Trunking: a smart replacement for cellular communications. Trunking communication systems Principles of trunking communication

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 between 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 zone

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 the technical parameters of 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 up 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 invites 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%).

Subscriber 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 transmission 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 radios 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 determined 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 Communication Systems). 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. It is possible to operate locally (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 area of the Alekseevskaya metro station, 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 applies to Moscow and the Moscow region, which allows us to offer consumers direct channel services (communication from portable radio stations up to 2 km in any built-up area).

Pavel Dmitriev, Networks, No. 10/2002

Trunking (trunk) systems are a type of mobile communication systems, used mainly to provide mobile communications by various departments (Ministry of Internal Affairs, Ministry of Emergency Situations, etc.). Trunking is understood as a method of free and equal access of mobile subscribers to all channels of the communication network. A trunked radio communication system is a system that provides dynamic provision of a small number of communication channels to a larger number of subscribers (correspondents). In such a system, each subscriber can be provided with any of the free channels. A subscriber radio station can send a request for a communication session to all base stations of the network and, when a communication channel is released on any of them, it occupies this channel for the duration of negotiations. This method of communication allows the probability of denial of service to be much lower than in single-channel or multi-channel radiotelephone systems. The block diagram of trunking communication is shown in Fig. 2.4.

Figure 2.4 - Block diagram of trunking communication: RT - radiotelephone of the trunking communication network, MS - mobile station of the trunking communication network, BPS - base transmitting station, TC - trunking controller, CKS - communication switching center, PSTN - public telephone network

The fundamental difference between trunking systems and other mobile communication systems is that frequency channels are not assigned to specific subscribers. The system has its own specific operating range, which is provided by several frequency channels. The choice of a free communication channel for a session is carried out by the system itself. At the end of the communication session, the same frequency channel can be provided to other subscribers of the system.

The main meaning of the trunking method of organizing communication is that simultaneous communication sessions of a large number of subscribers have a certain probability, therefore the number of operating frequencies can be selected so that the full occupancy of communication channels is no more than acceptable. The above can be explained by the time diagram of the operation of a 4-channel trunking system (Fig. 2.5), in which the occupancy of each communication channel is 40-60%. As can be seen from the diagram, the occupancy of each communication channel separately is quite high, and the system load as a whole is low (10%). If all communication channels are busy, the new service request is not lost, but is queued until a free channel becomes available.

1 channel

Channel 2

Channel 3

Channel 4

system

Figure 2.5 - Timing diagram of the trunking communication system operation

In trunking communication systems, a channel is allocated to a specific subscriber using two methods.

The first method involves searching for a free channel and sending a calling signal to the mobile subscriber station. Before establishing communication, the mobile station automatically searches for a free channel and, on each identified channel, attempts to establish communication with the base station. At the same time, the main disadvantage of this option appears, namely, the duration of the communication channel establishment cycle significantly exceeds the similar duration when the channels are fixedly assigned to specific mobile subscribers. Therefore, their use is effective with a small number of communication channels.

The second method of constructing a trunking system allows the base station control subsystem to search for a free communication channel. To solve this problem, a special control channel of the base station is used, through which the functions of establishing, maintaining and terminating communication are provided.

Trunking systems provide such capabilities as automatic switching of an established connection to a working channel in the event of a malfunction of the main communication channel, prompt switching of a working communication channel to another carrier frequency in the event of strong interference.

The simplest of the existing trunking systems is a single-zone analog system of the Smar Trunk II standard, operating in the ranges of 146 - 174 MHz and 400 - 470 MHz. The base station contains one control and fifteen working channels, which provide operation for up to four thousand subscribers.

A more modern analog trunking system is the MPT 1327 equipment with centralized control (Fig. 2.6).

Currently, there is a tendency to move from analogue communication systems to digital ones. The fully digital trunking system is a TETRA standard system.

The structure of the complexes of various trunking systems is approximately the same. The modular principle of constructing such systems allows them to be expanded to the required capacity.

Basic equipment for each channel includes:

Duplex transceiver (repeater);

Trunking controller;

Antenna-feeder device.

Subscriber kits are made on the basis of popular radio stations Kenwood, Icom, Alinco, Motorola, Standard, Yaesu, etc. with special logic boards installed in them that control the radio station and implement certain functions.

Radio stations can be programmed for the functional tasks of subscribers of this system using a special device - a programmer.

Various trunking systems provide a similar range of capabilities. For example, both single-zone and multi-zone systems achieve increased communication range. In a single-zone system, this requires increasing the base station transmitter power and using more sensitive antennas. In a multi-zone system, the same result is achieved by using several base stations with reduced transmitter power. A large number of base stations in a multi-zone system makes it possible to reduce the distance of the subscriber radio station from the base station, which increases the stability of communication. When a subscriber moves to an adjacent zone, communication support is relayed from one base station to another, that is, the established connection is not interrupted. Modern trunking systems provide the ability to divide the total number of subscriber radio stations into groups (squads), within which we can make an individual and group call. Such a system can be applied, for example, within a municipality, combining several city services into a common radio network, including units of the local fire brigade and emergency rescue units. Moreover, each service can have a communication network completely isolated from other services, and mutual calls between groups will be programmatically allowed only to specific radio stations.

The following types of calls are implemented in trunking systems:

An individual call can be addressed to any specific radio station, with each radio station assigned a specific set of numbers;

A group call is intended for a predetermined group of subscribers with their own identification number;

A general call can be sent to all subscribers of the radio network (group);

An emergency call allows you to interrupt conversations of any subscribers on the radio network;

Priority calling provides connection priority to the main radios in the corresponding subscriber group;

Sending a status allows a radio with an alphanumeric display to automatically select from memory messages corresponding to a given status and display it as a line of text;

A radiotelephone call provides the subscriber with access from the radio station to the public telephone network, as well as to the private branch exchange network, and its connection to such networks can occur both through the subscriber line and through the trunk line. A call to a subscriber of a mobile station of a trunking system from the public telephone network is carried out using an additional number;

Call forwarding allows you to transfer a call from one radio station to a predetermined other radio station;

A direct call ensures that the radio station switches to simplex operating mode to establish communication with other radio stations on the network without the participation of a base station.

Important service functions of modern trunking systems are the ability to transfer data between radio stations and provide wireless access to databases.

Additional functions of these systems include the ability to transmit short alphanumeric messages over the control channel without occupying the working channel, as well as providing voice mail.

Significant advantages of the trunking system are individual programming of access to each type of opportunity, setting a limit on talk time and subscriber priority, and the presence of protection against unauthorized access to the system. In addition, these systems can be used as a transport medium for systems for determining the location of moving objects and telemetry systems.

The wide inherent capabilities of trunking systems and their compatibility with various types of telephone networks make it possible to effectively use these systems to provide operational dispatch communications. Their use is limited in comparison with conventional (conventional) radio stations by more complex operating procedures.

Trunking radio communication networks are widely used to solve problems of RSChS management and civil defense using mobile communication components. Such networks, as a rule, include stationary, automobile and portable radio stations of the chiefs of civil defense of the constituent entities of the Russian Federation, the administrative center, its urban districts, the heads of the civil defense authorities of the constituent entity of the Russian Federation, the administrative center and its districts, members of the commission for the prevention and response of emergency situations and fire safety (KChSPB), heads of civil defense services, heads of search and rescue teams, duty services of the administrative center. Mutual use of trunking communication networks is based on entering into their databases the general numbering of radio stations of officials and operational groups allocated for use as interacting ones.

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 of 800 MHz. Currently, two companies Motorola and RIM are engaged in the production of terminals. In 2010, the Android terminal with a touch screen i1 was presented.

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"

Performed

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). Turning on the 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 ) and 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 by a common control system. 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 Russian federal mobile cellular network 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 ability to organize 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 BSs, 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 KR In the case of building a large network covering a large area, several KR and one central system controller (CSC) are used, which unites several KR and serves as a common switching and control center for the network, and switching and control in each individual zone, including the output, remain possible on the PSTN. In addition, the central network allows you to organize centralized maintenance of the trunking network. Communication between fixed and mobile subscribers (MS) is carried out through a network that includes the CD and the central network.

Connecting a trunking network to the PSTN.

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Federal Communications Agency State educational institution of higher professional training “Siberian State University of Telecommunications and Informatics” (branch)

Khabarovsk Institute of Infocommunications Faculty of Correspondence Studies

Course project

discipline: Radio communication systems with moving objects

on the topic: Design of a trunking communication network

Completed by: 4th year student of the Federal Educational Institution

specialties MTS (US)

Malysheva V.V.

Khabarovsk 2010

Introduction

3.4 Determination of the number of RFKs in the presence of several radio coverage zones with access to the telephone exchange through one base station

Literature

trunking network radio communication

The type of development of the service area has been specified. Determine the operating frequency range based on the type of building.

1. Determine the average size of service areas based on the type of development in the area, the power of the radio transmitter, the height of the antennas and the operating frequency range.

2. Carry out frequency planning of the network.

3.1 Develop a plan for the placement of base stations taking into account the topology of the area.

3.2 Determination of channels for each BS.

3.3 Calculation of service area and interference area for each BS.

4. Calculation of radio communication range.

5. Draw up a communication organization diagram.

6. Draw up a block diagram of the network based on the number of BS.

7. Draw up a block diagram of the BS, determining the type of basic equipment.

8. Draw up a block diagram of a single-zone or multi-zone trunking system.

9. Draw up a block diagram of control in the trunking system.

Initial data for completing the course project (option No. 6):

Type of development: mid-rise building

Type of object: mobile objects

Transmitter power: Rper = 30 W

Receiver sensitivity: Ec = 0.5 µV

Antenna height: h = 25m

Number of users: 325

Height differences: Hmax = 250m, Hmin = 50m

Antenna gain: G = 7 dB

Gravity coefficient: G = 0.35

Attenuation in AFU: 10 dB

Average number of calls: C = 4.4

Average call duration: tav = 28 sec

Transport density: V = 7 cars/km2

BS transmitter feeder length: lperBS = 17 m

AC transmitter feeder length: lperAC = 1.1 m

Feeder losses: DRf = 2.5 dB

Losses in the combiner: DRk = 4 dB

Also, the initial data is shown in Table 1.

Table 1

Options	Base station no.

Introduction

Currently, there are a number of land mobile radio communication systems:

Personal radio call systems (paging);

Dispatch (operational) radio communication systems;

Trunking radio communication systems;

Cellular telephone radio systems.

Trunking radio communication systems have become the most successful implementation of the development of operational mobile communication systems, which are highly efficient with the intensive exchange of operational information for a large number of subscribers who can be united into groups according to operational and functional characteristics. The range of services provided by trunking systems is very wide and practically includes all their diversity: from data transmission to radiotelephony and from simple notification to automatic determination of the location of moving objects.

Trunking radio communication systems are multi-channel systems in which the subscriber, upon his request, is automatically provided with a radio channel and other system resources according to a given algorithm, which ensures high efficiency in the use of frequency resources.

Based on the principle of radio channel organization, all trunking systems can be divided into three conditional groups:

Analogue - radio communication systems with selective calling (DTMF, Select 5, etc.);

Analog-digital - systems in which the transmission of service information when establishing a connection is carried out in digital mode, and transmission in analogue mode (SmarTrunk II, MPT 1327, LTR, EDACS);

Digital - EDACS ProtoCall, TETRA, Astro.

Based on the presence of a control channel in the system:

Systems that have a control channel at the time of connection establishment - SmarTrank II, Selekt 5, etc.;

Systems with a permanent control channel formed in various ways - TETRA, MPT 1327, LTR, etc.

According to the method of providing the communication channel:

Permanent for the entire communication session - SmarTrank II, MPT 1327, etc.;

Provided only for message transmission and changes during a communication session - EDACS, TETRA.

According to the principle of organizing the management of basic equipment: decentralized - SmarTrank II, etc.; centralized - MRI 1327, EDACS, TETRA, etc. In addition, all protocols of trunking systems can be divided into 2 classes:

1. Open protocols (MPT 1327, TETRA);

2. “Proprietary” protocols (LTR, SmartNet, SmartZone, EDACS, ESAS, etc.).

Open protocols are available to any manufacturer. These protocols are recommended for use in many countries. Systems with such protocols are produced by many companies; the equipment, due to mass production and high competition, is usually cheaper than in specialized systems.

In Russia, the most well-known protocols of trunking systems are: SmarTrank II, MPT 1327, LTR, EDACS and SmartZone. Therefore, in the course project, when choosing standard equipment, MRI protocol 1327 was taken as the basis.

The MRT 1327 protocol is intended for creating large operational radio communication networks with a virtually unlimited number of subscribers. The most important advantages of the MRI protocol 1327 are:

The ability to build multi-zone systems on a national scale with a large number of base stations, which allows “communication coverage” of large territories;

A wide selection of subscriber and basic equipment MRI 1327: it is produced by many companies - Motorola, Tait Electronics, Fylde Microsystems, Bosch, Philips, Nokia, Rohde & Schwarz, etc.;

The protocol is not tied to specific frequencies, which allows you to select them depending on the availability of a frequency plan and the corresponding permission of the SCRF;

Standardization of system components makes it possible to simplify and reduce the cost of operation, maintenance, development and integration of networks into larger systems;

Provides the possibility of economical transmission of short messages;

Protocols make it possible to build effective networks for collecting information from condition and emergency sensors;

Guaranteed upgrades and maintenance;

Implementation of a smooth transition to new generation signal protocols (from analogue systems to digital systems of the TETRA standard).

Opportunities provided to subscribers of MRT 1327 protocol trunking systems:

Individual call to a mobile radio station;

Broadcast call, in which the called subscribers can only listen to information;

Calling a group of subscribers;

Priority and emergency calls;

A nested call that allows you to include other callers in an existing conversation;

Connection with subscribers of city and departmental telephone networks;

Forwarding by the radio station user of incoming calls to another subscriber;

Queuing calls;

Protection against unauthorized access.

Trunking systems of the MRT 1327 standard support a data exchange mode that ensures the transmission of: status messages; short up to 25 characters; extended to 88 characters; messages of unlimited length.

1. Determination of the operating frequency range

In this course project, the type of development is mid-rise, therefore, we can assume that the type of area is urban. For urban areas, the optimal ranges are 300, 450 and 900 MHz. Let's take the range to be 300 MHz.

2. Determination of the average size of service areas

The average size of service areas depends on the power of the radio transmitter, the height of the antennas, the type of building, the service area, the type of subscriber station and the operating frequency range.

For mid-rise buildings, the resource value of the service zones of mobile facilities is 15-30 km.

3. Network frequency planning

Frequency planning of the network is carried out based on the calculation of the zone of reliable communication for a given reception quality. In this case, it is necessary to use the principle of uneven distribution of the radio frequency resource over the territory proportional to the concentration of subscribers: use small-channel equipment in local networks of trunked radio communications, providing service from 100-200 to 1500-2000 subscribers.

3.1 Development of a base station placement plan

When developing a BS placement plan, we are guided by the following: the approximate radius of the BS service area for 300 MHz is 10-15 km. Based on this, a preliminary placement of the BS is carried out, taking into account full or partial coverage of the service area and the use of single or multi-zone systems. The number of repeaters for a BS is determined based on the distribution of subscriber load within the service area at the rate of 80-100 subscribers per channel.

3.2 Determination of the number of radio frequency channels for one service area without access to a telephone exchange

When calculating the number of RFCs, it is assumed that all traffic on the network is created only by radio subscribers and is completely distributed between them, i.e. the attraction of radio subscribers to PBX subscribers. To determine the RFC beam capacity, you need to know:

N - number of radio subscribers;

Снн - average number of calls in CHNN created by one radio subscriber;

Tav - average call duration.

where is the load coming from one subscriber to the CHN, equal to:

Knowing that the average number of calls in the CNN created by one radio subscriber is 4.4, and the average call duration:

tav = 28 sec = 0.007778 hour,

we determine the load coming from one subscriber to the CHNN:

When blocking a call permanently:

at given N = 325,

According to the schedule (Figure 1), we determine that the required number of radio frequency channels:

V = 13 channels.

And the specific load coming from 250 subscribers is equal to:

3.3 Determination of the number of RFKs for one service area with access to a telephone exchange

In some cases, radio subscribers of a trunking network may have access to a PBX. In this case, part of the incoming load is the load between the system and the telephone network's PBX. Figure 2 shows a diagram of servicing a base station in one zone with an automatic telephone exchange.

According to the assignment, the gravitational coefficient is given:

network subscribers to the PBX. Let us determine the total load created by all subscribers, taking into account the gravitational coefficient using the following formula:

According to the graph (Figure 3) for the calculated value:

Ae = 4 Earl,

Let's find the capacity of the channel bundle V1 to service the load between the system and the telephone exchange.

Channel bundle capacity V1 = 11 channels.

3.4 Determination of the number of RFKs in the presence of several radio coverage zones with access to the telephone exchange through one base station

Figure 4 shows a diagram in the presence of several radio coverage zones with access to one base station. The values, N and G (load coming from one subscriber to the CHN, the number of radio subscribers and the gravitational coefficient) for BS-1, BS-2, BS-3 and BS-4 are indicated in Table 1.

If there are several base stations (BS), one of them will be the main one, which has access to the PBX via cable communication lines. The remaining BSs are connected to the main one via radio relay communication lines. Each BSi has Ni - the number of radio subscribers, and each of them creates a load i. For each BSi, the coefficient of gravity towards the ATS is given - Gi. The traffic of each BSi enters the PBX through the main BS. It is necessary to calculate the number of radio channels:

In each VBS zone;

Between the main BS and the PBX - V1;

Radio relay system connecting the BSi with the main one - Vpp.

Let's calculate the required values using the following algorithm:

1. Determine the total incoming load for each BSi using the formula:

2. According to the graph (Figure 1), we determine the number of RFCs based on the given values of i and Ni:

3. Let us calculate the incoming load Ae between each BSi and the vehicle, taking into account the gravitational coefficient:

4. Let’s determine the total incoming load from the BS to the PBX:

5. According to the graph (Figure 3), we determine the capacity of the channel bundle V1 between the main BS and the automatic telephone exchange using the found value of Ae total: V1 = 9 channels.

6. Based on the calculated loads Aei for each BSi, we determine the number of radio channels of the radio relay system Vpp connecting each BS with the main one. Vpp is determined using the graphical dependence presented in Figure 5.

4. Calculation of the base station service area

To determine the BS service area, we will make the following calculations:

1. Let us determine the effectively radiated power of the BS transmitter:

where RBS is the power of the BS transmitter, equal in this course project:

DRf - losses in the feeder equal to 2.5 dB;

DRk - losses in the combiner equal to 4 dB;

Go BS - BS antenna gain equal to 7 dB.

Substituting the values, we get:

2. Let us determine the parameter Dh, which characterizes the unevenness of the terrain. Approximately DH can be determined by the difference DH of the maximum and minimum elevations of the area:

Knowing that Hmax = 250m, and Hmin = 50m, we calculate:

3. Determine the effective height of the BS transmitting antenna:

where hBS is the height of the BS antenna relative to sea level (hBS = 25m);

the average terrain level relative to sea level at heights hi at a distance of 1000+250i meters from the BS, equal to 1.5 m.

4. Determine the median value of the minimum signal field strength for the subscriber station from the BS:

where is the field strength corresponding to the sensitivity of the AC receiver, dBµV/m;

Usign - receiver sensitivity, µV.

Effective length of the receiving antenna, m.

GAC is the gain of the AC antenna;

Rin - input resistance of the receiver, let's take Rin = 50 Ohm;

Ko is the reliability coefficient of the logarithmic distribution depending on the required reliability of communication in time and place (Ko = 1.64);

where and are the standard deviations of the signal in time and place:

DE and Dh - correction for uneven terrain:

Substituting the obtained values, we get:

5. Calculation of interference at the base station location

Calculation of the average effective value of the interference field strength at the BS receiving antenna point is carried out at frequency f MHz for a given traffic density in the reception area V.

Figure 6 shows the characteristics of radio interference observed in BS antennas. When assessing interference, a zone of perception of interference by the BS receiving antenna measuring 1 km 2 was determined, the interference was divided into three groups depending on the density of transport within the zone for each moment in time:

Transport density in the area of high levels of interference (Н) VН = 100 vehicles/km 2 ;

In the medium zone (M), the transport density is VM = 10 vehicles/km 2 ;

In the zone of low levels of interference (L), the transport density VL = 1 vehicle/km 2 .

In this course project, the interference, depending on the density of transport, is in the zone of medium levels, because VM = 7 vehicles/km 2

We take the average repetition frequency of interference pulses:

Fu = 3650 imp/p,

which weakly depends on the operating frequency; The standard deviation of peak interference values is taken equal to:

From Figure 6, for a given value of V and f, we find:

Ei (Ei = 22 dB).

Then, using the following formula, we find the average effective value of the interference strength:

where Piz is the effective bandwidth of a typical interference meter, we accept:

Ppr is the effective bandwidth of the receiver, we accept.

Taking into account the equipment’s own noise, the average effective value of the total interference field strength is:

where GН is the nominal sensitivity of the receiver, μV;

Attenuation in the antenna path of the receiver;

Feeder length;

(S/N)pr.in - nominal signal-to-noise ratio, taken equal to 10-12;

hd.pr - effective antenna height:

6. Calculation of radio communication range

Let us determine the field strength actually created by the transmitting BS at the receiving point for a given communication quality using the formula:

where Ec is the signal field strength required to obtain the specified quality indicators:

where EP.EF is the average effective value of the total interference field strength, equal to 9.43 dB

R0 = 5-10 dB - protection ratio to obtain a given reception quality

C = 8 dB - the value of the protective coefficient necessary to ensure the required protective ratio

Vr.n. - correction taking into account the difference between the rated power of the transmitter and the power of 1 kW:

where Рн is the rated power of the transmitter, equal to 30 W. That's why:

Vf - attenuation in resonators, bridge filters and antenna dividers is taken equal to 3 dB;

Вh2 - correction taking into account the height of the receiving antenna of the AC, dB:

For h2 = 3m: ;

Vrel - correction taking into account terrain different from Dh=50 m, dB.

Dh is determined by the formula:

where Hmax and Hmin are the maximum and minimum elevations of the terrain along the propagation path in the selected direction, equal to 200 m and 50 m.

Hence,

According to the graph (Figure 7) we determine Vrel (Vrel = 9 dB)

Du - gain of the receiving and transmitting antennas, equal to 7 dB;

Substituting the obtained values, we determine the field strength actually created by the transmitting BS at the receiving point for a given communication quality:

Having determined the field strength, according to the graph (Figure 8) we determine the expected communication range - 40 km.

7. Block diagram of the base station

Figure 9 shows the general principle of building a base station.

7.1 Block diagram of a single-zone trunking system

The structure of a single-zone trunking system is shown in Figure 10.

The radio signal combining device is used to combine and branch the signals coming from the transmitter and receiver of the repeater. A repeater is a set of transceivers serving one pair of carrier frequencies. One repeater can provide two or four traffic channels. Four channels to serve 50-100 radio channels; 8 channels - 200-500AC; 16 channels - up to 2000 radio subscribers. The coverage area of the BS at a frequency of 160 MHz is 40 km; at a frequency of 300 MHz - 25-30 km; at a frequency of 300 MHz - 20 km.

The switch handles all system traffic. The control device ensures interaction of all BS nodes. It processes calls, authenticates callers, maintains call queues, and makes entries into time-based payment databases.

The maintenance and operation terminal is designed to monitor the state of the system, diagnose faults, and make changes to the subscriber database.

The central station of the service area includes several transceivers, the number of which depends on the number of channels and the number of subscribers served.

The transceiver of each channel is controlled by a controller. The maximum number of channels at the central station is up to 24. One channel can serve up to 30-50 subscribers. To interact with all controllers of the central station, an interface unit is used, which is connected to all controllers via a common control bus, thus providing management, accounting and charging of connections.

In Russia, the most well-known protocols of trunking systems are: SmarTrunk II, MPT 1327, LTR and SmartZone. The MPT 1327 protocol is intended for creating large operational radio communication networks with a virtually unlimited number of subscribers.

Typical equipment specification in the 450 MHz band for mobile sites:

Basic equipment: Quantity:

Regional control processor T1530 1;

Operator console consisting of: computer and printer;

Operator console software T1504 1;

Switching unit T1560 1;

Channel interface board T1560-02 3;

Interface board T1560-03 for one 2-wire line 1;

Repeater T850 (50W, 100% operating mode) 4;

Trunking channel controller T1510 4;

System interface T1520 1;

Modem T902-15 2;

Cabinet 3 8RU 2.

Antenna-feeder equipment: Quantity:

Combiner M101-450-TRM 1;

Duplex filter TMND-4516 1;

Receiving distribution panel TWR8/16-450 1;

Stationary antenna ANT 450 D6 - 9 (gain 6-9 dB) 2;

Coaxial cable RK 50-7-58 70m;

Connector for RK 50-7-58 2;

Lightning arrester 1;

Adapter cables 8.

Trunking radio stations from TAIT ELECTRONICS LTD:

Wearable T3035;

Mobile T2050.

It is most advisable to build small multi-zone systems with centralized control and connection to a telephone exchange on the basis of the TAITNET system from TAIT Electronics.

The TAITNET system consists of a regional control center, a system control terminal, base stations and user equipment. A typical functional diagram of a four-zone trunking communication system TAITNET is presented in the block diagram (Figure 11).

7.2 Block diagram of a multi-zone trunking system

The system consists of a regional control center, a system control terminal, base stations, and user equipment. The regional control center includes: a regional controller, a switch and interface boards.

Regional controller (T1530 regional control processor), which combines all T1510 base station controllers into a single multi-channel multi-zone system. This controller can control a system consisting of 10 zones with 24 channels in each zone. It collects information from all connected BSs and transmits it to the system control terminal.

The system control terminal is an IBM-compatible personal computer and operates using special software T1504 from TAIT Electronics.

The T1560 switch consists of a switching matrix and interface cards. It provides switching of audio channels during interzone connections and audio channels with telephone lines.

T1560-03 interface cards provide interface with two-wire telephone subscriber lines. T1560-02 boards provide connection of the T1560 switch to BS traffic channels via dedicated four-wire lines.

If the TAITNET system operator has subscriber capacity on the PBX, then it is possible to organize a unified numbering of telephone network subscribers and trunking system subscribers. The organization of general numbering is provided by the trunk controller.

The base station equipment consists of antenna-feeder equipment, T850 transceivers, T1510 channel controllers and T1520 system interface.

BS controllers maintain a communication session and interact with the system interface. The system interface checks and records connections, provides information about the state of the system and exchanges data with BS controllers. Communication with the regional control processor is provided via dedicated two-wire lines via a modem. To connect BS subscribers with the regional node, 4-wire audio lines are used. Control and management of base stations is carried out by a regional controller.

Each knowledge base also has a system controller. Communication between base station system controllers is carried out using modems. Interface cards in the regional control center provide access to the public telephone network.

Literature

1. Guidelines and assignment for a course project on the subject "Communication systems with moving objects"

2. Lecture notes on the subject "Communication systems with moving objects"

3. Catalog "Systems and radio communications", 1998

4. Radioma equipment catalog, 1999

5. Summary table of characteristics of MRT-1327 trunking radios

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