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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.
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.
Statically Assigning Channel and Transmit Power Settings to Access Point Radios
Step 1 | Disable the radio of a particular access point on the 802.11a/n/ac or 802.11b/g/n network by entering this command: | ||||||
Step 2 | Configure the
channel width for a particular access point by entering this command:
config {802.11a | 802.11b} chan_width Cisco_AP {20 | 40 | 80}
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Step 3 | Enable or
disable the use of specific antennas for a particular access point by entering
this command:
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
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Step 4 | Specify the
external antenna gain, which is a measure of an external antenna’s ability to
direct or focus radio energy over a region of space entering this command:
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. 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. | ||||||
Step 5 | Configure
beamforming for the 5-GHz radios for all APs or a specific by entering this
command:
config 802.11a {global | ap ap-name} {enable | disable} | ||||||
Step 6 | Specify the
channel that a particular access point is to use by entering this command:
config {802.11a | 802.11b} channel ap Cisco_AP channel 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.
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Step 7 | Specify the
transmit power level that a particular access point is to use by entering this
command:
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. 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. 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).
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Step 8 | Save your settings by entering this command: save config | ||||||
Step 9 | Repeat Step 2 through Step 7 for each access point radio for which you want to assign a static channel and power level. | ||||||
Step 10 | Reenable the access point radio by entering this command: | ||||||
Step 11 | Have the Cisco WLC send the access point radio admin state immediately to WCS by entering this command: | ||||||
Step 12 | Save your changes by entering this command: save config | ||||||
Step 13 | See the
configuration of a particular access point by entering this command:
show ap config {802.11a | 802.11b} Cisco_AP Information similar to the following appears: Cisco AP Identifier.............................. 7 Cisco AP Name.................................... AP1 ... Tx Power Num Of Supported Power Levels ............. 8 Tx Power Level 1 .......................... 20 dBm Tx Power Level 2 .......................... 17 dBm Tx Power Level 3 .......................... 14 dBm Tx Power Level 4 .......................... 11 dBm Tx Power Level 5 .......................... 8 dBm Tx Power Level 6 .......................... 5 dBm Tx Power Level 7 .......................... 2 dBm Tx Power Level 8 .......................... -1 dBm Tx Power Configuration .................... CUSTOMIZED Current Tx Power Level .................... 1 Phy OFDM parameters Configuration ............................. CUSTOMIZED Current Channel ........................... 36 Extension Channel ......................... 40 Channel Width.............................. 40 Mhz Allowed Channel List....................... 36,44,52,60,100,108,116,132, ......................................... 149,157 TI Threshold .............................. -50 Antenna Type............................... EXTERNAL_ANTENNA External Antenna Gain (in .5 dBi units).... 7 Diversity.................................. DIVERSITY_ENABLED 802.11n Antennas Tx A....................................... ENABLED B....................................... ENABLED Rx A....................................... DISABLED B....................................... DISABLED C.................................... ENABLED |
Disabling Dynamic Channel and Power Assignment Globally for a Cisco Wireless LAN Controller
Step 1 | Choose Wireless > 802.11a/n/ac or 802.11b/g/n > RRM > Auto RF to open the 802.11a/n/ac (or 802.11b/g/n) Global Parameters > Auto RF page. |
Step 2 | Disable dynamic channel assignment by choosing OFF under RF Channel Assignment. |
Step 3 | Disable dynamic power assignment by choosing Fixed under Tx Power Level Assignment and choosing a default transmit power level from the drop-down list. |
Step 4 | Click Apply. |
Step 5 | Click Save Configuration. |
Step 6 | 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. |
Step 7 | (Optional) Repeat this procedure for the network type that you did not select (802.11a/n/ac or 802.11b/g/n). |
Step 1 | Disable the 802.11a or 802.11b/g network by entering this command: | ||
Step 2 | Disable RRM for all 802.11a or 802.11b/g radios and set all channels to the default value by entering this command: | ||
Step 3 | Enable the 802.11a or 802.11b/g network by entering this command: config {802.11a | 802.11b} enable network
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Step 4 | Save your changes by entering this command: save config |