Terrestrial Trunked Radio – China Machined Parts – Metal casting
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Description
The common mode of operation for them is in a group calling mode in which a single button push will connect the user to the users in a selected callgroup and/or a dispatcher. 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. If enabled by the Subscriber Management TETRA terminals can act as mobile phones (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, overriding any other activity taking place at the same time.
TETRA uses Time Division Multiple Access (TDMA) with four user channels on one radio carrier 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 or using Trunked infrastructure (Switching and Management Infrastructure or SwMI) made of TETRA Base Stations (TBS). As well as allowing direct communications in situations where network coverage is not available, Direct Mode or DMO also includes the possibility of using one (or a chain) of TETRA terminals as relays for a signal. This functionality is called DMO gateway (from DMO to TMO) or DMO Repeater (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 Data or Circuit switched data communication uses specifically assigned traffic channels.
TETRA provides Authentication Mechanisms of Terminals towards Infrastructure and vice versa. For protection against eavesdropping, over the air encryption and end-to-end encryption is available. 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 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 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 the cellular technologies, which connect one subscriber to one other subscriber (one-to-one) then TETRA is built to do one-to-one, one-to-many and many-to-many. These operational modes are directly relevant to the public safety and professional users.
TETRA supports both air-interface encryption and End-to-end encryption
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 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 to meet the stringent RF specifications that allow it to exist alongside other radio services.
handsets are more expensive than cellular (about 750 EUR in 2003, about 600 EUR in 2006). This is due to the more difficult technology, smaller economies of scale, and different business model (eg: need for security, high powers and robustness). However cheaper than main (PMR) *competitor technology APCO-16 where prices are >00 per handset. TETRA prices expected to fall further as far eastern manufacturers start production in 2007.
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 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. 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.
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. 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
The TETRA-system is in use by the public sector in the following countries
Continent
Country
Name
Agency
Status
Asia
Pakistan
Ministry of Interior
Police
In use Nationwide
India
Military College of Telecommunication Engineering (MCTE)
Indian Army
In use since 2004 at Mhow, Indore, Madhya Pradesh
AD100.
Kerala Police.
In use by police – Trivandrum city.
Taiwan
[]http://zh.wikipedia.org/wiki/
Taiwan Railways Administration,Railway Police Bureau
In use.
Israel
Mountain Rose.
Israel Defense Forces (IDF).
In use by IDF, country-wide.
Hong Kong
EADS TETRA Terminals
2008 Beijing Olympics and Paralympic Games (Hong Kong Equestrian Event)
Used from July 2008 to October 2008
Hong Kong Fire Services Department
Fire Service, Ambulance
In use.
Hong Kong Police Force
Police
In use.
Mass Transit Railway (MTR)
Transport
In use.
Hong Kong International Airport (HKIA)
Transport
Live from Feb 2009
Macao
Melco-Crown Entertainment
Casino-Hotels: Altira (formerly Crown Macau), and City of Dreams
In use since 2007.
Foras de Segurana de Macau
All Emergency Services
In use.
Africa
Sudan
Ministry of Interior
Police
In use Nationwide
Europe
Belgium
A.S.T.R.I.D
Austria
Police, Fire, Ambulance, Local Train Company
In use in all states except Tyrol and Vorarlberg (still roll-out)
Britain
Airwave
Police, Fire, Ambulance, Armed Forces, Highways Agency
In use by police all over the country.
Denmark
SINE
Police, Fire, Ambulance
Nationwide roll-out in progress
Ireland
TETRA Ireland
Garda, Fire, Ambulance, Defence Forces, Civil Defence, Security of State services
Nation-wide roll-out network
Italy
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)
Roll-out
Finland
VIRVE
Police, Fire, Ambulance, Customs, Defence Forces, Border guard
Nation-wide network
HelenNet
Helsingin Energia (One of the largest energy companies in Finland), Security guards (Mostly at shopping malls, train/metro stations and trams), Helsinki’s public transport
In use.
Estonia
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Police, Fire, Ambulance, Customs
Roll-out
Greece
C4I
Police, Fire, Coast Guard
Attica region
OTE
Airport, Metro, Security, Transportation, Taxi, Utilities, etc
Nation-wide Public Network
Latvia
Ventamonjaks Serviss Ltd, Ventspils Oil & Gas
In use since 2007.
Netherlands
C2000
Police, Fire, Ambulance
Nation-wide network
Norway
Ndnett
Police, Fire, Ambulance, Search and Rescue
Roll-out
Morocco
ADM
Highway authority
Roll-out
Sweden
RAKEL
Police, Fire
Roll-out
Portugal
SIRESP
Police, Fire, Ambulance
Nation-wide Roll-out in use since 2007
Romania
STS (Special Telecommunications Service)
Police, Fire, Search&Rescue
Nation-wide
Middle East
United Arab Emirates
Nedaa
Police, emergency services, professional communications
Dubai, Sharjah, Ajman, Umm Al-Qaiwain, Ras Al-Khaimah, Fujairah operational
Polikom
Police, emergency services, professional communications
Abu Dhabi Radio Frequencies
In South America, TETRA uses frequencies:
Emergency Systems
Number
Frequency Pair (MHz)
Band 1
Band 2
1
380-383
390-393
2
383-385
393-395
Civil