George Stefanick presented on advanced RF design and troubleshooting of WiFi networks. He discussed designing WiFi networks for coverage and capacity, including considering application requirements, client devices, channel planning, transmission power levels, and ensuring proper cell overlap and separation. He also covered the methodology for troubleshooting WiFi networks, including collecting information from end users, inspecting devices, reproducing issues, and using various monitoring tools.

1. Advanced RF Design and Troubleshooting
George Stefanick
December 2014

2. Wireless Architect @ Houston Methodist Hospital – 5 years
• Manage 3,000 Access points
• 11,000 concurrent clients / 26,000 total
• Deployed our first AWO (All Wireless Office) 300 users / 800 devices
Independent Consultant (training, site survey, security, deployment and troubleshooting)
Blog: www.my80211.com , www.nostringsattachedshow.com, Cisco Support Community and Aruba.
2
Started WiFi in late 90’s
Vendor and Vendor neutral certifications
Aruba MVP 2014
Cisco VIP 2012,2013 and 2014
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Who Am I ?
Interop - Speaker 2014 Las Vegas / NYC (Wifi Tools)
Cisco Live - Speaker 2013 Orlando (Deployment of 802.11ac)
Published Technical Editor – Sybex
Project: CCNA Wireless Study Guide by Todd Lammle
Published Technical Editor – Cisco Press
Project: Designing and Deploying 802.11 Wireless Networks: A Practical Guide to Implementing
802.11n and 802.11ac Wireless Networks For Enterprise-Based Applications (2nd Edition)
(Networking Technology) by Jim Geier

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In the next 60 minutes
Take (2) things away from this session you didn’t know
before then this session was a success!!
“I personally define my own success in how I can help
others on their journey in WiFi”

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Agenda
Designing WiFi Networks for RF Coverage / Capacity
(Overview)
The Methodology of Troubleshooting WiFi Networks
WiFi Tools and Monitoring For WiFi Networks

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Designing WiFi Networks for
RF Coverage / Capacity
• Designing WiFi for RF Coverage and Capacity

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Designing WiFi Networks for
RF Coverage / Capacity
We need to understand the technical reasons
“WHY”
there is a difference in design approach when
comparing coverage and density designs ..

7. WiFi Radios Listen, Transmit and Receive
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Fundamentals
CSMA-CA
NAV (Network Allocation Vector)
• Layer 2
• NAV (Time Busy After Transmission)
(ACKs, SIFS)
CCA (Clear Channel Assessment)
• Layer 1
• Energy Detect
• CS Carrier Sense
(Preambles / PHY Headers)

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Fundamentals
Preambles and PHY Headers
–Aruba Networks White Paper 802.11ac In-Depth

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Fundamentals
Constellations
–Aruba Networks White Paper 802.11ac In-Depth

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Fundamentals
Constellations
QPSK – 2 bits per modulation symbol at
90 degrees phase 4 wave forms
(phases)

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Fundamentals
Constellations

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Fundamentals
Layer 1 and Layer 2

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Fundamentals
Understand (CCI)
Majority of interference on todays WiFi networks
come from our own access points.
(CCI)
• High Power Radios
• Excessive Gain Antennas
• Excessive Overlap
• Poor Designs

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Fundamentals
TX Power and CSMA-CA
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TX Power In Relation To Cell Size

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Designing for WiFi Coverage
and Capacity
Typical Questions to Ask
Type of applications
• Real time (Voice / Video)
• EMR (Electronic Medical Record)
• PoS (Point of Sale)
• WMS (Warehouse Management System)
Type of WiFi devices
• Laptops
• Handhelds
• Phones
How many WiFi devices
UP/DOWN Bandwidth (Mbps) Requirements
Bands 2.4 GHz / 5 GHz
Area of coverage
Seamless Roaming Requirements*
WiFi Design
WiFi Grade
• Data
• Voice
• Vocera*
• RTLS
• Density (Indoor / Outdoor)
Identify High density areas
• Conference Rooms
• Lecture Halls
Security Requirements
• PCI
• HIPPA

16. Designing for WiFi Coverage
and Capacity
Generally Accepted WiFi Specifications
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DATA Cell Size @ -75 RSSI / 20% Cell Overlap
VOICE Cell Size @ -67 RSSI / 25% Cell Overlap
VOCERA* Cell Size @ -67 RSSI / 25% Cell Overlap
RTLS Cell Size @ -67 RSSI / 25% Cell Overlap
(Edge Coverage)
DENSITY Cell Size @ ?? RSSI / ??% Cell Overlap

17. Designing for WiFi Coverage
and Capacity
Bands 2.4 GHz / 5 GHz - Design for the future!
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2.4 GHz
Longer Wave Length (Longer Distance)
Most popular WiFi Frequency
Unlicensed
Over crowded
Many devices operate on 2.4
Limited channel selection (3 Channels)
5 GHz
Shorter Wave Length (Shorter Distance)
Popular WiFi Frequency
Unlicensed
20+ Channels
DFS
Not all clients support all channels
Careful with 2.4 GHz / 5 GHz enabled WLANs. Some client radios don’t make the best decisions.
Aruba’s Client Match aids with sticky clients.

18. Designing for WiFi Coverage
and Capacity
Channel Bonding – Should You Channel Bond?
20 MHz / 40 MHz / 80 MHz
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Just because you can bond 80 MHz doesn’t mean you should!
Let the design requirements dictate channel width. You may have specific
Access points bonding at 40 / 80 MHz while others are at 20 MHz.
Channel reuse is a must to consider during any design!

19. Designing for WiFi Coverage
and Capacity
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Channel Separation – 20 dBm
6 1 11
11 6

20. Designing for WiFi Coverage
and Capacity
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Channel Separation

21. Designing for WiFi Coverage
and Capacity
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Disable Low PHY Rates
DSSS / HRDSSS
1 PHY
2 PHY
5.5 PHY
11 PHY
ERP-OFDM / OFDM
6 PHY
9 PHY

22. Designing for WiFi Coverage
and Capacity
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High Channel Utilization

23. TX Power – Design for the lowest common device?
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Designing for WiFi Coverage
and Capacity

24. Example Excessive Transmission Power
1 Access Point Seen At -90 dBm – 250k sq feet Warehouse
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Designing for WiFi Coverage
and Capacity

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Example Excessive Transmission Power
-60 dBm
-70 dBm
-80 dBm
100% CCC or CCI
Designing for WiFi Coverage
and Capacity

26. Designing for WiFi Coverage
and Capacity
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TX Power @ 6mW
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Floor to Floor Coverage
1 Floor Below 2 Floors Below

27. Designing for WiFi Coverage
and Capacity
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TX Power @ 12mW
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Floor to Floor Coverage
1 Floor Below 2 Floors Below

28. Designing for WiFi Coverage
and Capacity
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TX Power @ 25mW
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Floor to Floor Coverage
1 Floor Below 2 Floors Below

29. Designing for WiFi Coverage
and Capacity
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TX Power @ 50mW
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Floor to Floor Coverage
1 Floor Below 2 Floors Below

30. Designing for WiFi Coverage
and Capacity
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TX Power @ 100mW
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Floor to Floor Coverage
1 Floor Below 2 Floors Below

31. Designing for WiFi Coverage
and Capacity
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TX Power @ 200mW
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Floor to Floor Coverage
1 Floor Below 2 Floors Below

32. Designing for WiFi Coverage
and Capacity
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Example Hallway Design

33. Designing for WiFi Coverage
and Capacity
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Limit Signal Pollution
• Shape Signal
• Antennas
• Walls
• Low Transmission Power
• Proper Channel Assignment

34. Designing for WiFi Coverage
and Capacity
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Do The Math – Maximize Your Performance
Application Bandwidth Requirements
• Web Browsing
• Video
• VoIP
Client Device Types
Maximum Clients Per Cell

35. Designing for WiFi Coverage
and Capacity
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Outdoor – These Fundamentals Apply
Mining
Oil / Gas
Stadium
Green Area

36. Designing for WiFi Coverage
and Capacity
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Success Starts Here
• Small cells low power
• Shape your signal
• Disable the low PHY rates
• Proper channel plan
• Proper cell overlap
• Know your application requirements
• Know your clients

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The Methodology of
Troubleshooting WiFi Networks
• The Methodology of Troubleshooting WiFi
Networks

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Mental Check Box
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The Methodology of
Troubleshooting WiFi Networks
Is the area of coverage designed and configured correctly ?
If yes, and no changes to (ARM) then move on to device debugs, logs and WiFi
Analyzer.
If no, fix the area of coverage
Where there any changes to the infrastructure, device configuration or application that
could cause this issue?
If yes, understand what changes were made.
If no, move on to device, debugs, logs and WiFi Analyzer.

39. Collect End User Data / Field Visit
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The Methodology of
Troubleshooting WiFi Networks
What is the issue from the end user perspective. Get detailed description of the problem.
Drop voice calls; Static calls; One way speech; Slow connection; Can’t Connect ; Specific Apps don’t
work; Multicast feature not working “Call to many”.
What device(s) are involved ?
Inspect device for damage; Driver Rev.; Configuration.
Can the issue be reproduced ?
ALWAYS try and get the device to fail yourself; Reproduce the failure. In almost all cases if you can get it
to fail. You can resolve the problem quicker. Test against known working devices side by side.
Is anyone else having a similar issue ?
If so, then track down these users and question them and compare stories. Best to do one on one
discussion and not group.
Are there any commonalities or differences in data collected ?
Is this isolated to a certain area of coverage; Certain population of devices or users.
When did this problem start happening?
Correlate to any possible network changes or pushes.

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The Methodology of
Troubleshooting WiFi Networks
Physically Inspect The Device

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The Methodology of
Troubleshooting WiFi Networks
Know Your Clients
• Cardiac Imaging
• Electronic Medical Record (EMR)
• Mobile Ultrasound
• Mobile Picture Archiving and Communications
systems (PACS)
• RTLS
• Mobile Robots
• Infusion Pumps
• Handheld Scanners
• Cows (Computer on Wheels)
• Cisco 7925 Handsets
• Vocera Badges
• Mobile Cisco TelePresence VX Clinical Assistant
• Roche Diagnostics ACCU-CHECK
• Mobile EKG Carts
• Mobile Med Dispensing Carts
• WorkGroup Bridges (WGB)
• Mobile Deaf Response Devices
• Patient Video Monitoring Carts
• DaVinci Simulators
• Laptops
• Tablets

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The Methodology of
Troubleshooting WiFi Networks
Clients Hear RSSI Differently

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WiFi Tools and Monitoring For
WiFi Networks
• WiFi Tools and Monitoring For WiFi Networks

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WiFi Tools and Monitoring For WiFi
Networks
Spectrum Analyzer

45. Wireless NICs, External USB Hubs, and Noise
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WiFi Tools and Monitoring For
WiFi Networks

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WiFi Tools and Monitoring For WiFi
Networks
Site Survey (Active, Passive, Virtual)

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WiFi Tools and Monitoring For WiFi
Networks
Site Survey (Active, Passive, Virtual)

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WiFi Tools and Monitoring For WiFi
Networks
Site Survey Rig

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WiFi Tools and Monitoring For WiFi
Networks
Sniffer

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WiFi Tools and Monitoring For WiFi
Networks
Mobile 802.11ac 3x3:3 (beta)
BY FLUKE AIRMAGNET

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WiFi Tools and Monitoring For WiFi
Networks
Aruba AirWave

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Education
“Having a powerful tool in
knowledgeable hands is the
difference between owning a
wireless problem or having a
wireless problem owning you”

53. Thank You
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