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ATMOSPHERE 2014AIRHEADS@
Advanced RF Design & Troubleshooting Blake Krone June 2014
CONFIDENTIAL © Copyright 2014. Aruba Networks, Inc. All rights reserved
2 #AirheadsConf
ATMOSPHERE 2014AIRHEADS@Agenda
Who Am I? Past and Present Design Goals Design, Design, Design Love Thy Patch Demystifying RF With Tools
3 CONFIDENTIAL © Copyright 2014. Aruba Networks, Inc. All rights reserved
#AirheadsConf
ATMOSPHERE 2014AIRHEADS@
Who Am I?
4 CONFIDENTIAL © Copyright 2014. Aruba Networks, Inc. All rights reserved
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ATMOSPHERE 2014AIRHEADS@Who Am I?
Blake Krone [email protected] @blakekrone http://NSAShow.com All around tech junkie, programmer, RC junkie CWNA, CCIE #31229 (Wireless)
5 CONFIDENTIAL © Copyright 2014. Aruba Networks, Inc. All rights reserved
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ATMOSPHERE 2014AIRHEADS@
Past & Present Design Goals
6 CONFIDENTIAL © Copyright 2014. Aruba Networks, Inc. All rights reserved
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ATMOSPHERE 2014AIRHEADS@Pre #GenMobile Design Goals
Green = Good = Coverage
• Designed for Coverage – Full bars, devices were connected
• Large cells, high power
• Less than 2 devices per person – Laptop – Smartphone
7 CONFIDENTIAL © Copyright 2014. Aruba Networks, Inc. All rights reserved
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ATMOSPHERE 2014AIRHEADS@#GenMobile Design Goals
Green = Good = Coverage – no longer applicable!
• Designed for Capacity – I’m connected, but can I send/receive with 100 other
devices?
• Small cells, lower power
• More than 4 devices per person – Laptop – Smartphone – Tablet – Wearables
8 CONFIDENTIAL © Copyright 2014. Aruba Networks, Inc. All rights reserved
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ATMOSPHERE 2014AIRHEADS@How To Reach the Goals?
RF is like Black Magic, the Dark Arts, etc…
Or Is it?
• Design, Design, Design
• Troubleshooting Accordingly
9 CONFIDENTIAL © Copyright 2014. Aruba Networks, Inc. All rights reserved
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ATMOSPHERE 2014AIRHEADS@
Design, Design, Design
10 CONFIDENTIAL © Copyright 2014. Aruba Networks, Inc. All rights reserved
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ATMOSPHERE 2014AIRHEADS@About RF Design
Key to a Great Design
• Airtime – Be fair and play fair
• SNR
– Not just RSSI!
• Frequency & Channel Reuse – Clients are like 2 year olds, their way or the high way!
• Don’t Forget the Backbone – It’s never the RF, it’s those pesky servers!
11 CONFIDENTIAL © Copyright 2014. Aruba Networks, Inc. All rights reserved
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ATMOSPHERE 2014AIRHEADS@Airtime
Basic Design • RSSI Good • Legacy Data Rates
On • Longer Waits to Get
On • Longer Time On
Great Design • RSSI Great • Legacy Data Rates
Off • Get On and Off
Quickly
12 CONFIDENTIAL © Copyright 2014. Aruba Networks, Inc. All rights reserved
#AirheadsConf
ATMOSPHERE 2014AIRHEADS@Airtime Example
Download/Upload 1Mb File • 6Mbps Client – 1.33s • 36Mbps Client – 0.22s
How Many Users per 5 Minute? • 6Mbps – 230 • 36Mbps - 1363
13 CONFIDENTIAL © Copyright 2014. Aruba Networks, Inc. All rights reserved
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ATMOSPHERE 2014AIRHEADS@Airtime Calculations
Mode (20Mhz, 1ss – 3ss)
Receive Sensitivity per Chain (dBm)
SNR (dB) @ -95 dBm Noise Floor
Legacy 802.11a/g 54 Mbps
-75 20
802.11n HT20 MCS7/15 65 – 216 Mbps
-71 24
802.11ac VHT20 87 – 289 Mbps
-65 30
Great Resource for Calculating Device Airtime: http://www.revolutionwifi.net/p/downloads.html - WLAN Capacity Planning Overview and Worksheets.pdf
14 CONFIDENTIAL © Copyright 2014. Aruba Networks, Inc. All rights reserved
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ATMOSPHERE 2014AIRHEADS@SNR
SNR is More Important Than RSSI!
• RSSI is how strong I hear AP – Doesn’t imply quality
• SNR is relationship to noise floor
– Changes per site per area per day per environment etc
15 CONFIDENTIAL © Copyright 2014. Aruba Networks, Inc. All rights reserved
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ATMOSPHERE 2014AIRHEADS@SNR Example
Take datasheet values for AP-220 • 802.11n HT20 • MCS7/15 • 65 – 216 Mbps • 24 SNR Perfect world with -95 dB noise floor says -71
dBm RSSI. Reality says more like -65 dBm or better!
16 CONFIDENTIAL © Copyright 2014. Aruba Networks, Inc. All rights reserved
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ATMOSPHERE 2014AIRHEADS@Frequency & Channel Reuse
Use As Much Frequency As You Can
• 2.4GHz – Yes it’s dirty and bloated, but we need it
• 5.0GHz
– Don’t be shy, client adoption increasing rapidly
– Just watch out for DFS channels
• 20MHz Channels Might Make More Sense – We don’t always need insane speed but we do need
channels
17 CONFIDENTIAL © Copyright 2014. Aruba Networks, Inc. All rights reserved
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ATMOSPHERE 2014AIRHEADS@Frequency & Channel Reuse
• Lower the Power – Just cause an AP does 200mW doesn’t mean you should
allow it – Reduce the cell size to allow more channel reuse
• Steer When You Can - Client Ultimately Calls the Shots – If it thinks 2.4GHz is better it’ll join there – Always assume a roaming issue will occur
18 CONFIDENTIAL © Copyright 2014. Aruba Networks, Inc. All rights reserved
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ATMOSPHERE 2014AIRHEADS@Don’t Forget Backbone
RF Still Needs Wires & Core Services
• DHCP – Active clients vs Associated clients. Makes no difference,
they still use an IP if just associated. – Short lease times for guest – example football game is 3
hours, use 3 – 4 hours for lease
• AAA Scaling
– Account for Web/RADIUS server calls per second for portals
– Better yet, forget about the portal!
19 CONFIDENTIAL © Copyright 2014. Aruba Networks, Inc. All rights reserved
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ATMOSPHERE 2014AIRHEADS@
Love Thy Patch
20 CONFIDENTIAL © Copyright 2014. Aruba Networks, Inc. All rights reserved
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ATMOSPHERE 2014AIRHEADS@Love Thy Patch
Learn From Interior Lighting Engineers
• Flood or Spotlight? – While a floodlight might work is it the right solution? – Paint the area with RF like you would light.
• Omni or Patch? – Same rules apply here as they do with lights. – More precisely control signal spread
21 CONFIDENTIAL © Copyright 2014. Aruba Networks, Inc. All rights reserved
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ATMOSPHERE 2014AIRHEADS@Patch Example
How would you cover a long corridor that never seems to end and provide density coverage?
22 CONFIDENTIAL © Copyright 2014. Aruba Networks, Inc. All rights reserved
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ATMOSPHERE 2014AIRHEADS@Patch Example
Absolutely Not! Omnis Maybe
23 CONFIDENTIAL © Copyright 2014. Aruba Networks, Inc. All rights reserved
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ATMOSPHERE 2014AIRHEADS@Patch Example
Use patch antennas alternating down a hallway.
Signal goes where you
want, antennas accessible.
24 CONFIDENTIAL © Copyright 2014. Aruba Networks, Inc. All rights reserved
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ATMOSPHERE 2014AIRHEADS@
Demystifying RF With Tools
25 CONFIDENTIAL © Copyright 2014. Aruba Networks, Inc. All rights reserved
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ATMOSPHERE 2014AIRHEADS@Demystifying RF
A screwdriver makes a decent hammer, but a hammer is better.
• Survey Tools – Site Survey Software – Spectrum Analysis Software
• Packet Tools • Testing Devices
26 CONFIDENTIAL © Copyright 2014. Aruba Networks, Inc. All rights reserved
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ATMOSPHERE 2014AIRHEADS@Survey Tools
Ekahau Site Survey • Predictive Design • Active (AP on Stick)
Survey • Post Validation
Survey • Proxim 8494
Adapters
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ATMOSPHERE 2014AIRHEADS@Spectrum Analyzer
Metageek Chanalyzer Pro
• USB Form Factor • 2 x Wi-Spy DBx for
2.4 & 5GHz simultaneous
• Easy to Use • Report Builder
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ATMOSPHERE 2014AIRHEADS@Packet Capture
Metageek Eye P.A • Compatible with
pcap files • AirPcap direct
capture • Visualizes the
packet flows
29 CONFIDENTIAL © Copyright 2014. Aruba Networks, Inc. All rights reserved
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ATMOSPHERE 2014AIRHEADS@Testing Devices
Fluke AirCheck • Rugged handheld
test device • Consistent
readings • Fast startup • Auto Test tool • Import / Export data
30 CONFIDENTIAL © Copyright 2014. Aruba Networks, Inc. All rights reserved
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ATMOSPHERE 2014AIRHEADS@Testing Devices
Fluke LinkSprinter 200 • Extremely portable • PoE, Link, VLAN,
DHCP, Internet testing device
• WiFi hotspot for advanced mobile display
31 CONFIDENTIAL © Copyright 2014. Aruba Networks, Inc. All rights reserved
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ATMOSPHERE 2014AIRHEADS@
Questions
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DOWNLOAD: Airheads Mobile
JOIN: community.arubanetworks.com
FOLLOW: @arubanetworks
DISCUSS: #AirheadsConf
ATMOSPHERE 2014AIRHEADS@
33
Thank You
#AirheadsConf CONFIDENTIAL © Copyright 2014. Aruba Networks, Inc. All rights reserved