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Kommunikasjon - Tjenester og nett > Chapter 7: Wireless and Mobile Networks > Flashcards

Chapter 7: Wireless and Mobile Networks Flashcards

1
Q

What are the two important challenges faced by wireless & mobile networks?

A

Wireless and mobility

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2
Q

Which element of a wireless network is described below?
Used to connect mobile(s) to base station, also used as a backbone link. Uses multiple access protocol coordinates for link access. Has various transmission rate and distances & frequency bands.

A

Wireless link

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3
Q

Which element of a wireless network is described below?
Runs applications. May be stationary (non-mobile) or mobile. E.g. laptop, smartphone, …

A

Wireless host

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4
Q

Which element of a wireless network is described below?
Typically connected to wires network and responsible for relay

A

Base station

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5
Q

Give the definition:
Sending packets between wired networks & wireless host(s) in the base station area

A

Relay

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6
Q

Which mode of a wireless network is this?
Base station connects mobiles into wired network

A

Infrastructure mode

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7
Q

What is the technique that a wireless network employs when a mobile changes base station providing connection into the wired network called?

A

Handoff

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8
Q

Which mode of a wireless network is this?
The mode where there are no base stations. Nodes can only transmit to other nodes within link coverage and nodes organize themselves into a network - route among themselves

A

Ad hoc mode

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9
Q

Which type of wireless network is described below?
Host connects to base station which connected to larger wired network.

A

Infrastructure mode with single-hop

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10
Q

Which type of wireless network is described below?
No base station & no connection to larger wired network

A

No infrastructure mode with single hop

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11
Q

Which type of wireless network is described below?
The host has to relay through several wireless nodes to connect to a larger network

A

Infrastructure mode with multiple hosts

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12
Q

Which type of wireless network is described below?
No base station & no connection to larger wired network. May have to relay to reach other / a given wireless node

A

No-infrastructure mode with multiple hosts

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13
Q

Which sort of link has the following characteristics?
Decreased signal strength
Interference from other sources
Multipath propagation

A

Wireless link

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14
Q

Give the definition:
Relative measure of the strength of a received signal & the noise (measured in dB)

A

Signal-to-Noise Ratio (SNR)

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15
Q

Is SNR larger or smaller when it’s easier to extract a signal from noise and the BER is lower?

A

Larger

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16
Q

Is the likelihood of noise overpowering a signal decreasing a result of increasing or decreasing SNR?

A

Increasing

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17
Q

Is the reduction of BER a result of increasing or decreasing SNR?

A

Increasing

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18
Q

Is a receiver being able to more accurately interpret the transmitted bits a result of increasing or decreasing SNR?

A

Increasing

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19
Q

For a given SNR, will a modulation technique with a higher bit transmission rate have a higher or lower BER?

A

Higher

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20
Q

Which problem with wireless networks is described below?
1. B and A hear each other
2. B and C hear each other
3. A and C can’t hear each other –> A and C are unaware of their interference at B

A

Hidden terminal problem

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21
Q

Which problem with wireless networks is described below?
1. B and A hear each other
2. B and C hear each other
3. A and C can’t hear each other interfering at B resulting in decreasing signal strength for A and C

A

Signal attenuation

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22
Q

What sort of CSMA do all IEEE 802.11 wireless LANs use for multiple access?

A

CSMA/CA

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23
Q

What two network versions do 802.11 wireless LANs have?

A

Base-station & ad hoc

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24
Q

The 802.11 LAN architecture consists of wireless hosts that communicate with…

A

Access Points / Base stations

25
Q

What part of the 802.11 LAN architecture contains the following in infrastructure mode:
- Wireless hosts
- Access Points
- Ad hoc mode: with hosts only

A

Basic Service Set (BSS)

26
Q

Give the definition:
Frames used in 802.11 LANs that include an AP’s SSID & MAC address

A

Beacon frames

27
Q

What sort of scanning by 802.11 is described below?
1. Beacon frames sent from APs
2. Association Request frame sent: H1 to selected AP
3. Association Response frame sent: selected AP to H1

A

Passive scanning

28
Q

What sort of scanning by 802.11 is described below?
1. Probe Request frame broadcast from H1
2. Probe Response frames sent from APs
3. Association Request frame sent: H1 to selected AP
4. Association Response frame sent from selected AP to H1

A

Active scanning

29
Q

Does 802.11 have collision detection?

30
Q

What 802.11 collision avoidance technique is described below?
1. Sender first transmits small Request-To-Send (RTS) packet to BS using CSMA
2. BS broadcasts Clear-To-Send (CTS) in response to RTS
3. CTS heard by all nodes
a) Sender transmits data frame
b) Other situations defer transmissions

A

RTS-CTS exchange

31
Q

What part of the 802.11 frame is described below?
MAC address of wireless host / AP to receive this frame

32
Q

What part of the 802.11 frame is described below?
MAC address of wireless host / AP transmitting this frame

33
Q

What part of the 802.11 frame is described below?
Duration of received transmission time

34
Q

What part of the 802.11 frame is described below?
Frame type

35
Q

What part of the 802.11 frame is described below?
Frame sequence number - used for reliable data transfer

A

Sequence control

36
Q

What part of the 802.11 frame is described below?
MAC address of router interface to which AP is attached

37
Q

What part of the 802.11 frame is described below?
Address used only in ad hoc mode

38
Q

What are the 2 advanced capabilities of 802.11?

A

Rate adaption & power management

39
Q

What element of the 4G LTE architecture is described below?
- 64 bit International Mobile Subscriber Identity IMSI) stored on Subscriber Identity Module (SIM) card
- User Equipment (UE) in LTE jargon

A

Mobile device

40
Q

What element of the 4G LTE architecture is described below?
- Stores info about mobile devices for which the HSS’s network is their “home network”
- Works with MME in device authentication

A

Home Subscriber Service (HSS)

41
Q

What element of the 4G LTE architecture is described below?
- Device authentication coordinated with mobile home network HSS
- Mobile device management - Tracking of device location
- Path (tunneling) setup from mobile device to P-GW

A

Mobile Management Entity (MME)

42
Q

What element of the 4G LTE architecture is described below?
- At “edge” of carrier’s network
- Manages wireless radio resources & mobile devices in its coverage area / “cell”
- Coordinates device authentication with other elements
- Similar to WiFi AP
- eNode-B in LTE jargon

A

Base station

43
Q

What element of the 4G LTE architecture is described below?
- Lies on data path to mobile / from Internet
- One of them is a gateway to mobile cellular network, looks like internet gateway router and provides NAT services
- Routers have an extensive use of tunneling

A

Serving Gateway (S-GW), PDN Gateway (P-GW)

44
Q

Is the data plane or the control plane in LTE described below?
New protocols for mobility management, security & authentication

A

Control plane

45
Q

Is the data plane or the control plane in LTE described below?
New protocols at link & physical layer. Extensive use of tunneling to facilitate mobility.

A

Data plane

46
Q

Which channel in the LTE radio access network is described below?
FDM, TDM within frequency channel

A

Downstream channel

47
Q

Which channel in the LTE radio access network is described below?
FDM, TDM similar to OFDM

A

Upstream channel

48
Q

Which LTE link layer protocol is described below?
Header compression & encryption

A

Packet Data Convergence

49
Q

Which LTE link layer protocol is described below?
Fragmentaton/reassembly & reliable data transfer

A

Radio Link Control (RLC) protocol

50
Q

Which LTE link layer protocol is described below?
Requesting & use of radio transmission slots

A

Medium Access Control (MAC)

51
Q

What sleep mode in an LTE mobile is described below?
After 100 ms of inactivity. Wake up periodically to check for downstream transmissions.

A

Light sleep

52
Q

What sleep mode in an LTE mobile is described below?
After 5 - 10 s of inactivity. Mobile may change cells while in this sleep - need to reestablish association

A

Deep sleep

53
Q

Which part of the global cellular network is described below?
Identifies and services info, while in home network & roaming

A

Home network HSS

54
Q

Which part of the global cellular network is described below?
Carriers interconnect with each other, and public internet at exchange points

55
Q

What property of 5G is described below?
- 2 frequency bands with mm wave frequencies. These frequencies enable much higher data rates over shorter distances.
- Not backwards compatible with 4G
- MIMO: multiple directional antenna

A

5G New Radio (NR)

56
Q

In comparison to 4G, does 5G have an increased or decreased peak bitrate?

57
Q

In comparison to 4G, does 5G have an increased or decreased latency?

58
Q

In comparison to 4G, does 5G have an increased or decreased traffic capacity?

Kommunikasjon - Tjenester og nett (9 decks)

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