The document provides an overview of digitizing different types of information for computer processing and transmission. It discusses digitizing alphanumeric data using coding standards like ASCII, EBCDIC, and Unicode. Components of information like data, audio, images, and video need to be digitized and encoded before digital transmission and processing by computers. Digitization allows information to be processed and transmitted easily over computer networks while minimizing loss of quality.
This document provides an overview of analog and digital technologies. It discusses the basics of analog signals including amplitude, frequency, and cycles. It also covers digital technologies including digital signals represented as binary digits, clock speed, and pulse duration. The document describes concepts such as frequency spectrum, bandwidth, analog to digital conversion, and digitization of different types of information including alphanumeric data, audio, images, and video. The goal is to explain the basic concepts of analog and digital technologies and how information can be represented and transmitted in both analog and digital forms.
This document provides an overview of digitizing audio by:
1) Taking samples of audio at regular time intervals defined by the sampling rate;
2) Representing the sampled audio values as digital pulse amplitudes using Pulse Amplitude Modulation (PAM);
3) Encoding the digital pulse amplitudes into binary code using Pulse Code Modulation (PCM).
The digitization process allows audio to be processed and transmitted in digital form.
This document provides an overview of analog and digital technologies. It discusses the basic concepts of analog and digital signals including amplitude, frequency, cycles. It explains how information is represented using analog signals and the need to digitize analog signals for computer processing. The document covers analog to digital conversion, data transmission using analog and digital technologies, and examples of voice transmission. It also discusses frequency spectrum, bandwidth, and how communication speed depends on bandwidth and technology. Finally, it gives an overview of digital to analog conversion, digitization of different types of information like audio, and how quality is retained in digital transmission.
This document provides an overview of analog and digital technologies. It discusses the basic concepts of analog and digital signals including amplitude, frequency, cycles, and bandwidth. It explains how information can be represented and transmitted using analog and digital signals. The document also covers analog to digital conversion, digitization of data, audio, images and video. It discusses how quality is retained when transmitting digital data compared to analog. The key points are that digital signals can be easily manipulated for computer processing, transmitted with minimal quality loss, and reconstructed at the receiving end with exact patterns.
This document provides an overview of analog and digital technologies. It discusses areas where analog and digital technologies are applied. It describes the basics of analog signals including amplitude, cycle, and frequency. It also covers the basics of digital signals including pulses, pulse duration, and signal strength. The document discusses analog to digital conversion and digital to analog conversion. It explains that conversion is needed when connecting analog devices to digital networks and vice versa. It also discusses how clock speed impacts execution speed, communication speed, and computer operation speed. Finally, it provides examples of using analog and digital signals to carry both analog and digital data.
This document discusses a proposed low bit rate audio codec algorithm using discrete wavelet transform. The key aspects of the algorithm are:
1. Choosing an optimal wavelet basis for audio signals and determining the optimal decomposition level in the discrete wavelet transform.
2. Applying thresholding to wavelet coefficients to truncate insignificant coefficients, allowing data compression while maintaining suitable peak signal to noise ratio.
3. Comparing performance of the audio codec using discrete wavelet transform to one using discrete wavelet packet transform.
4. Applying a postfiltering technique to improve the quality of the reconstructed audio signal by estimating and subtracting the error in the coded signal.
In order for the Internet of Things to function properly, a reliable wireless technology needs to be available. Radio frequencies are some of the most popular and effective means for IoT communication.
Telecommunications and Network Security PresentationWajahat Rajab
This document provides an overview of telecommunications and network security concepts. It discusses data network types like LANs, WANs, intranets and extranets. It describes the OSI reference model and its layers. Wireless network technologies like FHSS, DSSS and OFDM are explained. Security issues with early WLAN standards like WEP are covered. Improved security protocols like WPA and WPA2 are also summarized. Common network attacks such as DNS poisoning, SYN floods, ARP poisoning and DDoS attacks are defined. Finally, the document outlines virtual private network concepts and components of intrusion detection systems and firewalls.
This document provides an overview of analog and digital technologies. It discusses the basics of analog signals including amplitude, frequency, and cycles. It also covers digital technologies including digital signals represented as binary digits, clock speed, and pulse duration. The document describes concepts such as frequency spectrum, bandwidth, analog to digital conversion, and digitization of different types of information including alphanumeric data, audio, images, and video. The goal is to explain the basic concepts of analog and digital technologies and how information can be represented and transmitted in both analog and digital forms.
This document provides an overview of digitizing audio by:
1) Taking samples of audio at regular time intervals defined by the sampling rate;
2) Representing the sampled audio values as digital pulse amplitudes using Pulse Amplitude Modulation (PAM);
3) Encoding the digital pulse amplitudes into binary code using Pulse Code Modulation (PCM).
The digitization process allows audio to be processed and transmitted in digital form.
This document provides an overview of analog and digital technologies. It discusses the basic concepts of analog and digital signals including amplitude, frequency, cycles. It explains how information is represented using analog signals and the need to digitize analog signals for computer processing. The document covers analog to digital conversion, data transmission using analog and digital technologies, and examples of voice transmission. It also discusses frequency spectrum, bandwidth, and how communication speed depends on bandwidth and technology. Finally, it gives an overview of digital to analog conversion, digitization of different types of information like audio, and how quality is retained in digital transmission.
This document provides an overview of analog and digital technologies. It discusses the basic concepts of analog and digital signals including amplitude, frequency, cycles, and bandwidth. It explains how information can be represented and transmitted using analog and digital signals. The document also covers analog to digital conversion, digitization of data, audio, images and video. It discusses how quality is retained when transmitting digital data compared to analog. The key points are that digital signals can be easily manipulated for computer processing, transmitted with minimal quality loss, and reconstructed at the receiving end with exact patterns.
This document provides an overview of analog and digital technologies. It discusses areas where analog and digital technologies are applied. It describes the basics of analog signals including amplitude, cycle, and frequency. It also covers the basics of digital signals including pulses, pulse duration, and signal strength. The document discusses analog to digital conversion and digital to analog conversion. It explains that conversion is needed when connecting analog devices to digital networks and vice versa. It also discusses how clock speed impacts execution speed, communication speed, and computer operation speed. Finally, it provides examples of using analog and digital signals to carry both analog and digital data.
This document discusses a proposed low bit rate audio codec algorithm using discrete wavelet transform. The key aspects of the algorithm are:
1. Choosing an optimal wavelet basis for audio signals and determining the optimal decomposition level in the discrete wavelet transform.
2. Applying thresholding to wavelet coefficients to truncate insignificant coefficients, allowing data compression while maintaining suitable peak signal to noise ratio.
3. Comparing performance of the audio codec using discrete wavelet transform to one using discrete wavelet packet transform.
4. Applying a postfiltering technique to improve the quality of the reconstructed audio signal by estimating and subtracting the error in the coded signal.
In order for the Internet of Things to function properly, a reliable wireless technology needs to be available. Radio frequencies are some of the most popular and effective means for IoT communication.
Telecommunications and Network Security PresentationWajahat Rajab
This document provides an overview of telecommunications and network security concepts. It discusses data network types like LANs, WANs, intranets and extranets. It describes the OSI reference model and its layers. Wireless network technologies like FHSS, DSSS and OFDM are explained. Security issues with early WLAN standards like WEP are covered. Improved security protocols like WPA and WPA2 are also summarized. Common network attacks such as DNS poisoning, SYN floods, ARP poisoning and DDoS attacks are defined. Finally, the document outlines virtual private network concepts and components of intrusion detection systems and firewalls.
This document provides an introduction and overview of digital communications. It outlines the key elements of a digital communication system including the information source, source encoder, channel encoder, digital modulator, communication channel, digital demodulator, channel decoder, and source decoder. It describes common communication channels such as wireline channels using twisted pair and coaxial cable, fiber optic channels, wireless electromagnetic channels for ground wave, sky wave and line of sight propagation, and underwater acoustic channels. It also discusses mathematical models for communication channels, including the additive noise channel, linear filter channel, and linear time variant filter channel.
This document provides a quick introduction to communication systems, including:
1) It describes the basic components of a communication system including source encoding, transmission, reception, and decoding.
2) It contrasts analog and digital signals and modulation techniques.
3) It discusses performance metrics for analog and digital communication systems including fidelity, data rate, bit error rate, and signal-to-noise ratio.
High performance browser networking ch5,6Seung-Bum Lee
The document discusses the characteristics and performance limitations of wireless networks. It covers topics such as wireless network types and standards, factors that affect wireless throughput such as bandwidth and signal-to-noise ratio, and challenges such as interference from other networks and variable bandwidth. The key points are that wireless networks have limited and shared bandwidth, unpredictable latency, and throughput that varies based on environmental factors. Applications over wireless must be designed to adapt to these constraints.
AUDIO VOICE RECORDER AND TRANSMISSION THROUGH A WIRELESS MEDIUM BETWEEN PC AN...wadzani umaru
There is a fast growing need to support audio voice communication in wireless channel between a voice source and personal computer PC. In this paper we develop an algorithm using matlab software to indicate how a PC can receive audio voice signal from an audio source, record it and plot the resulting waveform on a graphical representation. The
actual data rate for audio voice transmission over IP is 64000bps, which was used as medium for audio voice communication between a PC and audio voice source
Unit 1 introduction to software defined radiosJAIGANESH SEKAR
The document discusses the introduction to software defined radios. It begins with defining software and radio individually, then explains how combining the two enables radios that are more flexible and cost-effective than traditional hardware radios. The ideal software defined radio architecture involves converting signals to the digital domain before performing all signal processing in software. This allows for easier upgrades and reconfiguration but poses technical challenges to implement. Potential benefits of software defined radios include greater flexibility, easier software reuse and testing, and lower costs for manufacturers, service providers and users.
This document provides an overview of data transmission and transmission media. It discusses topics such as transmission terminology, analog vs. digital signals, frequency domain concepts, transmission impairments, guided transmission media like twisted pair, coaxial cable and fiber optic cable, and wireless transmission media like terrestrial microwave and satellite transmission. The key topics covered in each transmission medium are also summarized.
In this presentation, production of digital audio is discussed. Also brief introduction about digital audio broadcast, recording techniques and stereo phony is given.
An audio quality evaluation of digital radio systemRojith Thomas
This document summarizes an evaluation of the audio quality of four digital radio systems: DAB, DAB+, HD Radio, and T-DMB. The evaluation used nine audio samples and tested each system at different bitrates. A group of listeners participated in two phases of subjective testing using the MUSHRA method. The results showed that certain bitrates for each system provided audio quality similar to or better than FM radio. Overall, the evaluation aimed to determine the optimal channel capacity needed to achieve a target audio quality for each digital radio system.
Practical Fundamentals of Voice over IP (VoIP) for Engineers and TechniciansLiving Online
This manual provides solid practical advice on application, implementation and, most importantly, troubleshooting Voice Over IP (VOIP) systems.
MORE INFORMATION: http://www.idc-online.com/content/practical-fundamentals-voice-over-ip-voip-21?id=151
This document summarizes a presentation on radio network planning for 3G networks. It discusses key concepts in radio network planning like cell configuration, interference management, frequency reuse, and mobile network evolution. It then covers the specific steps in 3G radio network planning, including dimensioning, nominal planning, simulation, and optimization. The document provides examples of link budget calculations and using planning software to simulate network performance and verify the design meets requirements.
Measuring Loudness Levels § When we measure loudness levels, we need to account for frequency sensitivity § This is done by applying a weighting filter to audio § For several yeas the A-weighting filter was commonly used § Other weighting curves (B and C for example) are also defined § Additionally measurement with multi channel audio need to take how we hear audio from different directional sources (i.e. surrounds) into account.
Loudness Management Strategies
§ “Measure and Set” § Measure content, set content with accurate metadata § “Measure and Scale” § Measure content, scale content to desired target level § “Target and Evaluate” § Select target loudness for submission – Specified in technical delivery specs § Evaluate content for compliance
This document provides an overview and details of a training course on wireless technology and wireless communication networks. The course covers topics such as transmission fundamentals, wireless network protocols including TCP/IP, spread spectrum technology, cellular wireless communications, and wireless network security. It also provides background information on wireless systems, personal area networks, wireless local area networks, and public wide-area cellular networks.
An audio quality evaluation of digital radio systemRojith Thomas
1) The document evaluates the audio quality of 4 digital radio systems (DAB, DAB+, HD Radio, T-DMB) at different bitrates using MUSHRA subjective testing methods.
2) Phase 1 results show the mean audio quality as a function of bitrate for each system, identifying optimal bitrates to achieve a target quality.
3) Phase 2 confirms Phase 1 consistency by comparing similar quality groups across systems.
4) The evaluation provides reference results on the audio quality and channel capacity needed to achieve various quality targets for digital radio systems.
TransferJet is a wireless technology that allows for high-speed file transfers between electronic devices through a simple touch. It has a transfer speed of 560 Mbps, much faster than Bluetooth or NFC. TransferJet uses ultra-wideband technology to transmit data over short ranges of a few centimeters. It supports common protocols like OBEX and SCSI and can be used to exchange files, access media, and enable print services between compatible devices. The TransferJet Consortium promotes adoption of the technology across various industries.
Comparisons of QoS in VoIP over WIMAX by Varying the Voice codes and Buffer sizeEditor IJCATR
Voice over Internet Protocol (VoIP) is developed for voice communications system based on voice packets transmitted over
IP network with real-time communications of voice across networks using the Internet protocols. Quality of Service (QoS) mechanism
is applied to guarantee successful voice packets transmitted over IP network with reduced delay or drop according to assigned priority
of voice packets. In this paper, the goal of simulation models is present to investigate the performance of VoIP codecs and buffer size
for improving quality of service (QoS) with the simulation results by using OPNET modeler version 14.5. The performance of the
proposed algorithm is analyzed and compared the quality of service for VoIP. The final simulated result shows that the VoIP service
performance best under G.729 voice encoder scheme and buffer size 256 Kb over WiMAX network.
The document discusses various topics related to wireless communication channels and networks. It provides details on wireline channels, fading effects, bit error rates for different mediums. It also summarizes key aspects of cellular systems, challenges in wireless communications, deployment of different generations of wireless networks, and traffic routing in wireless networks. The document is written by A.Sanyasi Rao and contains technical details on wireless communication concepts.
This document provides an overview of key considerations for setting up a wireless ISP (WISP). It discusses Tranzeo Wireless as a vendor, emphasizing their support, reliable products, and helping customers design cost-effective solutions. Several technical aspects are covered, such as choosing the right equipment, conducting site surveys, managing bandwidth, and ensuring reliable connections. The document stresses that every location has unique needs, and finding the right vendor is important to receiving proper guidance on planning and optimizing a WISP network.
DAB (Digital Audio Broadcasting) is a digital broadcasting system for radio that provides listeners with more choice, better sound quality, and more information than analog radio. It allows broadcasters to transmit many more stations using the same frequency, and listeners can receive between 30-50 stations in major cities. DAB delivers improved sound quality by locking onto the strongest signal and eliminating hiss, crackle, and fade. Digital radios also allow listeners to easily tune to stations by name, display text information from stations, and pause, rewind, and record live radio.
This document provides an overview of wireless networks and the IEEE 802.11 wireless LAN standards. It discusses how wireless LANs connect to wired networks through access points and allow mobility. The 802.11 standards including 802.11a, 802.11b, 802.11g, and 802.11e are summarized, outlining their data rates, frequencies, and other key aspects. Security features of 802.11 such as Wired Equivalent Privacy (WEP) are also summarized, noting vulnerabilities in the authentication and encryption methods.
Tại Diên Hồng, chúng tôi đang hướng tới Trung tâm dưỡng lão đáng tin cậy nhất cho Người cao tuổi, các nhà đầu tư, nhân viên và cộng đồng bằng cách cung cấp dịch vụ phù hợp và cá nhân hóa. Xây dựng Diên Hồng trở thành một nơi an dưỡng kiểu mẫu, nơi Người cao tuổi được sống như mình mong muốn. Các cụ được hỗ trợ trong sinh hoạt, vệ sinh cá nhân hàng ngày; được chăm lo y tế và sức khỏe; được khám, thăm hỏi ân cần và nhắc nhở uống thuốc định kỳ; được chia sẻ, tâm sự và vui vầy với các cụ cùng tuổi; được sống trong tập thể đồng cảm, thấu hiểu; được cập nhật kiến thức mới về y tế, xã hội, kỹ năng sống; được vui chơi và khỏe mạnh mỗi ngày… Đây là những gì mang lại ý nghĩa và giá trị cho Trung tâm dưỡng lão Diên Hồng.
Diên Hồng cung cấp một lối sống lành mạnh, an toàn, hoàn toàn thoải mái và thư giãn. Giúp cho Người cao tuổi được sống vui vẻ mỗi ngày là ưu tiên hàng đầu để đảm bảo các cụ được tận hưởng những gì trọn vẹn nhất. Chúng tôi tự hào mang đến những trải nghiệm thú vị và sinh động trong cuộc sống thường nhật.
Dokumen tersebut membahas tentang penyakit menular seksual, gejala, pencegahan, dan dampak kesehatan dan psikologis dari aborsi. Beberapa penyakit seperti HIV/AIDS tidak dapat disembuhkan sepenuhnya, sehingga pencegahan melalui kebersihan dan tidak berhubungan seks sebelum nikah sangat penting. Aborsi dapat memiliki dampak fisik dan psikologis yang serius bagi wanita.
This document provides an introduction and overview of digital communications. It outlines the key elements of a digital communication system including the information source, source encoder, channel encoder, digital modulator, communication channel, digital demodulator, channel decoder, and source decoder. It describes common communication channels such as wireline channels using twisted pair and coaxial cable, fiber optic channels, wireless electromagnetic channels for ground wave, sky wave and line of sight propagation, and underwater acoustic channels. It also discusses mathematical models for communication channels, including the additive noise channel, linear filter channel, and linear time variant filter channel.
This document provides a quick introduction to communication systems, including:
1) It describes the basic components of a communication system including source encoding, transmission, reception, and decoding.
2) It contrasts analog and digital signals and modulation techniques.
3) It discusses performance metrics for analog and digital communication systems including fidelity, data rate, bit error rate, and signal-to-noise ratio.
High performance browser networking ch5,6Seung-Bum Lee
The document discusses the characteristics and performance limitations of wireless networks. It covers topics such as wireless network types and standards, factors that affect wireless throughput such as bandwidth and signal-to-noise ratio, and challenges such as interference from other networks and variable bandwidth. The key points are that wireless networks have limited and shared bandwidth, unpredictable latency, and throughput that varies based on environmental factors. Applications over wireless must be designed to adapt to these constraints.
AUDIO VOICE RECORDER AND TRANSMISSION THROUGH A WIRELESS MEDIUM BETWEEN PC AN...wadzani umaru
There is a fast growing need to support audio voice communication in wireless channel between a voice source and personal computer PC. In this paper we develop an algorithm using matlab software to indicate how a PC can receive audio voice signal from an audio source, record it and plot the resulting waveform on a graphical representation. The
actual data rate for audio voice transmission over IP is 64000bps, which was used as medium for audio voice communication between a PC and audio voice source
Unit 1 introduction to software defined radiosJAIGANESH SEKAR
The document discusses the introduction to software defined radios. It begins with defining software and radio individually, then explains how combining the two enables radios that are more flexible and cost-effective than traditional hardware radios. The ideal software defined radio architecture involves converting signals to the digital domain before performing all signal processing in software. This allows for easier upgrades and reconfiguration but poses technical challenges to implement. Potential benefits of software defined radios include greater flexibility, easier software reuse and testing, and lower costs for manufacturers, service providers and users.
This document provides an overview of data transmission and transmission media. It discusses topics such as transmission terminology, analog vs. digital signals, frequency domain concepts, transmission impairments, guided transmission media like twisted pair, coaxial cable and fiber optic cable, and wireless transmission media like terrestrial microwave and satellite transmission. The key topics covered in each transmission medium are also summarized.
In this presentation, production of digital audio is discussed. Also brief introduction about digital audio broadcast, recording techniques and stereo phony is given.
An audio quality evaluation of digital radio systemRojith Thomas
This document summarizes an evaluation of the audio quality of four digital radio systems: DAB, DAB+, HD Radio, and T-DMB. The evaluation used nine audio samples and tested each system at different bitrates. A group of listeners participated in two phases of subjective testing using the MUSHRA method. The results showed that certain bitrates for each system provided audio quality similar to or better than FM radio. Overall, the evaluation aimed to determine the optimal channel capacity needed to achieve a target audio quality for each digital radio system.
Practical Fundamentals of Voice over IP (VoIP) for Engineers and TechniciansLiving Online
This manual provides solid practical advice on application, implementation and, most importantly, troubleshooting Voice Over IP (VOIP) systems.
MORE INFORMATION: http://www.idc-online.com/content/practical-fundamentals-voice-over-ip-voip-21?id=151
This document summarizes a presentation on radio network planning for 3G networks. It discusses key concepts in radio network planning like cell configuration, interference management, frequency reuse, and mobile network evolution. It then covers the specific steps in 3G radio network planning, including dimensioning, nominal planning, simulation, and optimization. The document provides examples of link budget calculations and using planning software to simulate network performance and verify the design meets requirements.
Measuring Loudness Levels § When we measure loudness levels, we need to account for frequency sensitivity § This is done by applying a weighting filter to audio § For several yeas the A-weighting filter was commonly used § Other weighting curves (B and C for example) are also defined § Additionally measurement with multi channel audio need to take how we hear audio from different directional sources (i.e. surrounds) into account.
Loudness Management Strategies
§ “Measure and Set” § Measure content, set content with accurate metadata § “Measure and Scale” § Measure content, scale content to desired target level § “Target and Evaluate” § Select target loudness for submission – Specified in technical delivery specs § Evaluate content for compliance
This document provides an overview and details of a training course on wireless technology and wireless communication networks. The course covers topics such as transmission fundamentals, wireless network protocols including TCP/IP, spread spectrum technology, cellular wireless communications, and wireless network security. It also provides background information on wireless systems, personal area networks, wireless local area networks, and public wide-area cellular networks.
An audio quality evaluation of digital radio systemRojith Thomas
1) The document evaluates the audio quality of 4 digital radio systems (DAB, DAB+, HD Radio, T-DMB) at different bitrates using MUSHRA subjective testing methods.
2) Phase 1 results show the mean audio quality as a function of bitrate for each system, identifying optimal bitrates to achieve a target quality.
3) Phase 2 confirms Phase 1 consistency by comparing similar quality groups across systems.
4) The evaluation provides reference results on the audio quality and channel capacity needed to achieve various quality targets for digital radio systems.
TransferJet is a wireless technology that allows for high-speed file transfers between electronic devices through a simple touch. It has a transfer speed of 560 Mbps, much faster than Bluetooth or NFC. TransferJet uses ultra-wideband technology to transmit data over short ranges of a few centimeters. It supports common protocols like OBEX and SCSI and can be used to exchange files, access media, and enable print services between compatible devices. The TransferJet Consortium promotes adoption of the technology across various industries.
Comparisons of QoS in VoIP over WIMAX by Varying the Voice codes and Buffer sizeEditor IJCATR
Voice over Internet Protocol (VoIP) is developed for voice communications system based on voice packets transmitted over
IP network with real-time communications of voice across networks using the Internet protocols. Quality of Service (QoS) mechanism
is applied to guarantee successful voice packets transmitted over IP network with reduced delay or drop according to assigned priority
of voice packets. In this paper, the goal of simulation models is present to investigate the performance of VoIP codecs and buffer size
for improving quality of service (QoS) with the simulation results by using OPNET modeler version 14.5. The performance of the
proposed algorithm is analyzed and compared the quality of service for VoIP. The final simulated result shows that the VoIP service
performance best under G.729 voice encoder scheme and buffer size 256 Kb over WiMAX network.
The document discusses various topics related to wireless communication channels and networks. It provides details on wireline channels, fading effects, bit error rates for different mediums. It also summarizes key aspects of cellular systems, challenges in wireless communications, deployment of different generations of wireless networks, and traffic routing in wireless networks. The document is written by A.Sanyasi Rao and contains technical details on wireless communication concepts.
This document provides an overview of key considerations for setting up a wireless ISP (WISP). It discusses Tranzeo Wireless as a vendor, emphasizing their support, reliable products, and helping customers design cost-effective solutions. Several technical aspects are covered, such as choosing the right equipment, conducting site surveys, managing bandwidth, and ensuring reliable connections. The document stresses that every location has unique needs, and finding the right vendor is important to receiving proper guidance on planning and optimizing a WISP network.
DAB (Digital Audio Broadcasting) is a digital broadcasting system for radio that provides listeners with more choice, better sound quality, and more information than analog radio. It allows broadcasters to transmit many more stations using the same frequency, and listeners can receive between 30-50 stations in major cities. DAB delivers improved sound quality by locking onto the strongest signal and eliminating hiss, crackle, and fade. Digital radios also allow listeners to easily tune to stations by name, display text information from stations, and pause, rewind, and record live radio.
This document provides an overview of wireless networks and the IEEE 802.11 wireless LAN standards. It discusses how wireless LANs connect to wired networks through access points and allow mobility. The 802.11 standards including 802.11a, 802.11b, 802.11g, and 802.11e are summarized, outlining their data rates, frequencies, and other key aspects. Security features of 802.11 such as Wired Equivalent Privacy (WEP) are also summarized, noting vulnerabilities in the authentication and encryption methods.
Tại Diên Hồng, chúng tôi đang hướng tới Trung tâm dưỡng lão đáng tin cậy nhất cho Người cao tuổi, các nhà đầu tư, nhân viên và cộng đồng bằng cách cung cấp dịch vụ phù hợp và cá nhân hóa. Xây dựng Diên Hồng trở thành một nơi an dưỡng kiểu mẫu, nơi Người cao tuổi được sống như mình mong muốn. Các cụ được hỗ trợ trong sinh hoạt, vệ sinh cá nhân hàng ngày; được chăm lo y tế và sức khỏe; được khám, thăm hỏi ân cần và nhắc nhở uống thuốc định kỳ; được chia sẻ, tâm sự và vui vầy với các cụ cùng tuổi; được sống trong tập thể đồng cảm, thấu hiểu; được cập nhật kiến thức mới về y tế, xã hội, kỹ năng sống; được vui chơi và khỏe mạnh mỗi ngày… Đây là những gì mang lại ý nghĩa và giá trị cho Trung tâm dưỡng lão Diên Hồng.
Diên Hồng cung cấp một lối sống lành mạnh, an toàn, hoàn toàn thoải mái và thư giãn. Giúp cho Người cao tuổi được sống vui vẻ mỗi ngày là ưu tiên hàng đầu để đảm bảo các cụ được tận hưởng những gì trọn vẹn nhất. Chúng tôi tự hào mang đến những trải nghiệm thú vị và sinh động trong cuộc sống thường nhật.
Dokumen tersebut membahas tentang penyakit menular seksual, gejala, pencegahan, dan dampak kesehatan dan psikologis dari aborsi. Beberapa penyakit seperti HIV/AIDS tidak dapat disembuhkan sepenuhnya, sehingga pencegahan melalui kebersihan dan tidak berhubungan seks sebelum nikah sangat penting. Aborsi dapat memiliki dampak fisik dan psikologis yang serius bagi wanita.
Beer vector mechanics for engineers statics 10th solutionsZahid Angah
This document contains solutions to problems involving determining the magnitude and direction of the resultant force of two or more applied forces using trigonometric methods like the law of sines and law of cosines. Various engineering scenarios are presented, like forces on structural members, cables supporting poles, and tanks being positioned. The solutions show setting up the appropriate trigonometric equations and solving for the unknown magnitudes and/or directions of forces based on given angle and force information.
The document discusses asynchronous and synchronous transmission. Asynchronous transmission is characterized by the sender and receiver not being synchronized in terms of information flow, but being synchronized for character timing. It can be used for low and high speed transmission such as modems and ATM. Synchronous transmission synchronizes the sender and receiver for both information flow and timing, requiring more resources. It is used for high speed links but asynchronous transmission is more widely used in practice due to advances allowing high speeds asynchronously.
1) The document provides an overview of analog and digital technology, their areas of application, and the process of analog to digital conversion.
2) Analog signals are defined by their amplitude, cycle, and frequency measured in Hertz. They can represent information but are difficult to manipulate. Analog to digital conversion is required for computer processing.
3) Digital technology uses binary digital signals and has advantages like exact reconstruction and faster speeds. It is used in computers, new telephone networks, and digital television. Digital to analog conversion is required to connect digital systems to analog networks.
This document provides an overview of several key topics related to analog and digital technologies:
1) It explains the basic concepts of analog and digital signals and technologies, and discusses the importance of frequency spectrum and bandwidth for communication.
2) It gives an overview of digital technologies and how data is digitized for processing and transmission. Key topics covered include digitization of data, audio, images and video.
3) It discusses interfaces between analog and digital technologies, and factors that influence quality retention when data is digitized and transmitted digitally.
The document provides an overview of key topics in wireless and mobile communication including fundamental communication terms, types of communication systems and channels, bandwidth, and the evolution of wireless technologies. It discusses models of wireless digital communication links and describes the basic functions of transmitters and receivers. The document also outlines tasks performed at the transmitter and receiver such as channel estimation, equalization, and modulation/demodulation.
These slides cover a topic on ISDN (Integrated Services Digital Network) in Data Communication. All the slides are explained in a very simple manner. It is useful for engineering students & also for the candidates who want to master data communication & computer networking.
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1fbciobmrrqmnlyjl1he-signature-a1b6820cbe628a2a167a0a81f2762fc8f340dd4b93d47a...Mathavan N
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Data transmission rates depend on three main factors: available bandwidth, the signal used, and noise levels. Bandwidth refers to the range of frequencies a channel can pass and is measured in Hertz, while transmission rate is measured in bits per second. Digital data uses discrete states represented by bits, while analog data is continuous. Common digital transmission systems include telephone lines, Ethernet, cable modems, DSL, wireless networks, and optical fiber, with rates ranging from kilobits per second to several gigabits per second. Analog transmission faithfully reproduces all signal details but quality degrades with each repeater, while digital only needs to reproduce discrete levels.
This document discusses the use of digital signal processing (DSP) for wireless and mobile communication. It provides examples of DSP applications such as speech coding, detection and filtering, diversity receivers, and error correction. DSP is beneficial for wireless systems because it provides flexibility, programmability, and can achieve the high performance needed for increasing data rates. DSP targets for applications include speech coding, image enhancement, and equalization in devices like cell phones and voice over IP.
The document discusses digital transmission and multiplexing techniques. It begins by defining digital transmission as the transmission of digital signals between two or more points in a communications system. It then describes several multiplexing techniques including time-division multiplexing (TDM), frequency-division multiplexing (FDM), and code-division multiplexing (CDM). The document also discusses the evolution of digital multiplexing standards from Plesiochronous Digital Hierarchy (PDH) to Synchronous Digital Hierarchy (SDH), noting that SDH provides a simpler, more economical, and flexible telecom infrastructure compared to PDH.
Certainly! Let's break down the discussion on data communication into several parts. For a comprehensive understanding, we'll cover the basics, protocols, networking, security, and emerging trends. Each part will provide a more in-depth exploration of the topic.
### Part 1: Basics of Data Communication
Data communication is the process of exchanging information between two or more devices through a transmission medium such as cables, optical fibers, or wireless channels. It involves the use of protocols and technologies to ensure the reliable and efficient transfer of data.
#### 1.1 Components of Data Communication
Data communication systems consist of several key components, including:
- **Sender/Transmitter:** Initiates the communication by converting data into a signal.
- **Receiver:** Accepts the signal and converts it back into usable data.
- **Transmission Medium:** The physical path through which data travels (e.g., cables, airwaves).
- **Protocol:** A set of rules governing the exchange of data between devices.
#### 1.2 Types of Data Transmission
- **Analog vs. Digital:** Understanding the fundamental difference between analog and digital signals.
- **Simplex, Half-Duplex, and Full-Duplex:** Exploring the various modes of data transmission.
#### 1.3 Modulation and Multiplexing
- **Modulation:** The process of encoding digital information onto analog signals.
- **Multiplexing:** Techniques for combining multiple signals into a single transmission medium.
### Part 2: Data Communication Protocols
Data communication relies on standardized protocols to facilitate seamless interaction between devices. These protocols dictate the rules for data formatting, error checking, and synchronization.
#### 2.1 TCP/IP Protocol Suite
- **Transmission Control Protocol (TCP) and Internet Protocol (IP):** Fundamental protocols of the internet.
- **UDP (User Datagram Protocol):** A connectionless protocol for faster data transmission.
#### 2.2 OSI Model
- **Open Systems Interconnection model:** A conceptual framework for understanding network interactions divided into seven layers.
#### 2.3 Wireless Communication Protocols
- **Wi-Fi, Bluetooth, and NFC:** Popular wireless communication protocols.
### Part 3: Networking in Data Communication
Networking is a crucial aspect of data communication, encompassing the design, implementation, and management of interconnected systems.
#### 3.1 Types of Networks
- **LANs (Local Area Networks) and WANs (Wide Area Networks):** Differences and use cases.
- **MANs (Metropolitan Area Networks) and PANs (Personal Area Networks):** Exploring network scales.
#### 3.2 Network Topologies
- **Star, Bus, Ring, Mesh, and Hybrid Topologies:** Understanding how devices are interconnected.
#### 3.3 Network Devices
- **Routers, Switches, Hubs, and Modems:** Roles and functionalities in a network.
### Part 4: Security in Data Communication
As data communication becomes more prevalent, ensuring the security and
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MMC 1 module ppt.pdf program to set up a given number of two program to set u...Prajwalgh
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3. Chapter Objectives
• Explain the basic concepts of analog and
digital technology
• Show the importance of frequency spectrum
to communication along with an explanation
of the concept of bandwidth
• Give an overview of the interface technology
between analog and digital technology
• Describe the process of digitizing data,
audio, image and video
• Discuss quality retention in digital
transmission
5. Areas of Application
• Old telephone networks
•Most television broadcasting at present
• Radio broadcasting
6. Analog Signals: The Basics
Cycle
Time
Signal
Amplitude
Frequency =
Cycles/Second
A typical
sine wave
7. Amplitude and Cycle
• Amplitude
– Distance above reference line
• Cycle
– One complete wave
8. Frequency
• Frequency
– Cycles per second
– Hertz is the unit used for expressing
frequency
• Frequency spectrum
– Defines the bandwidth for different analog
communication technologies
9. Information Representation
Using Analog Signals
• Information can be represented using
analog signals
• Analog signals cannot be manipulated
easily
• Analog signals must be digitized for
computer processing
– They must also be presented in binary
form for computer processing
10. Analog to Digital Conversion
1 0 1 1 0 1 0 0
A to D Converters, Digital
Signal Processors (DSP) etc.
11. Data Transmission Using Analog
Technology
Computer Modem
Digital
0s and 1s
Analog
0s and 1s
Digital-to-Analog Modulation
and vice versa
15. Frequency Spectrum Defined
• Available range of frequencies for
communication
• Starts from low frequency communication
such as voice and progresses to high
frequency communication such as satellite
communication
• The spectrum spans the entire bandwidth of
communicable frequencies
16. Frequency Spectrum
Low Frequency High Frequency
Radio
Frequency
Coaxial
Cable
MHz
Satellite
Transmission
Microwave
MHz
Voice
KHz
17. Frequency Spectrum
• Low-end
– Voice band
• Middle
– Microwave
• High-end
– Satellite communication
18. Signal Propagation
• Low frequency
– Omni-directional
• High frequency (In general)
– Unidirectional
19. Bandwidth Definition
• Bandwidth, in general, represents a
range of frequencies
Bandwidth is 400 MHz
300 MHz 700 MHz
20. Usage of the Term Bandwidth
• To specify the communication capacity
– A medium such as a coaxial cable is
associated with a bandwidth
• To indicate the bandwidth of a
technology
– Voice grade circuits have a bandwidth of 4
KHz (0-4000 Hz)
21. Digitization Consideration
• Sample at twice the rate of bandwidth
for acceptable quality digitization of
voice
– Sampling rate for voice transmission is
there 8000 Hz
• If each sample is represented by 8-bits,
the bandwidth required for
transmission is 64000 bps –
Approximately 64K bps
22. Communication Capacity
• Bandwidth is indicative of the
communication capacity
• Communication speed is proportional
to bandwidth
– Shannon's law
• Units used to represent bandwidth are
Hz, bps etc.
23. Coaxial Cable Example
• Bandwidth of 300 MHz
• Comparison with twisted pair
– Higher bandwidth
– Supports faster communication speeds
24. Limiting Factors on
Communication Speed
Communicatio
Bandwidth n Speed Technology
25. Impact of bandwidth and Technology
on Communication Speed
• Bandwidth limitation
– Use better technology such as data
compression used in modems to increase
speed of communication
• Bandwidth and technology limitation
– Move to higher bandwidth media such as
fiber cables
26. Speed Dependency on Bandwidth
and Technology
Higher Bandwidth
Medium 1
Technology Medium 2
Medium 1 example can be shielded twisted
pair and medium 2 example can be fiber.
27. Implication
•Whenever a new technology with
higher communication speed is
introduced, it is first introduced on a
medium of higher bandwidth
– Example: Optical fiber
• It is then moved to a widely used
medium with further advancement of
the technology
– Example: Copper wire
30. Areas of Application
• Computers
• New telephone networks
• Phased introduction of digital television
technology
31. Digital Technology
• Basics
– Digital signals that could be assigned
digital values
• Digital computer technology
– Digital signals
– Binary representation
•Encoded into ones and zeros
32. Digital Advantage
• Processing using computer technology
• Programmable services
• Better quality due to being able to
reconstruct exact digital patterns at the
receiving end
• Faster communication speeds are
possible
33. Digital Signal
1 0 1 1 0 1 0 0
Pulse
Time
Signal Strength
Pulse Duration
34. Digital Terms
• Pulse
• Pulse duration
• Pulse amplitude
• Signal strength
36. Clock Speed and
Execution Speed
• Pulse duration is inversely proportional
to the clock frequency
• Faster the clock speed, the smaller the
pulse duration
• Smaller the pulse duration, the faster
the execution in general
37. Clock Speed and Communication
Speed
• Faster the clock speed, smaller the pulse
duration
• Smaller the pulse duration, smaller the
time taken to transmit one bit of
information
• Therefore, faster the clock speed
measured in MHz, faster the
communication speed measured in
Mbps in general
38. Clock Speed and Computer
Operation
• Computer operations are timed by a clock,
namely by the clock speed measured in HZ
• Faster the speed, the smaller the pulse
duration
• Computer operations are timed by the pulse
duration
• Therefore, faster the clock speed, faster the
computer operation
– A 3 GHz computer is faster than a 2 GHz
computer
41. The Need for Conversion
• Analog-to-Digital Conversation
– Connection of a computer to an analog
communication line
• Digital-to-Digital Interface
– Connection of a computer to a digital ISDN
line
– Connection of different networks using a
router
42. Digital-to-Analog Interface
Comp.
Sys. 1
Comp.
POTS
Modem Modem Sys. 2
Digital
Serial
RS-232C
Digital
Serial
RS-232C
Analog
ITU V.90
45. Digital to Digital Interface
• In general, in digital to digital interface,
protocol conversion takes place
– Example: Connecting an Ethernet network
to a campus backbone network using a
router
51. The Advantages of Digitization
• Information can be processed by the
computer
• Easy transmission of information over
the Internet and other computer
networks
•Minimize loss of quality during
transmission
54. The Basis
• Alphanumeric data is digitized using
well established coding systems
55. Codes Used in the Digitization
Of Data
• Coding Standards
– ASCII
– EBCDIC
– Unicode
• ASCII Code example
– A=1000001
56. The Unicode
• Replaced the ASCII coding system in
microcomputers
• All variations of the Latin language
– English
– European languages
• Chinese and Japanese
• 18 Major languages
– Eg: Tamil
57. Unicode Possibilities
• It is a 16-bit code as opposed to the
ASCII code that is basically an 8-bit
code
• It is therefore possible to have 65,536
variations in UNICODE
58. Communication With ASCII
And EBCDIC
• Latin languages can be transmitted in
coded form
• Other languages
– Bit-mapped image transmission
– Requires considerably more bandwidth
– An exception is the use of true-type fonts
to display the characters of a language not
supported by ASCII
59. Communication With Unicode
• Binary encoded transmission
– Latin languages
– 18 major languages
– Chinese, Japanese etc.
• Transmission itself requires less
bandwidth
• Universal usability of software in all the
supported languages
60. Unicode Advantage in WWW
Transmissions
Tamil pages are transmitted in their binary encoded form.
Client
Tamil
Web
Site
Internet Explorer
Browser retrieving
Tamil pages on a client
supporting Unicode.
Site created using all
the tools such as the
MS-IIS.
61. Transmission of Tamil Pages as
Images on WWW
Client
Tamil
Web
Site
Internet Explorer
Browser retrieving Tamil
pages similar to images.
Binary image
transmission of
Tamil pages.
Web pages scanned and
stored as images.
62. Using Downloaded Fonts to Host
and Transmit Tamil Pages
Client
Tamil
Web
Site
Internet Explorer
retrieving Tamil
pages.
requirements are low.
Site created
with tools
such as MS-IIS.
Download and install
the Tamil fonts.
Bandwidth
Binary encoded form.
63. Foreign Language Web Page
Options
• Store the page as an image
• Use a font for the language, if available
• Use Unicode to develop the web page
64. UNICODE Usage
• Currently all the computers support
UNICODE
• Also, the operating systems and the
applications also support UNICODE
• Both hardware and software support is
necessary for the successful
implementation of UNICODE
67. Digitization Of Audio: Overview
• Take samples of audio at pre-determined
time intervals known as the
sampling rate
• Represent the sampled audio with
digital signals
– Pulse Amplitude Modulation (PAM)
• Encode signals into binary code
– Pulse Code Modulation (PCM) that
incorporates PAM as well
– Required for computer processing
68. Digitization of Audio: Pulse
Amplitude Modulation (PAM)
Audio
9 8 7 6 7 9
Digital Signals must
further be encoded
into binary signals
for computer
processing and
transmission.
Sampling Interval
69. Digitization and Encoding of Audio:
Pulse Code Modulation (PCM)
• PCM is a two step process
• First the audio is sampled and
represented by digital signals
• The digital signals are then encoded in
binary form
70. Binary Encoding of Signals in
Pulse Code Modulation (PCM)
9 8 7 6 5 6
1001 1000 0111 0110 0101 0110
The integer numbers have effectively been
coded into zeros and ones. The ones and zeros
now contain the audio information encoded in
a form that could be processed by a computer.
PCM
71. Salient Points on the
Digitization Of Audio
• Sampling rate and the number of bits
used for representing the samples will
determine the quality of the audio
• Quality is retained in transmission
because only codes are transmitted
• Audio can be recreated to the original
quality by extracting the pattern from
the digital code
72. Sampling Factors
• Sampling interval determined by
sampling frequency
– Measured in Hz
• Sampling depth
– Measured in bits
• Sampling channels
– Mono or stereo, for example
76. Factors Affecting Quality
Number of bits
used for binary
encoding.
Example: 4 bits
allow 16
amplitude
variations to be
represented.
9 8 7 6 7 9
Sampling Interval
77. Effect of Sampling Frequency
• Higher sampling frequency
– Smaller sampling intervals
– Frequent sampling
– Better quality because the audio pattern is
captured better
– Higher bandwidth required for
transmission
– Higher disk space required for storage
78. Computation of Bandwidth
Requirement for Transmission
• Problem:
– Compute the audio streaming rate for a
voice grade circuit given that the number
of bits used in the sampling is 8
• Background information
– A voice grade circuit has a bandwidth of
approximately 4000 Hz
• General rule
– For acceptable quality, the audio must be
sampled at twice the frequency of the voice
grade bandwidth
79. Reason for Sampling at Twice the
Frequency
• Two peaks in each cycle
– Half of a cycle is above the datum line
– The other half of the cycle is below the
datum line
• Therefore, sample the audio at twice the
frequency rate
80. CD Sampling?
• Sampling in this case is done for higher
quality
– 44 KHz
– 16-bits
– Stereo
81. Problem Representation
79 68 57 46 57 79
8 bits are used enabling
256 amplitudes to
represent the human
voice which is considered
to be adequate.
1/8000 Seconds (8000 HZ twice the frequency of the voice
grade circuit)
or 2X4000 samples per second
82. Bandwidth Computation for Voice
• Number of samples
– 8000 per second
• Number of bits per sample
– 8
• Bandwidth requirement
– 8X8000 bps = 64,000 bps
– Approximately 64K bps
• 64K bps is the speed of a single ISDN
(B) channel designed to carry voice
83. Bandwidth of Voice Circuits
• Generally speaking, the bandwidth
requirement for uncompressed voice
circuit is 64 Kbps
• An example is the ISDN – B channel
that was originally intended to carry
voice
– Its bandwidth is 64 K bps
86. Recording Used in this Example
• Settings for recording
– 11K Hz, 8 bit and mono
• Audio bandwidth requirement is 88K
bps
• Streaming is required to send the audio
alone over the Internet
• Approximate bandwidth required for
both video and audio is 133K bps
87. Audio Transmission In WWW
Audio streaming requires compression.
Web 28-56K bps
Site
Client
Receive audio using
Internet Explorer
and a plug-in to receive
the audio stream.
Real-time audio
broadcast support
using streaming
server module.
88. Delivery of Instruction Over the
WWW
Client
Web
Site
Audio/Video streaming.
Receive audio/video using
Internet Explorer and Media
Player.
Store streamed audio/
video using Windows Media.
28-56K bps
90. Internet Ramp Bandwidth
Computation
A T1 line operating at approximately 1.354M bps
can support approximately 10 connections in theory.
WWW
In practice, 7 connections which is 70 percent of 10
connections can be supported with due consideration
given to
bandwidth bottlenecks.
92. Sampling Considerations In
Communications
Digital audio transmission
Sender Receiver
Adjust quality (sampling interval and bit
representation) to suit bandwidth availability.
93. Audio Files
• Audio can be stored in different formats
– Uncompressed or raw file format (wav)
– Compressed format
– Streaming format
•Streamed audio is also compressed
•It is also designed for real-time delivery of
audio
94. Audio File Format
• wav file format
– Basic file format in audio storage or raw file
• rm file format
– Real audio’s streamed file format
– Streamed file
• wma file format
– Microsoft’s audio streamed file format
– Streamed file
• mp3 file format
– Compressed file
• aac file format
–
97. Quality Retention
• Quality is retained in digital
transmission because only the codes are
transmitted
• Quality is subject to some deterioration
in analog transmission because the
wave pattern is transmitted
98. Analog Audio Transmission
Audio Prior
to Transmission
Audio with
Interference
Transmission
Audio After Filtering
99. Passage of Analog Audio Over
Analog Lines
Analog
Audio
Analog
Signals
Analog
Signals
Analog
Audio
Telephone
Telephone
100. Recreation of Audio from Analog
Signals
• A difficult task
• Complex algorithms are used to filter
noise etc. for better audio transmission
101. Signal Passage in Digital Audio
Transmission
Encode
Recreate Transmit
Audio
Decode
Audio
102. A Sample Digital Audio
Transmission Path
Analog
Audio
Digital
Audio
DSL
Modem
DSL
Modem
Digital
Audio
Analog
Audio
Sound
Card
Sound
Card
Digital
Network
103. Sound Generation
• Sound is recreated at destination
– Using FM synthesis
– Using wave table generation
• Noise is not an issue in digital
communication although it is an issue
in digital transmission
– The reason, once again, is due to the fact
that only codes are transmitted in digital
transmission
104. Better Sound Generation
•Wave table generation provides better
sound reproduction that FM synthesis
105. Digital Advantage in Audio
Transmission
• Only codes are transmitted
• Original encoding is recreated
• Original audio is reproduced
• Again, sampling rate and number of
bits used in each sample will determine
the quality of audio transmitted
107. Sample Digital Audio Transmission
Path Over Analog Lines
Analog
Audio
Digital
Audio
Modem
Modem
Digital
Audio
Analog
Audio
Sound
Card
Sound
Card
Analog
PSN
108. Audio Transmission In WWW
Audio stream over analog/digital line.
Client
Web
Site
Receive audio using
Internet Explorer
and Windows Media Player.
Real-time audio
broadcast support
using Windows Media
streaming server module.
109. Analog to Digital Converter
• A to D and D to A converter
• The chip that is responsible for this
conversion is known as the DSP (Digital
Signal Processor) chip
• It is used in sound cards, modems etc.
wherever there is a need for A to D and D to
A conversion
• The mass use of this chip in various devices
has led to a drastic drop in the price of the
chip and the devices
113. Image Digitization
• Image can be of the form black and
white, gray scales, color
• Factors that influence the digitization of
image are as follows
– Resolution measured in pixels
– Color depth expressed in number of color
variations
115. Digitization of the Letter L
Number of bits
determine the
amount of
information that
could
be stored.
116. Digitization Of Image: The
Process
• Divide the image into a grid of pixels
that may be considered as the sampling
points of the image
• Digitize information on each pixel
• Store and transmit
117. Resolution
• Horizontal resolution
– Number of horizontal pixels
• Vertical resolution
– Number of vertical pixels
• Image resolution
– Horizontal by vertical resolution
– Ex: 640 by 480
118. Digitization of Black and White
Image
• White
– A pixel lit represents a 1
• Black
– A pixel not lit represents a 0
• Storage required per pixel
– 1 bit
• Storage required for 640 by 480
resolution image
– 640 times 480 bits = 307,200 bits = 38.4K
Bytes
119. Digitization of Image Using
Gray Scales
• A pixel may take a value between 0 and
15 for 16 gray scales
• A gray scale of 3 can be coded as 0011
and the others similarly using this 4
digit code
• The bandwidth requirement for the
transmission of a 640X480 image in this
case is as follows:
– 640X480X4 = 153.5K Bytes
120. Digitization of Color Image
• Image coding
– Each pixel may take a value between 0 and 255 if
256 colors are to be represented
• Storage requirement
– Digitizing of images requires substantial number
of bytes and hence large storage space for
processing
• Bandwidth requirement
– Higher bandwidths are required to transmit color
images
121. Bandwidth Computation for
Image with 256 Colors
• Resolution is 640X480
• 8 bits are required to represent 256
colors
• bandwidth requirement for the
transmission of one image is as follows:
– 640X480X8 = 307.2K Bytes
122. The Effect of Color Depth and
Resolution
• Compare VGA, SVGA and XGA
– XGA provides the highest resolution
• Practical implication
– More colors less resolution if bandwidth or
storage is the limiting concern
– Example
• 256 colors at lower resolution
• 16 colors at higher resolution
• Rule
– Higher the resolution the lower the number of
colors available in general given the resource
constraints such as bandwidth constraints
123. Factors Affecting Bandwidth
Requirement in Image Transmission
• The higher the resolution, the higher the
bandwidth requirement for transmission
• The higher the color representation, also
known as color depth, higher the bandwidth
requirement
• For true color, 24 (32) bits are required to
represent each pixel
• The file sizes in raw image capture can thus
become very large
126. Compression of Digitized Images
• Compression is required to reduce the
size of the image file
• Large blocks of unchanged data in an
image (background) offers an
opportunity to compress the image
• Image files are almost always
compressed
127. A Few Compression Formats
• GIF
• JPEG
•MIC (Microsoft Image Composer)
• PCD (KODAK) - Used by Corel
• Uncompressed file exist in the form of
bit mapped file with the extension of
.BMP
128. Image File Format Extensions
• File formats often represent the compression
procedure being used such as jpg
representing the jpeg compression technique
• Examples:
– Bmp – uncompressed file format
– Gif
– jpg
– pcd
– tiff
– pcx
129. Loss-less Compression and
Others
• Some compression formats offer loss-free
compression of the image
• Others sacrifice minimal loss for the
sake of reduced storage and bandwidth
requirements
• Fortunately, the loss is not easily
detected by the naked eye
130. Image Transmission
Considerations
Adjust image to suit available bandwidth.
Sender Receiver
Adjustable features are as follows.
- Resolution
- Color depth
Adjusting the size also reduces the bandwidth
requirement because of a corresponding reduction
in the number of pixels required to represent
the image.
131. A Peek At Data Compression
• 0 0 0 0 0 0 0 0 0 0 0 - - - - - -0 1 1 1 1 1 11
…... 0
• THE ABOVE CAN BE COMPRESSED
INTO = #9000$0#
– 9000 bits are compressed into 8 characters
that #600$require 1#
approximately 64 bits for
transmission
– 9000 ZEROS ARE CODED INTO #900$0#
INTERPRET WITHIN THE # SIGN
600
NUMBER COUNT
1
CHARACTER BEING
TRANSMITTED
132. Compression Result
• In the previous example, 9000 bits are
compressed into 8 characters
• If 10 bits are used on the average for
transmitting each character, the 9000
bits of information is now compressed
into 80 bits for transmission
133. Modem Implication in Image
Transmission
• Modems also compress the data stream to
achieve higher transmission speeds
• Because of the fact that the images are already
compressed, the full speed benefit may not be
realized when images are transmitted over a
modem connection
• An already compressed image file does not,
for instance, offer itself well to further
compression in the modem
136. Digitization of Video
• Digitization of video is an extension of
the process of digitizing an image
• It amounts to the transmission of
certain number of still images known as
frames per second
• Obviously, digitized video requires
higher bandwidth for transmission and
more space for storage
137. Frame Rate
• 30 frames of images per second, in general,
defines continuos motion
• In communications, 25 frames per second is
considered to be continuous motion
• 15 frames per second is currently used in
video conferencing over digital lines for
acceptable reception of video
• It is also possible to engage in video
conferencing at a frame rate of 5 frames per
second
138. Computation of Bandwidth for
Raw Transmission of Video
• Image resolution is 640X480
• Number of colors is 256 (8 bit)
• Acceptable reception requires 15 frames
per second
• Therefore, the bandwidth for the raw
transmission is as follows:
– 640X480X8X15 = 36.86M bps = 4.6M Bps
139. Compression Standards Used in
the Digitization of Video
• MPEG 1, MPEG 2, MPEG 3 and MPEG 4
• Windows Media Video
• Real Media
• Indio
• QuickTime
• ActiveMovie
• AVI
140. Streaming Formats for Video
• Various streaming formats are
supported by different vendors
– RealVideo
•Microsoft’s streaming format
– wma (Windows Media Audio)
– wmv (Windows Media Video)
– Active Streaming Format (ASF)
• Apple’s QuickTime format
• Etc.
141. Overview of Video Transmission
in Video Conferencing
• Minimum speed
– 3 to 5 frames per second
• Acceptable speed
– 15 frames per second
• Transmission techniques
– Data is compressed
– Only changes to the frame are transmitted
142. Bandwidth Optimization in
Video Conferencing
• Minimize Windows for maximum
efficiency
– Transmit less number of pixels in
minimized form
• Decrease the resolution
– Has the same effect as above
• Decrease the number of colors
displayed
143. Communication Links for Video
Conferencing
• Possible on analog lines using 56,000
bps transmission speed but not
desirable
• Digital lines are preferred and the
guidelines are as follows:
– Possible at 128k bps using ISDN lines
– Acceptable at 384k bps
– 1M bps and above offer good quality video
transmission
144. ISDN Line Suitability
• ISDN B channels can be assigned on a
dynamic basis depending on the
bandwidth requirement at any point in
time during video conferencing