Collision Detection in Wireless LAN

In a wireless LAN (Local Area Network), collision detection is not possible. Collision detection is a mechanism used in wired LANs to detect and manage collisions that may occur when two or more devices transmit data simultaneously on the same network segment. However, in wireless LANs, due to the nature of the medium and the lack of direct physical connections, collision detection is not feasible.

Explanation:

1. Collision Detection
Collision detection is a process used in wired LANs to detect when two or more devices transmit data simultaneously, resulting in a collision. In wired LANs, devices are connected to a common network segment, and they can sense the medium to detect collisions. When a collision is detected, the devices involved in the collision follow certain protocols to manage the collision and retransmit their data.

2. Wireless LAN
In wireless LANs, devices communicate through wireless signals instead of physical connections. The wireless medium is shared among multiple devices, and each device has to contend for access to the medium. Unlike wired LANs, wireless LANs cannot directly sense the medium to detect collisions. Therefore, collision detection and subsequent collision management protocols are not applicable in wireless LANs.

3. Collision Avoidance in Wireless LANs
While collision detection is not possible in wireless LANs, collision avoidance mechanisms are employed to minimize the chances of collisions. The most commonly used mechanism is the Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA). It involves devices sensing the medium before transmitting and avoiding transmission if they detect ongoing transmissions by other devices.

Conclusion
In wireless LANs, collision detection is not possible due to the nature of the wireless medium. Instead, collision avoidance mechanisms like CSMA/CA are used to minimize collisions. Therefore, the correct answer to the given question is option 'A' - collision detection.