The document discusses data transmission concepts and terminology. It explains that data transmission occurs between a transmitter and receiver over a transmission medium, using electromagnetic signals. Signals can be either analog or digital. Digital signals represent data using discrete voltage levels to represent bits, while analog signals have continuously varying voltage levels. The document discusses common transmission impairments like attenuation, delay distortion, and noise that can corrupt signals during transmission. It also introduces the concepts of channel capacity and the Nyquist formula, which states that the maximum data rate for a noise-free channel with bandwidth B is 2B bits per second.
This document provides a summary of key concepts in data communication and transmission including:
1) Communication models including simplex, half duplex, and full duplex transmission modes.
2) Analog and digital signals and their characteristics such as periodicity.
3) Concepts such as bandwidth, attenuation, noise, and Shannon's channel capacity formula that influence data transmission rates.
Analog signals are continuous waves that vary smoothly over time and can have an infinite number of values, while digital signals are discrete and can have only a limited set of values, such as 1 and 0. Analog signals are typically represented by sine waves, while digital signals are represented by square waves. While analog signals are best for audio and video transmission, digital signals are better suited for digital data transmission and provide benefits such as easier compression, encryption, and error detection.
This document provides an overview of digital communications and data transmission. It discusses key concepts such as analog to digital conversion (A/D), source coding, channel encoding, and modulation techniques.
The document begins with defining communication as the reliable transfer of data such as voice, video or codes from one point to another. It then outlines the basic components of a communication system including the information source, transmitter, channel, receiver and information sink.
It further explains the processes of analog to digital conversion including sampling, quantization and coding. It discusses how source coding aims to represent transmitted data more efficiently by removing redundant information. Finally, it provides an introduction to channel encoding which aims to control noise and detect/correct errors, as
This document discusses concepts related to data transmission including terminology, transmission media, signal types, bandwidth, impairments and more. It defines terms like simplex, duplex, guided vs unguided media, analog vs digital signals. It describes properties of periodic signals like sine waves and discusses how signals can be represented in both the time and frequency domains. It also summarizes common transmission impairments like attenuation, delay distortion and noise.
The document introduces some key concepts in data communication, including:
1) Different types of transmission media such as guided (e.g. fiber optic cable) and unguided (e.g. wireless).
2) Analog and digital signals and how analog data can be transmitted using either type of signal.
3) Factors that can impair transmission such as attenuation, delay distortion, and different types of noise. The Nyquist bandwidth and Shannon capacity formulas for calculating maximum data rates are also covered.
The Nyquist formula states that the maximum data rate supported by a bandwidth B is 2B bits per second. Doubling the bandwidth doubles the maximum data rate. Signals with more than two levels can represent more data per signal, with the formula becoming C = 2B log2M, where M is the number of signal levels. Shannon's channel capacity theorem defines the maximum reliable transmission rate C for a bandwidth B channel as C = B log2(1 + S/N), where S is the signal power and N is the noise power.
This document provides a summary of key concepts in data communication and transmission including:
1) Communication models including simplex, half duplex, and full duplex transmission modes.
2) Analog and digital signals and their characteristics such as periodicity.
3) Concepts such as bandwidth, attenuation, noise, and Shannon's channel capacity formula that influence data transmission rates.
Analog signals are continuous waves that vary smoothly over time and can have an infinite number of values, while digital signals are discrete and can have only a limited set of values, such as 1 and 0. Analog signals are typically represented by sine waves, while digital signals are represented by square waves. While analog signals are best for audio and video transmission, digital signals are better suited for digital data transmission and provide benefits such as easier compression, encryption, and error detection.
This document provides an overview of digital communications and data transmission. It discusses key concepts such as analog to digital conversion (A/D), source coding, channel encoding, and modulation techniques.
The document begins with defining communication as the reliable transfer of data such as voice, video or codes from one point to another. It then outlines the basic components of a communication system including the information source, transmitter, channel, receiver and information sink.
It further explains the processes of analog to digital conversion including sampling, quantization and coding. It discusses how source coding aims to represent transmitted data more efficiently by removing redundant information. Finally, it provides an introduction to channel encoding which aims to control noise and detect/correct errors, as
This document discusses concepts related to data transmission including terminology, transmission media, signal types, bandwidth, impairments and more. It defines terms like simplex, duplex, guided vs unguided media, analog vs digital signals. It describes properties of periodic signals like sine waves and discusses how signals can be represented in both the time and frequency domains. It also summarizes common transmission impairments like attenuation, delay distortion and noise.
The document introduces some key concepts in data communication, including:
1) Different types of transmission media such as guided (e.g. fiber optic cable) and unguided (e.g. wireless).
2) Analog and digital signals and how analog data can be transmitted using either type of signal.
3) Factors that can impair transmission such as attenuation, delay distortion, and different types of noise. The Nyquist bandwidth and Shannon capacity formulas for calculating maximum data rates are also covered.
The Nyquist formula states that the maximum data rate supported by a bandwidth B is 2B bits per second. Doubling the bandwidth doubles the maximum data rate. Signals with more than two levels can represent more data per signal, with the formula becoming C = 2B log2M, where M is the number of signal levels. Shannon's channel capacity theorem defines the maximum reliable transmission rate C for a bandwidth B channel as C = B log2(1 + S/N), where S is the signal power and N is the noise power.
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 concepts related to electromagnetic signals and digital data transmission. It covers topics such as:
- Analog vs. digital signals and how they are represented over time.
- Key parameters of signals like amplitude, frequency, period, and phase.
- Relationships between bandwidth, data rate, and channel capacity for digital transmission.
- Different transmission media like guided (copper, fiber) and unguided (wireless) and their frequency ranges.
- Multiplexing techniques like frequency-division and time-division that allow multiple signals to be transmitted over a single medium.
The document describes information and energy control systems. It discusses block diagrams of typical information systems like audio and process monitoring systems. It explains how electrical signals convey system information and the functions of system components like transducers, amplifiers, oscillators, analog to digital converters and digital to analog converters. It also discusses the effects of noise on systems and how system output is determined from a given input.
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.
The document discusses key concepts in data transmission including:
1) Transmission occurs over guided or unguided media between a transmitter and receiver.
2) Signals can be analyzed in the frequency domain and have properties like frequency, spectrum, and bandwidth.
3) Both analog and digital signals are used to represent data for transmission.
An Overview of Digital Communication and TransmissionDon Norwood
The document provides an overview of digital communication and transmission systems. It describes the key components of transmitters and receivers, including encoders, modulators, RF sections, and antennas. It also discusses baseband systems, sampling processes, quantization, pulse amplitude modulation (PAM), and non-uniform quantization techniques like μ-law and A-law compression used for voice communication. Aliasing is described as high frequencies taking on the identity of lower frequencies in sampled signals, and methods to eliminate it like anti-aliasing filters and increasing the sampling rate are presented.
The Presentation is as per the syllabus of the subject ”Digital Communication” of B.E. VIth Semester of Sant Gadge Baba Amravati University, Maharashtra, India
Contents are
Digital Communication System
Line Coding
Scrambling
The document discusses various communication channels and transmission mediums. It describes wired mediums like two-wire open lines, coaxial cable, and twisted pair lines. It also describes wireless transmission methods like microwave communication, radio, and satellite communication. For each medium, it provides details on bandwidth capacity, common types used, and advantages and disadvantages. The document also discusses channel capacity concepts like Nyquist rate and Shannon-Hartley theorem, and how noise affects channel capacity and data rates.
Analog communication System Basic Introduction by A Sravan KumarAPPALASRAVANKUMAR
This document discusses analog communication systems and key concepts related to noise. It describes the basic communication process involving a sender, receiver, and communication channel. It defines noise as any unwanted signal added to the desired message signal. Noise can reduce signal bandwidth, require increased transmitting power, and cause misunderstanding of signals. Noise is classified as either external noise from man-made, atmospheric, or extraterrestrial sources, or internal noise such as thermal, shot, time transit time, and miscellaneous noises. The document also discusses signal-to-noise ratio, defined as the ratio of signal power to noise power, and how it is expressed in decibels. Finally, it mentions noise factor, noise figure, and noise temperature as related
The document discusses concepts related to digital transmission and binary data representation. It covers topics such as binary transmission conventions, synchronization of digital signals, baseband data rates and error rates, digital transmission modes and operations, transmission over voice-grade circuits, periodic signals, frequency domain concepts, analog transmission of digital data, information capacity, error detection and correction techniques, protocols, synchronization techniques, and digital modulation techniques including amplitude shift keying and frequency shift keying.
This document discusses various methods of information transmission including digital-to-digital, analog-to-digital, transmission modes, digital-to-analog, and analog-to-analog conversion. It describes techniques such as line coding, block coding, pulse code modulation, delta modulation, asynchronous/synchronous/isochronous transmission, and analog modulation methods including amplitude, frequency, and phase modulation. The key steps and processes involved in each conversion technique are explained, along with considerations for bandwidth and how analog or digital signals are represented.
This document provides an overview of digital communication and covers several topics:
- It describes different types of transmission media including guided media like twisted pair cable, coaxial cable, and fiber optic cable. It also covers unguided or wireless media.
- It discusses characteristics of different transmission media and how signals are transmitted through them. This includes concepts like attenuation, distortion, and noise.
- It defines key terms used to measure signal quality like decibels and signal-to-noise ratio.
This document discusses key concepts in signal transmission including:
- There are two main types of signals - analog and digital. Analog signals are wave-based while digital signals are discrete zeros and ones. Conversion between analog and digital is sometimes needed.
- Frequency refers to the number of complete cycles per second, with the unit Hertz. Amplitude is the magnitude of the wave at a given point. Bandwidth is the amount of data that can be carried in a given time period, usually expressed in bits per second.
- Transmission can be synchronous, with data transferred in blocks, or asynchronous, transferring data character by character or frame by frame to accommodate slower or varying strength channels.
This document discusses various concepts related to communication systems, including:
- The basic elements of a communication system are a transmitter that converts a signal, a channel or medium for transmission, and a receiver that converts the signal back. Noise can interfere with the transmitted information.
- Types of communication include one-way or two-way, analog or digital signals, and baseband or modulated signals. Serial and parallel transmission methods are also covered.
- Key concepts discussed include bandwidth, data rate, baud rate, Nyquist theorem, signal-to-noise ratio, error handling codes, Shannon's theorem, and the electromagnetic spectrum. Noise sources and types are also defined.
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.
Wireless Communication and Networking by WilliamStallings Chap2Senthil Kanth
Hai I'm Senthilkanth, doing MCA in Mepco Schlenk Engineering College..
The following presentation covers topic called Wireless Communication and Networking
by WilliamStallings for BSc CS, BCA, MSc CS, MCA, ME students.Make use of it.
Wireless Communication and Networking
by WilliamStallings Chapter : 2Transmission Fundamentals
Chapter 2
Electromagnetic Signal
Function of time
Can also be expressed as a function of frequency
Signal consists of components of different frequencies
Time-Domain Concepts
Analog signal - signal intensity varies in a smooth fashion over time
No breaks or discontinuities in the signal
Digital signal - signal intensity maintains a constant level for some period of time and then changes to another constant level
Periodic signal - analog or digital signal pattern that repeats over time
s(t +T ) = s(t ) -¥< t < +¥
where T is the period of the signal
Time-Domain Concepts
Aperiodic signal - analog or digital signal pattern that doesn't repeat over time
Peak amplitude (A) - maximum value or strength of the signal over time; typically measured in volts
Frequency (f )
Rate, in cycles per second, or Hertz (Hz) at which the signal repeats
Time-Domain Concepts
Period (T ) - amount of time it takes for one repetition of the signal
T = 1/f
Phase () - measure of the relative position in time within a single period of a signal
Wavelength () - distance occupied by a single cycle of the signal
Or, the distance between two points of corresponding phase of two consecutive cycles
Sine Wave Parameters
General sine wave
s(t ) = A sin(2ft + )
Figure 2.3 shows the effect of varying each of the three parameters
(a) A = 1, f = 1 Hz, = 0; thus T = 1s
(b) Reduced peak amplitude; A=0.5
(c) Increased frequency; f = 2, thus T = ½
(d) Phase shift; = /4 radians (45 degrees)
note: 2 radians = 360° = 1 period
Sine Wave Parameters
Time vs. Distance
When the horizontal axis is time, as in Figure 2.3, graphs display the value of a signal at a given point in space as a function of time
With the horizontal axis in space, graphs display the value of a signal at a given point in time as a function of distance
At a particular instant of time, the intensity of the signal varies as a function of distance from the source
Frequency-Domain Concepts
Fundamental frequency - when all frequency components of a signal are integer multiples of one frequency, it’s referred to as the fundamental frequency
Spectrum - range of frequencies that a signal contains
Absolute bandwidth - width of the spectrum of a signal
Effective bandwidth (or just bandwidth) - narrow band of frequencies that most of the signal’s energy is contained in
Frequency-Domain Concepts
Any electromagnetic signal can be shown to consist of a collection of periodic analog signals (sine waves) at different amplitudes, frequencies, and phases
The period of the total signal is equal to the period of the fundamenta
This includes Digital signal data transmission, Base band and band pass transmission. Also detailed with PAM, PPM, PWM, PCM, DPCM, DM, ADM, ASK, PSK, FSK.
The document discusses telecommunications basics, including:
1) Signals carry information through a communication channel via variations in amplitude, frequency, or other physical properties over time.
2) Analog signals can be converted to digital signals by sampling and coding, allowing more robust transmission.
3) Modulation encodes information onto carrier signals to allow multiple users to share channels. Demodulation retrieves the original information.
4) Techniques like frequency division, time division, and code division multiplexing allow channels to be shared between multiple users.
Here are the key points about different communication systems, channel capacity, and the difference between FDM and TDM:
- Different types of communication systems include: radio/TV broadcasting, public switched telephone network (PSTN), cellular networks, computer networks, satellite systems, Bluetooth, fiber optic systems, etc.
- Channel capacity refers to the maximum rate at which information can be transmitted over a communications channel with an arbitrarily low error rate. It is calculated using the Shannon-Hartley theorem as C=B*log2(1+S/N) where B is bandwidth, S is signal power, and N is noise power.
- FDM (frequency-division multiplexing) divides the available bandwidth into non-
This document discusses concepts related to data transmission, including analog and digital signals and data. It explains that data can be either analog or digital, and signals used for transmission can be either. Analog signals vary continuously over time, while digital signals switch between discrete states. The document also covers transmission impairments like attenuation, delay distortion, and noise that can degrade signals during transmission. Repeaters are used in digital transmission to regenerate signals and overcome these impairments without noise accumulation.
This document summarizes key concepts from Chapter 3 of William Stallings' book "Data and Computer Communications". It defines common data transmission terminology like transmitters, receivers, guided and unguided mediums. It also describes analog and digital signals and data, how different types of data like voice, video and computer data are transmitted, and factors that impair transmission like attenuation, delay distortion, and noise. Finally, it covers channel capacity concepts like data rate, bandwidth, the Nyquist bandwidth theorem, and Shannon's channel capacity formula.
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 concepts related to electromagnetic signals and digital data transmission. It covers topics such as:
- Analog vs. digital signals and how they are represented over time.
- Key parameters of signals like amplitude, frequency, period, and phase.
- Relationships between bandwidth, data rate, and channel capacity for digital transmission.
- Different transmission media like guided (copper, fiber) and unguided (wireless) and their frequency ranges.
- Multiplexing techniques like frequency-division and time-division that allow multiple signals to be transmitted over a single medium.
The document describes information and energy control systems. It discusses block diagrams of typical information systems like audio and process monitoring systems. It explains how electrical signals convey system information and the functions of system components like transducers, amplifiers, oscillators, analog to digital converters and digital to analog converters. It also discusses the effects of noise on systems and how system output is determined from a given input.
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.
The document discusses key concepts in data transmission including:
1) Transmission occurs over guided or unguided media between a transmitter and receiver.
2) Signals can be analyzed in the frequency domain and have properties like frequency, spectrum, and bandwidth.
3) Both analog and digital signals are used to represent data for transmission.
An Overview of Digital Communication and TransmissionDon Norwood
The document provides an overview of digital communication and transmission systems. It describes the key components of transmitters and receivers, including encoders, modulators, RF sections, and antennas. It also discusses baseband systems, sampling processes, quantization, pulse amplitude modulation (PAM), and non-uniform quantization techniques like μ-law and A-law compression used for voice communication. Aliasing is described as high frequencies taking on the identity of lower frequencies in sampled signals, and methods to eliminate it like anti-aliasing filters and increasing the sampling rate are presented.
The Presentation is as per the syllabus of the subject ”Digital Communication” of B.E. VIth Semester of Sant Gadge Baba Amravati University, Maharashtra, India
Contents are
Digital Communication System
Line Coding
Scrambling
The document discusses various communication channels and transmission mediums. It describes wired mediums like two-wire open lines, coaxial cable, and twisted pair lines. It also describes wireless transmission methods like microwave communication, radio, and satellite communication. For each medium, it provides details on bandwidth capacity, common types used, and advantages and disadvantages. The document also discusses channel capacity concepts like Nyquist rate and Shannon-Hartley theorem, and how noise affects channel capacity and data rates.
Analog communication System Basic Introduction by A Sravan KumarAPPALASRAVANKUMAR
This document discusses analog communication systems and key concepts related to noise. It describes the basic communication process involving a sender, receiver, and communication channel. It defines noise as any unwanted signal added to the desired message signal. Noise can reduce signal bandwidth, require increased transmitting power, and cause misunderstanding of signals. Noise is classified as either external noise from man-made, atmospheric, or extraterrestrial sources, or internal noise such as thermal, shot, time transit time, and miscellaneous noises. The document also discusses signal-to-noise ratio, defined as the ratio of signal power to noise power, and how it is expressed in decibels. Finally, it mentions noise factor, noise figure, and noise temperature as related
The document discusses concepts related to digital transmission and binary data representation. It covers topics such as binary transmission conventions, synchronization of digital signals, baseband data rates and error rates, digital transmission modes and operations, transmission over voice-grade circuits, periodic signals, frequency domain concepts, analog transmission of digital data, information capacity, error detection and correction techniques, protocols, synchronization techniques, and digital modulation techniques including amplitude shift keying and frequency shift keying.
This document discusses various methods of information transmission including digital-to-digital, analog-to-digital, transmission modes, digital-to-analog, and analog-to-analog conversion. It describes techniques such as line coding, block coding, pulse code modulation, delta modulation, asynchronous/synchronous/isochronous transmission, and analog modulation methods including amplitude, frequency, and phase modulation. The key steps and processes involved in each conversion technique are explained, along with considerations for bandwidth and how analog or digital signals are represented.
This document provides an overview of digital communication and covers several topics:
- It describes different types of transmission media including guided media like twisted pair cable, coaxial cable, and fiber optic cable. It also covers unguided or wireless media.
- It discusses characteristics of different transmission media and how signals are transmitted through them. This includes concepts like attenuation, distortion, and noise.
- It defines key terms used to measure signal quality like decibels and signal-to-noise ratio.
This document discusses key concepts in signal transmission including:
- There are two main types of signals - analog and digital. Analog signals are wave-based while digital signals are discrete zeros and ones. Conversion between analog and digital is sometimes needed.
- Frequency refers to the number of complete cycles per second, with the unit Hertz. Amplitude is the magnitude of the wave at a given point. Bandwidth is the amount of data that can be carried in a given time period, usually expressed in bits per second.
- Transmission can be synchronous, with data transferred in blocks, or asynchronous, transferring data character by character or frame by frame to accommodate slower or varying strength channels.
This document discusses various concepts related to communication systems, including:
- The basic elements of a communication system are a transmitter that converts a signal, a channel or medium for transmission, and a receiver that converts the signal back. Noise can interfere with the transmitted information.
- Types of communication include one-way or two-way, analog or digital signals, and baseband or modulated signals. Serial and parallel transmission methods are also covered.
- Key concepts discussed include bandwidth, data rate, baud rate, Nyquist theorem, signal-to-noise ratio, error handling codes, Shannon's theorem, and the electromagnetic spectrum. Noise sources and types are also defined.
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.
Wireless Communication and Networking by WilliamStallings Chap2Senthil Kanth
Hai I'm Senthilkanth, doing MCA in Mepco Schlenk Engineering College..
The following presentation covers topic called Wireless Communication and Networking
by WilliamStallings for BSc CS, BCA, MSc CS, MCA, ME students.Make use of it.
Wireless Communication and Networking
by WilliamStallings Chapter : 2Transmission Fundamentals
Chapter 2
Electromagnetic Signal
Function of time
Can also be expressed as a function of frequency
Signal consists of components of different frequencies
Time-Domain Concepts
Analog signal - signal intensity varies in a smooth fashion over time
No breaks or discontinuities in the signal
Digital signal - signal intensity maintains a constant level for some period of time and then changes to another constant level
Periodic signal - analog or digital signal pattern that repeats over time
s(t +T ) = s(t ) -¥< t < +¥
where T is the period of the signal
Time-Domain Concepts
Aperiodic signal - analog or digital signal pattern that doesn't repeat over time
Peak amplitude (A) - maximum value or strength of the signal over time; typically measured in volts
Frequency (f )
Rate, in cycles per second, or Hertz (Hz) at which the signal repeats
Time-Domain Concepts
Period (T ) - amount of time it takes for one repetition of the signal
T = 1/f
Phase () - measure of the relative position in time within a single period of a signal
Wavelength () - distance occupied by a single cycle of the signal
Or, the distance between two points of corresponding phase of two consecutive cycles
Sine Wave Parameters
General sine wave
s(t ) = A sin(2ft + )
Figure 2.3 shows the effect of varying each of the three parameters
(a) A = 1, f = 1 Hz, = 0; thus T = 1s
(b) Reduced peak amplitude; A=0.5
(c) Increased frequency; f = 2, thus T = ½
(d) Phase shift; = /4 radians (45 degrees)
note: 2 radians = 360° = 1 period
Sine Wave Parameters
Time vs. Distance
When the horizontal axis is time, as in Figure 2.3, graphs display the value of a signal at a given point in space as a function of time
With the horizontal axis in space, graphs display the value of a signal at a given point in time as a function of distance
At a particular instant of time, the intensity of the signal varies as a function of distance from the source
Frequency-Domain Concepts
Fundamental frequency - when all frequency components of a signal are integer multiples of one frequency, it’s referred to as the fundamental frequency
Spectrum - range of frequencies that a signal contains
Absolute bandwidth - width of the spectrum of a signal
Effective bandwidth (or just bandwidth) - narrow band of frequencies that most of the signal’s energy is contained in
Frequency-Domain Concepts
Any electromagnetic signal can be shown to consist of a collection of periodic analog signals (sine waves) at different amplitudes, frequencies, and phases
The period of the total signal is equal to the period of the fundamenta
This includes Digital signal data transmission, Base band and band pass transmission. Also detailed with PAM, PPM, PWM, PCM, DPCM, DM, ADM, ASK, PSK, FSK.
The document discusses telecommunications basics, including:
1) Signals carry information through a communication channel via variations in amplitude, frequency, or other physical properties over time.
2) Analog signals can be converted to digital signals by sampling and coding, allowing more robust transmission.
3) Modulation encodes information onto carrier signals to allow multiple users to share channels. Demodulation retrieves the original information.
4) Techniques like frequency division, time division, and code division multiplexing allow channels to be shared between multiple users.
Here are the key points about different communication systems, channel capacity, and the difference between FDM and TDM:
- Different types of communication systems include: radio/TV broadcasting, public switched telephone network (PSTN), cellular networks, computer networks, satellite systems, Bluetooth, fiber optic systems, etc.
- Channel capacity refers to the maximum rate at which information can be transmitted over a communications channel with an arbitrarily low error rate. It is calculated using the Shannon-Hartley theorem as C=B*log2(1+S/N) where B is bandwidth, S is signal power, and N is noise power.
- FDM (frequency-division multiplexing) divides the available bandwidth into non-
This document discusses concepts related to data transmission, including analog and digital signals and data. It explains that data can be either analog or digital, and signals used for transmission can be either. Analog signals vary continuously over time, while digital signals switch between discrete states. The document also covers transmission impairments like attenuation, delay distortion, and noise that can degrade signals during transmission. Repeaters are used in digital transmission to regenerate signals and overcome these impairments without noise accumulation.
This document summarizes key concepts from Chapter 3 of William Stallings' book "Data and Computer Communications". It defines common data transmission terminology like transmitters, receivers, guided and unguided mediums. It also describes analog and digital signals and data, how different types of data like voice, video and computer data are transmitted, and factors that impair transmission like attenuation, delay distortion, and noise. Finally, it covers channel capacity concepts like data rate, bandwidth, the Nyquist bandwidth theorem, and Shannon's channel capacity formula.
The document provides information on analog and digital communication systems. It discusses the basic components of a communication system including the information source, transducer, transmitter, channel, receiver and destination. It also describes different analog modulation techniques like amplitude modulation and frequency modulation. The document discusses cellular wireless networks, their components like mobile station, base station, switching center and the concept of frequency reuse. It provides details on transmitting and receiving process in cellular networks and mobility management techniques like handoff. It concludes with an overview of first generation cellular technology.
UNIT 2- UNDERSTANDING DIGITAL SIGNALS PART 2LeahRachael
This document provides an overview of digital signals and their transmission. It discusses:
- Digital signals represented as a composite analog signal with infinite bandwidth and either discrete or continuous frequencies.
- The bandwidth of digital signals is defined by their bit rate, while analog signals bandwidth is defined by their frequency range.
- Digital signals can be transmitted over wide or band-limited channels using baseband or broadband transmission with modulation.
- Common digital modulation techniques include Pulse Amplitude Modulation, Pulse Code Modulation, Amplitude Shift Keying, Frequency Shift Keying, Phase Shift Keying, and Quadrature Amplitude Modulation.
This document provides an overview of key concepts in data communication and computer networks. It begins with definitions of data and data communication. It then describes the five components of data communication: message, sender, receiver, transmission medium, and protocol. It discusses transmission modes including parallel, serial, asynchronous, synchronous, and isochronous. It also covers direction of data flow, including simplex, half-duplex, and full-duplex. Additional topics include analog and digital signals, transmission impairments, network types and topologies, and hardware components such as NICs, hubs, switches, routers, and bridges.
This document discusses modern communication systems and their key components. It covers topics like analog vs digital signals, modulation techniques like amplitude modulation and frequency modulation, multiplexing, cellular networks from 1G to 4G, and key technologies like OFDM used in 4G. The document provides detailed explanations of the components of a basic communication system including the information source, transducer, transmitter, channel, receiver, and destination. It also discusses concepts like modulation index, carrier swing, noise factor, and SNR.
This document discusses digital transmission of digital data and baseband transmission. It explains that digital signals are binary in nature, representing data as 1s and 0s. Baseband signals directly encode these digital pulses without a carrier signal. Signaling techniques like unipolar and bipolar signaling are discussed. Manchester encoding is also covered as a technique that encodes transitions in the signal. The document then shifts to discussing analog transmission of digital data, where modulation techniques like amplitude shift keying, frequency shift keying, and phase shift keying are used to convert digital signals to analog for transmission.
This document discusses various methods for compressing analog and digital data. It begins by explaining why analog signals are modulated, such as to allow for more efficient transmission. It then covers analog to digital conversion techniques like pulse code modulation (PCM). On the digital side, it discusses lossless compression methods like run-length encoding, Huffman encoding, and Lempel-Ziv encoding. Lossy compression techniques like JPEG and MPEG are also summarized. The document aims to provide an overview of different data compression strategies.
This document provides an overview of basic communication systems. It discusses the main components including the input transducer, transmitter, channel, receiver and output transducer. It also describes different transmission directions like simplex, half duplex and full duplex. The document outlines baseband and passband data transmissions and discusses asynchronous and synchronous transmission methods. It introduces different types of communication channels including guided media like twisted wire, coaxial cable and fiber optic as well as wireless media like microwave and satellite. Finally, it maps out the electromagnetic frequency spectrum and discusses international standards and current wireless communication systems.
This document discusses various topics related to data communications including:
1. A simplified model of data communications consisting of a source, transmitter, transmission system, receiver and destination.
2. Guided media such as twisted pair, coaxial cable, and optical fiber which have different characteristics like bandwidth and attenuation.
3. Wireless transmission using antennas and frequencies ranging from microwave to satellite to broadcast radio to infrared.
4. Key concepts in data communications including analog vs. digital signals, bandwidth, attenuation, noise and error rates which impact system design factors and capacity.
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4. 4
Digital Data Transmission
time
1 1 0 0 1 1 1 0 0
Each single bit can be represented by a signal element.
Each signal element takes some time to send.
Bit rate: the number of bits that can be sent out per unit of time.
5. 5
What is the objective?
• Maximize the data rate: number of bits that the system can
transmit in a unit of time
—within an acceptable bit error rate
• Why there could be bit errors?
—The signal received by the receiver is different from the signal sent
from the sender
• Usually, if data rate becomes higher, it is more difficult for the
receiver to recognize the signal
—higher data rate results in higher bit error rate
• In order to achieve high data rate with low bit error rate, we
need to study the principle of data communications
6. 6
Terminology (1)
• Data transmission occurs between transmitter and
receiver over some transmission medium.
• Signal: electromagnetic waves
—Can propagate along the transmission medium
• Transmission Medium
—Guided medium: the signals are guided along a physical
path
• e.g., twisted pair, coaxial cable, optical fiber
—Unguided medium: wireless
• e.g., air, water, vacuum
7. 7
Terminology (2)
• Direct link
—Refer to the transmission path between the transmitter and receiver in
which signals propagate directly with no intermediate devices, other
than amplifiers or repeaters used to increase signal strength.
—Note that it can apply to both guided and unguided media
• A transmission medium is point-to-point if:
—Direct link
—Only 2 devices share the medium
• A transmission medium is multipoint if:
—More than two devices share the same medium
Point-to-point
Multipoint
8. 8
Terminology (3)
• Simplex transmission
—Signals are transmitted in only one direction
• e.g. Television
• Half duplex
—Signals can be transmitted in either direction, but only one
way at a time.
• e.g. police radio
• Full duplex
—Both stations may transmit simultaneously.
• e.g. telephone
9. 9
Signals: Time Domain
• We are concerned with electromagnetic signals used as a means to transmit
data.
• A signal is generated by the transmitter and transmitted over a medium.
• The signal is a function of time, but it can also be expressed as a function
of frequency.
• Time domain concepts: an electromagnetic signal can be either analog or
digital
— Analog signal
• The signal intensity varies in a smooth fashion over time. Or, there is no breaks or
discontinuities in the signal.
— Digital signal
• The signal intensity maintains a constant level for some period of time and then
changes to another constant level.
• Time domain function of a signal: s(t)
— Specifies the amplitude (in volts) of the signal at each instant in time.
11. 11
Periodic
Signals
Concept of periodic signal
• The same signal pattern repeats over
time.
• Otherwise, a signal is aperiodic.
Sine Wave: represented by three parameters,
s(t)=Asin(2 ft+)
• Peak Amplitude (A)
— maximum strength of signal
— measured in volts
• Frequency (f)
— Rate of change of signal
— Hertz (Hz) or cycles per second
— Period = time for one repetition (T)
— T = 1/f
• Phase ()
— Relative position in time within a single
period of a signal
Figure (a) displays the value of a signal at a
given point in space as a function of time.
13. 13
Signals: Frequency Domain
• In practice, an electromagnetic signal will be made up of
many frequencies.
—A frequency means a pure sine wave Asin(2 ft+)
• It can be shown (by Fourier analysis) that any signal is made
up of components at various frequencies, in which each
component is a sinusoid.
—By adding together enough sinusoidal signals, each with the
appropriate amplitude, frequency, and phase, any electromagnetic
signal can be constructed.
—Any electromagnetic signal can be shown to consist of a collection of
periodic analog signals (sine waves) at different amplitudes,
frequencies, and phases.
• Frequency domain function of a signal: S(f)
—Specifies the peak amplitude of the constituent frequencies of the
signal.
15. 15
Frequency
Domain
Representations
This signal has infinite
number of frequency
components: from 0 to
infinity
4/π
4/3π
(4/π)sin2πft
(4/3π)sin2π(3f)t
This signal is the same as
signal (c) in the previous
slide
16. 16
Spectrum & Bandwidth
• Spectrum of a signal
—the range of frequencies contained in the signal
• Absolute bandwidth of a signal
—the width of the signal spectrum
—Many signals have an infinite bandwidth!
• Effective bandwidth of a signal
—often just referred to as bandwidth
—the narrow band of frequencies containing “most” of the signal energy
• DC Component (dc: direct current)
—the component of zero frequency (i.e., f = 0)
—With no dc component, a signal has an average amplitude of zero.
—With a dc component, a signal has a frequency term at f = 0 and a
nonzero average amplitude.
19. 19
Data Rate and Bandwidth
• Effective bandwidth is the band within which most of the
signal energy is concentrated. Here, “most” is somewhat
arbitrary.
• Although a given waveform may contain frequencies over a
very broad range, as a practical matter, any transmission
system will be able to accommodate only a limited band of
frequencies.
—because of the limitation of transmitter & medium & receiver
—This limits the data rate that can be carried on the transmission system.
20. 20
Effective Bandwidth
• Effective bandwidth is one property of transmission
system.
• If the effective bandwidth of the input signal is larger
than the bandwidth of transmission system, the
output signal will be distorted a lot!
• The signal’s bandwidth should match the bandwidth
supported by the transmission system.
Transmission System
Input signal Output signal
21. 21
Part 2: Analog and Digital Data
Transmission
• The two terms “analog” and “digital” are used
frequently in the following three contexts:
—Data
• Entities that convey meaning or information
—Signals
• electromagnetic representations of data
—Transmission
• The communication of data by the propagation and processing of
signals
• Analog: continuous
• Digital: discrete
22. 22
Analog and Digital Data
• Analog data
— Continuous values within some interval
• Represented by real numbers
— How aloud is the sound?
— How bright is the color?
— What is your weight?
• Digital data
— Discrete values, e.g., text, integers
• Computers use digital data
— Even double precision floating numbers are discrete!
— In practice, digital data are used to approximate analog data
• E.g., the brightness of color can be represented by 0, 1, …, 255
• The loudness of the sound can be represented by 0, 1, …, 255
— Digital data are stored as bit stream in computers.
Digitized into digital data
23. 23
Analog and Digital Signals
• In a communication system, data are propagated from one
point to another by means of electromagnetic signals.
• Now we consider the signal generated by the transmitter.
• Analog signal
—Propagated over a variety of media: wire, fiber optic, space
—Continuously varying according to the source information
• Speech bandwidth: 100Hz to 7kHz
• Video bandwidth: 4MHz
• Digital signal
—A sequence of voltage pulses
—Almost unlimited bandwidth
24. 24
Advantages & Disadvantages
of Digital Signals
• Generally cheaper than analog signaling
• Less susceptible to noise
• Suffer more from attenuation!
—Pulses become rounded and smaller
—Leads to loss of information
26. 26
Data and Signals
• Usually, we use digital signals for digital data and analog
signals for analog data
—Analog data are a function of time and occupy a limited frequency
spectrum; such data can be represented by an electromagnetic signal
occupying the same spectrum.
—Digital data can be represented by digital signals, with a different
voltage level for each of the two binary digits.
• Can use analog signal to carry digital data
—Modem: modulator/demodulator
—The modem converts a series of binary voltage pulses into an analog
signal by encoding the digital data onto a carrier frequency.
• Can use digital signal to carry analog data
—Codec (coder-decoder): the codec takes an analog signal that directly
represents the voice data and approximates that signal by a bit stream.
At the receiving end, the bit stream is used to reconstruct the analog
data.
29. 29
Analog Transmission
• Analog transmission is a means of transmitting analog signals
without regard to their content.
—The signals may represent analog or digital data.
—In either case, the analog signal will become weaker after a certain
distance.
—Therefore, the analog transmission system includes amplifiers to boost
the energy in the signal.
—Unfortunately, the amplifier also amplifies noise.
—With amplifiers cascaded to achieve long distances, the signal becomes
more and more distorted.
• For analog data such a voice, quite a bit of distortion can be tolerated and
the data remain intelligible.
• For digital data, cascaded amplifiers will introduce bit errors.
30. 30
Digital Transmission
• Digital transmission is concerned with the content of
the signal.
—It can use digital signal, or analog signal.
• Repeaters are used instead of amplifiers
—A repeater receives the signal, recovers the pattern of 1s
and 0s, regenerates the signal, and retransmits the signal.
—Amplifiers cannot do this, as the signal has no meaning of
0 or 1
• Attenuation is overcome, noise is not cumulative.
31. 31
Advantages of Digital
Transmission
• Digital transmission techniques are widely used because of the following
advantages:
— Digital technology
• The advent of low cost LSI/VLSI technology has caused a continuing drop in the cost
and size of digital circuitry.
— Data integrity
• With the use of repeaters, the effects of noise and other impairments are not
cumulative. Thus it is possible to transmit data longer distances and over lower
quality lines while maintaining the integrity of the data.
— Capacity utilization
• High bandwidth links become economical.
• High degree of multiplexing is easier with digital techniques.
— Security & Privacy
• Encryption technique can be readily applied to digital data and to analog data that
have been digitized.
— Integration
• By treating both analog and digital data digitally, all signals have the same form and
can be treated similarly. Thus economies of scale and convenience can be achieved
by integrating voice, video, and digital data.
34. 34
Part 3: Transmission Impairments
• With any communications system, the signal that is
received may differ from the signal that is
transmitted, due to various transmission impairments.
• Consequences:
—For analog signals: degradation of signal quality
—For digital signals: bit errors
• The most significant impairments include
—Attenuation and attenuation distortion
—Delay distortion
—Noise
35. 35
Attenuation
• Attenuation: signal strength falls off with distance.
• Depends on medium
— For guided media, the attenuation is generally exponential and thus is
typically expressed as a constant number of decibels per unit
distance.
— For unguided media, attenuation is a more complex function of
distance and the makeup of the atmosphere.
• Three considerations for the transmission engineer:
1. A received signal must have sufficient strength so that the electronic
circuitry in the receiver can detect the signal.
2. The signal must maintain a level sufficiently higher than noise to be
received without error.
These two problems are dealt with by the use of amplifiers or
repeaters.
36. 36
Attenuation Distortion
(Following the previous slide)
3. Attenuation is often an increasing function of frequency. This
leads to attenuation distortion:
• some frequency components are attenuated more than other
frequency components.
Attenuation distortion is particularly noticeable for analog
signals: the attenuation varies as a function of frequency,
therefore the received signal is distorted, reducing intelligibility.
37. 37
Delay Distortion
• Delay distortion occurs because the velocity of
propagation of a signal through a guided medium
varies with frequency.
• Various frequency components of a signal will arrive
at the receiver at different times, resulting in phase
shifts between the different frequencies.
• Delay distortion is particularly critical for digital data
—Some of the signal components of one bit position will
spill over into other bit positions, causing intersymbol
interference, which is a major limitation to maximum bit
rate over a transmission channel.
38. 38
Noise (1)
• For any data transmission event, the received signal will
consist of the transmitted signal, modified by the various
distortions imposed by the transmission system, plus
additional unwanted signals that are inserted somewhere
between transmission and reception.
• The undesired signals are referred to as noise, which is the
major limiting factor in communications system performance.
• Four categories of noise:
—Thermal noise
—Intermodulation noise
—Crosstalk
—Impulse noise
39. 39
Noise (2)
• Thermal noise (or white noise)
—Due to thermal agitation of electrons
—It is present in all electronic devices and transmission media, and is a
function of temperature.
—Cannot be eliminated, and therefore places an upper bound on
communications system performance.
• Intermodulation noise
—When signals at different frequencies share the same transmission
medium, the result may be intermodulation noise.
—Signals at a frequency that is the sum or difference of original
frequencies or multiples of those frequencies will be produced.
—E.g., the mixing of signals at f1 and f2 might produce energy at
frequency f1 + f2. This derived signal could interfere with an intended
signal at the frequency f1 + f2.
40. 40
Noise (3)
• Crosstalk
—It is an unwanted coupling between signal paths. It can occur by
electrical coupling between nearby twisted pairs.
—Typically, crosstalk is of the same order of magnitude as, or less than,
thermal noise.
• Impulse noise
—Impulse noise is non-continuous, consisting of irregular pulses or noise
spikes of short duration and of relatively high amplitude.
—It is generated from a variety of cause, e.g., external electromagnetic
disturbances such as lightning.
—It is generally only a minor annoyance for analog data.
—But it is the primary source of error in digital data communication.
41. 41
Part 4: Channel Capacity
• The maximum rate at which data can be transmitted over a given
communication channel, under given conditions, is referred to as the
channel capacity.
• Data rate
— The rate in bits per second (bps) at which data can be communicated
• Bandwidth
— In cycles per second, or Hertz
— Constrained by transmitter and the nature of the medium
• Error rate
— The rate at which errors occur, where an error is the reception of a 1 when a 0
was transmitted or the reception of a 0 when a 1 was transmitted.
• We would like to make as efficient use as possible of a given bandwidth,
i.e., we would like to get as high a data rate as possible at a particular limit
of error rate for a given bandwidth.
42. 42
Two Formulas
• Problem: given a bandwidth, what data rate can we
achieve?
• Nyquist Formula
—Assume noise free
• Shannon Capacity Formula
—Assume white noise
43. 43
Nyquist Formula
• Assume a channel is noise free.
• Nyquist formulation: if the rate of signal transmission
is 2B, then a signal with frequencies no greater than
B is sufficient to carry the signal rate.
—Given bandwidth B, highest signal rate is 2B.
• Why is there such a limitation?
—due to intersymbol interference, such as is produced by
delay distortion.
• Given binary signal (two voltage levels), the
maximum data rate supported by B Hz is 2B bps.
—One signal represents one bit
44. 44
Nyquist Formula
• Signals with more than two levels can be used, i.e., each
signal element can represent more than one bit.
—E.g., if a signal has 4 different levels, then a signal can be used to
represents two bits: 00, 01, 10, 11
• With multilevel signaling, the Nyquist formula becomes:
—C = 2B log2M
—M is the number of discrete signal levels, B is the given bandwidth, C
is the channel capacity in bps.
—How large can M be?
• The receiver must distinguish one of M possible signal elements.
• Noise and other impairments on the transmission line will limit the
practical value of M.
• Nyquist’s formula indicates that, if all other things are equal,
doubling the bandwidth doubles the data rate.
45. 45
Shannon Capacity Formula
• Now consider the relationship among data rate, noise, and error rate.
• Faster data rate shortens each bit, so burst of noise affects more bits
— At given noise level, higher data rate results in higher error rate
• All of these concepts can be tied together neatly in a formula developed by
Claude Shannon.
— For a given level of noise, we would expect that a greater signal strength
would improve the ability to receive data correctly.
— The key parameter is the SNR: Signal-to-Noise Ratio, which is the ratio of the
power in a signal to the power contained in the noise.
— Typically, SNR is measured at receiver, because it is the receiver that processes
the signal and recovers the data.
• For convenience, this ratio is often reported in decibels
— SNR = signal power / noise power
— SNRdb
= 10 log10 (SNR)
46. 46
Shannon Capacity Formula
• Shannon Capacity Formula:
—C = B log2(1+SNR)
—Only white noise is assumed. Therefore it represents the theoretical
maximum that can be achieved.
• This is referred to as error-free capacity.
• Some remarks:
—Given a level of noise, the data rate could be increased by increasing
either signal strength or bandwidth.
—As the signal strength increases, so do the effects of nonlinearities in
the system which leads to an increase in intermodulation noise.
—Because noise is assumed to be white, the wider the bandwidth, the
more noise is admitted to the system. Thus, as B increases, SNR
decreases.
47. 47
Example
• Consider an example that relates the Nyquist and Shannon
formulations. Suppose the spectrum of a channel is between 3
MHz and 4 MHz, and SNRdB = 24dB. So,
B = 4 MHz – 3 MHz = 1 MHz
SNRdB = 24 dB = 10 log10(SNR) SRN = 251
• Using Shannon’s formula, the capacity limit C is:
C = 106 x 1og2(1+251) ≈ 8 Mbps.
• If we want to achieve this limit, how many signaling levels are
required at least?
By Nyquist’s formula: C = 2Blog2M
We have 8 x 106 = 2 x 106 x log2M M = 16.
48. 48
KEY POINTS
• All of the forms of information can be represented by
electromagnetic signals. Depending on the transmission
medium and the communications environment, either
analog or digital signals can be used to convey
information.
• Any electromagnetic signals, analog or digital, is made
up of a number of constituent frequencies. A key
parameter that characterizes the signal is bandwidth,
which is the width of the range of frequencies that
comprises the signal. In general , the greater the
bandwidth of the signal, the greater its information-
carrying capacity.
49. 49
KEY POINTS
• A major problem in designing a communications
facility is transmission impairment, including
attenuation, distortion, and various types of
noise. For analog signals, transmission
impairments introduce random effects that
degrade the quality of the received information
and may affect intelligibility. For digital signals,
transmission impairments may cause bit errors
at the receiver.
50. 50
KEY POINTS
• The designer of a communications facility must deal
with four factors: the bandwidth of the signal, the data
rate that is used for digital information, the amount of
noise and other impairments, and the level of error rate
that is acceptable. The bandwidth is limited by the
transmission medium and the desire to avoid
interference with other nearby signals. Because
bandwidth is a scarce resource, we would like to
maximize the data rate that is achieved in a given
bandwidth. The data rate is limited by the bandwidth,
the presence of impairments, and the error rate that is
acceptable.