Design of transport telecommunication networks. Course work: Project of a city telephone exchange based on a packet transport network Conditions for designing transport networks

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Introduction

2. Selection of topology

3. Calculation of the number of equivalent flows between network nodes

7. Selecting the type of equipment

Conclusion

Bibliography

Introduction

Constant increase in traffic volumes due to avalanche-like development Internet networks, led to the need to increase the capacity of data transmission channels. Today, SDH transmission systems are already used not only on PSTN backbones, but also at any levels of network hierarchies, including metro and network access points. At the same time, the equipment must be compact for installation in any premises and meet all modern requirements for equipment.

Interest in SDH technology among telecom operators is due to the fact that this technology replaced the methods of pulse-code modulation PCM (PCM) and plesiochronous digital hierarchy PDH (PDH) and began to be intensively implemented as a result of the mass installation of digital telephone exchanges that allow operating 2 Mbit/s streams , and the creation of regional SDH networks.

The advantage of the SDH network is that it can transmit multiplexed streams with a large amount of information and does not require complete demultiplexing when allocating channels in transit sections. Plesiochronic systems used equalizing bits to equalize speeds. In this case, information was lost that indicated the beginning of each tributary block of the lower order. Therefore, to allocate one tributary block, complete demultiplexing of the entire stream was required, as shown in Fig. 1.1.a.

After the tributary block was allocated, the remaining information added at this node, intended for transmission at the next site, was multiplexed again. This required the installation of a “multiplexer-demultiplexer” pair at transit stations, operating in direct communication (in the jargon - “back to back”, back-to-back).

They were intended only for selecting and inserting tributary blocks. This solution greatly increased the cost of the equipment, especially in cases where it was necessary to serve streams with predominantly transit load and a small amount of information that is received or replaced at a given node. SDH provides a significant reduction in hardware costs through the installation of an input/output multiplexer (Add Drop Multiplexer-ADM), which can “unpack” or replace information in a stream without demultiplexing the stream. The operation of such a device in transit mode is shown in Fig. Fig 1.1 b. The cost reduction is due to the elimination of the multiplexer-demultiplexer pair operating back-to-back. Transport networks using SDHMB can be linear or ring. In Fig. Figure 1.2a shows the use of SDHMVB in a linear network for communication between different SDH terminals (in the figure they are indicated by numbers 1, 2, 3, 4). These terminals may be parts of other equipment. For example, they may be interface equipment to routers on another network. In Fig. 1.2, each terminal has an SDH path with other nodes according to the “each with each” principle, as it is conventionally depicted in Fig. 1.2 b. This uses the capabilities of the input/output multiplexer. In Fig. 1.2.a does not show information flows going in the opposite direction. It is assumed that they are formed in the same way as direct ones - through a reverse-directed SDH path using SDHMVB in transit.

Figure 2

The figure assumes that the SDHMB installed at each node extracts information intended for that node and inserts another towards the neighboring node. Thus, I/O multiplexers allow the creation of virtual network topologies.

These considerations suggest that synchronous networks have a number of advantages over asynchronous ones, the main ones being the following:

Network simplification;

Reliability and self-healing of the network;

Flexibility of network management;

Bandwidth allocation on demand;

Versatility of use;

Easy to increase power;

2. Terms of reference for network design

· it is planned to build an SDH network

· in the areas where the SDH network is deployed, 6 digital telephone exchanges are expected to be put into operation;

· it is proposed to connect all stations into a single network using SDH technology;

· Develop a network organization diagram. Calculate the number of component flows between nodes. Justify the choice of transmission rates of aggregate flows. Select the types of multiplexers, cross-connects and linear equipment in the nodes. Select an optical cable.

· Select network protection schemes and justify them.

· Develop a synchronization network diagram.

· Select SDH equipment to implement the designed network, using products from any manufacturer. Provide the complete set of equipment.

Table 1. Distance between nodes in kilometers.

Distance between nodes in kilometers

Table 2. Approximate functions at nodes

Table 3. Required number of digital streams of the designed network.

	Digital streams	Transmission direction

1. Development of a network organization diagram

In accordance with the initial data in Table 1, we build a network organization diagram.

Rice. 1.1. Block diagram of a telecommunications transport network

In order to design the network as a whole, you need to go through several stages, at each of which one or another functional task set in the technical specifications at the design stage is solved. The first of these is the task of choosing a network topology. For this course project, we will choose a mesh network topology (Fig. 1). The mesh topology can have the form shown in Fig. 1. The mesh network consists of two square cells and contains six nodes. Each of them in practice corresponds to an STM-N level multiplexer installed on a digital PBX.

2. Types of network topology

One of the main design tasks is the correct choice

network topology. The standard basic topologies that are most widespread in organizing communications consist of the following set:

Point-to-point topology;

Topology "serial" linear circuit";

Star topology;

Ring topology.

Plesiochronous digital hierarchy (PDH) equipment is used mainly in point-to-point network structures, since the implementation of more reliable ring, branched and other networks using such equipment has proven to be too expensive and difficult to manage.

Synchronous Digital Hierarchy (SDH) equipment can be used in all structures where PDH equipment is also used, but the inherent

SDH features make it particularly attractive for the implementation of highly reliable managed network structures. The features of the basic topologies of real SDH networks are as follows. Point-to-point topology. The point-to-point topology network (Fig. 2.1) is the simplest and is used when transmitting large digital streams over high-speed trunk channels. It can be implemented using terminal multiplexers (TM), both according to a scheme without redundancy of the receive/transmit channel, and according to a scheme with 100% redundancy of the 1+1 type, using the main and backup electrical or optical aggregate outputs (receive/transmit channels) . If the main channel fails, the network can automatically switch to the backup one in a matter of tens of milliseconds.

Topology "series linear circuit". A network topology "serial linear circuit" is used in cases where at a number of points it is necessary to carry out input-output of digital streams. It is implemented using terminal (terminal) multiplexers and input-output multiplexers. In this case, the intermediate point multiplexers are equipped with two STM-N blocks , and in endpoint multiplexers only one such block is installed. This network can be presented in the form of a simple sequential linear circuit without redundancy, or a more complex circuit with redundancy of the 1+1 type. The last version of the topology is called a flattened ring. Star topology. In a star topology network, one of the multiplexers acts as a concentrator, in which part of the traffic is transmitted to the backbone, and the other part is distributed between the multiplexers of remote nodes. Such a multiplexer has the functions of an input-output multiplexer and a cross-switching system. It should be noted that with a general standard set of SDH equipment functions defined by ITU-T Recommendations, multiplexers produced by specific equipment manufacturers may not have a full set of the above capabilities, or may have additional ones.

Ring topology. This topology is typical for SDH networks. The main advantage of the ring topology is the ease of organizing 1+1 protection, thanks to the presence in SMUX multiplexers of two pairs (main and backup) of optical aggregate outputs: east-west, making it possible to form a double ring with counter flows.

The ring flow organization scheme can be either two-fiber (either unidirectional or bidirectional with or without 1+1 flow protection) or four-fiber (usually bidirectional, allowing for various options for protecting data flows). Despite the higher cost of the four-fiber version, it has come into use recently as it provides higher reliability. When organizing SDH networks, the topology of the “ring” type is most often used, which achieves not only high reliability of its operation, but also the ability to maintain or restore (in a very short time of tens of milliseconds) the functionality of the network even in the event of failure of one of its elements or environment transmission - cable. Such networks are called self-healing or “self-healing”. A ring topology can be configured with two fibers (dual ring topology) or four fibers (two dual rings). Route protection in a dual ring, which corresponds to the 1+1 type, can be organized in two ways.

Fig 2.1 Point-to-point topology

Rice. 2.2. "Serial linear circuit" topology implemented on TM and TDM.

Rice. 2.3. Topology "series linear circuit" of the "simplified ring" type with 1+1 protection.

Rice. 2.4 Star topology with a multiplexer as a hub.

Rice. 2.5 Ring topology with 1+1 protection.

3. Calculation of the number of equivalent E1 flows between network nodes

Let's calculate the equivalent number of primary digital streams in accordance with the technical specifications (Table 3).

The equivalent number of primary 2 M flows (E1) is determined from the relations:

2. a digital stream with a speed of 8 Mbit/s (E2) is equivalent to four streams with a speed of 2 Mbit/s (4x2 M);

3. digital stream with a speed of 34 Mbit/s (E3) is equivalent to 16 streams with a speed of 2 Mbit;

4. a digital stream with a speed of 140 Mbit/s (E4) is equivalent to 64 streams with a speed of 2 Mbit.

5. STM-1 is equivalent to 63 streams at 2 Mbit.

Enter the results of calculations of the number of 2 M flows in directions in Table 3.1

Table 3.1. Equivalent number of primary digital streams

Local nodes

Determine the capacity of linear paths between network nodes of the designed transport network.

Present the network topology, taking into account the number of E1 flows in given transmission directions, as in Fig. 3.1.

Enter the calculation results in Table 3.2.

Directions
	Number of equivalent E1 streams

Figure 3.1

4. Selecting cables between network nodes

The capacity of the communication channel and the signal transmission range depend on the type of fibers used in the cable. To transmit information over long distances from 1 to 100 km and beyond, single-mode fiber is used, with different characteristics. For short distances and tasks that are not critical in terms of speed and volume of transmitted information, multimode optical fibers are used.

The number of fibers in a cable may vary. The number of fibers in the cable must be at least 4x. The total number of fibers is determined based on the capacity of digital linear paths, the need for their redundancy, as well as other considerations.

An optical cable can have different designs, allowing for its installation in different conditions. An optical cable intended for external installation must have a temperature range appropriate to the location where it is laid. As a rule, the operating temperature range remains. The cable sheath must provide protection against moisture ingress into the cable. The optical cable for laying in open ground has more powerful armor in the form of a layer of steel wire.

When choosing an optical cable, you should, of course, take into account its cost, since approximately 80% of all capital costs for organizing a communication network are necessary for the purchase of cable and the construction of cable trunks. Taking into account the above, we select single-mode cable type for laying in the ground. For sections A-B, C-D, D-D, E-E with a working wavelength. Losses in the optical fiber are small, which makes it possible to organize communications over significant distances (about 100 km). For sections A-E and B-C with working wavelength. Losses in optical fiber. The operating wavelength will allow you to avoid installing attenuators in short sections, and will also reduce the cost of purchasing cables and optical interfaces of multiplexers.

The main characteristics of standard single-mode optical fiber (ITU-T recommendation G.652) are shown in Fig. 4.1.

Rice. 4.1. Basic characteristics of standard single-mode optical fiber (ITU-T Recommendation G.652)

We use products from ZAO OKS 01, St. Petersburg, cable brand OAS.

Rice. 4.2. Design of cable brand OAS ZAO "Oks-01"

Rice. 4.3. Purpose and main technical parameters

Rice. 4.4. Decoding the code designation

We choose a standard single-mode cable brand OAS-008-E-04-02-20.0/1.0-X-H with 8 optical fibers with an operating wavelength for long and short sections of the network, respectively.

5. Calculation of the required number of multiplexers of all levels

The “ring” topology involves the use of ADM I/O multiplexers in all nodes of the ring.

The ADM input/output multiplexer (Add/Drop Multiplexor) can have the same set of tribes at the input as the terminal multiplexer; it allows the input/output of channels corresponding to them. In addition to the switching capabilities provided by the TM, the ADM multiplexer allows end-to-end switching of output streams in both directions. ADM also allows you to close the receive channel to the transmit channel on both sides (east and west) in the event of failure of one of the directions. Finally, it allows (in the event of an emergency failure of the multiplexer) to pass (in emergency passive mode) the main optical flow bypassing the multiplexer.

The STM level for all ADM multiplexers in the ring is determined by the maximum flow in one of its sections.

In our case, the maximum traffic on the site is V-G is equal 148E1. STM-4 allows you to organize the transmission of up to 252 E1 streams.

Table 5.1. SDH systems

So, first, ADM multiplexers of the STM-4 level must be installed in each of the points.

Let's define optical interfaces at each section.

Table 5.2. Classification of standard optical interfaces

Usage	Inside the station	Between stations
		Short section	Long section
Nominal source wavelength, nm
Fiber type					Rec. G.652 Rec. G.654
Distance, km
STM levels

In short sections V-B and A-E we use the S-4.1 optical interface.

In other cases ( sections A-B, V-G, G-D, D-E) - optical interface L-4.2.

It can be tentatively assumed that the installation of regenerators will be required in sections A-E and D-G. The final conclusion about the need to install regenerators will be made after calculating the length of the regeneration section.

The final choice of the level of multiplexers in the ring, as well as optical interfaces, will be made after determining the protection method.

6. Selection of methods for protecting linear and group paths

Ring topology is widely used to build local and regional transport networks. Protection in ring networks is of the automatic type (networks with self-healing self-healing) with activation of switching in cases of damage and accidental decrease in signal quality.

ADM capabilities allow the formation of ring self-healing networks of two types:

· unidirectional, when during normal communication between nodes A and B, signals from A to B and from B to A follow the ring in one direction.

· bidirectional, when during normal communication between two nodes A and B, the transport stream signal from A to B flows along the ring in the direction opposite to the signal B to A.

In most cases, a bidirectional network ring is more cost-effective because it requires less bandwidth. This is explained by the fact that the same optical fibers are used for signals transmitted at various intersecting sections of the ring network (both in the main and in emergency modes of operation). At the same time, a unidirectional network ring is easier to implement.

A bidirectional ring can be implemented in two versions:

· two-fiber ring

· four-fiber ring.

Bidirectional 2 fiber ring with section switching multiplexing, where each ring section contains 2 fibers (one for TX transmission and one for RX reception), then in each fiber half of the channels will be used in operating mode while the other half will be in use as a reserve. Those. with the selected protection method, for the final determination of the STM level in the ring, maximum amount E1 flows need to be doubled.

148 x 2 = 296E1, therefore, the STM level in the ring has changed to STM-16. At the same time, it is obvious that some of the virtual containers in STM-16 may be unequipped. It is also necessary to use the appropriate optical interfaces S-16.1, L-16.2.

Bidirectional 4-fiber ring with multiplexing section switching, where each ring section has 4 fibers (two for TX transmission and two for RX reception); working and standby streams are directed along two different fibers, both in the TX transmission direction and in the RX reception direction. In this case, all adjacent network elements in the ring must be connected by two cable lines using two pairs of fibers each. The network element equipment must be equipped with four aggregate interfaces. This type of protection will allow you to maintain the STM4 level, while obviously, cable costs will increase significantly, and installing multiplexers with 4 optical interfaces will require additional costs. Four-fiber ring networks will remain operational even if any of the MS multiplexing sections are damaged twice, i.e. are more reliable for protecting large information flows.

From an economic point of view, taking into account the given traffic of the network being developed, it is advisable to use the 2F MS SPRING protection method.

Taking into account the selected 2F MS SPRING protection method, ADM STM-16 multiplexers with 2 optical interfaces each (S-16.1 and/or L-16.2 for short and long lines, respectively, depending on the network section) must be installed in all network nodes.

7. Selecting the type of equipment

Hardware and equipment for SDH transmission systems are offered by many well-known manufacturers, such as ECI Telecom, Alcatel, Siemens, Nortel, NEC and others. Almost all manufacturers are represented on Russian market. For better use and maintenance, it is advisable to choose equipment from one company.

Most of the multiplexers on the telecommunications equipment market have flexible options configuration and allow you to organize the required type of multiplexer depending on the purpose, protecting not only linear paths, but also hardware.

Changing the configuration of a synchronous multiplexer is carried out by installing or removing replaceable modules and reconfiguring using control interfaces.

Due to the high level of standardization of SDH technology, multiplexers are largely unified in terms of basic parameters.

Let's choose the Alcatel multiplexer 1661SM-C. Appearance The 1661SM-C multiplexer is shown in Figure 7.1.

Rice. 7.1. External view of the 1661SM-C multiplexer

The Alcatel 1661SM-C multiplexer is a compact STM-16 level SDH multiplexer based on the G.707 multiplexing algorithm. This multiplexer is an upgrade of the STM-4 1651 SM multiplexer to the STM-16 level. It is possible to use this system in the modes of input-output multiplexer, terminal multiplexer, double terminal multiplexer, regenerator (not fully supported). The use of the 1641 SM-D expansion shelf is supported. The system is compatible with the 1610 OA and 1664 OA optical amplifiers, with amplifier failures handled by a multiplexer.

Control interfaces Q2 (not in all versions), Q3, F are supported.

Rice. 7.2. Structural scheme

The main difference between the 1651SM and 1661SM-C multiplexers from the 1641SM and 1651SM-C is the presence of a dedicated switching matrix in the circuit. The matrix is ​​connected to aggregate and component ports using a four-wire bus with a transmission speed of 38.88 Mbit/s.

Aggregate blocks perform the following functions:

SPI is a synchronous physical interface.

MUX is a multiplexer that performs serial-parallel conversion of STM-4(16) to STM-1 and vice versa.

RST - end of the regeneration section, controls additional RSOH bytes.

MST - the end of the multiplexing section, controls the MSOH bytes.

SA - section adaptation, processes the AUG pointer for line and system synchronization.

HPC high-order path switching allows you to select and connect AU-4 streams from the switching matrix or aggregate port of the opposite direction for placement in STM-4 (16). When using a full matrix, switching of ALL AU-4 occurs through the matrix, i.e. Some HPC functions are performed by the matrix. The full matrix allows ANY connections between aggregate and component ports (including aggregate-to-aggregate and component-to-component).

Component port modules perform the following functions:

PI - physical interface.

LPA- places/extracts the plesiochronic signal into/from the container (C-12, C-3, C-4). LPT is the end of the low-level path, structures the virtual container (VC-12, VC-3, VC-4).

HPA tract adaptation top level, processes the TU pointer (TU-12, TU-3). LPC - low order path switching, switches any STM-1 position through the switching matrix.

PG(SA) - section pointer generator, enters the fixed value of the AUOH pointer.

SA - processes AU-4 data.

MSP PPS - selects between primary/backup paths and east/west side.

The transmultiplexer block contains a plesiochronous multiplexer that generates 16 2 Mbit/s streams from a 34 Mbit/s signal. The resulting 2 Mbit/s streams, along with five more 2 Mbit/s streams, are then placed as usual.

The 155 Mbit/s optical component stream module performs the following functions:

SPI - synchronous physical interface. RST- controls the first three lines of SOH.

MST is the end of the multiplexing section and controls the last five bytes of SOH.

SA - handles the AU-4 pointer.

HPT is the end of the high order path, structures VC-4.

LPC is a low order path connection that switches STM-1 positions and provides connections through the switch matrix.

The 1631 FOX CO thread I/O block allows the input/output of three STM-0 threads. The following functions are performed:

SPI - provides interaction of electrical/optical signals with an external source. On the receiving side, it extracts clock pulses from the signal.

RST - the end of the regeneration section, controls the first three lines of SOH.

MST is the terminal of the multiplexing section and controls the last five SOH sinks.

MSA - multiplexing section adaptation, handles AU.

HPT - the end of the high-order path, controls the overhead byte (POH) in the direction of transmission, structuring the VC-3 virtual container.

HPA - high order path adaptation, synchronizes in the receiving direction the AU-3 pointer and the TU-12 pointers, which can be located in the VC-3 container. LPC - low-order path switching, connects any position of the STM-0 frame, ensuring the interaction of aggregate blocks.

MSP - protection of the multiplexing section, selects the main/backup module.

The main advantage of having a switch matrix is ​​flexible flow switching and simplification of aggregate port maps.

Rice. 7.3. Module location

The STM-16 aggregate interface card (slots 16+17, 20+21) exists in two versions: first and second generation.

Characteristics of the optical interfaces used:

Interface S-16.1 (DIN, SC-PC, FC-PC connectors).

Operating range: 1290-1330 nm

At point S.

Laser type: SLM

Maximum spectral width at -20 dB: 1< нм

Maximum average radiated power: 0 dBm

Minimum average radiated power: -4 dBm

Minimum attenuation coefficient: 10 dB

Between S and R.

Attenuation: 0-13 dB

Dispersion: ps/nm

At point R.

Minimum sensitivity: -18 dBm

Maximum overload: 0 dBm

Maximum loss after point R: 1 dB

Interface L-16.2 HE1 (DIN, FC-PC connectors).

Operating range: 1500-1580 nm

At point S.

Laser type: SLM

Maximum spectrum width at -20 dB:<1 нм

Minimum side mode rejection ratio: 30 dB

Maximum radiated power: +2 dBm

Minimum radiated power: -2 dBm

Minimum attenuation coefficient: 8.2 dB

Between S and R.

Attenuation: 9-24 dB

Dispersion: 1600 ps/nm

Minimum cable loss at point S, including all connectors: 24 dB

Maximum discrete reflectivity between S and R: -27 dB

At point R.

Minimum sensitivity: -28 dBm

Maximum overload: -8 dBm

Maximum loss after point R: 2 dB

Maximum receiver reflectivity at point R: -27 dB

Switch matrix card (main - slot 6, backup - slot 7). It is possible to use one of two options: full matrix (connections at the VC-12 level, any switching), backplane (switching at the VC-4 level in aggregate port cards, port connections: aggregate-to-aggregate, component-to-aggregate, used only with component ports STM-1 and 140 Mbit/s).

21x2 Mbit/s cards are placed only in slots 1, 2, 3 and 5 (backup). I/O of more than 63 threads is provided using the 1641 SM-D expansion shelf. (HDB3, 3 V peak, 75 or 120 ohms, 0-6 dB attenuation at 1 MHz).

Component stream card 3x34 Mbit/s (reserve 1+ N, 1+1, HDB3, amplitude 1 V, 75 Ohm, signal attenuation 0-12.7 dB at 1 MHz).

Component stream card 3x45 Mbit/s (reserve 1+N, 1+1).

Transmultiplexer card 1x34 Mbit/s + 5x2 Mbit/s (reserve 1+N, 1+1).

Component flow map 1x 140/155 (electrical) Mbit/s (reserve 1+N, 1+1; CMI, signal attenuation 0-12.7 dB at 70 or 78 MHz, respectively).

Component stream card 1x155 (optical) Mbit/s (reserve not provided).

Clock generator unit (CRU) main - slot 19, backup - slot 18. There are two versions: regular (stability 1E-6) and improved (stability 0.37E-6).

AUX/EOW header access block (slot 15, not reserved). The WIDE NETWORK version provides transit of a digital voice signal between aggregate ports, the EXTENSION version provides connection to a telephone set.

Equipment controller (slot 22, not reserved). Provides control of a multiplexer, expansion shelf, control of an optical amplifier. Connection to the TMN network via interfaces Q3, F, Q2 (not available in all versions of the multiplexer).

Futurebus bus block (slot 14, not reserved), used when connecting an expansion shelf to transmit control and monitoring information.

Provides protection for multiplexer (EPS) units. For component flows, protection is 1+N or 1+1, the switching is reversible (when a faulty block is replaced or the characteristics of the block return to normal limits, a switch occurs from the protection block to the working block). STM-16 aggregate ports are not protected at the block level. Switching matrix blocks and clock generator blocks are protected 1+1, switching is irreversible (reverse switching from the protection block to the working one is forced).

Line protection - unidirectional MSP.

Path protection - SNCP (reversible and irreversible, recovery time in reversible mode 5 minutes). The protection structure is a unidirectional two-fiber ring. Switching is automatic (path control at the TU-12, TU-3 or VC-4 level). It is possible to use the drop-and-continue method to protect complex mesh networks. In this case, there must be at least two common points between the subnets.

Path protection 2F-MS-SPRING. Two-fiber bidirectional ring. Half of the ring capacity is reserved for reserve; low-priority traffic that is discarded in the event of an accident can be transmitted in the reserve band.

Synchronization.

The clock generator block allows you to connect the following external synchronization signals: clock frequencies of component streams 2 Mbit/s (T2), clock frequency from aggregate ports or STM component streams (T1), clock frequency 2048 kHz from an external generator (T3). The total number of used clock sources is no more than six. Frequency stability in hold mode 1E-6 (0.37E-6 for a unit with thermal stabilization), in auto-generation mode: 4.6E-6.

Control.

8. Selecting equipment configuration

As a result of the configuration, the multiplexer contains main and replaceable units. On their basis, equipment is completed.

Because ADM STM-16 multiplexers are installed in all nodes; configuration comes down to the selection of aggregate optical interfaces (2 aggregate ports are sufficient to ensure 2F MS SPRING protection) and tributary interfaces.

All multiplexers must contain the following basic blocks:

Switch matrix card (primary - slot 6, backup - slot 7) full matrix (VC-12 level connections, any switching)

Clock generator unit (CRU) main - slot 19, backup - slot 18 (stability 0.37E-6)

AUX/EOW header access block (slot 15, not reserved). The WIDE NETWORK version provides transit of a digital voice signal between aggregate ports, the EXTENSION version provides connection to a telephone set.

Equipment controller (slot 22, not reserved). Provides control of a multiplexer, expansion shelf, control of an optical amplifier.

power unit

Composition of replaceable units in units without taking into account redundancy (minimum set):

Input/output of streams A-B, A-D, A-D:

Aggregate ports:

Aggregate interface card STM-16 S-16.1 - 1 pc. (direction A-E) - slot 17

Aggregate interface card STM-16 L-16.2 - 1 pc. (direction A-B) - slot 21

Component interfaces:

Component stream card 1x155 (optical) Mbit/s (reserve not provided).

Input/output of B-C streams:

Transit flows A-B, A-D, A-D:

Aggregate ports:

Aggregate interface card STM-16 L-16.2 - 1 pc. (direction B-A) - slot 21

Component interfaces:

Component stream card 1x155 (optical) Mbit/s - slot9

Input/output of streams B-B, A-C, V-D, V-E:

46E1, 4E3, 1E4, 1STM-1

Transit flows A-G, A-D:

Aggregate ports:

Aggregate interface card STM-16 S-16.1 - 1 pc. (direction B-C) ​​- slot 17

Aggregate interface card STM-16 L-16.2 - 1 pc. (direction V-G) - slot 21

Component interfaces:

Component stream card 21x2 Mbit/s - 4 pcs. - slot 1, 2, 3 (slot 1 on expansion shelf 1641 SM-D)

Futurebus bus block (slot 14, not reserved), used when connecting an expansion shelf to transmit control and monitoring information.

Component stream card 3x34 Mbit/s - 2 pcs. - slot 8, 9

Component stream card 1x155 (optical) Mbit/s - slot 10

Input/output of streams A-D:

Transit flows A-D, B-D, B-E:

42E1, 2E3, 1E4

Aggregate ports:

Component interfaces:

Component stream card 21x2 Mbit/s - 3 pcs. - slot 1, 2, 3

Component stream card 3x34 Mbit/s - 1 piece. - slot 8

Input/output of streams A-D, B-D:

Transit flows B-E:

Aggregate ports:

Aggregate interface card STM-16 L-16.2 - 2 pcs. - slot 17, 21

Component interfaces:

Component stream card 21x2 Mbit/s - 2 pcs. - slot 1, 2

Component stream card 3x34 Mbit/s - 1 piece. - slot 8

Component stream card 1x 140/155 (electric) Mbit/s - 1 pc. - slot 9

Input/output of flows B-E: 6E1, 1E4

There are no transit flows.

Aggregate ports:

Aggregate interface card STM-16 S-16.1 - 1 pc. (direction E-A) - slot 17

Aggregate interface card STM-16 L-16.2 - 1 pc. (direction E-D) - slot 21

Component interfaces:

Component stream card 21x2 Mbit/s - 1 piece. - slot 1

Component stream card 1x 140/155 (electric) Mbit/s - 1 pc. - slot 8

When reserving 1+N component stream cards, slots 1, 2, 3, 4, 8, 9, 10, 11 are intended for working component stream cards, slots 5 and 12 are for backup ones (each for its own group). When reserving 1+1, blocks are divided into adjacent pairs (1+2, 3+4, 8+9,10+11), the card with a higher number is a backup; in this case, slots 5 and 12 are not used. Different configurations of groups are possible (one has 1+1, the other has 1+N)

9. Calculation of the length of the regeneration section

Determining the length of the regeneration section is an important part of the design of a linear FOTS path. After selecting the interface level of the transmission system and the type of optical cable, you can determine the length of the regeneration section for this interface.

As the signal propagates along the optical cable, on the one hand it weakens, and on the other, its dispersion increases. This leads to a limitation of OK's throughput. When designing a fiber-optic line, the length of the regeneration section in terms of attenuation and the length of the regeneration section in terms of broadband must be calculated separately, since the reasons limiting the limit values ​​are independent.

Let's calculate the length of the regeneration section for the STM-16 level equipment interfaces used.

The length of the regeneration section (RS) is determined by two main transmission parameters: attenuation and dispersion of information signals. To estimate the length of the regeneration section, the following expressions can be used:

where: - maximum design length of the regeneration section;

Minimum design length of the regeneration section;

The maximum value of the overlapped attenuation of the equipment, ensuring by the end of its service life an error rate of no more than 10 -10;

The minimum value of the overlapped attenuation of the equipment, providing an error rate of no more than 10 -10 ;

The average value of attenuation of the optical radiation power at the junction between the construction lengths of the cable on the site (0.04 dB/km);

Average construction length at the regeneration site (4 km);

Attenuation of optical radiation power of a detachable optical connector (0.1 dB);

Optical cable attenuation;

n - number of detachable optical connectors in the regeneration section 2 pcs.;

M - system reserve of fiber optic lines along the cable in the regeneration section (2-6 dB).

By broadband:

where: is the resulting dispersion of a single-mode optical fiber;

Width of the spectrum of the radiation source at a power level equal to half the maximum (spectrum width of single-mode lasers, which is indicated for a level of - 20 dBm from the maximum emitted power.), nm;

B - bandwidth of digital signals transmitted along the optical path, MHz.

The criterion for the final selection of equipment or cable is the fulfillment of the following ratio: taking into account the required capacity of the fiber optic line for the future development.

Let's make a calculation for the optical interface S-16.1

The relationship holds.

Since the maximum length of a short section is 20 km, the installation of regenerators in sections A-E and B-C is not required.

Let's make a calculation for the L-16.2 HE1 optical interface.

The relationship holds.

The minimum length of a long line in our case is 50 km, therefore, the installation of attenuators is not required.

The maximum is 85 km, it is obvious that there is also no need to install regenerators.

10. Development of a communication scheme

The communication diagram of the designed SDH network is shown in Fig. 10.1.

Rice. 10.1. Communication organization diagram.

11. Development of a synchronization and network management scheme

Synchronization in the transport network is necessary to eliminate information losses due to slippages that arise due to fluctuations in the clock frequencies of digital equipment generators (electronic switching nodes, digital transmission systems).

SDH networks are synchronized from a primary reference oscillator (PEG) with frequency stability no worse than 10 -11 . To eliminate the accumulation of phase jitter, secondary master oscillators (MSOs) with a frequency stability of no worse than 10 -9 per day are used.

The clock generator block allows you to connect the following external synchronization signals:

· clock frequencies of component streams 2 Mbit/s (T2),

· clock frequency from STM aggregate ports (T1),

· clock frequency from STM component streams (T1),

· clock frequency 2048 kHz from an external generator (T3).

The total number of used clock sources is no more than six. Frequency stability in hold mode (for a unit with thermal stabilization), in auto-generation mode: .

The specified synchronizing signals, except for the last one, operating in the self-oscillation mode, must be synchronized from the primary or secondary sources of reference signals.

The selection of the clock signal source in the equipment is programmed and carried out automatically. In this case, it is possible to automatically select the best quality synchronization source among several (usually at least three). If the clock sources are of the same quality, then the priority of use must be programmed.

The quality level of the clock signal used to generate the STM-N link is indicated by the S1 byte (ITU-T G.704).

There are rules for propagating the clock signal:

1. The multiplexer must transmit the selected synchronization signal quality to all outputs.

2. The quality in the opposite direction is assigned to “do not use”.

3. The selection of a clock signal from signals with equal quality is done by priority (P).

The synchronization circuit (Fig. 11) contains: one primary reference generator PEG (node ​​B) and one secondary source in node D (G.812).

Rice. 11.1. Synchronization circuit

Each network point has at least three synchronization sources, each of which is assigned a quality level and priority.

In point B, the main PEG is assigned the first quality level and the first priority, the reserve PEG is assigned the first quality level and the second priority. The internal source has been assigned the fourth quality level and the fifth priority. In emergency situations, it is possible to receive a synchronization signal from point B (third priority) and from point A (fourth priority). The quality level for these signals in operating mode is the lowest - sixth. The synchronization signal in operating mode is received for points B, D and E, E, A from the main PEG along the outer ring. To avoid a synchronization loop, the signal arriving along the outer ring from point A to point B is assigned fifteenth priority (“do not use for synchronization”).

The multiplexer blocks are controlled by the system controller using board controllers located in each equipment block. Signals from the expansion shelf are controlled and monitored via the Futurebus (IECB). Connection to the TMN network via QB3 and F interfaces (some versions support QB2). The Q3 is connected using AUI and a 10Base2 Ethernet network. Interface F is implemented as an RS-232C port.

Rice. 11.2. Network management scheme

Conclusion

network multiplexer equipment regeneration

The goal of the course project was to acquire practical skills in the calculation and design of transport telecommunication networks. When performing this work, calculations of the load between specified nodes were performed, the structure and methods of protecting the designed network were determined. Equipment was reviewed and selected. Communication, synchronization and control diagrams have been drawn up.

Bibliography

1. Slepov N.N. Modern technologies of digital fiber optic communication networks (ATM, PDH, SDH, SONET and WDM) / N.N. Slepov. - M.: Radio and Communications, 2003. - 468 p.

2. Sklyar B. Digital communication. Theoretical foundations and practical application. / B. Sklyar.

3. Grodnev I.I. "Fiber-optic transmission systems." - M. Radio and communications 1993. - 264 p.

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The time spent by passengers on one-way labor travel around the city is the main criterion for the quality of the transport system. According to the standards in Russia, these costs should not exceed T = 40 minutes in large cities (above 500 thousand inhabitants) and T = 30 million in medium and small cities. The value of transport accessibility should be at least 2.5 for large cities and at least 3.3 for medium and small cities. This criterion is decisive when designing transport networks and route schemes in cities.

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The initial stage is the construction of a planogram of the average distance of residence of the city's population relative to all centers of gravity.

Kilometer zones are constructed on the settlement planogram relative to all centers of gravity of the city. Kilometer zones are squares constructed at intervals of 1.2... p.km. relative to all centers of gravity.

The average distance of residence of the city's population relative to all centers of gravity is determined. Next, the weighted average time spent by the city population on moving relative to the centers of gravity is determined, based on a pedestrian speed of 4.5 km/h. Next, the accessibility of gravity centers in the city is determined.

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To do this, isochronous lines are constructed on the city plan relative to all centers of gravity. Isochrones are built with intervals of 10,20,30, etc. min. All the population of the city living inside the isochronous 10 min reaches the center of gravity of 10 min or less.

Based on the results of the construction, taking into account the current transport system, transport accessibility for the city in question is determined.

If the value of transport accessibility obtained by calculation is less than the required standard, then it is necessary to improve the transport system by, for example, increasing the speed of movement, reducing the traffic interval. Improvements are made until the requirements of the standard are achieved.

Further work includes improving the calculated transport network by choosing the type of transport based on the given costs, environmental requirements, and the choice of rolling stock.

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[Enter text]

Federal State Educational Institution of Higher Professional Education "Petersburg State Transport University"

Department of Electrical Communications

Course project on the topic:

SDH transport network design

St. Petersburg 2012

Synchronous multiplexer, generalized block diagram of an input/output multiplexer (ADM)

The figure shows a generalized block diagram of an input/output digital stream multiplexer (ADM). The controller monitors and controls all multiplexer modules, as well as collects and indicates alarm signals. Via DCC (Data Control Channel) channels, organized using section header bytes D1,...D12, it maintains constant information exchange with other multiplexers in the network, which ensures the operation of a control network superimposed on the primary SDH network. Either a local control system (via an RS-232 interface) or a control system of the TMN (Telecommunications Management Network) standard, for which an Ethernet interface is used, can be connected to the controller. The EOW (Engineering Order Wire) service communication unit is also connected to the controller, which is organized using the E1, E2, F1 bytes of the section headers (in some multiplexers, other bytes can be used for EOW).

Optical units (numbered 1 and 2 in the USA, and West and East in Western Europe) are connected to the switching (cross-connector) matrix, which performs all operational switching of digital streams. Tribute blocks are also connected to the matrix, to which the transmitted digital streams are supplied. In addition to PDH hierarchy streams, input/output of SDH hierarchy streams (in electrical or optical form), as well as Ethernet computer network signals can be carried out.

The main unit of the synchronous multiplexer controller is a processor with appropriate software. Thus, a multiplexer is essentially a specialized computer. The software of the multiplexer currently in production is constantly being developed and improved. As practice shows, during the course of a year approximately 3-5 updated software versions appear, which provide expanded functionality of the multiplexer.

Hardware redundancy

Hardware protection switching EPS (Equipment Protection Switching) is one of the measures aimed at increasing the reliability of the SDH network. In this case, working units of equipment are reserved (switching matrices, tributary units for input/output of digital streams, linear optical units). Since the primary network is being designed, it is necessary to maximize reliability. I use redundancy according to the 1 + 1 principle (one working unit and one backup).

Network Protection Mechanism MSP

To increase the reliability of the designed SDH network, I use MSP (Multiplexer Section Protection) redundancy, which corresponds to G.841. It can be used on a point-to-point network or subnetwork. To implement it, it is necessary to have a backup linear path, as shown in Fig. 2.1. In this case, the SDH signal is simultaneously transmitted along both the main and backup paths. Under normal operating conditions, reception uses the signal transmitted along the main path. In the SDH network, the quality of signal transmission is constantly monitored using the BIP (Bit Interleaved Parity) algorithm. In the event of a significant deterioration in the signal quality of the main receiving path, an emergency APS (Autometic Protection Switching) switch is made to the backup linear path, which is controlled by the KI and K2 bytes of the MSOH multiplexer section header. Obviously, such a switch is accompanied by a communication interruption, but according to existing standards, its duration should not exceed 50 milliseconds. Note that with MSP, the entire group signal transmitted along the linear path is protected.

Selection of synchronous multiplexers

The interaction of nodes of the projected SDH ring network is calculated in Table 1. It indicates the number of digital streams with a speed of 2 Mbit/s that must be organized between network nodes, parameter A corresponds to the summation of the corresponding digital streams vertically, and parameter B corresponds to the summation horizontally.

The table shows:

1) In column B, the total number 100 characterizes the number of digital streams transmitted over the SDH ring;

2) In column A+B, the numbers 45, 42, 39, 38, 36 correspond to the number of 2 Mbit/s ports on each node.

Thus, the minimum acceptable level of the SDH signal transmitted along the ring is STM-1. In this case, to implement this network, it is advisable to use Metropolis ADM (Compact shelf) equipment.

Technical characteristics of the synchronous multiplexer Alcatel-Lucent Metropolis ADM (Compact shelf).

Synchronous multiplexer with linear optical units STM-4 or STM-16, and implementation without units is allowed (with only tributary units). Number of installation places - 5 (one place for a backup unit).

Types of tributary blocks - 2 Mbit/s;

STM-1 (electric);

STM-1 (optical);

The maximum number of 2 Mbit/s ports on one tributary unit is 63.

The maximum number of 2 Mbit/s ports on a multiplexer is 252.

Safety mechanisms: MSP, SNCP, 2/:MS-SPRlNG (for STM-16 units).

Types of linear optical units: L-4.1, L-4.2, L-16.1, L-16.2/3.

Types of optical tributers: S - 1.1, L-1.2, S-4.1, L-4.2.

Rack mounted only.

Accordingly, based on calculations of the interaction of nodes, hardware redundancy and the selected type of network protection mechanism, the configuration of the multiplexers will look like this:

Node 1 Metropolis ADM (Compact Shelf)

Node 2 Metropolis ADM (Compact Shelf)

Node 3 Metropolis ADM (Compact Shelf)

Node 4 Metropolis ADM (Compact Shelf)

Node 5 Metropolis ADM (Compact Shelf)

Optical units and contributors

Optical units and distributors provide transmission of optical signals over single-mode optical fiber, which is used as a guide system on all SDH networks. Depending on the distance and fiber parameters, it is necessary to use different types of these devices, therefore there is a system of designation and standardization of the parameters of optical units and contributors in accordance with ITU-T Recommendation G.957. In accordance with it, the type of unit or contributor is designated as:

Thus, for example, the designation L-4.2 corresponds to an L unit or contributor, level STM-4 and with an operating wavelength in the range of 1.55 µm.

As mentioned above, in order to ensure more reliable operation of the extraction system clock frequency, the signal transmitted along the linear path is subject to scrambling. The NRZ (Non Return to Zero) signal format is used.

In recent synchronous multiplexers, replaceable SFP (Small Form-factor Pluggable) modules are used, which allow the operator to independently change the type of optical unit or contributor (for example, type S to type L).

At the operator's request, for some types of multiplexers it is possible to supply so-called “colored” optical units, the wavelength of optical radiation of which corresponds to the wavelength plan of the WDM transmission system.

Among the parameters of optical units and contributors, the range of overlapped optical attenuation Amin - Amax) and the maximum chromatic dispersion Dmax overcome by it should be highlighted. For example, for an L-4.2 optical tributary manufactured by Alcatel-Lucent and compliant with Recommendation G.957, the overlapped optical attenuation range is 10-24 dB, and the maximum chromatic dispersion Dmax is 2000 ps/nm.

Parameters of optical units and contributors

Type of optical unit or tributer	Energy potential Amin - Atah, dB	Maximum chromatic dispersion Dmax. ps/pm

Optical units with high output optical power are equipped with an automatic laser shutdown system ALS (Automatic Laser Shutdown). This system ensures that lasers in both directions are turned off in the event of damage to the optical fiber and are automatically turned on when the damage is repaired (this preventive measure is aimed at preventing possible damage to the eyes of operating personnel optical radiation emerging from the end of the fiber).

Many optical units provide control of the optical power at the laser output and at the input of the photodiode and control of the direct current of the laser bias, which makes it possible to estimate with acceptable accuracy the amount of total optical attenuation in the linear path and to carry out ongoing monitoring of laser operation.

Determining the type of optical units and optical contributors

The communication range over a single-mode optical fiber is limited by two factors - the attenuation of optical signals and their chromatic dispersion distortions. During the design process, the maximum permissible communication range is first determined, taking into account only the presence of signal attenuation - Lzat. Then the maximum communication range is determined taking into account only chromatic dispersive signals - Ldis. The final value of the maximum communication range - Lmax, taking into account the two limiting factors mentioned above, is calculated as the smaller of the values ​​of Lzat and Ldis.

The value of Lzat is determined by the energy potential of the optical unit or contributor, i.e. the permissible range of total optical attenuation overcome by the unit from the lower Amin to the upper Amax limit of the energy potential, in which normal operation of the synchronous multiplexer is ensured. In this case, the following relation must be satisfied

Data on the energy potential and maximum chromatic dispersion are the passport data of the synchronous multiplexer and are included in the corresponding technical documentation. In the table above, these parameters in relation to various types of optical units and contributors are shown for some samples of equipment from Alcatel - Lucent, which makes it possible to solve the corresponding problem during the design of an SDH network.

Since the minimum permissible level of the SDH signal transmitted along the ring is STM-1, it is necessary to check optical units of type S-1,1; L-1,2.

I'll check the optical unit S - 1.1.

Amax > 0.37 Lzat + (0.1*4) + (1*2) + 3

Amax > 0.37 Lzat + 5.4

12 > 0.37 Lzat + 5.4

6.6 > 0.37 Lzat

Lzat< 17,83 - Не удовлетворяет требованиям.

I'll check the optical unit L - 1.2.

Amax > 0.21 Lzat + (0.1*17) + (1*2) + 3

Amax > 0.21 Lzat + 6.7

28 > 0.21 Lzat + 6.7

21.3 > 0.21 Lzat

Lzat< 101,43 - Удовлетворяет требованиям.

Based on calculations, to build this network, it is more appropriate to use optical units L - 1.2.

Network clock synchronization system

synchronous multiplexer contributor network

The development of digital communication networks necessitates the creation and improvement of a network clock synchronization (TNS) system. The need for TSS arises when digital switching stations are connected to digital transmission systems, i.e. a unified digital network is being created that provides transmission and switching of signals in digital form. The fact is that if the clock frequencies of the master oscillators of jointly operating switching stations differ even slightly, then slippage occurs, i.e. elimination or repetition of one or more bits in a digital signal. They occur due to differences in the writing and reading speeds of buffer devices located at switching stations. With the help of TSS, the clock frequency of signals is set and maintained, which makes it possible not to go beyond the limits established by ITU-T on the frequency of slippages on the network. At the same time, the SDH transport network is used not only for transmitting information digital streams, but also for transmitting synchronization signals of digital switching stations and base stations GSM standard and other external systems for the SDH network.

TSS network operating modes

Existing regulatory documents define four modes of operation of the synchronization network:

1) synchronous;

2) pseudosynchronous;

3) plesiochronous;

4) asynchronous.

Synchronous mode is the normal mode of operation of a digital network. In an ideally operating digital network in this mode, the possibility of slippage is excluded.

Pseudo-synchronous mode occurs under the condition that two (or several) reference generators operate independently on the network, with a frequency stability of at least 1 x 10-11, which corresponds to Recommendation G.811. At the same time, the deterioration in quality for all types of communication will be practically imperceptible (one slip per 70 days). In particular, this mode occurs when two synchronization regions interact.

Plesiochronous mode of operation occurs when the generator of any slave node loses the ability to externally force synchronization. In this case, the generator goes into Holdover mode, in which it continues to generate the mains frequency with forced synchronization. The duration of operation in the holding mode to comply with slip frequency standards must be strictly limited in time (no more than a day during the year). The frequencies of the slave master oscillators used in this mode must comply with Recommendation G.812.

The asynchronous mode is characterized by a significantly larger discrepancy between generator frequencies and is not applicable to Russian communication networks.

This designed network operates in synchronous mode. Connection point for the main synchronization source, node No. 3.

Types of generator devices used on SDH networks. Hierarchical construction of a synchronization network

The following types of generator devices are used on SDH networks:

1) Primary reference oscillators PRC (Primary Reference Clock);

2) Slave master oscillators SSU (Synchronization Supply Unit);

3) SEC (SDH Equipment Clock) network element generators.

The primary reference oscillator PRC is a highly stable oscillator whose long-term relative frequency deviation from the nominal value is maintained not exceeding 1x10-11, which complies with Recommendation G.811. This generator has the highest quality on the synchronization network and occupies the highest level in the hierarchy of generator devices. It is implemented on the basis of a cesium or hydrogen quantum generator. Another way to implement PRC is to use a GPS receiver GPS coordinates(Global Positioning System). In this case, either the NAVSTAR system, administered by the US Department of Defense, or the domestic GLONASS system can be used. Note that PRCs implemented on the basis of GPS receivers can only be used as backup.

A slave master oscillator SSU is an oscillator whose phase is adjusted based on the input signal received from an oscillator of higher or equal quality. There are transit node SSU-T and local node SSU-L, corresponding to Recommendations G.812T and G.8I2L, occupying the second and third levels in the hierarchy. Their frequency stability in the slave mode is 5x10-10 (SSU-T) and 1x10-8 (SSU-L), and in the free oscillation mode 1x10-9 and 2x10-8, respectively.

The SEC NE oscillator meets the requirements of Recommendation G.813 and has a stability of 5x10-8 in slave mode and 4.6x10-6 in free-oscillation mode (synchronous multiplexers with an internal oscillator and higher quality ones are currently being implemented).

From the PRC, synchronization signals must be transmitted to all network elements, the number of which can be very large. Note that when transmitting clock signals from one NE (Network Element) to another, their quality continuously deteriorates due to the accumulation of phase jitter of the significant moments of the digital signal from their ideal positions in time (“jitter” and “vander”). To improve synchronization quality, SSUs are used in a chain of cascaded network elements, which have a very narrow bandwidth and filter out jitter and wander noise.

To limit the accumulation of jitter in long chains of NEs, it is necessary to limit the length and composition of the chain to the following limits:

1) the chain of generators in the network between the PRC and the most remote NE should not contain more than 10 SSUs and 60 SECs;

2) the maximum number of SECs between two SSUs should not exceed 20.

In accordance with the above, the general synchronization scheme of the SDH network has a hierarchical tree structure, providing for both redundancy of PRC and synchronization signal paths. Only forced synchronization of generators is used, otherwise called “master-slave”. At the same time, a certain hierarchy in the distribution of synchronization signals must be observed in the synchronization network: mainly the backbone primary network is synchronized from the PRC, intra-zone networks are synchronized from the backbone network, and local networks are synchronized from the intra-zone or backbone networks.

SSM algorithm. Synchronization loops. Priorities of synchronization sources

As noted above, it is necessary to provide backup sources and paths for synchronization signals on the synchronization network, and automation of the switching process is desirable. On SDII networks, this is achieved through the use of the synchronization status message algorithm - the SSM algorithm, which is based on the use of the S1 byte of the section header of the MSOH multiplexer section.

A synchronization signal source with PRC quality (node ​​3) is connected to the multiplexer located at the beginning of the synchronization chain. Then, in the S1 byte of the outgoing STM-N signal, in bits 5 to 8, the combination 0010 will be written. If the quality of the clock source is SSU-T (node ​​5), then the group 0100 is written in the S1 byte. Thus, neighboring multiplexers can automatically evaluate the SDH signals coming to them from the point of view of the appropriateness of their use for synchronization purposes and select the signal with the highest level of quality.

Figure 2 shows the synchronization chain. The DNU value written in the S1 byte using the combination 1111 means that the incoming signal is prohibited from being used for synchronization purposes. The need to enter the DNU message can be illustrated by the following example.

Let us assume that in the chain in Fig. 2, instead of the DNU message, a PRC message is transmitted from the second multiplexer to the third in the S1 byte. At the same time, in the event of the loss of an external synchronizing signal with real PRC quality, the multiplexer will begin to synchronize using the SDH signal arriving to it. A so-called synchronization loop will occur where the clock signal of a network element is derived from the clock output signal of the same network element. As a result, the clock signal becomes very unstable, which has an extremely negative impact on the characteristics of the SDH transport network, up to complete interruptions in communication. On an SDH network, under no possible operating modes (normal and emergency), synchronization loops should not occur. One of the measures to prevent the occurrence of loops is the transmission of the DNU message in the S1 byte.

The network element can simultaneously receive several clock signals with the same quality level. In this case, to determine the timing source that the network element selects, each timing source is assigned a priority.

Note that quality is a more important parameter than priority. Thus, when selecting a synchronization source, the network element first selects the source with the highest quality level. If there are several sources with the same quality, the choice is made in favor of the source with the highest priority.

Restoring synchronization in case of network failures

Let's consider an SDH network under various synchronization operating modes. Diagram 1 illustrates the operation of this network in normal mode. There are two synchronization sources - the main one (with PRC quality) and the backup one (with SSU-T quality).

Let's consider the emergency operation of the network, corresponding to a cable break in section 3-4. In the event of an accident, a transient process occurs, upon completion of which the synchronization network will take the form shown in Diagram 2. Obviously, in this case the network switches to a backup synchronization source.

There are certain requirements for constructing a synchronization network, and this task belongs to the class of searching for a multicriteria optimal solution. But it should be especially emphasized that the synchronization network must be designed in such a way as to exclude the possibility of synchronization loops, both in normal mode and during all possible network failures.

Bibliography

1. Guidelines on designing SDH transport networks.

2. Lecture notes.

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Design of a transport network based on fiber-optic communication lines for cellular operators of the GSM standard along the Shardara-Arys highway

INTRODUCTION

1.1 Statement of the project problem

1.3 Description of the GSM system

1.4 Methods of organizing a transport network

1.4.1 Satellite communication lines

1.4.2 Wired communication lines

2. Technical part

2.1 Classification of optical communication cables

2.2 Characteristics and calculation of the main parameters of the optical cable

2.3 Calculation of the length of the regeneration section

2.4 Calculation and plotting of transmission levels

3. Working documentation

3.1 General questions on the construction, installation and measurement of fiber-optic lines

4. Life safety

4.1 Analysis of working conditions during laser operation 5. Feasibility study project5.1 Calculation of capital costs

5.2 Calculation of the number of production workers

5.3 Calculation of technical and economic indicators

5.3.1 Calculation of operating costs

5.3.2 Calculation of income from communication services

Conclusion

INTRODUCTION

Creating a modern dynamic market economy with a self-regulation mechanism is impossible without reliable system communications and telecommunications, which is an important factor in the investment climate and an indispensable condition for business development. The current state of the global communications services market is characterized by profound structural changes.

Computerization of telecommunications equipment goes in parallel with the processes of privatization of national communication systems, the emergence of large operator companies on the market, which leads to increased competition. As a result, prices for telecommunications services are reduced, their range is expanded, and users have the opportunity to choose.

Most industrialized countries are intensively switching to digital standard communications, which allows you to instantly transfer enormous amounts of information with a high degree of protection of its content. In global telecommunications, there is a clear trend towards the development of full-service networks built on the basis of packet switching technology.

Currently, the top ten countries that have the most developed communications and telecommunications systems that meet international standards include Singapore, Sweden, New Zealand, Finland, Denmark, USA, Hong Kong, Turkey, Norway and Canada. In the ranking of countries in terms of the level of development of telecommunication systems, Kazakhstan is inferior not only to industrialized countries, but also to many developing countries.

Demand for information technology, modern computers and office equipment have had a significant impact on the dynamics and structure of the global economy in recent years. A real revolution in the field of information technology was the emergence and rapid development of the Internet system, which by the beginning of the third millennium had become one of the leading sectors of the world economy.

In each country, the management of the telecommunications industry has its own specifics. At the same time, the emergence of digital technologies and the massive introduction of services for providing access to the Internet have led to the fact that today almost any telecommunications operator operates not only in the local (regional or national) but also in the global telecommunications services market.

The advent of digital technology has brought about radical changes in the telecommunications industry. Traditional services voice communication began to be replaced by interactive services such as the Internet, data transmission, and mobile communications.

Telecommunications is the most dynamically developing industry and has the potential for long-term economic growth of industries. According to the Agency for Information and Communications, in order to ensure 1% economic growth in modern Kazakhstan, it is necessary to achieve 3% growth in the telecommunications industry. In this case, telecommunications will not only contribute to the development of society and strengthen the security of the country, but will also become the most important source of stable economic growth.

After the simplification of the mechanisms (1999-2000) for licensing, certification and the allocation of private resources to new communication operators, the number of alternative operators providing communication services increased. Almost all traditional wireline operators also provide cellular and paging services and Internet access.

But, despite the changes, the domestic market for communication services remains quite closed. On the one hand, this is due to the huge scale of the country’s territory, thanks to which the main income of telecom operators is formed. On the other hand, Kazakhstan is still outside the world market of international traffic, which until now has been a consequence of the insufficiently high level of digitalization of the main channels and lower quality of communication compared to world standards. increase.

Despite the high rate of implementation modern technologies, the percentage of coverage of the population of the Republic of Kazakhstan with new types of communication, such as cellular communications, paging, and the Internet remains low.

Cellular communications are developing most dynamically. In 1999 alone, the number of subscribers increased by almost 80%. This is due to the gradual increase in the effective demand of the population, as well as the tariff reduction policy pursued by the largest companies cellular communications. According to Western experts, by the end of the first decade of the 21st century, service users mobile communications will be the same as the number of subscribers of public telephone networks.

This diploma project examines issues of organizing (designing) a transport network based on fiber-optic communication lines for cellular operators of the GSM standard along the Shardara-Arys regional highway. The implementation of this project in real life will improve the quality of communication and increase the number of subscribers of cellular operators in remote areas of the region.

1. Analysis of the current situation

1.1 Statement of the project problem

The domestic market for communication services, despite the changes, remains quite closed. On the one hand, this is due to the huge scale of the country’s territory, thanks to which the main income of telecom operators is formed. On the other hand, Kazakhstan is still outside the world market of international traffic, which until now has been a consequence of the insufficiently high level of digitalization of the main channels and lower quality of communication compared to world standards.

Despite the high rate of introduction of modern technologies, the percentage of coverage of the population of the Republic of Kazakhstan with new types of communication, such as cellular communications, paging, and the Internet remains low.

Among the new types of communications, cellular communications are developing most dynamically. In 1999 alone, the number of subscribers increased by almost 80%. This is due to the gradual increase in the effective demand of the population, as well as the policy of reducing tariffs pursued by the largest cellular communication companies. According to Western experts, by the end of the first decade of the 21st century there will be as many users of mobile communication services as there are subscribers of public telephone networks.

The main goal of this project is: improving the quality of communication; increase in income from outgoing traffic; expansion and strengthening of the positions of cellular operators in the communication services market; avoiding the loss of potential consumers of communication services; increasing the cash flow of operators, etc. To achieve the goal, the project considers issues of organizing (designing) a transport network based on fiber-optic communication lines for cellular operators of the GSM standard along the Shardara-Arys regional highway, which will significantly improve the quality of the services provided and accordingly increase the outgoing traffic.

The basis of the project strategy is to satisfy the demand for improving the quality of communications, gaining a leadership position in the provision of telecommunications services, expanding the market, providing consumers in two regions (Aryssky and Shardara) with the most modern, high-quality communication services.

The relevance of the project lies primarily in the fact that existing system communications (the transport network of cellular operators is heterogeneous, i.e. partially analog-digital RRL and electrical cables compacted using PCM), the operation of which has remained unattended over the past years, does not satisfy the needs of the population, both in the quality of communication and in timely installations.

The planned design of a transport network based on fiber-optic communication lines creates the preconditions for stable traffic growth, the provision of high-speed data transmission services, as well as the provision of digital channels for rent to third-party operators.

Due to this, this project is necessary to eliminate all shortcomings in the operation of the telecommunications network, which will affect the increase in the number of subscribers, channels and will bring stable financial growth to the operator, will additionally increase the markets for the provision of telecommunications services, and accordingly will increase cash flow.

Consequently, the timely implementation of this project will allow the expansion of the market for the provision of telecommunications services and will provide a significant advantage in competition with companies that today provide similar services.

1.2 a brief description of region and communication network

The South Kazakhstan region is one of the large regions of the republic and borders on the east with the Zhambyl region, in the north with the Zhezkazgan region, in the west with the Kyzylorda region and in the south with Uzbekistan. Its territory is 117.3 thousand sq. km, about 2 million people live here. The administrative-territorial structure of the region includes 4 cities and 11 rural districts.

The region is rich in mineral deposits such as barite, coal, iron and polymetallic ores, bentonite clays, vermiculite, talc, limestone, granite, marble, gypsum, quartz sands. In terms of uranium reserves, the region ranks first, phosphorites and iron ores - third place in Kazakhstan.

The South Kazakhstan region has significant production and economic potential. This is one of the most labor-abundant regions of Kazakhstan.

The region is a major producer and supplier of cotton, astrakhan fur, leather raw materials, vegetable oil, fruits, vegetables, grapes, melons, confectionery, pasta, tobacco products, beer and soft drinks. The region also produces lead, cement, yellow phosphorus, petroleum products, sulfuric acid, slate, automobile tires, excavators, power transformers, oil switches, cotton fabrics, hosiery, clothing, and furniture.

The region has two lines of railways with a total length of 444.6 km, public roads of 5.2 thousand kilometers, incl. with hard surfaces - 5.1 thousand kilometers. Civil aviation operates on lines with a length of 18.3 thousand kilometers.

The regional center is located on the axis of the international highway Orenburg - Tashkent and the Turkestan-Siberian highway. In addition, it has convenient connections along the highways: Tashkent - Shymkent - Taraz - Almaty and Tashkent - Shymkent - Turkestan - Samara.

The main directions of socio-economic development of the region are the subordination of regional policy to the priorities of sustainable economic development of the real sector of the economy, especially those industries that provide employment by increasing the capacity of the domestic market and expanding effective demand, creating an attractive investment climate, and intensifying efforts to attract direct domestic and foreign investment into priority sectors of the economy. IN social sphere- implementation comprehensive program social protection population, building a system of targeted social protection at the local level and ensuring effective measures to combat poverty and unemployment.

The development of industry is determined by the oil refining and metallurgical industries. In metallurgy, production of refined lead, gold, and silver will stabilize. In the light and food industries, production is expected to almost double, but this will not have a significant impact on the structure of industrial production.

Priority development was given to subjects of the small business manufacturing sector engaged in processing agricultural products. The development of livestock farming will entail the creation of new enterprises for processing leather, wool, meat and milk. Particular attention will be paid to the creation of small enterprises with a complete cycle of processing raw cotton, the development of rice growing and viticulture.

The agricultural development strategy is based on supporting efficient business entities that produce competitive products and expanding the capacity of domestic and foreign markets for domestic agricultural products, creating general economic conditions for stabilizing the industry.

There is an increase in the volume of work of enterprises in the transport and communications complex. Dispatch of cargo by all types of public transport for 2000-2008. increased by 29.6%, including railway transport by 23.1%, road transport by 38.6%, and air transport by 2.5 times. On highways, work will be mainly aimed at improving their technical condition and reconstruction to ensure the passage of heavy vehicles.

The South Kazakhstan region has significant production and economic potential. It is based on huge natural reserves, high industrial potential and sufficient labor resources.

The region is a major producer and supplier of cotton, leather raw materials, vegetable oil, fruits, vegetables, grapes, melons, pasta, tobacco products, beer and soft drinks, lead, cement, petroleum products, sulfuric acid, slate, automobile tires, excavators, power transformers, oil switches, hosiery, garments, furniture.

Today, Southern Kazakhstan is one of the most dynamically developing industrial regions of the republic. The best enterprises in the region are experiencing steady growth in economic indicators. Another evidence of the successful development of the economy was the emergence of new enterprises and the creation of new jobs, primarily in the field of cotton processing. A cotton spinning factory was put into operation. The development of large-scale production is accompanied by an increase in the number of small and medium-sized businesses.

The largest junction station in South Kazakhstan with three directions is Arys station. It was founded in 1900 as a railway station during the construction of the Orenburg-Tashkent railway line. The Arys station is called the “route factory” and the “gateway to Central Asia”, since it is the main dispatcher of the southern highway of Kazakhstan.

There are several operators in the region providing communication services to the population and organizations. Among them the following can be noted: Kazakhtelecom, Kaztranscom, Transtelecom, Nursat, Astel, Golden Telecom, KCeel, Beeline, Dalacom, trunking companies, etc.

The South Kazakhstan Regional Directorate of Telecommunications, a branch of Kazakhtelecom JSC, plays an important role in the development of the regional economy. This organization provides local, long-distance and international telephone services, data transmission and telegraph communications, mobile radiotelephone communications, and services for broadcasting television and sound programs.

Since 1998, the Transnational Asian-European Fiber Optic Communication Line (TAE FOCL) has been operating, passing through the territory of the region. At the end of 2000, the Shymkent-Aktobe section of the Western branch of the National Information Superhighway (NISM) was put into operation, and since 2005, the eastern branch of Shymkent-Taraz.

Work is actively underway to digitalize local networks (GTS, STS), as well as the zonal network. In the city of Shymkent, work on the construction of the NGN network is being completed. Stations are being introduced satellite communications DAMA, providing communications to remote areas. Interest in the Internet has increased in the region.

But there are also problems, for example in the field of communications and telecommunications it is necessary to satisfy the population’s demand for services. Necessary further development work to modernize communication systems by replacing analog equipment to digital, as well as the introduction of new modern standards for cellular, mobile and other types of communications. To intensify work on the construction of secondary segments (intra-zonal and local) of the national information superhighway, to expand the satellite network, as well as to provide cellular communications to remote areas and villages.

Below in Section 1.3 of this thesis design, the main aspects of cellular planning are presented, since the goal of the project is to create a transport network for GSM operators along the Shardara-Arys highway based on fiber-optic communication lines.

1.3 Description of the GSM system

General characteristics of the system. In accordance with the 1980 CEPT recommendation regarding the use of the mobile communications spectrum in the frequency range 862-960 MHz, the GSM standard for digital pan-European (global) cellular system land mobile communications provides for the operation of transmitters in two frequency ranges: 890-915 MHz (for mobile station transmitters - MS), 935-960 MHz (for base station transmitters - BTS).

The GSM standard uses narrowband time division multiple access (NB TDMA). The TDMA frame structure contains 8 time positions on each of the 124 carriers.

To protect against errors in radio channels during transmission information messages block and convolutional coding with interleaving is used. Improving the efficiency of coding and interleaving at low speeds of movement of mobile stations is achieved by slow switching of operating frequencies (SFH) during a communication session at a rate of 217 hops per second.

To combat interference fading of received signals caused by multipath propagation of radio waves in urban conditions, communication equipment uses equalizers that ensure equalization of pulse signals with a standard deviation of the delay time of up to 16 μs.

The synchronization system is designed to compensate for the absolute delay time of signals up to 233 μs, which corresponds to a maximum communication range or maximum cell radius of 35 km.

The GSM standard chooses Gaussian frequency shift keying (GMSK). Speech processing is carried out within the framework of the adopted system of discontinuous transmission of speech (DTX), which ensures that the transmitter is turned on only when a speech signal is present and the transmitter is turned off during pauses and the end of a conversation. A speech codec with regular pulse excitation/long-term prediction and linear predicative coding with prediction (RPE/LTR-LTP codec) was selected as a speech converting device. The overall speech signal conversion speed is 13 kbit/s.

The GSM standard achieves a high degree of security for message transmission; Messages are encrypted using the public key encryption algorithm (RSA).

In general, the communication system operating in the GSM standard is designed for use in various fields. It provides users with a wide range of services and the ability to use a variety of equipment for the transmission of voice and data messages, calling and emergency signals; connect to public switched telephone networks (PSTN), data networks (PDN) and integrated services digital networks (ISDN). The characteristics of the GSM standard are given at the end of the explanatory note [P.A.].

System structure. The GSM network is divided into two systems. Each of these systems includes a number of functional devices, which in turn are components of a mobile radio network. These systems are:

Switching system (SS);

Base station system - Base Station System (BSS).

Each of these systems is controlled by a computer control center.

The SS system performs the functions of call handling and connection establishment, and is also responsible for the implementation of all services assigned to the subscriber. SS includes the following functional devices:

Mobile Switching Center (MSC).

Home Location Register (HLR).

Visiting Register (VLR).

Authentication Center (AUC).

Equipment Identification Register (EIR).

The BSS system is responsible for all functions related to the air interface and includes the following functional blocks:

Base station controller (BSC).

Base station (BTS).

Center Maintenance(OMS) performs all operational and maintenance tasks for the network, for example, it monitors network traffic and alarms from all network elements.

From the OMS, access is provided to both the SS and BSS systems.

MS does not belong to any of these systems, but is considered as an element of the network.

Composition of the SS switching system. Mobile switching center. The Mobile Switching Center (MSC) performs switching functions for mobile communications. This center controls all incoming and outgoing calls coming from other telephone and data networks. Such networks include PSTN, ISDN, public data networks, corporate networks, as well as mobile networks of other operators. Subscriber authentication functions are also performed in the MSC. The MSC provides call routing and call control functions. The MSC is responsible for switching radio channels. These include “handover,” which maintains continuity of communication as a mobile station moves from cell to cell, and switching operating channels within a cell when interference or failure occurs.

MSC generates the data necessary to issue invoices for communication services provided by the network, accumulates data on completed conversations and transmits them to the billing center. MSC also compiles statistical data necessary for monitoring and optimizing the network.

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

The switching center continuously monitors mobile stations using location registers (HLR) and movement registers (VLR).

Reference location register. In the GSM system, each operator has a database (HLR) containing information about all subscribers belonging to its PLMN. This database may be organized in one or more HLRs. Information about the subscriber is entered into the HLR at the time the subscriber registers (the subscriber enters into a service contract) and is stored until the subscriber terminates the contract and is removed from the HLR register.

Stored information in HLR includes:

Subscriber ID.

Additional services assigned to the subscriber.

Information about the subscriber's location.

Subscriber authentication information.

HLR can be implemented either in its own network node or separately. If the HLR capacity is exhausted, then an additional HLR can be added. And 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 to subscribers.

Visiting Register (VLR). The VLR database contains information about all mobile subscribers currently located in the MSC service area. Thus, each MSC on the network has its own VLR. The VLR temporarily stores subscription information so that the associated MSC can serve all subscribers within the MSC's service area. The VLR can be considered a distributed HLR because the VLR stores a copy of the subscriber information stored in the HLR.

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

Authentication Center (AUC). To prevent unauthorized use of communication system resources, authentication mechanisms are introduced to certify the authenticity of the subscriber. AUC - subscriber authentication center consists of several blocks and generates keys and authentication algorithms (passwords are generated). With its help, the subscriber’s credentials are checked and his access to the communication network is provided. The AUC makes decisions about the parameters of the authentication process and determines the encryption keys of subscriber stations based on a database located in the EIR equipment identification register.

Subscriber Equipment Identification Register (EIR). EIR is a database containing information about identification numbers mobile phones. This information necessary to block stolen phones. This register (EIR) is offered to operators as an option, so many operators do not use this register.

Composition of the BSS base station system. Base Station Controller (BSC). The BSC controls all functions related to the operation of radio channels in GSM networks. It is a high capacity switch that provides functions such as MS handover, radio channel assignment and cell configuration data collection. Each MSC can manage multiple BSCs.

Base station (BTS). The BTS controls the radio interface with the MS. The BTS includes radio equipment such as transceivers (receivers) and antennas that are necessary to serve each cell in the network. The BSC controller controls multiple BTSs.

Network monitoring centers. Maintenance Center (OMC/OSS). OMS or OSS is a computerized network monitoring center connected via X.25 data links to various network components, such as MSC and BSC. The center staff is provided with information about the status of the network and can monitor various system parameters and manage them. One network can have one or more centers - it depends on the size of the network.

Network Management Center (NMT). Centralized network management is performed in the Network Management Center (NMT). Only one center is needed on the network, from which the subordinate OMC/OSS can be controlled. The advantage of this centralized approach is that NMT staff can focus on solving long-term strategic problems associated with the entire network, while local staff at each OMC/OSS can focus on solving short-term regional or tactical problems.

The combination of OMC/OSS and NMC functions can be a combination implemented in the same physical network node or in different physical objects.

Mobile station (MS).MS is used by a subscriber of a mobile communication network to communicate within the network. There are several types of MS, each of which allows the subscriber to establish incoming and outgoing connections. MS manufacturers offer subscribers a large number of different devices, differing in design and capabilities, satisfying the needs of different markets.

The coverage range of each mobile terminal depends on its power output. Various types MS have different output power levels and therefore can operate reliably within zones different sizes. For example, the output power of a regular telephone that subscribers carry with them is less than the power of a device installed in a car with an external antenna, therefore, its operating area is smaller.

MS standard GSM consists of the following elements:

Mobile terminal (handset).

Subscriber Identity Module (SIM).

In the GSM standard, unlike other standards, information about the subscriber is separated from information about the mobile terminal. Subscriber information is stored on the SIM card. SIM can be inserted into any device that supports the GSM standard. This is an advantage for subscribers because they can easily change devices at will, which does not in any way affect the subscriber’s network service. In addition, this provides increased subscriber security. The block diagram of the system is given at the end of the explanatory note [P.A.].

1.3.1 Cellular planning aspects

Cellular planning involves several system design phases. At each design stage, various issues of network construction are considered: what equipment to use, where to place it, how it should be configured. In order to obtain an optimal system in terms of radio frequency coverage, it is necessary to carry out cellular planning.

The main aspects of cellular planning include:

System cost;

System throughput;

Coverage (service area);

Probabilities of call blocking;

Analysis of available frequencies;

Connection quality;

Subscriber distribution analysis;

Other factors;

Nominal Cellular Plan;

Selection of base station locations;

Drafting the project;

System construction;

Optimization;

Development.

System cost. Cost of the project cellular network is one of the most important factors. The funds invested in the construction of the network must be repaid within a given period. When designing a specific system, a group of specialists on the technical, financial, and marketing side of the project must develop a business plan in which, based on market conditions, the technical and financial capabilities of the operator, the volume of possible costs and the volume of expected profit from the implementation of a specific project should be assessed.

System throughput. On initial stage When designing a system, system capacity refers to the expected number of subscribers to be served. The network capacity at the design stage must be selected sufficient to satisfy the entire potential capacity of the mobile communications market in the intended region.

Coverage (service area). The radio coverage area of ​​the urban cellular communication network should cover the entire territory of the city, suburban settlements and communication routes.

Probabilities of call blocking. Probability of call blocking or (GoS - Grade of Service) - the percentage of unsuccessful connection attempts caused by network congestion, is calculated using the Erlang B formula and is used to calculate the probability of call blocking for a given load and a given number of traffic channels.

Analysis of available frequencies. When analyzing the frequencies available for planning, the most important point is the assessment of the electromagnetic compatibility (EMC) of the BSS base station subsystem. EMC is considered at two levels:

Intersystem EMC;

In-system EMC.

Connection quality. Quality in cellular communication systems is determined by many factors. When designing, take into account:

Probability of blocking (GOS);

SQI (Speech Quality Index).

Analysis of subscriber distribution. When analyzing subscriber distribution, the following is taken into account:

The density of development of the territory, its unevenness;

The direction and congestion of roads in the area;

Download statistics existing networks PSTN or PLMN.

Other factors. When constructing a PLMN, it is also important to consider:

Possibility of another operator appearing in the region. If such an operator already exists, then its work and pricing policy are assessed, and the disadvantages and advantages of its network are taken into account.

The solvency and material well-being of the population is assessed.

Other technical, economic, social factors that in one way or another influence the planning process.

Nominal Cellular Plan. After collecting data on the expected load and required coverage, a nominal cellular plan is drawn up, which is a graphical representation of the future cellular network, and it looks like a set of cells plotted on top of a geographic map.

A nominal cellular plan is the first stage of cellular planning. Once a nominal cellular plan is obtained, designers begin calculating coverage, frequencies, and interference.

Selection of base station locations. The installation point of the base station is determined based on the service area, network configuration, urban development features, expected parameters of subscriber traffic in the BS service area, the developed topological model of the network service area and the frequency-territorial plan.

When choosing base station locations, the following is taken into account:

Snap to the nominal plan grid;

Object type;

Antenna location;

Spatial diversity of antennas;

Existing obstacles;

Equipment location;

Base station power supply;

Transport network;

Agreement with the lessor.

Drawing up a project. On at this stage design there is all the necessary data for network design:

Coverage information;

Information about the location of base stations;

MSC location information;

BSC location information;

Information about the organization of the transport network.

Based on the available information, a final cellular plan for the construction of the entire system is drawn up, and names are assigned to the objects under construction (BTS, BSC, MSC). In addition, files are being prepared for loading cellular parameters into BSC (Cell Design Data). This data contains information about all launched cells.

Construction of the system. At the system construction stage, it is determined what equipment will be used in the construction of the network and how it will be installed. The types of antenna systems and BTS transceiver configurations are selected. Possibilities for connecting to the company's transport network are analyzed. In the case of using radio relay communication lines, the presence of line of sight in the direction of the radio relay line node or neighboring BTS is also determined. If calculations show that all requirements for coverage and interference are met, then contracts are concluded with the owners of the premises and work is carried out on the installation of the system and its implementation.

Optimization. Once the system is built and operational, a series of measurements are made to determine the system's performance and the energy characteristics of the overall coverage area.

In particular, the following is carried out:

Checking the validity of the final cellular plan;

RF coverage assessment;

Assessing the quality of the system;

Assessing the quality of customer service.

Based on testing and evaluation data, network configuration (optimization) is carried out. Network configuration (optimization) refers to the configuration of logical, energy and interference parameters of the network, which affect the quality of the communication services provided to subscribers.

Development. When analyzing the development path of a system, it is necessary to choose how and where to increase throughput. The main ways of system development include:

Expanding the number of existing base stations frequency range, for example GSM - 900;

Introduction of an additional frequency resource using extended GSM standards (E-GSM, R-GSM);

Using the GSM 1800/1900 standard;

Using additional system options, e.g. hierarchical structure cells in combined GSM 900/1800 systems, which allows for optimal load distribution between two frequency ranges.

Conclusion. As described above, cellular planning includes a complex of activities that require considerable capital expenditure, so timely and correct cellular planning is the key to high-quality communications in the future.

When cellular planning, it is necessary to take into account (regardless of the initial or development of the network) all of the listed aspects.

To solve the objectives of the thesis project, the following sections discuss in detail issues related to the transport network, since the solution to this issue is taken into account when choosing objects for locating base stations along the Shardara-Arys highway.

1.4 Comparison of methods for organizing a transport network

1.4.1 Satellite communication lines

Satellite communications have the most important advantages necessary for building large-scale telecommunications networks. Firstly, with its help you can quickly create a network infrastructure that covers a large area and does not depend on the presence or condition of terrestrial communication channels. Secondly, the use of modern technologies for accessing the resource of satellite repeaters and the ability to deliver information to an almost unlimited number of consumers simultaneously significantly reduce the cost of operating the network.

Any satellite communication network includes one or more relay satellites, through which the interaction of earth stations (ES) is carried out. Currently, the most widely used satellites are those operating in the C (4/6 GHz) and Ku (11/14 GHz) frequency bands. As a rule, C-band satellites serve a fairly large area, and Ku-band satellites cover a smaller area, but have higher energy, which makes it possible to use satellites with small diameter antennas and low-power transmitters to work with them.

Typically, in order to develop an optimal network solution, the cost of several network construction options (based on one or more technologies) is calculated for different load modes. If you plan to develop a network, then in order to correctly select a technology (of course, from among those suitable for providing the telecommunication services necessary for the enterprise), in addition to the cost of implementing the initial version of the network, you should evaluate the total cost of ownership of one user station and the change in this indicator as their number increases. When built, user stations are equipped with one port for data transmission with a traffic of 10 MB per month and one telephone port with a traffic of 1000 minutes per month, and the network has a star topology, in a network with 10 user stations, in the case of using TDM / TDMA technology The total cost of owning one such station for three years will be a fairly high figure of approximately $110,000, but as the network grows it will begin to decline very quickly. In small networks it is much cheaper to use SCPC or TDMA terminals, however, when the number of such terminals becomes more than 50, they are more expensive than TDM/TDMA user stations. It should be noted that the total cost of ownership of a station is greatly influenced by its load.

Many enterprises take the path of creating their own telecommunications departments, entrusting the development, construction and further operation of the corporate network to their employees. At the same time, they gain full control over their networks and save on paying for third-party services. At the same time, enterprises do not always have the opportunity to hire highly qualified personnel with knowledge of the technologies that are expected to be used in the future network, and the additional costs of training such personnel and solving complex problems that often arise during the implementation of the project can significantly exceed the amounts saved. At the same time, operating the network will require obtaining various permits, and this is a rather labor-intensive, expensive and time-consuming procedure. It is easier, and often cheaper, to use the services of a well-known operator who has experience in implementing similar projects and the necessary licenses. If an enterprise wants to independently control and maintain its network, i.e., to be its operator, an external operator can only be used at the stages of development and implementation of a network project. During this time, the enterprise's own specialists will be able to receive the necessary training in order to then take over the administration and maintenance of the entire network.

1.4.2 Wired communication lines

Cable lines are a rather complex structure. The cable consists of conductors enclosed in several layers of insulation: electrical, electromagnetic, mechanical, and also, possibly, climatic. In addition, the cable can be equipped with connectors that allow you to quickly connect various equipment to it. A twisted pair of wires is called a twisted pair (balanced cable). Twisting the wires reduces the effect of external interference on the useful signals transmitted along the cable.

Coaxial cable has an asymmetrical design and consists of an internal copper core and braid, separated from the core by a layer of insulation. There are several types of coaxial cable, differing in characteristics and areas of application - for local networks, for wide area networks, for cable television and so on.

Communication systems via electrical communication cables are most widespread in distribution networks (for example, in cable television systems) and long-distance communication systems, however, the high cost of source materials (non-ferrous and precious metals), along with the relatively small bandwidth, make the competitiveness of such devices problematic in the future .

Common disadvantages of cable structures are: big time construction associated with excavation or underwater work, exposure to natural disasters, acts of vandalism and terrorism and the increasing cost of laying work. Work on the deployment of wired systems is labor-intensive, and in some places, especially historical parts of cities, in protected areas or with difficult terrain, it is practically impossible. And the associated inconveniences for residents, disruptions to transport, damaged roads and other related problems complicate the already difficult approval procedures with various authorities and reduce economic benefits.

Under construction cable lines communications occupy a special place electrical measurements which is carried out: in the construction lengths of the cable (on drums and after laying); inside balancing steps; when connecting steps or sections to each other (during balancing); on installed reinforcement (regeneration) sections. In addition, the characteristics of inductors, extension cords, boxes, gas-tight couplings, balun capacitors and other parts used in cable installation are measured.

1.4.3 Fiber optical lines communications

Currently, optical communication lines are increasingly used on backbone transport networks. The main element of such lines is an optical fiber cable, which consists of thin (3-60 microns) fibers through which light signals travel. This is the highest quality type of cable - it provides data transmission with very high speed(up to 10 Gbit/s and higher) and, moreover, provides data protection from external interference better than other types of transmission media.

Optical cable (OC) in its properties is immune to any external electromagnetic influences, and in terms of mechanical and other characteristics it is comparable to traditional electrical communication cables. Optical cables can be laid in collectors, telephone sewers, directly in the ground, along walls, under water and suspended on supports. Optical cable can be laid in close proximity to strong energy sources, parallel to high-voltage cables, oil and gas pipelines, as well as near electrified railways and other sources of electrical interference.

Fiber-optic communication lines have found their application in organizing inter-station communication on GTS (recently also on STS), where they successfully replace electric cables, in organizing communication on long-distance networks and on local networks for transmitting broadband information (cable television) and other types of communication.

Fiber-optic communication lines are used in all sections of the primary network for trunk, zonal and local communications. The requirements for such transmission systems differ in the number of channels, parameters and technical and economic indicators.

On trunk and zonal networks, digital fiber-optic communication lines are used, on local networks, digital fiber-optic communication lines are also used to organize connecting lines between automatic telephone exchanges, and on the subscriber section of the network, both analog (for example, to organize a television channel) and and digital communication lines.

1.4.4 Radio relay communication lines

One of the main types of modern means of communication are radio relay communication lines, which are used to transmit signals of multi-channel telephone messages, radio broadcasting and television, phototelegraph signals and other types of communication. All types of messages are transmitted via radio relay lines with high quality over long distances.

The large branching of networks of radio relay lines makes it possible to transmit significant technical needs when servicing power systems of railway and aviation transport, oil pipelines, etc. i.e. to create corporate independent networks.

The cost of construction of the designed RRL, as well as its subsequent operation, largely depends on the correct choice of route; a lot of work is being done on the economic justification of its optimal direction. First of all, materials are collected that characterize the economy and geographical conditions of the areas where the radio relay lines pass, communication routes and the main local construction resources, prospects for providing electricity to radio relay lines, and others. Then the route is first selected using large-scale topographic maps and the presence of its general direction. After this preliminary selection of the route, it is outlined in more detail using small-scale maps, distinguishing the locations of the proposed location of RRL sites.

The rapid growth of the share of CRRL in the creation of communication networks is determined by the high quality of signal transmission and high noise immunity of digital systems, and their significant economic efficiency. Transmitting signals in digital form has a number of advantages, namely: the ability to transmit all communication signals (both analog and discrete) in a single digital form over a universal linear path; reduction in operating costs (by approximately 25%); a significant reduction in the requirements for the linearity of the characteristics of signal transmission paths (group path, RF path); practically eliminating (due to the use of regenerators) the accumulation of voltages during retransmission; simplification and reduction in cost of channel-forming equipment; better provision communication secrecy; a sharp increase in communication quality in the presence of fading signals on RRL flights.

When transmitting analog signals digitally, three main signal processing processes can be distinguished: converting the analog signal into digital form; modulation digital signal intermediate frequency sinusoidal carrier; converting the manipulated LF signal into a microwave signal and amplifying this signal.

1.5 Selecting the optimal communication line option

When choosing the optimal communication line option, it is necessary to evaluate it based on the main cost indicators. The main cost indicator of economic efficiency is the specific costs of construction and operation (capital investments and annual operating costs), per 1 canal-km. Specific costs for the construction of domestic multi-channel wire and radio relay communication lines are significantly reduced as the number of channels increases. At RRL, the number of channels can be increased by additional installation of equipment for new trunks at the previous main structures (technical buildings, antenna towers, power supply devices). Table 1 shows comparative data on the annual economic effect from the introduction of wired and RRL [P.A.]. The use of RRL and fiber optic lines as a transport medium characterizes the transition of electrical communications to more high level its development regarding wired communications in technical, economic and social indicators. Modern, more advanced radio relay transmission systems (on integrated circuits) in terms of specific cost indicators are not inferior to analogues on symmetrical cable lines. Their specific costs are lower than those of cable systems, with slightly higher operating costs. At the same time, there are opportunities to further reduce the cost of radio relay communication equipment. The second important criterion for assessing the technical and economic efficiency of a communication line is natural indicators: electricity consumption, occupancy of production space, increased labor productivity, estimated by the number of channel-kilometers, as well as savings in non-ferrous metals of communication circuits. In telecommunication networks today, almost all of the described types of physical data transmission media are used, but fiber optics are the most promising. Today, both backbones of large territorial networks and high-speed communication lines of local networks are built on them. Comparative technical characteristics of promising optical cables with electrical cables, as well as other guiding systems, are given in Table 2 [P.A.].

The main advantages of optical cable include:

High noise immunity, insensitivity to external electromagnetic fields; no crosstalk between fibers;

Significantly higher broadband (up to 3000 MHz/km), the ability to transmit a large flow of information (several thousand channels);

The large length of the regeneration section, determined by the low attenuation of the optical cable, equal to 0.7 dB/km (and lower) at a wavelength of 1.3 μm, which makes it possible to increase the length of the regeneration section to 100 km;

Safety of using optical cable in areas with flammable and flammable environments due to the absence of short circuits and sparking;

In mass production - low cost due to significant savings in expensive and scarce non-ferrous metals;

The small overall dimensions and weight of the optical cable (10 times less than electrical cables) make it possible to more efficiently use expensive telephone ductwork and significantly reduce costs during transportation and cable installation;

Complete electrical isolation between the input and output of the communication system, which does not require common grounding of the transmitter and receiver;