IEEE 802.11 MCQ Quiz in मराठी - Objective Question with Answer for IEEE 802.11 - मोफत PDF डाउनलोड करा

The correct answer is option 4.

Concept:

   802.11a is an IEEE standard for transmitting data over a wireless network. It uses a 5 GHz frequency band and supports data transfer rates of 54 Mbps or 6.75 megabytes per second.

• IEEE 802.11a was the first Wi-Fi (Wireless Fidelity) system in the IEEE 802.11 family.
• IEEE 802.11a established a Wi-Fi standard for wireless communication in the 5 GHz ISM band, with raw data rates of up to 54Mbps.
• Although it is the first standard in the 802.11 series alphabetically, it was introduced in 1999 at the same time as IEEE 802.11b, which was intended for 2.4 GHz ISM band communication.
• IEEE 802.11a was more expensive and complex to implement at the time since it ran at 5 GHz rather than 2.4 GHz, and as a result, it was less extensively adopted.

Hence the correct answer is 54 Mbps.

IEEE 802.11 wireless LANs use a media access control protocol called Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA).

All WiFi networks are contention-based TDD systems, where the access point and the mobile stations all use the same channel. Because of the shared media operation, all WiFi networks are half duplex.

The IEEE 802.11 protocol can also use a short Request To Send (RTS) control frame and a short Clear To Send (CTS) frame to reserve access to the channel.  When a sender wants to send a frame, it can first send a RTS frame to the receiver. A receiver that receives an RTS frame responds with a CTS frame, giving the sender explicit permission to send.

The correct answer is CSMA/CA.

Key Points

• CSMA/CA stands for Carrier Sense Multiple Access with Collision Avoidance.
• It is a network multiple access method used in IEEE 802.11 wireless network standards.
• CSMA/CA helps prevent collisions by using a technique where each device listens to the channel before transmitting data.
• If the channel is clear, the device sends a signal indicating its intent to transmit, then waits for an acknowledgment before actually sending the data.
• This method reduces the chances of collision and improves the reliability of data transmission in wireless networks.

Additional Information

• CSMA/CA is different from CSMA/CD (Carrier Sense Multiple Access with Collision Detection), which is used in wired Ethernet networks.
• In CSMA/CD, devices detect collisions after they occur and take steps to resolve them, while CSMA/CA aims to avoid collisions before they happen.
• IEEE 802.11 includes several amendments such as 802.11a, 802.11b, 802.11g, etc., all of which use CSMA/CA as the multiple access technique.
• Other multiple access techniques like CDMA (Code Division Multiple Access) and ALOHA are used in different networking standards and have different mechanisms for handling multiple access.

The correct answer is IEEE 802.3

Key Points

• IEEE 802.3 is a collection of standards that define the physical layer and the Media Access Control (MAC) sub-layer of the data link layer for wired Ethernet networks.
• CSMA/CD (Carrier Sense Multiple Access with Collision Detection) is a media access control method used in Ethernet networks to avoid collisions of data packets between devices sharing the same cable.
• Here's a brief overview of other IEEE 802.X standards:
  • IEEE 802.1 - Defines the overall architecture for IEEE 802 networks.
  • IEEE 802.2 - Defines Logical Link Control (LLC) sublayer.
  • IEEE 802.4 - Defines Token Bus and Token Ring standards for network access.

The correct answer is SSL

Consider three station A, B, and C where station B and C are within a range of A but station B is hidden to station c and vice versa. Station A sends CTS message which contains the duration of data transmission from B to A reaches C. Station C knows that some hidden terminal is using the channel and refrains from a transmission.

The CTS frame in CSMA/CA can prevent a collision from a hidden station.

IEEE 802.11 has three categories of frames: management frames, control frames, and data frames.  

Management frames are used for the initial communication between stations and access points.

Control Frames Control frames are used for accessing the channel and acknowledging frames.

Data frames are used for carrying data and control information.

Frame control indicates the type of frame (control, management, or data) and provides control information. Frame body contains an MSDU or a fragment of an MSDU. The MSDU is an LLC protocol data unit or MAC control information. Frame check sequence is a 32-bit cyclic redundancy check. Sequence control contains a 4-bit fragment number subfield, used for fragmentation and reassembly, and a 12-bit sequence number used to number frames sent between a given transmitter and receiver.

Network Access Vector (NAV) is a time slot reservation, in microseconds. It indicates the duration the station must wait before channel can be sampled again for sensing status of the medium. RTS/CTS pair with NAV covering up to the end of the ACK of the data packets are exchanged. The last ACK has a NAV of 0.