Wireless and Mobile Networks Chapter 6 Quiz

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Questions and Answers

In the context of 802.11, what does CSMA stand for?

Carrier Sense Multiple Access

What is the main goal of the 802.11 CSMA/CA protocol?

To avoid collisions

What type of frame does the base station transmit in response to a small request-to-send (RTS) packet from a sender in the 802.11 protocol?

Clear-to-Send (CTS)

What does the duration field in an 802.11 frame represent?

Reserved transmission time (RTS/CTS) Signup and view all the answers

In the 802.11 protocol, which MAC address is used only in ad hoc mode?

Address 4 Signup and view all the answers

What is the main purpose of rate adaptation in the 802.11 protocol?

To dynamically change transmission rate as mobile moves Signup and view all the answers

What information does the beacon frame contain in 802.11 power management?

List of mobiles with frames waiting to be sent Signup and view all the answers

What is the primary purpose of 802.15 personal area network (PAN)?

To replace cables for devices like mouse and keyboard Signup and view all the answers

In a wireless network infrastructure mode, how are mobiles connected to the wired network?

Base station connects mobiles to the wired network Signup and view all the answers

What is the main characteristic of wireless network ad hoc mode?

Nodes organize themselves into a network and relay among themselves Signup and view all the answers

What is the purpose of Code Division Multiple Access (CDMA) in wireless networks?

To assign unique codes to each user for transmission Signup and view all the answers

What is the unlicensed spectrum range for IEEE 802.11 wireless LAN?

2.4-5 GHz Signup and view all the answers

How do hosts connect in the 802.11 LAN architecture infrastructure mode?

Each Basic Service Set (BSS) contains wireless hosts and an Access Point (AP) Signup and view all the answers

What is the function of passive and active scanning methods in 802.11 networks?

For joining an 802.11 network Signup and view all the answers

What is the main purpose of handoff in a wireless network infrastructure mode?

To allow mobile devices to change base stations and maintain connection Signup and view all the answers

What is the primary issue caused by the hidden terminal problem in wireless networks?

Nodes cannot hear each other causing interference Signup and view all the answers

What is the primary feature of IEEE 802.11 wireless LAN architecture?

Base station and wireless hosts communicate within a Basic Service Set (BSS) Signup and view all the answers

What is the key function of CSMA/CA in IEEE 802.11 wireless LAN?

For multiple access in a wireless LAN environment Signup and view all the answers

What is the distinguishing feature of multiple hop networks in wireless taxonomy?

Hosts may have to relay through several wireless nodes to connect to larger Internet Signup and view all the answers

What is a significant trend in wireless networks?

The number of wireless phone subscribers now exceeds the number of wired phone subscribers. Signup and view all the answers

Which element is responsible for sending packets between the wired network and wireless hosts in its 'area'?

Base station Signup and view all the answers

What is the main function of a base station in a wireless network?

Sending packets between the wired network and wireless hosts Signup and view all the answers

What do wireless links typically connect?

Mobiles to base stations Signup and view all the answers

What does the term 'wireless does not always mean mobility' imply?

Not all wireless devices are mobile Signup and view all the answers

What is the data rate for 802.11 wireless links?

54 Mbps Signup and view all the answers

What does a wireless host refer to in a wireless network?

Device like a laptop or smartphone Signup and view all the answers

What is the main challenge in handling the mobile user in wireless networks?

Handling the change in point of attachment to the network Signup and view all the answers

What is an important role of the network infrastructure in a wireless network?

Relaying data within the wireless network Signup and view all the answers

Study Notes

The text discusses various elements of wireless and mobile networks, including infrastructure and ad hoc modes, single and multiple hop networks, and wireless link characteristics.
Wireless network infrastructure mode:
- Base station connects mobiles to wired network.
- Handoff allows mobile devices to change base stations and maintain connection.
Wireless network ad hoc mode:
- No base stations, nodes only transmit to other nodes within link coverage.
- Nodes organize themselves into a network and route among themselves.
Wireless network taxonomy:
- Single hop infrastructure networks: APs connect hosts to larger Internet.
- Multiple hop networks: hosts may have to relay through several wireless nodes to connect to larger Internet.
Wireless network characteristics:
- Decreased signal strength due to path loss.
- Interference from other sources and multipath propagation.
- Hidden terminal problem: B, A and B, C cannot hear each other, causing interference.
Code Division Multiple Access (CDMA):
- Unique codes assigned to each user.
- Multiple users can transmit simultaneously with minimal interference.
IEEE 802.11 wireless LAN:
- 2.4-5 GHz unlicensed spectrum.
- Up to 54 Mbps in 802.11a, 54 Mbps in 802.11g, up to 200 Mbps in 802.11n.
- All versions use CSMA/CA for multiple access.
802.11 LAN architecture:
- Base station (access point) and wireless hosts communicate.
- In infrastructure mode, each BSS contains wireless hosts and an AP.
- Hosts must associate with an AP and perform authentication.
802.11: Channels, association:
- 11 channels at different frequencies for 802.11b.
- Hosts must associate with an AP and perform authentication.
Passive and active scanning methods for joining an 802.11 network.