Transmission signals

• Analog voice data must be translated into a series of binary digits before they can be transmitted in digital transmission system. One means of doing this is called pulse amplitude modulation (PAM). • The process of converting analog signal to digital is also known as A_to_D conversion or A/D conversion. The circuit does the conversion known as A/D converter. In analog modulation (continuous wave modulation), some parameter of a sinusoidal carrier wave is varied continuously in accordance with the message signal. ...
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Signals represent information about data, voice, audio, image, video… There are many ways to classify signals but here we categorize signals as either analog (continuoustime) or digital (discretetime). Signal processing is to use circuits and systems (hardware and software) to act on input signal to give output signal which differs from the input, the way we would like to.
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A bit (binary digit) is the smallest unit of information • N = 2n where N is the number of representations and n is the number of bits (ex. ASCII, Unicode, PCM code etc.) • Data communications transfer information using codes that are transmitted as signals (either analog or digital) • In general, analog lines provide a slow service that contains high error rates.
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Transmission Basics In data networking, transmit means to issue signals to the network medium Transmission refers to either the process of transmitting or the progress of signals after they have been transmitted
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Guided  wire Unguided  wireless Characteristics and quality determined by medium and signal For guided, the medium is more important For unguided, the bandwidth produced by the antenna is more important Key concerns are data rate and distance
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In this section, we see how we can represent digital data by using digital signals. The conversion involves three techniques: line coding, block coding, and scrambling. Line coding is always needed; block coding and scrambling may or may not be needed.
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Digitaltoanalog conversion is the process of changing one of the characteristics of an analog signal based on the information in digital data.
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Transmission: the propagation of a signal, message, or other form of intelligence by any means such as optical fiber, wire, or visual means. Switching: selects the route to the desired destination that the transmitted signal travels by the closing of switches in either the space domain or the time domain or some combinations of the two.
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Telephone networks use circuit switching. The telephone network had its beginnings in the late 1800s. The entire network, which is referred to as the plain old telephone system (POTS), was originally an analog system using analog signals to transmit voice.
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The content in chapter 5 explain basic data transmission concepts, including full duplexing, attenuation, latency, and noise; describe the physical characteristics of coaxial cable, STP, UTP, and fiberoptic media; compare the benefits and limitations of different networking media;...
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Digital Modulation Techniques There are three ways in which the bandwidth of the channel carrier may be altered simply. It is worth emphasizing that these methods are chosen because they are practically simple, not because they are theoretically desirable. These are the altering of the amplitude, frequency and phase of the carrier sine wave. These techniques give rise to amplitudeshiftkeying (ASK), frequencyshiftkeying (FSK) and phaseshiftkeying (PSK), respectively. ASK describes the technique the carrier wave is multiplied by the digital signal f(t)....
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Automatic process control is concerned with maintaining process variables, temperatures, pressures, flows, compositions, and the like, at a desired operating value. As we shall see in the ensuing pages, processes are dynamic in nature. Changes are always occurring, and if actions are not taken, the important process variables— those related to safety, product quality, and production rates—will not achieve design conditions.
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Topics in Digital Communications Digital communication system advantages and disadvantages Digital communication system classification Digitization of analog signals Digital transmission systems Data communication systems Integrated Services Digital Network and other advanced digital communication systems.
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Frequency analysis of digital signals and systems was discussed in Chapter 4. To perform frequency analysis on a discretetime signal, we converted the timedomain sequence into the frequencydomain representation using the ztransform, the discretetime Fourier transform (DTFT), or the discrete Fourier transform (DFT). The widespread application of the DFT to spectral analysis, fast convolution, and data transmission is due to the development of the fast Fourier transform (FFT) algorithm for its computation....
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This is an undergraduate course in digital communications, which is designed to prepare students for engineering work in hightech industries and for graduate work in communications, signal processing, and computer systems. The course covers basic concepts and useful tools for design and performance analysis of transmitters and receivers in the physical layer of a communication system. Prerequisite: An introductory course in probability. A course in signals and systems. Texts: J.G. Proakis, M. Salehi, Communication Systems Engineering M. P. Fitz, A Course in Communication Theory Graders:...
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Many engineers familiar with analog television broadcast systems are now faced with designing, operating, and maintaining digital television systems. A major reason for this introductory book is to make the transition from analog to digital television broadcasting as painless as possible for these engineers. The emphasis is on radiofrequency (RF) transmission, those elements of the system concernedwith transmitting and propagating the digitally modulated signal.
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Spectrum of an FSK Signal : FSK involves frequency shifting a carrier between known fixed frequencies to convey digital data. Normally, FSK modulation is achieved using just two frequencies to represent binary data. For example, a frequency of 2000 Hz may represent a binary 1 (mark) and 1000 Hz a binary 0 (space). The energy of the signal alternates between the mark and space frequencies to convey the digital message. FSK describes the modulation of a carrier (or two carriers) by using a different frequency for a 1 or 0. The resultant modulated signal may be regarded as the sum...
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Fast Fourier Transform and Its Applications Frequency analysis of digital signals and systems was discussed in Chapter 4. To perform frequency analysis on a discretetime signal, we converted the timedomain sequence into the frequencydomain representation using the ztransform, the discretetime Fourier transform (DTFT), or the discrete Fourier transform (DFT). The widespread application of the DFT to spectral analysis, fast convolution, and data transmission is due to the development of the fast Fourier transform (FFT) algorithm for its computation.
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The scanning format of a video signal is a major determinant of general picture quality. Specifically, it determines such aspects as stationary and dynamic resolution, motion portrayal, aliasing, scanning structure visibility, and flicker. Various formats have been designed and standardized to strike a particular balance between quality, cost, transmission capacity, and compatibility with other standards.
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