View the on-demand webinar here: http://www.netscout.link/60048mlcI What's worse than bad Wi-Fi? Bad Wi-Fi that tests like good Wi-Fi. Join NETSCOUT and Ben Miller for this webinar, Deceptive Speed: How to Fix Fast, Unstable Wi-Fi, and learn simple tools and methods for diagnosing and resolving real world Wi-Fi performance issues. Ben Miller is a wireless specialist based out of Los Angeles, CA. Ben offers training services for professional training centers and organizations looking to design, manage and support wireless networks. Mr. Miller also offers surveying services to organizations in need of wireless network optimization.

2. Today’s Webinar: Deceptive Speed: How to
Fix Fast, Unstable Wi-Fi
• Presenter: Ben Miller, Wireless Specialist
• Today’s webinar will be available on-
demand following this live session. Simply
use the same url you used today.
Follow us @NETSCOUT

3. People Love Throughput Tests
• Tech folks: ‘stress testing’
• Regular folks: “will my app work?”
• Several methods
– Apps – Speedtest
– Web - Google

4. The problem with Wi-Fi throughput tests
• Changes as channel conditions change
• Device-dependent
• Affected by non- Wi-Fi factors

5. But… Let’s say you want throughput
• In Wi-Fi, higher throughput = less stability
• Optimized throughput settings give you…
– More crowded channels
 Wide channels = fewer channels = more device per channel
– Higher SNR required
– Less channels available (Band steering)
 2.4 GHz channels unavailable to many devices
– Less channel time in difficult areas (Airtime fairness)

6. If you still want high throughput…
• Use wider channels
– 40 MHz; maybe even 80 MHz
• Enable DFS
– Channels 52-144
• Use low AP Tx power
• Enable band steering
• Enable airtime fairness

7. Now… If you want stable Wi-Fi
• Issues beyond the Wi-Fi
• What affects Wi-Fi throughput?
– How to analyze it
• One… more… thing

8. • Each ‘leg’ is independent
– Wi-Fi speed
– Network speed
– Internet speed
Issues beyond Wi-Fi: ‘Data relay race’
Server
Internet Network Wi-Fi

9. What affects Wi-Fi throughput?
• Data rates
• Number of frames
• Retries
• Neighbors

10. • High data rate = less required channel time
‒ For data and Layer 2, 3, 4 headers
Data rates
AP
1500 Bytes
Near Far
1500 Bytes
Near
Far
Timeline
(173 Mbps)
(39 Mbps)
(quiet)
(quiet)

11. Identifying data rates
• Wi-Fi channel analyzer (a.k.a. Wi-Fi protocol analyzer)
‒ NETSCOUT AirMagnet WiFi Analyzer
 Included in NETSCOUT OptiView XG

12. Number of frames
• Approx. 100 microseconds of collision avoidance
• Approx. 40 microseconds per PHY header
1500 Bytes
Near
Near
Timeline
(173 Mbps)
1500 Bytes
(173 Mbps)
PHYCSMA/CA
PHYCSMA/CA
Drawn to scale; data includes SIFS and Ack
(quiet)
(quiet)

13. Identifying the number of frames
• Wi-Fi channel analyzer

14. • Wasted channel time
Retries
1500 Bytes
Near
Near
Timeline
(173 Mbps)
1500 Bytes
(173 Mbps)
PHYCSMA/CA PHYCSMA/CA
Drawn to scale; data includes SIFS and Ack
(quiet)

15. Cause of retries
• Crowded channel
• Interference

16. Identifying retries
• Wi-Fi channel analyzer

17. Neighbors
• Creates extra quiet time
– Collision avoidance
• Two ways neighbors cause issues
– Lots of devices
– Lots of Wi-Fi traffic

18. Identifying neighbor traffic
• Wi-Fi channel analyzer

19. Identifying neighbor devices
• Wi-Fi Scanner
‒ NETSCOUT AirCheck G2

20. There’s one… more… thing…
• Auto test!
• Tap once - let the AirCheck G2 do the rest
‒ (Field techs will thank you)
• Summarizes everything

21. Questions?
• Webinar: Deceptive
Speed: How to Fix Fast,
Unstable Wi-Fi
– Presented by Ben
Miller, Wireless
Specialist
AP

22. THANK YOU
• Today’s webinar will be available on-demand immediately
following today’s live session. Simply use the same url that
you used today.
enterprise.netscout.com