They are situated where the northeastern Caribbean Sea meets the western Atlantic Ocean...

Rohill Zenitel Police, emergency services, oil and professional communications. Aruba
Aruba
Aruba is a 33 km-long island of the Lesser Antilles in the southern Caribbean Sea, located 27 km north of the coast of Venezuela and 130 km east of Guajira Peninsula...

, Bonaire, Curaçao
Curaçao
Curaçao is an island in the southern Caribbean Sea, off the Venezuelan coast. The Country of Curaçao , which includes the main island plus the small, uninhabited island of Klein Curaçao , is a constituent country of the Kingdom of the Netherlands...

, Sint Maarten, Saint Martin
Saint Martin
Saint Martin is an island in the northeast Caribbean, approximately east of Puerto Rico. The 87 km2 island is divided roughly 60/40 between France and the Kingdom of the Netherlands ; however, the Dutch side has the larger population. It is one of the smallest sea islands divided between...

, Saba, Sint Eustatius, and Anguilla
Anguilla
Anguilla is a British overseas territory and overseas territory of the European Union in the Caribbean. It is one of the most northerly of the Leeward Islands in the Lesser Antilles, lying east of Puerto Rico and the Virgin Islands and directly north of Saint Martin...

 operational.

Radio aspects

To send information TETRA uses a digital modulation scheme known as π/4 DQPSK
Phase-shift keying
Phase-shift keying is a digital modulation scheme that conveys data by changing, or modulating, the phase of a reference signal ....

, this is a form of phase shift keying. The symbol (baud) rate is 18,000 symbols per second, and each symbol maps to 2 bits, thus resulting in 36,000 bit/s gross.

As a form of phase shift keying is used to transmit data during each burst, it would seem reasonable to expect the transmit power to be constant. However it is not. This is because the sideband
Sideband
In radio communications, a sideband is a band of frequencies higher than or lower than the carrier frequency, containing power as a result of the modulation process. The sidebands consist of all the Fourier components of the modulated signal except the carrier...

s, which are essentially a repetition of the data in the main carrier's modulation, are filtered off with a sharp filter so that unnecessary spectrum is not used up. This results in an amplitude modulation and is why TETRA requires linear amplifiers. The resulting ratio of peak to mean (RMS) power is 3.65 dB. If non-linear (or not-linear enough) amplifiers are used, the sidebands re-appear and cause interference on adjacent channels. Commonly used techniques for achieving the necessary linearity include Cartesian loops, and adaptive predistortion.

The base stations normally transmit continuously and (simultaneously) receive continuously from various mobiles on different carrier frequencies; hence the TETRA system is a Frequency Division Duplex (FDD) system. TETRA also uses FDMA/TDMA (see above) like GSM. The mobiles normally only transmit on 1 slot/4 and receive on 1 slot/4 (instead of 1 slot/8 for GSM).

Speech signals in TETRA are sampled at 8 kHz and then compressed with a vocoder
Vocoder
A vocoder is an analysis/synthesis system, mostly used for speech. In the encoder, the input is passed through a multiband filter, each band is passed through an envelope follower, and the control signals from the envelope followers are communicated to the decoder...

 using a technique called Adaptive Code Excited Linear Prediction (ACELP). This creates a data stream of 4.567 kbit/s. This data stream is error-protection encoded before transmission to allow correct decoding even in noisy (erroneous) channels. The data rate after coding is 7.2 kbit/s. The capacity of a single traffic slot when used 17/18 frames.

A single slot consists of 255 usable symbols, the remaining time is used up with synchronisation sequences and turning on/off, etc. A single frame consists of 4 slots, and a multiframe (whose duration is 1.02 seconds) consists of 18 frames. Hyperframes also exist, but are mostly used for providing synchronisation to encryption algorithms.

The downlink (i.e., the output of the base station) is normally a continuous transmission consisting of either specific communications with mobile(s), synchronisation or other general broadcasts. All slots are usually filled with a burst even if idle (continuous mode). Although the system uses 18 frames per second only 17 of these are used for traffic channels, with the 18th frame reserved for signalling, Short Data Service messages (like SMS in GSM) or synchronisation. The frame structure in TETRA (17.65 frames per second), consists of 18,000 symbols/s / 255 symbols/slot / 4 slots/frame, and is the cause of the perceived "amplitude modulation" at 17 Hz and is especially apparent in mobiles/portables which only transmit on one slot/4. They use the remaining three slots to switch frequency to receive a burst from the base station two slots later and then return to their transmit frequency (TDMA
Time division multiple access
Time division multiple access 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, one after the other, each using its own time slot. This...

).

Radio frequencies

TETRA frequencies in South America
Emergency Systems
Number | Frequency pair (MHz)
Band 1 Band 2
1 380–383 390–393
2 383–385 393–395
Civil systems
Number | Frequency pair (MHz)
Band 1 Band 2
1 410–420 420–430
2 870–876 915–921
3 450–460 460–470
4 385–390 395–399.9

TETRA frequencies in other countries
Country Allocation Frequency pairs (MHz)
France civilian/private 410-430
France Emergency services 380–400
Germany Emergency services 380–385, 390–395
Italy Emergency services / armed forces 380-390
Italy civilian/private 462
Norway Emergency services 380–385, 390–395, 406.1–426, 870–876
South Africa TBD TBD

Air interface encryption

To provide confidentiality the TETRA air interface is encrypted using one of the TETRA Encryption Algorithm (TEA) ciphers. The encryption provides confidentiality (protect against eavesdropping) as well as protection of signalling.

Currently 4 different ciphers are defined. These TEA ciphers should not be confused with the block cipher Tiny Encryption Algorithm
Tiny Encryption Algorithm
In cryptography, the Tiny Encryption Algorithm is a block cipher notable for its simplicity of description and implementation, typically a few lines of code...

. The TEA ciphers have different availability due to export and use restrictions. Few details are published concerning these proprietary ciphers. Riess mentions in early TETRA design documents that encryption should be done with a stream cipher
Stream cipher
In cryptography, a stream cipher is a symmetric key cipher where plaintext digits are combined with a pseudorandom cipher digit stream . In a stream cipher the plaintext digits are encrypted one at a time, and the transformation of successive digits varies during the encryption...

, due to the property of not propagating transmission errors. Parkinson later confirms this and explains that TEA is a stream cipher with 80-bit keys.  TEA1 and TEA4 provides basic level of security. They are meant for commercial use. The TEA2 cipher is restricted to European Public Safety organisations. The TEA3 cipher is for situations where TEA2 is suitable but not available.
Additional information

Cell re-selection (or hand-over) in images

This first representation demonstrates where the slow reselect threshold (SRT) the fast reselect threshold (FRT) and propagation Delay exceed parameters are most likely to be. These are represented in association with the decaying radio carrier as the distance increases from the TETRA Base Station
Base station
The term base station can be used in the context of land surveying and wireless communications.- Land surveying :In the context of external land surveying, a base station is a GPS receiver at an accurately-known fixed location which is used to derive correction information for nearby portable GPS...

.

From this illustration, these SRT and FRT triggering points are associated to the decaying radio signal strength of the respective cell carriers. The thresholds are situated so that the cell reselection procedures occur on time and assure communication continuity for on-going communication calls.

Initial cell selection

The next diagram illustrates where a given TETRA radio cell initial selection. The initial cell selection is performed by procedures located in the MLE and in the MAC. When the cell selection is made, and possible registration is performed, the MS (mobile station) is said to be attached to the cell. The mobile is allowed to initially select any suitable cell that has a positive C1 value; i.e., the received signal level is greater than the minimum receive level for access parameter.

The initial cell selection procedure shall ensure that the MS selects a cell in which it can reliably decode downlink data (i.e., on a main control channel/MCCH), and which has a high probability of uplink communication. The minimum conditions that shall have to be met are that C1 > 0. Access to the network shall be conditional on the successful selection of a cell.

At mobile switch on, the mobile makes its initial cell selection of one of the base stations, which indicates the initial exchanges at activation.
  • Refer to EN 300 392 2 16.3.1 Activation and control of underlying MLE Service
  • Note 18.5.12 Minimum RX access level


The minimum receive access level information element shall indicate the minimum received signal level required at the SwMI in a cell, either the serving cell or a neighbour cell as defined in table 18.24.

Cell improvable

The next diagram illustrates where a given TETRA radio cell becomes improvable. The serving cell becomes improvable when the following occurs: the C1 of the serving cell is below the value defined in the radio network parameter cell reselection parameters, slow reselect threshold for a period of 5 seconds, and the C1 or C2 of a neighbour cell exceeds the C1 of the serving cell by the value defined in the radio network parameter cell reselection parameters, slow reselect hysteresis for a period of 5 seconds.

Cell usable

The next diagram illustrates where a given TETRA radio cell becomes Usable. A neighbour cell becomes radio usable when the cell has a downlink radio connection of sufficient quality.

The following conditions must be met in order to declare a neighbour cell radio usable: The neighbour cell has a path loss parameter C1 or C2 that is greater than the following: (FAST_RESELECT_THRESHOLD+FAST_RESELECT_HYSTERISIS) for a period of 5 seconds, and the service level provided by the neighbour cell is higher than that of the serving cell. No successful cell reselection shall have taken place within the previous 15 seconds unless MM requests a cell reselection. The MS-MLE shall check the criterion for serving cell relinquishment as often as one neighbour cell is scanned or monitored.

The following conditions will cause the MS to rate the neighbour cell to have higher service level than the current serving cell:
  • The MS subscriber class is supported on the neighbour cell but not on the serving cell.
  • The neighbour cell is a priority cell and the serving cell is not.
  • The neighbour cell supports a service (that is, TETRA standard speech, packet data, or encryption) that is not supported by the serving cell and the MS requires that service to be available.
  • The cell service level indicates that the neighbour cell is less loaded than the serving cell.


Cell relinquishable (abandonable)

The next diagram illustrates where a given TETRA radio cell becomes relinquishable (abandonable). The serving cell becomes relinquishable when the following occurs:
The C1 of the serving cell is below the value defined in the radio network parameter cell reselection parameters, fast reselect threshold, for a period of 5 seconds, and the C1 or C2 of a neighbour cell exceeds the C1 of the serving cell by the value defined in the radio network parameter cell reselection parameters, fast reselect hysteresis, for a period of 5 seconds.

No successful cell reselection shall have taken place within the previous 15 seconds unless MM (Mobility Management) requests a cell reselection. The MS-MLE shall check the criterion for serving cell relinquishment as often as one neighbour cell is scanned or monitored.

Radio down-link failure

When the FRT threshold is breached, the MS is in a situation where it is essential to relinquish (or abandon) the serving cell and obtain another of at least Usable quality. That is to say, the mobile station is aware that the radio signal is decaying rapidly, and must cell reselect rapidly, before communications are terminated because of radio link failure. When the mobile station radio-signal breaches the minimum receive level, the radio is no longer in a position to maintain acceptable communications for the user, and the radio link is broken.

Radio link failure: (C1 < 0). Using the suggested values, this would be satisfied with the Serving Cell Level below −105 dBm. Cell reselection procedures are then activated in order to find a suitable radio base station.
Infrastructure TETRA Parameters to be Verified

This table serves only as a guide.
Type of radio cover Parameter Distance (km) Type of communication
City < 4 < 8 Pedestrian/metro
Sub-urban 10–18 20–36 Bus/train
Countryside 18–31 36–62 Inter-regional train
In Air > 32 > 64 In flight


A virtual MMI for TETRA radio terminals

Any given TETRA radio terminal using Java
Java (programming language)
Java is a programming language originally developed by James Gosling at Sun Microsystems and released in 1995 as a core component of Sun Microsystems' Java platform. The language derives much of its syntax from C and C++ but has a simpler object model and fewer low-level facilities...

 (Java ME/CLDC) based technology, provides the end user with the communication rights necessary to fulfil his or her work role on any short duration assignment.

For dexterity, flexibility, and evolution ability, the public transportation radio engineering department, have chosen to use the open sources, Java language specification administered by Sun and the associated work groups in order to produce a transport application tool kit.

TETRA MMI

Service acquisition admits different authorised agents to establish communication channels between different services by calling the service identity, and without possessing the complete knowledge of the ISSI, GSSI, or any other TETRA related communication establishment numbering plan. Service acquisition is administered through a communication rights centralised service or roll allocation server, interfaced into the TETRA core network.

In summary, the TETRA MMI aims are to:
  • Allow any given agent while in exercise, to exploit any given radio terminal without materiel constraint.
  • Provide specific transportation application software to the end-user agents (service acquisition, fraud, and aggression control).


This transport application tool-kit has been produced successfully and with TETRA communication technology and assures for the public transport application requirements for the future mentioned hereafter.

The home (main) menu presents the end user with three possibilities:
  1. Service acquisition,
  2. Status SDS,
  3. End-user parameters.


Service acquisition provides a means of virtually personalising the end user to any given radio terminal and onto TETRA network for the duration the end user conserves the terminal under his possession.

Status SDS provides the end user with a mechanism for generating a 440 Hz repeating tone that signals a fraud occurrence to members within the same (dynamic or static) Group Short Subscriber Identity (GSSI) or to a specific Individual Short Subscriber Identity (ISSI
Subscriber Identity Module
A subscriber identity module or subscriber identification module is an integrated circuit that securely stores the International Mobile Subscriber Identity and the related key used to identify and authenticate subscriber on mobile telephony devices .A SIM is held on a removable SIM card, which...

) for the duration of the assignment (an hour, a morning patrol or a given short period allocated to the assignment). The advantage being that each of the end users may attach themselves to any given terminal, and group for short durations without requiring any major reconfiguration by means of radio software programming tools. Similarly, the aggression feature functions, but with a higher tone frequency (880 Hz), and with a quicker repetitious nature, so to highlight the urgency of the alert.

The parameters tab provides an essential means to the terminal end-user allowing them to pre-configure the target (preprogrammed ISSI
Subscriber Identity Module
A subscriber identity module or subscriber identification module is an integrated circuit that securely stores the International Mobile Subscriber Identity and the related key used to identify and authenticate subscriber on mobile telephony devices .A SIM is held on a removable SIM card, which...

or GSSI ) destination communication number. With this pre-programmed destination number, the end-user shall liaise with the destination radio terminal or roll allocation server, and may communicate, in the group, or into a dedicated server to which the service acquisition requests are received, preprocessed, and ultimately dispatched though the TETRA core network. This simplifies the reconfiguration or recycling configuration process allowing flexibility on short assignments.

The parameters tab also provides a means of choosing between preselected tones to match the work group requirements for the purposes of fraud and aggression alerts. A possibility of selecting any given key available from the keypad to serve as an aggression or fraud quick key is also made possible though the transport application software tool kit. It is recommend to use the Asterisk
Asterisk
An asterisk is a typographical symbol or glyph. It is so called because it resembles a conventional image of a star. Computer scientists and mathematicians often pronounce it as star...

 and the Hash keys for the fraud and aggression quick keys respectively. For the fraud and aggression tones, it is also recommend to use 440 Hz slow repeating tone (blank space 500 milli-seconds) and 880 Hz fast repeating tone (blank space 250 milliseconds) respectively. The tone options are as follows: 440 Hz 620 Hz, 880 Hz, and 1060 Hz.

The parameters page provides an aid or help menu and the last tab within parameters describes briefly the tool kit the version and the history of the transport application tool kit to date.

Refer also to:
  • JSR-118
    Java Community Process
    The Java Community Process or JCP, established in 1998, is a formalized process that allows interested parties to get involved in the definition of future versions and features of the Java platform....

    ;
  • Mobile Information Device Profile, JSR-37
    Java Community Process
    The Java Community Process or JCP, established in 1998, is a formalized process that allows interested parties to get involved in the definition of future versions and features of the Java platform....

    ;
  • Wireless Messaging API, JSR120
    Java Community Process
    The Java Community Process or JCP, established in 1998, is a formalized process that allows interested parties to get involved in the definition of future versions and features of the Java platform....

    ;
  • Connected Limited Device Configuration, JSR-139
    Java Community Process
    The Java Community Process or JCP, established in 1998, is a formalized process that allows interested parties to get involved in the definition of future versions and features of the Java platform....

    ; and
  • Technology for the Wireless Industry, JTWI-185
    Java Community Process
    The Java Community Process or JCP, established in 1998, is a formalized process that allows interested parties to get involved in the definition of future versions and features of the Java platform....

    .

See also

  • Artevea
    Artevea
    Artevea Digital is a TETRA infrastructure manufacturer.-Product range:Artevea designs, develops and supplies digital trunking systems worldwide for the public safety market, which includes, military, paramilitary forces, police, fire service, ports, oil and gas, ambulance or any mission critical...

     Provider of TETRA Communication Systems under T-MATRIX
    TMATRIX
    T-MATRIX is the brand name under which Artevea markets its implementation of the TETRA digital radio communications standard.-Overview:TETRA is a radio network technology which is used for various emergency services like, military, paramilitary forces, police, fire service, ports, oil and gas,...

     brand
  • Digital Radio Mobile functions similar as TETRA, but less bandwidth and cheaper
  • EADS
    EADS
    The European Aeronautic Defence and Space Company N.V. is a global pan-European aerospace and defence corporation and a leading defence and military contractor worldwide...

     Secure Networks, provider of TETRA Networks after it bought Nokia
    Nokia
    Nokia Corporation is a Finnish multinational communications corporation that is headquartered in Keilaniemi, Espoo, a city neighbouring Finland's capital Helsinki...

    's PMR business at 2005. Also supplier of Tetrapol systems.
  • Motorola
    Motorola
    Motorola, Inc. was an American multinational telecommunications company based in Schaumburg, Illinois, which was eventually divided into two independent public companies, Motorola Mobility and Motorola Solutions on January 4, 2011, after losing $4.3 billion from 2007 to 2009...

     provider of TETRA Networks under Dimetra IP
    Dimetra
    DIMETRA IP is the brand name under which Motorola markets its implementation of the TETRA digital radio communications standard.-Overview:Tetra is a scalable radio network technology typically used by emergency services and other Government agencies...

     brand
  • MSX Communications is a TETRA system integration and application developer with office located in Dubai, United Arab Emirates.
  • NXDN
    NXDN
    NXDN is a Common Air Interface technical protocol for mobile communications. It was developed jointly by Icom Incorporated and Kenwood Corporation. was formed in order to promote the NXDN protocol in North and South America...

    , a two-way digital radio standard with similar characteristics
  • P25
    P25
    Project 25 is a suite of standards for digital radio communications for use by federal, state/province and local public safety agencies in North America to enable them to communicate with other agencies and mutual aid response teams in emergencies...

    , a TIA
    Telecommunications Industry Association
    The Telecommunications Industry Association is accredited by the American National Standards Institute to develop voluntary, consensus-based industry standards for a wide variety of ICT products, and currently represents nearly 400 companies...

     APCO standard used in North America
  • PowerTrunk is a TETRA Networks, Terminals and applications provider in North America.
  • Rohill Provider of TETRA Communication Systems under TetraNode brand
  • Sepura
    Sepura
    Sepura plc is the only major network-independent TETRA terminal supplier. It designs, develops and supplies digital radios for the public safety market as well as Military, Transport and Utilities...

    , manufacturer and supplier of TETRA terminals, Gateways and Repeaters.
  • Teltronic is a TETRA Networks, Terminals and applications manufacturer.
  • TETRAPOL
    TETRAPOL
    TETRAPOL is a digital professional mobile radio standard, as defined by the Tetrapol Publicly Available Specification , in use by professional user groups, such as public safety, military, industry and transportation organizations throughout the world....

     PMR standard which competes with TETRA for about every market.
  • UTOD GmbH is supplier of TETRA Communication Systems, including infrastructure, terminals and applications

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
x
OK