Networking Chapter 3 - Data and Signals, [3] Data and Signal, chap 3 Data and Signals, DATA AND SIGNALS, chp 2 - fundamentals of data and signals, Chapter 2, Fundamentals of data and signals, terms, Chapter 2 Fundamentals of Data and Signals, Chapter...
high frequency
Change in a short span of time means ________.
low frequency
Change over a long span of time means ________.
Analog
Continuous waveform (voice/music)
Hertz (Hz)
Cycles per second, or frequency.
14. The _________ product defines the number of bits that can fill the link. A) delay-amplitude B) frequency-amplitude C) bandwidth-period D) bandwidth-delay
D
2. _________ can impair a signal. A) Noise B) Attenuation C) Distortion D) All of the above
D
33. For a ______ channel, the Nyquist bit rate formula defines the theoretical maximum bit rate. A) low-pass B) bandpass C) noisy D) noiseless
D
9. In a time-domain plot, the horizontal axis is a measure of ________. A) phase B) signal amplitude C) frequency D) time
D
Digital Analog
Data can be ________.
The set of all textual characters or symbols and their corresponding binary patterns is called
Data code
Analog vs. Digital = Strengths
Data density is high Easy to process
Analog Data
Data that is represented by continuous waveforms, which can be at an infinite number of points between some given minimum and maximum.
in this technique a codec tracks the incoming analog data by assessing up or down "steps." During each time period, the codec determines whether the waveform has risen one delta step or dropped one delta step. If the waveform rises one delta step, a 1 is transmitted. If the waveform drops one delta step, a 0 is transmitted.
Delta Modulation
Digital
Discrete/non-continuous waveform (high voltage/low voltage)
____________ is an 8-bit code allowing 256 (28 = 256} possible combinations of textual symbols. These 256 combinations of textual symbols include all uppercase and lowercase letters
EBCDIC The Extended Binary Coded Decimal Interchange Code,
Digital Data
Entities that are represented by discrete waveforms, rather than continuous waveforms. Between a minimum value X and a maximum value Y, the discrete waveform takes on only a finite number of values.
Data
Entities that convey meaning within a computer or computer system.
Data
Entities that convey meaning. Example: computer files, music on CD, results from a blood gas analysis machine)
Frequency Modulation
FM works by varying the instantaneous frequency of the wave.
Noiseless
For a ______ channel, the Nyquist bit rate formula defines the theoretical maximum bit rate.
Noisy
For a ______ channel, we need to use the Shannon capacity to find the maximum bit rate.
Hz (Hertz)
Frequency is represented as ______ value.
this technique uses two different frequency ranges to represent data values of 0 and 1,
Frequency shift key
Nonzero to Zero Inverted (NRZ-I)
Has a voltage change at the beginning of a 1 and no voltage change at the beginning of a 0. Example applications: Local Area Networks
Amplitude
Height of wave above/below a reference point, measured in volts
infinite
If a signal changes instantaneously, its frequency is __________.
zero
If a signal does not change at all, its frequency is ______.
Bandpass
If the available channel is a ____ channel, we cannot send a digital signal directly to the channel.
57 KHz
If the bandwidth of a signal is 5 KHz and the lowest frequency is 52 KHz, what is the highest frequency?
-2
If the maximum amplitude of a sine wave is 2 V, the minimum amplitude is ________ V.
this technique represents 0's and 1's by different changes in the phase of a waveform
Phase shift keying
in this technique a codec converts the analog data to a digital signal by tracking the analog waveform and taking "snapshots" of the analog data at fixed intervals.
Pulse Code Modulation
Spectrum
Range of frequencies that a signal spans from minimum to maximum
Spectrum
Range of frequency that signal spans from minimum to maximum Example: Average voice has frequency range roughly 300 Hz to 3100 Hz Spectrum is 300 - 3100 Hz
Frequency
In a frequency-domain plot, the horizontal axis measures the ________.
Time
In a time-domain plot, the horizontal axis is a measure of ________.
analog to analog
In order to transmit analog data, you can modulate the data onto a set of analog signals telephone, AM and FM radio, broadcast TV, Cable TV systems
Loss of Signal Strength
It is called Attenuation Measured in decibel Example: If a signal starts at 100 Watts and ends at 50 Watts, what is the signal strength loss in decibel: Db = 10 log to base 10 (P2/P1) 10 log to base 10 (50/100) 10 log to base 10 (0.5) 10 x 0.3 = 3Db
Analog vs. Digital = Weaknesses
It is harder to separate noise from an analog signal than it is to separate noise from a digital signal. From a slight hiss in the background to a complete loss of signal
digital data
It refers to information that has discrete states and can have only a limited number of values.
analog data
It refers to information that is continuous and can have an infinite number of values.
frequency domain
It refers to the analysis of mathematical functions or signals with respect to frequency, rather than time.
phase
Itdescribes the position of the waveform relative to time 0.
Attenuation
Loss of power or strength. Denoted as a decibel (dB) loss.
this encoding scheme has the following properties: To transmit a 1, the signal changes from low to high in the MIDDLE of the interval, and to transmit a 0, the signal changes from high to low in the MIDDLE of the interval.
Manchester
Transmit Analog Data using Analog Signals
Modulate data onto a set of analog signals at set of frequencies at different channels so that different frequencies coexist in different channel
this encoding scheme has a voltage change at the beginning of a 1 and no voltage change at the beginning of a 0
Non-return to zero inverted (NRZI):
this encoding scheme transmits 1's as zero voltages and 0's as positive voltages
Non-return to zero-level (NRZ-L)
what are the type of modulation techniques used to transmit digital data with discrete analog ?
(1) Amplitude shift key (2) Frequency shift key (3) phase shift keying (4) quadrature phase shift keying (5) quadrature amplitude modulation
what are the three most important data codes?
(1) EBCDIC (2) ASCII (3) UNICODE
what are the six encoding schemes used to transmit digital data with square wave digital?
(1) Non-return to zero-level (NRZ-L) (2) Non-return to zero inverted (NRZI) (3) Manchester (4) differential Manchester (5) bipolar-AMI (6) 4B/5B
what are the Techniques used to transmit analog data with digital signals
(1) pulse code modulation (2) delta modulation
Phase
-the position of the waveform relative to a given moment of time or relative to time zero; -a change in phase can be any number of angles between 0 and 360 degrees; -Phase changes often occur on common angles such as 45, 90. 135, etc
What are the 4 main combinations of data and signals:
1. Analog data transmitted using analog signals 2. Digital data transmitted using digital signals 3. Digital data transmitted using discrete analog signals 4. Analog data transmitted using digital signals
value of a signal changes
1. changes over a very short span of time --> f is high 2. changes over a long span of time --> f is low
Sine wave
1. most fundamental form of a periodic analog signal.
this encoding scheme takes 4 bit of data, converts it into a unique 5 bit sequence and then encodes the 5 bit using NRZI
4B/5B digital encoding scheme
Digital to digital
5 techniques to convert digital data into digital signals 1 NRZ-L, 2. NRZl 3. Bipolar AMI 4. manchester, 5. differential manchester; LANs and telephone systems
13. A _________ sine wave is not useful in data communications; we need to send a _______ signal. A) single-frequency; composite B) composite; single frequency This is the correct answer. C) single-frequency; double-frequency D) none of the above
A
15. _______ signals can have only a limited number of values. A) Digital B) Analog C) (a) or (b) D) None of the above
A
24. _____ signals can have an infinite number of values in a range. A) Analog B) Digital C) (a) or (b) D) None of the above
A
25. A(n)_________ signal is a composite analog signal with an infinite bandwidth. A) digital B) analog C) either (a) or (b) D) neither (a) nor (b)
A
28. ________ is a type of transmission impairment in which an outside source such as crosstalk corrupts a signal. A) Noise B) Distortion C) Attenuation D) Decibel
A
American Standard Code for Information Interchange (ASCII)
A 7-bit code that is used to represent all the printable characters on a keyboard plus many non-printable control characters.
Unicode
A character encoding technique that can represent all the languages on the planet.
Self-Clocking
A characteristic of a signal in which the signal changes at a regular pattern, which allows the receiver to stay synchronized with the signal's incoming bit stream.
Codec
A device that accepts analog data and converts it into digital signals. This process is also known as digitization.
Manchester Code
A digital encoding scheme that ensures that each bit has a signal change in the middle of the bit and thus solves the synchronization problem.
4B/5B
A digital encoding scheme that takes 4 bits of data, converts the 4 bits in to a unique 5-bit sequence, and encodes the 5 bits using NRZI.
Non-return to Zero inverted (NRZI) Code
A digital encoding technique that assigns a binary 1 or a binary 0 by the voltage change or lack of voltage change at the beginning of the bit.
Non-return to Zero-Level (NRZ-L) Code
A digital encoding technique that assigns a binary 1 or binary 0 to a low or high voltage level.
Differential Manchester Code
A digital encoding technique that transmits a binary 0 when there is a voltage change at the beginning of the bit frame, and transmits a binary 1 when there is no voltage change at the begininng of the bit frame. This technique ensures that there is always a voltage transition in the middle of the bit frame.
Bipolar-AMI
A digital encoding technique with no DC-component; logic 9s are denoted by zero voltage, and logic 1s are denoted by alernating positive and negative voltages.
Delta Modulation
A method of converting analog data to a digital signal in which the incoming analog signal is tracked and a binary 1 or 0 is transmitted when the analog signal rises or falls.
Frequency Shift Keying
A modulation technique for encoding digital data using various frequencies of an analog signal.
Phase Shift Keying
A modulation technique for encoding digital data using various phases of an analog signal.
Amplitude Shift Keying
A modulation technique for endcoding digital data using various amplitude levels of an analog signal.
Quadrature Phase Shift Keying
A modulation technique that incorporates four different phase angles, each of which represents 2 bits.
Quadrature Amplitude Modulation
A modulation technique that incorporates multiple phase angles with multiple amplitude levels to produce numerous combinations, creating a bps that is greather than the baud rate.
1 KHz
A periodic signal completes one cycle in 0.001 s. What is the frequency?
Decibel
A relative measure of signal loss or gain and is used to measure logarithmic loss or gain of a signal.
Decibel (dB)
A relative measure of signal loss or gain that is used to measure the strength of a signal.
ASCII
A set of all textual characters/symbols and their corresponding binary pattern.
EBCDIC
A set of all textual characters/symbols and their corresponding binary pattern.
UNICODE
A set of all textual characters/symbols and their corresponding binary pattern. Each character is 16 bits, support large number of languages per character set Ex: T - 0000 0000 0101 0100 r - 0000 0000 0111 0010 a - 0000 0000 0110 0001
Amplitude
A signal can change amplitude as time progresses.
P2 is equals to P1
A signal is measured at two different points. The power is P1 at the first point and P2 at the second point. The dB is 0. This means ________.
Time; Frequency
A sine wave in the ______ domain can be represented by one single spike in the _____ domain.
Periodic and Continuous
A sine wave is ________.
Shift Keying
A technique in which digital data is converted to an analog signal for transmission over a telephone line.
Shannon's Theorem
A theorem that demonstrates that the data rate of a signal is proportional to the frequency of the signal and its power level, and inversely proportional to the singal's noise level.
Nyquist's Theorem
A theorem that states that the data transfer rate of a signal is a function of the frequency of the signal and the number of signal levels.
Digital signal
A(n)_________ signal is a composite analog signal with an infinite bandwidth.
Amplitude Modulation
AM works by varying the strength (amplitude) of the carrier in proportion to the waveform being sent.
is a government standard in the United States and is one of the most widely used data codes in the world. set exists in a few different forms, including a 7-bit version that allows for 128 (27 = 128) possible combinations of textual symbols,
ASCII The American Standard Code for Information Interchange
Bandwidth
Absolute value of difference between minimum and maximum freq. of signal Example: Average voice has frequency range roughly 300 Hz to 3100 Hz Bandwidth - Absolute value of difference between 3100 and 300 which is 2800 Hz
Bandwidth
Absolute value of the difference between the lowest and highest frequencies of a signal
All signals have three components
Amplitude Frequency Phase
Extended Binary Coded Decimal Interchange Code (EBCDIC)
An 8-bit code allowing 256 possible combinations of textual symbols (2 to the 8th power = 256).
Delta Modulation
An analog waveform is tracked, using a binary 1 to represent a rise in voltage, and a 0 to represent a drop
Pulse Code Modulation (PCM)
An encoding technique that converts analog data to a digital signal. Also known as digitization.
curve waveforms
Analog signal is represented by a ___________.
Decreases
As frequency increases, the period ________.
10. _______ data are continuous and take continuous values. A) digital B) analog C) (a) or (b) D) none of the above
B
11. Frequency and period are ______. A) proportional to each other B) inverse of each other C) the same D) none of the above
B
16. Before data can be transmitted, they must be transformed to ________. A) periodic signals B) electromagnetic signals C) aperiodic signals D) low-frequency sine waves
B
18. ________ is a type of transmission impairment in which the signal loses strength due to the different propagation speeds of each frequency that makes up the signal. A) Noise B) Distortion C) Attenuation D) Decibel
B
21. _______ data have discrete states and take discrete values. A) Analog B) Digital C) (a) or (b) D) None of the above
B
22. For a ______ channel, we need to use the Shannon capacity to find the maximum bit rate. A) noiseless B) noisy C) low-pass D) bandpass
B
23. What is the bandwidth of a signal that ranges from 1 MHz to 4 MHz? A) 1 KHz B) 3 MHz C) 4 MHz D) none of the above
B
27. The _____ of a composite signal is the difference between the highest and the lowest frequencies contained in that signal. A) period B) bandwidth C) frequency D) amplitude
B
29. _______ describes the position of the waveform relative to time 0. A) Amplitude B) Phase C) Frequency D) Voltage
B
30. Given two sine waves A and B, if the frequency of A is twice that of B, then the period of B is ________ that of A. A) one-half B) twice C) the same as D) indeterminate from
B
31. As frequency increases, the period________. A) increases B) decreases C) doubles D) remains the same
B
34. In a frequency-domain plot, the horizontal axis measures the ________. A) phase B) frequency C) slope D) peak amplitude
B
Low pass
Baseband transmission of a digital signal is possible only if we have a ____ channel.
The number of times a signal changes value per second is called the?
Baud rate
Electromagnetic signal
Before data can be transmitted, they must be transformed to ________.
in this encoding scheme when a device transmits a binary 0, a zero voltage is transmitted. When the device transmits a binary 1, either a positive voltage or a negative voltage is transmitted.
Bipolar-AMI
1. If the maximum amplitude of a sine wave is 2 V, the minimum amplitude is ________ V. A) 2 B) 1 C) -2 D) between -2 and 2
C
12. When propagation speed is multiplied by propagation time, we get the________. A) wavelength of the signal B) throughput C) distance a signal or bit has traveled D) distortion factor
C
17. Data can be ________. A) digital B) analog C) (a) or (b) D) none of the above
C
19. Signals can be ________. A) digital B) analog C) either (a) or (b) D) neither (a) nor (b)
C
20. A sine wave is ________. A) periodic and discrete B) aperiodic and discrete C) periodic and continuous D) aperiodic and continuous
C
26. A periodic signal completes one cycle in 0.001 s. What is the frequency? A) 1 Hz B) 100 Hz C) 1 KHz D) 1 MHz
C
32. If the available channel is a ____ channel, we cannot send a digital signal directly to the channel. A) low-pass B) low rate C) bandpass D) high rate
C
7. A sine wave in the ______ domain can be represented by one single spike in the _____ domain. A) time; phase B) frequency; time C) time; frequency D) phase; time
C
8. If the bandwidth of a signal is 5 KHz and the lowest frequency is 52 KHz, what is the highest frequency? A) 5 KHz B) 47 KHz C) 57 KHz D) 10 KHz
C
The frequency at which the snapshots are taken is called?
Sampling rate
Digital Analog
Signals can be ________.
Analog Signal
Signals that are represented by continuous waveforms, which can be at an infinite number of points between some given minimum and maximum.
Digital
Square wave
Bandwidth
The _____ of a composite signal is the difference between the highest and the lowest frequencies contained in that signal.
Bandwidth-delay
The _________ product defines the number of bits that can fill the link.
Bandwidth
The absolute value of the difference between the lowest and highest frequencies.
PCM (Pulse Code Modulation)
The analog waveform is sampled at specific intervals and the "snapshots" are converted to binary values. Example application - Telephone system, Music system
Effective Bandwidth
The bandwidth of a signal after noise and other factors such as environmental conditions have been applied.
what makes the Bipolar-AMI encoding scheme unique?
The bipolar-AMI encoding scheme is unique it uses three voltage levels.
Attenuation
The continuous loss of strength (power) that a signal experiences as it travels through a medium.
Quantization Levels
The divisions of the y-axis that are used in pulse code modulation.
Signals
The electric or electromagnetic encoding of data. Signals are used to transmit data.
Signal
The electric or electromagnetic impulses used to encode and transmit data. Ex: Telephone conversation/webpage download
Digital Signals
The electric or eletromagnetic encoding of data that is represented by discrete waveforms rather than continuous waveforms. Between a minimum value X and a maximum value Y, the discrete waveform takes on only a finite number of values.
Quantization Error
The error that is introduced during digitization. Also known as quantization noise.
Amplification
The gain of the signal strength (power) of an analog signal.
Amplitude
The height of the wave above or below a given reference point It also can denote the current level of the signal or the power level of the signal.The amplitude of a signal can be expressed as volts, amps, or watts.
Amplitude
The height of the wave, above or below a given reference point.
Period
The length, or time interval of one cycle.
Quantization Noise
The noise that occurs during digitization.
Intermodulation Distortion
The noise that occurs when the frequencies of two or more signals mix together and create new frequencies.
Slope Overload Noise
The noise that results during analog-to-digital conversion when the analog waveform rises or drops too quickly and the hardware tracking it is not able to keep up with the change.
Bits Per Second (bps)
The number of bits that are transmitted across a medium in a given second.
Baud Rate
The number of signal elements or signal level changes per second.
Frequency
The number of times a signal makes a complete cycle within a given time frame; frequency is measured in Hertz (Hz), or cycles per second (period = 1 / frequency)
Frequency
The number of times a signal makes a complete cycle within a given time frame.
Frequency
The number of times a signal makes a complete cycle within a given time frame; measured in Hertz (Hz), or cycles per second.
Phase
The position of the waveform relative to a given moment of time or relative to time zero A change in phase can be any number of angles between 0 and 360 degrees Phase changes often occur on common angles, such as 45, 90, 135, etc.
Phase
The position of the waveform relative to a given moment of time or relative to time zero.
Phase
The position of the waveform relative to given moment of time or relative to time zero.
Digitization
The process of converting an analog signal or data into digital data.
Modulation
The process of converting digital data into an analog signal.
Modulate
The process of sending data over a signal by varying either its amplitude, frequency or phase.
Spectrum
The range of frequencies that a signal spans from minimum to maximum.
Sampling Rate
The rate at which an analog input is sampled in order to convert it to a digital stream of 1's and 0's.
Data Code
The set of all textual character or symbols and their corresponding binary patterns.
Digital
The signal can only appear in a fixed number of forms
Data Rate
The speed at which data is transmitted between two devices; often refered to in bits per second (bps).
Fundamentals of Signals
Three basic components - Amplitude, Frequency, Phase
Pulse Amplitude Modulation (PAM)
Tracking an analog waveform and converting it to pulses that represent the wave's height above or below a threshold; part of pulse code modulation.
Nonreturn to zero-level (NRZ-L)
Transmits 1s as zero voltages and 0s as positive voltages. Example applications: Local Area Networks
is an encoding technique that provides a unique coding value for every character in every language, no matter what the platform. Currently, Unicode supports more than 110 different code charts
Unicode
Noise
Unwanted electrical or electromagnetic energy that degrades the quality of signals and data.
PSK (Phase Shift Keying)
Vary Phase, keep frequency/phase constant, While one phase change encodes a 0, another phase change encodes a 1. Example Application - DSL, Cable modem, Digital Broadcast TV
ASK (Amplitude Shift Keying)
Vary amplitude, keep frequency/Phase constant. While one amplitude encodes a 0, another amplitude encodes a 1 Example application: DSL, Cable modem, Digital Broadcast TV
FSK (Frequency Shift Keying)
Vary frequency, keep amplitude/phase constant. While one frequency encodes a 0, another frequency encodes a 1 Example application: DSL, Cable modem, Digital Broadcast TV
3 MHz
What is the bandwidth of a signal that ranges from 1 MHz to 4 MHz?
what are the two fundamental difference between NRZ-L and NRZI?
With NRZ-L, the receiver must check the voltage level for each bit to determine whether the bit is a 0 or a 1. With NRZI, the receiver must check whether there is a change at the beginning of the bit to determine if it is a 0 or a 1.
ASCII
a 7-bit code that is used to represent all the printable characters on a keyboard plus many non-printable control characters
Unicode
a character encoding technique that can represent all the languages on the planet
self-clocking
a characteristic of a signal in which the signal changes at a regular pattern, which allows the receiver to stay synchronized with the signal's incoming bit stream
Analog
a continuous waveform with examples such as naturally ocurring music and voice; harder to separate noise from digital
codec
a device that accepts analog data and converts it into digital signals. This process is also known as digitization
Manchester code
a digital encoding scheme that ensures that each bit has a signal change in the middle of the bit and thus solves the synchronization problem
4B/5B
a digital encoding scheme that takes 4 bits of data, converts the 4 bits into a unique 5-bit sequence, and encodes the 5 bits using NRZI
nonreturn to zero inverted (NRZI) code
a digital encoding technique that assigns a binary 1 or a binar 0 by the voltage change or lack of voltage change, respectively, at the beginning of the bit
nonreturn to zero-level (NRZ-L)
a digital encoding technique that assigns a binary 1 or binary 0 to a lower or high voltage level, respectively
differential Manchester code
a digital encoding technique that transmits a binary 0 when there is a voltage change at the beginning of the bit frame, and transmits a binary 1 when there is no voltage change at the beginning of the bit frame. This technique ensures that there is always a voltage transition in the middle of the bit frame
bipolar-AMI
a digital encoding technique with no DC-component; logic 0s are denoted by zero voltage, and logic 1s are denoted by alternating positive and negative voltages
Digital
a discreet or non-continuous wave; signal can only appear in a fixed number of forms
delta modulation
a method of converting analog data to a digital signal in which the incoming analog signal is tracked and a binary 1 or 0 is transmitted, respectively, when the analog signal rises or falls
amplitude shift keying
a modulation technique for encoding digital data using various amplitude levels of an analog signal
frequency shift keying
a modulation technique for encoding digital data using various frequencies of an analog signal
phase shift keying
a modulation technique for encoding digital data using various phases of an analog signal
quadrature phase shift keying
a modulation technique that incorporates four different phase angles, each of which represents 2 bits: a 45-degree phase shift represents a data value of 11; a 135-degree phase shift represents 10; a 225-degree phase shift represents 01, and a 315-degree phase shift represents 00.
quadrature amplitude modulation
a modulation technique that incorporates multiple phase angles with multiple amplitude levels to produce numerous combinations, creating a bps that is greater than the baud rate
decibel (dB)
a relative measure of signal loss or gain that is used to measure the strength of a signal
simple periodic analog signal
a sine wave, can not be decomposed into simpler signal.
shift keying
a technique in which digital data is converted to an analog signal for transmission over a telephone line
Shannon's theorem
a theorem that demonstrates that the data rate of a signal is proportional to the frequency of the signal and its power level, and inversely proportional to the signal's noise level
Nyquist's theorem
a theorem that states that the data transfer rate of a signal is a function of the frequency of the signal and the number of signal levels
frequency - bandwidth
absolute value of the difference between the lowest and highest frequencies of a signal
Loss of signal strength
all signals experience loss (attenuation)
in this technique a data value of 1 and a data value of 0 are represented by two different amplitudes of a signal.
amplitude shift keying
3 basic techniques transmitting digital data with discrete analog signals
amplitude shift keying frequency shift keying phase shift keying --two or more can be combined
3 fundamentals of signals
amplitude, frequency and phase
Digital to analog
amplitude, frequency and phase shift keying; modem devices; dial up, DSL and cable modem systems
All signals consist of three basic components
amplitude, frequency, and phase.
EBCDIC
an 8-bit code allowing 256 possible combinations of textual symbols (2^8 = 256)
pulse code modulation (PCM)
an encoding technique that converts analog data to a digital signal. Also known as digitization
Because both data and signals can be either digital or analog, four basic combinations of data and signals are possible
analog data converted to an anlaog signal, digital data converted to a square-wave digital signal, digital data converted to a discrete analog signal, and analog data converted to a digital signal.
when is transmitting analog data with digital signals necessary ?
analog data is converted to digital signals so that the original data can be transmitted through a computer system and eventually stored in memory or on a magnetic disk.
4 combinations of data and signals
analog to analog; Digital to digital; digital to analog; analog to digital
why are Manchester encoding schemes called self-clocking ?
because the occurrence of a regular transition is similar to seconds ticking on a clock.
periodic or nonperiodic can be used in
both analog and digital signals
A nonperiodic signal
changes without exhibiting a pattern or cycle that repeats over time.
signals
computer networks and data/voice communication systems transmit signals
Analog
continuous waveform
4B/5B Digital encoding scheme
converts 4 bits of data into 5 bit quanties -5 bit quantities are unique in that no five bit code has more than 2 consecutive zeroes -5 bit code then transmitted using an NRZI encoded signal
what percentage of overhead can you expect when converting 4-bit code to 5-bit code?
creates a 20 percent overhead (one extra bit).
hertz (Hz)
cycles per second, or frequency
analog data
data that is represented by continuous waveforms, which can be at an infinite number of points between some given minimum and maximum
attenuation
denoted as a decibel (dB) loss; decibal losses (and gains) are additive
wavelength in data communication
describe the transmission of light in an optical fiber.
Phase
describes the position of the waveform relative to time O.
in this encoding scheme if there is a transition at the beginning of the interval, then a 0 is being transmitted. If there is no transition at the beginning of the interval, then a 1 is being transmitted.
differential Manchester
box style waveforms
digital signal is represented by a ___________.
digital data
entities that are represented by discrete waveforms, rather than continuous waveforms. Between a minimum value X and a maximum value Y, the discrete waveform takes on only a finite number of values
Data
entities that convey meaning (computer files, music on CD) within a computer or computer system; can be analog or digital
data
entities that convey meaning within a computer or computer system
Manchester Digital encoding shemes
every bit has at least one significant change. Some bits have two signal changes per bit (baud rate = twice bps)
an average voice frequency
frequency 300Hz to 3100Hz spectrum 300-3100 Hz bandwidth 2800 Hz
Nonreturn to zero inverted (NRZI)
has a voltage change at the beginning of a 1 and no voltage change at the beginning of a 0
An analog signal has
infinitely many levels of intensity over a period of time.
Decibel (dB)
is a relative measure of signal loss or gain.
band limited signal
is a signal for which the amplitude S(f) = 0 for f > F1 and f < F2.
A composite periodic analog signal
is composed of multiple sine waves.
Peak Amplitude
is the absolute value of its highest intensity, proportional to the energy it carries. Example: Electric signal -- volt
what is the disadvantage of using NRZ-L/NRZI ?
long sequences of 0's in the data produce a signal that never changes. Often the receiver looks for signal changes so that it can synchronize its read- ing of the data with the actual data pattern.
A digital signal has
only a limited number of defined values.
Tracking an analog waveform and converting it to pulses that represent the wave's height above (or below) a threshold is called?
pulse amplitude modulation (PAM)
Analog to Digital
pulse code and delta modulation, Codec devices; Telephone and music systems
In this technique eight phase angles have a single amplitude, and four phase angles have double amplitudes, resulting in 16 different combinations.
quadrature amplitude modulation
this technique incorporates four different phase angles, each of which represents 2 bits:
quadrature phase shift keying
frequency - spectrum
range of frequencies that a signal spans from minimum to max.
what is the major disadvantage of the Manchester encoding scheme ?
roughly half the time there will be two transitions during each bit
analog signals
signals that are represented by continuous waveforms, which can be at an infinite number of points between some given minimum and maximum
If the analog waveform rises or drops too quickly, the codec may not be able to keep up with the change, causing _____________
slope overload noise
Digital
takes on the form of binary 1s and 0s
what is the most common form of data transmitted between a transmitter and a receiver?
textual data
bandwidth
the absolute value of the difference between the lowest and highest frequencies
effective bandwith
the bandwith of a signal after noise and other factors such as environmental conditions have been applied
attenuation
the continuous loss of strength (power) that a signal experiences as it travels through a medium
quantization levels
the divisions of the y-axis that are used in pulse code modulation
digital signals
the electric or electromagnetic encoding of data that is represented by discrete waveforms rather than continuous waveforms. Between a minimum value X and a maximum value Y, the discrete waveform takes on only a finite number of values
signals
the electric or electromagnetic encoding of data. Signals are used to transmit data
Signals
the electric or electromagnetic impulses used to encode and transmit data (telephone conversation, web page download); can be analog or digital
quantization error
the error that is introduced during digitization. Also known as quantization noise
amplification
the gain of the signal strength (power) of an analog signal
amplitude
the height of the wave above (or below) a given reference point
amplitude
the height of the wave above or below a given reference point
period
the length, or time interval, of one cycle
intermodulation distortion
the noise that occurs when the frequencies of two or more signals mix together and create new frequencies
slope overload noise
the noise that results during analog-to-digital conversion when the analog waveform rises or drops too quickly and the hardware tracking it is not able to keep up with the change
quantization noise
the nose that occurs during digitization. When the reproduced analog waveform is not an accurate representation of the original waveform, it is said that quantizing noise has been introduced. Also known as quantization error
bits per second (bps)
the number of bits that are transmitted across a medium in a given second
baud rate
the number of signal element or signal level changes per second
frequency
the number of times a signal makes a complete cycle within a given time frame
frequency
the number of times a signal makes a complete cycle within a given time frame, measured in Hertz (Hz) or cycles per second
phase
the position of the waveform relative to a given moment of time or relative to time zero
digitization
the process of converting an analog signal or data into digital data
modulation
the process of converting digital data into an analog signal
spectrum
the range of frequencies that a signal spans from minimum to maximum
sampling rate
the rate at which an analog input is sampled in order to convert it to a digital stream of 1s and 0s
data code
the set of all textual characters or symbols and their corresponding binary patterns
data rate
the speed at which data is transmitted between two devices; often referred to in bits per second (bps)
What is the major advantage that the Manchester scheme has over the NRZ scheme ?
there is always a transition in the middle of a bit. Thus, the receiver can expect a signal change at regular intervals and can synchronize itself with the incoming bit stream.
what is the primary advantage of 4B/5B digital encoding?
there will never be more than two 0's in a row transmitted If you never transmit more than two Os in a row using NRZI encoding, then you will never have a long period in which there is no signal transition.
pulse amplitude modulation (PAM)
tracking an analog waveform and converting it to pulses that represent the wave's height above (or below) a threshold; part of pulse code modulation
Nonreturn to Zero-level (NRZ-L)
transmits 1s as zero voltages and 0s as positive voltages
in this type of modulation, the analog signal takes on a discrete number of signal levels.
transmitting digital data with discrete analog signals
Bipolar - AMI encoding scheme
unique because it uses three voltage levels -When a device transmits a binary 0, a zero voltage is transmittted -When the device transmits a binary 1, either a positive voltage or a negative voltage is transmitted -Which of these is transmitted depends on the binary 1 value that was last transmitted?
noise
unwanted electrical or electromagnetic energy that degrades the quality of signals and data
how do you calculate a maximum data rate ?
use Shannon's equation S(f) = f x log2 (1 + S/N)• M = (V + Vn)/Vn, - M →Number of message at one transmission - V →Voltage of signal - Vn →Voltage of noise
data communications
use periodic analogs signals and nonperiodic digital signals.
what is the primary advantage of the Bipolar-AMI scheme ?
when all the voltages are added together after a long transmission, there should be a total voltage of zero. That is, the positive and negative voltages essentially cancel each other out.
Noise in digital signal
you can still discern a high voltage from a low voltage; too much noise you cannot discern a high voltage from low voltage.
Digital data
Discrete data. Example: data stored in computer memory
Twice
Given two sine waves A and B, if the frequency of A is twice that of B, then the period of B is ________ that of A.
Fourier Transform
It gives the frequency domain of a nonperiodic time domain signal.
sine wave
It is a continuous wave.
Sawtooth Signal/ wave
It is a kind of non-sinusoidal waveform and the name based on its resemblance to the teeth of a plain-toothed saw with a zero rake angle.
amplitude
It is a measure of a periodic variable of its change over a single period.
time limited signal
It is a signal for which the amplitude s(t) = 0 for t > T1 and t < T2
composite signal
It is a signal that is composed of other signals.
Fourier analysis
It is a tool that changes a time domain signal to a frequency domain signal and vice versa.
AM radio signal
It is an example of a nonperiodic composite signal.
composite periodic analog signal
It is composed of multiple sine waves.
bandwidth
It is defined as a range within a band of frequencies or wavelengths.
wavelength
It is measured in the direction of the wave.
bandwidth of a composite signal
It is the difference between the highest and the lowest frequencies contained in that signal.
frequency
It is the rate of change with respect to time.
4. A signal is measured at two different points. The power is P1 at the first point and P2 at the second point. The dB is 0. This means ________. A) P2 equals P1 B) P2 is zero C) P2 is much larger than P1 D) P2 is much smaller than P1
A
Single frequency; composite
A _________ sine wave is not useful in data communications; we need to send a _______ signal.
Analog data
A continuous representation of data. Example: sound make by human
A periodic signals
1. completes a pattern within a measurable time frame 2. the completion of one full pattern is called a cycle
Wavelength properties
1. depend of both the f and the medium 2. property of any type of signal.
Frequency formulas
1. f = 1/T 2. T= 1/f
signal plotting
1. horizontal axis -- time 2. the curve is for analog signal passes through an infinite number of points. 3. the vertical lines of the digital signal, demonstrate the sudden jump that the signal makes from value to value.
Wavelength
1. is another characteristic of a signal traveling through a transmission medium. 2. binds the period or the frequency of a simple sine wave to the propagation speed of the medium 3. is the distance a simple signal can travel in one period.
Measure phase
1. measured in degrees or radians [360° is 2n rad; 1° is 2n/360 rad, and 1 rad is 360/(2n)] 2. A phase shift of 360° corresponds to a shift of a complete period; 3. a phase shift of 180° corresponds to a shift of one-half of a period. 4. a phase shift of 90° corresponds to a shift of one-quarter of a period
Period vs. Frequency
1. period and frequency are just one characteristic defined in two ways. 2. Period is the inverse of frequency, and frequency is the inverse of period,
Period
1. refers to the amount of time, in seconds, a singal needs to complete 1 cycle. 2. expressed in seconds
Frequency
1. refers to the number of periods in 1 s. 2. expressed in Hertz (Hz), which is cycle per second.
Two Extremes
1. signal does not change at all, it never completes a cycle --> f = 0. 2. signal change instantaneously --> f is infinite and period = 0.
3 parameters of sine wave
1. the peak amplitude 2. the frequency 3. phase
3. ________is the rate of change with respect to time. A) Time B) Frequency C) Amplitude D) Voltage
B
5. Baseband transmission of a digital signal is possible only if we have a ____ channel. A) bandpass B) low-pass C) high rate D) low rate
B
6. ________ is a type of transmission impairment in which the signal loses strength due to the resistance of the transmission medium. A) Distortion B) Attenuation C) Noise D) Decibe
B
Inverse of each other
The relationship between frequency and period
Periodic analog signals
This can be classified as simple or composite
complete sine wave
This can be represented by one single spike in the frequency domain.
simple periodic analog signal
This cannot be decomposed into simpler signals.
time-domain
This may have a representation of three or more sine waves with frequencies.
single-frequency sine wave
This sine wave is not useful in data communications.
Distance a signal or bit has traveled
When propagation speed is multiplied by propagation time, we get the ________.
Analog signal
Which signal that can have an infinite number of values in a range.
Analog
_______ data are continuous and take continuous values.
Digital
_______ data have discrete states and take discrete values.
Phase
_______ describes the position of the waveform relative to time 0.
Digital
_______ signals can have only a limited number of values.
Noise
________ is a type of transmission impairment in which an outside source such as crosstalk corrupts a signal.
Distortion
________ is a type of transmission impairment in which the signal loses strength due to the different propagation speeds of each frequency that makes up the signal.
Attenuation
________ is a type of transmission impairment in which the signal loses strength due to the resistance of the transmission medium.
Noise Attenuation Distortion
_________ can impair a signal.
Frequency
________is the rate of change with respect to time.
