spectrum management best practices in a gigabit wireless world

Advanced RF properties at your disposal to improve Enterprise WLAN deployments and spectrum quality BRKEWN-3010

Jim Florwick

Platform TME – Wireless

CiscoLive 2014 Milan

Cisco and/or its affiliates. All rights reserved. Presentation_ID Cisco Public

House Keeping Notes – Wednesday April 16, 2014

Thank you for attending Cisco Connect Toronto 2014, here are a few housekeeping notes to ensure we all enjoy the session today.

Please ensure your cellphones are set on silent to ensure no one is disturbed during the session

I will take questions during the session, but may ask that your hold it if we’re ahead of the material

2


What We’re Going to Cover

3

How important is the RF? – The Physical Layer – we will focus exclusively on the physical

Site Survey – When was the last time a survey was done?

Tools – A word about tools

– Prime Planner, Ekahau, AirMagnet, Spectrum analysis

What are your Priorities?

RRM – RF Grouping

– Dynamic Channel Assignment

Tuning – RRM, Client Link, Band Select, HDX – RX_SOP/SmartRoam, RF Profiles

Summary


By The End of This Session

You should understand – Where to get information

– How to evaluate that information and use it

– Understand what tools and techniques are available to solve specific issues

– Use the information presented to create an action plan for change

– Improve your networks capacity and your users lives

4

Wireless Trends- What’s Your Goal?


1999

Wireless Evolution From Best Effort to Mission Critical

Hotspot System

Management Scalable

Performance

802.11n/OBSS

Self Healing &

Optimizing

802.11ac Gigabit Wireless

HS2.0

HDX

1999 2005

2007 2010 2013


The changing RF landscape

7

Protocol Date Characteristics Spatial

Steams

20 MHz

Channels

802.11 1997 1,2 Mbps, infra Red, spread and DSSS,

802.11FH 2.4 GHz

1 1

802.11b 1999 1,2,5.5,11 Mbps, DSSS 2.4 GHz 1 1

802.11a 1999 6,9,12,18,36,48,54 Mbps – OFDM – 5 Ghz 1 1

802.11g 2003 6,9,12,18,36,48,54 Mbps OFDM 2.4 GHz 1 1

802.11n 2005 MCS 1-15-23 1-3 SS, OFDM, 20,40 MHz, 2.4

and 5 GHz

1-3 1-2

802.11ac 2012 1-8 SS MCS 1-9, OFDM, 20-40-80-160 MHz, 5

GHz

1-8 1-8


2013 is the first year we’ve seen higher 5 GHz adoption rates

CiscoLive and Mobile World Congress - high tech shows –

SuperBowl different crowd 98.5% 802.11n

0.1

38 40

55

29

50 60

99

62 60

45

71

50 40

0

20

40

60

80

100

1205 GHz

2.4 GHz

98% 802.11n for 2012 and 2013!


Key Reports – Cisco Prime

Clean Air – How much of your spectrum is being used by NON Wi-Fi

devices?

Client – What protocols are your client using? Unique Client Summary – should be a frequent

reference

Device – Channel Utilization – how much spectrum do you have?

Security Are Rogue Access points using your spectrum? Which AP’s hear them – how loud?

The above reports will tell you what/who is using your spectrum, how efficiently you are using your spectrum and how much you have left

9

Deploying with Spectrum in Mind


Deploying with Spectrum in Mind

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

Evaluate the existing application requirements, available spectrum and Client types/mix

Focus should be on fixed infrastructure – AP placement

– Density is important = capacity

– Protocols supported

– Rates supported

– Interference sources

Mitigating issues

Planning tools

Designing for Sustainable Spectrum Management


About Site Surveys

When was the last time you did a site survey?

– What where the design goals when that survey was done?

– Coverage or Capacity model?

– Client/AP types and technology?

Technologies Change – how many devices/clients where on your network the last time you did a survey

What are your design Priorities? What where they when you last did a survey?

You don’t know what you don’t know and not all 802.11 technologies are complimentary – air time rules

12


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


What has not changed? 802.11 and Duty Cycle – Channel Utilization – Air Time

802.11 error recovery is limited - Still

– Retransmit a packet

– Rate shift

Duty Cycle of RF is logarithmically proportionate to Channel Utilization

Channel Utilization is Capacity

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

At a minimum – you have more users on your network this year than you did last year – and a lot more than you had 5 years ago….


How does Interference impact Wi-Fi? Separating the FUD from the Fact’s

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 – ED – quick – low power - prone to false positives – 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


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 Fact’s

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


802.11 and Duty Cycle – Channel Utilization

802.11 error recovery is limited

– Retransmit a packet

– Rate shift

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

For a deep dive on CleanAir and it’s best in class features see –

BRKEWN-3010 Orlando, Fl. June 2013

• Available on CiscoLive365

https://www.ciscolive.com/online/connect/sessionDetail.ww?SESSION_ID=7807&backBtn=true



RRM – Radio Resource Management


RRM—Radio Resource Management

What are RRM’s 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


RRM Monitors the RF Group

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 (802.11—rogue APs)

– Signal – (our AP’s)

– Load


How Does RRM Do This?

DCA—Dynamic Channel Assignment

–Each AP radio gets a transmit channel assigned to it

–Changes in “air quality” are monitored, AP channel assignment changed when deemed appropriate (based on DCA cost function)

TPC—Transmit Power Control

–Tx Power assignment based on radio to radio pathloss

–TPC is in charge of reducing Tx on some APs—but may also increase Tx by defaulting back to power level higher than the current Tx level

CHDM—Coverage Hole Detection and Mitigation

–Detecting clients in coverage holes

–Deciding on Tx adjustment (typically Tx increase) on certain APs based on (in)adequacy of estimated downlink client coverage


RF Grouping Neighbor Messages = OTA – Over The Air - RF analysis

Neighbor AP messages are sent every 60 seconds at highest power and lowest supported data rate

Neighbor Messages are used by receiving APs and their WLCs to determine how to create inter and Intra-WLC RF Groups and Physical RF Neighborhoods

Each AP listens for other AP’s neighbor messages – and if it’s RF Group name matches – the message is forwarded to it’s controller and ultimately to the RF Group leader

A list is maintained for each AP in the RF Group of who heard his neighbor messages and how loud

Neighbor messages are

sent from each AP to

multicast address

01:0B:85:00:00:00

For a deep dive on the concepts of grouping, Neighbor Discovery, and collection of off channel metrics used in RRM algorithm’s – please read – Radio Resource Management (RRM) RF Grouping

• Part of the 7.4 RRM Design Guide presently under revision

http://www.cisco.com/en/US/docs/wireless/controller/technotes/7.4/RRM_DG_74.pdf

http://www.cisco.com/en/US/docs/wireless/controller/technotes/7.4/RRM_DG_74.pdf


RRM—DCA— Dynamic Channel Assignment

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

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

34

RF Channel “64”

RF Channel “44”

RF Channel “100”

Analyzes and Optimizes

Channel assignments

Coordinates 20,40, and 80 MHz OBSS

assignments Using OTA measurements

What It Does


Who calculates DCA – It runs on the RF Group

Leader 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 on some radios, if appropriate

What criterion is evaluated: – RSSI-based Cost Function that

captures overall interference (including non-802.11 noise) on a per channel basis

Monitor=>Access Points=>Detail


DCA represents each channel using essentially a compound signal to noise ratio. This is called a cost metric or CM.

Contributions to this metric are

– Signal – Our AP’s TX and RX neighbor

– Noise – Non Wi-Fi interference

– Interference – Managed and unmanaged rogues

– Load – Cisco Channel Utilization

You can manipulate what you want to contribute to the metric – by default Signal, Noise, and Interference are selected.

Wireless=>802.11a/b=>RRM=>DCA


• Defaults are generally best

• Avoid Foreign AP Interference

If enabled – places a higher penalty on rogue devices

Is to encourage DCA to work around the neighboring AP

Encourages good neighbor borders

Can cause a lot of channel changes if enabled with a lot of transient rogue devices – disable if this is the case

• Load – disabled. This accounts for Cisco AP load only. Can cause a lot of channel changes in a heavily used network. Wireless=>802.11a/b=>RRM=>DCA


DCA evaluates the Cost Metric to determine optimal channels for the network

The user defined threshold – DCA Sensitivity Threshold – allows customization of the algorithm

The threshold is a Hysteresis to dampen DCA function

If sensitivity is medium for 2.4 GHz then in order for a channel change to be made the new channel must be 10 dB better than the current channel or no change will occur.

Version Band Low Medium High

6.0 + 2.4 GHz 5 dB 10 dB 20 dB

5 GHz 5 dB 15 dB 20 dB


DCA Example

What changes first is the CPCI selection process, randomization prevents pinning –

For a given CPCI, calculations permit changing first hop channels

Second hop channels considered

Solution is submitted to NCCF

CPCI and 1st neighbors are removed from the CPCI list

Next randomized CPCI is selected


Selection of 20 MHz – all AP’s set to 20 MHz

Selection of 40 MHz – All 40 MHz capable AP’s set to 40 MHz

– 20 MHz only AP’s will remain 20 MHz

Selection to 80 MHz – all 80 MHz capable AP’s set to 80 MHz

– Others – 802.11n at 40 MHz, and 802.11a at 20 MHz

Wireless=>802.11a/b=>RRM=>DCA


Using the example of an 80 MHz OBSS – (Overlapping BSS)

AP-AC wins contention on my primary channel and will send data on that channel and 3 other bonded channels.

The VHT header tells all 802.11AC stations that I’m using an 80 MHz OBSS and even tells what 20 MHz sub channels it’s using

But What of the lowly 802.11a station, or the 802.11n (HT) station who don’t speak 802.11ac and it’s fancy VHT language?


Never Fear – LBT (Listen before Talk) to the rescue – CCA! (Clear Carrier Assessment)

CCA thresholds where adjusted in the 802.11ac specification to allow Overlapping BSS and IBSS stations coexist by adjusting the contention requirements for Sub Channels

In the table above – you can see that all 3 protocols have equal contention on the primary.

Any primary operating within a secondary 20 or 40 will loose contention

Any secondary 20 operating in a secondary 40 will win contention over other secondary's!

Protocol Primary Secondary 20 MHz Secondary 40 MHz

802.11a -82 dBm

802.11n -82 dBm -62 dBm (20 dB liberty)

802.11ac -82 dBm -72 dBm (10 dB liberty) -76 to -79 (3-6 dB liberty)


The 802.11AC specification allows for an RTS to be sent on all sub channels as an 802.11a frame, and expects a CTS if a primary channel is assigned to one of the sub channels

– The specification says that RTS is optional, but CTS is mandatory

– Will clients implement this?

Even when the secondary40 channel is

occupied by a transmission, an 80 MHz

11ac AP can select to transmit 40 MHz

for the time being, thus the system still

fully utilizes the channel. (The

placement of the primary on which half

of the secondary40 is no longer a

critical concern.)


The level of constructive coexistence among OBSS’s is based on these criteria:

– Fair channel access

– Fairness between 11ac and 11ac is neutral

Fairness between 11ac and legacy (11n and 11a)

Number of hidden nodes decreases

Number of collision decreases

Overall performance and efficiency increases


In simulations and analysis, the general level of constructive coexistence decreases between two OBSSs in the order for these possible scenarios:

1. Primary and secondary20 channels mismatched

2. Primary channel on secondary40 or secondary 80 channels

3. Primary channels aligned

Cisco and/or its affiliates. All rights reserved. Presentation_ID Cisco Public 49

Channel 40,44

802.11n 802.11ac

Channel 48,52,40,44

-54 dBm

120 Mbps

50 Mbps

-64 dBm

50 Mbps

120 Mbps

-74 dBm

220 Mbps

10 Mbps

-84 dBm

210 Mbps

90 Mbps

Cisco and/or its affiliates. All rights reserved. Presentation_ID Cisco Public 50

Channel 48,52

802.11n 802.11ac

Channel 48,52,40,44

-54 dBm

120 Mbps

50 Mbps

-64 dBm

120 Mbps

50 Mbps

-74 dBm

120 Mbps

50 Mbps

-84 dBm

200 Mbps

90 Mbps


How does DCA keep track of all the other AP’s and the channels their using?

Remember the DCA cost Metric?

Add Bias to a given channels CM to reinforce good channel solutions

Bias values match the given 3 performance scenarios – B1, B2, B3 for our AP’s and R1, R2, R3 for rogues increasing the bias for lower coexistence values

For instance - Not using Channel 60, and the resulting CM for channel 60 is +128!


DCA will search for a 20, 40, 80 MHz solution for each AP – and only populate up to the AP’s capabilities

DCA channel Width settings determines the DCA mode

The AP Type determines the possible Channel Widths

DCA search’s for 20, then 40, then 80MHz channel widths and presents the solution as a grouping of cost metrics

Metrics for the same channel– can and will change for the channel width solution searched due to BIAS settings


Airewave Director: metrics20 After Normaliz( 52, -81.68)( 56, -74.51)( 60, 128.00)( 64, -55.38) <snip>



*RRM-MGR-5_0-GRP: Sep 23 15:59:38.556: 64:d9:89:42:29:50 <snip>

Note – there are 3 similar but different answers - It is

3 different questions with 3 different set’s of rules. What determines

Which answer is used?

*RRM-MGR-5_0-GRP: Sep 23 15:59:38.551: 64:d9:89:42:29:50 Airewave

Director RRM Chan Assignment Mode: 2 Lrad Capability: 2 DCA Channel Width:

2 0= 20 MHz

1 = 40 Mhz

2 = 80 Mhz


802.11ac and 80 MHz - lets see what this baby can do!

Likely already a full spectrum (the network was already there right?) – Using DFS channels already?

– Already have 40 MHz assigned for 802.11n?

Likely DCA is at medium Sensitivity 10 dB Hysteresis – Changing Channel Width – is a major change

– Expanding some channel Width’s to 80 Mhz and others to 40 Mhz is not trivial

– Don’t limit the possible solutions to within 10 dB!


5 GHz 20/40/80/160 MHz Channels

56

36

40

44

48

52

56

60

64

68

72

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80

84

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92

96

100

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136

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181

20

40

80

160

US

Europe

20

40

80

160

Indi

a

20

40

80

160

China

Existing Channel New Channel

UNII-2 UNII-1 NEW! UNII-2 NEW! UNII-2 UNII-3 NEW!

5250

MHz 5350

MHz

5470

MHz 5725

MHz

5825

MHz

5925

MHz


Feature Benefit

256-QAM 5/6 coding 30% faster – at any #ss

Rate vs Range – significantly

increased

Faster speeds – further from the AP –

faster overall cell – less airtime

consumed

802.11ac – ONLY 5 Ghz Finally,Seriously, overdue….

Optional 802.11n Specifications

Removed – discarded - junked

Less implementation choices = less

client variability

Manufacturers already committed to

implementation

Many already delivering product


Do you have spectrum available for 80 Mhz? – Evaluate by Regulatory

Do you use 40 MHz for 802.11n AP’s today? – If not – why not?

– Does it make sense to use 80 MHz?

Plan the Implementation – and understand that this is a Major Change to your existing spectrum plan

Let DCA help you


Best Practices for Implementing 802.11ac

Decide what Channel Width you will use

Implement new hardware –

Initialize DCA in Startup Mode – FROM the RF group Leader(s)

Remember – all of this is 5 GHz only!

7.3 and above – from the CLI - Config 802.11a/b channel global restart

Managing Efficiency


RX Utilization 36

TX Utilization 7

Channel Utilization 96


Channel Utilization – what is it?

Channel Utilization is the physical – and the logical Air Time consumed

It is – physical signal in the air above CCA

It is - the logical CW and NAV

It is – All RF in the air – ours as well as rogues – if it’s 802.11 and we hear it – it counts

It is the metric which represents the AP’s TX_op in the current channel

And- it represents the whole channel – not the AP’s utilization

Root Cause for Channel Utilization must be isolated

– Self Interference – SSID’s, Data Rates, AP isolation vs Density – control with Configuration

– Non – Wi-Fi interference – possibly controllable

– Rogue Devices/networks – configuration management


Spectrum Is a Shared Finite Resource

Understand Protocol Selection 802.11 b/g/a/n/ac and Duty Cycle—Important? Why?

75

0

500

1000

1500

2000

2500

3000

3500

6 12 36 54 130 173.3 300 540

64 Bytes

128 Bytes

256 Bytes

512 Bytes

1024 Bytes

2048 Bytes

Data Bytes

Time μS

Data Rate - Mbps

HT/VHT 40

3ss

HT/VHT 20

2ss

OFDM


Every SSID Counts!

76

Each SSID requires a separate Beacon

Each SSID will advertise at the minimum mandatory data rate

Disabled – not available to a client

Supported – available to Existing associated client

Mandatory – Client must support to associate

Lowest mandatory rate is beacon rate

Highest mandatory rate is default mcast rate


AP-3700 – Supports Client Link 3.0

So why Client Link 3.0? • ClientLink’s beamforming capability unlike the standard improves

the SNR for all clients including legacy clients.

• Because this technology does not depend on any client-side hardware or software capabilities, it works with mixed-client networks seamlessly with 802.11ac and 802.11a/n clients that co-exist on the same Access Point

• Standards based beamforming only works with .11ac clients and most of them do not support it at this time.

A real “purpose built” AP is one that can support Cellular modules, Monitor radios, Wave-2

upgrades and can future protect your investment.

We also didn’t “accidently” build the AP-3700 you might say “purpose built” includes

ClientLink innovation, Spectrum Intelligence and Quality RF performance from the center

of RF Excellence located in Richfield Ohio… Yes QUALITY DOES MATTER…


5 2.4

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

802.11?

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/n clients causing

contention

2.4GHz is prone to interference

RF Profiles


RF Profiles to Manage your RF Configurations

RF Profiles work in Conjunction with AP Groups (beginning in release 7.2)

You can create separate RF profiles for both 2.4 and 5 GHz

1 profile for each band (802.11a/802.11b) can be assigned to an AP group

What can be adjusted within a profile continues to expand with DCA expected in version 8.1

Today

– 802.11 data rates

– TPC Power Threshold and Min max Power settings

– DCA (in 8.0!)

– Coverage hole algorithm settings

– High Density – HDX configurations RX_SOP, Client Limit, Mcast data rate

– Client Distribution

82


RF Profiles – RRM – Create

RF Tuning parameters can be applied through profiles assigned in AP groups

2 Profiles per AP group – 1 ea. 2.4 and 5 GHz

Profiles must be applied on ALL WLC’s from which AP’s will be assigned (same as AP Group)

Permits control of granular groups of AP’s

We love it…

83

Wireless=>RF Profiles


Profiles : Granular Control

84

Data Rates

Load Balancing

TPC, DCA,Coverage Hole

High Density


Profiles – Applied Through AP Groups

87

Create Profiles

Create or edit AP Groups

Apply Profiles (2.4/5 Ghz) to AP groups

Assign AP’s

HDX – High Density Experience


Bigger Cells, More Users Control Cell Size by Data Rate selection and RX tuning

The Cell is the unit of bandwidth Manage the per user bandwidth

by managing the size of the Cell RF Profiles allows you to treat 2

groups of AP’s differently in order to tune the deployment to peak performance

Here are some additional tools to manage higher density encounters and win

90

167

PAX

40 PAX/per


When Coverage meets Capacity

You’ve eliminated several SSID’s

You’ve raised your data rates to fit the coverage areas

You’ve added AP’s to areas where additional coverage is needed…..

Channel Utilization won’t come down – and power is already at the lowest settings

Welcome to High Client Density

91


RX-SOP – Receive Start of Packet threshold

92

The AP has a threshold on each radio at which it logically honors a packet

Below this threshold – it is treated as noise

Above this threshold it is treated as Wi-Fi – and all the logical utilization that goes with that

When you start to add more channels for capacity – you will tune data rates and placement to decrease your transmit footprint

Use Antenna’s to focus your receive sensitivity

RX-SOP allows you to tune the receive cell size to match the Tx cell size

If you hear less – you will have less Channel Utilization


RX-SOP – (Receive - Start of Packet) – What is it?

Receiver Start of Packet Detection Threshold (RX-SOP) determines the Wi-Fi signal level in dBm at which an AP radio will demodulate and decode a packet.

The higher the level, the less sensitive the radio is and the smaller the receiver cell size will be

By reducing the cell size we can affect every thing from the distribution of clients to our perception of channel utilization

This is for High Density designs – and requires knowledge of the behavior you want to support

A client needs to have someplace to go if you ignore it on the current cell

WARNING – This setting is a brick wall – if you set it above where your clients are being

heard – they will no longer be heard. Really.


RX-SOP – Why Use It?

Reduce sensitivity to interference and noise – reduce Channel Utilization

It sharpens the cell edge – we will hear what we intend to cover

Caveats –

– You can significantly reduce coverage

– You can make it impossible for intended clients to associate or communicate with your AP

This feature is to be used in conjunction with a known design to solve a specific problems when you understand the coverage and usage of the network by the users

RX-SOP is available at the global level as well as in RF profiles – Strongly recommend applying only through profiles – to solve specific problems with HDX


RX-SOP configuration

Settings High, Medium, Low, Auto

Auto is default behavior, and leaves RX-SOP function linked to CCA threshold for automatic adjustment

Most networks can support a LOW setting and see improvement

This affects all packets seen at the receiver


Optimized Roaming- help for clients that are not so smart….

97

Optimized Roaming Disabled Optimized Roaming enabled


Optimized Roaming

Sets a threshold RSSI value and or Minimum Data rate that a client will be sent a Disassociate

Developed to support Cellular Hand Off

Global configuration of 4 Parameters available – Enable/Disable

– Interval (seconds)

– Data Rate threshold

– RSSI threshold configured through Data CHD

Trigger is Pre-Coverage hole event – set under CHDM config


Optimized Roaming configuration

Enable/Disable – Global command

Interval = #seconds between checks at the Radio

Data Rate threshold-

Used in conjunction with RSSI threshold, if set is a gating function where both data rate and rssi must be true for action – default is disabled

RSSI threshold – set through data RSSI config in Coverage at the global level, and under RRM in RF Profile


Optimized Roaming Logic

Data RSSI Data Rate Result

True Disable (default) Disassociate

True False No Action

True True Disassociate

• Uses CHDM Data RSSI for trigger Alone – decision is based on RSSI seen at the radio

• Combined with Data Rate – provides additional gate for action – and preserves CHDM Function

• If Used with Client Low RSSI check, and the higher of the two values is used (with 6 dB hysteresis).


Optimized Roaming & Low RSSI feature “WARNING”

Low RSSI check is a completely separate feature – and sets a low RSSI threshold which a client must be above to associate to the AP

Optimized Roaming has a 6 dB hysteresis built in to prevent thrashing

i.e. If Optimized roaming is set to -75, then to rejoin the AP the clients signal must improve to -69 dBm

The logic checks low RSSI – AND Optimized roaming before allowing a client to Join – and both must pass

For a deep dive on High Client Density design practices see BRKEWN-2019 RF design for the Mobile Device Explosion 2013 CL Orlando

• Available on CiscoLive365





Summary


Summary

Evaluating what the goal of your network is on a regular basis will enable you to make better design decisions

Good tools make and defend good decisions

Eliminating spectrum hogs should be first priority – strongly consider eliminating anything not OFDM all together (Legacy 802.11b)

Understand how RRM gathers information and makes it’s decisions

Allow RRM DCA to do it’s job – best practice to restart DCA after major changes to numbers, types, placements of AP’s

Not all your coverage zones have the same needs – use RF profiles!

104


Links/References

Cisco 802.11n Design and Deployment Guidelines

Cisco High Density Wireless Lan Design Guide

Cisco Client Link White Paper

Client Link testing – Miercom

Client Link 2 Testing - Miercom Report Cisco 3600e/i

10

5

http://www.cisco.com/en/US/solutions/collateral/ns340/ns394/ns348/ns736/net_implementation_white_paper0900aecd80554f8b.pdf

http://www.cisco.com/en/US/solutions/collateral/ns340/ns394/ns348/ns767/white_paper_80211n_design_and_deployment_guidelines.html

http://www.cisco.com/en/US/prod/collateral/wireless/ps5678/ps10981/design_guide_c07-693245_ps10315_Products_White_Paper.html

http://www.cisco.com/en/US/prod/collateral/wireless/ps5678/ps10092/white_paper_c11-516389.html

http://www.cisco.com/en/US/solutions/collateral/ns340/ns394/ns348/ns767/Miercom_Test_Report_Cisco_ClientLink.pdf




http://www.miercom.com/2012/03/cisco-ap3600ei-earns-miercom-performance-verified/




http://www.cisco.com/en/US/prod/collateral/wireless/ps5678/ps10981/design_guide_c07-693245_ps10315_Products_White_Paper.html


106

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prize redemption slip.

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spectrum management best practices in a gigabit wireless world

Technology

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available spectrum

spectrum analysis

spectrum quality brkewn

physical site survey

rrm rf

mbps ofdm