China Telecom Overview

The train of thought is: first talk about the device, then talk about network management, and finally talk about the relationship between systems.

I. Overview of China Telecom System
II. Introduction to various major telecommunication systems
3. China Telecom System Network Management and centralized monitoring system
Iv. Content of the system in charge of the operation department of the telecommunications system
V. Relationship between telecommunication systems
6. Telecommunication System Maintenance and Management System Structure

I. Overview of China Telecom System
The telecommunication system refers to the whole set of telecommunication equipment for coordination. The simplest telecommunications system is a leased line system established only between two users. The more complex system is a system consisting of multi-level communication networks providing channels for one call.
Divided by the daily operation and maintenance major, the telecommunications system is specialized by the Exchange major (including long-distance exchange, local exchange, intelligent network, No. 7 signaling, 112 System), transmission (including long-distance transmission equipment, local transmission equipment, digital synchronization network), line (including long-distance transmission lines, microwave and satellite communications, local transmission lines) access networks (including Wired Access Networks and wireless access networks), emergency communications, and resource management (including circuit scheduling and resource management) professional power supply, network management (including DCN and network management system maintenance, long-distance network analysis, and domestic network analysis. The Business Department maintains the IC/idcard system, 160/168 system, billing and accounting system, and business system, and the data network is maintained by the Data Bureau.
Classified into Level 1 trunk lines, level 2 trunk lines, and Region network. A level-1 trunk line refers to a network for communication between provinces. For example, the provincial capital city's long-distance bureau completes telephone exchanges with other provinces, and the Beijing-taixi optical cable passes through multiple provinces and cities from Beijing to Shaanxi, and the National Intelligent Network. Fixed assets of level-1 trunk lines belong to the group company, and are centrally managed and scheduled by the group company. A second-level trunk line refers to a network for communication between different cities in the province. For example, a city's long-distance bureau completes circuit exchange with other cities, and the provincial Intelligent Network is a second-level trunk line equipment. The fixed assets of level-2 trunk lines belong to provincial companies and are centrally managed and scheduled by provincial companies. A local network is a telephone service consisting of several local communication bureaus, communications bureaus, inter-office relay, long-city relay, user lines, and telephone terminals within the same long-distance area code. The fixed assets of the public network belong to local and municipal companies and are centrally managed and scheduled by local and municipal bureaus.
It is divided into transmission network, service network, support network, and user terminal device by type. A transmission network is a channel composed of line facilities and transmission facilities to provide the required transmission carrying capacity for information transmission services. Long-distance transmission network, local transmission network, and access network all belong to the transmission network. A service network is a network that provides users with telecom services such as telephones, telegrams, images, and data. The telephone exchange network, mobile exchange network, intelligent network, and data communication network all belong to the business network. A support network is a network that enables the telecom business network to run normally and plays a supporting role. Clock Synchronization Network, No. 7 signaling network, and network management network are all supported networks. User Terminal devices are user-side devices, such as telephones, fax machines, ISDN digital telephones, and PCs.
Network management refers to the telecom management network, also known as the network management and centralized monitoring system. Network management is mainly used for statistics, analysis, adjustment and optimization of telecommunication networks to ensure the high-quality and efficient operation of telecommunication equipment. The objects of management are networks; centralized Monitoring is mainly used to centrally monitor and control telecommunication network devices. Monitoring is short for monitoring to ensure the safe and reliable operation of telecommunication devices. A device is also called a network element.
II. Introduction to various major telecommunication systems
1. Transmission and line Majors
1.1 Overview
Transmission can be divided into Level 1 trunk line long-distance transmission, level 2 trunk line long-distance transmission, local transmission, access network, microwave and satellite communication. Before the restructuring of the telecom industry, China built an eight vertical and eight horizontal level dry-level long-distance transmission network, basically covering the whole country. Horizontal refers to east-west, such as the Beijing-Taiyuan-Shaanxi line, and vertical refers to the North-South direction, such as the Hubei line (Hohhot-Beihai ). The transmission network is dominated by SDH optical transmission, supplemented by Microwave and satellite communication. Currently, the access network is dominated by copper wire access and V5 access, supplemented by wireless access. Microwave Communication and satellite communication are currently in standby status because their capacity is far inferior to that of optical transmission. However, the equipment is very advanced. A 12-meter-diameter automatic tracking system is also a satellite antenna of the star chaser family, very magnificent.
The earliest long-distance transmission was via a bright line (copper wire). One pair of bright lines could only be used for one line of calls. Later, one pair of bright lines could contain up to 40 lines of calls, followed by a symmetric cable, later it was a symmetric cable, followed by a small coaxial cable (in that age, the carrier room was the most technical place in the post office and basically repaired the radio). The coaxial cable in China was a PCM Digital transmission method, (the long-distance communication was damaged because the daring hacker cut the wire and sold copper.) later, it was a cable. (We are telling you that there was no copper in the cable and it was useless to cut it. Here, we will do Wire Protection publicity), first PDH transmission, and then SDH transmission.
1.2. Optical Fiber and Optical Cable
Optical fiber is generally made of Z material, the cross section is very small double concentric cylinder, the outer layer is called the package layer refractive index N2, the inner layer is also called the refractive index of the core is N1, the refractive index of the package layer is slightly lower than that of the core. The light wave carrying information is guided forward by the interface of the core and package layer. It is called a guided wave. Guided Waves that generate total reflection on the core interface and pass through the Meridian (that is, the central axis of the optical fiber) can be used as optical carriers. [High school physics].
According to the refractive index, step Optical Fiber: N1 and N2 are fixed values. Gradient Optical Fiber: N1 gradually decreases with the increase of radius, and N2 remains unchanged.
Transmission Mode (because the transmission frequency of the cable is low, it is necessary to use two conductors to form a transverse electromagnetic mode (TEM mode) to transmit information. The optical fiber transmission frequency is high, only one optical fiber can form multiple modes to transmit information .) Split, Single-Mode Optical Fiber: Only one transmission mode in the optical fiber. The diameter of the Single-Mode Optical Fiber Core is small. It is a step-type optical fiber that only transmits the basic mode to avoid mode dispersion and is suitable for large-capacity and long-distance communication. Multimode Optical Fiber: multiple transmission modes in optical fiber. The diameter of the core is large. It is a gradient optical fiber. The bandwidth is narrow due to mode dispersion, but it is easier to manufacture, couple, and connect than single mode.
The main transmission parameters of the optical fiber include attenuation (Energy Loss) and dispersion (the error code is caused by inter-code interference ). The low-loss wavelength windows suitable for carriers in optical fibers are 850nm (mostly used for Multimode), 1310nm, and 1550nm.
Carrier: it can be understood to load the information to be transmitted to the wave. The carrier used for communication is electromagnetic waves, and the infrared interface used for computer carrier.
Optical fiber cables can be divided into submarine optical fiber cables, overhead optical fiber cables, pipe optical fiber cables, Directly Buried optical fiber cables, and military optical fiber cables. optical fiber cables consist of more than 2 cores (The unit of the number of optical fiber cables is the core ). To protect optical fibers, most trunk cables are filled with oil. Cable Laying Methods include direct burial (generally used for trunk lines), overhead, and pipelines (generally used in local cities. Directly Buried at the bottom of the ground 1 meter? There is a optical cable mark above the ground. The pole used by an overhead cable is generally called a pole link ). Long-distance transmission rod routes are generally optical fiber cables, while local transmission rod routes are generally optical fiber cables and power cables mixed into one pole for transmission.
1.3 SDH Transmission
SDH is called the Synchronous Digital System, which unifies the rate level, network node interface NNI, and frame structure of digital communication. SDH is to synchronous transmission module STM form to transmit, according to the level divided into STM-1: 155 Mbit/s (155), can accommodate 63 2 m; STM-2: 622 Mbit/s (622), can accommodate 4 155; STM-3: 2.5 Gbit/s (2.5g), can accommodate 4 622; 10 Gbit/s (10 Gb for short), can accommodate four 2.5 GB. SDH is based on 155. Ordinary Optical Communication transmits only one optical carrier on one optical fiber, while Dense Wavelength Division Multiplexing (DWDM) transmits different optical carriers at different wavelengths on one optical fiber. 10 Gb is implemented by DWDM.
Frame Structure:
Frame is based on bytes, n is the STM-N, the transmission direction is from the top left corner of the first byte, from left to right, from top to bottom in order to transmit. An STM of any level transmits 1 frame in 125 microseconds. STM-1 code rate = 270*9*8/(125*(10-6 power) = 155.520 Mbit/s. Soh: the overhead area used for network operation maintenance and management. Net Load area: transmits service information. Poh: the channel overhead area used for Channel maintenance and management. Management Unit pointer auptr area: consists of a group of codes. The value corresponding to this set of codes corresponds to the position of the information in the Information Net Load area (the location is numbered. In this way, the receiving end can accurately extract information from the Information Net Load area.
1.4 SDH Devices
Distribution Frame: A device used to configure and connect terminal user lines or trunk lines. The biggest advantage of distribution frame is flexible wiring. The Optical Distribution Frame ODF connects optical fiber cables through optical jumpers. The digital distribution frame DDF is used for the connection between 2 m cables. The main distribution frame MDF is used for the connection between the switch user cable and the egress cable through jumper.
The optical fiber used for connecting equipment racks is pigtails. Pigtails have a diameter of about 4mm, and both ends are equipped with standard connectors.
The interface connecting optical fiber or optical fiber is called optical port, and the interface connecting the optical fiber is called electrical port.
Optical Transceiver: generally composed of optical receivers, optical transmitters, and electrical terminals. There are also internal alarm modules (when the device is faulty) and official telephones (when the switch is not used for direct calls on the SDH network, and when the phone switch is down or fails, you can contact the switch through it. The optical terminal connects to the ODF through pigtails and connects to the DDF through a 2 m cable. It mainly implements functions such as photoelectric conversion. There are usually two types of Optical Sources in optical Transmitters: LD, high output optical power, narrow spectrum, and led, low output optical power, spectral width, low cost, and long service life. There are usually two types of photodetectors in the optical receiver: pin photodiodes and APD avalanche PHOTODIODES, which have an avalanche multiplier effect to improve the sensitivity of the high-gloss receiver. Detailed Principles of optical transceiver and optical cable line code types are not described in detail, it provides functions such as balance, code type conversion, scrambling code, encoding, driving light, photoelectric detection, pre-amplification, and main amplification, Judgment, decoding, and decoding, if you are interested, please refer to this book on Optical Fiber Communication Principles.
The 2 m cable conforms to the g703 standard and is the basic unit for inter-office transmission.
ADM (Add/drop multoplexing) Plug-in Multiplexing allows you to flexibly insert and split circuits, that is, the upper and lower circuits.
Dxc: Digital Cross connector, equivalent to automatic distribution frame, can be understood as replacing the jumper in the distribution frame with computer software, that is, replacing the hardware jumper with software jumper. It can easily implement circuit scheduling, protection switching, and other functions.
Optical Relay frame: it consists of optical transmitters, optical receivers, alarm circuits, and official telephones. Extend the optical transmission distance.
Monitoring Network Management Terminal: responsible for operation and maintenance of transmission devices and SDH networks.
1.5 SDH Network Structure
SDH network is generally composed of optical cables and several sites. Stations are divided into trunk stations and upstream and downstream stations. A relay only acts as a relay to extend the transmission distance. Based on the unified scheduling of the entire network, the upstream and downstream stations can allocate one or more 2 m of the trunk lines to the local area through ADM. SDH network can be divided into a ring network, a chain network, and a hybrid network (a combination of a ring and a chain ). A ring net is also called a self-healing Ring. During normal operation, information is transmitted along both clockwise and counterclockwise directions on the ring at the same time. In the receiving station, select one of the two directions as the main signal, and the other as the backup signal. When the optical cable is disconnected, the main signal and the standby signal are automatically communicated at the optical cable disconnection. For example, station 1, station 2, Station 3, and station 4 form a ring. The original information transmission method between station 1 and station 2 is that the transmission method of station 1 is 1-2, station 1 receives 2-1 optical fiber cables. If the optical fiber cables between station 1 and station 2 are cut off, the fiber cables of station 1 are changed to 1-4-3-2, station 1 Changes to 2-3-4-1.
Primary trunk lines, secondary trunk lines, and primary network are basically SDH transmission methods.
SDH Communication:
-------- | --------- | --------------- | ----------- |
-Optical Cable-Optical Distribution Frame-pigtail-optical terminal-2 m cable-digital distribution frame-2 m cable-switch, etc.
Upstream and downstream ends:
---------------------------------- | ~~~~ | (Digital distribution frame)
---------------------------------- |
-------- | --------- | ---------- | ------- |
-Optical Cable-Optical Distribution Frame-pigtails-optical terminal -- cable-ADM-cable-optical terminal
Only the end station that plays the role of relay:
-------- | ----------- | ------ +
--------- | ------------------- |
--------- + ------------ | ------ +
-Optical Cable-Optical Distribution Frame-pigtails-(optical terminal: the incoming and outgoing Optical terminals are in the same optical relay rack)
(Usually ADM is a block board, which is mounted in a rack with optical terminal, electrical terminal, and dxc)
1.6 Access Network
An access network consists of a series of transmission entities, including SNI (such as between a program-controlled switch and an access network device) and uni (between an access network device and a user terminal, provide the necessary transfer carrying capacity, which is transparent to user signaling and is not processed. It mainly implements cross-connection, multiplexing, and transmission functions, without switching functions. There are two types of access networks: Wired Access and wireless access. Wired Access is divided into remote module board, optical access network, copper access and other types.
1.6.1 copper wire access
Copper access is the most traditional and common access method. The diameter of the copper wire transmitted by the local telephone is generally 0.4mm. To ensure audio transmission, generally, the user line cannot exceed 5 kilometers. Therefore, the next Programmable switch in the traditional copper access mode can cover a region with a radius of 5 kilometers. Generally, the wiring method is used for hand-over. A user cable is generally provided by a program-controlled switch manufacturer. A user cable usually has 8 or 16 pairs of user cables. MDF: the main distribution frame. It is connected to both the horizontal and horizontal columns, the switch user cable, the trunk cable, and the straight column and the horizontal column with a dual-strand jumper (Common 0.4 plastic wire. In addition to flexible connections, MDF is also equipped with a security guard to prevent external power from entering devices (such as lightning and high voltage) through telephone lines ). The measuring platform refers to the electrical measurement (resistance, voltage, capacitor, etc.) of the user line to determine the cause of the obstacle (mixed line, broken line, ground gas, etc ). The trunk cable can contain up to 2400 pairs of copper wires. The trunk cable is divided into two types: oil filling and inflation. Fill the cable jacket with oil or gas to prevent moisture from being immersed in the core line. The inflatable model also requires a complete set of inflation system maintenance equipment. The transfer box is actually a micro distribution frame, which is responsible for connecting any one pair of trunk cable and any one pair of wiring cable. Wiring cables are about 100 pairs. The incoming line is usually a leather line.
| -------------- | ---------------- | ------------ | -------------- |
Switch -- User cable -- main distribution frame -- trunk cable -- junction box-wiring cable-distribution box -- Introduction line -- user terminal
1.6.2 remote module board access
Remote module Board refers to placing the user module of the programmable switch on the remote end through optical cables. Data production, billing, and user information of the remote module board are on the parent board. This method expands the coverage of the programmable switch. In various plans, remote module bureaus are not recommended, and it is considered that they cannot achieve multiple business access. However, at present, broadband services are far from mature, and most applications are dominated by telephone applications (the majority of optical access networks are also dominated by telephone access). In addition, the remote module board is closely connected with the parent board for convenient maintenance, therefore, it is still in use.
| ---------- | -------- | --------- | ------------ | ------ | ---------
Vswitch-2 m cable-DDF-2M cable-optical transceiver-2 m cable-remote module --- main distribution frame -----
1.6.3. optical access network access
The local device optical line terminal (OLT) is connected to the Programmable switch through the V5 interface. The remote optical network unit is connected to the user terminal through the user line. An OLT can be connected to multiple ONU. V5 interfaces include v5.1 and v5.2. The V5 interface implements standard connection between the OLT and the Programmable switch in units of 2 MB. Vswitches and optical access networks of different manufacturers can be interconnected through the V5 interface. In fact, the optical access network can be understood as changing the electrical transmission from a Programmable switch to optical transmission to expand the coverage of the programmable switch. The V5 interface is of little practical use to everyone. I will not detail it here.
| ---- | -- | --- | ----------- | ----
Switch -- DDF--OLT--DDF --- optical terminal-optical fiber-optical terminal --- ONU----MDF ----
1.6.4. Wireless Access
Wireless Access is the first solution for remote and mountainous areas (because there are few users and the line investment is too large). In order to achieve rural communication, basically, there is a base station in the terminal board that can connect to multiple terminal devices, and there is a terminal device in the village. Later, due to policy reasons, China Telecom did not apply for a mobile license, so Wireless Access (PHS) was developing rapidly. In fact, wireless local calls were a communication board rather than an access network. Therefore, the wireless phone exchange profession is briefly described.
The most important issue for wireless access is frequency application and allocation. It is easier for China Mobile and China Unicom to apply for GSM and CDMA from the CCN (Radio Management Board. The provincial companies apply for wireless access and wireless phone calls from provincial/municipal committees. If the provincial/municipal committee does not have a good working relationship with the provincial company, the frequency of requests will be very difficult, with a single fold. (So the most important thing in China is not technology, but relationship. .)
2. Exchange Majors
2.1. Programmable telephone switch
The switch type is primarily the EWSD of Shanghai Bell S1240 and Beijing bisc (which is a joint venture with Siemens) china site.
A Programmable telephone switch is the core of a fixed telephone network. Telephone Switches go through stages such as manual exchange, step-by-step exchange, horizontal exchange, and program-controlled exchange (storage program control. People of our age should be impressed 10 or even 20 years ago. I remember that the Chinese New Year always reported that the country's leaders had to send cordial condolences to the operator at the Beijing telephone and telegraph building, and the long-distance telephone staff in the post office lined up the TV screen. This shows how fast China Telecom is developing. Shi bancho is the boss of a funeral home in Kansas City. Whenever a family member of the deceased tells the operator that he wants to connect to a funeral home, the operator always connects the phone to another one (it is estimated that the operator was bought:). Old Shi was angry and vowed to implement automatic exchange without human transfer. In November 3, 1892, the step-by-step automatic telephone switch invented by old Shi was officially put into use, also known as the shiduan Qiao switch.
Vswitches can be divided into centralized control and decentralized control. Centralized control means that all the control functions of the entire switching system are undertaken by the processor. The advantage is that the system structure is simple, and the disadvantage is that the failure of the processor will affect switch operations. Distributed Control is the control function of the exchange system, which is assumed by each function module, that is, the distributed system. The advantage is that the system has good reliability and the disadvantage is that the architecture is complex. S1240 is a distributed control mode and EWSD is a centralized control mode.
The bandwidth of the Voice Band is 4000Hz (300-3400Hz) and the sampling frequency is 8000Hz. Therefore, the voice needs to be sampled at intervals of 125 microseconds and then changed to 8-bit binary code. This is the time slot. 32 channels are used for one 2 m of PCM, that is, 32 time slots are required within 125 microseconds, with each time slot accounting for 125/32 = 3.9 microseconds. The 32 time slots within 2 m are collectively referred to as a "frame ". In 32 time slots, the first time slot ts is used for synchronization. The fixed value is 10011011.
For a program-controlled telephone switch, all the lines connected to other program-controlled telephone switches are called inter-office relay. Inter-Office relay is formed by the relay group, and the relay group contains one to multiple relay lines. A trunk line is a logical concept. It is called a trunk line instead of a real-line connection. A line connected to a user's terminal device (such as a telephone number) is called a user line.
2.1.1. Exchange Network
The switching network consists of T-nodes and S-nodes. T-junction is a time-based access control consisting of voice memory and control memory. Working principle: To write the ts5 (with a time slot of 5) that passes through T-switched to the ts20 of the outlet to Unit 5 of the control memory, then, according to the number of units in the control memory, go to the corresponding time slot location of the voice memory to read the voice information and write it to the outlet. This is called the control memory to control writing, sequential reading, and sequential writing and controlling reading in the voice memory. There is another method opposite to this. T-junction is used to complete time slot switching on the same bus. The S-interface is a spatial interface consisting of an electronic crossover matrix and a control memory. The electronic crossover matrix has N inputs and N outputs to form an nxn matrix. Each bus (HW) contains n time slots, which are controlled by a group of n control storages. For example, if the value in group 3 of Group 2 is 2, The ts3 of group hw1 is switched to ts3 of group hw2 and the value in group 7 of Group 2 is 4, then, TS7 of hw2 is switched to TS7 of hw4. This is called output control, which is opposite to input control. The S-connector completes the exchange of the same time slot on different busbars.
Multiple T and S constitute an exchange network, which is generally composed of TST and TTT. For TST, level 1 t is responsible for the time slot exchange of the input bus, level 2 S is responsible for the space exchange between the buses, and level 3 T is responsible for the time slot exchange of the output bus. A two-way access is required for the exchange network. There must be a certain relationship between the two routes, such as a half frame difference, to reduce the processor load. Switching networks generally adopt dual-machine Hot Backup Redundancy. Another type of switch network is the switch network of the S1240 switch. The S1240 network consists of the plane selection level and the group selection level. The hardware consists of a swch board. Swch is a matrix switch (512 × 512) with the time division and air division switching function ). The current J-host generally has four planes. The switching network varies according to the number of modules. The S1240 is a fully distributed control, and its core is a digital exchange network.
2.1.2. User and relay modules
The user module can be categorized into seven functions: borscht. B: feed, the telephone is powered by a switch, the feed voltage is-48 V, the current is 18-50mA; O: overvoltage protection, except that there is a security guard in the total distribution frame, the user module must also have high-pressure protection. R: control the ringing of the ring to the called user, and control the stopping of the ring after the response is taken off. S: Monitor and monitor the various statuses of the user line, such as hanging status, picking status, dial-up pulse sending and receiving; C: compile code and filter to complete analog/analog conversion; H: hybrid circuit, because the analog signal is transmitted by second-line transmission, the digital signal is transmitted in four lines. Hybrid circuit for 2/4 line conversion; T: Test, complete the test of the user's internal and external line. User modules are generally divided into local and remote user modules. The remote user module has more external alarm functions than the local user module. The user module is generally composed of a common user board, a polarity reversal signal (mainly used for public calls) User Board, an ISDN User Board, a bell flow board, a power supply board, and a control panel. The user cable is connected to the user module.
The relay module generally implements code type conversion, synchronization and clock extraction, transmission and receiving of line signals, and other functions. The 2 m cable is connected to the relay module, and the other end is connected to the DDF digital distribution frame. Many switches now support 155 optical ports directly connected to the relay module.
2.1.3. Other modules
The signaling Unit completes the signaling process. For details, refer to the No. 7 signaling network. The error rate and other indicators of the signaling link are better than that of the Mandarin channel (the channel refers to the channel for transmitting voice information ). The recording notification module completes the recording notification function, such as busy voice and 117 Time. For details, see time synchronization network. The clock module can generate its own clock or synchronize it with the external clock. For details, see clock synchronization network. The input/output interface module connects to the hard disk, operating terminal, and printer. For details, see the network management monitoring system and billing collection system.
| ---------- | ------ |
User Terminal ----- User Module --- |
| ---------- | ------ | (Switching Network)
Inter-office relay ----- relay module --- |
| ---------- | ------ |
Signaling Link ----- signaling module --- |
++
++ (Processor)
---- | Input/output interface -- | clock Module
2.1.4. Traffic theory and key parameters
Due to the generation and development of telephone communication, it is urgent to solve the problem of business traffic and device configuration. A. K. Ireland first proposed the mathematical theory and application formula, and is the father of the telecom business traffic theory. Communication systems are divided into loss-based systems, waiting-based systems, and hybrid systems (wait for a while before the communication can be completed, give up ). Telephone Exchange is a loss system, and group exchange is a hybrid system. The call theory applies to telephone exchange and group exchange. Comrades who are interested in traffic control should learn the theory of traffic affairs well.
The user's call model generally conforms to the Poisson distribution. Traffic refers to the degree to which communication devices are occupied. The traffic formula is a = C x T. A is the call volume, measured in ERL (Ireland), C is the call count, measured in units, and T is the average duration of each call, measured in hours. Generally, a call volume is also called an hourly call. The time range of statistics is one hour. That is, C indicates the number of calls within one hour, and t indicates the average duration of each call. Frequently used key traffic indicators include: traffic per line (traffic per trunk line), average duration, and number of trial calls (total number of calls) number of relay calls, response times, and overflow times), number of user busy times, number of calls that are not allowed for a long time (no response is received after the ringing), traffic occupation, valid traffic, traffic per line, average traffic usage, number of user errors (including number of non-dial-up disconnections, incomplete dialing, and number of blank dialing numbers) number of congestion (call congestion caused by insufficient switch devices, such as small TST switching network.
One of the most important indicators of network operation is the connection rate. The access rate is actually the response usage ratio (or the response trial call ratio). For the operation and maintenance departments, the access rate is equivalent to GDP. This indicator is very important for a country, the connection rate competition is required every year. The reason is that China's communication resources are not rich in the past, so we need to complete the call connection as much as possible. In recent years, the Group Company has gradually reduced the concept of the connection rate competition because there are abundant communication resources and the main contradiction is to solve the traffic problem.
Because the network traffic varies for different times in a day, the traffic is also different. Take the busiest time of a day as the busy time. China's traffic analysis takes two busy hours: busy hours (-) and busy hours ).
Bhca is the number of calls during busy hours. It is used to measure the call processing capability of a switch. N = (t-A)/B, n is the total number of calls processed per unit time, that is, bhca, T is the switch's busy time usage (that is, the overhead used for call processing when the processor is busy), A is the overhead unrelated to call processing, and B is the average overhead used to process a call. For example, t = 0.7, A = 0.29, B = 32 ms, then n = 46000 times/hour.
In general, the traffic volume of each user in China is 0.1erl, and the traffic volume of each trunk line is 0.7erl. The average duration of each call is 60 s and 90 s. When the call volume is calculated, the call succeeds (that is, the call is initiated from the master node to the called server after the call is completed) and the call is counted as a live source call. Bhca = (user traffic X number of users)/average call usage + (inbound traffic x inbound traffic)/average call usage) = 6 * Number of users + 28 * Number of incoming relay.
System availability A = MTBF/(MTBF + MTTR), MTBF indicates the average system failure interval, and MTTR indicates the average system maintenance time.
For a vswitch, the number of users is generally called the number of doors, and the number of trunk lines is the number of terminals. For example, if a local vswitch can access a maximum of 90 thousand phone users, the vswitch has 90 thousand doors, A long-distance switch can provide 6000 relay lines, which are called 6000 ports.
2.1.5. China's exchange network structure
China's long-distance exchange network is divided into two levels, DC1 and DC2, DC1 refers to the first-level trunk lines are provincial capital cities and municipalities directly under the Central Government of long-distance switches, basically forming a mesh network in the DC1 plane, that is to say, there is direct relay between provincial capitals and other provincial capitals. DC2 refers to the second-level trunk lines that are long-distance switches between cities in the province, and the DC2 plane basically forms a mesh network, that is, a city in the same province has direct connections to other cities in the province.
The communications network can be divided into local communication bureaus, which provide direct user access. Communications bureaus can communicate with local communications bureaus and other communications (such as special servers). Communications bureaus are connected to networks of other operators; the SSP Bureau receives the provincial intelligent network to provide intelligent services. The private network bureau, a program-controlled switch belongs to the user and is connected to the operator's network. It generally belongs to the mining bureau, power plants, steel plants, and other large state-owned enterprises. The special service platform, special Services are provided. For example, the 114 platform provides a check number, the 112 platform provides an obstacle notice, 119 is a fire, and 110 is a police officer. TS: Long-distance Bureau, ls: local communication bureau, Tm: Communications Bureau, GW: Gateway Bureau, SSP: intelligent network bureau.
Vswitches are classified into efficient direct routing and trunk routing. A base-stem route is the most basic route. For example, if DC2 is sent to DC1 in this province, the base-stem route cannot overflow. Efficient direct routing is an additional route for two Bureaus with large traffic volumes, such as DC1 or DC2 from DC2 to other provinces. For example, from Yangquan to Shijiazhuang, efficient direct routing can overflow to the backbone routing.
2.1.6. Bureau data
Switch operation data is divided into two categories: Bureau data and user data. Bureau data refers to the data that enables inter-Bureau communication, such as routing, billing, and signaling. With the reform of the telecom industry, the data of interconnection bureaus is increased. User data refers to user attribute data. For example, if a user is shut down, a new user, or a user activates the call display service, user data is operated. For example, a user from the 202 Bureau calls the 404 Bureau (the first three digits of the phone number are generally used as the name of the phone Exchange Bureau), and there are 10 2 m direct relay between 202 and 404, the 202 direct relay group to the Settlement Board is called b7tm. Create a relay group in the 202 Bureau. For example, the relay group name is b7404, and then create a relay group consisting of 10 2 MB in the relay. <C> Create a destination, such as ls404, and then create route information. For example, use b7404 as the first route to ls404, and use b7tm as the second route to ls404. , And then establish a relationship between the destination code and the destination code, 404-ls404, which means that the number of users in the 202 Bureau will reach ls404. Create billing data. The billing data of 404 is: one Billing pulse is calculated within 180 seconds, and one Billing pulse is calculated every 60 seconds out of 180 seconds. This is called the billing method of the jump table. The long distance generally uses the detailed statement method. This is just basic and requires many parameters. For example, you need to set the call release control mode, whether the call control is called to control the release or not to control each other. Generally, they do not control each other. 110 and 119 are called controls.
If the first phone number is '0', it is called the Chinese long-distance crown. If the first phone number is '00', it is called the International Long-distance crown, A phone number cannot exceed 13 characters (excluding long-distance titles). The phone number is represented by pqrabcd (for example, 4121578, for example, 4-P, 1-Q, 2-r, 1-A, 5-B, 7-c, and 8-d) pqr is called the Bureau number, and ABCD is called the user number.
For User Data Automatic Stop and reply, and automatic new business and unified production Bureau data, see network management monitoring system.
2.1.7 call handling process of a programmable Switch
The switch detects that user a changes to the status of the device. In user data, find the category of user a (either a pulse phone or dual-audio phone, which is a common user, a small switch, or a public phone ); the switch sends a dial-up tone and prepares the receiving number. The receiving number receiver receives the user's dial-up number. When receiving the first number, it stops sending the dial-up tone. Generally, it analyzes the first half of the number, in order to determine the call type, and determine the number of digits to receive; in the Bureau data, check whether the call can be continued; check whether the called user is idle, if not idle, send back the busy voice; receive the called user, send a bell stream to the called user, and send a Bell tone back to the called user. The called user answers the call from the host, stops the ring and the return tone, and starts billing. After the call is complete, the called or called user hangs up and the route is restored, stop billing and send a busy voice to the peer user.
2.2 and 7 signaling network
The establishment and connection of any two telephone users between telephone networks can only be achieved through the relevant device following certain instructions and operating procedures, the signals for completing and implementing these commands and operating procedures are called telephone network signal systems. In fact, signaling is equivalent to a communication protocol (such as TCP/IP) in a vswitch, but it is called differently. Signaling is the neural system of the telephone network.
According to the working area of the signaling, it can be divided into user line signaling and inter-Bureau signaling. User line signaling refers to the signaling between the user and the switch, for example, the user disconnects the DC status signal of the host, DC pulse (dial-up phone) or dual-Tone Multi-frequency (button phone, dual-Tone Multi-frequency refers to a combination of Eight frequencies, representing numbers and * and # Keys) dialing signals. It reflects the signals such as Bell streams and return-tone busy tones in the idle state. Inter-board signaling refers to the signal between the switch and the switch, which is used to control the connection and disconnection of calls. There are two types of functions: Line signaling and route signaling. According to the signaling transmission mode, it can be divided into two types: the same-channel signaling and public channel signaling.
Call path: the path for transmitting voice information; Signaling Link: the path for transmitting signals.
A pay-as-you-go signaling is a method to transmit various required functional signals in a call. One PCM 2 m is called a frame, and 16 consecutive sub-frames are combined to call a compound frame. The first time slot of each sub-frame is used for synchronization, and the second time slot is used to transmit line signals of two channels, for example, ts16 of 0th frames transmits line signaling of tss1 and ts17, ts16 of 1st frames transmits line signaling of tss2 and ts18, and so on ,.... 15th frame ts16 transmission ts15 and ts31 line signaling, so that a complex frame ts16 transmits the whole complex frame of the TS1-TS15, TS17-TS31 line signaling, each session should have a corresponding signaling channel, so it is called a dispatch signaling. The generator signaling is the control signal for automatic telephone connection, including the selection of signaling and network management signaling. Multi-frequency mutual control (MFC) is generally used, that is, two combinations of six frequencies are used to form a group of codes, 15 forward signals in total, and two combinations of the four frequencies are used to form a group of codes, there are 6 kinds of backward signaling. Forward refers to the transfer of the caller to the called call, and backward refers to the transfer of the called call to the called call. A pay-as-you-go signaling is generally called an R2 signaling or a China 1 signaling. At present, in addition to some special servers, paging stations, voice stations, and so on, the same-line signaling is rarely used on the Internet. I will not go into detail here.
Public channel signaling is also called No. 7 signaling. For details, see the PPT document written by one of my predecessors. Here, I am a lazy. For example, after receiving the user's number, the caller A sends the initial address message Iam to the called B, and the B sends the full message to the ACM. After the called response, the B Department sends a response to the board. ans are divided into the response billing ANC and the response is not billed by Ann. After the called host is mounted, the B Department sends it to the department and sends the split-line message CBK. After the called host is mounted, the Department sends the split-line message CLF to the B Department. After the B Department recovers, bureau B issues a protection signal RLG to Bureau A, and the department a recovers. As long as it is connected through the No. 7 signaling, it is actually the Exchange Board. For example, if the wireless phone number (PHS) is associated with the exchange network by means of signaling 7, the wireless phone number is not in the access network category. In fact, it should be an exchange board.
2.3. Intelligent Network
See the PPT document written by one of my predecessors. (I am too tired to write .)
2.4. Clock Synchronization Network
The No. 7 signaling network, SDH network, and program-controlled telephone exchange network can work well and must maintain clock synchronization. The synchronization network function is to accurately transmit the clock synchronization information from the benchmark clock to each node of the synchronization network, so as to adjust the clock in the Network to establish and maintain clock synchronization. China's clock synchronization network adopts the four-level master-slave synchronization mode, and international communication adopts the quasi-synchronization mode. Level 1: The reference clock is composed of three WeChat atomic clocks. Level 2: A high-stability crystal clock with a persistence function, using a double backup of the thermostatic Cell Crystal, or a Rb atomic clock. Level 3: high-Stability Crystal Clock is compensated for temperature with the persistence function. Its frequency offset rate and persistence capability are lower than the second-level clock. Level 4: General crystal clock, when the reference source is lost, it enters the free running status and does not transmit the scheduled reference. There should be no loops in the clock synchronization network; reduce the length of the scheduled transmission link as much as possible; master and slave benchmarks should be obtained from scattered routes; the controlled clock should be obtained from other devices at the same level or higher level; select a high-availability transmission system transfer benchmark. The first-level benchmark clock (PRC) is located in Beijing and Wuhan. The provincial cities and municipalities have established the second-level benchmark clock LPR. The LPR system is composed of two GPS (satellite GPS) receivers installed in the zhuzhong district, provides a time baseline signal with a latency of 10-11 power over 1. Bits: provides comprehensive and scheduled system equipment. bits are set at Level 2 and Level 3, and the clock to be synchronized in the production building is synchronized. Generally, the external synchronous signal of a digital communication device is 2.048 Mbit/s or 2.048 MHz. Basically, the synchronous Network timing signal is transmitted over SDH, SDH Network Element should have 2 Mb/s external synchronous port, electrical performance in line with g703, frame structure and SSM format in line with g704, the output of the synchronous signal should be directly restored from the STM-N; the synchronization network has a centralized monitoring and management device SRM in the provincial center.
3. Power Supply and Air Conditioning
I couldn't write it, so I had to move a friend's documents out as a rescue. The heat of the equipment is very large. Generally, the machine room is equipped with air conditioners, while the program-controlled switch room is usually equipped with specialized air conditioners, which are specialized air conditioners with high temperature, humidity, and reliability. A humidifier is required for air drying areas in other data centers, because static electricity is generated when the humidity is low.