Correct a draft channel, power and security plan for a four-AP office floor

Steps

1. Read the floor. Four dual-band access points hang in a row along one corridor, from west to east: AP-A, AP-B, AP-C and AP-D. Neighbouring APs hear each other; AP-A and AP-D, at opposite ends, barely do. The draft plan is:

AP     2.4 GHz            5 GHz
AP-A   channel 1, 20 MHz  channel 36, 40 MHz
AP-B   channel 3, 20 MHz  channel 44, 40 MHz
AP-C   channel 6, 40 MHz  channel 100, 40 MHz
AP-D   channel 11, 20 MHz channel 149, 40 MHz

Copy it onto your worksheet, leaving room to correct each line. 2. Find the 2.4 GHz faults. List every pair of neighbouring APs whose 2.4 GHz channels overlap, remembering that channel centres are 5 MHz apart and each signal is about 20 MHz wide. Name the kind of interference that results (adjacent-channel, which corrupts frames rather than sharing airtime). Then say what is wrong with AP-C's 40 MHz width in this band. 3. Fix the 2.4 GHz plan. Rewrite it using only non-overlapping channels at 20 MHz, so that no two neighbours share a channel. With four APs and three clean channels, one channel must be reused: put the reuse on the pair that are farthest apart, and say which interference that pair could still cause if they hear each other (co-channel contention). 4. Check the 5 GHz plan. For each 5 GHz channel, write its UNII band and whether it needs Dynamic Frequency Selection. Then answer: if AP-C's 5 GHz radio suddenly changes channel on its own and its clients drop for a moment, what most likely happened? Decide whether 40 MHz is reasonable here, given how much more room 5 GHz has than 2.4 GHz. 5. Work the survey numbers. A survey at a desk in the meeting room reads AP-B's 5 GHz radio at -67 dBm with a noise floor of -92 dBm. At the east end of the corridor, AP-D's 2.4 GHz radio reads -84 dBm with a noise floor of -90 dBm. Work out the signal-to-noise ratio at each spot, and say which spot is at the edge of its cell. Then work out the power: AP-C's 5 GHz radio transmits at 14 dBm, about 25 mW. What is it in milliwatts if raised by 3 dB, and if raised by 10 dB? Finally, explain why AP-C's 5 GHz cell is smaller than its 2.4 GHz cell at the same power. 6. Fix the security plan. The draft security section says:

STAFF  WPA3-Personal only, on 2.4 and 5 GHz
GUEST  open, with a captive portal
STAFF  copied to 6 GHz as WPA2-Personal

Three requirements apply. Twelve warehouse scanners support only WPA2-Personal with CCMP and must keep working on STAFF. Guest traffic must be encrypted over the air, without guests typing a password. The new 6 GHz radios must carry STAFF. For each SSID, write the mode that meets its requirement, and the rule from lesson 5 that forces it. 7. Name the cause of each complaint. For each, write the cause and one fix: (a) Wi-Fi near the kitchen stalls from 12:00 to 13:00 on 2.4 GHz, while 5 GHz clients in the same spot carry on; (b) the training room tested well when empty, but coverage drops when 40 people are seated; (c) AP-A and AP-D, both on the reused channel, each show a strong signal to their own clients, but both cells slow down at busy times; (d) a Bluetooth headset user asks whether moving the headset to 5 GHz would help. 8. Write the final plan as one table: AP, 2.4 GHz channel and width, 5 GHz channel and width, DFS yes or no, and the security mode of each SSID on each band. Check it against every fault you found in steps 2 to 6.