Cisco CleanAir: Spectrum Analyzers Are Not All Created Equal

Cisco Confidential 1© 2011 Cisco and/or its affiliates. All rights reserved.

Spectrum Analyzers are Not All Created Equal

David Stiff, Product Line Manager, Cisco

Michael Rhoades, IT Administrator, North American Höganäs

© 2011 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 2

• Interference Impact on Network Performance

• Detection, Classification and Isolation

• Standalone vs. System Level Solution

• What to do About Interference?

• Höganäs AB - Customer Case Study

I can’t do my job without wireless. It has to work.

“”

Wireless is best-effort. I can’t support a level 1 SLA.

“”

IT Lacks RF Resources and

Expertise

VS

ContinuedGrowth and Reliance

on Wi-Fi Devices

Limited Spectrum

Performance

802.11n Performance Decrease

SYSTEM OVERLOAD!

Support Cost

Increase in Support Cost

$ $ $ $

Throughput

Reduction

Interference TypeNear(25 ft)

Far(75 ft)

2.4 or 5 GHz

Cordless

Phones100% 100%

Video Camera 100% 57%

Wi-Fi(busy neighbor)

90% 75%

Microwave

Oven63% 53%

Bluetooth

Headset20% 17%

DECT Phone 18% 10%

End User Impact

Reduced network capacity and coverage

Poor quality voice and video

Potential complete link failure

IT Manager Impact

Potential security breaches

Support calls

Increased cost of operation

Source: FarPoint Group

http://www.cisco.com/wirelesssecurity


• 802.11a/b/g/n - CSMA/CA or LBT (Listen Before Talk)

• Collision Avoidance – 802.11 very very polite – by design

CCA – Collisions - SNR

• CCA – Clear Channel Assessment

Energy Detect – quick – low power - prone to false positives

Wi-Fi Preamble – takes time – power – less prone to false

• CCA threshold for 802.11b/g is -65 dBm

• CCA for 802.11a is different -65 dBm ED, if true then 20 dB lower for Preamble interrogation needs to be processed -85 dBm


• Collisions - Non Wi-Fi devices do not participate in our CA mechanism – they have their own

• No respect for Wi-Fi – results in:

Corrupted packets

Increased retransmissions

Increased Duty Cycle

Less available bandwidth

• SNR – Signal to Noise ratio

High SNR Low SNR

Signal

Noise

Energy Levels


• Duty Cycle of interference is directly proportionate to channel time available

• Busy network – less interference tolerance

• Less busy – might not even notice low levels of interference

• Bandwidth is like Money – the more you get the more you spend


• A Wi-Fi chip is a communications processor – a MODEM

• It only knows

Energy that can be demodulated = Wi-Fi

Energy that can not be demodulated = Noise

• Noise is complicated! It can be caused by:

Collisions, fragments, corruption, …

Wi-Fi that is below sensitivity threshold of the receiver

• Peaks in Wi-Fi activity can cause all of the above to occur

• Allowing Automatic & Fast channel changes purely based on noise leads to network instability from sporadic re-channeling


Typical Wi-Fi chipset

Spectral Resolution at 5 MHzCisco CleanAir Wi-Fi chipset

Spectral Resolution at 78 to 156 KHz

‘Chip View Visualization’ of Microwave oven and BlueTooth Interference

Microwave oven

BlueTooth

Microwave oven

BlueTooth

Po

we

r

Po

we

r

?

Spectrum Analysis with no compromise to data throughput


• Custom CleanAir ASIC with 4 cores:SAgE, DSL, CPU, and Wi-Fi

• SAgE has an additional 500K gates for SI

• SAgE is the spectrum analyzer that was used on the Spectrum Expert Cards (Spectrum Analysis Engine)

• All Detection & Classification done in ASIC at AP

• No impact to data forwarding

• Minimal info passed to controller

DSP CPU

2.4 GHz 5 GHz

SAgE Wi-Fi

Antenna

Non Wi-Fi Energy Detection

FFT, Pulse routines, etc

Signal Isolation

Energy Stream Analysis

Interference Classification

1 GB Data Stream/Sec

100

35

Uniquely identify and track

multiple interferers

Assess unique impact to Wi-Fi

performance

Monitor AirQuality

Detect & Classify

How?

Inside the CleanAir ASIC


Cisco Unified Wireless Network 7.0 Release

• 2.4 GHz only

Bluetooth Link

Bluetooth Discovery

802.11FH

Microwave Oven

Industrial wireless/802.15.4

Xbox

• 5 GHz only

Radar

WiMAX Mobile

WiMAX Fixed

• 2.4 or 5 GHz

Jammer

Wi-Fi Inverted

Wi-Fi Invalid Channel

Continuous Transmitter

Video Camera

SuperAG

Canopy

Other (i.e. unclassified devices)

TDD Transmitter

DECT-like PhoneDefinite Security Threat Devices

Potential Security Threat Devices

Performance Impacting Devices

1. Classifiers are expandable over time with software upgrade.

2. All third party trademarks are the property of their respective owners.


Air Quality is a measurement of non-Wi-Fi and adjacent channel Wi-Fi interference

All Individual devices when Classified are assigned a Severity Value. A Severity of 0 is not severe, a Severity of 100 is very severe.

For the same device – severity will differ on each reporting AP because of the AP’s RF relationship to that device

Air Quality is a measure of all Devices/Severities within a Radio, Floor, Building, or Campus

Good

Bad


• Persistent Device Avoidance – PDA

Operates on Interferer Classification on a per AP basis

Once set – biases RRM’s channel picking algorithm against the “PDA channel” for the detecting AP only

Remembers interference and avoids placing the AP back on the same channel

• Energy Detect RRM or “ED-RRM”

Fast acting (=< 30 seconds)

Triggered by AQI value on a per AP basis

Designed to prevent catastrophic interference from disrupting channel/clients

NOTE: Only Available with full CleanAir enabled installation – not overlay


WLC GUI - Wireless=>802.11a/b=>RRM=>DCA

WCS – Configure=>controllers=>802.11a/b=>RRM=>DCA

Enabled Per Band

Same on WCS or WLC

EDRRM has threshold variable

ED-RRM AQI thresholds:Low – 35

Medium (default) – 50

High - 60


• Multiple APs = Multiple Sensors

• Each AP assigns a Psudo-MAC to an identified device

• WLC compares Psudo-MACs from each AP and merges devices seen into one physical interferer when appropriate.

• MSE calculates location of the one, real device.

• Prevents False reporting and alert proliferation.

• Aids in quick troubleshooting. Easy to find THE interfering device.

90


• Reactive troubleshooting used when interference suspected

• Fly the expert onsite with expensive tools

• Live troubleshooting in a production environment

• Resolution can be time consuming

• Challenges

Requires expertise

Hard to find the interferer

No continuous monitoring

Lengthy resolution time

Travel & time & cost requirements Cisco Spectrum Expert


Keys to Success

1. Continual, system-wide discovery to recognize interference exists

2. Accurately identify source(s) of interference and scope the impact

3. Take intelligent, automatic action to avoid current and future interference

Reduce OpEx

Incre

ase R

elia

bili

ty


Benefits Features

Self Healing and Optimizing

Troubleshooting Forensics

Wireless Security

Policy Enforcement

AirQuality Aware RRM

Event Driven RRM

Persistent Device Avoidance

Unwanted Device Notification

Unwanted Device Location

Remote Client Troubleshooting

Spectrum Expert Connect

Location, Impact Analysis & History Playback

New Rogue Threats Detection

(off-channel, inverted)

DOS Jammer Detection

Reduces Downtime, Maximizes Resilience

Lowers Problem Resolution Time/Cost

Improves Visibility to New Threats

Enables Enforceable Rules


Product Functionality

AP3500

Wireless LAN

Controller

MSE

NCS

None Multi-interferer Detection & Classification

AirQuality Monitoring

Self-Healing Event Driven RRM

Standard per AP count Remote Client Troubleshooting

AirQuality Visualization and Mapping

Forensics Tools

Location Visualization

Impact Analysis

History Playback

AirQuality Aware RRM

Self-Learning Persistent Device Avoidance

Spectrum Expert Connect

AirQuality and Interferer Alerts

Context Aware client license

required for each interferer

tracked

MSE adds support for 100

interferers when AP3500 present

(5 per AP, additive)

Interferer Tracking and Merging

Location Calculations

History Storage

Standard per AP

Licensing

Requirements

Cisco Confidential 22© 2011 Cisco and/or its affiliates. All rights reserved.

North American HöganäsWireless Implementation

Michael RhoadesIT Administrator


• Höganäs AB

• Based in Höganäs Sweden

• Worlds Largest producer of Iron Powders

• Multi-National Company

• Publically held and traded on the Swedish Stock Exchange in Stockholm


• 4 Sites in the US

Hollsopple, PA (Stony Creek Plant (HQ))

Johnstown, PA

St Mary’s, PA

Niagara Falls, NY

• 360 Employees

2 Full time IT Staff

• Microsoft Environment


• Cisco Unified Communications (Version 8.5)

• Cisco Unified Messaging

• Cisco Unified Presence

• Cisco Catalyst 3750 Series Core Switch MDF

• 22 – Cisco Catalyst 3560 IDF’s


• Large Warehouse with 500,000 Sq. Ft.

• Coverage Areas:

Maintenance

Production

Logistics (Fork Lift Computers)

• Emergency Device Tracking


• Surveyed at 2.4-GHz 802.11b/g

• 2 Cisco 4400 Series Wireless Controllers

• 52 Cisco Aironet 1240 Series Access Points

Mounted very high inside and outside of the plant

• Cisco 7921 Wireless Phones

• Omni Directional High Gain Antennas

• Added 5-GHz and 802.11a

No major improvement


• Large Steel Building

500,000 Square Feet

Two 7 Story Bay Open Steel Structures

Numerous Multi-level Spaces

Large Equipment

• Metal Powder in the Air

• Large Metal Racks with 2 Ton Bags of Metal Powder

• Magnetic Separator

• Overhead Cranes

• Tunnels, Small Enclosed Spaces

• Electric Arc Furnace

• Poured Concrete Walls with Rebar


• Multipath

• Reflection

• Shadowing

• One way calling

• Loss of service (Leaving Service Area)

• Antenna Patterns missing coverage area

• AP’s improperly placed

• Wrong Antennas

• Interference from plant equipment

• Other wireless networks (Friendly Rogues)


• Cisco Advanced Services

Survey for Harsh Environments

• 802.11a/g/n

2.4GHz (primary) and 5GHz

• 3 qty 5505 Series Controllers

• Cisco WCS (Wireless Control System) for Management

• MIMO technology

• 90 Cisco Aironet 3500 Series APs with CleanAir technology

• 50 Cisco 7925G-EX wireless phones


• Use Cisco Aironet 3500 Series Access Points with CleanAir Technology and Wireless Controllers

• Use small Di-pole and Directional Antennas to ensure proper coverage

• Lower placement of AP’s

• RRM (Radio Resource Management)


• Locates Interference with Zone of Impact

• Air Quality Results

• Map Visualization with WCS

• Persistent Device Avoidance

• Self Healing Networks

• ClientLink and MIMO

802.11a/g devices work better


• Helps troubleshooting performance problems in real-time

• Tracks intermittent and past problems

• Reporting on usage and interference trends

• Reduces man hours to manage and troubleshoot wireless problems


• Outdoor Survey

• Upgrading from WCS to Prime NCS

• Cisco Aironet 1500 Series Mesh Access Points


• Survey

• WCS

• AP Placement (Lower)

• AP Selection

• Antenna selection and mounting angles

Thank you.

Cisco CleanAir: Spectrum Analyzers Are Not All Created Equal

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