This set of Wireless & Mobile Communications Multiple Choice Questions & Answers (MCQs) focuses on “MAC Management”.
1. Which of the following elements is mandatory for Wireless Local Area Network (WLAN) peer to peer mode configurations?
a) Cell stations
b) Multiport Repeater
c) Distributed Media Access Control protocol
d) Handoff
View Answer
Explanation: WLAN technology includes hub topology and peer to peer mode topology. Hub topology requires cell stations, multiport repeater and mobile station handoff. Peer to peer mode based systems does not require the elements of hub topology and purely rely on distributed Media Access Control protocol.
2. Which of the following is not a contention based protocol utilized in WLAN architecture?
a) Carrier Sense Multiple Access with Collision Detection (CSMA/ CD)
b) Carrier Sense Multiple Access (CSMA)
c) Aloha
d) Carrier Sense Multiple Access with Collision Avoidance (CSMA/ CA)
View Answer
Explanation: CSMA/CD is efficient only for wired applications, since it requires a medium between transmitter and receiver. Contention based protocol aims in providing efficient communication between multiple users without interference in wireless medium. But, in rare cases collisions are prone to occur. Few examples of contention based protocols include Aloha, CSMA, Ethernet, Multiple Access Collision Avoidance (MACA), CSMA/CA and Multiple Access with Collision Avoidance for Wireless (MACAW).
3. Collision avoidance in Media Access Control (MAC) protocol is capable of determining whether effective transmission of the signals occurs.
a) True
b) False
View Answer
Explanation: MAC protocols include Carrier Sense (CS), Carrier Detection (CD), Collision Avoidance (CA), and back off mechanisms. CS is capable of sensing effective transmission, whereas back off mechanism implies procedures to estimate contention and postponing transmissions. CD and CA are used for detecting and avoiding collisions respectively.
4. Which of the following Media Access Control (MAC) protocols provide maximum throughput per packet interval?
a) 0.01 persistent Carrier Sense Multiple Access (CSMA)
b) Non – persistent CSMA
c) 0.5 persistent CSMA
d) 1 – persistent CSMA
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Explanation: Persistent CSMA is an advanced version of CSMA which extensively operates in the MAC layer. In persistent CSMA protocols, whenever transmitting station is capable of sending frames, it senses busy channels, waits until the transmission ends and then transmits immediately. Compared with persistent and non- persistent versions of CSMA, 0.01 persistent CSMA provides increased throughput per packet interval.
5. Which of the following element is not present in Multiple Access with Collision Avoidance (MACA) protocol’s signaling packets?
a) Sender address
b) Receiver address
c) Information
d) Packet size
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Explanation: MACA utilizes shorter signaling packets to avoid collisions and each packet contains the address of the sender, receiver and packet size. During this transmission process, transmitter sends Request to Send (RTS) message to the receiver before it transmits the data packets. Once the receiver is ready for reception, it permits the transmitter to send message.
6. Which of the following access method is mandatory for MAC layer in IEEE 802.11?
a) Carrier Sense Multiple Access (CSMA)
b) Carrier Sense Multiple Access with Collision Detection (CSMA/CD)
c) Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA)
d) Persistent Carrier Sense Multiple Access
View Answer
Explanation: CSMA/CA, CSMA/CD and CSMA are the access methods utilized by the MAC layer of IEEE 802.11. Among these categories of access methods, CSMA/CA is a mandatory method deployed whereas the remaining methods are optional. This technique avoids collisions by exponential back-off mechanism and offers minimum distance between successive packets.
7. Which of the following elements is not a feature of MAC management technique?
a) Synchronization
b) Association
c) Re-association
d) Interoperability
View Answer
Explanation: MAC management techniques includes the following elements namely synchronization, association, re-association, power management and Management Information Base (MIB). Synchronization technique detects effectiveness of the connection between devices. Association and Re-association techniques manage the integration of the devices to a Local Area Network. Power management tracks the traffic measurements and MIB manages the signals for communication.
8. MAC layer is responsible for describing frame formats and encapsulating frames.
a) True
b) False
View Answer
Explanation: MAC layer provides an abstraction of physical layer and the remaining higher layers of Open System Interconnection (OSI) model. Additionally, it encapsulates multiple frames and describes frame formats for transferring information. It provides full duplex communication channel within multipoint network and uses several MAC protocols to prevent collisions.
9. Which frame is used to filter duplicate frames in the frame structure of MAC layer in IEEE 802.11?
a) Power management
b) Order
c) Duration
d) Sequence Control
View Answer
Explanation: Sequence control in MAC layer of WLAN is 16 bits long. It is further classified into 2 sub categories namely Sequence number and Fragment number. The 12 bit sequence number portion is used to filter repetitive frames by avoiding duplication of acknowledgement mechanism frames.
10. Which of the following access methods is used in the Distributed Coordinated function (DCF) layer of IEEE 802.11?
a) Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA)
b) Carrier Sense Multiple Access (CSMA)
c) Persistent Carrier Sense Multiple Access
d) Carrier Sense Multiple Access with Collision Detection (CSMA/CD)
View Answer
Explanation: MAC architecture of WLAN includes Point Co-ordination Function (PCF) and Distributed Co-ordination Function (DCF). The operation of PCF is similar to polling process where one station serves as a point coordinator (master). DCF is implemented in all stations and it uses CSMA/CA access method for packet transmission.
Sanfoundry Global Education & Learning Series – Wireless & Mobile Communications.
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