Wireless Technologies Questions and Answers

Q: For the IEEE 802.11 MAC protocol for wireless communication, which of the following statements is/are TRUE?I. At least three non-overlapping channels are available for transmissions.II. The RTS-CTS mechanism is used for collision detection.III. Unicast frames are ACKed.

The true statements are I and III only.I is true: in the 2.4 GHz band, channels 1, 6 and 11 do not overlap, so at least three non-overlapping channels are available (and many more at 5 GHz).III is true: 802.11 uses a stop-and-wait acknowledgement at the MAC layer, so every unicast data frame received correctly is ACKed; broadcast frames are not.II is false: a wireless station cannot reliably detect collisions while transmitting, so 802.11 uses CSMA/CA, collision avoidance. The RTS-CTS exchange reserves the medium to avoid collisions, notably from hidden terminals; it does not detect them. That rules out every option containing II.

Q: In wireless networks CDPD stands for ................. .

CDPD stands for Cellular Digital Packet Data.CDPD was a wireless data service that sent digital packets over idle channels of the AMPS analogue cellular network, letting mobile users connect to IP networks.The other expansions are invented; in particular CDPD involves no collision detection, and its last word is 'Data', not 'Distribution'.

Q: Bluetooth is an example of :

Bluetooth is an example of a personal area network.A personal area network connects devices around one person, over distances of roughly 10 m: a phone with headphones, a watch, a keyboard or a car system. Bluetooth (originally IEEE 802.15.1) is the best-known wireless PAN technology, operating in the 2.4 GHz band.A local area network covers a building or campus, as Wi-Fi and Ethernet do. A wide area network spans cities or countries. A virtual private network is a secure tunnel over another network such as the internet, not a type of short-range link.

Q: Which of the following is most commonly used IOT standards for Medium Access Control (MAC) ?

The most commonly used IoT MAC standard is IEEE 802.15.4.IEEE 802.15.4 defines the physical and medium access control layers for low-rate, low-power wireless personal area networks. It is the foundation of Zigbee, 6LoWPAN, Thread and WirelessHART, which makes it the most widely used MAC standard in IoT sensor networks.IEEE 802.11ah (Wi-Fi HaLow) is a newer, sub-1 GHz Wi-Fi standard for IoT with far less deployment. IEEE 2413 is an architectural framework for IoT, not a MAC standard. IEEE 11073 is a family of standards for communication between personal health devices.

Q: In cellular networks, what is the primary reason for using hexagonal cells instead of circular cells ?

Hexagons are used because they give uniform coverage without gaps or overlaps.A base station radiates roughly equally in all directions, so its ideal coverage area is a circle. But circles cannot tile a plane: placed edge to edge they leave gaps, and overlapped to close the gaps they waste area. Of the shapes that do tile the plane (triangle, square, hexagon), the hexagon is closest to a circle, so it covers the most area per cell for a given maximum distance from the centre, with no gaps and no overlaps. That makes cell planning and frequency reuse easy to model.The shape is a planning model, so it has no effect on antenna gain or multi-antenna support, and option B describes the very problem hexagons are used to avoid.

Q: Handoff latency is MOST critically influenced by which factor in mobile networks ?

Handoff latency is most critically influenced by the switching center processing speed.Handoff latency is the delay between deciding that a call must move to a new cell and completing the move. In that interval the mobile switching centre must reserve a channel in the new cell, exchange signalling with both base stations and switch the call path, so the time it takes to process these steps sets the latency.Signal strength decides when a handoff is triggered, not how long the handoff takes once started. Battery level does not enter the handoff procedure, and the modulation technique affects data rate and robustness on the air interface rather than the switching delay.

Q: Increasing base station density does NOT always prevent handoff failure because

The reason is that frequent handoffs overload the control channel.Adding base stations makes cells smaller. A moving user then crosses cell boundaries more often, and every crossing needs a handoff, with measurement reports, channel allocation and signalling between the mobile, the base stations and the switching centre. If the handoff rate rises faster than the control channels and switch can handle, requests are delayed or dropped and calls fail, so denser cells do not always help.More towers do not reduce signal power; nearby users actually receive stronger signals. Denser deployment makes cells smaller, not larger, and it raises total capacity through frequency reuse rather than lowering it.

Q: Mobile IP uses which mechanism to maintain session continuity ?

Mobile IP maintains session continuity through dynamic tunneling.A mobile node keeps its permanent home address, so connections bound to that address never need to change. When it moves to a foreign network it obtains a care-of address and registers it with its home agent. The home agent intercepts packets sent to the home address and tunnels them, by IP-in-IP encapsulation, to the current care-of address, where they are unwrapped and delivered. Each move simply changes the tunnel's endpoint.Packet filtering is a firewall function, and proxy switching and route compression are not part of Mobile IP.

Q: In LTE, handover failures mainly occur due to which reason ?

LTE handover failures mainly come from incorrect RSRP/RSRQ threshold configuration.In LTE, the handset measures the RSRP (Reference Signal Received Power) and RSRQ (Reference Signal Received Quality) of its serving and neighbouring cells and reports when configured events occur, for example a neighbour becoming better than the serving cell by an offset. Badly set thresholds, hysteresis and time-to-trigger values make handovers happen too late (radio link failure), too early, or back and forth (ping-pong).TDD frame synchronisation and encryption keys are handled by the network as part of the procedure. 'AP association' is Wi-Fi terminology, not LTE.

Which of the given options best describes the truthfulness of the following statements? i) Service Set Identification (SSID) is human readable text string with a maximum length of 2000 bytes. ii) Service Set Identification (SSID) acts as a single shared identifier between the access points and clients.

A.i-True, ii-True
B.i-False, ii-True
C.i-True, ii-False
D.i-False, ii-False

Exam Year(s)

DSSSB TGT - 2023,

Answer: B

Statement i is false and statement ii is true. An SSID is a human-readable text string, but its maximum length is 32 bytes, not 2000 bytes. The SSID acts as a single shared identifier between the access points and the clients of a wireless network. So the second option, i-False and ii-True, is correct, and the options that call i true are wrong. The 32-byte limit is the same figure that is given for the SSID in the standard for wireless networks.

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For the IEEE 802.11 MAC protocol for wireless communication, which of the following statements is/are TRUE?

I. At least three non-overlapping channels are available for transmissions.
II. The RTS-CTS mechanism is used for collision detection.
III. Unicast frames are ACKed.

A.All I, II, and III
B.I and III only
C.II and III only
D.II only

Exam Year(s)

GATE CS - 2016,

Answer: B

The true statements are I and III only.

I is true: in the 2.4 GHz band, channels 1, 6 and 11 do not overlap, so at least three non-overlapping channels are available (and many more at 5 GHz).

III is true: 802.11 uses a stop-and-wait acknowledgement at the MAC layer, so every unicast data frame received correctly is ACKed; broadcast frames are not.

II is false: a wireless station cannot reliably detect collisions while transmitting, so 802.11 uses CSMA/CA, collision avoidance. The RTS-CTS exchange reserves the medium to avoid collisions, notably from hidden terminals; it does not detect them. That rules out every option containing II.

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In wireless networks CDPD stands for ................. .

A.Carrier Data Packet Data
B.Collision Detection in Packet Data
C.Cellular Digital Packet Distribution
D.Cellular Digital Packet Data

Exam Year(s)

MH SET - 2024, SET Exam - 2024,

Answer: D

CDPD stands for Cellular Digital Packet Data.

CDPD was a wireless data service that sent digital packets over idle channels of the AMPS analogue cellular network, letting mobile users connect to IP networks.

The other expansions are invented; in particular CDPD involves no collision detection, and its last word is 'Data', not 'Distribution'.

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Bluetooth is an example of :

A.Wide area network
B.Virtual private network
C.Local area network
D.Personal area network

Exam Year(s)

MH SET - 2025, SET Exam - 2025,

Answer: D

Bluetooth is an example of a personal area network.

A personal area network connects devices around one person, over distances of roughly 10 m: a phone with headphones, a watch, a keyboard or a car system. Bluetooth (originally IEEE 802.15.1) is the best-known wireless PAN technology, operating in the 2.4 GHz band.

A local area network covers a building or campus, as Wi-Fi and Ethernet do. A wide area network spans cities or countries. A virtual private network is a secure tunnel over another network such as the internet, not a type of short-range link.

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Which of the following is most commonly used IOT standards for Medium Access Control (MAC) ?

A.IEEE802.15.4
B.IEEE802.11ah
C.IEEE 2413
D.IEEE11073

Exam Year(s)

MH SET - 2025, SET Exam - 2025,

Answer: A

The most commonly used IoT MAC standard is IEEE 802.15.4.

IEEE 802.15.4 defines the physical and medium access control layers for low-rate, low-power wireless personal area networks. It is the foundation of Zigbee, 6LoWPAN, Thread and WirelessHART, which makes it the most widely used MAC standard in IoT sensor networks.

IEEE 802.11ah (Wi-Fi HaLow) is a newer, sub-1 GHz Wi-Fi standard for IoT with far less deployment. IEEE 2413 is an architectural framework for IoT, not a MAC standard. IEEE 11073 is a family of standards for communication between personal health devices.

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In cellular networks, what is the primary reason for using hexagonal cells instead of circular cells ?

A.Higher antenna gain
B.Easy mathematical modeling of overlapping circles
C.Uniform coverage without gaps or overlaps
D.Support for multi-antenna base stations

Exam Year(s)

Tripura Public Service Commission - 2026,

Answer: C

Hexagons are used because they give uniform coverage without gaps or overlaps.

A base station radiates roughly equally in all directions, so its ideal coverage area is a circle. But circles cannot tile a plane: placed edge to edge they leave gaps, and overlapped to close the gaps they waste area. Of the shapes that do tile the plane (triangle, square, hexagon), the hexagon is closest to a circle, so it covers the most area per cell for a given maximum distance from the centre, with no gaps and no overlaps. That makes cell planning and frequency reuse easy to model.

The shape is a planning model, so it has no effect on antenna gain or multi-antenna support, and option B describes the very problem hexagons are used to avoid.

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Handoff latency is MOST critically influenced by which factor in mobile networks ?

A.Signal strength between mobile and base station
B.Switching center processing speed
C.Mobile device battery level
D.Modulation technique

Exam Year(s)

Tripura Public Service Commission - 2026,

Answer: B

Handoff latency is most critically influenced by the switching center processing speed.

Handoff latency is the delay between deciding that a call must move to a new cell and completing the move. In that interval the mobile switching centre must reserve a channel in the new cell, exchange signalling with both base stations and switch the call path, so the time it takes to process these steps sets the latency.

Signal strength decides when a handoff is triggered, not how long the handoff takes once started. Battery level does not enter the handoff procedure, and the modulation technique affects data rate and robustness on the air interface rather than the switching delay.

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Increasing base station density does NOT always prevent handoff failure because

A.Frequent handoffs overload the control channel
B.More towers reduce signal power
C.Larger cells increase fading
D.Cell capacity decreases

Exam Year(s)

Tripura Public Service Commission - 2026,

Answer: A

The reason is that frequent handoffs overload the control channel.

Adding base stations makes cells smaller. A moving user then crosses cell boundaries more often, and every crossing needs a handoff, with measurement reports, channel allocation and signalling between the mobile, the base stations and the switching centre. If the handoff rate rises faster than the control channels and switch can handle, requests are delayed or dropped and calls fail, so denser cells do not always help.

More towers do not reduce signal power; nearby users actually receive stronger signals. Denser deployment makes cells smaller, not larger, and it raises total capacity through frequency reuse rather than lowering it.

Discuss in Forum

Mobile IP uses which mechanism to maintain session continuity ?

A.Packet filtering
B.Dynamic tunneling
C.Proxy switching
D.Route compression

Exam Year(s)

Tripura Public Service Commission - 2026,

Answer: B

Mobile IP maintains session continuity through dynamic tunneling.

A mobile node keeps its permanent home address, so connections bound to that address never need to change. When it moves to a foreign network it obtains a care-of address and registers it with its home agent. The home agent intercepts packets sent to the home address and tunnels them, by IP-in-IP encapsulation, to the current care-of address, where they are unwrapped and delivered. Each move simply changes the tunnel's endpoint.

Packet filtering is a firewall function, and proxy switching and route compression are not part of Mobile IP.

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10.

In LTE, handover failures mainly occur due to which reason ?

A.Incorrect RSRP/RSRQ threshold configuration
B.Lack of synchronization in TDD frames
C.Missing encryption keys
D.Poor AP association protocol

Exam Year(s)

Tripura Public Service Commission - 2026,

Answer: A

LTE handover failures mainly come from incorrect RSRP/RSRQ threshold configuration.

In LTE, the handset measures the RSRP (Reference Signal Received Power) and RSRQ (Reference Signal Received Quality) of its serving and neighbouring cells and reports when configured events occur, for example a neighbour becoming better than the serving cell by an offset. Badly set thresholds, hysteresis and time-to-trigger values make handovers happen too late (radio link failure), too early, or back and forth (ping-pong).

TDD frame synchronisation and encryption keys are handled by the network as part of the procedure. 'AP association' is Wi-Fi terminology, not LTE.

Discuss in Forum

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