NTT Final Exam Questions & Answers
2024/2025
17.2 - List and briefly define key requirements for wireless LANs. - ANSWERSThroughput: The medium
access control protocol should make as efficient use as possible of the wireless medium to maximize
capacity. Number of nodes: Wireless LANs may need to support hundreds of nodes across multiple cells.
Connection to backbone LAN: In most cases, interconnection with stations on a wired backbone LAN is
required. For infrastructure wireless LANs, this is easily accomplished through the use of control modules
that connect to both types of LANs. There may also need to be accommodation for mobile users and ad
hoc wireless networks. Service area: A typical coverage area for a wireless LAN has a diameter of 100 to
300 m. Battery power consumption: Mobile workers use battery-powered workstations that need to
have a long battery life when used with wireless adapters. This suggests that a MAC protocol that
requires mobile nodes to monitor access points constantly or engage in frequent handshakes with a base
station is inappropriate. Typical wireless LAN implementations have features to reduce power
consumption while not using the network, such as a sleep mode. Transmission robustness and security:
Unless properly designed, a wireless LAN may be interference prone and easily eavesdropped. The
design of a wireless LAN must permit reliable transmission even in a noisy environment and should
provide some level of security from eavesdropping. Collocated network operation: As wireless LANs
become more popular, it is quite likely for two or more wireless LANs to operate in the same area or in
some area where interference between the LANs is possible. Such interference may thwart the normal
operation of a MAC algorithm and may allow unauthorized access to a particular LAN. License-free
operation: Users would prefer to buy and operate wireless LAN products without having to secure a
license for the frequency band us
17.5 - Is a distribution system a wireless network? - ANSWERSIt may or may not be.
17.10 - How is the concept of an association related to that of mobility? - ANSWERSMobility refers to the
types of physical transitions that can be made by a mobile node within an 802.11 environment (no
transition, movement from one BSS to another within an ESS, movement from one ESS to another).
Association is a service that allows a mobile node that has made a transition to identify itself to the AP
within a BSS so that the node can participate in data exchanges with other mobile nodes.
17.6 - List and briefly define three transmission techniques for infrared LANs. - ANSWERSThe transmitted
signal can be focused and aimed (as in a remote TV control); it can be radiated omnidirectionally; or it
can be reflected from a light-colored ceiling.
2024/2025
17.2 - List and briefly define key requirements for wireless LANs. - ANSWERSThroughput: The medium
access control protocol should make as efficient use as possible of the wireless medium to maximize
capacity. Number of nodes: Wireless LANs may need to support hundreds of nodes across multiple cells.
Connection to backbone LAN: In most cases, interconnection with stations on a wired backbone LAN is
required. For infrastructure wireless LANs, this is easily accomplished through the use of control modules
that connect to both types of LANs. There may also need to be accommodation for mobile users and ad
hoc wireless networks. Service area: A typical coverage area for a wireless LAN has a diameter of 100 to
300 m. Battery power consumption: Mobile workers use battery-powered workstations that need to
have a long battery life when used with wireless adapters. This suggests that a MAC protocol that
requires mobile nodes to monitor access points constantly or engage in frequent handshakes with a base
station is inappropriate. Typical wireless LAN implementations have features to reduce power
consumption while not using the network, such as a sleep mode. Transmission robustness and security:
Unless properly designed, a wireless LAN may be interference prone and easily eavesdropped. The
design of a wireless LAN must permit reliable transmission even in a noisy environment and should
provide some level of security from eavesdropping. Collocated network operation: As wireless LANs
become more popular, it is quite likely for two or more wireless LANs to operate in the same area or in
some area where interference between the LANs is possible. Such interference may thwart the normal
operation of a MAC algorithm and may allow unauthorized access to a particular LAN. License-free
operation: Users would prefer to buy and operate wireless LAN products without having to secure a
license for the frequency band us
17.5 - Is a distribution system a wireless network? - ANSWERSIt may or may not be.
17.10 - How is the concept of an association related to that of mobility? - ANSWERSMobility refers to the
types of physical transitions that can be made by a mobile node within an 802.11 environment (no
transition, movement from one BSS to another within an ESS, movement from one ESS to another).
Association is a service that allows a mobile node that has made a transition to identify itself to the AP
within a BSS so that the node can participate in data exchanges with other mobile nodes.
17.6 - List and briefly define three transmission techniques for infrared LANs. - ANSWERSThe transmitted
signal can be focused and aimed (as in a remote TV control); it can be radiated omnidirectionally; or it
can be reflected from a light-colored ceiling.
