Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Computer Networks > Wireless Networks > Flashcards

Wireless Networks Flashcards

1
Q

What are the wireless hosts in Wireless Network

A

laptop, smartphone etc.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the base station in Wireless Network

A

The base station is typically connected in a network, responsible for sending packets between wired network and wireless host in its area

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the wireless link in Wireless Network

A

typically used to connect mobile(s) to base station. multiple access protocol coordinates link access

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Is wireless link used as a backbone link?

A

Yes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the infrastructure mode in Wireless Network

A

base station connects mobiles into wired network
▪ handoff: mobile changes base station providing connection into wired network

base stations are connected to the infrastructure mode

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the ad hoc mode Wireless Network

A

no base stations, nodes can only transmit to other nodes within link coverage. nodes organize themselves into a network: route among themselves

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are the factors that make wireless link more difficult?

A
  1. decreased signal strength
  2. interference from other sources
  3. multipath propagation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is SNR? if SNR is large, what does it mean?

A

SNR: signal-to-noise ratio

• larger SNR – easier to extract signal from noise (a “good thing”)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Describe SNR vs BER tradeoffs

A

given physical layer: increase power -> increase SNR- >decrease BER (Bit Error Rate)
• given SNR: choose physical layer that meets BER requirement, giving highest throughput
• SNR may change with mobility: dynamically adapt physical layer (modulation technique, rate)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Describe Hidden Terminal Problem

A

▪ B, A hear each other
▪ B, C hear each other
▪ A, C can not hear each other means A, C unaware of their interference at B

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Describe Signal Attenuation

A

▪ B, A hear each other
▪ B, C hear each other
▪ A, C can not hear each other interfering at B

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Tell encoded signal formula in CDMA

A

encoded signal = (original data) X (chipping

sequence)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Direct Sequence Spread Spectrum is in which protocol?

A

802.11b

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Which protocol has 2.4-5Ghz, and up to 11Mbps?

A

802.11b

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Which protocol has 2.4-5Ghz, and up to 200Mbps?

A

802.11n

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Which protocol has 5-6Ghz, and up to 54Mbps?

A

802.11a

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Which protocol has 2.4-5Ghz, and up to 54Mbps?

A

802.11g

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

All protocols use ___ for multiple access

A

CSMA/CA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Base station is present in what protocol?

How about ad-hock networks?

A

All

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Is base station an access point in IEE 802.11 protocols?

A

Yes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is included in BSS(Basic Service Set)

A

Wireless hosts, access point, ad hoc mode: hosts only

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

802.11b is divided into how much channels?

A

11

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is the name for access point identifiers?

A

SSID

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Apart from SSID, what else should access points have according to the protocol

A

MAC Address

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
How does CSMA/CA avoid collisions?
Prepared RTS(ready to send) message, that includes destination address and duration of message. Tells everyone to backoff. After that Destination sends CTS(clear to send) message. Other stations set their Network Allocation vector and wait for that duration
26
Can CSMA/CA detect collisions?
No
27
What are the two ways to scan the channels?
Passive/acting scanning.
28
Explain passive scanning
1. beacon frames sent from AP 2. request frame from H1 to AP sent 3. response from AP to H1 sent
29
Explain active scanning
1. probe request frame broadcast from h1 2. probe response sent from APs 3. associated request frame from h1 to selected AP 4. associated response from selected AP to h1
30
Why there is no collision detection in IEEE 802.11?
Because of the weak signals from the wireless links
31
List DCF components
Carrier sense, interframe spaces, backoff timer, frame transmission
32
What kind of Carrier Sense types exist? Describe each of them
Physical and Virtual Physical Carrier Sense uses Clear Channel Assessments stations check wireless medium to detect use. Two types: Carrier Sense(CS): detects signal strength Energy Detection(ED): measures RF energy in the channel Virtual Carrier Sense has NAV timer to calculate transmission opportunity time
33
What kind of Backoff Timer types exist? Describe each of them
Contention Window, Random Backoff Contention Window includes a range of numbers from which stations randomly select backoff value Random Backoff: number randomly chosen from Contention Window.
34
What interframe space Highest Priority Frames use? What interframe space Medium Priority Frames use? What interframe space Asynchronous Data Frames use?
1. short IFS, 2. Point Coordination Function IFS, 3. Distributed Coordination Function IFS
35
Arbitration Interframe Spaces are used by?
Used by Quality of Service stations
36
List and describe components of cellular network architecture?
cell: covers geographical region; base station (BS) analogous to 802.11 AP. mobile users attach to network through BS. air-interface: physical and link layer protocol between mobile and BS
37
Mobile Switching Center responsibility is?
❖ to connect cells to wired tel. net. ❖ to manage call setup ❖ to handle mobility
38
What are the two ways for sharing mobile radio spectrum?
1. FDMA/TDMA | 2. CDMA
39
What is 1G?
First generation. Supports voice calls only. Uses FDMA. analog modulation
40
What is 2G?
Second. Supports voice and data services. Uses TDMA and Digital Modulation
41
Mobile station components?
Mobile equipment and SIM
42
Base stations subsystem components?
1. Base Tranceiver Station: * sends & receives signals from MS * uses multiplexing, encryption, modulation 2. Base Station Controller * controls BTS * allocates radio channels * handovers from one BTS to another
43
Network switching subsystem components?
MSC(Mobile switching Center): * heart of GSM * manages mobile services
44
Key insight of 3G?
New cellular data network operates in parallel with existing cellular voice network. voice network unchanged, data network operates in parallel
45
What is the difference between LTE and 3G?
1. IP packets tunneled (through core IP network) from base station to gateway 2. no separation between voice and data – all traffic carried over IP core to gateway
46
What are the 5 5G Technologies?
Millimeter Waves, Small Cells, Massive MIMO, Beamforming, Full duplex
47
Explain Millimeter Waves
Expanding the frequency range. | Has problem of being absorbed by nature or not being able to travel the obstacles: solved by small cells
48
Explain small cells
Put behind the obstacles so that the signal does not dissapear
49
Explain massive MIMO
MIMO: Massive Input Massive Output. 7 times more ports increase the capacity of networks. Problem: massive interference. Solved by beamforming
50
Explain beamforming
Serves as a traffic light for signals. Solved the interference
51
Explain full duplex
Allows the signals to be sent in both ways at once.
52
ZigBee is?
Is a wireless technology standard that finds a set of communication protocols for short range communications
53
Zigbee is a standard that addresses the need of _____ implementation of ___ with ___ data rate and ___ range wireless communication
very low cost; low-power devices; low; short
54
List ZigBee applications?
1. Home automation 2. Medical data collection 3. Industrial Control Systems
55
Purpose of ZigBee?
1. Collect Information | 2. Perform Control Tasks inside a building
56
Give example where ZigBee can be applied and Bluetooth or Wifi cannot?
Remote Monitoring System can be applied by Zigbee. Wi-Fi too powerful Bluetooth has max 7 devices
57
List three frequency bands assigned to ZigBee
Europe: 868Mhz US and Australia: 915 Mhz, Channels 1-10 Across the world: 2.6Ghz, Channels 11-26
58
List Zigbee devices
Coordinators, Routers, End Devices
59
Explain Coordinator in Zigbee
Coordinator: most capable device, root of the network, only one Can perform: channel selection, assign ID to network, allocates unique address to device, initiates and transfers messages
60
Explain Router in Zigbee
Routers: intermediate node between coordinator and the end devices. Route traffic between nodes. Receives and store messages intended for their messages, allow other routers and end devices to join the network
61
Explain End devices in Zigbee
End Devices: contains enough info to talk to parent, they may sleep(suitable for battery devices), all traffic to end devices is routed to its parent. Responsible for requesting any pending messages from parent
62
Which topologies are used in Zigbee
Mesh, star
63
Describe channel accessing in Zigbee
Two types: contention-free and contention based methods. In first, coordinator dedicates specific timeslot to each devices(guaranteed time slot). In second: no synchronization, CSMA/CA. Step by step: go to receive mode, check for signals, transmit if channel is clear. else backoff

Computer Networks (6 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions