iDEN subscriber terminals, like the GSM system, use SIM cards. In terms of interconnection, GSM signaling control algorithms are used, which greatly simplifies roaming with cellular networks. Professional (industrial) terminals (R370, R470, R765, R765IS) and commercial “i” series are produced. There are dual mode models iDEN/GSM, iDEN/CDMA. Some terminals have the “Direct Connect” function, which allows you to connect network subscribers directly, bypassing base stations, in local areas in the SMR (Specialized Mobile Radio) frequency range 800 MHz. Currently, two companies Motorola and RIM are engaged in the production of terminals. In 2010, an Android terminal was presented with touch screen i1.
It's a miracle - it works like a radio.
In 2005, a further development of the standard was introduced, which allows, by combining the time slots of four physical channels, to obtain a data transfer rate of up to 100 kBit/s. The upgrade is called WiDEN (Wideband Integrated Digital Enhanced Network).
As of 2010, along with systems
Ministry of the Russian Federation for Communications and Informatization.
Siberian State University
telecommunications and computer science.
Report on the topic:
"Trunking communication systems"
Completed
Student gr. M-81
Mikhailova O.I.
Checked
Burov P.N.
Novosibirsk 2001
Content.
1.Use of trunking radiotelephone communication systems.
2.Principles of building trunking systems.
a) Turning on the radiotelephone communication network as a UPBX.
b). Turning on the trunking communication network as a RATS subscriber.
V). Enabling a trunking communication network as a RATS.
3. Use of radio frequencies.
4. Conclusion.
5. List of references.
APPLICATION OF TRUNKING RADIOTELEPHONE COMMUNICATION SYSTEMS ON THE FEDERAL INTERCONNECTED COMMUNICATION NETWORK OF RUSSIA.
Today in Russia, two types of mobile communication networks (MCNs) are most widespread - tracking radiotelephone communication networks and cellular mobile communication networks. Trafficbook networks are built on the basis of the MPT1327, Smar frank P (Germany) standards, cellular networks are based on the GSM, DSC1800 (European countries), NMT-450 (Nordic countries), AMPS (USA), HCMTS (Japan), TACS (UK) standards ), etc.
The term "trunking" ("tmnking") means automatic distribution of channels (ARC) and provision of users with any radio channel from among the free ones. The ARC method makes it possible to effectively use radio channels and thereby significantly reduce their congestion. This is especially necessary in areas with a large schedule, where the ARC method allows you to increase, without any losses, the throughput of each radio channel.
In radio systems of the "Trunking" type, several radio channels are used simultaneously. Each subscriber of the system can be provided with any of the free channels for communication. All radio channels are connected common system management. It monitors their status and immediately provides available channels to the next subscribers. That is why in the Trunking system the probability of denial of service is much lower than in a single-channel system with one repeater. For a single-channel system, the number of subscribers should not exceed 30. A four-channel system allows servicing, according to various estimates, from 40 to 80 subscribers per channel, i.e. up to 300 users. When the number of channels is less than four, the “Trunking” type system does not yet demonstrate its full inherent efficiency. That is why for a system with two or three channels you need to assume an average load of 30...50 subscribers.
Principles of constructing trunking systems.
Initially, trunking systems were intended for departmental use as part of dedicated networks and did not have access to the public telephone network (PSTN). Over time, these systems received a slightly different development and began to be used to organize commercial networks.
Trunking networks make it possible to combine network subscribers into groups and, thus, the main load (80...90%) is distributed within the network, since subscribers of these groups - employees of ambulance services, fire departments, city organizations, etc. - either have limited access to PSTN, or do not have it at all. Along with groups of users, individual mobile subscribers can also be connected to the network, having the ability to access local, long-distance and international communication networks. This structure opens up the possibility of “commercialization” of departmental networks.
As is known, the federal mobile network cellular communications Russia is built on the basis of international standards systems adopted in most European countries - NMT-450 and GSM. In addition to the basic services provided to subscribers of cellular networks, their main feature is the possibility of organizing automatic national and international roaming- servicing subscribers of one network in another similar network. Trunking communication networks operate only at the regional level, i.e. they serve mobile and fixed subscribers within the boundaries of regions (long-distance zones); such inclusion of networks in the PSTN will be carried out at the local level since, unlike cellular networks, trapping networks generally do not have the possibility of roaming.
Trunking networks are built in accordance with two principles - radial and zonal. The first provides for communication within the coverage area of the central (base) station, the second - within the coverage of several base (area) stations (BS). Base stations are located in a specific region and are connected to a single switching center by bundles of trunk lines. These principles of network construction cannot always guarantee continuous communication when moving from one zone to another within the range of several BS (the so-called function handover). A simplified classification of terrestrial mobile networks in the Russian Federation is presented in Fig. 1.
The structure of the trunking network is shown in Fig. 2. Radio communication is carried out through BS, which are connected to a radio channel controller (RC), which provides control of one radio channel [when managing several radio channels, a trunking controller (TC) is used], performance of all system functions and operation of interfaces with BS, control panels, PSTN and others In the case of building a large network covering a large area, several control centers and one central system controller (CSC) are used, which combines several control centers and serves as a common switching and control center for the network, while switching and control in each individual zone, including the output, remain possible. on the PSTN. In addition, the CCS allows you to organize centralized maintenance of the trunking network. Communication between stationary and mobile subscribers (UA) is carried out through a network that includes the CD and CCS.
Connecting a trunking network to the PSTN.
The first mobile radio communication systems appeared in the USA in the late 30s. These were single-channel conventional systems intended primarily for radio communications in the police and army. During World War II the first multi-channel systems with "manual" channel switching.
A significant drawback of conventional systems is their vulnerability to unauthorized use of frequency resources. Any radio amateur knowledgeable in radio engineering is able to assemble a device to tune to the frequencies used by a given system and thus become an unauthorized user. In addition, in these systems it is not easy to disconnect subscribers who create excessive load with endless non-business “conversations”. The connection of subscriber terminals with the public telephone network (PSTN) is not implemented in all conventional systems.
The main idea of trunking communication is that when a subscriber receives a request to establish a connection, the system automatically detects free channels and assigns one of them to a given pair or group of subscribers. Partially, the problem of automating channel selection was solved in the so-called pseudo-trunking systems, which include the popular SmarTrunk/SmarTrunk II in Russia from SmarTrunk System and ArcNet from Motorola. Their radio stations do not have a dedicated control channel and scan a dedicated frequency range in search of a free one. Most of these systems (with the exception of ArcNet) are single-zone.
At the end of the 70s. The radio communications market was replenished with the first analog trunking systems with a dedicated control channel. Such systems implement the transmission of speech information according to the principle of “one channel - one carrier”; the frequency spacing of the channels is usually 25 or 12.5 kHz. Theoretically, with a sufficient number of frequency channels, they are capable of serving tens of thousands of subscribers. However, the actual values of the allocated frequency resource limit the number of analog trunking network subscribers to 3-5 thousand.
In addition, these systems still do not solve the problem of protecting the network from unauthorized access. Systems based on analog standards provide communication with PSTN subscriber terminals, but such terminals are very expensive ($1500-2000). A significant drawback of these systems is also the limited number of user groups. And although the implementation of the function of dynamic reconfiguration of groups allows you to circumvent this limitation, the game is not always worth the trouble: the complexity of the equipment leads to a significant increase in the cost of infrastructure.
In the early 90s. Trunking systems using digital technologies for voice signal transmission began to appear. Today, the most famous digital standards are APCO25, TETRA and PRISM (digital version of EDACS). They allow you to significantly increase the system capacity - up to several thousand subscribers. In addition, they practically solve the problem of data protection and confidentiality of conversations, since it is impossible to become an unauthorized user of a digital system or listen to a channel.
Many modern trunking communication systems (Fig. 1) - both analog and digital - are capable of transmitting data over a voice communication channel, i.e., performing the functions of a wireless modem. At the same time, in analog standards the data transfer rate does not exceed 4800 bps, and in digital standards it reaches higher values - from 9600 bps to 28 kbps (TETRA). Unlike analogue ones, digital trunking communication systems allow text messages to be transmitted through control channels (paging). The text of the message is displayed on the display of the subscriber terminal.
Currently, three different areas of application of mobile radio communication systems can be distinguished: government (police, fire, ambulance, etc.); - type PS (Public Safety); private, such as PMR (Private Mobile Radio); commercial public networks SMR (Shared Mobile Radio).
Figure 1.
Technologies mobile communications(* TDMA based technologies)
Systems of the first type are usually designed for a relatively small number of subscribers (usually no more than 500-1000). They are characterized by increased requirements for reliability and confidentiality, as well as the presence of special functions like Emergency Call. The cost of subscriber terminals of PS systems is quite high. Of the previously mentioned networks, the Public Safety/PMR category includes SmartNet, EDACS/PRISM, systems based on the APCO25 standard, as well as networks based on the currently developed digital TETRA standard.
Commercial systems such as SMR are distinguished by large capacity (the number of subscribers can reach tens of thousands), the ability to provide additional information services, as well as the moderate cost of subscriber terminals. Among them are networks built on the basis of SmartZone, MPT1327, LTR/ESAS protocols and the GeoNet system. Note that most existing analog SMR systems have limitations on frequency reuse and channel switching, as well as automatic identification of subscribers when they move from one zone to another, etc.
In contrast to conventional and trunked radio communication systems, mobile telephone cellular communications are intended primarily to provide one-to-one personal mobile voice communication in full duplex mode. The first generation of cellular technology, which appeared in the early 1980s, used analog standards. The most widely used in the world (including Russia) are the North American AMPS standard, the British TACS and the Scandinavian NMT-450.
The use of digital technologies has made it possible to understand that two different types mobile voice communications - cellular and trunking - have much in common (territorial organization of the system, infrastructure, organization of access to the PSTN, etc.). However, analog technologies of trunking systems are unable to provide the level of service provided by mobile telephony.
In the mid-90s. Motorola decided to implement the idea of an integrated system that combines the capabilities of group and dispatch radio communications, mobile cellular telephone communications, as well as the transmission of alphanumeric messages (paging) and data. The proposed system was supposed to provide a modern level of service for all types of communications. All this was implemented in iDEN (integrated Digital Enhanced Network) technology.
System services
Mobile dispatch radio communication based on iDEN technology provides all types of services provided by modern digital trunking systems:
- group call for mobile subscribers and dispatchers in half-duplex communication mode. To make a call, just one click of a button is enough; connection establishment time does not exceed 0.5 s. In this case, only one voice communication channel is used - regardless of the number of subscribers in the group. The number of possible groups in iDEN is quite large (65,535), which eliminates the need for dynamic group reconfiguration functionality. All configurations can be created in advance: if necessary, subscribers simply move to the appropriate groups. Group members can be located at a distance of tens or hundreds of kilometers from each other (of course, within the system’s coverage area);
- personal call (private call) in half-duplex mode, when only two subscribers participate in the conversation and complete confidentiality of negotiations is ensured. Note that in the group and individual call mode, the caller's name or his digital identifier appears on the display of the subscriber terminal of the called subscriber;
- call signaling (call alert) - transmission of a special signal to a subscriber (or group), indicating the need to establish radio communication. If at this moment the subscriber is outside the system area or the subscriber terminal is turned off, the call is stored in the system. The moment the subscriber becomes available, he receives beep, and the caller ID appears on the terminal screen. Only then does the caller receive confirmation of the call.
In addition to the services typical for conventional trunked communications, the iDEN system provides a number of capabilities of modern mobile telephone systems:
- mobile telephone communication between subscribers, including via PSTN (both incoming and outgoing in duplex mode). The iDEN system provides local telephony functions (mini-PBX, PABX) voicemail(voice mail), long-distance and international communications;
- transmission text messages. Subscribers can receive alphanumeric messages displayed on the user terminal screen, which can store up to 16 messages of 140 characters each. This provides both group and individual messaging. Receiving text messages is possible simultaneously with a mobile telephone session;
- data transfer. Portable (wearable) iDEN terminals have built-in modems and can be connected to a PC via an RS-232C adapter. In circuit switching mode, data transfer rates of up to 9600 bps are provided, and in packet mode - up to 64 kbps. To increase the reliability of data transmission, the system uses a forward error correction scheme. The data function allows mobile subscribers to receive and send fax messages and email, exchange data with office computers and provide access to the Internet. In packet mode, the standard TCP/IP network protocol is supported.
Note that adding a data transfer function to the existing iDEN system does not require the installation of additional equipment at base stations (BS). It is only necessary to install additional blocks of the central system management infrastructure and install the corresponding software on the base stations and the central system.
User terminals
Although the iDEN system provides several types of communications, this does not mean that the subscriber needs to “subscribe” to all types of services and, accordingly, purchase a fully functional subscriber terminal from the operator. The user can always choose a model that matches the package of services he is interested in. The cost of iDEN portable subscriber terminals and digital cell phones is approximately the same.
The i370/r370 portable terminals are capable of operating both as trunking radios and as mobile phones. They are equipped with a multi-line LCD display, which displays lists of available groups (subscribers) and alphanumeric messages. The improved i600 multifunction terminal is smaller, lighter and has longer battery life.
The latest model of the i1000 portable terminal has an even smaller weight and size: its weight without batteries is 120 g, dimensions are 120x60x30 mm.
The i470/r470 models are equipped with a built-in modem, which allows them to be used for data transfer and fax messages. In addition, these terminals support additional features iDEN systems, such as simultaneous work in several groups, providing communication in isolated BS mode (in case of communication failure with the central infrastructure of the system), Emergency Call, etc.
Models r370 and 470, meeting the requirements of US military standards, have a shock-resistant body and are not afraid of moisture. The signal output power of all types of portable terminals is 600 mW.
The iDEN family of mobile subscriber terminals consists of three models - m100, m370 and m470. The first one works only in dispatch radio mode, the other two are equipped with a handset and support mobile telephone communications. In addition, the m470 model has a built-in modem and provides the same special functions, as i470/r470 terminals. All types of mobile terminals have output power 3 W.
The iDEN system also provides desktop dispatch stations based on m100/m370/m470 mobile terminals. They have an external antenna, a table microphone and an AC power supply.
Radio interface and voice coding
The basis of iDEN technology is the TDMA (Time Division Multiple Access) standard, according to which 6 digitized speech signals are simultaneously transmitted over each 25 kHz frequency channel. iDEN technology does not require all frequency channels to be contiguous.
The 90 ms time interval is divided into 6 time slots of 15 ms duration, each of which carries one voice signal (Fig. 2). The use of radio signal modulation using the M16-QAM (Quadrature Amplitude Modulation) method provides a total data transfer rate over one frequency channel of 64 kbit/s (transmission speed in the voice channel is 7.2 kbit/s). Adequate reproduction of the human voice and other sounds at such a low bit rate is achieved through the use of an advanced encoding scheme using the VSELP algorithm.
Figure 2.
iDEN frequency channel capacity
Frequency range
The system based on iDEN technology operates in the trunking range 806-825/851-870 MHz, standard for America and Asia. Note that recently in Russia, part of this range, namely 815-820/860-865 MHz, has also been allocated for trunking radio communication systems (Fig. 3).
Figure 3.
Frequency range allocated for the iDEN system in Russia: mobile terminals (MT) 806-821 MHz; base stations (BS) 851-866 MHz
When developing iDEN technology, Motorola wanted to achieve the most efficient use of frequency resources, at least as good as existing implementations of the CDMA standard. Since iDEN provides simultaneous transmission of six speech signals on each 25 kHz frequency channel, 240 such channels can be accommodated in 1 MHz of spectrum. For comparison, with a bandwidth of 1 MHz, analog and digital trunking communication systems can support no more than 80, analog cellular communication systems - from 30 to 40, and systems in the GSM standard - 40 voice channels (Fig. 4).
Figure 4.
Comparison of spectrum efficiency. In 1 MHz of spectrum you can place voice channels (GC): analog trunking systems - 40/80; analog cellular systems - 33-40; GSM - 40; TETRA - 160; iDEN - 240
iDEN system structure
The system based on iDEN technology consists of two main components: the BS and the central infrastructure. (Fig. 5). The iDEN infrastructure is organized to maximize the functionality of the BS, so the most important functional element is the EBTS Enhanced Base Transceiver System base station. EBTS includes an integrated node controller (iSC), up to 20 base radio stations (BR) of the omni type or 24 sector BRs, an amplifier and radio signal transmitters, a synchronizing receiver, and BS antennas.
Figure 5.
System structure based on iDEN technology: * provides telephone communication; ** provide radio communication; *** provided by the system operator; DACS (Digital Access Crossconnect Switch) - digital access switch; IWF (Interworking Function) - data transfer interface with PSTN; VMS (Voice Mail System) - voice mail
EBTS provides interaction between the system and subscriber devices, supports the transmission of voice traffic on several frequency channels, and also performs a whole series control functions, for example, separation of radio and telephone traffic, synchronization of the operation of the BS and subscriber terminals, control of the radio signal level, etc. The multifunctionality of EBTS can significantly reduce the load on the components of the central infrastructure, primarily on the MSC (Mobile Switching Center). The EBTS transmitter supports a maximum of 144 voice channels per system node.
The main function of the BSC (Base Site Controller) is to control communications when moving subscriber terminals from one coverage area to another (handover). Each BSC is capable of supporting up to 30 zones, performing the full range of actions to concentrate traffic coming from hub stations and distribute it to the appropriate zones.
The XCDR transcoder performs forward and reverse conversion of VSELP audio to PCM digital format.
The MPS (Metro Packet Switch) packet switch consists of a switch and a packet duplicator. It transmits dispatch radio voice packets and control information from the EBTS to the DAP and back.
The DAP (Dispatch Application Processor) dispatch system performs group and personal call management, call signaling and other functions. With a large number of system subscribers, it is possible to create clusters of four DAPs.
Subscriber location registration blocks HLR/VLR (Home Location Register)/Visited Location Register) serve mobile telephone communications. The HLR stores complete information about all subscriber terminals registered in various geographical segments of the system. The VLR contains information about the movement of subscriber devices and provides the system with the information necessary to perform roaming. Note that in the iDEN system there is no roaming in the sense in which it is understood in cellular systems, since not PSTN, but dedicated E1 channels are used to connect geographically distant segments of the system.
The MSC (Mobile Switching Center) switch provides the interface between the PSTN and iDEN mobile phones, performing the typical functions of such a switch, and also manages the transmission when subscribers move from an area controlled by one BSC to an area controlled by another. If the iDEN network covers a large area, several MSCs may be installed in it. The functions of the MSC of the iDEN system are completely identical to the functions of a GSM cellular network switch.
The main control module of the system is OMC (Operation Maitenance Center), which provides system configuration, emergency management, collection of statistical data on system operation and a number of other management functions.
Short service SMS messages(Short Message Service) supports all text messaging functions, including text notifications when messages are available for of this subscriber(voice mail).
iDEN MicroLite
Motorola is currently finalizing the development of the iDEN MicroLite system, which is a “small” iDEN-based system designed to serve hundreds to several thousand subscribers. While maintaining all iDEN technological solutions, using the same subscriber equipment and base stations, this system differs, first of all, in the maximum number of frequency channels (40 of them).
The main technological difference between iDEN MicroLite and iDEN is the organization of the central infrastructure of the system. In the iDEN MicroLite system, it is implemented on a single computer platform of the Compact PCI standard (a variant of the PCI platform for industrial computers), running the Neutrino real-time OS from QNX Labs.
The first version of iDEN MicroLite will provide two types of communication - group (individual) radio communication and mobile telephone communication. Future versions will add short message and dial-up/packet data services to the system. The maximum number of base stations that the central infrastructure of the first version of the system can support is 5; in the future it will be increased to 8-10.
If it is necessary to switch from iDEN MicroLite to complete system iDEN required new installation central infrastructure of the system, however, by modifying the appropriate software, you can use subscriber terminals and existing BS equipment.
Deliveries of the iDEN MicroLite system will begin in the second quarter of 1999. Technical development of iDEN MicroLite system projects is expected from the third quarter of 1998.
Applications for iDEN
iDEN technology is focused on creating SMR (Shared Mobile Radio) type systems, i.e. commercial networks that provide integrated services to organizations and individuals. To ensure communication between individual departments and groups of employees, a so-called “fleet” is created for each corporate user of the system - a virtual private network within the organization’s network. Different groups can be created within the fleet, corresponding to the company's divisions (the maximum number of groups in one fleet is 255). The possibility of accidental or deliberate intrusion of subscribers into foreign fleets is absolutely excluded. Fleet members can be located in different geographic regions and move from one city to another.
Thus, an organization can build its own mobile telecommunications system that is fully equivalent to the organization's network. At the same time, she does not need to purchase equipment and build antennas, and also spend several months installing and debugging the system. All you need to do is become a corporate user already existing system iDEN.
Where and when
The first commercial system based on iDEN technology, deployed in the United States by NEXTEL in mid-1994, is now nationwide. It has about 4,500 BS and about 2 million subscribers. In the southwestern states of the United States, there is another network based on iDEN technology, operated by the energy company Southern Co. In addition, in the southwestern provinces of Canada, Clearnet also provides communication services in the iDEN network, consisting of 320 BS.
In Latin America, iDEN networks already exist in Bogota (Colombia) and Buenos Aires (Argentina). They are being built in Sao Paulo and Rio de Janeiro (Brazil), as well as in Mexico City (Mexico). Deployment of iDEN-based systems in Peru, Venezuela and Chile, as well as expansion of systems in Colombia and Argentina, are planned in the near future.
In Asia, iDEN systems are used in several countries: such systems have been operating in Tokyo and Osaka (Japan) for more than two years, and in Singapore for about a year. There are systems in China, South Korea and the Philippines. Construction is underway in Indonesia. In the Middle East, a nationwide iDEN network has been deployed in Israel, and construction of such systems has begun in Morocco and Jordan.
Each of the listed systems is designed to serve tens of thousands of subscribers.
The modular principle of the system organization provides various implementations. For example, the iDEN network can be initially deployed as a pure trunking system, and then mobile telephony, text messaging and data capabilities can be added as needed. According to the system developers, today iDEN is one of the few commercially proven technologies that provide the entire range of mobile communication services.
Andrey Aleksandrovich Denisov is the manager of Motorola for the iDEN system in the region of Eastern Europe and the former USSR. He can be contacted at: [email protected] and fax 785-0160
So, when choosing a commercial trunking operator, users should pay attention not only to the presence of a license from the Ministry of Communications, but also to some “passport” data of the network. First of all, these include supported communication protocols, which can be divided into open and “proprietary”. Open protocols allow any company to organize the production of basic and subscriber equipment, but the developer of a “proprietary” protocol is the only manufacturer of the corresponding devices.
The openness of the protocol leads to competition among manufacturers, which increases the performance of infrastructure equipment, and systems that differ in functionality and cost appear on the market. If there are many offers of subscriber devices, the consumer has the opportunity to choose a fleet of radio stations depending on the required price/quality ratio. But the main thing is that it is not tied for life to the equipment of a specific company. For example, for use in a network organized on the basis of an open protocol such as MPT-1327 (there are many varieties of it), it is possible to use equipment from most radio equipment manufacturers. On the contrary, only Ericsson devices can work with the “proprietary” EDACS protocol, and only Nokia equipment “understands” the ACTIONET standard.
Service area
According to the principles of organization, trunking communication is similar to cellular communication. Each base station “covers” a certain area. The coverage area (read: area of competence) is called a site (in cellular communications, a cell). To ensure stable communication at all points in the service area, continuous coverage is necessary. One base station is physically unable to fulfill this condition: there will certainly be “holes” in the zone where the radio station will not be able to receive a signal. For example, it will not be possible to organize stable communication near some reinforced concrete buildings, and in order to get out of the “radio shadow” area, the user will have to go around the building or move to an open space. Therefore, for continuous coverage, at least three base stations are required.
The quality and reliability of communications are determined not only by the number of transmitters, but also by their locations, the height of the antennas, as well as technical parameters base stations. The easiest way to check the quality of communication provided by a specific operator is to borrow subscriber equipment from it for a while to test it in working conditions.
Frequency
In Russia, several frequency ranges have been allocated for commercial trunking communication systems: 136 - 174, 403 - 470, 470 - 520 and 800 MHz. The user needs to remember that the lower the frequency at which the operator operates, the greater the communication range. On the other hand, the higher the frequency, the shorter the distance between base stations and the better the quality of communication. The best option may be the range 478 - 486 MHz. Previously, this section of the frequency spectrum was reserved for TV channel 22, but several years ago it was put out for tender, and now it is distributed among five Moscow radio operators. This range is free from the influence of paging company transmitters and other sources of interference.
Service and maintenance
Who will install and connect subscriber equipment? If the operator offers the user to install the radio station in the car himself or sends him to another company for this purpose, then, most likely, he simply decided to save on paying the technical staff. Then the question of service guarantees remains open. Besides, who knows in what other ways he tries to minimize his expenses.
Prices for all operators are approximately the same. They consist of two components - a one-time payment at the time of connection and a monthly subscription fee. A one-time payment consists of the price of the radio station and necessary accessories (85-90% of the total amount), the cost of obtaining permits (2-3%), connecting to the network (4-6%) and installing the radio station (4-6%).
User equipment can be purchased, rented, or leased (with the option of repurchase after a year). In addition, some companies buy back old equipment at residual value. Its price is used to offset the one-time payment for a new connection.
In Moscow, trunking communication services are provided by more than 15 operators. Many companies supply equipment and install local (departmental) networks. So the customer can always choose a company that can fully satisfy his immediate needs.
AMT. This is one of the first commercial radiotelephone operators in Russia. The AMT network of the MPT-1327 standard is built on the basis of Nokia equipment. Its coverage area includes the territory of Moscow and the Moscow region at a distance of up to 50 km from the Moscow Ring Road, as well as the Moscow region cities of Solnechnogorsk, Dubna and their environs. The company's services are designed for both individual consumers (radio telephones) and corporate customers (virtual departmental radio communication networks). The system uses full-duplex and half-duplex radios. In addition to voice communication, data transmission is supported. There is full access to the public telephone network and roaming with regions is provided.
ASVT (Rusaltai). The Rusaltai network is built on the basis of Actionet equipment from Nokia. The leading base station is located on the Ostankino tower, and 10 others are deployed in the Moscow region to ensure its full coverage and partial coverage of surrounding areas. For now, the network's services are positioned as radiotelephone services, that is, the client receives a radiotelephone with a direct Moscow number. However, unlike a cell phone, the subscriber device provided by the company is also capable of operating in half-duplex mode, which is used in trunking for group communication. The Rusaltai network uses not per-minute (as in cellular communications), but per-second billing, which, with a similar cost of airtime, allows subscribers to significantly reduce costs.
"RadioTel". This largest trunking operator in the North-West, and in Russia, is part of the Telecominvest group. The RadioTel company is the only St. Petersburg mobile communications operator that provides the construction of hierarchical communication systems for corporate users, trunking communications with the ability to access the GTS, emergency communications with Ambulance (03), duty services of the city administration and the Office of Civil Defense and emergency situations. The coverage area of the RadioTel network includes the whole of St. Petersburg and the nearest suburbs. Terminal equipment is manufactured and supplied by Ericsson and Maxon corporations. At the beginning of 1996, the company created its own dispatch service, St. Petersburg Taxi 068, which currently serves more than 50% of taxi calls in the city by telephone.
In 1999, at the request of one of the St. Petersburg fuel companies, RadioTel developed the project “Data transfer for accepting payments using plastic cards of major payment systems.” The created system is multifunctional and allows solving several problems, including the task of ensuring transaction security.
In 1999, RadioTel won the tender to organize trunking communications for the Emergency Medical Service and supplied it with 350 pieces of equipment. Today, every ambulance in St. Petersburg is radio-equipped by this company.
"MTK-Trunk". The MTK-Trunk network is built on the basis of SmartZone equipment from Motorola. Six sites provide reliable communication in the capital and at a distance of at least 10 km from the Moscow Ring Road for portable and at least 50 km from the Moscow Ring Road for car radios. The network is aimed at collective users (organizations), which are characterized by high personnel mobility and random distribution of employees throughout Moscow and the region. Each client is allocated its own virtual network. Group and personal calls are made throughout the entire radio coverage area from any subscriber radio station without additional manipulations or switching. It is possible to establish communication outside the network coverage area in talk-around mode (direct channel), as well as exit from the subscriber station to the public telephone network.
"RadioLeasing". This is the first operator of a commercial trunking network in Moscow. Several networks are united under the Translink brand:
Local networks in the 160 MHz range (on “direct” simplex channels);
pseudo-trunking network SmarTrunk II (since 1992);
multi-zone trunking network MRT-1327, built on the basis of Fylde Microsystems equipment.
Currently, there are five base stations (22 channels) operating, which support reliable communication within 50 km from the Moscow Ring Road.
"Regiontrank". The company provides radiotelephone communication services in Moscow and the Moscow region, as well as in the regions of Central Russia. The first communication network based on the ESAS protocol, operating in the 800 MHz band, was put into operation in 1997. Currently, six base stations are located in Moscow, which ensures reliable reception within the city for portable subscriber stations and in the near Moscow region for car devices. A distinctive feature of Regiontrank’s services is the development of professional business solutions that take into account the special requirements of customers. For example, a software and hardware complex “Taxi Dispatch Service” was created for a large Moscow taxi fleet.
"Center-Telko". The city integrated radiotelephone communication system "Sistema Trunk" was deployed in accordance with the decree of the Moscow government of October 29, 1996. The network is built on the basis of EDACS equipment, which ensures high security of communication channels and reliable operation of the system in any extreme situations. Four base stations support the operation of portable stations in Moscow and the immediate Moscow region (4-7 km from the MKAD), and automobile ones within 50 km from the MKAD. In addition to traditional services for radio communication networks, the System Trunk network provides services for transmitting digital data and determining the location of objects.
Operators of single-zone trunking networks
BTT. The BTT network uses EF Johnson equipment. Its peculiarity is that, along with a repeater, it uses a network of remote receivers connected to the base station by dedicated wire lines. User terminals are characterized by high reliability.
"Softnet". The Softnet system was created to provide operational dispatch communications. This is what caused the choice of LTR as the trunking protocol. The main users are services that require unified management, such as taxis, cargo delivery, cash collection, security services, etc. The advantage of this network is the presence of an operational communication channel with the Moscow City Rescue Service, provided to subscribers free of charge.
Pseudo-trunking networks
MCS(" Mobile systems communications"). MCS is one of the first trunking networks based on the SmarTrunk-II protocol - it was deployed back in 1994. Basic DX-RADIO equipment (USA) is located at the 269th and 325th marks of the Ostankino TV tower, which provides a coverage area within a radius of 80-90 km. Together with Center-Telko, MCS is part of the City Integrated Radiotelephone Communication System (GISRS), created by decree of the Moscow government.
Currently, the Mobile Communication Systems company provides all carriers of dangerous goods (fuel, oil, acids, etc.) with voice communications, condition monitoring sensors and GPS. The unified control center is located in the Civil Defense and Emergency Situations Directorate. Services are provided for half-duplex and full-duplex communications, access to the telephone network, data transfer and GPS. There is a possibility local work(without a repeater) on simplex frequencies throughout Moscow and the Moscow region. It is possible that equipment will be provided free of charge to a potential customer for testing in real conditions.
"Lancombe". The SmarTrunk-R mobile radiotelephone communication system has been in operation in Moscow since 1995. The Moscow segment of the network consists of two base stations with a total capacity of 11 radio channels operating in the range 430-450 MHz. Due to the spacing of base stations (BS No. 1 is located in the Alekseevskaya metro area, and BS No. 2 is located near the Belyaevo metro station), uninterrupted communication is ensured within the Moscow Ring Road and partially in the near Moscow region.
Since 1999, the company has been operating mobile radiotelephone communication systems in Orel, Kursk, Belgorod and Tambov. The work of subscribers of the Moscow trunking network in the above cities is possible by replacing their terminals at the Lanskom office with equipment compatible with regional trunking systems. A similar opportunity is provided to subscribers of regional networks.
"Everlink". A single-zone five-channel pseudo-trunk communication system, based on the E-trunk protocol, provides stable reception to portable radio stations within Moscow and to mobile radio stations within a radius of up to 30 km from the Moscow Ring Road. Telephone services are not provided. The license extends to Moscow and the Moscow region, which allows you to offer direct channel services to consumers (communication with portable radios up to 2 km in any building conditions).
Pavel Dmitriev, Networks, No. 10/2002
In almost every cellular communication store, the windows of which are bursting with mobile phones, there is a security guard with the obligatory bulky walkie-talkie. Here you involuntarily ask the question: “Why doesn’t this person use a simple mobile phone for service?”
Today, along with the usual cellular communications, there are so-called professional mobile radio systems (PMR) (Professional Mobile Radio-PMR), or trunked mobile radio. They occupy their sector of the mobile communications equipment market for corporate users, various departments and social services, performing functions necessary specifically for these users.
Trunking mobile radio communication (from English. trunking- provision of free channels, trunk- trunk line) is a two-way mobile radio communication system that uses the ultrashort wave range. In practice, the PMR system is structured similarly to a cellular one: user terminals and base stations (BS), equipment to increase the communication range - repeaters and a controller that controls the operation of the station, processes the repeater channels (switches them) and provides access to the city telephone network. Trunking networks can be single-zone (contain one BS) or multi-zone (several BS). There are analog and digital trunking communication systems.
Better than a cell phone?
How does trunking communication differ from cellular communication, if, apart from the difference between the user terminal (walkie-talkie/phone), everything is arranged the same?
Cellular communications are positioned as a “phone in your pocket,” while trunking is designed to solve a narrow range of professional tasks. Cellular communications, for example, provide a variety of multimedia services, but an oil worker on duty on a drilling platform in the Baltic Sea or a rescue worker from the Ministry of Emergency Situations are unlikely to rely on the opportunity to download Madonna’s new album. Trunking communication are chosen by organizations such as the Ministry of Emergency Situations, security agencies, taxi companies, etc. For ordinary office workers, the option “ cell phone+ corporate tariff plan.”
The communication system used by professionals must support features such as:
Implementation of instant communication (0.2-0.5 seconds) within a group of subscribers, which can be specified in advance;
Ability to redistribute group members during a communication session;
Call priority system ( mobile operator does not differentiate between subscribers);
Maintaining communication even if the base station fails;
Transmission of a broadcast signal to network subscribers;
Ability to quickly reconfigure the network.
These requirements are impossible to meet in cellular communication systems, but are fully supported by trunking systems. It is worth noting that mobile communications market participants do not sit idly by and offer the service Push-To-Talk with the ability to establish a group call and quickly establish a connection. However, the innovation in any case does not meet the requirements of professionals. You can read more about Push-To-Talk here.
We offer a comparison table using the example of two versions of TETRA - a popular standard for digital trunked radio communications, and GSM networks.
Modes and functionality, communication standards TETRA (Rl) TETRA (R2) GSM Group call + + +/- Broadcast call + + - Emergency call + + +/- Priority call + + +/- Priority access + + - Duplex communication + + + Delayed call + + - Delayed connection + + - Direct communication mode (without base station) + + - “Receive only” mode - + - Possibility of expanding the communication area - + - Zone selection + + - Status messages + + - Transmission of short text messages + + + Calling a dispatcher + + - Providing wide bandwidth upon request of a subscriber + + - Encryption capabilities for signal and radio interface + + +/- Simultaneous transmission of voice and data + + + High-speed data transmission - + + Selective listening of subscribers by a dispatcher + + - Remote listening to the acoustic environment + + - Dynamic regrouping + + - From steampunk to cyberpunk
Professional analog communications have existed almost since the beginning of the 20th century and during this time it has changed a lot, coming to digital technologies with impressive luggage.
Everyone knows that radio communication began in 1895, when A. Popov (and only a year later G. Marconi) created the first receiver. From 1897 to 1915 G. Marconi organizes the first communication companies and launches equipment production; Radio communication regulations are appearing, including on the distribution of frequencies between various services. Professional radio communications began in the period from 1915 to the 1950s.
In the first half of the 20th century, the possibilities of communication at different wavelengths were explored. Before 1920, communications were carried out using waves ranging in length from hundreds of meters to tens of kilometers. In 1922, the property of short waves to propagate over any distance, refracted in the upper layers of the atmosphere and reflected from them, became known - an ideal means for long-distance communication. The 1930s became the time of meter waves; and the 1940s - decimeter and centimeter, spreading rectilinearly over 40-50 km within line of sight. The popularization of radio communications directly depended on technological advances. Before the advent of miniature semiconductors, receivers remained bulky and, at best, fit into a suitcase, which imposed certain limitations.
The history of professional radio networks is usually divided into stages. The first stage networks are considered to be of a conventional type (from the English. conventional- ordinary, traditional). Their limited capabilities are as follows: simplex operating mode (pressed a button - asked a question - released the button - received an answer - pressed the button - ...), making individual and group calls (up to several dozen subscribers) In conventional systems, the communication channel (frequency) is strictly assigned to a specific group of subscribers. This guarantees high communication efficiency (you only need to adjust the frequency), but causes low network throughput (there are few frequencies).
Second stage- trunking networks. Such networks made it possible to serve up to several hundred subscribers and allowed for more efficient use of radio frequency resources. Such communication systems have become systems with shared access subscribers to the frequency range, in contrast to conventional systems. This provides increased throughput and greater coverage area.
Multi-zone trunking networks third stage. The service area in them has increased even more due to several base stations. The number of subscribers served has become practically unlimited, a call priority system has appeared, the possibility of a duplex call mode (no need to press a button, the connection is similar to a telephone one, adjusted for a much higher call speed), access to telephone networks public use, data transfer.
Simplex, half duplex and duplexNo, these are not the names of the sequels to the comedy "Duplex", which starred Hollywood stars Ben Stiller and Drew Barrymore. The heading contains the names of the three basic wireless radio communication modes.
1. Simplex communication uses one frequency for reception and transmission. Only exchange of replicas is possible. Due to the limitations imposed by physics, you can use this most economical type of wireless radio communications at a distance of no more than 5 km. An open area is highly desirable for a stable signal. Communication is carried out through user terminals.
2. Half-duplex communication also uses two frequencies, but you will have to communicate as in simplex mode. A base station (BS) constantly receives subscriber signals on one frequency, and then broadcasts what it has received on another frequency. The radio uses the frequency on which the BS broadcasts for reception and must contain a radio frequency switch. The half-duplex principle underlies low-cost networks that connect dozens of subscribers in different parts of the city and open areas.
3. Duplex communication uses two frequencies - one for reception, the other for transmission and is intended to conduct a familiar dialogue. Naturally, base stations are used to relay signals. Analogue duplex systems require two channels (4 radio frequencies) to connect subscribers. The terminal is equipped with a large duplex filter, whose role is to give the receiver and transmitter simultaneous access to the antenna. Digital duplex is implemented differently and does not require a cumbersome filter - at every moment of time the subscriber’s device is receiving or transmitting. For example, in the TETRA standard, switching occurs 18 times per second.
Modern digital trunking networks (DH) are the top of the evolutionary chain of professional communication. In addition to the capabilities available to users of analogue systems, reliable protection against unauthorized access is added (in addition, listening to conversations using analog devices becomes impossible) and packet data transfer (Internet access). The subscriber's device is identified using various identification mechanisms or SIM cards. In essence, digital trunking systems are universal communication networks that ensure the confidentiality of subscriber contacts, and are capable of simultaneous transmission of large data streams over communication channels, be it telemetry data or video information (the latest editions of the standards provide for such capabilities).
There are a large number of different standards for trunked mobile radio communication systems, differing in many ways. In our country, as well as throughout the world, analog systems are still common different versions and standards. However, due to their obsolescence, they are not as interesting to consider as their digital counterparts. The five most popular and recognized in many countries of the world are worth considering in more detail.
EDACS (Enhanced Digital Access Communication System)
Firm Ericsson(Sweden) before others (until it was bought Sony in the 1980s) became concerned about the problem of obsolescence of analog technologies and the insufficient degree of security of communications in such systems and began developing the corporate closed standard EDACS (Enhanced Digital Access Communication System). Initially, the standard provided for speech transmission via analog protocols, later the standard was modified and a digital version of the system appeared called EDACS Aegis. EDACS systems operate at frequencies of 138-174 MHz, 403-423 MHz, 450-470 MHz and 806-870 MHz; the network can be extended to more than 16,000 subscribers. In Russia, this standard is not very popular due to its closed nature and rapid obsolescence (in fact, it is a digital standard for transmitting analog signals). All rights belong to the developer, and you will not be allowed to release the equipment just like that. In addition, Ericsson has stopped supplying equipment to deploy new networks of this standard and is only supporting existing ones.
iDEN technology ( integrated Digital Enhanced Network) is a closed corporate standard, the development of which was started by the company Motorola in the early 1990s. In 1994 in the USA the company NEXTEL The first commercial application network was deployed based on this technology. Today, similar networks are deployed in many countries in North and North America and Asia. Today, iDEN has more than 3,000,000 subscribers (90% of them in the USA). iDEN has gained such popularity due to the fact that it is a kind of compromise between trunking and cellular systems (it provides the ability to send messages, fax, and transmit data via TCP/IP at speeds of up to 36 kbit/s, low cost). Each organization using the iDEN standard can create up to 10,000 virtual networks, each of which can have up to 65,500 subscribers. iDEN uses frequency range 805-821/855-866 MHz. There are no iDEN systems in Russia - most likely due to the inconvenience of using such a frequency range when solving problems for which professional communication systems are designed. It is noteworthy that the company Motorola Various iDEN devices are produced with the functions of modern mobile phones. For example, Motorola ic502 is a CDMA/iDEN phone with GPS and Motorola i290 with an MP3 player.
Tetrapol PAS (Tetrapol)
Developed by a French company Matra Communication. The creation of this closed standard was started in 1987 by Matra Communications at the request of the French gendarmerie. The Tetrapol standard communication network has been operating on half of France since 1994 and serves more than 15,000 subscribers. Tetrapol standard communication systems operate starting at a frequency of 70 MHz and have a performance ceiling of 520 MHz, which does not contribute to popularization in other countries where similar systems Traditionally, other frequency ranges may be allocated. Experimental zones for the functioning of the Tetrapol network have been created in Russia.
TETRA (Terrestrial Trunked Radio)
TETRA- an open standard for professional radio communications, developed since 1994 ETSI(European Telecommunications Standards Institute - European Institute of Telecommunications Standards). TETRA stands for Terrestrial Trunked Radio. Initially, until the standard gained popularity outside of Europe, TETRA stood for Trans-European Trunked Radio- “trans-European trunking radio”. In Europe, the TETRA standard PMR operates in the frequency ranges 380-385/390-395 MHz, 410-430/450-470 MHz. In Asia - 806-870 MHz.
In the specifications, TETRA is listed as an open standard, which means that anyone who wants to produce communications equipment does not have to worry about problems of compatibility with equipment from other companies and the division of copyrights. To produce products that support this standard, you must join the organization MOU TETRA- Memorandum on promotion of the TETRA standard. Nokia, Motorola, RohdeSchwarz and other large communications equipment companies support this standard. TETRA networks are deployed throughout almost all of Europe, Asia, Africa and South America. TETRA Release 2 - new version standard, which allows for tight integration with mobile networks third generation and significantly increase data transfer speed. Network Deployment Project this standard in Russia it is called “Tetrarus”. The fact that “within the framework of the Federal Target Program “Development of Sochi as a mountain climatic resort until 2014” says a lot. TETRA radio communications will operate at the venues of sporting competitions and throughout the Krasnodar Territory.”
APCO Project 25 (APCO 25)
Open standard APCO 25 created by the organization AssociationofPublicSafetyCommunicationsOfficials-international-Association of representatives of public security communications services. The standard was created and improved (construction of the radio interface, encryption protocols, speech coding methods) in the period from 1989 to 1995. One of the main advantages of APCO 25 is that it allows operation in any of the frequency bands available for mobile radio systems: 138-174, 406-512 or 746-869 MHz. Up to two million people and up to 65 thousand groups can be united into one network. Since 2003, a similar network with several hundred subscribers has been operating in St. Petersburg for the purposes of the Russian Ministry of Internal Affairs.
Trunking can be used not only for communication:
Latest system trunking JRC Trunked Radio System with function automatic detection vehicle location based on GPS and MPT 1327/1343 standards. In addition to, in fact, ensuring communications between subscribers, the standard provides automatic transmission of data on the location and status of each machine to the terminal in the control center.
An example of two ways to organize a trunking network:
The characteristics of the standards are reflected more fully in the table:
Functionality, digital trunking standards APCO 25 EDACS IDEN TETRA Tetrapol Individual, group, broadcast calls + + + + + PSTN access + + + + + Full duplex subscriber terminals - + + + - Data transmission and access to databases + + + + + Direct communication mode + + ? + + Automatic registration of mobile subscribers + + + + + Personal call + - + + + Access to IP networks + + + + + Transmission of status messages + + + + + Transmission of short messages + - + + + Transmission of subscriber location data from GPS receiver? + ? + + Fax + - + + + Is it possible to set up an open channel? - - + + Multiple access using a subscriber list + - + + + Signal relay mode + ? ? + + “Dual surveillance” mode ? - ? + + Access/call priority + + - + + Dynamic regrouping + + - + + Selective listening + + - + + Remote listening? - - + + Identification of the calling party + + - + + Call authorized by the dispatcher + + - + + Transfer of keys over the radio channel (OTAR) + - - + + Simulation of subscriber activity - - - - + Remote disconnection of the subscriber + ? - + + Subscriber authentication + ? - + +
In Russia, simultaneously with the introduction, successful use and development of digital networks of various trunking standards, analogue systems based on the old MRT1327. And this is by no means a bad thing. Digital trunking is convenient where not only operational communication is needed, but also data transfer and telephony. Often, simplex voice communication and messaging functionality are sufficient for customers. Using analog systems saves time and money.
In general, the situation with professional mobile radio communications resembles the transition from the use of second-generation cellular networks of the standard GSM to standards 3G. Cellular networks, despite their growth rates, in the near future they will not be able to completely replace professional radio communication networks due to the fact that they perform other functions.
