CWDP-305 Exam Dumps : Certified Wireless Design Professional

When APs are deployed in the same physical pattern across floors without channel and physical spacing considerations, co-channel interference (CCI) between floors occurs. This is particularly problematic when APs on different floors are vertically aligned on the same channels.

From CWDP-305:

“In multi-floor deployments, avoid placing APs on the same vertical axis across floors using the same channel. This leads to CCI. Stagger AP locations and vary channels to reduce interference.”

— Reference: CWDP-305 Official Study Guide, Wireless Design Process Chapter

In environments where access points (APs) are mounted on high ceilings (e.g., over 20 feet), it's essential to direct the wireless signal downwards towards the client devices on the floor. Patch antennas, which are directional antennas, are ideal for this scenario as they can focus the RF energy downward, providing better coverage and signal strength to the intended area.

The CWDP-305 Official Study and Reference Guide emphasizes the importance of antenna selection based on mounting height and coverage requirements:

"When APs are mounted on high ceilings, using directional antennas like patch antennas can help focus the RF energy towards the client devices, ensuring optimal coverage and performance."

Comprehensive and Detailed Explanation:

In a 3x3 802.11n configuration supporting two spatial streams over a 20 MHz channel with a short guard interval (400ns), the maximum data rate achievable is 144 Mbps. This is derived from the MCS (Modulation and Coding Scheme) index tables defined in the 802.11n standard, where MCS 15 corresponds to two spatial streams at 64-QAM modulation with a 5/6 coding rate. Therefore, the correct maximum MCS rate for this configuration is 144 Mbps.