v1_brkewn-3013_c1 ciisco live -wireless lan

2011 Cisco and/or its affiliates. All rights reserved. Cisco Public BRKEWN-3013 1

Wireless LAN Radio: Spectrum Management Best Practices BRKEWN-3013


The Challenge Wireless Trends

Evolution of the WLAN

Deploying with Spectrum in Mind Site Survey A Word About Tools Cisco Radio Resource ManagementRRM ClientLink, BandSelect, CleanAir

What Were Going to Cover


The Challenge


You are breathing the physical layer RF reflects off things RF is absorbed by things Its 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, its a technology enabler providing

Increased productivity Creative freedom Enhanced user experienceby putting the power of the network where the user lives and works

The Dynamic Nature of Spectrum


Mobility Refers to the Client Not the Infrastructure

Radio assets are fixed devices

Autonomous AP channel and power must be set in advance

Clients move about Resource demands shift

with client location, and density

Clients Associate to AP with Strongest Signal


Even When Well Planned, Things Change

Mission critical requires HA Client technology refreshadditional device types PDAs, Tablets New neighbors?


Normal Range

Reduced Range

Degraded Range

Reduced Coverage from 20% to 80% Reduced Call Quality Most Video Rated Unwatchable

A Series of Papers on Wi-Fi Interference Concluded

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

Video Voice Data

http://www.cisco.com/en/US/products/ps9393/prod_white_papers_list.html

Does NonWi-Fi Interference Matter?


Wireless Trends


Enterprise Wireless Evolution From Best Effort to Mission Critical

System Management

Scalable Performance Self Healing &

Optimizing

Hotspot


When the students returned this year, if you asked me what percentage of students are using the Wi-Fi network I would have told you 40%. I was shocked to see 85% of them using the Wi-Fi network.

Scott Ksander September 2009 Cisco Education TAB Purdue University


Expectation for Mission Critical Wireless

IT Lacks RF Resources and

Expertise vs.

Continued Growth and Reliance

on Wi-Fi Devices

I Cant Do My Job Without Wireless. It Has to Work.

Wireless Is Best-Effort. I Cant Support a Level 1 SLA.


Deploying with Spectrum in Mind


Role of site survey is as important as everbut has evolved Evaluate the existing application requirements, available spectrum

and Clients Focus should be on fixed infrastructure

AP placement

Density is important

Protocols supported

Rates supported

Interference sources

Mitigating issues Planning tools

Deploying with Spectrum in Mind

Designing for Sustainable Spectrum Management


A Word About Tools

What you use is less important than how you use it Internal vs. external adapters

Internal adapters even the same model will have different antenna arays and placement for different model laptops External adapters can be moved with the application and provide consistent results regardless of the platform used

Use the same Tool to compare results! Recheck results from a known environment with

version updates

Free Tools Nothing is Free

How to Compare Apples to Apples


Throughput Reduction

Interference Type Near (25 Feet) Far

(75 Feet)

2.4 or 5 GHz Cordless

Phones 100% 100%

Video Camera 100% 57%

Wi-Fi (Busy Neighbor) 90% 75%

Microwave Oven 63% 53%

Bluetooth Headset 20% 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

The Impact of a Crowded Spectrum Performance at Risk in Unprotected Networks

Source: FarPoint Group


802.11 is CSMA/CA collision avoidance CCA is Clear Channel Assessment and is the listen before talk

component of Collision Avoidance

With 802.11n radios CCA is typically linked to Preamble/Start of packet

Radios are better these days (mostly) CCA - is -65 and SOP is -85 dBm for 802.11b/g/a If you can hear it above these levels you are sharing the spectrum

What Is CCA and SOP?


CCA Blocked or High

802.11n Traffic

Video Signal

Video Camera Duty Cycle 90-100%


How Does Interference Impact Wi-Fi? Separating the FUD from the Facts

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

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


802.11 and Duty Cycle Channel Utilization

Retransmit a packet Duty Cycle of interference is logarithmically 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


Deploying with RRM in Mind


What are RRMs objectives? To dynamically balance the RF infrastructure and mitigate changes

Monitor and maintain coverage for all clients

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

What RRM does not do Substitute for a site survey

Correct an incorrectly architected network

Manufacture spectrum

RRMRadio Resource Management


Continuously monitors dynamic changes in environment Collection of statistics and metrics used by DCA, TPC, and CHDM

Provides assessment of the overall RF health of the network

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

Interference (802.11rogue APs)

Signal (our APs)

Load

RRM Monitors the RF Group


Three APs Deployed in Each Foyer


Initial Measures Before and After Eliminated center 2.4 GHz radios on each floor Eliminated all but 11 Mbps Enabled Client Link Enabled Band Steering


End Result APs Moved


Case 2 RF Groups

After conducting a multi floor active site survey using a 4400 and 10 x 1140 APs, coverage looked good at power levels 2-3.

The customer then deployed 3500 series APs according to the plan, and RRM set the power levels to 6!

Whats different about the 3500?


RF Grouping


The Tell Survey Was Conducted in Separate RF Group


> - 80dBm

Wireless Controller A RF Group =

Wireless Controller B RF Group =

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

Neighbor Messages Are Sent At Full Power, Containing Information About the APs 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 Neighborhood, Channel, and Power Then Compute as a Group

About RF Groups RF Groups Are Clusters of Controllers that Share the Same RF Group Name. RF Neighborhoods Are Groups of APs that Hear Each Other


RF Neighborhood (a)

RF Neighborhood (b) RFGroup - Bob

RF Grouping and RF Neighborhoods Multiple RF Neighborhoods can exist within a

single RF Group RRM is calculated on a per RF neighborhood

basis RF Neighborhoods can be inter-controller or

intra-controller Multiple RF Neighborhoods may be formed

even when controllers share same RF Group name

RF Groups/Neighborhoods Apply per PHY Type

RFGroup - Bob

RF Neighborhood (B) RF Neighborhood (A)

RF Neighborhood (C)

RF Neighborhood (D)

RF Neighborhood (E)

Logical RF sub-group (c)

RFGroup 1 RFGroup 1

RF Neighborhood (A)

RF Neighborhood (B)

RF Neighborhood (C)


Configuring RF Grouping

By Default the RF Network Name and Mobility Domain Name Are the Same, but This Is Default Behavior

RF Group Name Is Configured From: Controller > General on the WLC GUI: Configure > Controllers > controller > System > General in WCS:


RF Grouping

By looking at the RF neighborhoods from the network perspective, you can determine which APs are literally within the same RF domain or neighborhood.

Placing like groups of APs into a separate RF group is perfectly ok, and in fact can provide much better design options


Case -3 DCA

New Building installation CU has a very high density of I-phones Main Architect good RF knowledge Without RRM channel distribution matched plan With RRM APs on same channel adjacent to one another Did not trust RRM

Channel Utilization vs. Spectrum Expert did not match

Neighbor Lists and spot check with Client card vastly different


Neighbor Message and AP Neighbors

Neighbor Messages Are Sent Every 60 Seconds to the Multicast Address of 01:0B:85:00:00:00

Did Not Trust RRM Compared the Neighbor Lists for WLC to Beacon Observations at the AP

Produced Less Trust -


Looking at the 1st floor we see two APs on the same channel

At the 2nd floor, we see 3 APs

The 3rd, we see 3 APs And the 4th we see

2 APs

But look at the APs channels as they stack!

RRM Put Adjacent APs on the Same Channel!

1st 2nd

3rd

1

6

11

4th

1


WLCCA View


AP Placement

Omni Antennas have an Elevation pattern of a donut

12 dB attenuation between floors

Customer intentionally stacked the APs to protect against direct exposure

Had these been 1130s possibly a valid argument

BUT - These Are Cisco AP 1140s


Antenna Pattern Elevation Plane 2.4 GHz

Access Point Has 3 Integrated 4 dBi (2.4GHz) Antennas


DCA 6.0 and Beyond CM= RSSI, Noise, Interference, signal, and a constant (threshold) An AP list ordered by CMs in the RF Neighborhood is created worst to best Prior to release 6.0 we solved for the worst AP CM in the RF Neighborhood 6.0 and after - DCA now operates on multiple local searches and randomly

selects CPCI (channel Plan Change Initiators) from the CPCI list and calculates optimal solutions for the CPCI and its first and second hop neighbors

The calculation completes with the NCCF function a goodness value for the group indicating positive change for the CPCI and its immediate neighborhood

Version Band High Medium Low 4.1.185.1 2.4 GHz 5 dB 15 dB 30 dB

5 GHz 5 dB 20 dB 30 dB 6.0 2.4 GHz 5 dB 10 dB 20 dB

5 GHz 5 dB 15 dB 20 dB


DCA Solution Flow

AP-5

CPCI

First Hop Neighbor

Second Hop Neighbor

Worst

Best

AP CM AP-5 25 AP-4 34 AP-6 55 AP-1 60 AP-7 63 AP-8 67 AP-23 68 AP-14 71 AP-13 73 AP-19 75 AP-24 76 AP-25 77 AP-16 78 AP-10 79 AP-15 79 AP-17 81 AP-2 82 AP-11 82 AP-20 83 AP-21 83 AP-22 84 AP-9 85 AP-18 87 AP-3 90 AP-12 91

AP-5 AP-6

AP-15 AP-11

AP-9

AP-10 AP-18

AP-19

AP-16

AP-21

AP-22

CPCI and First Hop Neighbor, Channel Change Is Allowed

The Impact on the Second Hop Neighbor Is Considered in the Calculation, but No Channel Change Is Permitted

A CPCI List Is Created of All APs in the Local RF Neighborhood


DCA Solution Flow

AP-5

CPCI

First Hop Neighbor

Second Hop Neighbor

Worst

Best


AP-5 AP-6

AP-15 AP-11

AP-9

AP-10 AP-21

AP-19

AP-16

AP-22

AP-18

NCCF Is Calculated on the Entire Group for Each Channel Plan Calculated A Plan Is Selected


DCA Solution Flow

AP-5

CPCI

First Hop Neighbor

Second Hop Neighbor

Worst

Best


AP-5 AP-6

AP-15 AP-11

AP-9

AP-10

X X

X

X X

X

The CPCI and Its First Hop Neighbors Are Removed from the CPCI List


DCA Solution Flow

AP-5

CPCI

First Hop Neighbor

Second Hop Neighbor

Worst

Best

AP-2 AP-19

AP-8 AP-7

AP-18

AP-22

AP CM AP-4 34 AP-1 60 AP-7 63 AP-8 67 AP-23 68 AP-14 71 AP-13 73 AP-19 75 AP-24 76 AP-25 77 AP-16 78 AP-17 81 AP-2 82 AP-20 83 AP-21 83 AP-22 84 AP-9 85 AP-18 87 AP-3 90 AP-12 91

The Process Begins Again with the Remaining APs on the List Randomization Is Applied for Selection of the Next CPCI


Redesigned DCA Benefits

Faster Convergence calculations for an RF group are much faster can complete 6 iterations in the previous time it took for one.

More Granular more flexible for the dynamic needs of an RF Neighborhood

System wide View every APs assignment is known and managed by a centralized resource

Much better for integrating Spectrum Intelligence and makes CleanAir integration exciting.


Back to Our Use Case -

Dont like RRMs answer what can be done? Change the question!

Move an AP on Either Floor Override Global for Just 1 AP and Let DCA Recalculate!


Case 4 Transmit Power Control

New construction Predictive site survey done for Vocera 11.b badges Predictive survey called for 25 30 foot spacing Power at 13 dBm power (power level 3) to cover TPC forced APs to power level 7 Result was coverage holes for Voice


Voice Readiness Tool Results


New Building Borders with Existing Building and AP1130 Installation


Add APs Fill Coverage Holes without Increasing Co-Channel Interference


Assume an APs TX neighbors hear it at the following RSSI levels (listed in decreasing order; units are [dBm])

45, 55, 67, 75, 78, 80

For third loudest neighbor RSSI_3rd > TPC_Threshold TPC_Threshold = 70 dBm

TPC would recommend a Tx power decrease Important: The RSSI_3rd >? TPC_Threshold criterion only

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

The delta between the current and the recommended Tx

Hysterisis for a TX Power increase is 3 dB

Hysterisis for a TX Power decrease is 3 dB

TPCHow It Works


There are two main TX power scenarios that can trigger an increase There is no third neighbor will result in maximum power

TPC Equation evaluates the recommended Tx_Ideal 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 power increases happen immediately

TPCHow It Works


Several changes to how power is calculated where made in the 6.0 MR-1 release

A smoothing algorithm was added that takes into account the power levels of the next neighboring APs and their neighbors

In situations where there is no third neighbor the old algorithmic behavior was to default to power level 1 (no RSSI_3rd)

With these changes, if there is no third neighbor TPC looks for any neighbors heard above the TPC threshold, and interrogates those neighbors that are heard above the current TPC Threshold

An average of averages is factored against TPC recommended power

That average is used to modify the recommendation from TPC

TPC 6.0 MR1 Algorithm Changes


AP-2 RX-TX Neighbor List

TPC - Example

AP-1

AP-2 AP-3

AP-4

AP-6

AP-5

Neighbor RSSI

ap2 - tx -45 dBm

ap6 - rx -55 dBm


Neighbor RSSI Power

Ap3 -45 dBm 5

Ap6 -55 dBm 4

Ap4 -57 dBm 5

ap5 -79 dBm 3

Neighbor RSSI Power

Ap2 -55 dBm 4

Ap3 -58 dBm 5

Ap4 -68 dBm 3

ap5 -71 dBm 4


Ap1 has 2 neighbors, ap2 and ap6 Ap2 has three neighbors above TPC Threshold of -70 Ap6 has three neighbors above TPC Threshold of -70 Average the power settings for all 6 neighbors 4+5+3+5+4+5=26 26/6=4 Use power level 4 in smoothing algorithm for final TPC recommendation of 3 for AP1


From the controller GUI select- Wireless=>802.11a/b=>RRM-TPC

TPC 6.0 MR1 Min/Max Power GUI Configuration

Note: Ensure You Select Apply in the Upper Right Hand Corner of the Screen to Save.


Facts

At static power level 3 no clients on the network average channel utilization was 30-40%!

At power level 7- Utilization was much lower at 10% more representative of what the unloaded network should look like

Three options under current RRM Add more APs too late

Split RF group into new group

Risky live hospital borders 1 full side of the new building separation was 6 meters

Use TPC Min Max settings to raise power levels in this building

Better less risk of affecting neighboring APs


Use TPC Min/Max

Set TPC Min/Max to 9 dBm and 6 dBm Network settled at power level 5 Eliminated 1, 2 Mbps APs stayed at power level 5 Channel Utilization Dropped Voice Survey showed good coverage


TPC Min/Max Power GUI Configuration From the controller GUI select- Wireless=>802.11a/b=>RRM-TPC

Note: Ensure You Select Apply in the Upper Right Hand Corner of the Screen to Save.


5 2.4

Optimized RF Utilization by Moving 5 GHz Capable Client Out of the Congested 2.4 GHz Channels

802.11n

BandSelect Access Point Assisted 5 GHz Band Selection

Dual-Band Client Radio 2.4/5GHz

Discovery Probes Looking for AP

Discovery Response

Solution BandSelect Directs Clients to 5 GHz Optimizing RF usage

Better usage of the higher capacity 5GHz band Frees up 2.4 GHz for single band clients

Challenge Dual-Band Clients Persistently Connect to 2.4 GHz

2.4GHz may have 802.11b/g clients causing contention

2.4GHz is prone to interference


BandSelect Configuration Per-SSID Override (Cont.)


802.11a/g Client Connection Not Optimized, Creates Coverage Hole

The Problem Beam Strength Not Directed to Client

802.11n

802.11a/g Beam Strength X


Intelligent Beam Forming Directs Signal to Improve Performance and Coverage for 802.11a/g Devices

Beam Forming 802.11a/g

802.11n

Up to 65% Improvement

The Solution Cisco Innovation: ClientLink


Higher Throughput per 11a/g Device

No Connection without

ClientLink

Throughput vs. Distance

Test: 802.11a/g Device with 802.11n Network Source: Miercom

Up to 65% Increase in Throughput

13.6%

87.7% 70.4%

89.5%


Test: 802.11a/g Device Measured at 16 Antenna Orientations with 802.11n Network Source: Miercom

Faster data transmission, less retries = more efficient use of RF channel.

Faster 11a/g transactions opens airtime for 11n devices, providing them improved experience

Higher System Capacity Up to 27% Improvement in Channel Capacity

Channel Util of 74.2% Channel Util of 45.2%


Detect and Classify

What Is CleanAir Technology?

Cisco CleanAir

High-Resolution Interference Detection and Classification Logic Embedded into Ciscos 802.11n Radio ASIC. Inline Operation with no CPU or Performance Impact.

100

63

35

97

90

20

CleanAir Radio ASIC Uniquely Identify and

Track Multiple Interferers Assess Unique Impact to

Wi-Fi Performance Monitor AirQuality


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 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 occure

Wi-Fi and Spectrum Knowledge Why Is Silicon Important?


High Resolution Spectral Advantage

Typical Wi-Fi Chipset Spectral Resolution at 5 MHz

Cisco 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

Pow

er

Pow

er

The Industrys ONLY In-Line High-Resolution Spectrum Analyzer


Benefits of CleanAir Technology

Self Healing and Optimizing

Forensics for Troubleshooting

Wireless Security

Policy Enforcement


Self Healing and Optimization

PERFORMANCE AIR QUALITY

Wireless LAN Controller

11

6

1

RRM

Channels 11, 6 and 1 Are Optimized for Maximum Performance and Minimum Interference





11

1

RRM

6

Channels 11, 6 and 1 Are Optimized for Maximum Performance and Minimum Interference

Interference on Channel 6. Air Quality Is Affected. RRM Is Browsing the List of Preferred Channels to Resolve Conflict

11 6 1

Scanning Available Channels





11

1

RRM

11 6 1 Changing to Channel 11

6 11

X Conflict Resolved. Information Is Being Relayed to RRM. Conflicting Channel Is Blocked from Future Use.



Persistent Device

Avoidance Self Learning to Increase Reliability

Event Driven

RRM CH 1 CH 1 CH 11 CH 1 Self Healing to Avoid Wi-Fi Degradation

Interference Aware RRM Maximizes Performance by Avoiding Interference


RF Matters


Q&A


Cisco CleanAir solutions

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

Farpoint 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 (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

Links


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v1_brkewn-3013_c1 ciisco live -wireless lan

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