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CIS 3347 > Physical Layer - CH 3 (EXAM 1) > Flashcards

Physical Layer - CH 3 (EXAM 1) Flashcards

1
Q

What is the physical layer?

A

layer 1 in the internet model

contains physical and logical circuits to send transmission to data link layer

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2
Q

What are the 2 types of circuit configuration?

A

point to point (wired) - server – client computer

multipoint (wireless) - client computer - client computer

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3
Q

What is simplex data flow?

A

data flow in ONE direction

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4
Q

What is half-duplex data flow?

A

data flow in BOTH directions (one at a time)

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5
Q

What is a full-duplex?

A

data flows simultaneously in BOTH directions

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6
Q

What is multiplexing?

A

dividing high speed circuits into slower logical ones

saving $$$

frequency and time

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7
Q

What is frequency division multiplexing?

A

creates channels from the LARGER frequency band

guardbands separate channels to prevent interference

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8
Q

What is wavelength division multiplexing?

A

a variant of FDM in fiber optics circuits

makes use of MULTIPLE wavelengths to divide circuits into channels

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9
Q

What is time-division multiplexing?

A

circuit divided by devices taking turns
more efficient than FDM
equal turns

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10
Q

What is statistical time division multiplexing?

A

variant of TDM
reduce time slots based on network usage

may cause delays when usage does not match allocated slots

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11
Q

What is inverse multiplexing?

A

combines low-speed circuits into high-speed

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12
Q

What is media?

A

physical manner to carry vice or data transmission

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13
Q

What is guided media?

A

transmission flows along physical media

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14
Q

What is wireless media?

A

transmission flow through the air

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15
Q

What is a twisted pair cable?

A

guided media

(twisted-pair cable)wires bundled together
used for telephones and LAN

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16
Q

What is a coax cable?

A

guided media

single copper core, outer insulation, shielding, inner insulation

less prone to interference

cable tv / internet

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17
Q

What is a fiber optic cable?

A

guided media

optical core made of glass or plastic
data transmitted through LED’s
extremely fast data rates

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18
Q

What are fiber optics?

A

multimode
graded-index multimode
single-mode

19
Q

What is a radio?

A

wireless media

wireless transmission of electrical waves through air
mobile network communication
cordless, wireless LAN

20
Q

What is a microwave?

A

high-frequency radio communication

requires line of sight which requires antennas and towers

21
Q

What is a satellite?

A

special form of microwave communication

long distance leads to delays

22
Q

What are the factors of media selection?

A 
network type
cost
transmission distance
security
error rates
speeds
23
Q

What is a digital-analog?

A

discrete binary values (01)

24
Q

What is an analog?

A

transmission involves continuous waves (sin, cos)

25
Q

What is a parallel transmission mode?

A

multiple bits transmitted simultaneously

26
Q

What is a serial transmission mode?

A

bits transferred sequentially one at a time

27
Q

What do the sender and receiver have to agree on?

A 
set of symbols (voltages or light pulses)
symbol rate (how often sent)
28
Q

What is a unipolar signaling technique?

A

voltage is 0 or positive

represents binary bits

29
Q

What is a bipolar NRZ signaling technique?

A

voltage is positive or negative but NOT zero

30
Q

What is a bipolar RZ signaling technique?

A

voltage is positive or negative returning to 0 between each bit

31
Q

What is a bipolar AMI signaling technique?

A

voltage is 0, positive, negative, returns 0 between each bit, and alternates between a negative and positive voltage

32
Q

What is a manchester signaling technique?

A

voltage is positive or negative and bits are indicated by a mid bit transition

33
Q

What system was built for analog data?

A

telephone

needs a modem to convert analog to digital

34
Q

What are the 3 characteristics of waves?

A

amplitude (height of the wave)
frequency (waves/second)
phase (wave direction in degrees)

35
Q

What is a carrier wave?

A

basic wave transmitted through a circuit

36
Q

What is modulation?

A

modification of carrier wave’s fundamental characteristics in order to encode information

37
Q

What are the 3 ways to modulate information?

A 
amplitude modulation (AM)
frequency modulation (FM)
phase modulation (PM)
38
Q

What is a symbol?

A

+1 modifications to a carrier wave used to encode data

one bit defining two different symbols

39
Q

What is 2-bit amplitude modulation?

A

2 bits transmitted per symbol (4 levels defined as symbols)

40
Q

What is the data rate?

A

data rate = symbol rate * (#bits/symbol)

41
Q

What are codecs?

A

device or software converting analog signals into digital form and vice versa

42
Q

What is pulse code modulation?

A

converts analog to digital

sampling analog signal
measuring amplitude of each sample
encoding amplitude as binary data

43
Q

What is quantizing error?

A

difference between an original analog signal and approximated digital signal

44
Q

How can you reduce quantizing error?

A

sampling more frequently

using more levels of amplitude in encoding

CIS 3347 (5 decks)

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