1. Chapter 12 WLAN Troubleshooting
Certified Wireless Network Administrator (CWNA)
PW0-105
Chapter 12
WLAN Troubleshooting

2. Chapter 12 Overview Layer 2 Retransmissions
Coverage Considerations
Voice vs. Data
Performance
Weather
Certified Wireless Network Administrator: CWNA – PW0-105 2

3. Layer 2 Retransmissions
Retransmissions occur when the sending STA does not receive an ACK frame from the target STA
Layer 2 retransmissions impact performance
Increase overhead
Increase latency and jitter
Real-time applications are impacted most by retransmissions
All communications are slower
Certified Wireless Network Administrator: CWNA – PW0-105 3

4. Layer 2 Retransmissions Causes
RF Interference
Multipath
Adjacent Channel Interference
Low SNR
Mismatched Power Settings
Near/Far
Hidden Node
Certified Wireless Network Administrator: CWNA – PW0-105 4

5. RF Interference
Certified Wireless Network Administrator: CWNA – PW0-105 5

6. Multipath
Certified Wireless Network Administrator: CWNA – PW0-105 6

7. Adjacent Channel Interference
Certified Wireless Network Administrator: CWNA – PW0-105 7

8. Low SNR
Certified Wireless Network Administrator: CWNA – PW0-105 8

9. Mismatched Power Settings
Certified Wireless Network Administrator: CWNA – PW0-105 9

10. Near/Far
Certified Wireless Network Administrator: CWNA – PW0-105 10

11. Hidden Node (Obstruction)
Certified Wireless Network Administrator: CWNA – PW0-105 11

12. Hidden Node (Large Coverage Cell)
Certified Wireless Network Administrator: CWNA – PW0-105 12

13. Hidden Node (Distributed Antenna System)
Certified Wireless Network Administrator: CWNA – PW0-105 13

14. Hidden Node (RTS/CTS)
Certified Wireless Network Administrator: CWNA – PW0-105 14

15. 802.11 Coverage Considerations
Dynamic Rate Switching (DRS)
Roaming
Layer 3 roaming
Co-channel interference
Channel Reuse/Multiple Channel Architecture (MCA)
Single Channel Architecture (SCA)
Capacity vs. Coverage
Certified Wireless Network Administrator: CWNA – PW0-105 15

16. Voice vs. Data
Certified Wireless Network Administrator: CWNA – PW0-105 16

17. Performance Transmission power rates Antenna gain Antenna type
Wavelength
Free space path loss
Physical environment
CSMA/CA
Encryption
Application use
Number of clients
Layer 2 retransmissions
Certified Wireless Network Administrator: CWNA – PW0-105 17

18. Weather Lightning Wind Water Air stratification UV/Sun 18
Certified Wireless Network Administrator: CWNA – PW0-105 18

19. Chapter 12 Summary Layer 2 Retransmissions
Coverage Considerations
Voice vs. Data
Performance
Weather
Certified Wireless Network Administrator: CWNA – PW0-105 19