Structural diagram of the contact network as an object of diagnostics. Coursework: Designing an educational local area network Structural diagram of a local area network

To organize data transmission over power networks, the transmitted information undergoes the same transformations as when transmitting data over telephone network common use. That is, the transmitted information at the transmitting end undergoes coding, digital-to-analog conversion and modulation, and at the receiving end - demodulation, analog-to-digital conversion and decoding.

Since each subscriber of the data transmission system is both a source and a recipient of information, it is necessary to organize the transmitting and receiving parts of the system on each PC. It is convenient to organize this by using the same internal and external interfaces for the transmitter and receiver. Thus, the generalized block diagram of the data transmission system on one PC will look like this (Fig. 3.1).

Figure 3.1 - Generalized scheme of the data transmission system

From fig. 3.1 shows that transmitted information v digital form enters the data transfer device through the internal interface. The internal interface serves to separate from the entire data stream that is transmitted over the internal data bus of the PC, those that are intended for transmission to the communication line. The allocation process occurs in accordance with the address information transmitted on the address bus. It follows from this that the internal interface ensures that only the data that needs to be transmitted over the communication line enters the transmitting device. In the same way, the data received by the receiver is transferred via an internal interface to a PC for further processing.

Front end serves to coordinate the device for transmitting and receiving data with the communication line. It performs the functions of separating signals in directions, adapting signals to the transmission medium, decoupling by voltage, matching resistances in the line and linear path, and isolating only the useful signal.

The processes of encoding, decoding, digital-to-analogue and analog-to-digital conversion, as well as modulation and demodulation are performed by a microprocessor system. This system incorporates read-only memory (ROM), which contains software that provides the performance of certain functions of the microprocessor system. It also includes random access memory (RAM) and reprogrammable read only memory (PROM). RAM is used to store intermediate results of calculations, key data. Temporary algorithms for the operation of the microprocessor system are entered into the PROM. All transformations to which the signal is subjected are performed in the microprocessor (MP) itself. The microprocessor used has special requirements. Since the main mathematical operation in the implementation of encoding and decoding algorithms is floating-point multiplication, when using classical MT, the complexity of writing programs and their execution time increase dramatically. Today, digital signal processors, also called DSP controllers, are widely used in digital signal processing. The main advantage of these DSP controllers is the ability to perform single-cycle multiplications, additions, the presence of specific commands, such as binary inversion. The use of such a DSP controller dramatically reduces the requirements for its performance, which has a positive effect on the price of the system. Using in microprocessor system, along with the usual microprocessor, DSP controller, you can redistribute the functions performed. So MP is engaged in the organization of data exchange via the data bus with the PC, generating and receiving address information via the address bus, that is, it performs the functions of an internal interface. Since the speed of the DSP controller is much higher than the MP, it performs the functions of encoding, decoding, digital-to-analog and analog-to-digital conversion, as well as modulation and demodulation.

The external interface is organized by several devices that each perform their own function. An adaptive equalizer is used to adapt the signal to the communication line. An echo canceller is used to separate signals by direction. Connection device that performs following features: cuts off the industrial frequency and passes only a useful high-frequency signal, serves as a barrier device for high voltage, serves as a matching element between the high-frequency cable and the linear path, since the wave impedance of the cable is not equal to the characteristic impedance of the linear path.

Thus, the general block diagram of the data transmission system over the power grid has the following form (Fig. 3.2), where, UE is the connection device, SHA is the address bus, SD is the data bus.

Figure 3.2 - Structural diagram of the system for transmitting information over power networks

Based on this scheme, it is possible to give a block diagram of the transmitter (Fig. 3.3).

The functioning of the MP is carried out according to the algorithm recorded in the ROM and PROM. The data that is analyzed by the microprocessor is stored in RAM. After performing all the necessary operations on the data, the RAM is cleared in order to accept other data. The principle of operation of the encoder depends on the coding method, which is selected from the condition of obtaining the minimum error probability and maximum noise immunity. Modulation should ensure the transfer of the useful signal spectrum to the frequency range where it will be least affected by interference. The data rate and maximum noise immunity also depend on the modulation method. Therefore, the main parameters of the data transmission system as a whole depend on the choice of the type of modulation.

Figure 3.3 - Structural diagram of the transmitter

Since data transmission is carried out in four frequency bands, which are located quite close to each other, it becomes necessary to limit the spectra of transmitted signals within the frequency band. Limiting is done so that signals transmitted in one band do not affect signals transmitted in another frequency band. To limit the spectra, band-pass filters are used, each tuned to its own resonant frequency.

Management of the processes occurring in the microprocessor and DSP-controller occurs with the help of drivers that are supplied with the microprocessor and DSP-controller from the manufacturer.

A structured cabling system is a set of switching elements (cables, connectors, cross panels and cabinets), as well as a technique for sharing them, which allows you to create regular, easily expandable communication structures in computer networks.

A structured cabling system is a kind of "constructor", with the help of which the network designer builds the configuration he needs from standard cables connected by standard connectors and switched on standard cross panels. If necessary, the configuration of connections can be easily changed - add a computer, segment, switch, remove unnecessary equipment, and also change the connections between computers and switches.

When building a structured cable system it is understood that every workplace in the enterprise must be equipped with sockets for connecting a phone and a computer, even if this is not necessary at that moment. That is, a good structured cabling system is built redundant. This can save money in the future, since changes to the connection of new devices can be made by reconnecting already laid cables.

According to the task, the block diagram of the location of buildings, each of which has its own subnet, is shown in Fig. 2.1.

Figure 2.1 - Block diagram of the location of buildings

The block diagram of the subnetworks of each of the buildings is shown in fig. 2.2 - 2.3. Since there are two 5-storey buildings, and they have the same number of switching equipment and PCs, their block diagrams are identical.

Figure 2.2 - Structural diagram of the subnetwork of a 5-storey building

Figure 2.3 - Structural diagram of the subnetwork of a 4-storey building

The block diagram of connecting subnets into one network is shown in fig. 2.4.

Figure 2.4 - General block diagram of the network

In buildings, the technology is FastEthernet, between buildings - FDDI, Internet access from each building via a radio channel.

3 Equipment and cable selection

3.1 Switch selection

A switch is a device designed to connect several nodes of a computer network within one or more network segments. The switch operates at the data link layer of the OSI model. Unlike a hub that distributes traffic from one connected device to all others, a switch only forwards data directly to the recipient. This improves network performance and security by eliminating the need for other segments of the network to process data that was not intended for them.

In this course project, in each room of the buildings there are room switches - workgroup switches, on each floor - a floor switch that combines the workgroup switches of its floor, and the root switch located in the server room on the first floor, to which the switches of all floors are connected.

Switching equipment (switches, routers) was selected from the manufacturer Cisco. According to the Dell "Oro Group, Cisco occupies 60% of the global network equipment market, that is, more than all other competitors. This manufacturer has the widest line of all network solutions, a wide range of technologies, protocols, ideologies, both standard and and our own, allowing you to expand the capabilities of the network, the broadest troubleshooting capabilities built into almost all Cisco devices.

Based on the optimal ratio of price, performance and functionality, the following models of switches were selected, belonging to the Cisco 300 series, designed specifically for small businesses. The line includes a range of low cost managed switches that provide a powerful foundation for maintaining a corporate network.

Cisco 300 Series Switch Features

provide high availability and performance needed for mission-critical business applications while reducing possible time just me.

allow you to control network traffic using modern features such as quality of service analysis, static routing of the third layer, support for the IPv6 protocol.

have clear tools with a web interface; the possibility of mass deployment; similar functions in all models.

allow you to optimize energy consumption without affecting performance.

3.1.1 Workgroup switches

According to the task for the course work in a 4-storey building in three rooms on each floor there are 35 computers, and in two 5-storey buildings in one room on each floor there are 31 computers, for connecting which the SG300-52 switch is selected, which has 48 ports (Figure 3.1).

Figure 3.1 - Workgroup switch SG300-52

Switch SG300-52 (price: 7522 UAH), manufactured by Cisco, is equipped with 48 10/100/1000 Mbps ports for Ethernet networks with automatic speed negotiation for RJ45 ports, which facilitates installation of the device.

This switch provides good performance and can improve workgroup performance and network and host throughput, ensuring easy and flexible installation and configuration. Due to the compact size of the body, the device is ideal for placement on a limited desktop space; also the device can be mounted in a rack. Dynamic LEDs display the switch's real-time status and allow basic diagnostics of the device's operation.

The main technical characteristics of the SG300-52 switch are presented in Table 3.1.

Table 3.1 - Technical characteristics of the switch SG300-52

For two 5-storey buildings, which have 18 and 25 computers in the remaining rooms on each floor, respectively, 18 computers are selected for connection - a switch for 24 ports - SF300-24P (price: 4042 UAH), and for connection 25 computers - two switches, each for 16 ports - SG300-20 (price: UAH 3023), which are shown in fig. 3.2. The remaining ports are reserved.

Figure 3.2 - Workgroup switch SF300-24P (a) and SG300-20 (b)

The SF300-24P is a 24-port managed network switch. These switches provide all the features you need to run mission-critical business applications, protect confidential information, and optimize bandwidth for more efficient network transmission. Plug-and-play and auto-negotiation support allow the switch to automatically detect the type of connected device (such as an Ethernet network adapter) and select the most appropriate speed. LED indicators are used for cable connection control and standard diagnostics. The switch can be desktop-mounted or rack-mounted.

Designed for small workgroups, the SG300-20 is equipped with 18 10/100/1000BASE-TX Ethernet ports and 2 mini-GBICs. The functionality of these switches is similar to the functionality of the SF300-24P switch, since they both belong to the same Cisco 300 series.

The main technical characteristics of the SF300-24P switch are presented in table 3.2, and the SG300-20 switch - table. 3.3.

Table 3.2 - Technical characteristics of the SF300-24P switch

Table 3.3 - Technical characteristics of the SF300-20 switch

3.1.2 Floor switches

To connect workgroup switches, storey switches are used, for which the SRW208G-K9 switch (price: UAH 1483) is selected, which has 8 ports (Fig. 3.3).

Figure 3.3 - Floor switch SRW208G-K9

The SRW208G-K9 switch is equipped with 8 RJ45 ports for Fast Ethernet, 1 Gigabit Ethernet port, and two SFP (mini-GBIC) ports that operate in auto-configuration and speed-sensing mode.

The Cisco Catalyst 2960 is a series of new Fixed Configuration Smart Ethernet Switches. They provide the need for data transmission at a speed of 100 Mbps and 1 Gbps, allow the use of LAN services, for example, for data transmission networks built in corporate branches. The Catalyst 2960 family delivers high data security with built-in NAC, QoS support, and a high level of system resiliency.

Key Features:

High security, advanced access control lists (ACLs);

Organization of network control and optimization of bandwidth using QoS, differentiated rate limiting and ACL.

To ensure network security, the switches use a wide range of user authentication methods, data encryption technologies and organization of access control to resources based on the user ID, port and MAC addresses.

Switches are easy to manage and configure

An auto-configuration feature is available via Smart ports for some specialized applications.

The main technical characteristics of this switch, manufactured by Cisco, coincide with the characteristics presented in Table. 3.2. for a switch from the same company.

3.1.3 Root switches

To connect floor switches, root switches are used, for which a switch was chosen in each building - SG300-20, which has 16 ports. This switch was also chosen as a switch of the working group, its description is presented in clause 3.1.1.

3.2 Selecting routers

A router (router) is a device that has at least two network interfaces and forwards data packets between different network segments, making forwarding decisions based on information about the network topology and certain rules set by the administrator.

Routers help reduce network traffic by dividing it into collision or broadcast domains, and by filtering packets. They are mainly used to combine networks of different types, often incompatible in architecture and protocols. Often a router is used to provide access from local network to the Internet, performing the functions of address translation and firewall.

To connect buildings to one network, a router is used, which was chosen as Cisco 7507 of the 7500 series (price: UAH 121,360), which has the ability to connect an FDDI module (Fig. 3.4).

Figure 3.4 - Cisco 7507 Router

This router was chosen based on the ability to connect an FDDI module, the optimal price from the entire line of this series, and the fact that the Cisco 7500 series modular routers are the most powerful Cisco routers. They meet the highest requirements for modern data networks. The flexible modular architecture of this series of routers makes it possible to use them in large network nodes, choosing the best solutions.

The Cisco 7500 series consists of three models. The Cisco 7505 has one Route/Switch Processor (RSP1= Route/Switch Processor), one power supply, and four interface processor slots (5 slots total). The Cisco 7507 and Cisco 7513, with seven and thirteen slots respectively, provide more bandwidth and can be configured with two RSP2s or PSP4s and a redundant power supply. Combined with the new, redundant CyBus, the Cisco 7507/7513 routers offer unsurpassed performance and reliability capabilities. This is achieved through a new, distributed multiprocessor architecture that includes three elements:

Integrated Routing and Switching Processor (RSP);

New Versatile Interface Processor (VIP);

New high-speed bus Cisco CyBus.

In a dual RSP (Integrated Routing and Switching Processor) configuration, the Cisco 7500 distributes functions between the primary and secondary RSP, increasing system performance, and if one of the processors fails, the other takes over all functions.

The Cisco 7507 Router is a modular router designed for the backbone of large networks and works with virtually all LAN and WAN technologies and all major network protocols.

The Cisco 7507 series supports a very wide range of connections, including: Ethernet, Token Ring, FDDI, Serial, HSSI, ATM, Channelized T1, Fractionalized E1 (G.703/G.704), ISDN PRI, Channel Interface for IBM mainframes.

The network interfaces reside on modular processors that provide a direct connection between the high-speed Cisco Extended Bus (CxBus) backbone and the external network. Seven slots are available for front-end processors on the Cisco 7507. Hot-swap capability allows you to add, replace, or remove CxBus processor modules without interrupting network operation. For storage of information standard Flash-memory is used. All models come with a standard 19" rack mount kit.

There are such communication interface modules:

Ethernet Intelligent Link Interface - 2/4 Ethernet ports with high-speed filtering (29000 p/s), support for Transparent Bridging and Spanning Tree algorithms, configurable using the Optivity system;

Token Ring Intelligent Link Interface - 2/4 Token Ring 4/16 Mb/s ports;

FDDI Intelligent Link Interface - 2 ports supporting two SAS connections or one DAS connection, filtering at up to 500,000 p/s;

ATM Intelligent Link Interface.

3.3 Cable selection

Cable - a construction of one or more conductors (cores) isolated from each other, or optical fibers enclosed in a sheath. In addition to the actual cores and insulation, it may contain a screen, power elements and other structural elements. The main purpose is the transmission of a high-frequency signal in various fields of technology: for cable television systems, for communication systems, aviation, space technology, computer networks, household appliances etc. When using switches, the Fast Ethernet protocol can operate in duplex mode, in which there are no restrictions on the total length of the network, but there are restrictions on the length of the physical segments connecting neighboring devices (switch-adarter and switch-switch).

On assignment, Fast Ethernet technology with 100Base-TX specification was used inside the buildings, unshielded as a communication line twisted pair(UTP) 5 categories.

Between buildings - FDDI technology, as a communication line is used

optical cable for outdoor installation.

Indoor UTP cable, 2 pairs, category 5, is used in subscriber wiring when providing access to data network services. For laying, a cable from the manufacturer Neomax - NM10000 (Fig. 3.4) was chosen due to its high strength and long service life, its characteristics are presented in table 3.4.

Figure 3.4 - UTP, 2 pairs, cat. 5f: 1 - Outer shell; 2 - Twisted pair

Table 3.4 - Main characteristics of the UTP cable, cat.5

3.4 Selecting wireless equipment

Each building uses a radio channel to access the Internet. The Maximus Sector 515812-B directional antenna was chosen as the antenna on the BPS (Fig. 3.5, a), and on the buildings, the TP-Link TL-WA7510N WiFi access point was selected as an external access point (Fig. 3.5, b). This equipment was chosen for the optimal ratio of price and functionality.

The 5GHz frequency band was chosen as the operating range, since the 2.4GHz band is more saturated (loaded) due to the ubiquity of wireless networks. This frequency is used by: the old standard 802.11b, the recently departed 802.11g and 802.11n. Whether you are using 802.11b, 802.11g, or 802.11n, you are transmitting data over the same channel. Another disadvantage of 2.4 GHz is the presence of “side noise” in the wireless channel, which degrades the channel throughput, since it shares the spectrum with many other unlicensed devices - microwave ovens, mini-monitors, cordless phones, etc. Also, the number of used radio channels in the range 2.4GHz is limited. The 5 GHz band is less crowded and has more usable channels at the expense of a slightly shorter coverage area.

Figure 3.5 - Wireless equipment: a) antenna; b) hotspot

Model TL-WA7510N (price: 529 UAH) is a long-range outdoor wireless device operating in the 5 GHz frequency band and transmitting data wirelessly at speeds up to 150 Mbps. The device has a dual polarized antenna with a gain of 15 dBi, which is a key element for building Wi-Fi connections over long distances. It is designed to transmit a signal with radiation angles of 60 degrees horizontally and 14 degrees vertically, increasing the signal strength by concentrating the radiation in a given direction.

Thanks to the all-weather housing and the thermal stability of the internal hardware, the access point can operate in various environmental conditions, in sunny or rainy weather, in strong winds or in snowfall. Built-in ESD protection up to 15KV and lightning protection up to 4000V can prevent power surges during a thunderstorm, which guarantees the stability of the device. In addition, the device has a ground terminal for a more professional level of protection for some advanced users.

The device can work not only in the access point mode. The TL-WA7510N also supports AP client router, AP router, bridge, repeater and client operating modes, which can greatly expand the scope of the device, provide users with the most versatile product possible.

Powered by a PoE injector, an outdoor access point can use an Ethernet cable to simultaneously transmit data and electricity to wherever the access point is up to 60 meters away. This feature increases the placement options for the access point, allowing you to place the access point in the most suitable location for receiving best quality signal.

The main characteristics of the TL-WA7510N are presented in Table. 3.5.

Table 3.5 - Characteristics of TL-WA7510N

Sector antenna Maximus Sector 515812-B (price: 991 UAH) of vertical polarization is made in an antenna housing made of UV-resistant plastic with cast aluminum bracket. High-quality materials allow the antenna to be used in harsh weather conditions. It can be used for small, medium and large base stations. The antenna gives out a strong and stable signal at medium and long distances. The main characteristics are presented in table. 3.6.

Table 3.6 - Technical characteristics of Maximus Sector 515812-B

Based on the scheme of information flows, the separation of these flows, and the scheme of information flows, taking into account servers, also knowing the location of buildings and their dimensions, we will draw up a structural diagram of the corporate network (IN THE APPENDIX) and give its brief description.

Organization of communication with branches.

In this section, it is necessary to describe the type of communication with branches given by the teacher in the following sections: theoretical description of the given method, equipment that allows organizing this communication on the receiving and transmitting sides.

Distribution of addresses of workstations, taking into account block diagram.

V this section it is necessary to divide the network into several subnets based on the block diagram of the network. Define IP addresses for subnets (for servers and PCs), mask and broadcast addresses. Use a non-class model to allocate addresses.

Choice of network protocols.

Select the network protocols that will be used in the developed network and what functions based on these protocols will be performed.

Selection of active and passive equipment of the corporate network.

Types of cables used.

The most commonly used means of communication are twisted pair, radio channel and fiber optic lines. When choosing the type of cable, the following indicators are taken into account:

1. The cost of installation and maintenance;

2. Speed ​​of information transfer;

3. Restrictions on the value of the information transmission distance (without additional repeater amplifiers (repeaters));

4. Security of data transmission.

The main problem is to achieve these indicators at the same time, for example, the highest data transfer rate is limited by the maximum possible data transfer distance, which still provides the required level of data protection. Easy scalability and ease of expansion of the cable system affect its cost and data transmission security.

Select cable types for the network.

To select the type of cable, and hence the type network technology and, accordingly, the equipment, you need to know what load will be on this communication channel. The length of this channel and the environmental conditions in which this channel will be located.

Calculate the load on communication channels. This requires the data from the tables in the first chapter, as well as the block diagram of the network.

Switch selection.

Switches are:
1. A multi-port device that provides high-speed packet switching between ports.
2. In a packet-switched network, a device that directs packets, usually to one of the backbone network nodes. Such a device is also called a data switch.

The switch provides each device (server, PC, or hub) connected to one of its ports with the entire network bandwidth. This improves performance and improves network response time by reducing the number of users per segment. Like dual speed hubs, the latest switches are often designed to support 10 or 100 Mbps, depending on the top speed connected device. If equipped with automatic baud rate detection, they can self-adjust to the optimal baud rate - no manual reconfiguration is required. How does a switch work? Unlike hubs that broadcast all packets received on any of the ports, switches only forward packets to the target device (destination) because they know the MAC (Media Access Control) address of each connected device (similar to how the postman at the postal address determines where the letter should be delivered). The result is reduced traffic and increased overall throughput, two factors that are critical given the increasing network bandwidth demands of today's complex business applications.

Switching is gaining popularity as a simple, inexpensive method to increase the available network bandwidth. Modern switches often support features such as traffic prioritization (which is especially important when carrying voice or video on a network), network management functions, and multicast control.

To select switches, you must first calculate the minimum number of ports for each of them. Spare ports must be provided on each switch so that in the event of a failure of one of the used ones, the problem can be corrected as soon as possible and one of the spare ports can be used. This approach makes sense for ports under a UTP cable. For optical ports, this is irrelevant, since they rarely fail.

The number of ports is calculated using the following formula:

where: N is the required number of ports; N k is the number of busy ports.

And rounded up depending on the standard number of ports on the switches.

Next, you can choose specific models switches. We will take, if possible, switches and network cards from the same manufacturer. This will avoid conflicts and also simplify the network setup.

Choice of network adapters.

Network interface cards (NIC, Network Interface Card) are installed on desktop and laptop PCs. They are used to communicate with other devices on the local network. There is a whole range of network cards for various PCs that have specific performance requirements. They are characterized by data transfer speed and network connection methods.

If we consider simply the method of receiving and transmitting data on PCs connected to the network, then modern network cards ( network adapters) play an active role in improving performance, prioritizing critical traffic (transmitted/received information), and monitoring network traffic. In addition, they support features such as remote activation from a central workstation or remote configuration changes, which saves a lot of time and effort for administrators of ever-growing networks.

Selecting the configuration of servers and workstations.

The main requirement for servers is reliability. To increase reliability, we will choose machines with a RAID controller. It can work in two modes: "mirror" and " fast mode". We will be interested in the first mode. In this mode, the data written to the hard disk is simultaneously written to another second similar hard disk (duplicated). Also for servers large quantity RAM (it is not possible to find out how much memory is required, since we do not know the actual size of the databases and the amount of information stored on hard drives). Also, on the server, requests are processed (database servers) of the user, therefore, you need to choose the brand and frequency of the processor better (more) than on workstations.

Structural diagram of the system mobile communications GSM standard is shown in Figure 3.1. The GSM network is divided into two systems: Switching System (SSS) and Base Station System (BSS). V GSM standard functional interfacing of system elements is carried out through interfaces, and all network components interact in accordance with the CCITT SS No. 7 signaling system (CCITT SS No. 7).

MSC Mobile Switching Center serves a group of cells and provides all types of connections that the mobile station needs in the process of operation. The MSC is similar to an exchange and is the interface between the fixed networks (PSTN, PDN, ISDN, etc.) and the mobile communication system. It provides call routing and call control features. In addition to performing the functions of a conventional switching station, the MSC is assigned the functions of switching radio channels. These include "handover", which achieves continuity of communication when the mobile station moves from cell to cell and switching of working channels in the cell when interference or malfunctions occur.

Figure 3.1 - Structural diagram of a GSM mobile communication system

In this diagram, the following are indicated: MS - mobile station; BTS - transceiver base stations; BSC - base station controller; TCE - transcoder; BSS - base station equipment; MSC - mobile switching center; HLR - position register; VLR - move register; AUC - Authentication Center; EIR - equipment identification register; OMC - operation center and Maintenance; NMC Network Management Center.

MSC provides service to mobile subscribers located within a certain geographical area.

The MSC manages the call setup and routing procedures, accumulates data on conversations that have taken place, which is necessary for issuing bills for the services provided by the network.

The MSC maintains the security procedures used to control access to radio channels. The MSC manages location registration procedures to ensure call delivery to roaming mobile subscribers from public switched telephone network subscribers and to maintain conversation when a mobile station moves from one coverage area to another. The GSM standard also provides call transfer procedures between networks (controllers) belonging to different MCSs.

The MSC generates the data necessary for issuing invoices for the communication services provided by the network, accumulates data on conversations that have taken place and transfers them to the settlement center (billing center). The MSC also compiles the statistics needed to monitor and optimize the network.

The MSC not only participates in call control, but also manages the location registration and handover procedures.

Position Register HLR is a database of subscribers permanently registered in the network. Information about the subscriber is entered into the HLR at the time of registration of the subscriber and is stored until the subscriber stops using this communication system and is removed from the HLR register.

The database contains identification numbers and addresses, subscriber authentication parameters, composition of communication services, routing information, subscriber roaming data is recorded, including temporary mobile subscriber identification number (TMSI) data and the corresponding VLR. The long-term data stored in the position register HLR is shown in Table 3.3.

All MSC- and VLR-networks, including those belonging to other networks, have remote access to the data contained in the HLR while providing inter-network roaming of subscribers. If there are multiple HLRs in the network, each HLR represents a specific part of the network's overall subscriber database. Access to the database of subscribers is carried out by IMSI or MS ISDN number (mobile subscriber number in the ISDN network).

HLR can be executed both in its own network node and separately. If the capacity of the HLR is exhausted, then an additional HLR may be added. In the case of organizing several HLRs, the database remains single - distributed. The subscriber data record always remains the only one. Data stored in the HLR can be accessed by MSCs and VLRs belonging to other networks as part of providing inter-network roaming of subscribers.

Table 3.3 - Long-term data stored in the HLR

Move register VLR also designed to control the movement of a mobile station from one area to another. The VLR database contains information about all mobile subscribers located in this moment within the MSC service area. It allows the operation of the mobile station outside the area controlled by the HLR.

When a subscriber moves into the service area of ​​a new MSC, the VLR connected to that MSC requests information about the subscriber from the HLR that stores that subscriber's data. The HLR sends a copy of the information to the VLR and updates the location information of the subscriber. When a subscriber calls from a new service area, the VLR already has all the information needed to service the call. In the case of subscriber roaming to the coverage area of ​​another MSC, the VLR requests information about the subscriber from the HLR to which the this subscriber. The HLR in turn sends a copy of the subscriber's data to the requesting VLR and in turn updates the subscriber's new location information. After the information is updated, the MS can make outgoing/incoming connections.

To ensure the safety of data in the HLR and VLR registers, their memory devices are protected. VLR contains the same data as HLR. This data is stored in the VLR while the subscriber is in the controlled area. The temporary data stored in the VLR is shown in Table 3.4.

Table 3.4 - Temporary data stored in the VLR register

When a mobile station roams, the VLR assigns a number (MSRN) to it. When the mobile station receives an incoming call, the VLR selects its MSRN and passes it to the MSC, which routes the call to base stations near the mobile subscriber.

The VLR manages the authentication procedures during call processing. At the discretion of the operator, the TMSI may change from time to time to complicate the identification of subscribers. Access to the VLR database may be provided through the IMSI, TMSI or through the MSRN. In general, the VLR is a local mobile subscriber database for the area where the subscriber is located. This allows you to eliminate constant requests to the HLR and reduce the time to service calls.

AUC Authentication Center designed to authenticate subscribers in order to exclude unauthorized use of communication system resources. The AUC decides on the parameters of the authentication process and determines the encryption keys of subscriber stations based on a database located in the Equipment Identification Register (EIR). Each mobile subscriber receives a standard subscriber identity module (SIM) for the period of using the communication system, which contains: an international identification number (IMSI), its own individual authentication key K i and authentication algorithm A3. With the help of the information recorded in the SIM, as a result of mutual data exchange between the mobile station and the network, a complete authentication cycle is carried out and the subscriber's access to the network is allowed. The subscriber authentication procedure is as shown in Figure 3.2.

Figure 3.2 - Scheme of the authentication procedure

The network sends a random number (RAND) to the mobile station. on it with K i and authentication algorithm A3 response value is determined (SRES) i.e. SRES = Ki*. The mobile station sends the calculated SRES value to the network. The network checks the received SRES against the SRES , computed by the network. If the values ​​match, the mobile station is allowed to send messages. V otherwise communication is interrupted and the indicator of the mobile station shows that the identification did not take place. To ensure privacy, the calculation of SRES occurs within the SIM. Unclassified information is not processed in the SIM module.

Equipment Identification Register EIR contains a database for authenticating the International Mobile Station Equipment Identity (IMEI). The EIR database consists of lists of IMEI numbers organized as follows:

Whitelist - contains IMEI numbers, about which there is information that they are assigned to authorized mobile stations;

Blacklist - contains the IMEI numbers of mobile stations that are stolen or denied service for any reason;

Gray list - contains the IMEI numbers of mobile stations that have problems that are not grounds for blacklisting.

The EIR database can be accessed by MSCs of this network and can also be accessed by MSCs of other mobile networks.

Center for operation and maintenance of OMS is the central element of the GSM network. It provides management of network elements and quality control of its work. The OMS is connected to other network elements via X.25 packet channels. OMS provides processing of emergency signals intended to alert maintenance personnel and registers information about emergency situations in network elements. Depending on the nature of the malfunction, the OMS ensures its elimination automatically or with the active intervention of personnel. The MN can check the status of the network equipment and the mobile station's call progress. OMS allows you to regulate the load in the network.

NMC Network Management Center allows for rational hierarchical control of the GSM network. The NMC provides network traffic management and network supervisory control in complex emergency situations. In addition, the NMC monitors and displays the status of automatic network management devices. This allows NMC operators to monitor and assist with regional issues. In extreme situations, NMC operators can enforce management procedures such as "priority access" where only high priority (emergency) subscribers can access the system. The NMC controls the network and its operation at the network layer and therefore provides the network with the data necessary for its optimal development.

So, the NMT staff can focus on solving long-term strategic problems related to the entire network as a whole, and the local staff of each OMC/OSS can focus on solving short-term regional or tactical problems.

BSS base station equipment consists of a base station controller (BSC) and transceiver base stations (BTS). The base station controller can manage multiple BTSs. The BSC manages the allocation of radio channels, monitors connections, regulates their order, provides frequency hopping, signal modulation and demodulation, message coding and decoding, speech coding, voice, data and call rate adaptation. The BSS, together with the MSC, performs the functions of clearing the channel if the call does not go through due to radio interference, and also performs priority transmission of information for certain categories of mobile stations.

Transcoder TSE provides conversion of the output signals of the MSC voice and data channel (64 kbps PCM) to the form corresponding to the GSM recommendations on the air interface (Rec. GSM 04.08), with a voice rate of 13 kbps - full speed channel. The standard provides for the use in the future of a half-speed speech channel of 6.5 kbps. The reduction in the transmission rate is provided by the use of a special speech-transforming device that uses linear predictive coding (LPC), long-term prediction (LTP), residual impulse excitation (RPE or RELP). The transcoder is usually placed with the MSC. When transmitting digital messages to the base station controller BSC, stuffing (adding additional bits) of the 13 kbps information flow to a transmission rate of 16 kbps is carried out. Then, the received channels are compressed with a multiplicity of 4 into a standard 64 kbit/s channel. This forms the 30-channel PCM line defined by the GSM Recommendations, which provides the transmission of 120 voice channels. Additionally, one channel (64 kbps) is allocated for the transmission of signaling information, the second channel (64 kbps) can be used for the transmission of data packets conforming to the CCITT X.25 protocol. Thus, the resulting transfer rate on the specified interface is 30x64 + 64 + 64 = 2048 kbps.

Identifiers– a set of numbers that the GSM network uses to determine the subscriber's location when establishing a connection. These identifiers are used to route calls to the MS. It is important that each identification number is unique and always correctly identified. Description of identifiers is given below.

IMSI(International Mobile Subscriber Identity) uniquely describes a mobile station in the global global GSM network. Most transactions within the GSM network are made using this number. The IMSI is stored in the SIM, in the HLR, in the serving VLR and in the AUC. According to the GSM specifications, the length of the IMSI is typically 15 digits. IMSI consists of three main parts:

-MCC

- MNC

- MSIN(Mobile Station Identification Number) - MS identification number.

MSISDN(Mobile Station ISDN Number) is the number of the subscriber that we dial when we want to call him. There can be several of these numbers for one subscriber. The dial plan for MSISDN is exactly the same as the PSTN dial plan:

- SS(Country Code) - country code;

- NDC(National Destination Code) - the national code of the destination (city or network);

- SN(Subscriber Number) - subscriber number.

Each PLMN has its own NDC. In the communication network of the Republic of Kazakhstan NDC+SN called "national significant number". NDCs for mobile networks are designated as DEF and are referred to as the "non-geographic area code". In Russia, several NDCs are defined for each PLMN. The MSISDN number can be of variable length. The maximum length is 15 digits, prefixes are not included (+7). An incoming connection with a Beeline network subscriber is carried out by dialing +7 777 ХХХ ХХХХ or with the code 705.

TMSI(Temporary Mobile Subscriber Identity) - a temporary IMSI number that can be issued by the MS when it registers. It is used to keep the mobility of the mobile station private. MS will always go on the air with a new TMSI number. TMSI does not have a rigid structure like IMSI, its length is usually 8 digits. Since the TMSI is half the size of the IMSI, paging in one cycle is performed for two subscribers, which also reduces the load on the processor. Each time the MS makes a request for system procedures (LU, call attempt or service activation) the MSC/VLR maps the new TMSI to the IMSI, MSC/VLR. transmits the TMSI to the MS, which stores it in the SIM card. Signaling between MSC/VLR. and MS is used only on the basis of TMSI. Thus, the real IMSI subscriber number is not transmitted over the air. The IMSI is used when the Location Update fails or no TMSI is assigned.

IMEI(International Mobile Terminal Identity) is used to uniquely identify a mobile terminal on a network. This code is used in communications security procedures to identify stolen equipment and prevent unauthorized access to the network. According to the GSM specifications, the IMEI length is 15 digits:

- TAS(Type Arrgoval Code) - code of the approved type sample(6 numbers);

- FAC(Final Assembly Code) - the code of the final assembled product,

assigned by the manufacturer (2 digits);

- SNR(Serial Number) - individual serial number(6 numbers).

Identifies completely all equipment, taking into account the TAC and FAC codes.

- Spare is a free number. Reserved for future use.

When this code is transmitted to the MS, the value of this code shall always be "0".

IMEISV(International Mobile Terminal Identity and Software Version number) - provides a unique identification of each MT, and also ensures that the version of the software installed in the MS corresponds to the one authorized by the operator. The software version is an important parameter as it affects the services available to the MS as well as the ability to perform speech coding. Thus, for example, the PLMN needs to know the MS's speech coding capabilities at call setup (eg, half rate/full rate, etc.). These features are displayed using IMEISV, the first 14 digits of which repeat the IMEI, and the last 2:

- SVN(Software Version number) - software version number, allows the MS manufacturer to identify various versions MS type approved software. SVN value 99 is reserved for future use.

MSRN(Mobile Station Roaming Number) - a temporary number needed to route an incoming connection to the MSC in which the MS is currently located. The time of using the MSRN is very short - only the incoming connection is closed, after that the number is released and can be used to make the next connection. MSRN consists of three parts, the same as in MSISDN, but in this case SN means the address of the serving MSC/VLR.

LAI(Location Area Identity) - an area number (LA) that uniquely describes LA within the entire global GSM network. LAI consists of the following parts:

-MCC(Mobile Country Code) – mobile communication code for the country (3 digits);

- MNC(Mobile Network Code) – mobile operator code (3 digits);

- LAC(Location Area Code) - location code, the maximum length of the LAC is 16 bits, which allows you to define 65536 different LAs within one PLMN.

- CGI(Cell Global Identity) is used to identify a particular cell within an LA. Cell identification is accomplished by adding a Cell Identity (CI) parameter to the LAI components. CI has a size of 16 bits.

- BSIC(Base Station Identity Code) allows MS to distinguish between cells with the same frequency. BSIC consists of:

- NCC(Network Color Code) – color code networks. It is used to delimit the coverage areas of operators in those places where the networks of operators overlap each other.

- BCC(Base station Color Code) - the color code of the base station. Used to distinguish between base stations using the same frequency.

Contact network (CS) - complex engineering structure, which has a significant length and a periodic structure, designed for continuous power supply of rolling stock through a sliding contact.

An analysis of the downtime of the rolling stock (RS) of the tram on the line in a number of large cities shows that a fairly common cause of downtime on the line is the failure contact network. Thus, according to the Novosibirsk Department of Transport, up to 7.5% of substation downtime in time terms occurred on the line due to the failure of the compressor station. In this regard, the assessment of the technical condition of the compressor station from the standpoint of reliability is one of the most important tasks.

When analyzing the failures of the CS in Novosibirsk, failures that occurred as a result of extraneous interactions, such as breakage of suspensions by oversized cargo, damage to support structures by vehicles, annealing of wires as a result of accidents at SS, damage to suspensions by faulty pantographs, were identified and excluded. In the course of a preliminary analysis of the statistical material, it was revealed that the main part (79.8% of the total number of failures) are such failures: breakage of the contact wire, tearing of the wire from the clamp, breakage of the flexible cross, damage to intersections.

The analysis of statistical material and data from operational services shows that the catenary is not an equally reliable system, which indicates the need for further improvement of the structures and assemblies of the contact suspension of the tram, in particular crossings. The largest number failures occur at the moment the pantograph passes through special parts and points of suspension and fixation of the contact wire, i.e. as a result of unsatisfactory interaction due to improper adjustment and installation of the suspension, as well as malfunctions of the pantograph.

It should be noted that up to 27.3% of all failures of tram pantographs on the line occur as a result of cuts and increased wear of contact inserts, which, as is known, is largely caused by a violation of the catenary suspension parameters, such as: zigzag sizes, contact wire height above the level rail heads, slopes and rises of the contact wire, arson.

In addition, from the graphs shown in Fig. 4.10, there is a clear dependence of the amount of damage on climatic conditions. Thus, the maximum intensity of failures of the “break of the flexible cross member” type occurs in May and September with the largest daily temperature difference, and for failures of the type of “breakage of the gearbox and tearing of the gearbox from the clamp”, the maximum intensity occurs in June, which is characterized by the highest temperatures.

Rice. 4.10.

Since the CS is a complex electrical object, its reliability as a whole is determined by the reliability of its constituent elements. Therefore, when analyzing the reliability of the COP, it is necessary:

• to determine the influence of the type of suspension and the quality of its maintenance on the reliability of the CS;
• identify elements that have a reduced, compared with others, reliability;
• determine the climatic factors that affect the reliability of the elements.

The main requirement for the compressor station as an element of the maintenance and repair system is the constant compliance of the main parameters with the required level of reliability, operating conditions and intensity of use. Such correspondence can be achieved if the actual reliability indicators of the CS, as well as the parameters of the maintenance and repair system, are formed on the basis of objective information about the technical condition of the CS.

It is possible to determine the technical condition of the COP based on the results of measuring and evaluating a large number of input, internal and output parameters. In practice, to determine the technical condition, it is enough to single out a set of direct and indirect diagnostic signs and parameters that reflect the most probable malfunctions associated with a decrease in performance and the occurrence of failures.

The block-functional decomposition of the CS is shown in fig. 4.11. Vertical decomposition leads to the construction of a hierarchy of links between its constituent components. Four levels are distinguished in this hierarchy: sectional, which includes the section of the contact network; systemic, including supporting, carrying, fixing, linear current-carrying, supporting devices, thermal elongation compensation devices, interfaces and special parts; the subsystem level includes separate assembly units; the fourth level - elemental - includes non-separable parts. This decomposition predetermines the form of subordination of diagnostic goals and algorithms. The horizontal decomposition of the CS allows you to select individual components according to the basic principle of the physical process, functional purpose or the principle of technical execution.

Rice. 4.11.

As an example of the relationship between the elements of the CS in Fig. 4.12 shows diagrams for simple (a) and chain (b) pendants.

When diagnosing each of these systems in a number of several used physical methods diagnostics, it is possible to single out the dominant one, which allows to determine the technical condition of the CS with a sufficient degree of reliability.

During operation, the COP can be in the following main states:

It is serviceable and operable, which means that the Z parameters characterizing the state of its elements and assemblies are within the nominal tolerance field:

Rice. 4.12.

Faulty, but operable, which is due to the output of the parameters of the main elements and assemblies from the tolerance field, but not higher than the limit values:

Faulty and inoperable, therefore, the parameters of the main elements and assemblies are out of tolerance:

The limits of the specified tolerances for existing types of catenary hangers are given in regulatory documents. However, it should be noted that the existing tolerances mainly reflect the state of the suspension through its geometric dimensions in a static state, i.e., in the absence of rolling stock. In mode normal functioning The CS along its entire length is in interaction with the current collectors of the PS, and therefore, it should also be evaluated by indicators characterizing the interaction, taking into account reliability, durability and quality, i.e. contact stability.

The specified level of operational reliability of the CS is supported by the implementation of a system of repairs and adjustments, determined by the regulatory and technical documentation. The existing system of maintenance and repair, aimed at maintaining the efficiency of the COP, includes control the most important parameters contact suspension and their adjustment. However, control measurements show that the technical equipment of individual operations is insufficient and inefficient. In addition, it provides for the control of the CS parameters in a static state, which, given the existing connections, makes it even more difficult to objectively assess its state. Therefore, it is possible to obtain complete and reliable information only through a comprehensive diagnosis of all CS parameters throughout its entire length in the operating mode.