part 1 Flashcards
(54 cards)
1
Q
data communication
A
Transfer of data from one device to another
2
Q
5 Components of Data Communication
A
- Protocol for sender
- Sender
- Medium
- Protocol for Receiver
- Receiver
3
Q
Types of Effectiveness Measures
A
- Bitrate/delay (how fast data is sent)
2. Accuracy (any corruption in received data)
4
Q
computer network
A
Series of interfacing devices that communicate with one another through various transmission mediums
5
Q
2 Types of Links
A
- Point-to-point: link interconnected to two devices and will only carry data between these devices
- Multipoint: link is shared between multiple devices and will only carry data between these devices
6
Q
network topology
A
The way in which a network is laid out physically
7
Q
4 Types of Topologies
A
- Star: every device connected to a hub
- Mesh: every device connected to every other device
- Bus: every device links to one cable
- Ring: devices connected to two devices, creating a ring
8
Q
WAN
A
Wide Area Network:
- encompasses parts of states, multiple states, countries etc.
9
Q
LAN
A
Local Area Network:
- small geographic area; spans a room/floor/building/campus
10
Q
MAN
A
Metropolitan Area Network:
- serve an area of 1km-50km, approx. the size of a typical city
11
Q
PAN
A
Personal Area Network:
- network of a few meters, between wireless devices i.e. PDAs, laptops, smartphones etc. (e.g. bluetooth)
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)
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
14
Q
LAN-to-WAN (Network Layout)
A
Interconnects a user on a LAN workstation to the internet
15
Q
data
A
Tangible entities that convey meaning
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 **
17
Q
2 Types of Data
A
- Analog
2. Digital
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)
19
Q
Advantages of Analog Data
A
- infinite range of values/data
- easy processing
- density higher than digital
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
21
Q
digital data
A
Composed of discrete/fixed number of values, represented by binary 0s and 1s
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
- Phase: position of waveform relative to a given moment of time or relative to time zero
- Frequency: number of times a signal makes a complete cycle within a given time frame
- Amplitude: height of the wave above or below a given reference point
25
modulation
Process of sending data over a signal by varying its amplitude, frequency, or phase
26
baud rate
Number of times the signal changes per second
27
5 Digital Encoding Schemes (Digital -> Digital)
- NRZ-L: Nonreturn to zero-level
- NRZ-I: Nonreturn to zero-inverted
- Manchester
- Differential Manchester
- Bipolar AMI
** refer to images **
28
Pulse Code Modulation (Analog -> Digital)
- 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
Delta Modulation (Analog -> Digital)
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
Shift Keying Techniques (Digital -> Analog)
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
Transmission Media Categories
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
Twisted Pair Wires
Reduces crosstalk because wires cross each other at nearly perpendicular angles
33
Advantages of Unshielded Twisted-Pair (UTP)
- inexpensive compared to other media
| - high availability
34
Disadvantages of Unshielded Twisted-Pair (UTP)
- limited frequency spectrum
- limited/slow data rates
- high error rate
- chance for crosstalk if wires not aligned properly
35
2 Types of Coaxial Cables
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
Advantages of Coaxial Cables
- 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
Disadvantages of Coaxial Cables
- 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
Fiber-optic Cable
Photo diode or laser generates pulses of light which travel down the fiber optic cable and are received by a photo receptor
39
Advantages of Fiber-optic Cables
- extremely high bandwith
- not susceptible to electromagnetic impairments/interference
- low bit rate error
- secure detection
- low in weight and mass
40
Disadvantages of Fiber-optic Cables
- 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
wireless signals
Wireless data signals travel on electromagnetic waves
42
Infrared Light
- 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
Infrared Wireless Transmission Types
- directed transmission
| - diffused transmission
44
Advantages of Infrared Light
- 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
Disadvantages of Infrared Light
- lack of mobility
- can only cover up to a range of 15 meters
- must be indoors
- slower speed of transmission
46
Radio Waves
- 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
Factors in Choosing Transmission Media
- cost (i.e. initial cost, ROI)
- speed (propagation, data transfer)
- distance and expandability
- environment (i.e. extreme conditions)
- security
48
multiplexing
Multiple signals being able to be transmitted at the same time to make transmissions more effective
49
multiplexor
Accepts inputs and assigns frequencies to each device
50
Frequency Division Multiplexing
- 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
Time Division Multiplexing
- sharing of the signal is accomplished by dividing available transmission time on a medium among users
52
Synchronous Time Division Multiplexing
- 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
Statistical Time Division Multiplexing
- transmits data from active workstations only
| - uses less resources than synchronous = more efficient
54
Code Division Multiplexing
- 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 **
