dynamic channel assignment algorithm interval

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Configuring DCA

16 Saturday Mar 2013

Posted by nayarasi in RRM

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Dynamic Channel Assignment (DCA) handled by RF group leader for a particular RF group. DCA algorithm takes following information into account

1. Load Measurement (Every AP measure the % total time occupied by Tx or Rx 802.11 frames) 2. Noise (APs calculate noise value on all serviced channels) 3. Interference (APs report on % medium taken up by interfering 802.11 transmission) 4. Signal strength ( RSSI of neighbor messages are heard)

Based on these metrics, if the worst performing AP will benefit by at least 5dB or more a channel change (DCA) will take place. The decision of change channel is also weighted to prevent mass change within RF group. Less client AP will more likely to change channel.

When a AP first boot up (out of the box) it transmit on CH1 in 802.11b/g radio and CH36 on 802.11a radio. Even AP reboots afterwards it will remain on the same channel until DCA occurs.

There are two scenarios in DCA could impact wireless network negatively. “ Pinning ” & “ Cascading ” are those two.

Pinning occurs when DCA algorithm could find a better channel plan for some radios in RF group, but is prevented from pursuing such a channel plan because worst radio in the network does not have any better channel options. The worst radio in RF group potentially prevent other radios in the group from seeking better channel plan. The larger the network, the more likely pinning becomes.

Cascading occurs when one radio’s channel change results in successive channel changes to optimize remaining radios in the RF neighborhood.Optimizing these radio could lead to their neighbors and their neighbor’s neighbors having a suboptimal channel plan and triggering their channel optimization. This could leads to a network instability.

Since WLC code 6.0 DCA algorithm redesigned to address both pinning & cascading.

1. Multiple local seaches DCA serach algorithm perform multiple local seraches initiated by different radios rather than performing a single global search driven by a single radio) 2. Multiple Channel Plan Change Initiators (CPCI) Previously , the single worst radio was the sole initiator of a channle plan change. Now each radio within RF group is evaluated and prioratized as potential initiators. Intelligent randomization of the resulting list eliminates the potential for pinning. 3. Localization For each CPCI radio, the DCA algorithm performs a local search for a better channel plan, but only CPCI radio itself and its one-hop neighboring AP are actually allowed to change the current Tx channels 4. Non RSSI based cost metric. A cumulative cost metric measures how well an entire region, neighborhood or network perfrom with respect to given channel plan.

You can configure DCA in 3 ways, “Automatic” , “Freeze (on-demand)”, “Off”

Automatic is the default setting where DCA runs every 10 min for 10 times once controller boots up. Then you can anchor it to certain time of the day & repeat specified time interval.

In Freeze mode no RF changes will made until you click “Invoke Channel Update Now” button. You need to remember it will not run immediately & it will run next 10 min interval.

Here are the other settings in the menu.

1. Avoid Foreign AP interference: Enabled by default. When enabled the co-channel interference metric is included in DCA calculations. For 802.11a this is good to enable as there are multiple non overlapping channels to change. But in 802.11b/g there are only 3 non overlapping channels and always there will be co-channel interference. So you need to careful when to tick this box for b/g.

2. Avoid Cisco AP Load: Disabled by default. When enabled, the client load on an AP is taken into consideration before making a channel change. It is good idea to tick this in order to prevent channel change for large client associated AP.

3. Avoid non-802.11 noise: Enabled by default. When enabled non-802.11 interference is taken into consideration.

5. Channel Width: If you are using channel bonding in 5GHz select 40MHz. In 2.4 GHz it should be always 20MHz

6. Avoid check for non-DFS channel: Disabled by default. When enabled controller avoid checks for non-DFS channels. (dynamic frequency channels). Config guide (7.0.116.0) state this only required for outdoor mesh deployment. So we can leave this disabled

7. DCA Channel List : You can select/de-select channels you want to consider for DCA algorithm. If you want to include Extend UNII-2 channels tick that box as well.

Make sure you disable the radio band before make changes & enable it once you do that.

1. RRM Basics 2. Configuring RRM 3. Configuring TPC 4. Configuring CHD 5. Configuring ClientLink 6. Override RRM 7. 8. Rogue Access Point Detection

Performance issues and algorithms for dynamic channel assignment

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Vidyarthi D Singh S (2015) A Heuristic Channel Allocation Model Using Cognitive Radio Wireless Personal Communications: An International Journal 10.1007/s11277-015-2824-1 85 :3 (1043-1059) Online publication date: 1-Dec-2015 https://dl.acm.org/doi/10.1007/s11277-015-2824-1
Lavén A Kassler A Brunstrom A Landfeldt B Igartua M Prakash R Li C (2013) Performance evaluation of the anypath routing and forwarding mechanism AP-OLSR Proceedings of the 16th ACM international conference on Modeling, analysis & simulation of wireless and mobile systems 10.1145/2507924.2507934 (81-90) Online publication date: 3-Nov-2013 https://dl.acm.org/doi/10.1145/2507924.2507934
Yang J Manivannan D (2013) Performance Comparison of Two Channel Allocation Strategies in Cellular Networks Wireless Personal Communications: An International Journal 10.1007/s11277-012-0698-z 70 :1 (353-372) Online publication date: 1-May-2013 https://dl.acm.org/doi/10.1007/s11277-012-0698-z
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Singh H Kumar S (2012) Dispatcher Based Dynamic Load Balancing on Web Server System International Journal of System Dynamics Applications 10.4018/ijsda.2012040102 1 :2 (15-27) Online publication date: 1-Apr-2012 https://dl.acm.org/doi/10.4018/ijsda.2012040102
Vidyarthi D Khanbary L (2011) Multi-objective optimization for channel allocation in mobile computing using NSGA-II International Journal of Network Management 10.1002/nem.763 21 :3 (247-266) Online publication date: 1-May-2011 https://dl.acm.org/doi/10.1002/nem.763
Yang J Manivannan D (2005) An Efficient Fault-Tolerant Distributed Channel Allocation Algorithm for Cellular Networks IEEE Transactions on Mobile Computing 10.1109/TMC.2005.79 4 :6 (578-587) Online publication date: 1-Nov-2005 https://dl.acm.org/doi/10.1109/TMC.2005.79
Yang J Jiang Q Manivannan D Singhal M (2005) A Fault-Tolerant Distributed Channel Allocation Scheme for Cellular Networks IEEE Transactions on Computers 10.1109/TC.2005.71 54 :5 (616-629) Online publication date: 1-May-2005 https://dl.acm.org/doi/10.1109/TC.2005.71
Daniels K Chandra K Liu S Widhani S (2004) Dynamic channel assignment with cumulative co-channel interference ACM SIGMOBILE Mobile Computing and Communications Review 10.1145/1052871.1052872 8 :4 (4-18) Online publication date: 1-Oct-2004 https://dl.acm.org/doi/10.1145/1052871.1052872
Narayanan L Tang Y (2004) Worst-case analysis of a dynamic channel assignment strategy Discrete Applied Mathematics 10.1016/j.dam.2003.02.002 140 :1-3 (115-141) Online publication date: 15-May-2004 https://dl.acm.org/doi/10.1016/j.dam.2003.02.002
Lawlor M White T Rosenschein J Wooldridge M Sandholm T Yokoo M (2003) A self organizing social insect model for dynamic frequency allocation in cellular telephone networks Proceedings of the second international joint conference on Autonomous agents and multiagent systems 10.1145/860575.860789 (1048-1049) Online publication date: 14-Jul-2003 https://dl.acm.org/doi/10.1145/860575.860789

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dynamic channel assignment algorithm interval

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What is Cisco DCA and how does it work with RRM.

This episode is sponsored by Metageek

Cisco RRM DCA – Dynamic Channel Assignment

DCA, or Dynamic Channel Assignment, is a core component of Cisco Radio Resource Management (RRM). It runs a critical algorithm which dynamically changes an access points (AP) client serving channel based on multiple parameters, collectively called a Cost Metric. To really get an understanding of Cisco RRM, start with our previous episode on Cisco NDP .

DCA is configured under 802.11a/n/ac (5 GHz) and 802.11b/g/n (2.4 GHz)

Channel Assignment Method

The first thing you will notice is the Channel Assignment Method of Automatic, Freeze, or Off.

Automatic will run the DCA algorithm at the define Interval which is every 10 minutes by default. The anchor point is used to set the time of day the DCA algorithm would start.

For less frequent channel changes, increase the interval.

Keep in mind that clients will be disconnected briefly for a channel change.

Freeze does not run the DCA algorithm unless triggered.

Off disables the use of RRM and its auto-rf capabilities.

Avoid Foreign AP interference

Enabling this option allows RRM to take surrounding neighboring APs that are not part of your network into consideration.

RRM will create a channel plan to help mitigate co-channel interference.

Avoid Cisco AP Load

This option allows RRM to consider the traffic load on an access point to help build a better channel plan.

I don’t believe in enabling this feature because it can be difficult to make a client device associate with a specific AP.

Avoiding non-802.11a|b noise

This RRM option takes interference on the channel into consideration for the channel plan.

The category of interference is anything coming from a non-AP.

Persistent Device Avoidance

Sometimes there is non-Wi-Fi device interference affecting your wireless network. DCA can help mitigate the issue if Avoid Persistent Non-WiFi Interference option is enabled.

RRM will receive information from CleanAir and if the interference is creating a negative impact, RRM can issue a channel change to avoid it.

Viewing persistent devices can be done by viewing the details of an AP from the web interface. At the bottom of the page are all the persistent devices being tracked including the class type, on what channel the interference was heard, what the duty cycle is, RSSI, and when it was last seen.

DCA Channel Sensitivity

DCA has three different modes it could be in:

Scheduled – DCA algorithm runs at a selected time. Usually to minimize changes to off peak hours.
Steady State – DCA algorithm running at a specified interval.
Startup Mode – Used when making changes to the wireless network architecture. It restarts the DCA algorithm and runs for 100 minutes at high sensitivity.

By default, DCA has a medium channel sensitivity at 15 dB for 5 GHz and 10 dB for 2.4 GHz. This is the DCA Sensitivity Threshold.

By changing the channel sensitivity to high, then a cost metric of 5 dB better will recommend a channel change.

DCA Channel List

To have DCA dynamically select a channel, it must be in the Channel List. You can select specific channels for DCA to select from or select them all, including the UNII-2 channels.

Dynamic Bandwidth Selection

RRM has a flexible way to assign bandwidth to APs by analyzing the RF and selecting the best channel width.

By default, DCA uses 20 MHz channels. You can configure Cisco RRM DCA all the way up to 160 MHz channels or select Best to have RRM pick for you.

If an AP doesn’t support 40/80/160 MHz channels it will not be configured for it.

To see DCA dynamically select channels, head over to the CLI on the controller and enter the debug command:

In the output above, Cisco RRM DCA made a request to change an AP to a 40 MHz channel width using primary channel 100 and secondary 104.

At the very end, RRM sets the channel to 100 with the reason – to reduce co-channel interference.

From command line, it is possible to view when the last channel assignment was set using the following show command:

802.11a – shows the 5 GHz radio 802.11b – shows the 2.4 GHz radio <ap-name> – replace with the name of your AP

The output was truncated just to display the channel assignment information. You can see the current and previous channel average energy, how many times the channel has changed, when it was last changed, and which is the best recommended channel.

Event Driven RRM

If you need the wireless network to react quickly and automatically to bad interference, ED-RRM is an option to enable.

An example could be a device using 100% duty cycle causing all nearby APs and clients to hold off communicating on the wireless medium. ED-RRM would allow an AP to make the channel change sooner than when the DCA interval kicks in.

To configure ED-RRM:

1. Click on Wireless 2. Click on 802.11a/n/ac or 802.11b/g/n 3. Click on DCA 4. At the bottom of the page, enable EDRRM 5. Set the sensitivity threshold to Low (my recommendation is not go above Medium)

The sensitivity threshold defines the air quality (AQ) at the following:

Low sensitivity – AQ at 35%
Medium sensitivity – AQ at 50%
High sensitivity – AQ at 60%

An air quality of 100% is good, very bad is 0%

The Rogue Duty-Cycle option will allow you to set the percentage of duty cycle and rogue duty cycle occurs before triggering EDRRM.

To learn more details about Cisco’s RRM – DCA be sure to check out the white paper from Cisco.

Links and Resources

Cisco RRM White Paper
WPA3 announced by Wi-Fi Alliance

Rowell, CWNE #210, is a network engineer in Higher-Ed. He enjoys working with wireless networking technologies and loves to share and engage with the community. You can connect with him on Twitter , LinkedIn , and Facebook .

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Dynamic Channel Assignment (DCA)

One of the functions that makes up the RRM operations is Dynamic Channel Assignment (DCA) . In this lesson, we’ll be taking a closer look at the DCA algorithm and how it works.

2.3 Design radio management

The Dynamic Channel Assignment (DCA) algorithm is used to automatically determine the most optimal AP channel. Our RF environment is constantly changing. What happens if a rogue AP starts broadcasting on channel our AP is using? Alternatively, we may be experiencing interference from non-802.11 devices.

The wireless controller that’s been assigned as the RF group leader will perform the DCA algorithm. There are a number of parameters our controller uses to determine the most optimal channel for our APs. These include:

Interference.
Signal strength.

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Cisco Wireless LAN Controller Configuration Guide, Release 7.3

Bias-free language.

The documentation set for this product strives to use bias-free language. For the purposes of this documentation set, bias-free is defined as language that does not imply discrimination based on age, disability, gender, racial identity, ethnic identity, sexual orientation, socioeconomic status, and intersectionality. Exceptions may be present in the documentation due to language that is hardcoded in the user interfaces of the product software, language used based on RFP documentation, or language that is used by a referenced third-party product. Learn more about how Cisco is using Inclusive Language.

Using the Web-Browser and CLI Interfaces
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Radio Resource Management

Configuring Cisco CleanAir
FlexConnect
Mobility Groups
Configuring Mobile Concierge
Troubleshooting

Chapter: Radio Resource Management

Radio resource monitoring, overriding the tpc algorithm with minimum and maximum transmit power settings, dynamic channel assignment, coverage hole detection and correction, benefits of rrm, restrictions for configuring rrm, configuring the rf group mode (gui), configuring the rf group mode (cli), configuring transmit power control (gui), information about off-channel scanning defer, configuring off-channel scanning defer for a wlan (gui), configuring off channel scanning defer for a wlan (cli), configuring dynamic channel assignment (gui), configuring coverage hole detection (gui), configuring rrm profile thresholds, monitoring channels, and monitor intervals (gui), configuring rrm (cli), viewing rrm settings (cli), debug rrm issues (cli), information about rrm ndp and rf grouping, configuring rrm ndp (cli), rf group leader, controllers and aps in rf groups, configuring an rf group name (gui), configuring an rf group name (cli), viewing the rf group status (gui), viewing the rf group status (cli), information about overriding rrm, prerequisites for overriding rrm, restrictions for overriding rrm, statically assigning channel and transmit power settings (gui), statically assigning channel and transmit power settings (cli), disabling dynamic channel and power assignment (gui), disabling dynamic channel and power assignment (cli), information about rogue access point detection in rf groups, enabling rogue access point detection in rf groups (gui), configuring rogue access point detection in rf groups (cli), radio measurement requests, location calibration, configuring ccx radio management (gui), configuring ccx radio management (cli), viewing ccx radio management information (cli), debugging ccx radio management issues (cli), information about radio resource management.

The Radio Resource Management (RRM) software embedded in the Cisco Wireless LAN Controller acts as a built-in RF engineer to consistently provide real-time RF management of your wireless network. RRM enables Cisco WLCs to continually monitor their associated lightweight access points for the following information:

Traffic load—The total bandwidth used for transmitting and receiving traffic. It enables wireless LAN managers to track and plan network growth ahead of client demand.

Interference—The amount of traffic coming from other 802.11 sources.

Noise—The amount of non-802.11 traffic that is interfering with the currently assigned channel.

Coverage—The received signal strength (RSSI) and signal-to-noise ratio (SNR) for all connected clients.

Other—The number of nearby access points.

Using this information, RRM can periodically reconfigure the 802.11 RF network for best efficiency. To do this, RRM performs these functions:

Radio resource monitoring

Transmit power control

Dynamic channel assignment

Coverage hole detection and correction

Transmit Power Control

RRM automatically detects and configures new Cisco WLCs and lightweight access points as they are added to the network. It then automatically adjusts associated and nearby lightweight access points to optimize coverage and capacity.

Lightweight access points can simultaneously scan all valid 802.11a/b/g channels for the country of operation as well as for channels available in other locations. The access points go “off-channel” for a period not greater than 60 ms to monitor these channels for noise and interference. Packets collected during this time are analyzed to detect rogue access points, rogue clients, ad-hoc clients, and interfering access points.

In the presence of voice traffic (in the last 100 ms), the access points defer off-channel measurements.

Each access point spends only 0.2 percent of its time off-channel. This activity is distributed across all access points so that adjacent access points are not scanning at the same time, which could adversely affect wireless LAN performance.

When there are numerous rogue access points in the network, the chance of detecting rogues on channels 157 or 161 by a FlexConnect or local mode access point is small. In such cases, the monitor mode AP can be used for rogue detection.

The Cisco WLC dynamically controls access point transmit power based on real-time wireless LAN conditions. You can choose between two versions of transmit power control: TPCv1 and TPCv2. With TPCv1, typically, power can be kept low to gain extra capacity and reduce interference. With TPCv2, transmit power is dynamically adjusted with the goal of minimum interference. TPCv2 is suitable for dense networks. In this mode, there could be higher roaming delays and coverage hole incidents.

The Transmit Power Control (TPC) algorithm both increases and decreases an access point’s power in response to changes in the RF environment. In most instances, TPC seeks to lower an access point's power to reduce interference, but in the case of a sudden change in the RF coverage—for example, if an access point fails or becomes disabled—TPC can also increase power on surrounding access points. This feature is different from coverage hole detection, which is primarily concerned with clients. TPC provides enough RF power to achieve desired coverage levels while avoiding channel interference between access points.

These documents provide more information on Transmit Power Control values for the following access points:

Cisco Aironet 3500 Series http://www.cisco.com/c/en/us/support/wireless/aironet-3500-series/products-installation-guides-list.html

Cisco Aironet 3700 Series http://www.cisco.com/c/en/us/support/wireless/aironet-3700-series/products-installation-guides-list.html

Cisco Aironet 700 Series http://www.cisco.com/c/en/us/support/wireless/aironet-700-series/products-installation-guides-list.html

Cisco Aironet 1530 Series http://www.cisco.com/c/en/us/support/wireless/aironet-1530-series/products-installation-guides-list.html

The TPC algorithm balances RF power in many diverse RF environments. However, it is possible that automatic power control will not be able to resolve some scenarios in which an adequate RF design was not possible to implement due to architectural restrictions or site restrictions—for example, when all access points must be mounted in a central hallway, placing the access points close together, but requiring coverage out to the edge of the building.

In these scenarios, you can configure maximum and minimum transmit power limits to override TPC recommendations. The maximum and minimum TPC power settings apply to all access points through RF profiles in a RF network.

To set the Maximum Power Level Assignment and Minimum Power Level Assignment, enter the maximum and minimum transmit power used by RRM in the text boxes in the Tx Power Control page. The range for these parameters is -10 to 30 dBm. The minimum value cannot be greater than the maximum value; the maximum value cannot be less than the minimum value.

If you configure a maximum transmit power, RRM does not allow any access point attached to the controller to exceed this transmit power level (whether the power is set by RRM TPC or by coverage hole detection). For example, if you configure a maximum transmit power of 11 dBm, then no access point would transmit above 11 dBm, unless the access point is configured manually.

Two adjacent access points on the same channel can cause either signal contention or signal collision. In a collision, data is not received by the access point. This functionality can become a problem, for example, when someone reading e-mail in a café affects the performance of the access point in a neighboring business. Even though these are completely separate networks, someone sending traffic to the café on channel 1 can disrupt communication in an enterprise using the same channel. Controllers can dynamically allocate access point channel assignments to avoid conflict and to increase capacity and performance. Channels are “reused” to avoid wasting scarce RF resources. In other words, channel 1 is allocated to a different access point far from the café, which is more effective than not using channel 1 altogether.

The controller ’s Dynamic Channel Assignment (DCA) capabilities are also useful in minimizing adjacent channel interference between access points. For example, two overlapping channels in the 802.11b/g band, such as 1 and 2, cannot both simultaneously use 11/54 Mbps. By effectively reassigning channels, the controller keeps adjacent channels separated.

We recommend that you use only non-overlapping channels (1, 6, 11, and so on).

The controller examines a variety of real-time RF characteristics to efficiently handle channel assignments as follows:

Access point received energy—The received signal strength measured between each access point and its nearby neighboring access points. Channels are optimized for the highest network capacity.

Noise—Noise can limit signal quality at the client and access point. An increase in noise reduces the effective cell size and degrades user experience. By optimizing channels to avoid noise sources, the controller can optimize coverage while maintaining system capacity. If a channel is unusable due to excessive noise, that channel can be avoided.

802.11 Interference—Interference is any 802.11 traffic that is not part of your wireless LAN, including rogue access points and neighboring wireless networks. Lightweight access points constantly scan all channels looking for sources of interference. If the amount of 802.11 interference exceeds a predefined configurable threshold (the default is 10 percent), the access point sends an alert to the controller . Using the RRM algorithms, the controller may then dynamically rearrange channel assignments to increase system performance in the presence of the interference. Such an adjustment could result in adjacent lightweight access points being on the same channel, but this setup is preferable to having the access points remain on a channel that is unusable due to an interfering foreign access point.

In addition, if other wireless networks are present, the controller shifts the usage of channels to complement the other networks. For example, if one network is on channel 6, an adjacent wireless LAN is assigned to channel 1 or 11. This arrangement increases the capacity of the network by limiting the sharing of frequencies. If a channel has virtually no capacity remaining, the controller may choose to avoid this channel. In very dense deployments in which all nonoverlapping channels are occupied, the controller does its best, but you must consider RF density when setting expectations.

Load and utilization—When utilization monitoring is enabled, capacity calculations can consider that some access points are deployed in ways that carry more traffic than other access points (for example, a lobby versus an engineering area). The controller can then assign channels to improve the access point with the worst performance reported. The load is taken into account when changing the channel structure to minimize the impact on clients currently in the wireless LAN. This metric keeps track of every access point’s transmitted and received packet counts to determine how busy the access points are. New clients avoid an overloaded access point and associate to a new access point. This parameter is disabled by default.

The controller combines this RF characteristic information with RRM algorithms to make system-wide decisions. Conflicting demands are resolved using soft-decision metrics that guarantee the best choice for minimizing network interference. The end result is optimal channel configuration in a three-dimensional space, where access points on the floor above and below play a major factor in an overall wireless LAN configuration.

Radios using 40-MHz channels in the 2.4-GHz band or or 80MHz channels are not supported by DCA.

The RRM startup mode is invoked in the following conditions:

In a single- controller environment, the RRM startup mode is invoked after the controller is upgraded and rebooted.

In a multiple- controller environment, the RRM startup mode is invoked after an RF Group leader is elected.

You can trigger RRM startup mode from CLI.

The RRM coverage hole detection algorithm can detect areas of radio coverage in a wireless LAN that are below the level needed for robust radio performance. This feature can alert you to the need for an additional (or relocated) lightweight access point.

If clients on a lightweight access point are detected at threshold levels (RSSI, failed client count, percentage of failed packets, and number of failed packets) lower than those specified in the RRM configuration, the access point sends a “coverage hole” alert to the controller . The alert indicates the existence of an area where clients are continually experiencing poor signal coverage, without having a viable access point to which to roam. The controller discriminates between coverage holes that can and cannot be corrected. For coverage holes that can be corrected, the controller mitigates the coverage hole by increasing the transmit power level for that specific access point. The controller does not mitigate coverage holes caused by clients that are unable to increase their transmit power or are statically set to a power level because increasing their downstream transmit power might increase interference in the network.

RRM produces a network with optimal capacity, performance, and reliability. It frees you from having to continually monitor the network for noise and interference problems, which can be transient and difficult to troubleshoot. RRM ensures that clients enjoy a seamless, trouble-free connection throughout the Cisco unified wireless network.

RRM uses separate monitoring and control for each deployed network: 802.11a and 802.11b/g. The RRM algorithms run separately for each radio type (802.11a and 802.11b/g). RRM uses both measurements and algorithms. RRM measurements can be adjusted using monitor intervals, but they cannot be disabled. RRM algorithms are enabled automatically but can be disabled by statically configuring channel and power assignment. The RRM algorithms run at a specified updated interval, which is 600 seconds by default.

The OEAP 600 series access points do not support RRM. The radios for the 600 series OEAP access points are controlled through the local GUI of the 600 series access points and not through the Cisco WLC. Attempting to control the spectrum channel or power, or disabling the radios through the Cisco WLC will fail to have any effect on the 600 series OEAP.

Configuring RRM

The controller’s preconfigured RRM settings are optimized for most deployments. However, you can modify the controller’s RRM configuration parameters at any time through either the GUI or the CLI.

You can configure these parameters on controllers that are part of an RF group or on controllers that are not part of an RF group.

The RRM parameters should be set to the same values on every controller in an RF group. The RF group leader can change as a result of controller reboots or depending on which radios hear each other. If the RRM parameters are not identical for all RF group members, varying results can occur when the group leader changes.

Using the controller GUI, you can configure the following RRM parameters: RF group mode, transmit power control, dynamic channel assignment, coverage hole detection, profile thresholds, monitoring channels, and monitor intervals.

Choose Wireless > 802.11a/n or 802.11b/g/n > RRM > RF Grouping to open the 802.11a (or 802.11b/g) RRM > RF Grouping page.

From the Group Mode drop-down list, select the mode you want to configure for this Cisco WLC.

You can configure RF grouping in the following modes:

auto—Sets the RF group selection to automatic update mode.

This mode does not support IPv6 based configuration.

leader—Sets the RF group selection to static mode, and sets this Cisco WLC as the group leader.

Leader supports static IPv6 address.

If a RF group member is configured using IPv4 address, then IPv4 address is used to communicate with the leader. The same is applicable for a RF group member configured using IPv6 too.

off—Sets the RF group selection off. Every Cisco WLC optimizes its own access point parameters.

A configured static leader cannot become a member of another Cisco WLC until its mode is set to “auto”.

A Cisco WLC with a lower priority cannot assume the role of a group leader if a Cisco WLC with a higher priority is available. Here priority is related to the processing power of the Cisco WLC.

We recommend that Cisco WLCs participate in automatic RF grouping. You can override RRM settings without disabling automatic RF group participation.

In the Cisco WLC Name text box, enter the Cisco WLC that you want to add as a member to this group.

In the IP Address (IPv4/IPv6) text box, enter the IPv4/IPv6 address of the RF Group Member.

Click Add Member to add the member to this group.

If the member has not joined the static leader, the reason of the failure is shown in parentheses.

Configure the RF Grouping mode by entering this command:

config advanced { 802.11a | 802.11b } group-mode { auto | leader | off | restart }

auto—Sets the RF group selection to automatic update mode.

leader—Sets the RF group selection to static mode, and sets this Cisco WLC as the group leader.

If a group member is configured with IPv4 address, then IPv4 address is used to communicate with a leader and vice versa with IPv6 also.

restart—Restarts the RF group selection.

A configured static leader cannot become a member of another Cisco WLC until its mode is set to “auto”.

A Cisco WLC with a lower priority cannot assume the role of a group leader if a Cisco WLC with higher priority is available. Here priority is related to the processing power of the Cisco WLC.

config advanced {802.11a | 802.11b} group-member add controller_name ipv4/ipv6 _address

config advanced {802.11a | 802.11b} group-member remove controller_nam ipv4/ipv6_address

You can add RF Group Members using either IPv4 or IPv6 address.

show advanced { 802.11a | 802.11b } group

Choose Wireless > 802.11a/n or 802.11b/g/n > RRM > TPC to open the 802.11a/n (or 802.11b/g/n) > RRM > Tx Power Control (TPC) page.

Choose the Transmit Power Control version from the following options:

Interference Optimal Mode (TPCv2)—For scenarios where voice calls are extensively used. Transmit power is dynamically adjusted with the goal of minimum interference. It is suitable for dense networks. In this mode, there could be higher roaming delays and coverage hole incidents.

We recommend that you use TCPv2 only in cases where RF issues cannot be resolved by using TCPv1. Please evaluate and test the use of TPCv2 with the assistance of Cisco Services.

Coverage Optimal Mode (TPCv1)—(Default) Offers strong signal coverage and stability. In this mode, power can be kept low to gain extra capacity and reduce interference.

Automatic —Causes the Cisco WLC to periodically evaluate and, if necessary, update the transmit power for all joined access points. This is the default value.

On Demand —Causes the Cisco WLC to periodically evaluate the transmit power for all joined access points. However, the Cisco WLC updates the power, if necessary, only when you click Invoke Power Update Now .

The Cisco WLC does not evaluate and update the transmit power immediately after you click Invoke Power Update Now. It waits for the next 600-second interval. This value is not configurable.

Fixed —Prevents the Cisco WLC from evaluating and, if necessary, updating the transmit power for joined access points. The power level is set to the fixed value chosen from the drop-down list.

The transmit power level is assigned an integer value instead of a value in mW or dBm. The integer corresponds to a power level that varies depending on the regulatory domain, channel, and antennas in which the access points are deployed.

For optimal performance, we recommend that you use the Automatic setting.

The range for the Maximum Power Level Assignment is –10 to 30 dBm.

The range for the Minimum Power Level Assignment is –10 to 30 dBm.

The range for this parameter is –80 to –50 dBm. Increasing this value (between –65 and –50 dBm) causes the access points to operate at a higher transmit power. Decreasing the value has the opposite effect.

In applications with a dense population of access points, it may be useful to decrease the threshold to –80 or –75 dBm to reduce the number of BSSIDs (access points) and beacons seen by the wireless clients. Some wireless clients might have difficulty processing a large number of BSSIDs or a high beacon rate and might exhibit problematic behavior with the default threshold.

This page also shows the following nonconfigurable transmit power level parameter settings:

Power Neighbor Count—The minimum number of neighbors an access point must have for the transmit power control algorithm to run.

Power Assignment Leader—The MAC address of the RF group leader, which is responsible for power level assignment.

Last Power Level Assignment—The last time RRM evaluated the current transmit power level assignments.

Configuring Off-Channel Scanning Defer

In deployments with certain power-save clients, you sometimes need to defer the Radio Resource Management's (RRM) normal off-channel scanning to avoid missing critical information from low-volume clients (for example, medical devices that use power-save mode and periodically send telemetry information). This feature improves the way that Quality of Service (QoS) interacts with the RRM scan defer feature.

You can use a client's Wi-Fi Multimedia (WMM) UP marking to configure the access point to defer off-channel scanning for a configurable period of time if it receives a packet marked UP.

Off-Channel Scanning Defer is essential to the operation of RRM, which gathers information about alternate channel choices such as noise and interference. Additionally, Off-Channel Scanning Defer is responsible for rogue detection. Devices that need to defer Off-Channel Scanning Defer should use the same WLAN as often as possible. If there are many of these devices (and the possibility exists that Off-Channel Defer scanning could be completely disabled by the use of this feature), you should implement an alternative to local AP Off-Channel Scanning Defer, such as monitoring access points, or other access points in the same location that do not have this WLAN assigned.

You can assign a QoS policy (bronze, silver, gold, and platinum) to a WLAN to affect how packets are marked on the downlink connection from the access point regardless of how they were received on the uplink from the client. UP=1,2 is the lowest priority, and UP=0,3 is the next higher priority. The marking results of each QoS policy are as follows:

Bronze marks all downlink traffic to UP= 1.

Silver marks all downlink traffic to UP= 0.

Gold marks all downlink traffic to UP=4.

Platinum marks all downlink traffic to UP=6.

Configuring Off-Channel Scanning Defer for WLANs

Choose WLANs to open the WLANs page.
	Click the ID number of the WLAN to which you want to configure off-channel scanning Defer.
	Choose the Advanced tab from the WLANs > Edit page.
	From the Off Channel Scanning Defer section, set the Scan Defer Priority by clicking on the priority argument.
	Set the time in milliseconds in the Scan Defer Time text box. Valid values are 100 through 60000. The default value is 100 milliseconds.
	Click Apply to save your configuration.

Assign a defer-priority for the channel scan by entering this command:

config wlan channel-scan defer-priority priority [ enable | disable ] WLAN-id

The valid range for the priority argument is 0 to 7.

The priority is 0 to 7 (this value should be set to 6 on the client and on the WLAN).

Use this command to configure the amount of time that scanning will be deferred following an UP packet in the queue.

Assign the channel scan defer time (in milliseconds) by entering this command:

config wlan channel-scan defer-time msec WLAN-id

The time value is in miliseconds (ms) and the valid range is 100 (default) to 60000 (60 seconds). This setting should match the requirements of the equipment on your wireless LAN.

You can also configure this feature on the Cisco WLC GUI by selecting WLANs, and either edit an existing WLAN or create a new one.

You can specify the channels that the dynamic channel assignment (DCA) algorithm considers when selecting the channels to be used for RRM scanning by using the Cisco WLC GUI.

This functionality is helpful when you know that the clients do not support certain channels because they are legacy devices or they have certain regulatory restrictions.

Disable the 802.11a/n or 802.11b/g/n network as follows: Choose Wireless > 802.11a/n or 802.11b/g/n > Network to open the Global Parameters page. Unselect the 802.11a (or 802.11b/g) Network Status check box. Click Apply.

Choose Wireless > 802.11a/n or 802.11b/g/n > RRM > DCA to open the Dynamic Channel Assignment (DCA) page.

Choose one of the following options from the Channel Assignment Method drop-down list to specify the Cisco WLC’s DCA mode:

Automatic—Causes the Cisco WLC to periodically evaluate and, if necessary, update the channel assignment for all joined access points. This is the default value.

Freeze—Causes the Cisco WLC to evaluate and update the channel assignment for all joined access points, if necessary, but only when you click Invoke Channel Update Once.

The Cisco WLC does not evaluate and update the channel assignment immediately after you click Invoke Channel Update Once. It waits for the next interval to elapse.

OFF —Turns off DCA and sets all access point radios to the first channel of the band, which is the default value. If you choose this option, you must manually assign channels on all radios.

For optimal performance, we recommend that you use the Automatic setting. See the section for instructions on how to disable the Cisco WLC’s dynamic channel and power settings.

If your Cisco WLC supports only OfficeExtend access points, we recommend that you set the DCA interval to 6 hours for optimal performance. For deployments with a combination of OfficeExtend access points and local access points, the range of 10 minutes to 24 hours can be used.

Low —The DCA algorithm is not particularly sensitive to environmental changes.

Medium —The DCA algorithm is moderately sensitive to environmental changes.

High —The DCA algorithm is highly sensitive to environmental changes.

The default value is Medium. The DCA sensitivity thresholds vary by radio band, as noted in the table below.

Table 1 DCA Sensitivity Thresholds
Option	2.4-GHz DCA Sensitivity Threshold	5-GHz DCA Sensitivity Threshold
High	5 dB	5 dB
Medium	10 dB	15 dB
Low	20 dB	20 dB

20 MHz —The 20-MHz channel bandwidth (default)

40 MHz —The 40-MHz channel bandwidth

If you choose 40 MHz, be sure to choose at least two adjacent channels from the DCA Channel List in (for example, a primary channel of 36 and an extension channel of 40). If you choose only one channel, that channel is not used for 40-MHz channel width.

If you choose 40 MHz, you can also configure the primary and extension channels used by individual access points.

To override the globally configured DCA channel width setting, you can statically configure an access point’s radio for 20- or 40-MHz mode on the 802.11a/n Cisco APs > Configure page. if you then change the static RF channel assignment method to WLC Controlled on the access point radio, the global DCA configuration overrides the channel width configuration that the access point was previously using. It can take up to 30 minutes (depending on how often DCA is configured to run) for the change to take effect.

If you choose 40 MHz on the A radio, you cannot pair channels 116, 140, and 165 with any other channels.

This page also shows the following nonconfigurable channel parameter settings:

Channel Assignment Leader—The MAC address of the RF group leader, which is responsible for channel assignment.

Last Auto Channel Assignment—The last time RRM evaluated the current channel assignments.

This parameter is applicable only for deployments having outdoor access points such as 1522 and 1524.

The ranges are as follows:  802.11a—36, 40, 44, 48, 52, 56, 60, 64, 100, 104, 108, 112, 116, 132, 136, 140, 149, 153, 157, 161, 165, 190, 196 802.11b/g—1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11

The defaults are as follows: 802.11a—36, 40, 44, 48, 52, 56, 60, 64, 100, 104, 108, 112, 116, 132, 136, 140, 149, 153, 157, 161 802.11b/g—1, 6, 11

These extended UNII-2 channels in the 802.11a band do not appear in the channel list: 100, 104, 108, 112, 116, 132, 136, and 140. If you have Cisco Aironet 1520 series mesh access points in the -E regulatory domain, you must include these channels in the DCA channel list before you start operation. If you are upgrading from a previous release, verify that these channels are included in the DCA channel list. To include these channels in the channel list, select the Extended UNII-2 Channels check box.

The ranges are as follows:  802.11a—1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26

The defaults are as follows: 802.11a—20, 26

Choose Wireless > 802.11a/n or 802.11b/g/n > Network to open the Global Parameters page.

Select the 802.11a (or 802.11b/g ) Network Status check box.

Click Apply .

To see why the DCA algorithm changed channels, choose Monitor and then choose View All under Most Recent Traps. The trap provides the MAC address of the radio that changed channels, the previous channel and the new channel, the reason why the change occurred, the energy before and after the change, the noise before and after the change, and the interference before and after the change.

Disable the 802.11 network as follows: Choose Wireless > 802.11a/n or 802.11b/g/n > Network to open the 802.11a (or 802.11b/g) Global Parameters page. Unselect the 802.11a (or 802.11b/g) Network Status check box. Click Apply.
	Choose Wireless > 802.11a/n or 802.11b/g/n > RRM > Coverage to open the 802.11a (or 802.11b/g/n) > RRM > Coverage page.
	Select the Enable Coverage Hole Detection check box to enable coverage hole detection, or unselect it to disable this feature. If you enable coverage hole detection, the Cisco WLC automatically determines, based on data received from the access points, if any access points have clients that are potentially located in areas with poor coverage. The default value is selected.
	In the Data RSSI text box, enter the minimum receive signal strength indication (RSSI) value for data packets received by the access point. The value that you enter is used to identify coverage holes (or areas of poor coverage) within your network. If the access point receives a packet in the data queue with an RSSI value below the value that you enter here, a potential coverage hole has been detected. The valid range is –90 to –60 dBm, and the default value is –80 dBm. The access point takes data RSSI measurements every 5 seconds and reports them to the Cisco WLC in 90-second intervals.
	In the Voice RSSI text box, enter the minimum receive signal strength indication (RSSI) value for voice packets received by the access point. The value that you enter is used to identify coverage holes within your network. If the access point receives a packet in the voice queue with an RSSI value below the value that you enter here, a potential coverage hole has been detected. The valid range is –90 to –60 dBm, and the default value is –75 dBm. The access point takes voice RSSI measurements every 5 seconds and reports them to the Cisco WLC in 90-second intervals.
	In the Min Failed Client Count per AP text box, enter the minimum number of clients on an access point with an RSSI value at or below the data or voice RSSI threshold. The valid range is 1 to 75, and the default value is 3.
	In the Coverage Exception Level per AP text box, enter the percentage of clients on an access point that are experiencing a low signal level but cannot roam to another access point. The valid range is 0 to 100%, and the default value is 25%.	If both the number and percentage of failed packets exceed the values configured for Failed Packet Count and Failed Packet Percentage (configurable through the Cisco WLC CLI) for a 5-second period, the client is considered to be in a pre-alarm condition. The Cisco WLC uses this information to distinguish between real and false coverage holes. False positives are generally due to the poor roaming logic implemented on most clients. A coverage hole is detected if both the number and percentage of failed clients meet or exceed the values entered in the Min Failed Client Count per AP and Coverage Exception Level per AP text boxes over a 90-second period. The Cisco WLC determines if the coverage hole can be corrected and, if appropriate, mitigates the coverage hole by increasing the transmit power level for that specific access point.

Choose Wireless > 802.11a/n or 802.11b/g/n > Network to open the 802.11a (or 802.11b/g) Global Parameters page.

Select the 802.11a (or 802.11b/g/n ) Network Status check box.

Choose Wireless > 802.11a/n or 802.11b/g/n > RRM > General to open the 802.11a/n (or 802.11b/g/n) > RRM > General page.
	Configure profile thresholds used for alarming as follows:	The profile thresholds have no bearing on the functionality of the RRM algorithms. Lightweight access points send an SNMP trap (or an alert) to the Cisco WLC when the values set for these threshold parameters are exceeded.

In the Interference text box, enter the percentage of interference (802.11 traffic from sources outside of your wireless network) on a single access point. The valid range is 0 to 100%, and the default value is 10%.
In the Clients text box, enter the number of clients on a single access point. The valid range is 1 to 75, and the default value is 12.
In the Noise text box, enter the level of noise (non-802.11 traffic) on a single access point. The valid range is –127 to 0 dBm, and the default value is –70 dBm.
In the Utilization text box, enter the percentage of RF bandwidth being used by a single access point. The valid range is 0 to 100%, and the default value is 80%.

All Channels —RRM channel scanning occurs on all channels supported by the selected radio, which includes channels not allowed in the country of operation.

Country Channels —RRM channel scanning occurs only on the data channels in the country of operation. This is the default value.

DCA Channels —RRM channel scanning occurs only on the channel set used by the DCA algorithm, which by default includes all of the non-overlapping channels allowed in the country of operation. However, you can specify the channel set to be used by DCA if desired. To do so, follow instructions in the Dynamic Channel Assignment .

In the Channel Scan Interval text box, enter (in seconds) the sum of the time between scans for each channel within a radio band. The entire scanning process takes 50 ms per channel, per radio and runs at the interval configured here. The time spent listening on each channel is determined by the non-configurable 50-ms scan time and the number of channels to be scanned. For example, in the U.S. all 11 802.11b/g channels are scanned for 50 ms each within the default 180-second interval. So every 16 seconds, 50 ms is spent listening on each scanned channel (180/11 = ~16 seconds). The Channel Scan Interval parameter determines the interval at which the scanning occurs.The valid range is 60 to 3600 seconds, and the default value is 60 seconds for 802.11a radios and 180 seconds for the 802.11b/g radios.

If your Cisco WLC supports only OfficeExtend access points, we recommend that you set the channel scan interval to 1800 seconds for optimal performance. For deployments with a combination of OfficeExtend access points and local access points, the range of 60 to 3600 seconds can be used.

In the Neighbor Packet Frequency text box, enter (in seconds) how frequently neighbor packets (messages) are sent, which eventually builds the neighbor list. The valid range is 60 to 3600 seconds, and the default value is 60 seconds.

If your Cisco WLC supports only OfficeExtend access points, we recommend that you set the neighbor packet frequency to 600 seconds for optimal performance. For deployments with a combination of OfficeExtend access points and local access points, the range of 60 to 3600 seconds can be used.

If the access point radio does not receive a neighbor packet from an existing neighbor within 60 minutes, the Cisco WLC deletes that neighbor from the neighbor list.

Click Set to Factory Default if you want to return all of the Cisco WLC’s RRM parameters to their factory-default values.

Disable the 802.11 network by entering this command:

config { 802.11a | 802.11b} disable network

Choose the Transmit Power Control version by entering this command:

config advanced { 802.11a | 802.11b} tpc-version {1 | 2}

where:

TPCv1: Coverage-optimal—(Default) Offers strong signal coverage and stability with negligent intercell interferences and sticky client syndrome.

TPCv2: Interference-optimal—For scenarios where voice calls are extensively used. Tx power is dynamically adjusted with the goal of minimum interference. It is suitable for dense networks. In this mode, there can be higher roaming delays and coverage hole incidents.

Perform one of the following to configure transmit power control:

Have RRM automatically set the transmit power for all 802.11 radios at periodic intervals by entering this command:

config { 802.11a | 802.11b} txPower global auto

Have RRM automatically reset the transmit power for all 802.11a or 802.11b/g radios one time by entering this command:

config { 802.11a | 802.11b} txPower global once

Configure the transmit power range that overrides the Transmit Power Control algorithm, use this command to enter the maximum and minimum transmit power used by RRM:

config { 802.11a | 802.11b} txPower global { max | min} txpower

where txpower is a value from –10 to 30 dBM. The minimum value cannot be greater than the maximum value; the maximum value cannot be less than the minimum value.

If you configure a maximum transmit power, RRM does not allow any access point to exceed this transmit power (whether the maximum is set at RRM startup, or by coverage hole detection). For example, if you configure a maximum transmit power of 11 dBm, then no access point would transmit above 11 dBm, unless the access point is configured manually.

Manually change the default transmit power setting by entering this command:

config advanced { 802.11a | 802.11b} { tpcv1-thresh | tpcv2-thresh} threshold

where threshold is a value from –80 to –50 dBm. Increasing this value causes the access points to operate at higher transmit power rates. Decreasing the value has the opposite effect.

In applications with a dense population of access points, it may be useful to decrease the threshold to –80 or –75 dBm in order to reduce the number of BSSIDs (access points) and beacons seen by the wireless clients. Some wireless clients may have difficulty processing a large number of BSSIDs or a high beacon rate and may exhibit problematic behavior with the default threshold.

Configure the Transmit Power Control Version 2 on a per-channel basis by entering this command:

config advanced { 802.11a | 802.11b} tpcv2-per-chan { enable | disable}

Perform one of the following to configure dynamic channel assignment (DCA):

Have RRM automatically configure all 802.11 channels based on availability and interference by entering this command:

config { 802.11a | 802.11b} channel global auto

Have RRM automatically reconfigure all 802.11 channels one time based on availability and interference by entering this command:

config { 802.11a | 802.11b} channel global once

Disable RRM and set all channels to their default values by entering this command:

config { 802.11a | 802.11b} channel global off

Restart aggressive DCA cycle by entering this command:

config {802.11a | 802.11b} channel global restart

To specify the channel set used for DCA by entering this command:

config advanced { 802.11a | 802.11b} channel { add | delete} channel_number

You can enter only one channel number per command. This command is helpful when you know that the clients do not support certain channels because they are legacy devices or they have certain regulatory restrictions.

Configure additional DCA parameters by entering these commands:

config advanced { 802.11a | 802.11b} channel dca anchor-time value—Specifies the time of day when the DCA algorithm is to start. value is a number between 0 and 23 (inclusive) representing the hour of the day from 12:00 a.m. to 11:00 p.m.

config advanced { 802.11a | 802.11b} channel dca interval value—Specifies how often the DCA algorithm is allowed to run. value is one of the following: 1, 2, 3, 4, 6, 8, 12, or 24 hours or 0, which is the default value of 10 minutes (or 600 seconds).

config advanced { 802.11a | 802.11b } channel dca sensitivity { low | medium | high } —Specifies how sensitive the DCA algorithm is to environmental changes such as signal, load, noise, and interference when determining whether to change channel.

low means that the DCA algorithm is not particularly sensitive to environmental changes.

medium means that the DCA algorithm is moderately sensitive to environmental changes.

high means that the DCA algorithm is highly sensitive to environmental changes.

The DCA sensitivity thresholds vary by radio band, as noted in following table.

Table 2 DCA Sensitivity Thresholds
Option	2.4-GHz DCA Sensitivity Threshold	5-GHz DCA Sensitivity Threshold
High	5 dB	5 dB
Medium	10 dB	15 dB
Low	20 dB	20 dB

config advanced 802.11a channel dca chan-width-11n { 20 | 40 } —Configures the DCA channel width for all 802.11n radios in the 5-GHz band.

20 sets the channel width for 802.11n radios to 20 MHz. This is the default value.

40 sets the channel width for 802.11n radios to 40 MHz.

If you choose 40, be sure to set at least two adjacent channels in the config advanced 802.11a channel { add | delete} channel_number command in (for example, a primary channel of 36 and an extension channel of 40). If you set only one channel, that channel is not used for 40-MHz channel width.

If you choose 40, you can also configure the primary and extension channels used by individual access points.

To override the globally configured DCA channel width setting, you can statically configure an access point’s radio for 20-MHz or 40-MHz mode using the config 802.11a chan_width Cisco_AP { 20 | 40} command. If you change the static configuration to global on the access point radio, the global DCA configuration overrides the channel width configuration that the access point was previously using. It can take up to 30 minutes (depending on how often DCA is configured to run) for the change to take effect.

config advanced { 802.11a | 802.11b } channel outdoor-ap-dca { enable | disable } —Enables or disables to the Cisco WLC to avoid checks for non-DFS channels.

config advanced { 802.11a | 802.11b } channel foreign { enable | disable } —Enables or disables foreign access point interference avoidance in the channel assignment.

config advanced { 802.11a | 802.11b } channel load { enable | disable } —Enables or disables load avoidance in the channel assignment.

config advanced { 802.11a | 802.11b } channel noise { enable | disable } —Enables or disables noise avoidance in the channel assignment.

config advanced { 802.11a | 802.11b } channel update —Initiates an update of the channel selection for every Cisco access point.

In Cisco WLC software release 5.2 or later releases, you can disable coverage hole detection on a per-WLAN basis.

config advanced { 802.11a | 802.11b } coverage { enable | disable } —Enables or disables coverage hole detection. If you enable coverage hole detection, the Cisco WLC automatically determines, based on data received from the access points, if any access points have clients that are potentially located in areas with poor coverage. The default value is enabled.

config advanced { 802.11a | 802.11b } coverage { data | voice } rssi-threshold rssi —Specifies the minimum receive signal strength indication (RSSI) value for packets received by the access point. The value that you enter is used to identify coverage holes (or areas of poor coverage) within your network. If the access point receives a packet in the data or voice queue with an RSSI value below the value you enter here, a potential coverage hole has been detected. The valid range is –90 to –60 dBm, and the default value is –80 dBm for data packets and –75 dBm for voice packets. The access point takes RSSI measurements every 5 seconds and reports them to the Cisco WLC in 90-second intervals.

config advanced { 802.11a | 802.11b } coverage level global clients —Specifies the minimum number of clients on an access point with an RSSI value at or below the data or voice RSSI threshold. The valid range is 1 to 75, and the default value is 3.

config advanced { 802.11a | 802.11b } coverage exception global percent —Specifies the percentage of clients on an access point that are experiencing a low signal level but cannot roam to another access point. The valid range is 0 to 100%, and the default value is 25%.

config advanced { 802.11a | 802.11b } coverage { data | voice } packet-count packets —Specifies the minimum failure count threshold for uplink data or voice packets. The valid range is 1 to 255 packets, and the default value is 10 packets.

config advanced { 802.11a | 802.11b } coverage { data | voice } fail-rate percent —Specifies the failure rate threshold for uplink data or voice packets. The valid range is 1 to 100%, and the default value is 20%.

If both the number and percentage of failed packets exceed the values entered in the packet-count and fail-rate commands for a 5-second period, the client is considered to be in a pre-alarm condition. The Cisco WLC uses this information to distinguish between real and false coverage holes. False positives are generally due to the poor roaming logic implemented on most clients. A coverage hole is detected if both the number and percentage of failed clients meet or exceed the values entered in the coverage level global and coverage exception global commands over a 90-second period. The Cisco WLC determines if the coverage hole can be corrected and, if appropriate, mitigates the coverage hole by increasing the transmit power level for that specific access point.

config { 802.11a | 802.11b } enable network

To enable the 802.11g network, enter config 802.11b 11gSupport enable after the config 802.11b enable network command.

To see 802.11a and 802.11b/g RRM settings, use these commands:

show advanced { 802.11a | 802.11b } ?

where ? is one of the following:

ccx { global | Cisco_AP } —Shows the CCX RRM configuration.

channel —Shows the channel assignment configuration and statistics.

coverage —Shows the coverage hole detection configuration and statistics.

logging —Shows the RF event and performance logging.

monitor —Shows the Cisco radio monitoring.

profile { global | Cisco_AP } —Shows the access point performance profiles.

receiver —Shows the 802.11a or 802.11b/g receiver configuration and statistics.

summary —Shows the configuration and statistics of the 802.11a or 802.11b/g access points.

txpower —Shows the transmit power assignment configuration and statistics.

Use these commands to troubleshoot and verify RRM behavior:

debug airewave-director ?

all —Enables debugging for all RRM logs.

channel —Enables debugging for the RRM channel assignment protocol.

detail —Enables debugging for RRM detail logs.

error —Enables debugging for RRM error logs.

group —Enables debugging for the RRM grouping protocol.

manager —Enables debugging for the RRM manager.

message —Enables debugging for RRM messages.

packet —Enables debugging for RRM packets.

power —Enables debugging for the RRM power assignment protocol as well as coverage hole detection.

profile —Enables debugging for RRM profile events.

radar —Enables debugging for the RRM radar detection/avoidance protocol.

rf-change —Enables debugging for RRM RF changes.

Configuring RRM Neighbor Discovery Packets

The Cisco Neighbor Discovery Packet (NDP) is the fundamental tool for RRM and other wireless applications that provides information about the neighbor radio information. You can configure the controller to encrypt neighbor discovery packets.

This feature enables you to be compliant with the PCI specifications.

An RF group can only be formed between Cisco WLCs that have the same encryption mechanism. That is, an access point associated to a Cisco WLC that is encrypted can not be neighbors with an access point associated to a Cisco WLC that is not encrypted. The two Cisco WLCs and their access points will not recognize each other as neighbors and cannot form an RF group. It is possible to assign two Cisco WLCs in a static RF group configuration that has mismatched encryption settings. In this case, the two Cisco WLCs do not function as a single RF group because the access points belonging to the mismatched Cisco WLCs do not recognize one another as neighbors in the group.

To configure RRM NDP using the Cisco WLC CLI, enter this command:

config advanced 802.11 { a | b } monitor ndp-mode { protected | transparent }

This command configures NDP mode. By default, the mode is set to “transparent”. The following options are available:

Protected—Packets are encrypted.

Transparent—Packets are sent as is.

Use this command to see the discovery type:

show advanced 802.11 { a | b } monitor

Configuring RF Groups

Information about rf groups.

An RF group is a logical collection of Cisco WLCs that coordinate to perform RRM in a globally optimized manner to perform network calculations on a per-radio basis. An RF group exists for each 802.11 network type. Clustering Cisco WLCs into a single RF group enable the RRM algorithms to scale beyond the capabilities of a single Cisco WLC.

User-configured RF network name.

Neighbor discovery performed at the radio level.

Country list configured on MC.

RF grouping runs between MCs.

Lightweight access points periodically send out neighbor messages over the air. Access points using the the same RF group name validate messages from each other.

When access points on different Cisco WLCs hear validated neighbor messages at a signal strength of –80 dBm or stronger, the Cisco WLCs dynamically form an RF neighborhood in auto mode. In static mode, the leader is manually selected and the members are added to the RF Group. To know more about RF Group modes, “RF Group Leader” section .

RF groups and mobility groups are similar in that they both define clusters of Cisco WLCs, but they are different in terms of their use. An RF group facilitates scalable, system-wide dynamic RF management while a mobility group facilitates scalable, system-wide mobility and Cisco WLC redundancy.

RF Group Name

Starting in the 7.0.116.0 release, the RF Group Leader can be configured in two ways as follows:

Auto Mode—In this mode, the members of an RF group elect an RF group leader to maintain a “master” power and channel scheme for the group. The RF grouping algorithm dynamically chooses the RF group leader and ensures that an RF group leader is always present. Group leader assignments can and do change (for instance, if the current RF group leader becomes inoperable or if RF group members experience major changes).

Static Mode—In this mode, the user selects a Cisco WLC as an RF group leader manually. In this mode, the leader and the members are manually configured and are therefore fixed. If the members are unable to join the RF group, the reason is indicated. The leader tries to establish a connection with a member every 1 minute if the member has not joined in the previous attempt.

The RF group leader analyzes real-time radio data collected by the system, calculates the power and channel assignments, and sends them to each of the Cisco WLCs in the RF group. The RRM algorithms ensure system-wide stability and restrain channel and power scheme changes to the appropriate local RF neighborhoods.

In Cisco WLC software releases prior to 6.0, the dynamic channel assignment (DCA) search algorithm attempts to find a good channel plan for the radios associated to Cisco WLCs in the RF group, but it does not adopt a new channel plan unless it is considerably better than the current plan. The channel metric of the worst radio in both plans determines which plan is adopted. Using the worst-performing radio as the single criterion for adopting a new channel plan can result in pinning or cascading problems.

Pinning occurs when the algorithm could find a better channel plan for some of the radios in an RF group but is prevented from pursuing such a channel plan change because the worst radio in the network does not have any better channel options. The worst radio in the RF group could potentially prevent other radios in the group from seeking better channel plans. The larger the network, the more likely pinning becomes.

Cascading occurs when one radio’s channel change results in successive channel changes to optimize the remaining radios in the RF neighborhood. Optimizing these radios could lead to their neighbors and their neighbors’ neighbors having a suboptimal channel plan and triggering their channel optimization. This effect could propagate across multiple floors or even multiple buildings, if all the access point radios belong to the same RF group. This change results in considerable client confusion and network instability.

The main cause of both pinning and cascading is the way in which the search for a new channel plan is performed and that any potential channel plan changes are controlled by the RF circumstances of a single radio. In Cisco WLC software release 6.0, the DCA algorithm has been redesigned to prevent both pinning and cascading. The following changes have been implemented:

Multiple local searches—The DCA search algorithm performs multiple local searches initiated by different radios within the same DCA run rather than performing a single global search driven by a single radio. This change addresses both pinning and cascading while maintaining the desired flexibility and adaptability of DCA and without jeopardizing stability.

Multiple channel plan change initiators (CPCIs)—Previously, the single worst radio was the sole initiator of a channel plan change. Now each radio within the RF group is evaluated and prioritized as a potential initiator. Intelligent randomization of the resulting list ensures that every radio is eventually evaluated, which eliminates the potential for pinning.

Limiting the propagation of channel plan changes (Localization)—For each CPCI radio, the DCA algorithm performs a local search for a better channel plan, but only the CPCI radio itself and its one-hop neighboring access points are actually allowed to change their current transmit channels. The impact of an access point triggering a channel plan change is felt only to within two RF hops from that access point, and the actual channel plan changes are confined to within a one-hop RF neighborhood. Because this limitation applies across all CPCI radios, cascading cannot occur.

Non-RSSI-based cumulative cost metric—A cumulative cost metric measures how well an entire region, neighborhood, or network performs with respect to a given channel plan. The individual cost metrics of all access points in that area are considered in order to provide an overall understanding of the channel plan’s quality. These metrics ensure that the improvement or deterioration of each single radio is factored into any channel plan change. The objective is to prevent channel plan changes in which a single radio improves but at the expense of multiple other radios experiencing a considerable performance decline.

The RRM algorithms run at a specified updated interval, which is 600 seconds by default. Between update intervals, the RF group leader sends keepalive messages to each of the RF group members and collects real-time RF data.

Several monitoring intervals are also available. See the Configuring RRM section for details.

A Cisco WLC is configured with an RF group name, which is sent to all access points joined to the Cisco WLC and used by the access points as the shared secret for generating the hashed MIC in the neighbor messages. To create an RF group, you configure all of the Cisco WLCs to be included in the group with the same RF group name.

If there is any possibility that an access point joined to a Cisco WLC may hear RF transmissions from an access point on a different Cisco WLC, you should configure the Cisco WLCs with the same RF group name. If RF transmissions between access points can be heard, then system-wide RRM is recommended to avoid 802.11 interference and contention as much as possible.

Controller software supports up to 20 controllers and 6000 access points in an RF group.

The RF group members are added based on the following criteria:

Maximum number of APs Supported: The maximum limit for the number of access points in an RF group is 6000. The number of access points supported is determined by the number of APs licensed to operate on the controller.

Twenty controllers: Only 20 controllers (including the leader) can be part of an RF group if the sum of the access points of all controllers combined is less than or equal to the upper access point limit.

Table 3 Controller Model Information
	8500	7500	5500	WiSM2
Maximum APs per RRM Group	6000	6000	1000	2000
Maximum AP Groups	6000	6000	500	500

This section describes how to configure RF groups through either the GUI or the CLI.

The RF group name is generally set at deployment time through the Startup Wizard. However, you can change it as necessary.

When the multiple-country feature is being used, all Cisco WLCs intended to join the same RF group must be configured with the same set of countries, configured in the same order.

You can also configure RF groups using the Cisco Prime Infrastructure.

Choose Controller > General to open the General page.
	Enter a name for the RF group in the RF-Network Name text box. The name can contain up to 19 ASCII characters.
	Click Apply to commit your changes.
	Click Save Configuration to save your changes.
	Repeat this procedure for each controller that you want to include in the RF group.

Create an RF group by entering the config network rf-network-name name command:

Enter up to 19 ASCII characters for the group name.

Viewing the RF Group Status

This section describes how to view the status of the RF group through either the GUI or the CLI.

You can also view the status of RF groups using the Cisco Prime Infrastructure.

Choose Wireless > 802.11a/n > or 802.11b/g/n > RRM > RF Grouping to open the 802.11a/n (or 802.11b/g/n) RRM > RF Grouping page.

This page shows the details of the RF group, displaying the configurable parameter RF Group mode, the RF Group role of this Cisco WLC, the Update Interval and the Cisco WLC name and IP address of the Group Leader to this Cisco WLC.

RF grouping mode can be set using the Group Mode drop-down list.

Tip Once a Cisco WLC has joined as a static member and you want to change the grouping mode, we recommend that you remove the member from the configured static-leader and also make sure that a member Cisco WLC has not been configured to be a member on multiple static leaders. This is to avoid repeated join attempts from one or more RF static leaders.

See which Cisco WLC is the RF group leader for the 802.11a RF network by entering this command: show advanced 802.11a group

Information similar to the following appears:

Radio RF Grouping 802.11a Group Mode............................. STATIC 802.11a Group Update Interval.................. 600 seconds 802.11a Group Leader........................... test (209.165.200.225) 802.11a Group Member......................... test (209.165.200.225) 802.11a Last Run............................... 397 seconds ago

This output shows the details of the RF group, specifically the grouping mode for the Cisco WLC, how often the group information is updated (600 seconds by default), the IP address of the RF group leader, the IP address of this Cisco WLC, and the last time the group information was updated.

If the IP addresses of the group leader and the group member are identical, this Cisco WLC is currently the group leader.

A * indicates that the Cisco WLC has not joined as a static member.

Overriding RRM

In some deployments, it is desirable to statically assign channel and transmit power settings to the access points instead of relying on the RRM algorithms provided by Cisco. Typically, this is true in challenging RF environments and non standard deployments but not the more typical carpeted offices.

If you choose to statically assign channels and power levels to your access points and/or to disable dynamic channel and power assignment, you should still use automatic RF grouping to avoid spurious rogue device events.

You can disable dynamic channel and power assignment globally for a Cisco WLC, or you can leave dynamic channel and power assignment enabled and statically configure specific access point radios with a channel and power setting. While you can specify a global default transmit power parameter for each network type that applies to all the access point radios on a Cisco WLC, you must set the channel for each access point radio when you disable dynamic channel assignment. You may also want to set the transmit power for each access point instead of leaving the global transmit power in effect.

We recommend that you assign different nonoverlapping channels to access points that are within close proximity to each other. The nonoverlapping channels in the U.S. are 36, 40, 44, 48, 52, 56, 60, 64, 149, 153, 157, and 161 in an 802.11a network and 1, 6, and 11 in an 802.11b/g network.

Do not assign all access points that are within close proximity to each other to the maximum power level.

Statically Assigning Channel and Transmit Power Settings to Access Point Radios

Choose Wireless > Access Points > Radios > 802.11a/n or 802.11b/g/n to open the 802.11a/n (or 802.11b/g/n) Radios page.

This page shows all the 802.11a/n or 802.11b/g/n access point radios that are joined to the Cisco WLC and their current settings. The Channel text box shows both the primary and extension channels and uses an asterisk to indicate if they are globally assigned.

Hover your cursor over the blue drop-down arrow for the access point for which you want to modify the radio configuration and choose Configure. The 802.11a/n (or 802.11b/g/n) Cisco APs > Configure page appears.

Specify the RF Channel Assignment from the following options: Global—Choose this to specify a global value. Custom—Choose this and then select a value from the adjacent drop-down list to specify a custom value.

Configure the antenna parameters for this radio as follows:

From the Antenna Type drop-down list, choose Internal or External to specify the type of antennas used with the access point radio.

Select and unselect the check boxes in the Antenna text box to enable and disable the use of specific antennas for this access point, where A, B, and C are specific antenna ports. The D antenna appears for the Cisco 3600 Series Access Points. A is the right antenna port, B is the left antenna port, and C is the center antenna port. For example, to enable transmissions from antenna ports A and B and receptions from antenna port C, you would select the following check boxes: Tx: A and B and Rx: C. In 3600 APs, the valid combinations are A, A+B, A+B+C or A+B+C+D. When you select a dual mode antenna, you can only apply single spatial 802.11n stream rates: MCS 0 to 7 data rates. When you select two dual mode antennae, you can apply only the two spatial 802.11n stream rates: MCS 0 to 15 data rates.

In the Antenna Gain text box, enter a number to specify an external antenna’s ability to direct or focus radio energy over a region of space. High-gain antennas have a more focused radiation pattern in a specific direction. The antenna gain is measured in 0.5 dBi units, and the default value is 7 times 0.5 dBi, or 3.5 dBi.

If you have a high-gain antenna, enter a value that is twice the actual dBi value (see Cisco Aironet Antenna Reference Guide for antenna dBi values). Otherwise, enter 0. For example, if your antenna has a 4.4-dBi gain, multiply the 4.4 dBi by 2 to get 8.8 and then round down to enter only the whole number (8). The Cisco WLC reduces the actual equivalent isotropic radiated power (EIRP) to make sure that the antenna does not violate your country’s regulations.

Choose one of the following options from the Diversity drop-down list:

Enabled—Enables the antenna connectors on both sides of the access point. This is the default value.

Side A or Right—Enables the antenna connector on the right side of the access point.

Side B or Left—Enables the antenna connector on the left side of the access point.

In the RF Channel Assignment area, choose Custom for the Assignment Method under RF Channel Assignment and choose a channel from the drop-down list to assign an RF channel to the access point radio.

In the Tx Power Level Assignment area, choose the Custom assignment method and choose a transmit power level from the drop-down list to assign a transmit power level to the access point radio.

The transmit power level is assigned an integer value instead of a value in mW or dBm. The integer corresponds to a power level that varies depending on the regulatory domain in which the access points are deployed. The number of available power levels varies based on the access point model. However, power level 1 is always the maximum power level allowed per country code setting, with each successive power level representing 50% of the previous power level. For example, 1 = maximum power level in a particular regulatory domain, 2 = 50% power, 3 = 25% power, 4 = 12.5% power, and so on.

See the hardware installation guide for your access point for the maximum transmit power levels supported per regulatory domain. Also, see the data sheet for your access point for the number of power levels supported.

If the access point is not operating at full power, the “Due to low PoE, radio is transmitting at degraded power” message appears under the Tx Power Level Assignment section.

Disable the radio of a particular access point on the 802.11a/n or 802.11b/g/n network by entering this command:

config { 802.11a | 802.11b} disable Cisco_AP

Configure the channel width for a particular access point by entering this command:

config { 802.11a | 802.11b} chan_width Cisco_AP { 20 | 40}

where

20 allows the radio to communicate using only 20-MHz channels. Choose this option for legacy 802.11a radios, 20-MHz 802.11n radios, or 40-MHz 802.11n radios that you want to operate using only 20-MHz channels. This is the default value.

40 allows 40-MHz 802.11n radios to communicate using two adjacent 20-MHz channels bonded together. The radio uses the primary channel that you choose as well as its extension channel for faster throughput. Each channel has only one extension channel (36 and 40 are a pair, 44 and 48 are a pair, and so on). For example, if you choose a primary channel of 44, the Cisco WLC would use channel 48 as the extension channel. If you choose a primary channel of 48, the Cisco WLC would use channel 44 as the extension channel.

This parameter can be configured only if the primary channel is statically assigned.

Statically configuring an access point’s radio for 20-MHz or 40-MHz mode overrides the globally configured DCA channel width setting (configured using the config advanced 802.11a channel dca chan-width-11n { 20 | 40} command). If you ever change the static configuration back to global on the access point radio, the global DCA configuration overrides the channel width configuration that the access point was previously using. It can take up to 30 minutes (depending on how often DCA is configured to run) for the change to take effect.

Channels 116, 120, 124, and 128 are not available in the U.S. and Canada for 40-MHz channel bonding.

config { 802.11a | 802.11b } 11nsupport antenna { tx | rx } Cisco_AP { A | B | C } { enable | disable }

where A, B, and C are antenna ports. A is the right antenna port, B is the left antenna port, and C is the center antenna port. For example, to enable transmissions from the antenna in access point AP1’s antenna port C on the 802.11a network, you would enter this command:

config 802.11a 11nsupport antenna tx AP1 C enable

config { 802.11a | 802.11b } antenna extAntGain antenna_gain Cisco_AP

High-gain antennas have a more focused radiation pattern in a specific direction. The antenna gain is measured in 0.5 dBi units, and the default value is 7 times 0.5 dBi, or 3.5 dBi.

config { 802.11a | 802.11b } channel ap Cisco_AP channe l

For example, to configure 802.11a channel 36 as the default channel on AP1, enter the   config 802.11a channel ap AP1 36 command.

The channel you choose is the primary channel (for example, channel 36), which is used for communication by legacy 802.11a radios and 802.11n 20-MHz radios. 802.11n 40-MHz radios use this channel as the primary channel but also use an additional bonded extension channel for faster throughput, if you chose 40 for the channel width.

Changing the operating channel causes the access point radio to reset.

config { 802.11a | 802.11b } txPower ap Cisco_AP power_level

For example, to set the transmit power for 802.11a AP1 to power level 2, enter the  config 802.11a txPower ap AP1 2 command.

In certain cases, Cisco access points support only 7 power levels for certain channels, so that the Cisco Wireless Controller considers the 7th and 8th power levels as the same. If the 8th power level is configured on those channels, the configuration would fail since the controller considers the 7th power level as the lowest acceptable valid power level. These power values are derived based on the regulatory compliance limits and minimum hardware limitation which varies across different Cisco access points. For example, Cisco 3500, 1140, and 1250 series access points allow the configuration of last power levels because those access points report the "per path power" to the controller, whereas all next generation acess points such as Cisco 3700, 3600, 2600, and 1600 series access points report "total power value" to the controller, thereby decreasing the allowed power levels for newer generation products. For example, if the last power level in the 3600E access point has a power value of 4dbm (total power), then it actually means the power value is -2dbm (per path).

See the hardware installation guide for your access point for the maximum transmit power levels supported per regulatory domain. Also, see data sheet for your access point for the number of power levels supported.

config { 802.11a | 802.11b } enable Cisco_AP

show ap config { 802.11a | 802.11b } Cisco_AP

Information similar to the following appears:

Disabling Dynamic Channel and Power Assignment Globally for a Controller

Choose Wireless > 802.11a/n or 802.11b/g/n > RRM > Auto RF to open the 802.11a/n (or 802.11b/g/n) Global Parameters > Auto RF page.
	Disable dynamic channel assignment by choosing OFF under RF Channel Assignment.
	Disable dynamic power assignment by choosing Fixed under Tx Power Level Assignment and choosing a default transmit power level from the drop-down list.
	Click Apply.
	Click Save Configuration.
	If you are overriding the default channel and power settings on a per radio basis, assign static channel and power settings to each of the access point radios that are joined to the Cisco WLC.
	(Optional) Repeat this procedure for the network type that you did not select (802.11a/n or 802.11b/g/n).

Disable the 802.11a or 802.11b/g network by entering this command:

config { 802.11a | 802.11b} disable network

Disable RRM for all 802.11a or 802.11b/g radios and set all channels to the default value by entering this command:

config { 802.11a | 802.11b} channel global off

Enable the 802.11a or 802.11b/g network by entering this command:

config { 802.11a | 802.11b} enable network

To enable the 802.11g network, enter the config 802.11b 11gSupport enable command after the config 802.11b enable network command.

Configuring Rogue Access Point Detection in RF Groups

After you have created an RF group of Cisco WLCs, you need to configure the access points connected to the Cisco WLCs to detect rogue access points. The access points will then select the beacon/probe-response frames in neighboring access point messages to see if they contain an authentication information element (IE) that matches that of the RF group. If the select is successful, the frames are authenticated. Otherwise, the authorized access point reports the neighboring access point as a rogue, records its BSSID in a rogue table, and sends the table to the Cisco WLC.

Make sure that each Cisco WLC in the RF group has been configured with the same RF group name.

The name is used to verify the authentication IE in all beacon frames. If the Cisco WLCs have different names, false alarms will occur.

The name of the RF group to which this Cisco WLC belongs appears at the top of the page.

The valid threshold range is from1 to 255, and the default threshold value is 1. To avoid false alarms, you may want to set the threshold to a higher value.

If rogue access point detection is not enabled on every Cisco WLC in the RF group, the access points on the Cisco WLCs with this feature disabled are reported as rogues.

config ap mode local Cisco_AP or config ap mode monitor Cisco_AP

config wps ap-authentication threshold

The valid threshold range is from 1 to 255, and the default threshold value is 1. To avoid false alarms, you may want to set the threshold to a higher value.

Configuring CCX Radio Management Features

Information about ccx radio management features.

You can configure two parameters that affect client location calculations:

Radio measurement requests

Location calibration

These parameters are supported in Cisco Client Extensions (CCX) v2 and later releases are designed to enhance location accuracy and timeliness for participating CCX clients.

For the location features to operate properly, the access points must be configured for normal, monitor, or FlexConnect mode. However, for FlexConnect mode, the access point must be connected to the Cisco WLC.

When you enable the radio measurements requests feature, lightweight access points issue broadcast radio measurement request messages to clients running CCXv2 or later releases. The access points transmit these messages for every SSID over each enabled radio interface at a configured interval. In the process of performing 802.11 radio measurements, CCX clients send 802.11 broadcast probe requests on all the channels specified in the measurement request. The Cisco Location Appliance uses the uplink measurements based on these requests received at the access points to quickly and accurately calculate the client location. You do not need to specify on which channels the clients are to measure. The Cisco WLC, access point, and client automatically determine which channels to use.

The radio measurement feature enables the Cisco WLC to also obtain information on the radio environment from the client’s perspective (rather than from just that of the access point). In this case, the access points issue unicast radio measurement requests to a particular CCXv4 or v5 client. The client then sends various measurement reports back to the access point and onto the Cisco WLC. These reports include information about the radio environment and data used to interpret the location of the clients. To prevent the access points and Cisco WLC from being overwhelmed by radio measurement requests and reports, only two clients per access point and up to 20 clients per Cisco WLC are supported. You can view the status of radio measurement requests for a particular access point or client as well as radio measurement reports for a particular client from the Cisco WLC CLI.

The Cisco WLC software improves the ability of the mobility services engine to accurately interpret the location of a device through a CCXv4 feature called location-based services. The Cisco WLC issues a path-loss request to a particular CCXv4 or v5 client. If the client chooses to respond, it sends a path-loss measurement report to the Cisco WLC. These reports contain the channel and transmit power of the client.

Non-CCX and CCXv1 clients ignore the CCX measurement requests and do not participate in the radio measurement activity.

For CCX clients that need to be tracked more closely (for example, when a client calibration is performed), the Cisco WLC can be configured to command the access point to send unicast measurement requests to these clients at a configured interval and whenever a CCX client roams to a new access point. These unicast requests can be sent out more often to these specific CCX clients than the broadcast measurement requests, which are sent to all clients. When location calibration is configured for non-CCX and CCXv1 clients, the clients are forced to disassociate at a specified interval to generate location measurements.

Configuring CCX Radio Management

Choose Wireless > 802.11a/n or 802.11b/g/n > Network to open the 802.11a/n (or 802.11b/g/n) Global Parameters page.

Under CCX Location Measurement, select the Mode check box to globally enable CCX radio management. This parameter causes the access points connected to this Cisco WLC to issue broadcast radio measurement requests to clients running CCX v2 or later releases. The default value is disabled (or unselected).

If you selected the Mode check box in the previous step, enter a value in the Interval text box to specify how often the access points are to issue the broadcast radio measurement requests.

The range is 60 to 32400 seconds.

The default is 60 seconds.

Click Apply.

Click Save Configuration.

Follow the instructions in of the section below to enable access point customization.

To enable CCX radio management for a particular access point, you must enable access point customization, which can be done only through the Cisco WLC CLI.

Globally enable CCX radio management by entering this command:

config advanced { 802.11a | 802.11b} ccx location-meas global enable interval_seconds

The range for the interval_seconds parameter is 60 to 32400 seconds, and the default value is 60 seconds. This command causes all access points connected to this Cisco WLC in the 802.11a or 802.11b/g network to issue broadcast radio measurement requests to clients running CCXv2 or later releases.

Enable access point customization by entering these commands:

config advanced { 802.11a | 802.11b} ccx customize Cisco_AP { on | off}

This command enables or disables CCX radio management features for a particular access point in the 802.11a or 802.11b/g network.

config advanced { 802.11a | 802.11b} ccx location-meas ap Cisco_AP enable interval_seconds

The range for the interval_seconds parameter is 60 to 32400 seconds, and the default value is 60 seconds. This command causes a particular access point in the 802.11a or 802.11b/g network to issue broadcast radio measurement requests to clients running CCXv2 or higher.

Save your settings by entering this command: save config

To see the CCX broadcast location measurement request configuration for all access points connected to this Cisco WLC in the 802.11a or 802.11b/g network, enter this command:

show advanced { 802.11a | 802.11b } ccx global

To see the CCX broadcast location measurement request configuration for a particular access point in the 802.11a or 802.11b/g network, enter this command:

show advanced { 802.11a | 802.11b } ccx ap Cisco_AP

To see the status of radio measurement requests for a particular access point, enter this command:

show ap ccx rm Cisco_AP status

To see the status of radio measurement requests for a particular client, enter this command:

show client ccx rm client_mac status

To see radio measurement reports for a particular client, enter these commands:

show client ccx rm client_mac report beacon —Shows the beacon report for the specified client.

show client ccx rm client_mac report chan-load —Shows the channel-load report for the specified client.

show client ccx rm client_mac report noise-hist —Shows the noise-histogram report for the specified client.

show client ccx rm client_mac report frame —Shows the frame report for the specified client.

To see the clients configured for location calibration, enter this command:

show client location-calibration summary

To see the RSSI reported for both antennas on each access point that heard the client, enter this command:

show client detail client_mac

Debug CCX broadcast measurement request activity by entering this command:

debug airewave-director message { enable | disable }

Debug client location calibration activity by entering this command:

debug ccxrm [ all | error | warning | message | packet | detail { enable | disable }]

The CCX radio measurement report packets are encapsulated in Internet Access Point Protocol (IAPP) packets. Therefore, if the previous debug ccxrm command does not provide any debugs, enter this command to provide debugs at the IAPP level:

debug iapp error { enable | disable }

Debug the output for forwarded probes and their included RSSI for both antennas by entering this command:

debug dot11 load-balancing

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IMAGES

Classification of Channel Assignment Algorithms
Channel Assignment Strategies: Concept, Need, Fixed and Dynamic Channel
Greedy algorithm for power optimisation using dynamic channel
Figure 11 from A dynamic channel assignment algorithm for a hybrid TDMA
Figure 1 from A dynamic channel assignment algorithm for voice and data
Figure 1 from A dynamic channel assignment algorithm for cellular

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The Dynamic Channel Assignment (DCA) Algorithm. • Can dynamically determine best bandwidth for each AP (DBS v.8.1) Figure 1: When a new AP is added, it's radio conflicts with an existing AP's radio causing contention. DCA adjusts the channel plan for the best solution for the new AP. DCA's job is to monitor the available channels for the RF ...
Configuring DCA
Dynamic Channel Assignment (DCA) handled by RF group leader for a particular RF group. DCA algorithm takes following information into account 1. Load Measurement (Every AP measure the % total time occupied by Tx or Rx 802.11 frames) 2. Noise (APs calculate noise value on all serviced channels) 3. Interference (APs report on % medium…
PDF Dynamic Channel Assignment in IEEE 802.11 Networks
A. Dynamic Channel Assignment for WLAN with 4 APs Initially, we place 4 APs to simulate the WLAN. Setting ini-tially all APs to the same channels, we simulate our dynamic channel assignment algorithm for 100 runs while recording the interference and channel assignment from each run. We calculate the total interference in dBm for algorithm I and II
Changing DCA and TxPowerLevelAssignment Interval
Hi Michael, Sadly this number (600 seconds/10 minutes) is not able to be changed; Transmit Power Control Algorithm . The TPC algorithm, run at a fixed ten minute interval by default, is used by the RF Group Leader to determine the APs' RF proximities and adjust each band's transmit power level lower to limit excessive cell overlap and co-channel interference.
Dynamic Channel Assignment in IEEE 802.11 Networks
We design a dynamic channel assignment algorithm for IEEE 802.11 wireless networks. Our algorithm assigns channels dynamically in a way that minimizes channel interference generated by neighboring access points (APs) on a reference access point, resulting in higher throughput. We implement and simulate our algorithm using two versions (I: pick rand and II: pick first) and different number of ...
Performance issues and algorithms for dynamic channel assignment
Using dynamic channel assignment (DCA) algorithms to select communications channels as needed, time-division multiple access (TDMA) or frequency-division multiple access (FDMA) systems can serve dynamic and nonuniform traffic demands without frequency planning as long as quality is sufficient and equipment is available.
Automatic Channel Assignment Mode (DCA)
Our current setting on Channel Assignment Method is Automatic and the interval set is 10 minutes. This works for both b/g and a radios. So I'm understanding that the controller should be changing the channel of all APs automatically for every 10 minutes. But I checked my running config on WLC Config Analyzer and found out that the last channel ...
PDF Dynamic Channel Assignment (DCA)
The Dynamic Channel Assignment (DCA) Algorithm. The Group Leader maintains the neighbor lists for all AP's in the RF Group, and organizes these neighbors into RF Neighborhoods. The following metrics are also tracked for each AP in the RF Group. Same Channel Contention—other AP's/clients on the same channel - also known as Co-Channel ...
CTS 104: Cisco DCA
DCA, or Dynamic Channel Assignment, is a core component of Cisco Radio Resource Management (RRM). It runs a critical algorithm which dynamically changes an access points (AP) client serving channel based on multiple parameters, collectively called a Cost Metric. ... Automatic will run the DCA algorithm at the define Interval which is every 10 ...
A dynamic channel assignment algorithm for IEEE 802.11 WLAN
This paper presents a Dynamic Channel Assignment (DCA) algorithm implemented in Matlab. It uses a cross-correlation of power spectral density (PSD) estimations of individual WLAN channels. Estimations are based on Received Signal Strength Indicator (RSSI) level from different channels of individual clients in the IEEE 802.11 WLAN. Based on RSSI and current clients' needs for channel bandwidth ...
Dynamic Channel Assignment
An on-demand dynamic channel assignment mechanism ... S then sends an ATIM-RES packet to D so that the pair of nodes reserve the channel for data interval. ... [20], the distance-1 constrained channel assignment algorithm [21], and the sequence based channel assignment algorithm [32] ...
PDF Dynamic Channel Assignment Techniques Liang Yong [email protected]
— acquires the channel that is being used by the nearest BS at distance or greater • Nearest Neighbour+1 (NN+1) — acquires the channel that is in use at the nearest BS at distance +1 or greater • Mean Square (MSQ) — assigns the available channel that minimizes the mean square of the distances among all BSs using the same channel DN DN
PDF Dynamic Channel Allocation
Dynamic Channel Allocation • Channel allocation based on real time measurements - All the channels in a common pool - Channels allocated based on the situation in the network • Teletraffic point of view • FCA operates as a set of small servers • DCA as a big pool of servers Classification of DCA algorithms -x•FCAFi
Cisco Wireless LAN Controller Configuration Guide, Release 7.4
The controller 's Dynamic Channel Assignment (DCA) capabilities are also useful in minimizing adjacent channel interference between access points. For example, two overlapping channels in the 802.11b/g band, such as 1 and 2, cannot simultaneously use 11 or 54 Mbps. ... DCA algorithm interval is set to 1 hour, but DCA algorithm always runs in ...
Performance issues and algorithms for dynamic channel assignment
Using dynamic channel assignment (DCA) algorithms to select communications channels as needed, time-division multiple access (TDMA) or frequency-division multiple access (FDMA) systems can serve dynamic and nonuniform traffic demands without frequency planning as long as quality is sufficient and equipment is available. Here, performance issues and algorithms for DCA in a TDMA portable radio ...
Dynamic Channel Assignment (DCA)
The Dynamic Channel Assignment (DCA) algorithm is used to automatically determine the most optimal AP channel. Skip to content . MixedNetworks. Home; Courses. Automation. Ansible; Cisco. Cisco ISE (Identity Services Engine) CCNP. ENCOR (350-401) ENWLSD (300-425) Contact; MixedNetworks. Home;
WLC Dynamic Channel Assignment issue
In response to cem.erman. 05-11-2015 11:27 PM. Hi Erman, First: I will say" use only channel 1, 6 and 11" in DCA channel list. Give a Try: just assign the TPC to all AP to "1" (Maximum)- Fixed, then you will see change in channels. 2nd: Also paste the output from: Wireless > All APs > Radios > 802.11b/g/n. Regards.
Radio Resource Management under Unified Wireless Networks
Last Channel Assignment—The DCA algorithm runs every 600 seconds (10 minutes). This field only indicates the time (in seconds) since the algorithm last ran and not necessarily the last time a new channel assignment was made. Figure 11: Dynamic Channel Assignment Algorithm Configuration. Tx Power Level Assignment Settings via the WLC GUI
Cisco 9800 WLC Client Disconnections
DCA Algorithm Interval. Recommendation: ... Dynamic Channel Assignment algorithm is a process responsible for assigning the channel to all APs and runs by default every 10 minutes. This means that ...
Cisco Wireless LAN Controller Configuration Guide, Release 7.3
DCA algorithm interval is set to one hour, but DCA algorithm always runs in default interval of 10min, channel allocation happens for every 10min interval for the first 10 cycles, and channel changes as per DCA algorithm for every 10min. ... In Cisco WLC software releases prior to 6.0, the dynamic channel assignment (DCA) search algorithm ...