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CSIT127: Networks and Communications > part 1 > Flashcards

part 1 Flashcards

1
Q

data communication

A

Transfer of data from one device to another

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2
Q

5 Components of Data Communication

A
  1. Protocol for sender
  2. Sender
  3. Medium
  4. Protocol for Receiver
  5. Receiver
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3
Q

Types of Effectiveness Measures

A
  1. Bitrate/delay (how fast data is sent)

2. Accuracy (any corruption in received data)

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4
Q

computer network

A

Series of interfacing devices that communicate with one another through various transmission mediums

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5
Q

2 Types of Links

A
  1. Point-to-point: link interconnected to two devices and will only carry data between these devices
  2. Multipoint: link is shared between multiple devices and will only carry data between these devices
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6
Q

network topology

A

The way in which a network is laid out physically

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7
Q

4 Types of Topologies

A
  1. Star: every device connected to a hub
  2. Mesh: every device connected to every other device
  3. Bus: every device links to one cable
  4. Ring: devices connected to two devices, creating a ring
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8
Q

WAN

A

Wide Area Network:

- encompasses parts of states, multiple states, countries etc.

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9
Q

LAN

A

Local Area Network:

- small geographic area; spans a room/floor/building/campus

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10
Q

MAN

A

Metropolitan Area Network:

- serve an area of 1km-50km, approx. the size of a typical city

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11
Q

PAN

A

Personal Area Network:

- network of a few meters, between wireless devices i.e. PDAs, laptops, smartphones etc. (e.g. bluetooth)

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12
Q

Microcomputer-to-LAN (Network Layout)

A

Computer connects to LAN through network interface card (NIC) which allows for a connection to a hub-like device (switch)

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13
Q

LAN-to-LAN (Network Layout)

A

Switch can filter out frames and limit what each LAN can see and send to one another

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14
Q

LAN-to-WAN (Network Layout)

A

Interconnects a user on a LAN workstation to the internet

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15
Q

data

A

Tangible entities that convey meaning

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16
Q

signal

A

How we transfer data; intangible, used to encode and transmit data

** data must be converted to a signal before being transferred to different devices **

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17
Q

2 Types of Data

A
  1. Analog

2. Digital

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18
Q

analog data

A

Continuous waveform, can be at an infinite number of points between some given minimum and maximum values (e.g. human voice)

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19
Q

Advantages of Analog Data

A
  • infinite range of values/data
  • easy processing
  • density higher than digital
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20
Q

Disadvantages of Analog Data

A
  • harder to separate noise
  • more exact values but difficult to work with
  • more susceptible to noise
  • generation loss
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21
Q

digital data

A

Composed of discrete/fixed number of values, represented by binary 0s and 1s

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22
Q

Advantages of Digital Data

A
  • easier to separate original waveform from noise
  • travels faster over digital lines
  • can transfer more data than analog
23
Q

Disadvantages of Digital Data

A
  • finite range of values
  • need greater bandwith
  • systems and processing are more complex
24
Q

3 Components of Signals

A
  1. Phase: position of waveform relative to a given moment of time or relative to time zero
  2. Frequency: number of times a signal makes a complete cycle within a given time frame
  3. Amplitude: height of the wave above or below a given reference point
25
Q

modulation

A

Process of sending data over a signal by varying its amplitude, frequency, or phase

26
Q

baud rate

A

Number of times the signal changes per second

27
Q

5 Digital Encoding Schemes (Digital -> Digital)

A
  • NRZ-L: Nonreturn to zero-level
  • NRZ-I: Nonreturn to zero-inverted
  • Manchester
  • Differential Manchester
  • Bipolar AMI

** refer to images **

28
Q

Pulse Code Modulation (Analog -> Digital)

A
  • analog waveform is sampled at specific intervals and the “snapshots” are converted to binary values
  • when binary values are later converted to an analog signal, a waveform similar to the original results
  • more snapshots taken = better resolution
  • need to sample an input source at 2x the highest frequency to get a fairly accurate representation (i.e. at 4000 Hz = need 8000 samples)
29
Q

Delta Modulation (Analog -> Digital)

A

Analog waveform is tracked, using a binary 1 to represent a rise in voltage and a 0 to represent a drop

** 1 = rise, 0 = drop **

30
Q

Shift Keying Techniques (Digital -> Analog)

A
  1. Amplitude shift keying:
    - one amplitude encodes 0, another encodes 1
  2. Frequency shift keying
    - same as above but with frequency
  3. Phase shift keying
    - same as above but with phase
31
Q

Transmission Media Categories

A
  1. Cable (i.e. UTP, STP, coaxial)
    - inexpensive compared to other media
  2. Light (i.e. fiber optics)
    - enormous bandwith, low noise
  3. Wireless (i.e. radio, satellite, infrared)
    - faster and cheaper way to deploy service where there is no infrastructure/environment for cabling
32
Q

Twisted Pair Wires

A

Reduces crosstalk because wires cross each other at nearly perpendicular angles

33
Q

Advantages of Unshielded Twisted-Pair (UTP)

A
  • inexpensive compared to other media

- high availability

34
Q

Disadvantages of Unshielded Twisted-Pair (UTP)

A
  • limited frequency spectrum
  • limited/slow data rates
  • high error rate
  • chance for crosstalk if wires not aligned properly
35
Q

2 Types of Coaxial Cables

A
  1. Baseband: uses digital signaling which the cable carries only one channel of digital data
  2. Broadband: transmits analog signals and is capable of supporting multiple channels
36
Q

Advantages of Coaxial Cables

A
  • greater channel capacity
  • large bandwith supports high speed and multimedia services
  • lower error rates due to less distortion
  • greater spacing = reduced noise and crosstalk
37
Q

Disadvantages of Coaxial Cables

A
  • deployed in bus architecture which means shared bandwith and security risks
  • high installation costs in local environment
  • high costs for local moves, adds or changes
  • susceptible to damage from lightning strikes
38
Q

Fiber-optic Cable

A

Photo diode or laser generates pulses of light which travel down the fiber optic cable and are received by a photo receptor

39
Q

Advantages of Fiber-optic Cables

A
  • extremely high bandwith
  • not susceptible to electromagnetic impairments/interference
  • low bit rate error
  • secure detection
  • low in weight and mass
40
Q

Disadvantages of Fiber-optic Cables

A
  • susceptible to reflection (light bounces around in cable) and refraction (light passes out of core and into surrounding cladding)
  • high installation costs
  • vulnerable to physical damage and damage caused by wildlife and flora
41
Q

wireless signals

A

Wireless data signals travel on electromagnetic waves

42
Q

Infrared Light

A
  • easy to transmit information with light because computers use binary and light has two properties (on/off)
  • requires an LED to transmit the signal and a detector that receives the signal
  • send data by the intensity of the light wave
43
Q

Infrared Wireless Transmission Types

A
  • directed transmission

- diffused transmission

44
Q

Advantages of Infrared Light

A
  • does not interfere with other types of communication signals
  • not affected by other signals (except light)
  • does not penetrate walls (i.e. signals are kept in a room = more secure)
45
Q

Disadvantages of Infrared Light

A
  • lack of mobility
  • can only cover up to a range of 15 meters
  • must be indoors
  • slower speed of transmission
46
Q

Radio Waves

A
  • travels through space or air in electromagnetic waves
  • when electric current passes through wire, creates a magnetic field in the space around the wire
  • as magnetic field radiates/moves out, it creates radio waves
47
Q

Factors in Choosing Transmission Media

A
  • cost (i.e. initial cost, ROI)
  • speed (propagation, data transfer)
  • distance and expandability
  • environment (i.e. extreme conditions)
  • security
48
Q

multiplexing

A

Multiple signals being able to be transmitted at the same time to make transmissions more effective

49
Q

multiplexor

A

Accepts inputs and assigns frequencies to each device

50
Q

Frequency Division Multiplexing

A
  • assignment of non-overlapping frequency ranges to each “user” or signal on a medium
  • e.g. all signals are transmitted at the same time, each using different frequencies
  • corresponding multiplexor/demultiplexor is on the receiving end of the medium and separates signals

Examples: cable television, telephone systems, broadcast radio (think: entertainment)

51
Q

Time Division Multiplexing

A
  • sharing of the signal is accomplished by dividing available transmission time on a medium among users
52
Q

Synchronous Time Division Multiplexing

A
  • multiplexor accepts input from attached devices in a round-robin fashion and transmits the data in a never-ending pattern
  • if one device generates data faster than others, multiplexor samples data from that device more than the others
  • if device does not transfer data, multiplexor must still insert something into the stream
53
Q

Statistical Time Division Multiplexing

A
  • transmits data from active workstations only

- uses less resources than synchronous = more efficient

54
Q

Code Division Multiplexing

A
  • allows multiple devices to transmit on the same frequencies at the same time
  • assigns unique 64-bit code to each device
  • send 1 = sends that code, send 0 = sends inverse

** check example in notes **

CSIT127: Networks and Communications (4 decks)

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