1. Please describe the differences between Independent BSS and Infrastructure BSS in WLAN. 2. Please describe the differences between Association and Re-association in WLAN. 3. What is the hidden node problem in the wireless network? How to address this problem in WLAN? 4. Under what scenario that the RTS/CTS mechanism in IEEE802.11 may be disabled by the dot11RTSThreshold attribute in the MIB (Management Information Base) ? 5. In the 802.11, Network Allocation Vector (NAV) is used to realize the Virtual Carrier Sense. How the NAV is determined? 6. What are the schemes used in 802.11 to achieve collision avoidance