This document discusses various techniques for encoding digital data onto analog signals for transmission. It begins with an overview of encoding and modulation. Digital data can be encoded as either a digital or analog signal. When encoded as an analog signal, various modulation techniques can be used including amplitude shift keying, frequency shift keying, and phase shift keying. For digital to digital encoding, techniques like non-return to zero and biphase encoding are discussed. The techniques are evaluated based on factors like bandwidth usage, synchronization capability, and noise immunity. Overall, the document provides an overview of common encoding and modulation techniques used in data communications.
Digital Data, Digital Signal | Scrambling TechniquesBiplap Bhattarai
Digital signal is a sequence of discrete, discontinuous voltage pulses.
Each pulse is a signal element.
Binary data are transmitted by encoding the bit stream into signal elements.
In the simplest case, one bit is represented by one signal element.
- E.g., 1 is represented by a lower voltage level, and 0 is represented by a higher voltage level
The attached narrated power point presentation attempts to explain the methods of computation of total power loss and system rise time in a fiber optic link. The material will be useful for KTU final year B Tech students who prepare for the subject EC 405, Optical Communications.
Sampling Theorem, Quantization Noise and its types, PCM, Channel Capacity, Ny...Waqas Afzal
Sampling Theorem
Quantization
Noise and its types
Encoding-PCM
Power of Signal
Signal to noise Ratio
Channel Capacity
Nyquist Bandwidth
Shannon Capacity Formula
Multirate Digital Signal Processing-Up/Down Sampling
Applications
DVB is a set of standards that define digital broadcasting using existing satellite, cable, and terrestrial infrastructures.
The term digital television is sometimes used as a synonym for DVB
Serial Communication & Embedded System InterfaceKUET
Before using this presentation , one have to familiar with Embedded system , Various serial port for communication channel,basic knowledge of Matlab , Arduino ..
This a great opportunity for the searcher to get information of this topic .80% of the information provided in this slide was taken from the sparkfun , a very well known website for hardware project and tutorials . One can get more helpful information through this website .
Now, if you are looking for straight forward guideline for Serial Communication , well you are in the right place to have .So , get this if you want to , it's completely open source ( editable ) .
Farewell.
Digital Data, Digital Signal | Scrambling TechniquesBiplap Bhattarai
Digital signal is a sequence of discrete, discontinuous voltage pulses.
Each pulse is a signal element.
Binary data are transmitted by encoding the bit stream into signal elements.
In the simplest case, one bit is represented by one signal element.
- E.g., 1 is represented by a lower voltage level, and 0 is represented by a higher voltage level
The attached narrated power point presentation attempts to explain the methods of computation of total power loss and system rise time in a fiber optic link. The material will be useful for KTU final year B Tech students who prepare for the subject EC 405, Optical Communications.
Sampling Theorem, Quantization Noise and its types, PCM, Channel Capacity, Ny...Waqas Afzal
Sampling Theorem
Quantization
Noise and its types
Encoding-PCM
Power of Signal
Signal to noise Ratio
Channel Capacity
Nyquist Bandwidth
Shannon Capacity Formula
Multirate Digital Signal Processing-Up/Down Sampling
Applications
DVB is a set of standards that define digital broadcasting using existing satellite, cable, and terrestrial infrastructures.
The term digital television is sometimes used as a synonym for DVB
Serial Communication & Embedded System InterfaceKUET
Before using this presentation , one have to familiar with Embedded system , Various serial port for communication channel,basic knowledge of Matlab , Arduino ..
This a great opportunity for the searcher to get information of this topic .80% of the information provided in this slide was taken from the sparkfun , a very well known website for hardware project and tutorials . One can get more helpful information through this website .
Now, if you are looking for straight forward guideline for Serial Communication , well you are in the right place to have .So , get this if you want to , it's completely open source ( editable ) .
Farewell.
Exploiting Artificial Intelligence for Empowering Researchers and Faculty, In...Dr. Vinod Kumar Kanvaria
Exploiting Artificial Intelligence for Empowering Researchers and Faculty,
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at Integral University, Lucknow, 06.06.2024
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How to Make a Field invisible in Odoo 17Celine George
It is possible to hide or invisible some fields in odoo. Commonly using “invisible” attribute in the field definition to invisible the fields. This slide will show how to make a field invisible in odoo 17.
2024.06.01 Introducing a competency framework for languag learning materials ...Sandy Millin
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Published classroom materials form the basis of syllabuses, drive teacher professional development, and have a potentially huge influence on learners, teachers and education systems. All teachers also create their own materials, whether a few sentences on a blackboard, a highly-structured fully-realised online course, or anything in between. Despite this, the knowledge and skills needed to create effective language learning materials are rarely part of teacher training, and are mostly learnt by trial and error.
Knowledge and skills frameworks, generally called competency frameworks, for ELT teachers, trainers and managers have existed for a few years now. However, until I created one for my MA dissertation, there wasn’t one drawing together what we need to know and do to be able to effectively produce language learning materials.
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Safalta Digital marketing institute in Noida, provide complete applications that encompass a huge range of virtual advertising and marketing additives, which includes search engine optimization, virtual communication advertising, pay-per-click on marketing, content material advertising, internet analytics, and greater. These university courses are designed for students who possess a comprehensive understanding of virtual marketing strategies and attributes.Safalta Digital Marketing Institute in Noida is a first choice for young individuals or students who are looking to start their careers in the field of digital advertising. The institute gives specialized courses designed and certification.
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Operation “Blue Star” is the only event in the history of Independent India where the state went into war with its own people. Even after about 40 years it is not clear if it was culmination of states anger over people of the region, a political game of power or start of dictatorial chapter in the democratic setup.
The people of Punjab felt alienated from main stream due to denial of their just demands during a long democratic struggle since independence. As it happen all over the word, it led to militant struggle with great loss of lives of military, police and civilian personnel. Killing of Indira Gandhi and massacre of innocent Sikhs in Delhi and other India cities was also associated with this movement.
June 3, 2024 Anti-Semitism Letter Sent to MIT President Kornbluth and MIT Cor...Levi Shapiro
Letter from the Congress of the United States regarding Anti-Semitism sent June 3rd to MIT President Sally Kornbluth, MIT Corp Chair, Mark Gorenberg
Dear Dr. Kornbluth and Mr. Gorenberg,
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harassment and intimidation at the Massachusetts Institute of Technology (MIT). Failing to act decisively to ensure a safe learning environment for all students would be a grave dereliction of your responsibilities as President of MIT and Chair of the MIT Corporation.
This Congress will not stand idly by and allow an environment hostile to Jewish students to persist. The House believes that your institution is in violation of Title VI of the Civil Rights Act, and the inability or
unwillingness to rectify this violation through action requires accountability.
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students that opportunity and have been hijacked to become venues for the promotion of terrorism, antisemitic harassment and intimidation, unlawful encampments, and in some cases, assaults and riots.
The House of Representatives will not countenance the use of federal funds to indoctrinate students into hateful, antisemitic, anti-American supporters of terrorism. Investigations into campus antisemitism by the Committee on Education and the Workforce and the Committee on Ways and Means have been expanded into a Congress-wide probe across all relevant jurisdictions to address this national crisis. The undersigned Committees will conduct oversight into the use of federal funds at MIT and its learning environment under authorities granted to each Committee.
• The Committee on Education and the Workforce has been investigating your institution since December 7, 2023. The Committee has broad jurisdiction over postsecondary education, including its compliance with Title VI of the Civil Rights Act, campus safety concerns over disruptions to the learning environment, and the awarding of federal student aid under the Higher Education Act.
• The Committee on Oversight and Accountability is investigating the sources of funding and other support flowing to groups espousing pro-Hamas propaganda and engaged in antisemitic harassment and intimidation of students. The Committee on Oversight and Accountability is the principal oversight committee of the US House of Representatives and has broad authority to investigate “any matter” at “any time” under House Rule X.
• The Committee on Ways and Means has been investigating several universities since November 15, 2023, when the Committee held a hearing entitled From Ivory Towers to Dark Corners: Investigating the Nexus Between Antisemitism, Tax-Exempt Universities, and Terror Financing. The Committee followed the hearing with letters to those institutions on January 10, 202
Model Attribute Check Company Auto PropertyCeline George
In Odoo, the multi-company feature allows you to manage multiple companies within a single Odoo database instance. Each company can have its own configurations while still sharing common resources such as products, customers, and suppliers.
Synthetic Fiber Construction in lab .pptxPavel ( NSTU)
Synthetic fiber production is a fascinating and complex field that blends chemistry, engineering, and environmental science. By understanding these aspects, students can gain a comprehensive view of synthetic fiber production, its impact on society and the environment, and the potential for future innovations. Synthetic fibers play a crucial role in modern society, impacting various aspects of daily life, industry, and the environment. ynthetic fibers are integral to modern life, offering a range of benefits from cost-effectiveness and versatility to innovative applications and performance characteristics. While they pose environmental challenges, ongoing research and development aim to create more sustainable and eco-friendly alternatives. Understanding the importance of synthetic fibers helps in appreciating their role in the economy, industry, and daily life, while also emphasizing the need for sustainable practices and innovation.
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DATA COMMUNICATION
Signal Encoding Technique
Data Communications and Networking
Overview Encoding and Modulation
DIgita Data, Digital Signal
Digital Data, Analog Signal
Analog Data, Digital Signal
Analog Data, Analog Signal
Reading:
Book Chapter 5
Data and Computer Communications, 8th edition
By William Stallings
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Modulation
• Modulation is the process of encoding source data
onto a carrier signal with frequency fc.
—The frequency of the carrier signal is chosen to be
compatible with the transmission medium being used.
—Modulation techniques involve operation on one or more of
the three parameters: amplitude, frequency, and phase
• According to the input source signal m(t) (either
analog or digital), which is called baseband signal (or
modulating signal) , the carrier signal fc(t) will be
modulated into modulated signal s(t).
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Encoding/modulation Techniques
• Digital data, digital signal
—The equipment for encoding digital data into a digital signal
is less complex and less expensive than digital-to-analog
modulation equipment.
• Analog data, digital signal
—Conversion of analog data (e.g., voice, video) to digital form
permits the use of modern digital transmission & switching.
• Digital data, analog signal
—Optical system and unguided media (wireless system) only
propagate analog signals.
• Analog data, analog signal
—Baseband: easy and cheap, e.g., in voice-grade telephone
lines, voice signals are transmitted over telephone lines at
their original spectrum
—Modulation permits frequency division multiplexing, e.g.,
AM/FM radios
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(I) Digital Data, Digital Signal
• Digital signal is a sequence of discrete,
discontinuous voltage pulses.
• Each pulse is a signal element.
• Binary data are transmitted by encoding the
bit stream into signal elements.
• In the simplest case, one bit is represented by
one signal element.
—E.g., 1 is represented by a lower voltage level,
and 0 is represented by a higher voltage level
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Terminologies
• Unipolar
— If all signal elements have the same algebraic sign (all positive or
all negative), then the signal is unipolar.
• Polar
— One logic state represented by positive voltage, the other by
negative voltage
• Data rate
— Rate of data transmission measured in bps: bits per second
• Duration or length of a bit
— Time taken for transmitter to emit the bit
• Modulation rate
— Rate at which the signal level changes
— Measured in baud: signal elements per second
• Mark and Space
— Mark: Binary 1
— Space: Binary 0
How are they
related?
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Interpreting Signals at the Receiver
• The receiver needs to know
— The timing of each signal element, i.e., when a signal element
begins and ends
— signal levels
— These tasks are performed by sampling each element position in the
middle of the interval and comparing the value to a threshold.
• Factors affecting successful interpreting of signals
— Signal-to-noise ratio (SNR)
— Data rate
— Bandwidth
• Some principles:
— An increase in data rate increases bit error rate (BER)
— An increase in SNR decreases BER
— An increase in bandwidth allows an increase in data rate
• Another factor that can improve performance:
— Encoding scheme: the mapping from data bits to signal elements
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Evaluation of Encoding
Schemes (1)
• Signal Spectrum
— Lack of high frequencies reduces required bandwidth
— Lack of dc component allows ac coupling via transformer,
providing electrical isolation and reducing interference
— Concentrate power in the middle of the bandwidth
• Clocking
— Need to determine the beginning and end of each bit
— Synchronizing transmitter and receiver
1. Use external clock, which is expensive; or
2. Synchronization mechanism based on the transmitted signal
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Comparison of Encoding
Schemes (2)
• Error detection
—Various error-detection techniques will be covered in Chapter
9
—Some error detection capability can be built into signal
encoding scheme
• Signal interference and noise immunity
—Some codes are better than others in the presence of noise
—Performance is usually expressed in terms of BER
• Cost and complexity
—Higher signal rate (thus data rate) leads to higher cost
—Some codes require a signal rate greater than the actual data
rate
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Encoding Schemes
• Nonreturn to Zero (NRZ)
—Nonreturn to Zero-Level (NRZ-L)
—Nonreturn to Zero Inverted (NRZI)
• Multilevel Binary
—Bipolar-AMI
—Pseudoternary
• Biphase
—Manchester
—Differential Manchester
• Scrambling techniques
—B8ZS
—HDB3
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Nonreturn to Zero-Level (NRZ-L)
• Two different voltages for 0 and 1 bits
• Voltage is constant during a bit interval
—no transition, i.e. no return to zero voltage
• E.g. absence of voltage for zero, constant
positive voltage for one
• More often, negative voltage for one value
and positive for the other
• This is known as NRZ-L
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Nonreturn to Zero Inverted
• NRZI: Nonreturn to zero, invert on ones
• Constant voltage pulse for duration of bit
• Data are encoded as presence or absence of
signal transition at the beginning of the bit
time
• A transition (low to high or high to low)
denotes a binary 1
• No transition denotes binary 0
• NRZI is an example of differential encoding
technique
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Differential Encoding
• Data are represented in terms of the changes
between successive signal elements, rather
than the signal elements themselves.
• It is more reliable to detect a transition in
the presence of noise than to compare a
value to a threshold.
• With a complex transmission layouts, it is
easy to lose the sense of the polarity of the
signal.
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NRZ pros and cons
• Pros
—Easy to engineer
—Make efficient use of bandwidth
• Cons
—The presence of dc component
—The lack of synchronization capability
• NRZ codes are commonly used for digital
magnetic recording, but not often used for
signal transmission.
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Multilevel Binary
• Use more than two levels
• Bipolar-AMI: alternate mark inversion
—zero represented by no line signal
—one represented by a positive or negative pulse
—one pulses must alternate in polarity
—Advantages:
• No loss of synchronization if a long string of 1s occurs
(0s still be a problem)
• No net dc component
• Provides a simple means of error detection
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Trade-off for Multilevel Binary
• Not as efficient as NRZ
—In a 3 level system, each signal element could
represent log23 = 1.58 bits
—However, in biploar-AMI & pseudoternary, each
signal element only represents one bit
—Receiver must distinguish between three levels
(+A, -A, 0)
—Requires approx. 3dB more signal power for same
probability of bit error, or
—The BER for NRZ codes, at a given SNR, is
significantly less than for mulitlevel binary.
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Biphase
• Manchester
—There is a transition at the middle of each bit period.
—The midbit transition serves as a clock mechanism and also
as data: low to high represents 1, high to low represents 0
—Used by IEEE 802.3 Ethernet LAN
• Differential Manchester
—The midbit transition is used only to provide clocking.
—0 is represented by the presence of a transition at the
beginning of a bit period.
—1 is represented by the absence of a transition at the
beginning of a bit period.
—Note: this is a differential encoding scheme
—Used by IEEE 802.5 token ring LAN
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Biphase Pros and Cons
• Pros
—Self-clocking: Because there is a predictable
transition during each bit time, the receiver can
synchronize on that transition.
—No dc component
—Error detection: the absence of an expected
transition can be used to detect errors
• Con
—Requires at least one transition per bit time and
may have as many as two transitions, thus,
—The maximum modulation rate is twice that for
NRZ
—Requires more bandwidth
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Scrambling
• Use scrambling to replace sequences that would
produce constant voltage
• Main idea:
—Sequences that would result in a constant voltage are
replaced by filling sequences that will provide sufficient
transitions for the receiver’s clock to maintain
synchronization.
—Filling sequences must be recognized by receiver and
replaced with original data sequence.
—Filling sequence is the same length as original sequence.
• Design goals:
—No dc component
—No long sequences of zero-level line signals
—No reduction in data rate
—Error detection capability
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B8ZS
• Bipolar With 8-Zeros Substitution
• Based on bipolar-AMI, whose drawback is a long
string of zeros may result in loss of synchronization.
• If octet of all zeros occurs and the last voltage pulse
preceding this octet was positive, encode as 000+-0-+
• If octet of all zeros occurs and the last voltage pulse
preceding this octet was negative, encode as 000-
+0+-
• Causes two violations of AMI code
• Unlikely to occur as a result of noise
• Receiver recognizes the pattern and interprets the
octet as consisting of all zeros.
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HDB3
• High-Density Bipolar-3 Zeros
• Based on bipolar-AMI
• String of four zeros is replaced with sequences
containing one or two pulses.
Number of Bipolar Pulses since last
substitution
Polarity of
Preceding Pulse
Odd Even
- 000- +00+
+ 000+ -00-
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(II) Digital Data, Analog Signal
• E.g., Public telephone system
—Designed to transmit analog signals in 300Hz to 3400Hz
(limited by the central office, not the twisted pair cable)
—Use modem for digital data (modulator-demodulator)
• Modulation involves operation on one or more of the
three characteristics of a carrier signal
—Amplitude shift keying (ASK)
—Frequency shift keying (FSK)
• Binary FSK (BFSK)
• Multiple FSK (MFSK)
—Phase shift keying (PSK)
• Binary PSK (BPSK)
• Four-level PSK (QPSK)
• Multilevel PSK (MPSK)
• QAM: a combination of ASK and PSK
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Amplitude Shift Keying
• Values are represented by different amplitudes
of the carrier frequency
• Usually, one amplitude is zero
—i.e. presence and absence of carrier is used
• Inefficient: up to 1200bps on voice grade
lines
• ASK is used to transmit digital data over
optical fiber.
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Binary Frequency Shift Keying
• The most common form of FSK is binary FSK
(BFSK)
• Two binary values represented by two
different frequencies (near carrier frequency)
• BFSK is less susceptible to error than ASK.
• Up to 1200bps on voice grade lines
• Also used for high frequency (3 to 30MHz)
radio
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Phase Shift Keying
• In PSK, the phase of the carrier signal is
shifted to represent data.
• Binary PSK
—Two phases represent two binary digits
• Differential PSK
—Phase shifted relative to previous transmission
rather than some constant reference signal
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Multilevel PSK
• More efficient use of bandwidth
• Each signal element represents more than one
bit
• QPSK: quadrature PSK
—shifts of /2 (90o), i.e. 4 different phases
—Each signal element represents 2 bits
• Multilevel PSK
—Can use 8 or more phase angles, and each phase
can have more than one amplitude
—9600bps modem use 12 angles, four of which
have two amplitudes, in total 16 different signal
elements
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Quadrature Amplitude
Modulation
• QAM is used in the asymmetric digital
subscriber line (ADSL) and some wireless
standards.
• Combination of ASK and PSK
• A logical extension of QPSK
• Send two different signals simultaneously on
the same carrier frequency
—Use two copies of the carrier, one shifted by 90°
—Each carrier is ASK modulated
—Two independent signals over same medium
—Demodulate and combine for original binary
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QAM Levels
• Two level ASK
—Each of two streams in one of two states
—Four state system
—Essentially QPSK
• Four level ASK
—Combined stream in one of 16 states
• 64 and 256 state systems have been
implemented
• Improved data rate for given bandwidth
—Increased potential error rate
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(III) Analog Data, Digital Signal
• Digitization
—Conversion of analog data into digital data
• Digital data can then be transmitted using NRZ-L
• Digital data can then be transmitted using code other
than NRZ-L
• Digital data can then be converted to analog signal
—Analog to digital conversion done using a codec
(coder-decoder)
—Two principle codec techniques
• Pulse Code Modulation
• Delta modulation
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Pulse Code Modulation
• Sampling Theorem: If a signal is sampled at regular
intervals of time and at a rate higher than twice the
highest signal frequency, then the samples contain all
the information of the original signal.
• For example, voice data are limited to below 4000Hz
—8000 samples per second is sufficient to characterize the
voice signal.
• Samples are analog samples, called Pulse Amplitude
Modulation (PAM) samples.
• To convert to digital, each analog sample must be
assigned a binary code.
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Pulse Code Modulation
• Each sample is quantized into some level
—The original signal is now only approximated and
cannot be recovered exactly
—This effect is called quantizing error or quantizing
noise
• For example, 8 bit sample gives 256 levels
• 8000 samples per second and 8 bits per
sample gives 64kbps, for a single voice
signal.
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Nonlinear Encoding
• Typically, PCM scheme is refined using nonlinear
encoding.
• Quantization levels are not equally spaced.
• The problem of equal spacing:
—The mean absolute error for each sample is regardless of
signal level.
—Lower amplitude values are relatively more distorted.
• Nonlinear encoding:
—Use a greater number of quantizing steps for signals of low
amplitude, and a smaller number of quantizing steps for
signals of large amplitude
—Reduces overall signal distortion
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Delta Modulation
• Modulation:
—An analog signal is approximated by a staircase
function that moves up or down by quantization
level at each sampling interval.
—If the value of the sampled waveform exceeds that
of the staircase function, 1 is generated,
otherwise, 0 is generated.
• Two important parameters:
—The size of the step.
—The sampling rate.
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Delta Modulation
• Noise
—Slope overload noise (when the analog waveform
is changing rapidly than the staircase can follow)
—Quantizing noise (when the analog waveform is
changing slowly)
• Trade-off
—The quantizing noise increases as the size of the
step increases.
—The slope overload noise increases as the size of
the step decreases.
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(IV) Analog Data, Analog Signals
• Modulation:
—Combine an input signal m(t) and a carrier
frequency fc to produce a signal s(t) whose
bandwidth is usually centered on fc
• E.g., voice signals are transmitted over
telephone lines at their original spectrum.
• Types of modulation
—Amplitude modulation: AM
—Angle Modulation
• Frequency modulation: FM
• Phase modulation: PM
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KEY POINTS
• Both analog and digital information can be encoded
as either analog or digital signals. The particular
encoding that is chosen depends on the specific
requirements to be met and the media and
communications facilities available.
• Digital data, digital signal: The simplest form of
digital encoding of digital data is to assign one
voltage level to binary one and another to binary
zero. More complex encoding schemes are used to
improve performance, by altering the spectrum of the
signal and providing synchronization capability.
• Digital data, analog signal: A modem converts digital
data to an analog signal so that it can be transmitted
over an analog line. The basic techniques are ASK,
FSK, and PSK.
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KEY POINTS
• Analog data, digital signals: Analog data, such as voice and
video, are often digitized to be able to use digital transmission
facilities. The simplest technique is PCM (Pulse Code
Modulation), which involve sampling the analog data
periodically and quantizing the samples. Another technique is
Delta Modulation.
• Analog data, analog signals: Analog data are modulated by a
carrier frequency to produce an analog signal in a different
frequency band, which can be utilized on an analog
transmission system. The basic techniques are AM (Amplitude
Modulation), FM (Frequency Modulation), and PM (Phase
Modulation).
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