1) CAP and DMT are technologies that divide telephone signals into separate channels to minimize interference and maximize bandwidth utilization. CAP uses voice, upstream, and downstream channels while DMT uses 256 discrete channels.
2) Wi-Fi and WiMAX are wireless technologies. Wi-Fi uses radio waves to connect devices in a local area network while WiMAX can provide connectivity over longer distances at speeds up to 75 Mbps.
3) GSM interfaces include the air interface between mobile stations and base transceiver stations, the A-bis interface between BTS and BSC, and the A-interface between BSC and MSC.
CDMA is a technique that allows multiple users to access the network using the same frequency band at the same time. It works by spreading each user's signal across the entire bandwidth using unique codes. This allows signals to overlap without interfering with each other. Key advantages of CDMA include larger network capacity, less transmit power per user, seamless handoffs between cells, no need for frequency planning, high tolerance of interference, and multiple diversity techniques. A typical CDMA network can support 400 subscribers per sector using 1.25MHz of spectrum, allowing a cell with 6 sectors to support up to 2,400 subscribers on a single frequency channel.
The document discusses signaling fundamentals in a base station subsystem (BSS). It describes the A, Abis, and Um interfaces between the BSS components. The A interface uses SS7 protocol layers including the physical layer, MTP, SCCP and BSSAP. The BSSAP layer supports BSSMAP messages for connectionless and connection-oriented signaling between the BSS and MSC.
Improvement of signal coverage using wcdma signal repeater for 3 g systemsIjrdt Journal
Wireless communication has become an indispensable technology for the society. In broadband wireless data transmission technique, 3G cellular systems are expected to provide high data rate and less probability of error. This repeater finds application in areas of poor signal coverage and connectivity. The repeater consists of a patch panel antenna for receiving WCDMA signals from the base station and amplifying the signals using a wideband RF amplifier. The signals are then retransmitted to the weak coverage area using a directional Yagi-Uda antenna. The antenna characteristics such as return loss and VSWR are measured using a Network analyzer. The component of the repeater are mounted in a stand and the performance of the entire unit was evaluated using a WCDMA generator, act as a base station, transmitting at 869 MHz and 5dBm output power. A spectrum analyzer with WCDMA analyzer is used as a receiver, the RF signal level and constellation plots with error vector magnitude are determined
GSM-Mobility Management-Call Control
GRPS-Network elements
Radio Resource Management
Mobility Management and Session Management
Small Screen Web Browsing
UTRAN-Core and Radio Network Mobility Management
UMTS Security
The document discusses radio technologies for mobile WiMAX networks, including OFDM, OFDMA, S-OFDMA, smart antenna systems, and frequency reuse strategies. It explains how these technologies improve spectral efficiency, coverage, throughput and quality of service. Specifically, it discusses how OFDM/OFDMA divide the frequency band into multiple subcarriers to increase robustness to interference, how smart antennas like beamforming increase signal strength and throughput, and how frequency reuse optimization is important to maximize spectrum usage while minimizing interference.
This document provides an overview of Wideband Code Division Multiple Access (WCDMA) technology. It discusses how WCDMA evolved from existing GSM and CDMA technologies to provide higher data rates and capacity. Key aspects of WCDMA include efficient power control, soft handover between cells, and the ability to allocate capacity between voice and data services. The document describes the basic architecture of a WCDMA network including the radio access network components like Node B base stations and radio network controllers.
IRJET- Performance Comparison Analysis between Multi-FFT OFDM for Power Line ...IRJET Journal
This document compares different multi-FFT OFDM techniques for power line carrier communications. It analyzes the performance of partial FFT (P-FFT), shaped FFT (S-FFT), fractional FFT (F-FFT), and Taylor FFT (T-FFT) demodulation methods to reduce inter-carrier interference in OFDM systems over power lines. These multiple-FFT techniques approximate the optimal receiver front-end for time-varying power line channels better than a single FFT. The document also discusses OFDM modulation, power line communications, and proposes using multiple FFT demodulation and combining to improve the speed and robustness of power line communication channels.
White paper on Why Power Line Communication is the best fit for AMI In indiaSameer Patil
This document compares different communication technologies for smart metering in India and argues that power line communication (PLC) is best suited. It discusses advantages of PLC over radio frequency (RF) and GPRS technologies. PLC has better coverage since it can reach all meters connected to power lines. It is not impacted by building materials or topography like RF and GPRS. PLC also allows real-time asset mapping and energy auditing since networks are isolated by distribution transformers. Additionally, PLC has lower costs since it utilizes existing power infrastructure and fewer repeaters are needed compared to RF. Ongoing maintenance is also lower for self-healing PLC networks versus RF networks. Therefore, the document concludes that PLC is
CDMA is a technique that allows multiple users to access the network using the same frequency band at the same time. It works by spreading each user's signal across the entire bandwidth using unique codes. This allows signals to overlap without interfering with each other. Key advantages of CDMA include larger network capacity, less transmit power per user, seamless handoffs between cells, no need for frequency planning, high tolerance of interference, and multiple diversity techniques. A typical CDMA network can support 400 subscribers per sector using 1.25MHz of spectrum, allowing a cell with 6 sectors to support up to 2,400 subscribers on a single frequency channel.
The document discusses signaling fundamentals in a base station subsystem (BSS). It describes the A, Abis, and Um interfaces between the BSS components. The A interface uses SS7 protocol layers including the physical layer, MTP, SCCP and BSSAP. The BSSAP layer supports BSSMAP messages for connectionless and connection-oriented signaling between the BSS and MSC.
Improvement of signal coverage using wcdma signal repeater for 3 g systemsIjrdt Journal
Wireless communication has become an indispensable technology for the society. In broadband wireless data transmission technique, 3G cellular systems are expected to provide high data rate and less probability of error. This repeater finds application in areas of poor signal coverage and connectivity. The repeater consists of a patch panel antenna for receiving WCDMA signals from the base station and amplifying the signals using a wideband RF amplifier. The signals are then retransmitted to the weak coverage area using a directional Yagi-Uda antenna. The antenna characteristics such as return loss and VSWR are measured using a Network analyzer. The component of the repeater are mounted in a stand and the performance of the entire unit was evaluated using a WCDMA generator, act as a base station, transmitting at 869 MHz and 5dBm output power. A spectrum analyzer with WCDMA analyzer is used as a receiver, the RF signal level and constellation plots with error vector magnitude are determined
GSM-Mobility Management-Call Control
GRPS-Network elements
Radio Resource Management
Mobility Management and Session Management
Small Screen Web Browsing
UTRAN-Core and Radio Network Mobility Management
UMTS Security
The document discusses radio technologies for mobile WiMAX networks, including OFDM, OFDMA, S-OFDMA, smart antenna systems, and frequency reuse strategies. It explains how these technologies improve spectral efficiency, coverage, throughput and quality of service. Specifically, it discusses how OFDM/OFDMA divide the frequency band into multiple subcarriers to increase robustness to interference, how smart antennas like beamforming increase signal strength and throughput, and how frequency reuse optimization is important to maximize spectrum usage while minimizing interference.
This document provides an overview of Wideband Code Division Multiple Access (WCDMA) technology. It discusses how WCDMA evolved from existing GSM and CDMA technologies to provide higher data rates and capacity. Key aspects of WCDMA include efficient power control, soft handover between cells, and the ability to allocate capacity between voice and data services. The document describes the basic architecture of a WCDMA network including the radio access network components like Node B base stations and radio network controllers.
IRJET- Performance Comparison Analysis between Multi-FFT OFDM for Power Line ...IRJET Journal
This document compares different multi-FFT OFDM techniques for power line carrier communications. It analyzes the performance of partial FFT (P-FFT), shaped FFT (S-FFT), fractional FFT (F-FFT), and Taylor FFT (T-FFT) demodulation methods to reduce inter-carrier interference in OFDM systems over power lines. These multiple-FFT techniques approximate the optimal receiver front-end for time-varying power line channels better than a single FFT. The document also discusses OFDM modulation, power line communications, and proposes using multiple FFT demodulation and combining to improve the speed and robustness of power line communication channels.
White paper on Why Power Line Communication is the best fit for AMI In indiaSameer Patil
This document compares different communication technologies for smart metering in India and argues that power line communication (PLC) is best suited. It discusses advantages of PLC over radio frequency (RF) and GPRS technologies. PLC has better coverage since it can reach all meters connected to power lines. It is not impacted by building materials or topography like RF and GPRS. PLC also allows real-time asset mapping and energy auditing since networks are isolated by distribution transformers. Additionally, PLC has lower costs since it utilizes existing power infrastructure and fewer repeaters are needed compared to RF. Ongoing maintenance is also lower for self-healing PLC networks versus RF networks. Therefore, the document concludes that PLC is
The document is a chapter from a textbook on digital communication techniques. It covers topics such as digital transmission of data, parallel and serial transmission, and data conversion. Some key points include:
- Digital communication has largely replaced analog communication since the 1970s due to benefits like noise immunity, error detection/correction, and compatibility with technologies like time-division multiplexing.
- Data can be transmitted either in parallel (all bits at once) or serially (one bit at a time). Serial transmission is more practical for long distances.
- Analog to digital conversion (ADC) involves sampling an analog signal and assigning it a digital value, while digital to analog conversion (DAC) reconstructs an analog signal from digital values.
The document discusses planning requirements for mobile telephone networks including providing capacity and frequency efficiency while maintaining low cost and high quality of service. It then summarizes key factors to consider in network planning such as frequency spectrum allocation, traffic capacity calculations, propagation effects, frequency reuse patterns, and overcoming adverse propagation conditions. Planning tools are discussed that can model signal strength across cells to aid in the planning process.
1) JVVNL is the largest electricity distribution company in Jaipur, Rajasthan, distributing power to 12 districts. It was formed in 2000 by unbundling the state electricity board.
2) Power line carrier communication (PLCC) uses existing power lines to transmit information for telecommunication and monitoring between substations. It involves modulating data onto a carrier frequency and transmitting it through couplers onto power lines.
3) PLCC equipment includes indoor equipment like modems and outdoor equipment like line traps, which block high frequencies but allow power frequencies to pass through power lines.
This document summarizes Sharanjit Kaur's industrial training presentation at MTNL. It introduces MTNL and provides an overview of topics covered during training, including switching, signaling, broadband, and transmission. It then describes projects undertaken and steps to improve quality of service in 3G networks, including checking equipment, monitoring KPIs, increasing bandwidth, and performing drive tests using the TEMS Investigation tool.
Comparison between gsm & cdma najmul hoque munshiNajmulHoqueMunshi
This document compares and contrasts GSM and CDMA cellular communication technologies. It begins with an introduction to cellular concepts and architectures. It then describes GSM, including that it uses TDMA and operates at 900/1800 MHz bands. The GSM architecture includes components like the BTS, BSC, HLR, VLR, and AuC. It then describes CDMA, including that it uses spread spectrum technology and references GPS for timing. The CDMA architecture spreads each user's signal over the entire bandwidth using unique codes. Finally, it lists the main differences between GSM and CDMA, such as their use of different multiple access technologies and CDMA providing better security through encryption.
This document discusses adaptive modulation and coding (AMC) techniques in wireless communications. It provides an introduction to AMC and describes how it allows matching modulation, coding, and other signal parameters to radio link conditions. The document then outlines the development roadmap for broadband wireless access (BWA) and WiMAX, including added support for mobility, advanced antennas, and modulation/coding schemes. It discusses the advantages of AMC in improving transmission rates and bit error rates by exploiting channel state information. Finally, it notes challenges around AMC being sensitive to measurement errors and delay in selecting the appropriate modulation.
A communications system allows for the transfer of information from an information source to an information sink. It consists of a transmitter that encodes a message from the information source into a transmitted signal, a channel to carry the signal, and a receiver to decode the signal back into a message for the information sink.
The transmitter may perform operations like modulation, amplification, and filtering on the message signal. The channel can be a wireline medium like coaxial cable or a wireless medium like free space. It is subject to degradation from noise, interference and distortion. The receiver performs complementary operations to the transmitter like demodulation, amplification and filtering to recover the original message from the received signal for the information sink.
The document discusses the evolution of wireless communication technologies through generations from 2G to 4G. It describes the key characteristics and speed capabilities of each generation. It also provides details on various wireless networking components and concepts such as channel access schemes, radio signals, BTS, BSC, MSC, HLR, AuC, EIR and SMSC.
Power line carrier communication (PLCC) is a method of transmitting information over existing power lines. It works by injecting a high frequency signal over electrical power lines. PLCC has been found to be an economical and reliable method of medium to long distance communication. It uses the power lines as a communication medium by varying a carrier signal to convey information. A few common modulation techniques used in PLCC networks include OFDM, GMSK, and DSSS. Security is an important issue for PLCC since it operates over a shared channel like Wi-Fi and requires encryption. PLCC provides communication infrastructure without additional wiring and utilizes the existing power grid.
Data Communications,Data Networks,computer communications,multiplexing,spread spectrum,protocol architecture,data link protocols,signal encoding techniques,transmission media,asynchronous transfer mode,routing,cellular networks
A trade-off design of microstrip broadband power amplifier for UHF applications IJECEIAES
In this paper, the design of a Broadband Power Amplifier for UHF applications is presented. The proposed BPA is based on ATF13876 Agilent active device. The biasing and matching networks both are implemented by using microstrip transmission lines. The input and output matching circuits are designed by combining two broadband matching techniques: a binomial multi-section quarter wave impedance transformer and an approximate transformation of previously designed lumped elements. The proposed BPA shows excellent performances in terms of impedance matching, power gain and unconditionally stability over the operating bandwidth ranging from 1.2 GHz to 3.3 GHz. At 2.2 GHz, the large signal simulation shows a saturated output power of 18.875 dBm with an output 1-dB compression point of 6.5 dBm of input level and a maximum PAE of 36.26%.
Power line communication uses existing power lines to transmit data signals. It provides a cost-effective solution compared to installing new communication wiring. The document discusses the basic concepts of power line communication, including that different frequencies are used depending on the wiring and applications can have data rates from kilobits per second to megabits per second over short distances. Advances in digital signal processing have allowed new designs to overcome noise issues on power lines using techniques like spread spectrum modulation and error correction coding. Standards still vary globally which limits technical information sharing for these proprietary systems.
This slide includes
Advanced multiplexing
Code Division Multiplexing
Dense Wavelength Division Multiplexing
OFDM
Connectionless
LAN
L3 SWTICH
SLIP
PPP
CORE AND DISTRIBUTION NETWORKS.
This document discusses mobile communications and cellular systems. It describes the basic components like subscribers, base stations, and different communication modes. It then explains the fundamentals of cellular systems including cell structure, base stations, mobile units, and wireless components. Finally, it outlines the process of making and receiving telephone calls through a cellular network including call handoff between base stations.
The document discusses power line carrier communication (PLCC). It provides an introduction to PLCC, describing it as an economical and reliable method for long-distance communication in a power system. It then lists the contents to be covered, including the basic principles of PLCC, types of coupling used, wave traps, battery chargers, and advantages and disadvantages. PLCC allows sending signals over power lines using coupling devices and wave traps to prevent interference with power equipment.
History, Basic concepts of wireless communication, challenges in wireless communication, cellular communication, performance criteria, wireless communication standars, how call is made?
1) 3G networks combine developments in cellular networks, fixed-line networks, and the internet to provide flexible access to any service regardless of location.
2) First generation networks provided analog voice calls with low quality and security. Second generation networks like GSM introduced digital cellular and allowed data services.
3) A GSM network includes mobile stations, a base station subsystem with base transceiver stations and base station controllers, a network switching subsystem with mobile switching centers, home and visitor location registers, and connections to public switched telephone networks.
This document discusses wireless communication and GSM networks. It provides an overview of multiple access techniques used in wireless networks like TDMA, FDMA, and CDMA. It then describes the development and standards of GSM networks and how they were created to provide a digital cellular standard across Europe to resolve issues with different analog 1G systems. Finally, it summarizes the call setup process in a GSM network for a mobile terminated call, including analyzing the number, interrogating the HLR and MSC/VLR, generating a temporary MSRN, and initiating paging to locate the called subscriber.
The document discusses broadband services provided by BSNL. It defines broadband as a high-speed, always-on internet connection with a minimum download speed of 256 kbps. Broadband offers advantages like fast access to the internet, video on demand, interactive gaming, audio/video conferencing, and distance learning. BSNL provides broadband through various wired and wireless technologies depending on factors like population density, existing infrastructure, government policies, and technology evolution. The network architecture has three parts - the last mile access network connecting subscribers, a metro area network comprising the core network, and service provisioning equipment at the provider's premises.
1) Data communication involves transmitting information from a source to a receiver using a medium. The basic components are a source that generates the data, a medium that carries the data, and a receiver that obtains the data.
2) There are three main types of transmission: simplex allows transmission in one direction only, half duplex allows transmission in two directions but not simultaneously, and full duplex allows simultaneous two-way transmission using two channels.
3) Data is transmitted as a series of 1s and 0s using a code, such as ASCII, that defines each symbol. Transmission can be parallel, with all bits sent at once on separate lines, or serial, with bits sent one after the other on
The document is a chapter from a textbook on digital communication techniques. It covers topics such as digital transmission of data, parallel and serial transmission, and data conversion. Some key points include:
- Digital communication has largely replaced analog communication since the 1970s due to benefits like noise immunity, error detection/correction, and compatibility with technologies like time-division multiplexing.
- Data can be transmitted either in parallel (all bits at once) or serially (one bit at a time). Serial transmission is more practical for long distances.
- Analog to digital conversion (ADC) involves sampling an analog signal and assigning it a digital value, while digital to analog conversion (DAC) reconstructs an analog signal from digital values.
The document discusses planning requirements for mobile telephone networks including providing capacity and frequency efficiency while maintaining low cost and high quality of service. It then summarizes key factors to consider in network planning such as frequency spectrum allocation, traffic capacity calculations, propagation effects, frequency reuse patterns, and overcoming adverse propagation conditions. Planning tools are discussed that can model signal strength across cells to aid in the planning process.
1) JVVNL is the largest electricity distribution company in Jaipur, Rajasthan, distributing power to 12 districts. It was formed in 2000 by unbundling the state electricity board.
2) Power line carrier communication (PLCC) uses existing power lines to transmit information for telecommunication and monitoring between substations. It involves modulating data onto a carrier frequency and transmitting it through couplers onto power lines.
3) PLCC equipment includes indoor equipment like modems and outdoor equipment like line traps, which block high frequencies but allow power frequencies to pass through power lines.
This document summarizes Sharanjit Kaur's industrial training presentation at MTNL. It introduces MTNL and provides an overview of topics covered during training, including switching, signaling, broadband, and transmission. It then describes projects undertaken and steps to improve quality of service in 3G networks, including checking equipment, monitoring KPIs, increasing bandwidth, and performing drive tests using the TEMS Investigation tool.
Comparison between gsm & cdma najmul hoque munshiNajmulHoqueMunshi
This document compares and contrasts GSM and CDMA cellular communication technologies. It begins with an introduction to cellular concepts and architectures. It then describes GSM, including that it uses TDMA and operates at 900/1800 MHz bands. The GSM architecture includes components like the BTS, BSC, HLR, VLR, and AuC. It then describes CDMA, including that it uses spread spectrum technology and references GPS for timing. The CDMA architecture spreads each user's signal over the entire bandwidth using unique codes. Finally, it lists the main differences between GSM and CDMA, such as their use of different multiple access technologies and CDMA providing better security through encryption.
This document discusses adaptive modulation and coding (AMC) techniques in wireless communications. It provides an introduction to AMC and describes how it allows matching modulation, coding, and other signal parameters to radio link conditions. The document then outlines the development roadmap for broadband wireless access (BWA) and WiMAX, including added support for mobility, advanced antennas, and modulation/coding schemes. It discusses the advantages of AMC in improving transmission rates and bit error rates by exploiting channel state information. Finally, it notes challenges around AMC being sensitive to measurement errors and delay in selecting the appropriate modulation.
A communications system allows for the transfer of information from an information source to an information sink. It consists of a transmitter that encodes a message from the information source into a transmitted signal, a channel to carry the signal, and a receiver to decode the signal back into a message for the information sink.
The transmitter may perform operations like modulation, amplification, and filtering on the message signal. The channel can be a wireline medium like coaxial cable or a wireless medium like free space. It is subject to degradation from noise, interference and distortion. The receiver performs complementary operations to the transmitter like demodulation, amplification and filtering to recover the original message from the received signal for the information sink.
The document discusses the evolution of wireless communication technologies through generations from 2G to 4G. It describes the key characteristics and speed capabilities of each generation. It also provides details on various wireless networking components and concepts such as channel access schemes, radio signals, BTS, BSC, MSC, HLR, AuC, EIR and SMSC.
Power line carrier communication (PLCC) is a method of transmitting information over existing power lines. It works by injecting a high frequency signal over electrical power lines. PLCC has been found to be an economical and reliable method of medium to long distance communication. It uses the power lines as a communication medium by varying a carrier signal to convey information. A few common modulation techniques used in PLCC networks include OFDM, GMSK, and DSSS. Security is an important issue for PLCC since it operates over a shared channel like Wi-Fi and requires encryption. PLCC provides communication infrastructure without additional wiring and utilizes the existing power grid.
Data Communications,Data Networks,computer communications,multiplexing,spread spectrum,protocol architecture,data link protocols,signal encoding techniques,transmission media,asynchronous transfer mode,routing,cellular networks
A trade-off design of microstrip broadband power amplifier for UHF applications IJECEIAES
In this paper, the design of a Broadband Power Amplifier for UHF applications is presented. The proposed BPA is based on ATF13876 Agilent active device. The biasing and matching networks both are implemented by using microstrip transmission lines. The input and output matching circuits are designed by combining two broadband matching techniques: a binomial multi-section quarter wave impedance transformer and an approximate transformation of previously designed lumped elements. The proposed BPA shows excellent performances in terms of impedance matching, power gain and unconditionally stability over the operating bandwidth ranging from 1.2 GHz to 3.3 GHz. At 2.2 GHz, the large signal simulation shows a saturated output power of 18.875 dBm with an output 1-dB compression point of 6.5 dBm of input level and a maximum PAE of 36.26%.
Power line communication uses existing power lines to transmit data signals. It provides a cost-effective solution compared to installing new communication wiring. The document discusses the basic concepts of power line communication, including that different frequencies are used depending on the wiring and applications can have data rates from kilobits per second to megabits per second over short distances. Advances in digital signal processing have allowed new designs to overcome noise issues on power lines using techniques like spread spectrum modulation and error correction coding. Standards still vary globally which limits technical information sharing for these proprietary systems.
This slide includes
Advanced multiplexing
Code Division Multiplexing
Dense Wavelength Division Multiplexing
OFDM
Connectionless
LAN
L3 SWTICH
SLIP
PPP
CORE AND DISTRIBUTION NETWORKS.
This document discusses mobile communications and cellular systems. It describes the basic components like subscribers, base stations, and different communication modes. It then explains the fundamentals of cellular systems including cell structure, base stations, mobile units, and wireless components. Finally, it outlines the process of making and receiving telephone calls through a cellular network including call handoff between base stations.
The document discusses power line carrier communication (PLCC). It provides an introduction to PLCC, describing it as an economical and reliable method for long-distance communication in a power system. It then lists the contents to be covered, including the basic principles of PLCC, types of coupling used, wave traps, battery chargers, and advantages and disadvantages. PLCC allows sending signals over power lines using coupling devices and wave traps to prevent interference with power equipment.
History, Basic concepts of wireless communication, challenges in wireless communication, cellular communication, performance criteria, wireless communication standars, how call is made?
1) 3G networks combine developments in cellular networks, fixed-line networks, and the internet to provide flexible access to any service regardless of location.
2) First generation networks provided analog voice calls with low quality and security. Second generation networks like GSM introduced digital cellular and allowed data services.
3) A GSM network includes mobile stations, a base station subsystem with base transceiver stations and base station controllers, a network switching subsystem with mobile switching centers, home and visitor location registers, and connections to public switched telephone networks.
This document discusses wireless communication and GSM networks. It provides an overview of multiple access techniques used in wireless networks like TDMA, FDMA, and CDMA. It then describes the development and standards of GSM networks and how they were created to provide a digital cellular standard across Europe to resolve issues with different analog 1G systems. Finally, it summarizes the call setup process in a GSM network for a mobile terminated call, including analyzing the number, interrogating the HLR and MSC/VLR, generating a temporary MSRN, and initiating paging to locate the called subscriber.
The document discusses broadband services provided by BSNL. It defines broadband as a high-speed, always-on internet connection with a minimum download speed of 256 kbps. Broadband offers advantages like fast access to the internet, video on demand, interactive gaming, audio/video conferencing, and distance learning. BSNL provides broadband through various wired and wireless technologies depending on factors like population density, existing infrastructure, government policies, and technology evolution. The network architecture has three parts - the last mile access network connecting subscribers, a metro area network comprising the core network, and service provisioning equipment at the provider's premises.
1) Data communication involves transmitting information from a source to a receiver using a medium. The basic components are a source that generates the data, a medium that carries the data, and a receiver that obtains the data.
2) There are three main types of transmission: simplex allows transmission in one direction only, half duplex allows transmission in two directions but not simultaneously, and full duplex allows simultaneous two-way transmission using two channels.
3) Data is transmitted as a series of 1s and 0s using a code, such as ASCII, that defines each symbol. Transmission can be parallel, with all bits sent at once on separate lines, or serial, with bits sent one after the other on
This document summarizes broadband access techniques, specifically digital subscriber line (DSL) technology. It describes the basic applications of broadband like web browsing, video on demand, and fast file transfers. It then provides a comparative study of download speeds using different technologies like dialup, ISDN, ADSL, and cable modem. The rest of the document defines different types of DSL technologies like ADSL, HDSL, SDSL, RADSL, and VDSL and how they work. It concludes with details about how ADSL uses different frequencies to provide multiple channels for data and voice without interference.
This document is a seminar report submitted by Rajan Meena to fulfill requirements for a Bachelor of Technology degree from Rajasthan Technical University. The report summarizes Rajan's 28-day training with Bharat Sanchar Nigam Limited (BSNL), India's state-owned telecommunications company. The report provides an overview of BSNL's role in India's telecommunications sector and describes key components of BSNL's basic telecommunications network, including call setup, electronic exchanges, carrier rooms, main distribution frames, and power plants. It also covers topics taught during the training like leased lines, intranets, corporate networks, Wi-Fi, WiMAX, and GSM.
http://inarocket.com
Learn BEM fundamentals as fast as possible. What is BEM (Block, element, modifier), BEM syntax, how it works with a real example, etc.
How to Build a Dynamic Social Media PlanPost Planner
Stop guessing and wasting your time on networks and strategies that don’t work!
Join Rebekah Radice and Katie Lance to learn how to optimize your social networks, the best kept secrets for hot content, top time management tools, and much more!
Watch the replay here: bit.ly/socialmedia-plan
Lightning Talk #9: How UX and Data Storytelling Can Shape Policy by Mika Aldabaux singapore
How can we take UX and Data Storytelling out of the tech context and use them to change the way government behaves?
Showcasing the truth is the highest goal of data storytelling. Because the design of a chart can affect the interpretation of data in a major way, one must wield visual tools with care and deliberation. Using quantitative facts to evoke an emotional response is best achieved with the combination of UX and data storytelling.
This document provides an overview of Wideband Code Division Multiple Access (WCDMA) technology. It discusses the basics of WCDMA including that it uses direct sequence spread spectrum technology and differentiates users through the use of spreading codes. It also describes key aspects of WCDMA such as power control, handovers between cells, and current market adoption of WCDMA networks. The document aims to inform readers about the specifications and advantages of the 3G wireless standard known as WCDMA.
1. The document discusses performance enhancement of WiMAX mobile handover using OFDM with M-QAM modulation and best relay selection.
2. It analyzes the bit error rate performance of M-QAM OFDM systems for different modulation schemes, numbers of relays, and subchannels.
3. The results show that M-QAM OFDM with best relay selection provides higher performance and lower error communication compared to other techniques.
This document summarizes information about Bharat Sanchar Nigam Limited (BSNL), the seventh largest telecommunications company in the world. It provides an overview of BSNL's services and sections within telephone exchanges, including the main distribution frame room, power room, PCM room, switch room, optical fiber cable section, broadband section, and mobile section. It also describes technologies used like DWDM, signaling, PDH and SDH multiplexing hierarchies, and defines key terms like STM.
This document analyzes the capacity of MIMO wireless channels when accounting for impairments from physical transceiver hardware limitations. It is shown that when including the effects of transceiver impairments like non-linearities, phase noise, and quantization noise, the capacity of MIMO channels reaches a finite limit as SNR increases, rather than increasing without bound. This results in a zero multiplexing gain, unlike the ideal case without impairments. However, the relative capacity increase from MIMO over single-antenna channels remains at least as large when including impairments. Various figures are presented showing the capacity and multiplexing gain for different channel models and transceiver configurations. The document concludes by stating the analysis provides insights into understanding
This document provides an overview of CDMA and WiMAX technologies as well as the components that make up a BSS (Base Station Subsystem) in a CDMA network, including the BSC (Base Station Controller) and BTS (Base Transceiver Station). It describes the functions of the BSC and BTS, their interfaces, and configurations including components like the CIPS (Common Interface Processing Subrack) in the BSC and modules in the DBS3900 distributed antenna system.
Analysis of WiMAX Physical Layer Using Spatial Multiplexing Under Different F...CSCJournals
WiMAX is defined as Worldwide Interoperability for Microwave Access by the WiMAX Forum and its industry. WiMAX is basically a wireless digital communication system which is also known as IEEE 802.16 standard intended for wireless \"metropolitan area networks\". WiMAX is based upon OFDM multiplexing technique. It was developed in order to provide high speed data rates to the users located in those areas also where broadband wireless coverage is not available. MIMO systems also play an important role in the field of wireless communication by allowing data to be transmitted and received over different antennas. WiMAX-MIMO systems are developed to improve the performance of WiMAX system. This paper analyzes WiMAX-MIMO system for different modulation schemes with different CC code rates under different fading channels (Rician and Nakagami channel). Spatial Multiplexing technique of MIMO system is used for the simulation purpose. Analysis has been done in the form of Signal-to Noise Ratio (SNR) vs Bit Error Rate (BER) plots.
seminar paper on BROADBAND OVER POWER LINES. It is the method of data transfer through the existing power lines.
"Wherever electricity is available there could be broadband"
This document discusses the design of terrestrial microwave links. It begins with an introduction to microwave links and their basic components - transmitters, towers, antennas, and receivers. Antennas must have line-of-sight between sites. The document then covers topics like frequency standards, polarization, antenna types, link budgets, and operating frequencies. It provides block diagrams of transmitter and receiver base stations. Key components like mixers, filters, amplifiers and their functions are described. Signal spreading in W-CDMA systems is also explained. Technical characteristics of microwave point-to-point links are outlined.
This document provides a summary of key concepts in GSM RF including:
1) GSM network services like bearer, tele, and supplementary services that modify basic services.
2) GSM frequency bands like 900MHz and 1800MHz with uplink and downlink carrier frequencies.
3) Concepts like ciphering, authentication, equalization, and interleaving used to secure transmissions and combat multipath fading.
Public Switched Telephone Network (PSTN)J.T.A.JONES
The document discusses various aspects of the Public Switched Telephone Network (PSTN). It covers topics like modulation/demodulation schemes used to convert between analog and digital signals, the bandwidth of telephone lines, traditional modem standards like V.32, V.90, ADSL, techniques used for multiplexing like TDM and WDM, and components within switching offices. It provides technical details on how analog voice signals are converted to digital, transmitted through digital trunks, and switched within the network.
DYNAMIC OPTIMIZATION OF OVERLAP-AND-ADD LENGTH OVER MIMO MBOFDM SYSTEM BASED ...ijwmn
An important role performed by Zero Padding (ZP) in multi-band OFDM (MB-OFDM) System. This role
show for low-complexity in résistance against multipath interference by reducing inter-carrier interference
(ICI) and eliminating the inter-symbol interference (ISI) Also, zero-padded suffix can be used to eliminate
ripples in the power spectral density in order to conform to FCC requirements. At the receiver of MB-OFDM system needs to use of a technique called as overlap-and-add (OLA). Which maintain the circular convolution property and take the multipath energy of the channel.In this paper, we proposed a method of performing overlap-and-add length for zero padded suffixes. Then,we studied the effect of this method, dynamic optimization of overlap-and-add (OLA) equalization, on the performance of MIMO MBOFDM system on Bit Error Rate (BER) with AWGN channel and SalehValenzuela (S-V) Multipath channel Model.In the dynamic optimization OLA, the Length of ZP depends on length of channel impulse response (CIR).
These measures, based on SNR, insert the ZP according to the measurement.Dynamic optimization of length of ZP improves the Performance of MIMO MBOFDM system. In fact wedeveloped a technique to select the length of ZP as function of SNR and CIR estimate. In our simulation
this technique improve to 0.6 dB at BER=10-2 with a multipath channels CM4
This document provides a summary of an industrial training presentation at MTNL. It introduces MTNL and describes key topics covered during the training, including switching, signaling, broadband, and transmission. It discusses these topics in detail and provides examples of projects undertaken and steps that can be taken to improve quality of service in 3G networks. The document concludes with a summary of field training experiences at different MTNL locations.
A Survey on Emerging WiMAX Antenna Technologies and Slotted Microstrip Patch ...IRJET Journal
This document discusses various antenna technologies for WiMAX applications, including SISO, SIMO, MISO, MIMO and AAS modes. It also reviews slotted microstrip patch antennas, specifically double C-slot and C-slot designs. Key findings include:
1) Slotted microstrip patch antennas can improve gain, return loss and VSWR over conventional patch antennas for WiMAX.
2) A double C-slot design achieved a return loss of -31.6 dB and gain of 6.4 dBi, outperforming a C-slot antenna.
3) Slotted designs provide a 37% reduction in antenna size compared to conventional square patches.
Data Transmission Analysis using MW-5000 at 5.8 GHz Frequency IJECEIAES
This document summarizes an experiment on data transmission analysis using a MW-5000 module at 5.8 GHz frequency. The experiment found that the duration for data transmission depends on the length of the message and the baud rate setting. Testing various message lengths at a fixed baud rate of 4800 resulted in similar transmission durations. However, transmitting the same message at different baud rates showed that higher baud rates reduced the transmission duration. Specifically, a message sent at 4800 baud took 1.14 seconds while at 9600 baud it took 0.60 seconds. The document concludes that transmission duration is influenced by message length and baud rate.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
DYNAMIC OPTIMIZATION OF OVERLAPAND- ADD LENGTH OVER MBOFDM SYSTEM BASED ON SN...cscpconf
An important role performed by Zero Padding (ZP) in multi-band OFDM (MB-OFDM) System.
This role show for low-complexity in résistance against multipath interference by reducing
inter-carrier interference (ICI) and eliminating the inter-symbol interference (ISI) Also, zeropadded
suffix can be used to eliminate ripples in the power spectral density in order to conform
to FCC requirements.
At the receiver of MB-OFDM system needs to use of a technique called as overlap-and-add
(OLA). Which maintain the circular convolution property and take the multipath energy of the
channel.
In this paper, we proposed a method of performing overlap-and-add length for zero padded
suffixes. Then, we studied the effect of this method, dynamic optimization of overlap-and-add
(OLA) equalization, on the performance of MBOFDM system on Bit Error Rate (BER) with
AWGN channel and Saleh-Valenzuela (S-V) Multipath channel Model.
In the dynamic optimization OLA, the Length of ZP depends on length of channel impulse
response (CIR). These measures, based on SNR, insert the ZP according to the measurement.
Dynamic optimization of length of ZP improves the Performance of MBOFDM system. In fact
we developed a technique to select the length of ZP as function of SNR and CIR
estimate(repetition). In our simulation this technique improve to 3 dB at BER=10-2 with a
multipath channels CM4.
An important role performed by Zero Padding (ZP) in multi-band OFDM (MB-OFDM) System.
This role show for low-complexity in résistance against multipath interference by reducing
inter-carrier interference (ICI) and eliminating the inter-symbol interference (ISI) Also, zeropadded
suffix can be used to eliminate ripples in the power spectral density in order to conform
to FCC requirements.
At the receiver of MB-OFDM system needs to use of a technique called as overlap-and-add
(OLA). Which maintain the circular convolution property and take the multipath energy of the
channel.
In this paper, we proposed a method of performing overlap-and-add length for zero padded
suffixes. Then, we studied the effect of this method, dynamic optimization of overlap-and-add
(OLA) equalization, on the performance of MBOFDM system on Bit Error Rate (BER) with
AWGN channel and Saleh-Valenzuela (S-V) Multipath channel Model.
In the dynamic optimization OLA, the Length of ZP depends on length of channel impulse
response (CIR). These measures, based on SNR, insert the ZP according to the measurement.
Dynamic optimization of length of ZP improves the Performance of MBOFDM system. In fact
we developed a technique to select the length of ZP as function of SNR and CIR
estimate(repetition). In our simulation this technique improve to 3 dB at BER=10-2 with a
multipath channels CM4.
802.16e provides enhancements to 802.16-2004 to support subscriber stations moving at vehicular speeds. It specifies a system for combined fixed and mobile broadband wireless access using Scalable OFDMA technology. Mobile WiMAX supports seamless handoff between base stations, sleep and idle modes for power management, and smart antenna technologies like beamforming. It can offer full mobility and compete with 3G for IP traffic with peak data rates up to 63Mbps download and 28Mbps upload in a 10MHz channel.
This document summarizes research on improving the performance of WiMAX systems using FEC zigzag coding and MIMO techniques. It first provides background on WiMAX and discusses how OFDM, MIMO, and various channel coding schemes like zigzag codes work. It then evaluates the bit-error rate performance of WiMAX systems using zigzag-coded modulation with different code rates and lengths. The results show zigzag coding presents stronger error correction than Reed-Solomon with Convolutional coding. Encoding and decoding of zigzag codes is explained, along with how concatenated zigzag codes provide even stronger error correction through interleaving and turbo processing.
IEEE 802.16 is a standard for wireless broadband access that uses orthogonal frequency-division multiplexing (OFDM) and orthogonal frequency-division multiple access (OFDMA). OFDMA divides the available carriers into subchannels that can be allocated to different users with varying modulation schemes and coding levels depending on channel conditions. For non-line-of-sight deployments, OFDMA provides mechanisms like power concentration in subchannels, space diversity, and selective coding and modulation to mitigate higher path losses and multipath fading. Same frequency networks are also supported through OFDM's ability to equalize signals from multiple synchronized transmitters.
1. Industrial Training at B.S.N.L. Training Report’12
CAP divides the signals of the telephone line into three bands: voice, upstream channel
and downstream channel. Voice conversations are carried in the 0 to 4
KHz band as they are in all POTS circuits. The upstream channel that carries data
from the user to the server is between 25 and 160 KHz. The downstream channel begins
at 240KHz with a maximum of 1.5 MHz which depends on a number of conditions
such as distance, line noise and number of users. CAP by keeping the three channels
widely separated, minimises the possibility of interference both between channels on one
line and signals on different lines.
DMT also operates by dividing signals into separate channels without using two quite
broad channels for upstream and downstream. The modulation technique that has
become standard for ADSL is called the Discrete Multitone Technique, which combines
QAM and FDM. In ADSL, the available bandwidth of 1.104 MHz is divided into 256
channels. Each channel uses a bandwidth of 4.312 KHz. Each channel is 4KHz wide with
a guard band of .312KHz.. Hence the name Discrete Multitone.
Each sub carrier can support maximum15 number of bits. Depending on signal to noise
ratio for that sub carrier, a decision is taken as to how many bits that particular sub
carrier can support. Every channel is monitored and if the quality is low, the signal is
shifted to another channel. DMT constantly shifts signals between different channels,
looking for the best channels for transmission and reception. Moreover, some of the
lower frequency channels, are used as bi- directional channels for upstream and
downstream. Keeping up with the quality of all channels, monitoring and sorting the
information on the bi-directional
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Wireless Access
T echnologies
Wi-Fi stands for Wireless Fidelity. As the words indicates, the system seeks to do away
with-wires. This system is known as wireless LAN, as with Wi-Fi we can connect different
computers in a LAN using radio waves. This is as shown below in Fig-1.
Figure 1
This standard is known as IEEE 802 .11. There are different versions of this standard
available. They are 802.11b, 802.11a & 802.11g. A comparison of the different standards
is given below. WiFi generally refers to any type of IEEE
802.11 standard.
Wi-Max
WiMAX is an acronym that stands for Worldwide Interoperability for Microwave Access,
a certification mark for products that pass conformity and interoperability tests for the
IEEE 8802.16 standards.(IEEE 802.16 is working group number 16 of IEEE 802
specializing in point-to-multipoint Broadband wireless access). WiMAX covers wider,
metropolitan or rural areas. It can provide data rates up to 75 megabits per second
(Mbps) per base station with typical cell sizes of 2 to 10 kilometers. This is enough
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bandwidth to simultaneously support (through a single base station) more than 60
businesses with T1/E1-type connectivity and hundreds of homes with DSL-type
connectivity. It will provide fixed, portable, and eventually mobile wireless broadband
connectivity and also provides POTS services.
WiMAX actually provide two forms of wireless service :
1. Non-line-of-sight, WiFi sort of service, where a small antenna on your
computer connects to the tower. In this mode, WiMAX uses a lower
frequency range – 2 GHz to 11 GHz
2. Line-of-sight service, where a fixed dish antenna points straight at the WiMAX
tower from a rooftop or pole. Line-of-sight transmissions use higher frequencies,
with ranges reaching a possible 66 GHz.
IEEE 802.16 Specifications
Range - 30-mile (50-km) radius from base station
Speed - 70 megabits per second
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Line-of-sight not needed between user and base station
Frequency bands - 2 to 11 GHz and 10 to 66 GHz
Two key features of Wi Max is the use of OFDM (Orthogonal Frequency Division
Multiplexing) and Adaptive modulation techniques for achieving greater bit rates and
stable connection. In OFDM, the data will be sent over narrow band carriers
transmitted in parallel at different frequencies. These carrier frequencies are
closely spaced and they are orthogonal. In adaptive modulation, depending on the signal
to Noise ratio (SNR) value of the radio link, the modulations will the
automatically changed and bit rates will be adjusted accordingly. This also ensures a
stable connectivity between the subscriber station and the Wi Max base station.
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Overview of the GSM RF Interfaces
Interfaces For the connection of the different nodes in the GSM network, different
interfaces are defined in the GSM specifications. The GSM interfaces
discussed in this lesson are:
Air interface or U m –interface
The Air Interface is the interface between the BTS (Base Transceiver
Station) and the MS (Mobile Station). The air interface is required for
supporting:
— Universal use of any compatible mobile station in a GSM
network
— A maximum spectral efficiency
A bis -interface
The A bis -interface is the interface between the BSC (Base Station
Controller) and the BTS. The interface comprises traffic and control
channels. Functions implemented at the A bis -interface are:
— Voice-data traffic exchange
— Signaling exchange between the BSC and the BTS
— Transporting synchronization information from the BSC to the
BTS
A-interface
The A-interface is the interface between the BSC and the MSC.
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The U m –interface
Introduction One of the most important interfaces is the U m or Air interface. This
interface is thoroughly specified to achieve a full compatibility
between mobile stations of various manufacturers and networks of
different operators.
FDMA and To achieve a high spectral efficiency in the cellular network a
TDMA combination of FDMA (Frequency Division Multiple Access) and
methods TDMA (Time Division Multiple Access) is used. The FDMA part
involves the division by frequency of the 25 MHz bandwidth into
124 carrier frequencies spaced 200 KHz for GSM-900. For GSM-
1800 the frequency spectrum of the 75 MHz bandwidth is divided
into 374 carrier frequencies spaced 200 KHz. One or more
frequencies are assigned to each BTS. Each of these carrier
frequencies is then divided in time, using a TDMA scheme to
increase the number of channels per carrier frequency.
Each carrier frequency channel carries eight time-division
multiplexed physical channels. A physical channel is determined by
the carrier frequency (or a number of carrier frequencies and a
defined hopping sequence) and the timeslot number. A mobile station
can transmit speech data only during its assigned timeslot.
Uplink and In the frequency range specified for the GSM-900 mobile radio
downlink networks, 124 frequency channels with a bandwidth of 200 KHz are
available for both the uplink and downlink direction. The uplink
(mobile station to BTS) uses the frequencies between 890 MHz and
915 MHz and the downlink (BTS to mobile station) uses
the frequencies between 935 MHz and 960 MHz. The duplex spacing,
the spacing between the uplink and downlink channel, is 45 MHz.
GSM-1800 uses a similar scheme. The difference is that for GSM-
1800 the uplink uses the frequencies between 1710 MHz and 1785
MHz and the downlink the frequencies between 1805 MHz and 1880
MHz. The duplex spacing is 95 MHz.
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BASIC TYPES OF POWER PLANTS AND SPECIFICATIONS
Classification of power plants (3 piece)
-Power plant comprises 3
parts
-Float Rectifier
-Battery Charger
-Switching Cubicle.
Power plants are classified based on their capacity.
Feature Small exchange Medium exchange Large exchange
power plants power plants power plants
Capacity: 5/12A 25/50A > 50A
Input Single Phase Single Phase Three Phase
Paralleling Not possible Only manual Auto paralleling is
of rectifier paralleling is possible
possible
Another classification of power plant is
Single unit type Two unit Type Three unit type
F.R,B.C and SC -One unit is FC/BC/SWC -FR, BC, and SC are
will be in Single (Float rectifier cum in individual units.
container battery charger, cum
Switching cubicle )
Ex: 5/12A PP - another unit is FR
Note: Nowadays mostly 2 units p/p are used with maintenance
free batteries and all transmission power plant are 2-unit type only. The latest
being P/P of SMPS with VRLA batteries.
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SWITCHING SYSTEMS
Introduction
The telephone is a telecommunication device that is used to transmit and receive
electronically or digitally encoded speech between two or more people conversing. It is one of
the most common household appliances in the developed world today. Most telephones operate
through transmission of electric signals over a complex telephone network which allows almost
any phone user to communicate with almost any other user.
Telecommunication networks carry information signals among entities, which are
geographically far apart. An entity may be a computer or human being, a facsimile machine, a
teleprinter, a data terminal and so on. The entities are involved in the process of information
transfer that may be in the form of a telephone conversation (telephony) or a file transfer
between two computers or message transfer between two terminals etc.
With the rapidly growing traffic and untargeted growth of cyberspace,
telecommunication becomes a fabric of our life. The future challenges are enormous as we
anticipate rapid growth items of new services and number of users. What comes with the
challenge is a genuine need for more advanced methodology supporting analysis and design of
telecommunication architectures. Telecommunication has evaluated and growth at an explosive
rate in recent years and will undoubtedly continue to do so.
The communication switching system enables the universal connectivity. The universal
connectivity is realized when any entity in one part of the world can communicate with any
other entity in another part of the world. In many ways telecommunication will acts as a
substitute for the increasingly expensive physical transportation.
The telecommunication links and switching were mainly designed for voice
communication. With the appropriate attachments/equipments, they can be used to transmit
data. A modern society, therefore needs new facilities including very high bandwidth switched
data networks, and large communication satellites with small, cheap earth antennas.
Voice Signal Characteristics
Telecommunication is mainly concerned with the transmission of messages between
two distant points. The signal that contains the messages is usually converted into electrical
waves before transmission. Our voice is an analog signal, which has amplitude and frequency
characteristics.
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Voice frequencies: - The range of frequencies used by a communication device
determines the communication channel, communicating devices, and bandwidth or information
carrying capacity. The most commonly used parameter that characterizes an electrical signal is
its bandwidth of analog signal or bit rate if it is a digital signal. In telephone system, the
frequencies it passes are restricted to between 300 to 3400 Hz.
In the field of telecommunications, a Telephone exchange or a Telephone switch is a
system of electronic components that connects telephone calls. A central office is the physical
building used to house inside plant equipment including telephone switches, which make
telephone calls "work" in the sense of making connections and relaying the speech information.
Switching system fundamentals
Telecommunications switching systems generally perform three basic functions: they
transmit signals over the connection or over separate channels to convey the identity of the
called (and sometimes the calling) address (for example, the telephone number), and alert (ring)
the called station; they establish connections through a switching network for conversational
use during the entire call; and they process the signal information to control and supervise the
establishment and disconnection of the switching network connection.
In some data or message switching when real-time communication is not needed, the
switching network is replaced by a temporary memory for the storage of messages. This type of
switching is known as store-and-forward switching.
Signaling and control
The control of circuit switching systems is accomplished remotely by a specific form of
data communication known as signaling. Switching systems are connected with one another by
telecommunication channels known as trunks. They are connected with the served stations or
terminals by lines.
In some switching systems the signals for a call directly control the switching devices
over the same path for which transmission is established. For most modern switching systems
the signals for identifying or addressing the called station are received by a central control that
processes calls on a time-shared basis. Central controls receive and interpret signals, select and
establish communication paths, and prepare signals for transmission. These signals include
addresses for use at succeeding nodes or for alerting (ringing) the called station.
Most electronic controls are designed to process calls not only by complex logic but
also by logic tables or a program of instructions stored in bulk electronic memory. The tabular
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technique is known as translator. The electronic memory is now the most accepted technique
and is known as stored program control (SPC). Either type of control may be distributed among
the switching devices rather than residing centrally. Microprocessors on integrated circuit chips
are a popular form of distributed stored program control.
Switching fabrics
Space and time division are the two basic techniques used in establishing connections.
When an individual conductor path is established through a switch for the duration of a call, the
system is known as space division. When the transmitted speech signals are sampled and the
samples multiplexed in time so that high-speed electronic devices may be used simultaneously
by several calls, the switch is known as time division.
In the early stages of development in telecommunication, manual switching methods
were deployed. But later on to overcome the limitations of manual switching; automatic
exchanges, having Electro-mechanical components, were developed. Strowger exchange, the
first automatic exchange having direct control feature, appeared in 1892 in La Porte (Indiana).
Though it improved upon the performance of a manual exchange it still had a number of
disadvantages, viz., a large number of mechanical parts, limited availability, inflexibility, bulky
in size etc. As a result of further research and development, Crossbar exchanges,having an
indirect control system, appeared in 1926 in Sweden.
The Crossbar exchange improved upon many short- comings of the Strowger system.
However, much more improvement was expected and the revolutionary change in field of
electronics provided it. A large number of moving parts in Register, marker, Translator, etc.,
were replaced en-block by a single computer. This made the exchange smaller in size, volume
and weight, faster and reliable, highly flexible, noise-free, easily manageable with no
preventive maintenance etc.
Influence of Electronics in Exchange Design.
When electronic devices were introduced in the switching systems, a new concept of
switching evolved as a consequence of their extremely high operating speed compared to their
former counter-parts, i.e., the Electro-mechanical systems, where relays, the logic elements in
the electromechanical systems, have to operate and release several times which is roughly equal
to the duration of telephone signals to maintain required accuracy.
Research on electronic switching started soon after the Second World War, but
commercial fully electronic exchange began to emerge only about 30 years later. However,
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electronic techniques proved economic for common control systems much earlier. In
electromechanical exchanges, common control systems mainly used switches and relays, which
were originally designed for use in switching networks. In common controls, they are operated
frequently and so wear out earlier. In contrast, the life of an electronic device is almost
independent of its frequency of operation. This gave a motivation for developing electronic
common controls and resulted in electronic replacements for registers, markers, translators etc.
having much greater reliability than their electromechanical predecessors.
In electromechanical switching, the various functions of the exchange are achieved by
the operation and release of relays and switch (rotary or crossbar) contacts, under the direction
of a Control Sub-System. These contracts are hard - wired in a predetermined way. The
exchange dependent data, such as subscriber’s class of service, translation and routing,
combination signaling characteristics are achieved by hard-ware and logic, by a of relay sets,
grouping of same type of lines, strapping on Main or Intermediate Distribution Frame or
translation fields, etc. When the data is to be modified, for introduction of a new service, or
change in services already available to a subscriber, the hardware change ranging from
inconvenient to near impossible, are involved.
In an SPC exchange, a processor similar to a general-purpose computer is used to
control the functions of the exchange. All the control functions, represented by a series of
various instructions, are stored in the memory. Therefore the processor memories hold all
exchange dependent data. such as subscriber date, translation tables, routing and charging
information and call records. For each call processing step. e.g. for taking a decision according
to class of service, the stored data is referred to, Hence, this concept of switching. The
memories are modifiable and the control program can always be rewritten if the behavior or the
use of system is to be modified. This imparts and enormous flexibility in overall working of the
exchange.
Digital computers have the capability of handling many tens of thousands of
instructions every second, Hence, in addition to controlling the switching functions the same
processor can handle other functions also. The immediate effect of holding both the control
programme and the exchange data, in easily alterable memories, is that the administration can
become much more responsive to subscriber requirements. both in terms of introducing new
services and modifying general services, or in responding to the demands of individual
subscriber. For example, to restore service on payment of an overdue bill or to permit change
from a dial instrument to a multi frequency sender, simply the appropriate entries in the
subscriber data-file are to be amended. This can be done by typing- in simple instructions from
a teletypewriter or visual display unit. The ability of the administration to respond rapidly and
effectively to subscriber requirements is likely to become increasingly important in the future.
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The modifications and changes in services which were previously impossible be
achieved very simply in SPC exchange, by modifying the stored data suitably. In some cases,
the subscribers can also be given the facility to modify their own data entries for supplementary
services, such as on-demand call transfer, short code (abbreviated) dialing, etc.
The use of a central processor also makes possible the connection of local and remote
terminals to carry out man-machine dialogue with each exchange. Thus, the maintenance and
administrative operations of all the SPC exchanges in a network can be performed from a single
centralized place. The processor sends the information on the performance of the network, such
as, traffic flow, billing information, faults, to the centre, which carries out remedial measures
with the help of commands. Similarly, other modifications in services can also be carried out
from the remote centre. This allows a better control on the overall performance of the network.
As the processor is capable of performing operations at a very high speed, it has got
sufficient time to run routine test programmes to detect faults, automatically. Hence, there is no
need to carry out time consuming manual routine tests.
In an SPC exchange, all control equipment can be replaced by a single processor. The
processor must therefore be quite powerful, typically it must process hundreds of calls per
second, in addition to performing other administrative and maintenance tasks. However, totally
centralized control has drawbacks. The software for such a central processor will be
voluminous, complex, and difficult to develop reliably. Moreover, it is not a good arrangement
from the point of view of system security, as the entire system will collapse with the failure of
the processor. These difficulties can be overcome by decentralizing the control. Some routine
functions such as scanning, signal distributing, marking, which are independent of call
processing, can be delegated to auxiliary or peripheral processors.
Stored program control (SPC) has become the principal type of control for all types of
new switching systems throughout the world, including private branch exchanges, data and
Telex systems. Two types of data are stored in the memories of electronic switching systems.
One type is the data associated with the progress of the call, such as the dialed address of the
called line.
Another type, known as the translation data, contains infrequently changing
information, such as the type of service subscribed to by the calling line and the information
required for routing calls to called numbers. These translation data, like the program, are stored
in a memory, which is easily read but protected to avoid accidental erasure. This information
may be readily changed, however, to meet service needs. The flexibility of a stored program
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also aids in the administration and maintenance of the service so that system faults may be
located quickly.
SPC exchanges can offer a wider range of facilities than earlier systems. In addition,
the facilities provided to an individual customer can be readily altered by changing the
customer’s class-of-service data stored in memory. Moreover, since the processor’s stored data
can be altered electronically,some of these facilities can be controlled by customers. Examples
include:-
1. Call barring (outgoing or incoming): The customer can prevent unauthorized calls
being made and can prevent incoming calls when wishing to be left in peace.
2. Call waiting: The ‘Call waiting’ service notifies the already busy subscriber of a third
party calling him.
3. Alarm calls: The exchange can be instructed to call the customer at a pre-arranged time
(e.g. morning alarm).
4. Call Forwarding: The subscriber having such a feature can enable the incoming calls
coming to his telephone to be transferred to another number during his absence.
5. Conference calls: Subscriber can set up connections to more than one subscriber and
conduct telephone conferences under the provision of this facility.
6. Dynamic Barring Facility: Subscriber having STD/ISD facilities can dynamically lock
such features in their telephone to avoid misuse. Registering and dialing a secret code will
extend such such a facility.
7. Abbreviated Dialing: Most subscribers very often call only limited group of telephone
numbers. By dialing only prefix digit followed by two selection digits, subscribers can call up
to 100 predetermined subscribers connected to any automatic exchange. This shortens the
process of dialing all the digits.
8. Malicious call Identification: Malicious call identification is done immediately and the
information is obtained in the print out form either automatically or by dialing an identification
code.
9. Do Not Disturb: This facility enables the subscriber to free himself from attending his
incoming calls. Using this facility the calls coming to the subscriber can be routed to an
operator position or to an answering machine. The operator position or the machine can inform
the calling subscriber that the called subscriber is temporarily inaccessible. Today SPC is a
standard feature in all the electronic exchanges.
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Implementation of Switching Network.
In an electronic exchange, the switching network is one of the largest sub-system in
terms of size of the equipment. Its main functions are Switching (setting up temporary
connection between two or more exchange terminations), Transmission of speech and signals
between these terminations, with reliable accuracy.
There are two types of electronic switching system. viz. Space division and Time
Division.
Space Division switching System
In a space Division Switching system, a continuous physical path is set up between
input and output terminations. This path is separate for each connection and is held for the
entire duration of the call. Path for different connections is independent of each other. Once a
continuous path has been established., Signals are interchanged between the two terminations.
Such a switching network can employ either metallic or electronic cross points. Previously,
usage of metallic cross-points using reed relays and all were favored. They have the advantage
of compatibility with the existing line and trunk signaling conditions in the network.
Time Division Switching System
In Time Division Switching, a number of calls share the same path on time division
sharing basis. The path is not separate for each connection, rather, is shared sequentially for a
fraction of a time by different calls. This process is repeated periodically at a suitable high rate.
The repetition rate is 8 KHz, i.e. once every 125 microseconds for transmitting speech on
telephone network, without any appreciable distortion. These samples are time multiplexed
with staggered samples of other speech channels, to enable sharing of one path by many calls.
The Time Division Switching was initially accomplished by Pulse Amplitude
Modulation (PAM) Switching. However, it still could not overcome the performance
limitations of signal distortion noise, cross-talk etc. With the advent of Pulse Code Modulation
(PCM), the PAM signals were converted into a digital format overcoming the limitations of
analog and PAM signals. PCM signals are suitable for both transmission and switching. The
PCM switching is popularly called Digital Switching.
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Digital Switching Systems
A Digital switching system, in general, is one in which signals are switched in digital
form. These signals may represent speech or data. The digital signals of several speech samples
are time multiplexed on a common media before being switched through the system.
To connect any two subscribers, it is necessary to interconnect the time-slots of the two
speech samples, which may be on same or different PCM highways. The digitalized speech
samples are switched in two modes, viz., Time Switching and Space Switching. This Time
Division Multiplex Digital Switching System is popularly known as Digital Switching System.
The general architecture of a Digital Switching System is depicted in Fig2.
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General architecture of Digital Switching System
Subs interface
Digital Switch
Trunks interface
Other
exchanges
CONTROL
PROCESSOR
Other auxiliary inter faces
Such as,
(a) Tone generator
(b) Frequency receives
(c) Conference call facility
(d) CCS# 7 Protocol Manager Operation &
(e) V 5.2 access manager Maintenance
Figure-2
The ESS No.1 system was the first fully electronic switching system but not digital.
But later came ESS No.4 system which was digital for trunk portion only. When designed, the
cost of A/D conversion (CODEC) on each subscriber line was seen as prohibitive. So the ESS
No.4 system was acting as a Trunk/Tandem exchange but not as a local exchange. So the main
difficulty for implementing a digital local exchange was the implementation of the subscriber
line interface. This was solved by the introduction of Integrated Circuits, which made the
digital local exchange economically feasible. This implementation handles the following
functions:
B-Battery feed
O-Over-voltage protection (from lightning and accidental power line contact)
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R-Ringing
S-Supervisory Signaling
C-Coding (A/D inter conversion & low pass filtering)
H-Hybrid (2W to 4W conversion)
T-Testing the connectivity of Subscriber
Examples of digital exchanges (switching systems) include CDOT, OCB, AXE, EWSD, 5ESS
etc.
The next evolutionary step was to move the PCM codec from the exchange end
of the customer’s line to the customer’s end. This provides digital transmission over the
customer’s line, which can have a number of advantages. Consider data transmission. If there
is an analog customer’s line, a modem must be added and data can only be transmitted at
relatively slow speeds. If the line is digital, data can be transmitted by removing the codec
(instead of adding a modem). Moreover, data can be transmitted at 64 kbit/s instead of at, say,
2.4 kbit/s. Indeed, any form of digital signal can be transmitted whose rate does not exceed 64
kbit/s. This can include high-speed fax, in addition to speech and data.
This concept had led to the evolution of Integrated services digital network
(ISDN), in which the customer’s terminal equipment and the local digital exchange can be used
to provide many different services, all using 64 kbit/s digital streams. In simple terms, we can
say ISDN provides end-to-end digital connectivity.
Access to an ISDN is provided in two forms:
1. Basic-Rate Access (BRA)
The customer’s line carries two 64 kbit/s “B” channels plus a 16 kbit/s “D”
channel (a common signaling channel) in each direction.
2. Primary Rate Access (PRA)
The line carries a complete PCM frame at 2 Mbit/s in each direction. This
gives the customer 30 circuits at 64 kbit/s plus a common signaling channel, also at 64 kbit/s.
Control of switching systems
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Switching systems have evolved from being manually controlled to being controlled by
relays and then electronically. The change from the manual system to the Strowger step-by-
step system brought about a change from centralized to distributed control. However, as
systems developed and offered more services to customers, it became economic to perform
particular functions in specialized equipments that were associated with connections only when
required, thus, common control was introduced.
Later, the development of digital computer technology enabled different functions to be
performed by the same hardware by using different programs; thus switching system entered
the era of stored-program control (SPC).
There are basically two approaches to organizing stored program control: centralized
and distributed. Early electronic switching systems (ESS) developed during the period 1970-75
almost invariably used centralized control. Although many present day exchange designs
continue to use centralized SPC, with the advent of low cost powerful microprocessors and very
large scale integration (VLSI) chips such as programmable logic arrays (PLA) and
programmable logic controllers (PLC), distributed SPC is gaining popularity.
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Development of exchanges
year
Figure 3
The figure above shows the evolution of electronic switching systems from the manual
switching systems. The figure also depicts the changing scenario from digital switching to
Broadband where the focus will be for high bit rate data transmissions.
Signaling In Telecommunication
A telecommunication network establishes and releases temporary connections, in
accordance with the instructions and information received from subscriber lines and inter
exchange trunks, in form of various signals. Therefore, it is necessary to interchange
information between an exchange and it external environment i.e. between subscriber lines and
exchange, and between different exchanges. Though these signals may differ widely in their
implementation they are collectively known as telephone signals.
A signaling system uses a language, which enables two switching equipments to
converse for the purpose of setting up calls. Like any other language. it possesses a vocabulary
of varying size and varying precision, ie. a list of signals which may also vary in size and a
syntax in the form of a complex set of rules governing the assembly of these signals. This
handout discusses the growth of signaling and various type of signaling codes used in Indian
Telecommunication.
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Types of Signaling
1. Subscriber Line Signaling
2. Inter exchange Signaling
The signaling information exchanged between a subscriber and an exchange for the
establishment and release of a call is termed as Subscriber line signaling. Example for
Subscriber line signaling –Calling subscriber going off-hook, feeding of dial tone to the
subscriber by the exchange, feeding of Ringing current, digits dialed by the subscriber
(Address information) in the form of pulses or tones etc.
The signaling information exchanged between different exchanges via inter exchange
trunks for the routing of calls is termed as Inter exchange Signaling. Earlier in band /out of
band frequencies were used for transmitting signaling information. Later on, with the
emergence of PCM systems, it was possible to segregate the signaling from the speech channel.
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TRANSMISSION SYSTEMS
Telephonic conversation is possible on a single wire connected between two telephones
but distance is limited, approximately 5 to 10 Kms. If two wires are used which run parallel
between two telephones, long distance communication can be provided. However, this is a
costly affair therefore, many different systems of transmission are designed.
What is a Transmission System?
A transmission system consists of two terminals Transmitter and Receiver, with media
for transmission between the two. There may be few repeaters (for amplification) at
intermediate stations if required. There are different types of Transmission systems.
Carrier Systems
This system is installed between two cities and both systems are
connected by two wires called line. It provides three telephonic subscribers conversation
simultaneously. The distance between two cities is 50Km. to 100 Km. These systems work on
230 V AC.
Different Carrier systems are,
3 Channel system
8 Channel system
12 Channel system
24 Channel system
Co-axial cable systems
In the initial stages of Tele –Communication two wires were used as
line (as explained above). The disadvantage is that, it cannot handle more traffic. With the
increasing demand of more simultaneous telephone- calls different measures were adopted. Co-
axial cable is one of them. The systems working on Co-Axial Cables are called Coaxial Cable
systems. After multiplexing telephone calls are transmitted by different coaxial cable systems.
The description is as follows.
A. 4 MHz System
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960 telephone calls are multiplexed by multiplexing equipment and it comes in
this system. This system amplifies the power and transmits on coaxial cable to distant station.
B. 12 MHz System
2700 multiplexed signals are fed in this system for distant end. This system
amplifies the power and makes it suitable for transmission to other stations.
Micro Wave Systems
Microwave working is resorted to provide reliable communication especially in difficult
terrains where communication by coaxial cable and other means cannot be provided. It has the
following advantages.
It can provide a very large bulk of speech circuits.
It can be provided over rough and in-accessible terrain where other types of
communication cannot be economically arranged.
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The fault liability in M/W system is very low. Provision of remote fault
localization and standby microwave channel almost provides uninterrupted
communication.
The annual maintenance cost is very low as compared with other transmission
system.
Pulse Code Modulation System (PCM System)
PCM systems use Time Division Multiplexing technique to provide a number
of circuits on the same transmission medium viz-open wire or underground cable pair of a
channel provided by carrier, coaxial, microwave or satellite system
Time Division Multiplexing
Basically, time division multiplexing involves nothing more than sharing a
transmission medium by a number of circuits in time domain by establishing a sequence of time
slots during which individual channels (circuits) can be transmitted.
Each channel is sampled at a specified rate and transmitted for a fixed
duration. All channels are sampled one by one and transmitted one by one, the cycle is
repeated again and again. The channels are connected to individual gates, which are opened
one by one in a fixed sequence. At the receiving end also similar gates are opened in unison
with the gates at the transmitting end.
The signal received at the receiving end will be in the form of discrete
samples and these are combined to reproduce the original signal. Thus at a given instant of
time, only one channel is transmitted through the medium, and by sequential sampling a
number of channels can be staggered in time as opposed to transmitting all the channel at the
same time as in FDM systems. This staggering of channels in time sequence for transmission
over a common medium is called Time Division Multiplexing (TDM).
To develop a PCM signal from several analogue signals, the following
processing steps are required:
Filtering
Sampling
Quantization
Encoding
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Line Coding
Optical Fiber Systems
Optical fibre is a medium, in which information (voice, data or video) is
transmitted through a glass or plastic fibre, in the form of light, following the transmission
sequence given below:
Information is encoded into electrical signals.
Electrical signals are converted into light signals.
Light travels down the fibre.
A detector changes it into electrical signals at receiver.
Electrical signals are decoded into information.
Recei
Tra
Gat ve Ga
ns
CH 1 ( )
e ) (
te 1 CH
1 1
CH 2 ( ) ) ( 2 CH
2 2
~~
Mediu
CH 3 ( ) m ) ( 3 CH
3 3
CH n ( ) ) ( n CH
n n
Time Division Multiplexing
Multiplexing
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Advantages Of Optical Fibre
Optical Fibre is non conductive (Dielectric)
Electromagnetic immunity
Large Bandwidth
Low Loss
Small, light weight cables
Available in Long lengths
Security
Safety
Universal medium
PDH Fiber Optic Transmission Systems: -
Present telecom technology provides both PDH (Plesiochronous Digital
Hierarchy) and SDH (Synchronous Digital Hierarchy) optical fiber equipments. The PDH
systems are basically used for the Point-to-Point transmission (carrying a signal between two
end points) e.g. for connecting two cities. The different PDH Fiber Optic Transmission Systems
which are used in the network of BSNL, capacity wise, are given below: -
8 Mbps system 120 channels capacity
34 mbps system 480 channels capacity
140 mbps system 1920 channels capacity
565 mbps system 7680 channels capacity
The above PDH Fiber Optic Transmission Systems available either in
separate OLTE (Optical Line Terminating Equipment) and MUX (Multiplexer) or in integrated
OLTE + MUX (OPTIMUX) version housed in a single rack. The application of these systems
depends upon the traffic of that particular route. These PDH Fiber Optic Transmission Systems
are supplied by different manufacturers to BSNL
Main parts of PDH Fiber Optic Transmission Systems: -
Multiplexing Equipments
Line Equipments
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OLTE (Optical Line Terminating Equipment)
Repeater (Regenerator)
Transmission Media (Optical Fiber)
Block diagram of FOTS
O R O
M
E M
Telephon Telephone
e calls U L calls
G L
from/to from/to
Exchange X
N U Exchange
T
E T
E R X
A
E
T
SDH Optical Fiber Systems O
R
It is an international standard networking principle and a multiplexing
method. The name of hierarchy has been taken from the multiplexing method, which is
synchronous, by nature. The evolution of this will assist in improving the economy of
operability and reliability of a digital network
SDH was very quickly perceived to be a better way of deploying optical
networks. SDH played a crucial role in the fast and efficient deployment of high speed
backbone connecting routers. SDH starts its hierarchy at 155.52 mbps and available in different
capacity systems like: -
Name of system Speed Capacity
STM-1 155.52 Mbps 1890 channels
STM –4 622.08 Mbps 7560 channels
STM –16 2.50 Gbps 30,240 channels
STM - 64 10.0 Gbps 1,20,960 channels
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The first attempt to formulate standards for optical transmission started in
USA as SONET (Synchronous Optical Network) The aim of these standards was to simplify
interconnection between network operator by allowing inter connection of equipment from
different venders to the extent that compatibility could be achieved.
When in year 1986 USA reported about SONET, which was developed by
AT&T USA .UK and Japan took the interest in the technique and it was discussed in ITU (T)
[International Telecommunication Union (telecommunication standardization Sector)] which is
a world standard in telecommunication field , and SONET was renamed as SDH (Synchronous
Digital Hierarchy ), after making some modifications in SONET .Thereafter SDH become the
global of transmission system.
Merits of SDH
1. Simplified Multiplexing and De-multiplexing process
2. Direct access to lower speed channel without need to demultiplex the entire high-
speed signal.
3. Enhanced OAM & P: - Due to enhanced Operation, Administration, Maintenance
and Provisioning capabilities user can control the whole network from a central
location i.e. remote supervision and control is very easy.
4. Easy Growth: - Easy growth to high capacity systems.
5. Capable of transporting existing PDH signals.
6. Capable of transporting future broadband signals like, interactive multimedia &
video conferencing.
7. Capable of operating in a multivender and multi-operator environment: - Before
SDH optical solutions for the long distance transmission were intensely vendor
specific but SDH were firm standards for vendor inter operability.
8. Synchronous networking: - SDH supports multi-point, Hub and Ring
Configuration whereas PDH networking only supports Point-to-Point
Configuration.
SDH Network Elements: -
Terminal Multiplexer (TM) – TM an end point device of SDH network, it is used
at terminals of point to point SDH network.
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Add/Drop Multiplexer (ADM) – ADM is network element, which allows
configurable add/drop of a subset of traffic channels from higher rate data stream.
Regenerator (REG): -The most basic element is regenerator. They terminate and
regenerate the optical signal. These are not simple regenerator but have alarm and
performance monitoring capability.
Synchronous Digital Cross Connect (SDXC): -
This device will form the cornerstone of new SDH. They can function as semi
permanent switch for transmission channels and can switch at any level from 64 kbps to STM-
1 under software control .The previous systems like analogue transmission systems and PDH
based digital transmission systems are only point to point or in bus configuration. In bus
configuration repeaters are having drop and insert facility of channels and in point to point
configuration repeaters do not have drop and insert facility. But in both of these configuration if
media breaks or repeater fails, the full system goes out of order.
EXCHANGE
ADM
“A”
E
E X
X C
ADM ADM
C H
H A
A N
N “B” “D”
G
G E
E
ADM
“C”
EXCHANGE
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In SDH this problem is overcome by using other type of configurations
specially RING TYPE as shown in fig.
In the fig. Four nodes (A, B, C, D) are shown, when media between say node
A and B breaks, the traffic interrupted is automatically rerouted between nodes A&B via nodes
D&C.
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Satellite Systems
Long distance communications, particularly to remote locations, using
conventional terrestrial media is both uneconomic and unreliable. A geo-stationary
communication satellite which acts as a repeater hung in the sky can cover a very large
area and provide a reliable and cost effective alternative.
Although satellite communication would seem to be a straightforward extension
of Conventional radio system, the use of satellites for communications brings in new
operational features not found in terrestrial systems. In this hand out, some of the
features of satellite communication are discussed. Basic knowledge of terrestrial radio
systems is assumed.
Structure of a Satellite Link
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