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© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 1BRKAGG-301314659_05_2008_x1

Wireless LAN Radio: Spectrum Management Best Practices


BRKAGG-3013


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Trouble with Bluetooth

$30 Billion HMO With over 8.5 Million Members

The ScenarioSouth Sacramento hospital IT staff had problems with theirSouth Sacramento hospital IT staff had problems with their mobile Point of Care terminals getting disconnected from the wireless networkThe network was surveyed and implemented at –65 dBmThe IT staff began planning to increase the density of their Wi-Fi infrastructure

Solution and OutcomeUsing Cisco’s Spectrum Expert, problematic Bluetooth devices were immediately identified, said devices were transmitting at 100 W/20 dB Cl 1 Bl t th


100 mW/20 dBm. Class 1 Bluetooth The Bluetooth reader devices were installed on all of the wireless carts in question Once Bluetooth readers were identified as culprits, the device manufacture reprogrammed Bluetooth devices to use a lower power outputIT staff solved issue without adding capacity, which likely would have created, not solved problems

“RF matters.”


Jim FlorwickCisco Systems



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What We’re Going to Cover

The challenge

Wireless trendsWireless trendsEvolution of the WLAN

Deploying with spectrum in mindSite survey

Cisco Radio Resource Management—RRM

Cisco Spectrum Expert


Cisco Spectrum Expert

Intelligent mitigationCHDM

RRM Dashboard

Spectrum Intelligence

The Challenge



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The Dynamic Nature of Spectrum

You are breathing the physical layer

RF reflects off thingsRF reflects off things

RF is absorbed by things

It’s a shared medium (as such, not all RF is always yours)

Requirements change in response to changes in the environment—not always helpful

Yet, if implemented and maintained properly, it’s a


, p p p y,technology enabler providing

Increased productivity

Creative freedom

Enhanced user experience—by putting the power of the network where the user lives and works

Mobility Refers to the Client—Not the infrastructure

Radio assets are fixed devices Clients Associate to AP

with Strongest Signal

Autonomous AP channel and power must be set in advance

Clients move about

Resource demands shift

g g


with client location, and density


5

Even When Well Planned, Things Change

Mission critical requires HA

Client technology refresh—additional device typesClient technology refresh—additional device types

Moves, adds, changes

New neighbors?


Multiple QoS Demands

Managing multiple QoS streams

Balancing dynamic demandsBalancing dynamic demands

Changing user requirements

Video Conferencing

VoD


Video and Audio Streaming

Voice


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A Series of Papers on Wi-Fi Interference Concluded…http://www.cisco.com/en/US/products/ps9393/prod_white_papers_list.html

Does Non–Wi-Fi Interference Matter?

Normal Range

Reduced Range

Degraded Range

VideoVoiceData


Reduced Coveragefrom 20% to 80% Reduced Call Quality Most Video Rated “Unwatchable”

..That Dramatic Loss in Quality of Mobility Services Will Result When Wi-Fi Encounters Interference

The Problem: Wi-Fi Competes for Spectrum

Bluetooth

802.11FHOlder microwave linksGame controllersWireless headphonesWireless videoMobile and fixed alarm systems

RadarMicrowave Ovens


Causes Issues That Slow Down Acceptance, Erodes Customer Confidence

Other Wi-Fi Networks 2.4/5 GHz Cordless Phones

yMotion sensorsFluorescent lightsA pinball machine (really)


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Wireless Trends


Evolution of WLAN

Wireless initially for casual data—user convenience

Customer expectations set for best effort serviceCustomer expectations set for best effort service

Maturing mobility applications

Enterprise class—mission-critical architectures

Enterprise class—end-to-end security

Productivity gains realized—customer expectations increased


Wireless access is now edge access

Multiple wireless devices—multiple spectrums

Spectrum Is a Mission-Critical Resource $$$$$


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Deploying with Spectrum in Mind


Deploying with Spectrum in Mind

Role of site survey is as important as ever—but has evolved

Understanding the existing spectrumUnderstanding the existing spectrum

Focus should be on fixed infrastructureAP placement

Density is important

Protocols supported

Rates supported


Interference sources

Mitigating issues

Planning tools

Designing for Sustainable Spectrum Management


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What’s Using the Spectrum Now?

Spectrum is finite

Duty cycle orDuty cycle or utilization of non–Wi-Fi devices (noise) matters


What’s Using the Spectrum Now?

Identify Interference, Hits to SNRSNR (Signal to Noise Ratio) is a ratio

To improve SNRIncrease signal

Or Reduce Noise



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AP Placement—Evaluate Problem Areas


AP Placement—Evaluate Problem Areas

Si lObject in Signal Path

Plasterboard wall

Glass wall with metal frame

Cinder block wall

Office window

3 dB

6 dB

4 dB

3 dB

Signal Attenuation


Metal door

Metal door in brick wall

Phone and Head position

6 dB

12 dB

6 dB


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Access Point Placement Guidelines

How many APs do I needDetermined by the site survey


Determined by the site survey

Planning mode in WCS can assist in determining adequate coverage density

Place where clients will be locatedIn a meeting room VSAN adjacent hallway

In a central location that can cover multiple walled offices

Not in a wiring closet

Coverage Density



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AP Placement Considerations—Multipath

Highly reflective environments

Multipath distortion/fade is a consideration

802.11b most prone

802.11g/a better

Things that reflect RF


Things that reflect RFIrregular metal surfaces

Large glass enclosures/walls

Lots of polished stone

Minimize the Impact of Multipath

Temptation is to mount on beams or ceiling rails

This reflects transmitted as well as received packets

Dramatic reduction in SNR due to high-strength, multipath signals


Minimize Reflections When Choosing Locations


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Planning Tools—Cisco Spectrum Expert





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Example: Microwave

Duty Cycle Higher in Part of BandLoud Moving

Signal Seen in Max and Max

Hold


Drifts in Frequency


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Example: Microwave


Example: Microwave

1

2

3

4

5

6


–11dBm–114dBm

6

7


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Planning Tools—WCS Planning Mode

Allows Comprehensive

Selection of AP and Antenna Type as Well as Several

Deployment Options

Allows the Addition of Obstacles

(Attenuations) to the Map, Default

Values Are Editable

Add in Existing APs from a

Deployed Floor


Options Values Are EditableGenerates a

Comprehensive Proposal Including Assumptions, Heat

and Rate Maps

WCS Planning Mode—AP SelectionAP TypeAntenna TypeProtocol Selection Including NgDesired Throughput Services Allows for

Selection of Data—Margins Adjustable in 3 Db Increments—Aggressive, Safe, Very Safe

Voice SettingsAggressive = Minimum [–78 dBm]Safe = Medium [–75 dBm]Very Safe = Maximum [(–72 dBm]7920_enabled = [(–72 dBm] (802 11a); 67 dBm (802 11b/g)]

Optimized Placement for Location with/


(802.11a); -67 dBm (802.11b/g)]

Demand Allows for Calculations Based on Total Users, as Well as Users per AP

Override to Bias the Coverage per AP

for Location with/ Without MMAP


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WCS Planning Mode

1 Cubicle

4 Light door

15 Heavy door

2 Light wall

13 Thick wall

Loss (in dB) Color coding Type of obstacle


Map Editor

1.5 Glass

Planning Tools—WCS



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Deploying with RRM in Mind


RRM—Radio Resource Management

What are RRM’s objectives?To dynamically balance the infrastructure and mitigate changesTo dynamically balance the infrastructure and mitigate changes

Monitor and maintain coverage for all clients

Manage Spectrum Efficiency so as to provide the optimal throughput under changing conditions

What RRM does not doSubstitute for a site survey


Correct an incorrectly architected network

Manufacture spectrum


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RRM Monitors the RF Group

Continuously monitors dynamic changes in environment

Collection of statistics and metrics used by DCA, DPC, and CHDM

Provides assessment of the overall “health” of the network

Stats/metrics include:Noise (e.g., radar, Bluetooth devices, microwave ovens)


Interference (802.11—both our WLAN and rogue APs)

Coverage

Load

Info on neighboring APs/radios

How Does RRM Do This?

DCA—Dynamic Channel AssignmentEach AP radio gets a transmit channel assigned to itchannel assigned to itChanges in “air quality” are monitored, AP channel assignment changed when deemed appropriate (based on DCA cost function)

DPC—Dynamic Power ControlTx Power assignment based on radio to radio pathlossDPC is in charge of reducing Tx on some APs—but may also increase Tx by defaulting back to


y y gpower level higher than the current Tx level

CHDM—Coverage Hole Detection and Mitigation

Detecting clients in coverage holesDeciding on Tx adjustment (typically Tx increase) on certain APs based on (in)adequacy of estimated downlink client coverage


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RF Group Controllers Elect an RF Group Leader That Analyses RF Data and Neighbor Relationships to Make More Intelligent Decisions About Optimizing the RF Environment for the System

About RF Groups

Wireless Controller ARF Group = <asciii string>

Wireless Controller BRF Group = <ascii string>

Environment for the System


< -80dbm

Neighbor Messages Are Sent At Full Power, Containing Information About the AP Seen, and Authenticated via a MIC Based on the RF Group Name

IF APs on Different Controllers Hear Neighbor Messages from APs in the Same RF Group at –80 Dbm or Greater They Will Group in an RF Subgroup, Channel, and Power Then Compute as a Group

LogicalRF sub-group (a)

RF Grouping and RF Domains

Multiple “RF subgroups” can exist within a single RF GroupRRM is calculated on a per RF group basis

LogicalRF sub-group (b)

Logical RF sub-group (c)Logical RF sub-group (b)

RFGroup 1RFGroup 1

RFGroup

RRM is calculated on a per RF group basisRF subgroups can be intercontroller or intracontrollerMultiple RF subgroups may be formed even when controllers share an RF Group name

RF groups/subgroups apply per PHY type


g g p ( )g g p ( )

Logical RF sub-group (d)Logical RF sub-group (a)

Logical RF sub-group (e)

LogicalRF sub-group (b)

LogicalRF sub-group (a)

LogicalRF sub-group (c)

RFGroup


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New Access Point Causes Co-Channel Interference

System Optimizes Channel Assignments to Decrease Interference

RRM—DCA—Dynamic Channel Assignment

RF Channel “6”RF Channel “1”


RF Channel “11”

What ItDoes

Ensures that available RF spectrum is utilized well across frequencies/channels

Best network throughput is achieved without sacrificing stability or AP availability to clients

DCA in a Nutshell

Who calculates DCAIt runs on the RF Group Leader WLCLeader WLC

Decisions on channel assignment change made on a per AP, per radio basis

DCA manages channel assignments to each AP

Assigns channels to radios

Changes the existing assignment


Changes the existing assignment on some radios, if appropriate

What criterion is evaluated:RSSI-based Cost Function that captures overall interference (including non-802.11 noise) on a channel


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DCA and Cost Metric

The value of CM is compared between the existing channel and the recommended channel for the single worst AP radio in RF groupRF group

Is the Δ(CM) > RSSI DCA Threshold value?

Pre version 5.0, RSSI DCA threshold value was fixed at 5 dB for all APs

Beginning in version 5.0—sensitivity is customer configurable—DCA Threshold sensitivity values are:

High Medium Low Sensitivity


High Medium Low Sensitivity

2.4 GHz band: 5dB 15dB 30dB

5 GHz band: 5dB 20dB 35dB

The new default is Medium SensitivityCorresponds to medium RSSI Δ(CM) threshold value

DCA Example

Suppose AP-1 has the worst CM in the RF Group with CM value –60 dBm on its current channel 6

DCA finds that the CM value could be –80 dBm on channel 11

This represents a potential Δ(CM) = 20 dBif we change channel 6 to channel 11 for AP-1

DCA would change the channel if sensitivity

AP-1


yset to High or Medium(5 or 15) < 20; no change would be made if sensitivity set to Low (30 > 20)


RF Channel “11”

AP-2AP-3


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RRM Support for 40 MHz

40 MHz channels can be configured automatically using Cisco WCS or Controller only

20 MHz

20 MHz40- HzGained

Space

Cisco WCS or Controller—only applies to 5 GHz radios

40 MHz channels can still be statically configured on 2.4 GHz radios

Improves 802.11n network performance

40 MHz = Two aggregated 20 MHz channels

Takes advantage of the reserved channel space through bonding to gain more than double the data rate of two 20 MHz channels


Available 40 MHz Channels

No DFS Support

DFS Support

4 11

2

1 3 5 7 9 11

4 6 8 10

5 GHz 40 MHz Channels

Cisco Aironet® 1250

DFS and Available Bandwidth

Scheduled DCA

Prior to release 5.1, DCA had a fixed run interval at 1 in 10; it ran once every 10 minutes

With the release 5.1 DCA is customer scheduled using two valuesAnchor Time—the time that DCA will first run 0100–2400

Interval–the interval between DCA runs–1–24 hours

Minimum interval is 1 hour

Scheduled DCA is off by default

Channel Change is the most disruptive change


The AP is temporarily unavailable

Some older Clients can become confused—and not find new channel

Channel changes should be done much more conservatively that TX power changes in DPC—less is more

Only a promise of considerable improvement should warrant a channel change


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DCA and Spectrum 802.11 b/g


802.11B/G and Duty Cycle

APs per Channel


Duty Cycle vs. Time


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Channel Utilization—What Made the Difference?

What Made This Dramatic

Change?

Before


5% After

Noise, Interference, and Utilization via WLC

RX Utilization 36

TX Utilization 7

Channel Utilization 96



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802.11B/G and Duty Cycle

Beacon SizeDSSS

100 200 250 300 350

1 896 1696 2096 2496 28962 496 896 1096 1296 1496

5.5 241 387 460 532 605

11 169 241 278 314 351

OFDM

6 153 287 353 420 48712 87 153 187 220 253


12 87 153 187 220 25324 53 87 103 120 13754 35 50 57 64 72

130 26 32 35 38 42300 23 25 27 28 29

Time µS

DCA—Initial Operations

DCA operates in three modesPre-deployment uses information from the AP to assign channel until CM data can be developed

Aggressive search—runs 1 in 10 for first 100 minutes exhaustive search

(Each time the controller boots up)

Less aggressive search—more local—less exhaustive

Sensitivity—medium by default


More concerned with higher throughput—set to High

More concerned with Client behavior and stability—set to Low

QoS queue—DCA will not change channels if traffic is in the queue

DCA will assign the best channel given the arguments


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Power Not Optimized—RF Signal Bleeds—Causes Interference

Decreased Power Limits Interference and Improves Application Performance

RRM—DCA—Dynamic Power Control



What ItDoes

TX power assignment based on radio to radio pathloss

DPC cf. in charge of reducing Tx on some APs—but it can also increase Tx by defaulting back to power level higher than the current Tx level (under appropriate circumstances)

RF Channel “11”

DPC in a Nutshell

Who calculates DPCIt runs on the RF Group Leader WLC

Decisions on TX power assignment change made on a per AP, per radio basis

DPC viewed as a two-stage processDetermining the ideal Tx for a radio given neighboring AP info

Deciding if making the change from Tx_current to Tx_ideal is actually worth one’s while


Determining Tx_ideal for a radioTx_ideal = Tx_max + (DPC_Threshold – RSSI_3rd)

Comparing the tentative improvement vs. the hysteresisIf change from Tx_current to Tx_ideal is small, since Tx changes can be disruptive, it may be better to leave AP’s Tx as is


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DPC—The Neighbor List

APs send Neighbor Messages at the highest TX power and lowest data rate for each supported protocol (802.11 a/b/g) and served channel at default 60 second intervalsand served channel at default 60-second intervalsWhen APs receive Neighbor Messages the frames are forwarded to the WLC to determine if the message is from the same RF group as the receiving APAn AP that sends either undecipherable Neighbor messages (indicating that a foreign RF group name is being used) or does not send Neighbor Messages, is determined to be a


rogue AP A neighbor list is formed for each AP in an RF subgroupAn RF subgroup is a group of APs that can hear each other within an RF GroupNeighbor list is pruned at 60-minute intervals

Neighbor Message Format

Field Name Description

Radio Identifier APs with Multiple Radios Use This to Identify Which Radio Is Being Used to Transmit Neighbor Messages

Group ID A Counter and MAC Address of the WLC

WLC IP Address Management IP Address of the RF Group Leader

AP’s Channel Native Channel on Which the AP Services Clients

N i hb M Ch l Channel on Which the Neighbor Packet Is


Neighbor Message Channel gTransmitted

Power Not Currently Used

Antenna Not Currently Used


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DPC—TX Power Threshold Notes

In release 4.2 the default TX power threshold is –70 dBm, the old default value was –65 dBm

Good results are generally achieved with values between –68 and –75 dBm

Ensure that the TX Power threshold is configured the same on all controllers

DPC runs on the RF Group leader, the WLC who was


elected

The TX Power threshold setting for the RF Group leader will be what is used for all DPC calculations

DPC—How It Works

Assume an AP’s neighbors are heard at the following RSSI levels (listed in decreasing order; units are [dBm])

–45, –55, –67, –75, –78, –80

For third loudest neighbor RSSI_3rd > DPC_ThresholdDPC_Threshold = –70 dBm

DPC would recommend a Tx power decrease

Important: the RSSI_3rd >? DPC_Threshold criterion only determines if Tx decrease is recommended


determines if Tx decrease is recommendedWhether the actual decrease takes place depends on hysteresis

The “delta” between the current and the recommended Tx

Hysterisis for a TX Power increase is 6 dB

Hysterisis for a TX Power decrease is 3 dB


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DPC—How It Works

There are two main TX power scenarios that can trigger an increase

There is no third neighbor

TPC Equation evaluates the recommended Tx to be in between Tx_max and Tx_current (rather than lower than TX_current)

Power decreases take place gradually –1 power level at a time (3 dB)

TPC i h i di t l


TPC power increases happen immediately

DPC—Why Is It the Third Neighbor?

2.4 GHz Uses Third Neighbor


5 GHz Uses 8th Neighbor


31

“RF Matters”


Intelligent Mitigation



32

Radio Resource ManagementCoverage Hole Detection and Mitigation

Access Point FailureCoverage Hole Detected and Filled

Normal Operation


What ItDoes

No single point of failure

Automated network failover decreases support and downtime costs

Wireless network reliability approaches wired

RRM—CHDM

Runs on every controller independently from the RF Group Leader

Detection—WLCDetermines for each client of an AP if that client is in a CH (coverage hole)

Keeps the count of how many of a given AP’s clients are in a coverage hole

Mitigation is dependant upon


CH detection—and NumFailedClients threshold

Decides if an AP’s TX needs to be increased

Decides on the rate/amount of increase

Operations Are Completely Independent of DPC, but Will Affect DPC and DCA


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How does WLC Detect a CH?

Based on SNR calculated from the APCan’t always know what the clients experience actually isCan t always know what the clients experience actually is

Not all detected holes are legitimateMobile clients moving out of coverage range

Sticky, poor roaming logic of a client

Not all legitimate coverage holes are fixable with TX increase


increaseAnd, not all that are should be

Think SystemwideOperations Are Completely Independent of DPC, but Will Affect DCA and DPC

CHDM Improvements—4.1.185

New Feature Expected/Desired System Behavior

NumClientsThresh: Threshold in Terms of the Number of Clients in

CH Required to Trigger the Mitigation Part of CHDM

(i.e., Whether the AP Should Increase Its Tx)

Tx Increase Is Triggered if and Only if NumFailedClients ≥

NumClientsThresh

TxIncreaseLimit: Knob That Th T I i Si l


TxIncreaseLimit: Knob That Controls the Amount of an APs Transmit Power Increase in a

Single Iteration Of CHDM

The Tx Increase in a Single Iteration Should Not Exceed

TxIncreaseLimit


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Important Improvements Version 5.0

Improved load metricsMassive improvements in accuracy of estimatesMassive improvements in accuracy of estimates

Impact to code base minor

Enhanced Coverage Hole DetectionVery important feature—impacts much of RRM

Main functional improvement: detecting clients that are roaming poorly


Note: Some of the components were not possible to be implemented in the Edgewood timeframe

Improvements in Load Metrics

Previous approximations of load metrics were poorSince the metrics were done at the host layer, RRM based on those

i l k d d i f l l i imetrics lacked a good picture of low layer activity

New estimates are much better since they are based upon PHY and Low Layer MAC measurements

Rx Load% of time the channel is utilized by traffic directed to the radio

(Of an AP in this case) i e Fraction of time spent listening to traffic


i.e., Fraction of time spent listening to trafficTx Load

% of time the channel is utilized by traffic sent by the radioi.e., fraction of time spent sending traffic

CCA Load% of time the channel is busy due to any kind of traffic


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Implementation Changes

LWAPP message changed to include only Rx, Tx, and CCA loads

Previously, a number of bytes were sent at each available rate

This doesn’t scale too well with 802.11n since there are so many different rates

PreviouslyAll clients were considered the same

Measurement interval was configurable from 180 secs to 3600 secs


Metrics and coverage thresholds were SNR-based

The desired coverage level for clients currently in coverage holes was based on a moving average

Measurements sent through LWAPP Airewave Director control messages

New CHDM Features

Ability to distinguishing between voice and data clientsDifferent RSSI coverage thresholds

Coverage holes can be detected on a 5-second intervalWLC can be notified with these pre-alarms

Aggregated coverage data is sent on a fixed 90-second interval basis

Measurements are done based on RSSI histograms

Detection of poorly roaming clients treated as Coverage Hole false


Detection of poorly roaming clients, treated as Coverage Hole false positives

Use other APs’ metrics to determine if a client is associating sub-optimally

If so, do not increment the NumFailedClients counter of the AP the poorly roaming client associates to

Consequently, CHDM-induced Tx increase due to clients’ poor roaming is avoided


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Cisco WCS RRM Dashboard

FeaturesAPs with mostAPs with most channel changes

APs running at maximum power

APs with coverage hole events

Top channel


change reasons

RRM related configuration mismatches across all controllers in RF Group

RRM Dashboard

ObjectiveIdentify trouble spotsIdentify trouble spots

Simplify troubleshooting of RRM-related events

ContentAPs with most channel changes

APs running at maximum power




Top channel change reasons

RRM-related configuration mismatches across all controllers in RF Group


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RRM Dashboard—Main Screen (1 of 3)Visibility into RF Groups


Quick Snapshot of the Network, and the Reasons Behind a Certain Event, Such as, Channel Changes

RRM Dashboard—Main Screen (2 of 3)Go Right into the Details of What

Configuration Mismatches Have Been Detected Across WLCs in an RF Group

Get an Instant Look into Potential Problems with APs Running “Hotter” Than Usual



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RRM Dashboard—APs at Max Power

Notice the “Sort Order” in Each of These Screens to Understand How

Items on Each Page Are SortedItems on Each Page Are Sorted


Excludes APs That Are Down, But Includes APs That Have Statically

Been Assigned With Tx Power Level 1

RRM Dashboard—APs with Most Channel Changes

“S t O d ”“Sort Order” with Multisort



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RRM Dashboard—RF Group Members’ Configuration Mismatch


Quickly Identify the (Potential And Unintentional) Mismatch of RRM-Related Configuration Across

All Controllers in a RF Group

RRM Dashboard—APs Reporting Coverage Holes

Perhaps There’s Not Enough Coverage in These Areas if the Same

AP Is Seen Here Often, or ReportsAP Is Seen Here Often, or Reports Multiple Events in a Short Span



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Cisco Spectrum IntelligenceDetect, Classify, and Locate RF Interference

Cisco WCS

Cisco WLAN Controller

LAN/WANNetwork

Wireless/WiredNetwork


Cisco AironetAccess Points

Cisco-Compatible Client Devices Spectrum Expert Detected Incompatible and Interfering Devices

Cisco Spectrum Expert Sensors

Spectrum Intelligence Actionable Information

What’s UsingMy Spectrum


What’s BeingAffected


41

Sensor Summary



Location of Sensorand Area of Coverage




42






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WCS 4.2 Spectrum Intelligence Configuration

In order to integrate a Cisco Spectrum Expert, you will need a Cisco WCS Spectrum intelligence License for Sensors

Cisco part number WCS-ADV-SI-SE-10

Add this license through the WCS help dialog

Add Spectrum Experts


“RF Matters”



44

Q and A


Recommended Reading

Continue your Cisco Live learning experience with further reading from Cisco Press

Check the Recommended Reading flyer for suggested books


Available Onsite at the Cisco Company Store


45

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Links

Farpoint Tech Note: Evaluating Interference in Wireless LANs: Recommended Practice (PDF; 220 KB)

Farpoint Tech Note: Interference and Metro Scale Wi Fi Mesh NetworksFarpoint Tech Note: Interference and Metro-Scale Wi-Fi Mesh Networks(PDF; 98 KB)

Farpoint Tech Note: The Effects of Interference on Video Over Wi-Fi(PDF; 100 KB)

Farpoint Tech Note: The Effects of Interference on VoFi Traffic (PDF; 88 KB)

Farpoint Tech Note: The Invisible Threat: Interference and Wireless LANs(PDF; 83 KB)

Farpoint Tech Note: The Effects of Interference on General WLAN Traffic


Farpoint Tech Note: The Effects of Interference on General WLAN Traffic(PDF; 88 KB)

Protecting Wi-Fi Networks from Hidden Layer 1 Security Threats (PDF; 7 MB)

RF Spectrum Policy: Future-Proof Wireless Investment Through Better Compliance

20 Myths of Wi-Fi Interference


46


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