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ELEC 419 > Ch. 5 > Flashcards

Ch. 5 Flashcards

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1
Q

What is Simplex transmission?

A

Signals are transmitted in only one direction. One station is transmitter and the other is receiver.

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2
Q

Define Half Duplex transmission.

A

Both stations transmit, but only one at a time.

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3
Q

What is Full Duplex transmission?

A

Both stations may transmit simultaneously.

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4
Q

What is a Sine Wave?

A

The fundamental periodic signal represented by peak amplitude, frequency, period, and phase.

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5
Q

What is Peak Amplitude?

A

Maximum value or strength of the signal over time, typically measured in volts.

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6
Q

Define Frequency.

A

Rate at which the signal repeats, measured in Hertz (Hz) or cycles per second.

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7
Q

What is the Period of a signal?

A

The amount of time for one repetition, calculated as T = 1/f.

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8
Q

What is Phase in signal transmission?

A

Relative position in time within a single period of signal.

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9
Q

What is Wavelength?

A

The distance between successive peaks of a wave.

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10
Q

What is the relationship between data rate and bandwidth?

A

There is a direct relationship between data rate and bandwidth.

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11
Q

What impact has digital technology had on data transmission?

A

It has caused a continuing drop in the cost and size of digital circuitry.

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12
Q

How do repeaters affect data integrity?

A

They allow transmission of data longer distances over lower quality lines while maintaining integrity.

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13
Q

What is the significance of high bandwidth transmission links?

A

They require a high degree of multiplexing to utilize capacity effectively.

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14
Q

True or False: Encryption techniques can only be applied to analog data.

A

False: Encryption techniques can be applied to both digital data and digitized analog data.

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15
Q

Define Asynchronous Transmission.

A

Data are transmitted one character at a time without sending long, uninterrupted streams of bits.

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16
Q

What is Synchronous Transmission?

A

A block of bits is transmitted in a steady stream without start and stop codes.

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17
Q

What does a Frame consist of in data transmission?

A

Data plus preamble, postamble, and control information.

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18
Q

What are the main transmission impairments?

A
  • Attenuation and attenuation distortion
  • Delay distortion
  • Noise
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19
Q

Define Attenuation.

A

Signal strength falls off with distance over any transmission medium.

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20
Q

What is Delay Distortion?

A

Occurs when the propagation velocity of a signal through a guided medium varies with frequency.

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21
Q

What is Noise in transmission?

A

Unwanted disturbances that can affect the quality of the transmitted signal.

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22
Q

What is Crosstalk?

A

A signal from one line is picked up by another due to electrical coupling.

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23
Q

Define Impulse Noise.

A

Caused by external electromagnetic interferences, consisting of irregular pulses or spikes.

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24
Q

What is Nyquist Bandwidth?

A

The limitation of data rate in a noise-free channel is simply the bandwidth of the signal.

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25
What is the Nyquist formula for data rate?
C = 2B log2M, where C is the capacity, B is the bandwidth, and M is the number of signal elements.
26
What does Shannon's Capacity Formula relate?
It relates data rate, noise, and error rate considering the signal to noise ratio.
27
What is Digital Data, Digital Signal?
A digital signal is a sequence of discrete, discontinuous voltage pulses.
28
Define Unipolar encoding.
All signal elements have the same sign.
29
What is Polar encoding?
One logic state is represented by positive voltage and the other by negative voltage.
30
What is NRZ-L?
Nonreturn to Zero-Level encoding, using two different voltages for 0 and 1 bits.
31
Explain NRZI encoding.
Non-return to zero, invert on ones; constant voltage pulse for the duration of the bit.
32
What is Bipolar-AMI?
Uses more than two signal levels; Binary 0 represented by no line signal and Binary 1 by alternating positive or negative pulses.
33
What is the purpose of scrambling in data transmission?
To replace sequences that would produce constant voltage to maintain synchronization.
34
What does B8ZS stand for?
Bipolar with 8-zeros substitution, a coding scheme commonly used in North America.
35
What is HDB3?
A coding scheme based on bipolar-AMI that replaces sequences of four zeros based on the last pulse.
36
What is a digital signal?
Sequence of discrete, discontinuous voltage pulses ## Footnote Each pulse is a signal element.
37
Define unipolar in the context of digital signals.
All signal elements have the same sign.
38
What does polar mean in digital signal terminology?
One logic state represented by positive voltage and the other by negative voltage.
39
What is data rate?
Rate, in bits per second that data are transmitted.
40
What is the duration or length of a bit?
Time taken for transmitter to emit the bit.
41
What is modulation rate?
Rate at which the signal level is changed, expressed in baud.
42
What do mark and space refer to?
Binary digits 1 and 0.
43
How does an increase in SNR affect BER?
Decreases BER.
44
What is the impact of an increase in data rate on BER?
Increases BER.
45
How does an increase in bandwidth affect data rate and BER?
Increases data rate and increases BER.
46
What is the main use of digital data in an analog signal?
Public telephone system.
47
What frequency range does the public telephone system operate within?
300Hz to 3400Hz.
48
What device is used to convert digital data to analog signals?
Modem (modulator-demodulator).
49
What is the purpose of modulation?
Encoding source data into a carrier signal with frequency fc.
50
What is amplitude shift keying (ASK)?
Encode bit 0 and bit 1 by different carrier amplitudes.
51
How does ASK represent binary digits?
* 1 binary digit represented by presence of carrier (amplitude A) * 0 binary digit represented by absence of carrier (null amplitude).
52
What is binary frequency shift keying (BFSK)?
Two binary values are represented by two different frequencies near carrier.
53
List some applications of BFSK.
* Up to 1200bps on voice grade lines * High frequency radio * Even higher frequency on LANs using coaxial cable.
54
What is multiple FSK (MFSK)?
Each signaling element represents more than one bit using more than two frequencies.
55
What is phase shift keying (PSK)?
The phase of the carrier signal is shifted to represent data.
56
Define binary PSK.
Two phases represent the two binary digits.
57
What is differential PSK?
Phase shifted relative to previous transmission.
58
What is the baud rate if 1000 signal units are sent per second?
1000 bauds.
59
What is the relationship between transmission bandwidth and bit rate for ASK?
Bandwidth is directly related to bit rate.
60
What does QAM stand for?
Quadrature Amplitude Modulation.
61
What is the main advantage of QAM?
Combines ASK and PSK to send two different signals simultaneously.
62
What is digitization?
Conversion of analog data into digital data.
63
What is Pulse Code Modulation (PCM)?
Technique based on the sampling theorem for converting analog signals to digital.
64
What is the first step in Pulse Code Modulation?
Sampling: get analog samples using PAM sampler.
65
What is quantization in PCM?
Assigning a binary code to each of the analog samples.
66
What is Delta Modulation (DM)?
Analog input approximated by a staircase function with binary behavior.
67
What does the output of the delta modulation process represent?
A single binary digit for each sample.
68
What are some types of digital data modulation?
* Nonreturn to zero (NRZ) * Multilevel binary * Biphase.
69
What are some types of analog data modulation?
* Pulse code modulation * Delta modulation (DM).
70
What is a key performance factor for digital to analog modulation schemes?
Transmission bandwidth.

ELEC 419 (11 decks)

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