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.
Band Selection
Band selection enables client radios that are capable of dual-band (2.4- and 5-GHz) operation to move to a less congested 5-GHz access point. The 2.4-GHz band is often congested. Clients on this band typically experience interference from Bluetooth devices, microwave ovens, and cordless phones as well as co-channel interference from other access points because of the 802.11b/g limit of three nonoverlapping channels. To prevent these sources of interference and improve overall network performance, you can configure band selection on the controller.
Band selection works by regulating probe responses to clients and it can be enabled on a per-WLAN basis. It makes 5-GHz channels more attractive to clients by delaying probe responses to clients on 2.4-GHz channels. In the access point, the band select table can be viewed by giving show dot11 band-select command. It can also be viewed from show cont d0/d1 | begin Lru.
Note | The WMM default configuration will not be shown in show running-config output. |
The band selection algorithm affects clients that use 2.4-GHz band. Initially, when a client sends a probe request to the access point, the corresponding client probe’s Active and Count values (as seen from the band select table) become 1. The algorithm functions based on the following scenarios:
Scenario - 1: Client RSSI (as seen from show cont d0/d1 | begin RSSI) is greater than both Mid-RSSI and Acceptable Client RSSI.
Dual band clients—No 2.4-GHz probe responses are seen at any time; 5-GHz probe responses are seen for all 5-GHz probe requests.
Single band (2.4-GHz) clients— 2.4-GHz probe responses are seen only after the probe suppression cycle.
After the client’s probe count reaches the configured probe cycle count, the algorithm waits for the Age Out Suppression time and then marks the client probe’s Active value as 0. Then, the algorithm is restarted.
Scenario - 2: Client RSSI (as seen from show cont d0/d1 | begin RSSI) lies between Mid-RSSI and Acceptable Client RSSI.
Note | The client RSSI value (seen as sh cont d0 | begin RSSI) is the average of the client packets received, and the Mid-RSSI feature is the instantaneous RSSI value of the probe packets. As a result, the client RSSI is seen as weaker than the configured Mid-RSSI value (7 dB delta). The 802.11b probes from the client are suppressed to push the client to associate with the 802.11a band. |
Band-selection enabled WLANs do not support time-sensitive applications like voice and video because of roaming delays.
Band selection can be used only with Cisco Aironet 1140, 1250, 1260, 1530, 1550, 1570, 1600, 1700, 1800, 2600, 2700, 2800, 3500, 3600, 3700, 3800 series access points.
Mid RSSI is not supported on Cisco Aironet 1600 Series access points.
Band selection is not supported in Cisco Aironet 1040, OEAP 600 series access points.
Band selection operates only on access points that are connected to a controller. A FlexConnect access point without a controller connection does not perform band selection after a reboot.
The band-selection algorithm directs dual-band clients only from the 2.4-GHz radio to the 5-GHz radio of the same access point, and it only runs on an access point when both the 2.4-GHz and 5-GHz radios are up and running.
You can enable both band selection and aggressive load balancing on the controller. They run independently and do not impact one another.
It is not possible to enable or disable band selection and client load balancing globally through the controller GUI or CLI. You can, however, enable or disable band selection and client load balancing for a particular WLAN. Band selection and client load balancing are enabled globally by default.
Configuring Band Selection
Short and Long Preambles
For the best integration with the Cisco UWN solution, SpectraLink NetLink Telephones require an extra operating system configuration step: enable long preambles. The radio preamble (sometimes called a header) is a section of data at the head of a packet that contains information that wireless devices need when sending and receiving packets. Short preambles improve throughput performance, so they are enabled by default. However, some wireless devices, such as SpectraLink NetLink phones, require long preambles.
Configuring SpectraLink NetLink Phones
Step 1 | Log on to the controller CLI. |
Step 2 | Enter the show 802.11b command and select the Short preamble mandatory parameter. If the parameter indicates that short preambles are enabled, continue with this procedure. This example shows that short preambles are enabled: Short Preamble mandatory....................... Enabled However, if the parameter shows that short preambles are disabled (which means that long preambles are enabled), the controller is already optimized for SpectraLink NetLink phones and you do not need to continue this procedure. |
Step 3 | Disable the 802.11b/g network by entering this command: You cannot enable long preambles on the 802.11a network. |
Step 4 | Enable long preambles by entering this command: |
Step 5 | Reenable the 802.11b/g network by entering this command: |
Step 6 | Enter the reset system command to reboot the controller. Enter y when the prompt to save the system changes is displayed. The controller reboots. |
Step 7 | Verify that the controller is properly configured by logging back into the CLI and entering the show 802.11b command to view these parameters: 802.11b Network................................ Enabled Short Preamble mandatory....................... Disabled These parameters show that the 802.11b/g network is enabled and that short preambles are disabled. |
To configure 802.11 enhanced distributed channel access (EDCA) parameters to support SpectraLink phones, use the following CLI commands:
config advanced edca-parameter {custom-voice | optimized-video-voice | optimized-voice | svp-voice | wmm-default}
custom-voice enables custom voice EDCA parameters
optimized-video-voice enables combined video-voice-optimized parameters
optimized-voice enables non-SpectraLink voice-optimized parameters
svp-voice enables SpectraLink voice priority (SVP) parameters
wmm-default enables wireless multimedia (WMM) default parameters
Note | To propagate this command to all access points connected to the controller, make sure to disable and then reenable the 802.11b/g network after entering this command. |
Receiver Start of Packet Detection Threshold (Rx-SOP)
Receiver Start of Packet Detection Threshold (RxSOP) determines the Wi-Fi signal level in dBm at which an access point's radio demodulates and decodes a packet. As the Wi-Fi level increases, the radio sensitivity decreases and the receiver cell size becomes smaller. Reduction of the cell size affects the distribution of clients in the network.
RxSOP is used to address clients with weak RF links, sticky clients, and client load balancing across access points. RxSOP helps to optimize the network performance at high-density deployments such as stadiums and auditoriums where access points need to optimize the nearest and strongest clients.
Note | RxSOP configuration is not applicable to the third radio module pluggable on a 3600 AP. |
Step 1 | Choose
to configure the high, medium, and low RxSOP threshold values for each 802.11 band. The table below shows the RxSOP threshold values for high, medium and low levels for each 802.11 band.
| ||||||||||||
Step 2 | Choose RF profiles page is displayed. to configure the RxSOP threshold value for an RF profile. The | ||||||||||||
Step 3 | Save the configuration. |
Verify information about RxSOP thresholds for an 802.11 band by using theshow {802.11a | 802.11b} extended command.
Step 1 | Configure RxSOP threshold values for each 802.11 band by entering this command:
config {802.11a | 802.11b} rx-sop threshold {high | medium | low | auto} {ap ap_name | default} You can configure the RxSOP thresholds for an access point or on all access points in an 802.11 band. |
Step 2 | Configure RxSOP threshold values for an RF profile by entering this command:
config rf-profile rx-sop threshold {high | medium | low | auto} profile_name |
Step 3 | View information about RxSOP thresholds for an 802.11 band by entering this command:
show {802.11a | 802.11b} extended (Cisco Controller) > show 802.11a extended
Default 802.11a band Radio Extended Configurations:
Beacon period: 100, range: 0 (AUTO);
Multicast buffer: 0 (AUTO), rate: 0 (AUTO);
RX SOP threshold: -76; CCA threshold: 0 (AUTO);
AP3600-XALE3 34:a8:4e:6a:7b:00
Beacon period: 100, range: 0 (AUTO);
Multicast buffer: 0 (AUTO), rate: 0 (AUTO);
RX SOP threshold: -76; CCA threshold: 0 (AUTO);
AP54B4 3c:ce:73:6c:42:f0
Beacon period: 100, range: 0 (AUTO);
Multicast buffer: 0 (AUTO), rate: 0 (AUTO);
RX SOP threshold: -76; CCA threshold: -80;
|