Advanced RF Design & Troubleshooting

Advanced RF Design and Troubleshooting

George Stefanick

December 2014

2CONFIDENTIAL

© Copyright 2014. Aruba Networks, Inc.

All rights reserved#AirheadsConf

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

Started WiFi in late 90’s

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)

Vendor and Vendor neutral certifications

Blog: www.my80211.com , www.nostringsattachedshow.com, Cisco Support Community and Aruba.

Aruba MVP 2014

Cisco VIP 2012,2013 and 2014

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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”

CONFIDENTIAL


All rights reserved4 #AirheadsConf

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 for RF Coverage and Capacity

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We need to understand the technical reasons

“WHY” there is a difference in design approach when

comparing coverage and density designs ..

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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)

WiFi Radios Listen, Transmit and Receive

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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 AskType 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

• HIPAA

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Generally Accepted WiFi Specifications

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


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Bands 2.4 GHz / 5 GHz - Design for the future!

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.


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Channel Bonding – Should You Channel Bond?

20 MHz / 40 MHz / 80 MHz

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!


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Channel Separation – 20 dBm

6 1 11

11 6


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Channel Separation


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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

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High Channel Utilization


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TX Power – Design for the lowest common device?


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Example Excessive Transmission Power

1 Access Point Seen At -90 dBm – 250k sq feet Warehouse


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Example Excessive Transmission Power

-60 dBm

-70 dBm

-80 dBm100% CCC or CCI


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Floor to Floor Coverage

1 Floor Below 2 Floors Below

TX Power @ 6mW


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TX Power @ 12mW


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TX Power @ 25mW


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TX Power @ 50mW


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TX Power @ 100mW


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TX Power @ 200mW


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Example Hallway Design


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Limit Signal Pollution

• Shape Signal• Antennas

• Walls

• Low Transmission Power

• Proper Channel Assignment


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Do The Math – Maximize Your Performance


Application Bandwidth Requirements• Web Browsing

• Video

• VoIP

Client Device Types

Maximum Clients Per Cell

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Outdoor – These Fundamentals Apply

Mining

Oil / Gas

Stadium

Green Area


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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

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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.

Mental Check Box

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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.

Collect End User Data / Field Visit

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Physically Inspect The Device

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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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Clients Hear RSSI Differently

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• WiFi Tools and Monitoring For WiFi Networks

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WiFi Tools and Monitoring For WiFiNetworks

Spectrum Analyzer

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Wireless NICs, External USB Hubs, and Noise


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Site Survey (Active, Passive, Virtual)

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Site Survey (Active, Passive, Virtual)

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Site Survey Rig

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Sniffer

50CONFIDENTIAL




Mobile 802.11ac 3x3:3 (beta)

BY FLUKE AIRMAGNET

51CONFIDENTIAL




Aruba AirWave

52CONFIDENTIAL



Education

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

Advanced RF Design & Troubleshooting

Technology

Transcript of Advanced RF Design & Troubleshooting