Telecommunication Switching Systems and Networks by V S Bagad: An In-depth Analysis of the Latest Technologies and Trends
Telecommunication Switching Systems and Networks by V S Bagad Ebook: A Comprehensive Guide
Telecommunication is the transmission of information over a distance using electromagnetic signals. Telecommunication switching systems are devices that enable the connection and disconnection of different communication channels. Telecommunication networks are collections of switching systems interconnected by transmission links.
Telecommunication Switching Systems And Networks By V S Bagad Ebook
Telecommunication switching systems and networks are essential for modern communication systems, such as telephone, internet, mobile, satellite, etc. They enable efficient, reliable, secure, and cost-effective communication among users across the world.
Telecommunication Switching Systems and Networks by V S Bagad is a well-known textbook that covers both switching systems and telecommunications networks in a single volume. It is designed for the final-year undergraduate or the first-year postgraduate students in electronics and communication engineering and allied subjects. It provides an in-depth coverage of various topics, such as fibre optic communication systems, traffic engineering, data networks, ISDN, mobile communication, satellite communication, etc. It also includes numerous worked-out examples and exercises to help the readers understand all aspects of telecommunication engineering.
Overview of Telecommunication Switching Systems
The evolution of telecommunication switching systems can be traced back to the invention of the telephone by Alexander Graham Bell in 1876. The first telephone exchange was established in New Haven, Connecticut in 1878 using manual switchboards operated by human operators. The operators connected the calls by plugging wires into jacks on a panel.
Manual switching was soon replaced by automatic switching using electromechanical devices. The first automatic switching system was developed by Almon Strowger in 1889 using rotary switches. Later, crossbar switches were introduced in 1938 using horizontal and vertical bars to make contacts. These switches were faster, more reliable, and more compact than rotary switches.
Electromechanical switching was gradually replaced by electronic switching using transistors and integrated circuits. The first electronic switching system was developed by Bell Labs in 1965 using space division switching. Later, time division switching was introduced in 1976 using pulse code modulation and time slot interchange. These switches were more flexible, scalable, and efficient than electromechanical switches.
A switching system consists of three basic components: input/output devices, switch fabric, and control unit. Input/output devices are the interfaces between the switching system and the external communication channels. They perform functions such as signal conversion, multiplexing, modulation, etc. Switch fabric is the core of the switching system that establishes the connections between the input and output devices. It can be implemented using space division or time division techniques. Control unit is the brain of the switching system that performs functions such as call processing, routing, signaling, billing, etc.
A network structure is the arrangement of switching systems and transmission links in a telecommunication network. It determines the connectivity, reliability, scalability, and performance of the network. There are different types of network structures, such as star, tree, mesh, ring, etc. Routing is the process of selecting the best path for a call from the source to the destination in a network. There are different types of routing algorithms, such as fixed routing, alternate routing, adaptive routing, etc.
Types of Switching Systems
Strowger Switching Systems
Strowger switching systems are the first generation of automatic switching systems that use rotary switches to connect calls. A rotary switch consists of a set of contacts arranged in a circular pattern and a movable arm that rotates to select a contact. A strowger switch has two stages: selector stage and connector stage. The selector stage selects a free trunk line from a group of trunk lines. The connector stage connects the selected trunk line to the desired subscriber line.
A strowger switch can be operated by dial pulses or multifrequency tones generated by the calling subscriber. Dial pulses are interruptions in the loop current that correspond to the dialed digits. Multifrequency tones are combinations of two sinusoidal frequencies that correspond to the dialed digits. The strowger switch uses relays and stepping motors to convert the dial pulses or multifrequency tones into rotary movements of the switch arm.
Strowger switching systems have some advantages, such as simplicity, reliability, and low maintenance cost. However, they also have some disadvantages, such as low speed, high noise, limited capacity, and lack of features.
Crossbar Switching Systems
Crossbar switching systems are the second generation of automatic switching systems that use crossbar switches to connect calls. A crossbar switch consists of a matrix of horizontal and vertical bars that can make contacts at their intersections. A crossbar switch has three stages: marker stage, register stage, and link stage. The marker stage identifies the availability and location of the required resources for a call. The register stage stores the dialed digits and sends them to the marker stage. The link stage establishes the connection between the calling and called subscribers using crossbar switches.
A crossbar switch can be operated by common control or direct control methods. Common control method uses a central processor to control all the crossbar switches in a system. Direct control method uses local processors to control each crossbar switch independently.
Crossbar switching systems have some advantages over strowger switching systems, such as higher speed, lower noise, higher capacity, and more features. However, they also have some disadvantages, such as complex wiring, high power consumption, and mechanical wear and tear.
Electronic Space Division Switching Systems
Electronic space division switching systems are the third generation of automatic switching systems that use electronic switches to connect calls. An electronic switch consists of a set of semiconductor devices that can make or break an electrical circuit electronically. An electronic switch has two stages: control stage and switching stage. The control stage performs functions such as call processing, routing, signaling, billing, etc. The switching stage establishes the connection between the calling and called subscribers using electronic switches.
An electronic switch can be implemented using different technologies, such as reed relay matrix (RRM), transistor-transistor logic (TTL), emitter coupled logic (ECL), integrated injection logic (IIL), metal oxide semiconductor (MOS), complementary metal oxide semiconductor (CMOS), etc.
Electronic space division switching systems have some advantages over crossbar switching systems, such as higher reliability, lower power consumption, smaller size, and more flexibility. However, they also have some disadvantages, such as higher cost, heat dissipation, and interference.
Time Division Switching Systems
Optical Fiber Systems
Optical fiber systems are the latest generation of communication systems that use optical fibers to transmit signals. An optical fiber is a thin and flexible strand of glass or plastic that can carry light waves. An optical fiber system consists of three components: transmitter, receiver, and optical fiber link. The transmitter converts electrical signals into light signals and launches them into the optical fiber. The receiver converts light signals back into electrical signals and detects them. The optical fiber link is the medium that carries the light signals from the transmitter to the receiver.
Optical fiber systems have many advantages over conventional communication systems, such as higher bandwidth, lower attenuation, lower interference, higher security, and lower cost. However, they also have some challenges, such as signal distortion, dispersion, nonlinear effects, connector losses, etc.
Optical fiber systems use different technologies to improve their performance and capacity, such as optical sources and detectors, optical amplifiers, optical multiplexers and demultiplexers, optical filters, etc. Some of the most important technologies are SONET, WDM, and DWDM.
SONET (Synchronous Optical Network) is a standard for optical transmission that defines a hierarchy of signal rates and formats. It provides synchronization, multiplexing, switching, and management functions for optical signals. It also supports various services and protocols, such as voice, data, video, ATM, IP, etc.
WDM (Wavelength Division Multiplexing) is a technique for increasing the capacity of an optical fiber by transmitting multiple signals at different wavelengths (colors) simultaneously. It uses optical multiplexers and demultiplexers to combine and separate the signals at different wavelengths.
DWDM (Dense Wavelength Division Multiplexing) is a variant of WDM that uses more closely spaced wavelengths to achieve higher capacity. It can transmit up to 160 signals at different wavelengths over a single optical fiber.
Traffic Engineering
Traffic engineering is the study of the characteristics and behavior of traffic in telecommunication networks. It aims to optimize the performance, reliability, and efficiency of the networks by applying mathematical models and techniques.
Traffic engineering involves various concepts and parameters, such as traffic intensity, traffic load, traffic volume, traffic mix, arrival rate, service rate, holding time, etc. These parameters describe the amount and type of traffic in a network and its impact on the network resources.
Traffic engineering also involves various measures and criteria, such as grade of service (GOS), blocking probability (BP), delay probability (DP), queue length (QL), etc. These measures and criteria evaluate the quality and availability of service in a network and its effect on the user satisfaction.
Traffic engineering uses various formulas and methods to analyze and design telecommunication networks, such as Erlang B formula, Erlang C formula, Poisson distribution, binomial distribution, etc. These formulas and methods help to calculate the required network resources and parameters for a given traffic demand and GOS.
Traffic engineering also uses various tools and techniques to measure and monitor traffic in telecommunication networks, such as traffic counters, traffic analyzers, traffic generators, traffic simulators, etc. These tools and techniques help to collect and process traffic data and statistics for network management and optimization.
Telephone Networks
Telephone networks are the oldest and most widely used telecommunication networks that provide voice communication among users. They consist of switching systems and transmission links that connect subscribers' terminals (phones) to each other.
Telephone networks have a hierarchical structure that consists of several levels of switching centers (exchanges), such as local exchanges (LEs), toll exchanges (TEs), transit exchanges (TXs), international exchanges (IEs), etc. Each level of switching center serves a different geographical area and function in the network.
Telephone networks use different signaling techniques and protocols to exchange information between switching centers and subscribers' terminals for call establishment, maintenance, termination, etc. Some of the most common signaling techniques are loop disconnect signaling (LDS), multifrequency signaling (MFS), common channel signaling (CCS), etc. Some of the most common signaling protocols are signaling system 7 (SS7), integrated services digital network user part (ISDN-UP), etc.
Telephone networks use different numbering plans and routing schemes to assign unique numbers to subscribers' terminals and to select the best paths for calls in the network. Some of the most common numbering plans are E.164, E.212, E.214, etc. Some of the most common routing schemes are direct routing, indirect routing, hierarchical routing, alternate routing, etc.
Telephone networks use different charging and billing methods to collect fees from subscribers for using the network services. Some of the most common charging and billing methods are flat rate, message rate, measured rate, distance rate, time rate, etc.
Data Networks
Data networks are telecommunication networks that provide data communication among users. They consist of data terminals (computers), data switches (routers), and data links (wires or wireless) that transmit and receive data in the form of packets or frames.
Data networks have a layered structure that consists of several layers of functions and protocols, such as physical layer, data link layer, network layer, transport layer, etc. Each layer performs a specific function and communicates with the adjacent layers using a well-defined interface.
Data networks use different data communication concepts and standards to ensure reliable and efficient transmission and reception of data in the network. Some of the most important data communication concepts and standards are modulation, multiplexing, error detection and correction, flow control, etc.
Data networks use different data link layer protocols and error control techniques to ensure reliable and efficient delivery of data frames between adjacent nodes in the network. Some of the most common data link layer protocols and error control techniques are high-level data link control (HDLC), point-to-point protocol (PPP), cyclic redundancy check (CRC), automatic repeat request (ARQ), etc.
Data networks use different network layer protocols and routing algorithms to ensure reliable and efficient delivery of data packets across the network. Some of the most common network layer protocols and routing algorithms are internet protocol (IP), internet control message protocol (ICMP), address resolution protocol (ARP), open shortest path first (OSPF), border gateway protocol (BGP), etc.
Data networks use different transport layer protocols and flow control techniques to ensure reliable and efficient delivery of data segments between end nodes in the network. Some of the most common transport layer protocols and flow control techniques are transmission control protocol (TCP), user datagram protocol (UDP), sliding window protocol, congestion control protocol, etc.
Integrated Services Digital Network
Integrated services digital network (ISDN) is a telecommunication network that provides integrated services for voice, data, video, and other multimedia applications using digital transmission and switching technologies. It is an evolution of the traditional telephone network that uses analog transmission and switching technologies.
ISDN has a layered architecture that consists of three layers: physical layer, data link layer, and network layer. The physical layer defines the physical interface and transmission medium for ISDN. The data link layer defines the frame format and error control for ISDN. The network layer defines the signaling and addressing for ISDN.
ISDN has two types of interfaces: basic rate interface (BRI) and primary rate interface (PRI). BRI provides two 64 kbps bearer channels (B channels) for user data and one 16 kbps delta channel (D channel) for signaling. PRI provides 23 B channels and one D channel in North America or 30 B channels and one D channel in Europe.
ISDN provides various types of channels and services for different applications and users. Some of the most common types of channels are circuit-switched channels, packet-switched channels, virtual channels, etc. Some of the most common types of services are telephony service, teletex service, facsimile service, videotex service, etc.
ISDN uses various protocols and standards to ensure interoperability and compatibility among different ISDN equipment and networks. Some of the most important protocols and standards are Q.931, Q.921, I.430, I.431, etc.
Broadband ISDN (B-ISDN) is an extension of ISDN that provides higher bandwidth and more services for multimedia applications using optical fiber transmission and switching technologies. It uses asynchronous transfer mode (ATM) as the core technology for multiplexing, switching, and routing various types of traffic in the network.
Mobile Communication
Mobile communication is a telecommunication system that provides wireless communication among users using mobile devices (phones) and base stations (towers). It is an evolution of the traditional fixed-line communication system that uses wired communication among users using fixed devices (phones) and switching centers (exchanges).
Mobile communication uses the cellular system concept and frequency reuse technique to increase the capacity and coverage of the network. The cellular system concept divides the service area into small regions called cells, each served by a base station. The frequency reuse technique assigns the same frequency band to different cells that are sufficiently far apart to avoid interference.
Mobile communication uses different mobile radio propagation and fading models to describe and predict the behavior of the wireless channel. Some of the most common mobile radio propagation and fading models are free space model, two-ray model, log-distance model, log-normal shadowing model, Rayleigh fading model, Rician fading model, etc.
Mobile communication uses different multiple access techniques and standards to enable multiple users to share the same frequency band in the network. Some of the most common multiple access techniques are frequency division multiple access (FDMA), time division multiple access (TDMA), code division multiple access (CDMA), orthogonal frequency division multiple access (OFDMA), etc. Some of the most common mobile communication standards are global system for mobile communications (GSM), code division multiple access 2000 (CDMA2000), universal mobile telecommunications system (UMTS), long term evolution (LTE), etc.
Satellite Communication
Satellite communication is a telecommunication system that uses artificial satellites to relay signals between distant locations on Earth or in space. It is an alternative or complement to terrestrial communication systems that use cables or wireless links.
Satellite communication has some advantages over terrestrial communication systems, such as global coverage, high bandwidth, low delay, low maintenance cost, and easy deployment. However, it also has some disadvantages, such as high initial cost, high propagation loss, atmospheric attenuation, orbital congestion, security risk, etc.
Satellite communication uses different satellite orbits and orbital theory to determine the position and motion of satellites in space. Some of the most common satellite orbits are geostationary orbit (GEO), medium earth orbit (MEO), low earth orbit (LEO), etc. Some of the most important orbital theory concepts are Kepler's laws, orbital elements, orbital perturbations, etc.
Satellite communication uses satellite link budget analysis and design to calculate and optimize the performance and parameters of a satellite link. A satellite link budget analysis involves various factors and p