Katana VentraIP

TETRA

Terrestrial Trunked Radio[1] (TETRA; formerly known as Trans-European Trunked Radio), a European standard for a trunked radio system, is a professional mobile radio[2] and two-way transceiver specification. TETRA was specifically designed for use by government agencies, emergency services, (police forces, fire departments, ambulance) for public safety networks, rail transport staff for train radios, transport services and the military.[3] TETRA is the European version of trunked radio, similar to Project 25.

For other uses, see Tetra (disambiguation).

Company type

Incentive

European Telecommunications Standards Institute
professional mobile radio
trunked radio system

1995
Europe

Europe

TETRA is a European Telecommunications Standards Institute (ETSI) standard, first version published 1995; it is mentioned by the European Radiocommunications Committee (ERC).[4]

The Air Interface Encryption (AIE) keystream generator is vulnerable to decryption due to the use of publicly-broadcast network time[5]—keystream reuse can be triggered.[6]

oracle attacks

TEA1 contains a secret reduction step that effectively downgrades the cryptographic strength from 80 to 32 bits, allowing anyone to break the cipher and subsequently decrypt the signal in as little as one minute using a consumer laptop. "There's no other way in which this can function than that this is an intentional backdoor," "This constitutes a full break of the cipher, allowing for interception or manipulation of radio traffic", according to the news report posted on .[7] The deliberately weakened TEA1 flaw seems to be known in intelligence circles and is referred to in the famous 2006 Wikileaks dump of US diplomatic communications .

ComputerWeekly

AIE contains no for the ciphertext, making malleability attacks possible.[5]

authentication

The cryptographic anonymization scheme is weak and can be partially reversed to track users.

[5]

The authentication algorithm allows attackers to set the Derived Cypher Key (DCK) to 0, circumventing session authentication.[6]

[5]

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.

During a voice call, the communications are not interrupted when moving to another network site. This is a unique feature, which dPMR networks typically provide, that allows 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. A dedicated system isn't required in order to achieve this functionality, unlike with analogue radio systems.

transponder

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, and many-to-many. These operational modes are directly relevant to the public safety and professional users.

one-to-many

Security TETRA supports terminal registration, authentication, air-interface encryption and .

end-to-end encryption

Rapid deployment (transportable) network solutions are available for disaster relief and temporary capacity provision.

Network solutions are available in both reliable circuit-switched (telephone like) architectures and flat, IP architectures with soft (software) switches.

The main advantages of TETRA over other technologies (such as GSM) are:


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

Serious security issues have been identified, including an intentional weakening of the TEA1 cipher, constituting a full break within a minute on consumer hardware. (See )

Description

Requires a to meet the stringent RF specifications that allow it to exist alongside other radio services.

linear amplifier

Data transfer is slow by modern standards.

Its main disadvantages are:


Up to 7.2 kbit/s per timeslot, in the case of point-to-point connections, and 3.5 kbit/s per timeslot in case of IP encapsulation. Both options permit the use of between one and four timeslots. Different implementations include one of the previous connectivity capabilities, both, or none, and one timeslot or more. These rates are ostensibly faster than the competing technologies DMR, dPMR, and P25 are capable of. 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. To overcome the limitations many software vendors have begun to consider hybrid solutions where TETRA is used for critical signalling while large data synchronization and transfer of images and video is done over 3G / LTE.[8]

Technical details[edit]

Radio aspects[edit]

For its modulation TETRA, uses π⁄4 differential quadrature 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 sidebands, 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 using algebraic 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).

Man-machine interface (MMI)[edit]

Virtual MMI for terminals[edit]

Any given TETRA radio terminal using Java (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.


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:

TETRA: It is optimized for high population density areas, with spectral efficiency (4 time slots in 25 kHz: four communications channels per 25 kHz channel, an efficient use of spectrum). It is suitable for high population density areas and supports full duplex voice, data and messaging. but, it is generally unavailable for simulcast, VHF band - however particular vendors have introduced Simulcast and VHF into their TETRA platform..

P25: it is optimized for wider area coverage with low population density, and support for simulcast. however, it is limited to data support. (Phase 1 P25 radio systems operate in a 12.5 kHz analogue, digital or mixed mode, and P25 Phase II will use a 2-timeslot TDMA structure in 12.5 kHz channels.

Project 25 and TETRA are utilised for the public safety Radio network and Private Sector Radio network worldwide however, it has some differences in technical features and capacities.[18][19][20]


Currently, P25 deployed to more than 53 countries and TETRA deployed to more than 114 countries.

a TDMA digital radio standard from ETSI

Digital mobile radio

(dPMR), an FDMA digital radio standard from ETSI

Digital private mobile radio

a two-way FDMA digital radio protocol from Icom and JVC Kenwood

NXDN

(Project 25), a TIA APCO standard (USA)

P25

(previously MATRA)

TETRAPOL

prepared for the Home Office

Report on the health effects of TETRA

TETRA in use by radio amateurs

TETRA and Critical Communications Association (TCCA)

Radiocommunication objectives and requirements for Public Protection and Disaster Relief (PPDR)