TETRA uses time-division multiple access (TDMA) with four user channels on one radio carrier and 25kHz 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 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 in which a single button push will connect the user to the users in a selected call group 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. 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.
An in-depth review published in July 2023 by the company Midnight Blue of the TETRA standard and encryption algorithms, the first made public in the last 20 years, has found multiple security flaws, collectively referred to as TETRA:BURST. A total of 5 flaws were filed to the CVE database:[5]
The Air Interface Encryption (AIE) keystream generator is vulnerable to decryption oracle attacks due to the use of publicly-broadcast network time[5]—keystream reuse can be triggered.[6]
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 ComputerWeekly.[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 [citation needed].
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,[5] circumventing session authentication.[6]
In addition, the Midnight Blue team spots a "peculiarity regarding the TEA3 S-box", but has yet to determine whether it constitutes a weakness.[6]
These vulnerabilities remained publicly unknown for 28 years after TETRA's publication because TETRA does not make definitions of its cryptographic algorithms public, an example of security through obscurity. The Midnight Blue team gained access to TETRA's cryptographic code by attacking the trusted execution environment on a TETRA-enabled radio. The team points to a list of previously broken cryptographic systems relying on obscurity and argues that the Kerckhoffs's principle should have been followed: the system would have been safer when its structure is publicly known.[6]
Advantages
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.
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 transponder system isn't required in order to achieve this functionality, unlike with analogue radio systems.
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. These operational modes are directly relevant to the public safety and professional users.
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.
Further information is available from the TETRA Association (formerly TETRA MoU) and the standards can be downloaded for free from ETSI.
Disadvantages
Its main disadvantages are:
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 linear amplifier to meet the stringent RF specifications that allow it to exist alongside other radio services.
Data transfer is slow by modern standards.
Up to 7.2kbit/s per timeslot, in the case of point-to-point connections, and 3.5kbit/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 115.2kbit/s in 25kHz or up to 691.2kbit/s in an expanded 150kHz 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
Radio aspects
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 36,000bit/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 3.65dB. 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 8kHz and then compressed with a vocoder using algebraic code-excited linear prediction (ACELP). This creates a data stream of 4.567kbit/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 7.2kbit/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 17Hz 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).
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, TEA1 up to TEA4. These TEA ciphers should not be confused with the block cipher Tiny Encryption Algorithm. The TEA ciphers have different availability due to export and use restrictions. Few details are published concerning these proprietary ciphers. Riess[12] mentions in early TETRA design documents that encryption should be done with a stream cipher, due to the property of not propagating transmission errors. Parkinson[13] later confirms this and explains that TEA is a stream cipher with 80-bit keys. The algorithms were later reversed and it appeared that TEA1 reduces its key strength to 32 bits.[14] TEA1 and TEA4 provide basic level security, and are meant for commercial use.[15] The TEA2 cipher is restricted to European public safety organisations. The TEA3 cipher is for situations where TEA2 is suitable but not available.[16]
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.
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
Cell initial 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 mobile station (MS) 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
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
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, for a period of 5 seconds, greater than the fast reselect threshold plus the fast reselect threshold, 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)
Cell relinquishable
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 Mobility Management (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.
Radio down-link failure
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 −105dBm. Cell reselection procedures are then activated in order to find a suitable radio base station.
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:
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:
Service acquisition,
Status SDS,
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 440Hz 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) 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 (880Hz), 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 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 and the hash keys for the fraud and aggression quick keys respectively. For the fraud and aggression tones, it is also recommend to use 440Hz slow repeating tone (blank space 500 milli-seconds) and 880Hz fast repeating tone (blank space 250 milliseconds) respectively. The tone options are as follows: 440Hz, 620Hz, 880Hz, and 1060Hz.
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.
TETRA Enhanced Data Service (TEDS)
The TETRA Association, working with ETSI, developed the TEDS standard, a wideband data solution, which enhances TETRA with a much higher capacity and throughput for data. In addition to those provided by TETRA, TEDS uses a range of adaptive modulation schemes and a number of different carrier sizes from 25kHz to 150kHz. Initial implementations of TEDS will be in the existing TETRA radio spectrum, and will likely employ 50kHz channel bandwidths as this enables an equivalent coverage footprint for voice and TEDS services. TEDS performance is optimised for wideband data rates, wide area coverage and spectrum efficiency.[17]
Advances in DSP technology have led to the introduction of multi-carrier transmission standards employing QAM modulation. WiMAX, Wi-Fi and TEDS standards are part of this family.
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]
TETRA: It is optimized for high population density areas, with spectral efficiency (4 time slots in 25kHz: four communications channels per 25kHz 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 12.5kHz analogue, digital or mixed mode, and P25 Phase II will use a 2-timeslot TDMA structure in 12.5kHz channels.
Currently, P25 deployed to more than 53 countries and TETRA deployed to more than 114 countries.
Usage
At the end of 2009[update] there were 114 countries using TETRA systems in Europe, Middle East, Africa, Asia Pacific, Caribbean and Latin America.[21]
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 of suppliers.
Police, fire, ambulance, customs, defence forces, and border guard
Nationwide network
HelenNet
Energy company Helsingin Energia, tram operator HKL-Raitioliikenne, 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.
Business critical, public protection & disaster relief (PPDR) communications, public utility and oil-gas companies, seaports, airports, public and private transportation companies, public and private sector security personnel, other. Data applications nationwide including SCADA, AVL, M2M.
Extensive nationwide footprint, 70% population coverage in 2014, in use since 2002
SEPURA
Teltronic
Police, Fire Services, Coast Guard
Nationwide roll-out in progress.
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
Police, fire services, ambulances, Search and Rescue units, Red Cross, bus service (Strætó Bs.), The Icelandic National Broadcasting Service, most utility companies, municipalities and private users such as excursion companies.
An Garda Siochana, HSE National Ambulance Service, Irish Prison Service, Irish Naval Service, Customs & Excise, civil defense (only a few units), Irish Coast Guard, mountain rescue (only a few units), Order of Malta Ambulance Corps, Irish Red Cross, St John Ambulance, National Emergency Office, Port of Cork, Revenue Commissioners and Office of Public Works.
Nationwide roll-out network complete. The fire services are planning to implement in the coming years. As of July 2011, TETRA Ireland now operates the national Paging System.
Polizia di Stato (Italian state police), Carabinieri (military police), Guardia di Finanza (financial police), Polizia Penitenziaria (prison police), and Corpo Forestale Italiano (Italian forest brigades)
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
Hytera/Motorola/Sepura
HamTetra Network Romania
Amateur radio users engage in both DMO (Direct Mode Operation) and TMO (Trunked Mode Operation) modes, both within the country and globally, connecting through gateways such as Zello and SVXLink.
Ham Tetra Romania Network Architecture was developed and published along with users map and equipment used on the YO8TEH website
Tetra gear in ham radio was initially introduced by YO8TEH in 2014 in DMO (Direct Mode Operation). Subsequently, it evolved into gateways through platforms like Zello and Teamspeak. In 2021, a part of the system was split and migrated to svxlink, along with its classic application. The first Tetra Repeater for Ham Radio use in Romania was licensed under the call sign YO8TEH-1, while the second TMO repeater was licensed under the call sign YO8Q.
Russia
DAMM TetraFlex
Moscow Metro (second most heavily used rapid transport system in the world)
Transport - rail - telemetry, safety, security, police, ambulance, fire
Government - ambulance and emergency services, police, healthcare facilities, utility services, St. Petersburg Authorities and the regional civil defense
Police, fire brigades, civil protection, ambulances, forest guards, water agency, gas company, road maintenance service and other public agencies
In use since 2006
Sweden
SAAB, Cassidian, Eltel Networks
RAKEL
Managed by the Civil Contingencies Agency - MSB. For use by the emergency services and others in the fields of civil protection, public safety and security, emergency medical services and healthcare, road services, nuclear facilities.
In operation, covering 99.8% of Sweden's population and 95% of its territory
Motorola
Tetra
Stockholm public transport: used by transport security officers for dispatch internal communications, Transport Police ("Tunnelbanepolisen") and other police forces for liaison with transport officials. Roll-out stage for train operations on underground.
Ministry of Interior, army, police, air force search and rescue, EMS (medical).
Initial use for the 15th Asian Games all games venues inclusive of transportation routes for "blue light" services, later extended to cover the State of Qatar, in use since 2006, national roll out complete by 2008. Known as Qatar Secure TETRA Radio System (QSTRS).
911: technical and power systems support communication, operations and dispatching, service agencies communication systems (police, Public health, firefighters, traffic control authority, road support).
Metro: First line operation started in 2008. 2nd line operation started 2013. 2nd line expansion (L2B) started in 2014 and started operation on August 8, 2018.
911: Operation started in 2014 in Santo Domingo, with expansions in 2015. In 2016, TETRA trunking radio expanded to Haina and San Cristobal, cities in the southwest of Santo Domingo. In 2017, the service expansion of 911 services using TETRA expanded to the north of the country, to cover large cities as Santiago, Puerto Plata and small villages. On August 3, 2018, service expanded to the province Peravia (West to the Capital) and on August 28, 2018, it started in the province of San Pedro de Macoris ( East to the capital).
Digital Enhanced Cordless Telecommunications (DECT) is a cordless telephony standard maintained by ETSI. It originated in Europe, where it is the common standard, replacing earlier standards, such as CT1 and CT2. Since the DECT-2020 standard, it also includes IoT communication.
The Global System for Mobile Communications (GSM) is a standard developed by the European Telecommunications Standards Institute (ETSI) to describe the protocols for second-generation (2G) digital cellular networks used by mobile devices such as mobile phones and tablets. GSM is also a trade mark owned by the GSM Association. GSM may also refer to the Full Rate voice codec.
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, one after the other, each using its own time slot. This allows multiple stations to share the same transmission medium while using only a part of its channel capacity. Dynamic TDMA is a TDMA variant that dynamically reserves a variable number of time slots in each frame to variable bit-rate data streams, based on the traffic demand of each data stream.
Wireless communication is the transfer of information (telecommunication) between two or more points without the use of an electrical conductor, optical fiber or other continuous guided medium for the transfer. The most common wireless technologies use radio waves. With radio waves, intended distances can be short, such as a few meters for Bluetooth or as far as millions of kilometers for deep-space radio communications. It encompasses various types of fixed, mobile, and portable applications, including two-way radios, cellular telephones, personal digital assistants (PDAs), and wireless networking. Other examples of applications of radio wireless technology include GPS units, garage door openers, wireless computer mouse, keyboards and headsets, headphones, radio receivers, satellite television, broadcast television and cordless telephones. Somewhat less common methods of achieving wireless communications involve other electromagnetic phenomena, such as light and magnetic or electric fields, or the use of sound.
A SIMcard is an integrated circuit (IC) intended to securely store an international mobile subscriber identity (IMSI) number and its related key, which are used to identify and authenticate subscribers on mobile telephone devices. Technically the actual physical card is known as a universal integrated circuit card (UICC); this smart card is usually made of PVC with embedded contacts and semiconductors, with the SIM as its primary component. In practice the term "SIM card" is still used to refer to the entire unit and not simply the IC.
IS-54 and IS-136 are second-generation (2G) mobile phone systems, known as Digital AMPS (D-AMPS), and most often referred to as TDMA, are a further development of the North American 1G mobile system Advanced Mobile Phone System (AMPS). It was once prevalent throughout the Americas, particularly in the United States and Canada since the first commercial network was deployed in 1993. D-AMPS is considered end-of-life, and existing networks have mostly been replaced by GSM/GPRS or CDMA2000 technologies.
The Government Radio Network (GRN) is a network of various systems in place across Australia that enable statewide trunked radio communication. The network operates through inter-linked sites for government and public services such as police, ambulance, fire, or roads authorities which require such a system to function properly. The main aim of the GRN is to consolidate all resources into one network, ensuring greater coverage and reliability than if each department had its own independent communication system. The existence of the GRN also reduces the amount of government money and resources needed to maintain communication between units of emergency and public service branches. Last, it allows effective intercommunication among these services in times of national or state emergency for coordination of wide-scale actions.
Professional mobile radio are person-to-person two-way radio voice communications systems which use portable, mobile, base station, and dispatch console radios. PMR systems are based on such standards as MPT-1327, TETRA, APCO 25, and DMR which are designed for dedicated use by specific organizations, or standards such as NXDN intended for general commercial use. These systems are used by police, fire, ambulance, and emergency services, and by commercial firms such as taxis and delivery services. Most systems are half-duplex, in which multiple radios share a common radio channel, and only one can transmit at a time. Transceivers are normally in receive mode, the user presses a push-to-talk button on his microphone when he wants to talk, which turns on his transmitter and turns off his receiver. They use channels in the VHF and UHF bands, giving them a limited range, usually 3 to 20 miles depending on terrain. Output power is typically limited to 4 watts. Repeaters installed on tall buildings, hills or mountain peaks are used to increase the range of systems.
Project 25 is a suite of standards for interoperable digital two-way radio products. P25 was developed by public safety professionals in North America and has gained acceptance for public safety, security, public service, and commercial applications worldwide. P25 radios are a direct replacement for analog UHF radios, but add the ability to transfer data as well as voice, allowing for more natural implementations of encryption and text messaging. P25 radios are commonly implemented by dispatch organizations, such as police, fire, ambulance and emergency rescue service, using vehicle-mounted radios combined with repeaters and handheld walkie-talkie use.
The Secure Communications Interoperability Protocol (SCIP) is a US standard for secure voice and data communication, for circuit-switched one-to-one connections, not packet-switched networks. SCIP derived from the US Government Future Narrowband Digital Terminal (FNBDT) project. SCIP supports a number of different modes, including national and multinational modes which employ different cryptography. Many nations and industries develop SCIP devices to support the multinational and national modes of SCIP.
Spectral efficiency, spectrum efficiency or bandwidth efficiency refers to the information rate that can be transmitted over a given bandwidth in a specific communication system. It is a measure of how efficiently a limited frequency spectrum is utilized by the physical layer protocol, and sometimes by the medium access control.
E-UTRA is the air interface of 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) upgrade path for mobile networks. It is an acronym for Evolved UMTS Terrestrial Radio Access, also known as the Evolved Universal Terrestrial Radio Access in early drafts of the 3GPP LTE specification. E-UTRAN is the combination of E-UTRA, user equipment (UE), and a Node B.
TETRAPOL (Terrestrial Trunked Radio POLice) is a digital professional mobile radio standard, as defined by the Tetrapol Publicly Available Specification (PAS), in use by professional user groups, such as public safety, military, industry and transportation organizations throughout the world. Airbus Defence and Space is the main supplier of this technology.
MPT 1327 is an industry standard for trunked radio communications networks.
For telephone services to mobile phones, Hierarchical cell structure ("HCS") used in mobile telecommunication means the splitting of cells. This type of cell structure allows the network to effectively use the geographical area and serve an increasing population.
The Universal Mobile Telecommunications System (UMTS) is one of the new ‘third generation’ 3G mobile cellular communication systems. UMTS builds on the success of the ‘second generation’ GSM system. One of the factors in the success of GSM has been its security features. New services introduced in UMTS require new security features to protect them. In addition, certain real and perceived shortcomings of GSM security need to be addressed in UMTS.
NXDN stands for Next Generation Digital Narrowband, and is an open standard for public land mobile radio systems; that is, systems of two-way radios (transceivers) for bidirectional person-to-person voice communication. It was developed jointly by Icom Incorporated and Kenwood Corporation as an advanced digital system using FSK modulation that supports encrypted transmission and data as well as voice transmission. Like other land mobile systems, NXDN systems use the VHF and UHF frequency bands. It is also used as a niche mode in amateur radio.
Digital mobile radio (DMR) is a digital radio standard for voice and data transmission in non-public radio networks. It was created by the European Telecommunications Standards Institute (ETSI), and is designed to be low-cost and easy to use. DMR, along with P25 phase II and NXDN are the main competitor technologies in achieving 6.25 kHz equivalent bandwidth using the proprietary AMBE+2 vocoder. DMR and P25 II both use two-slot TDMA in a 12.5 kHz channel, while NXDN uses discrete 6.25 kHz channels using frequency division and TETRA uses a four-slot TDMA in a 25 kHz channel.
The Norwegian Public Safety Network is a public safety network system based on Terrestrial Trunked Radio (TETRA). Nødnett is implemented by the Directorate for Emergency Communication. The network is primarily used for internal and interdisciplinary communication by the police, fire departments and health services. Nødnett is also used by several organisations participating in rescue and emergency work. Planning of the network started in 1995 and in 2006 the contract to build it was awarded to Nokia Siemens Networks. As Nokia Siemens Networks was unable to complete the contract, it was passed on to Motorola Solutions in 2012. The critical infrastructure of Nødnett was finished and was operational in all districts of mainland Norway by December 1, 2015.
M17 is a digital radio modulation mode developed by Wojciech Kaczmarski et al. M17 is primarily designed for voice communications on the VHF amateur radio bands, and above. The project received a grant from the Amateur Radio Digital Communications in 2021 and 2022. The protocol has been integrated into several hardware and software projects. In 2021, Kaczmarski received the ARRL Technical Innovation Award for developing an open-source digital radio communication protocol, leading to further advancements in amateur radio.
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