Solution

The correct answer is C, A, B, D.

Key Points

• SIFS (Short Interframe Spacing): It is the shortest interframe time interval used for high-priority transmissions like acknowledgments and RTS/CTS frames.
• PIFS (PCF Interframe Spacing): This is slightly longer than SIFS and is used by the Point Coordination Function to gain access to the medium before DCF.
• DIFS (DCF Interframe Spacing): It is longer than both SIFS and PIFS and is used for contention-based access under the Distributed Coordination Function.
• EIFS (Extended Interframe Spacing): This is the longest interframe time interval, used for retransmissions in response to corrupted frames.

Additional Information

• IEEE 802.11 Standards:
  • Interframe time intervals are crucial in determining the priority of access to the wireless medium.
  • SIFS is used for time-critical operations like acknowledgments and control frames.
  • PIFS enables PCF to access the medium before DCF-based devices.
  • DIFS is used for regular data transmissions under contention-based access.
  • EIFS is used as a recovery mechanism after detecting frame corruption.
• Purpose of Interframe Spacings:
  • Ensures efficient and fair access to the wireless medium.
  • Allows prioritization of critical transmissions over regular data frames.
  • Helps in avoiding collisions and maintaining network stability.
• Important Points:
  • Interframe spacings are predefined durations based on the IEEE 802.11 protocol.
  • The correct arrangement of these intervals helps in understanding the hierarchical access mechanism in wireless networks.