08-Radio Resources Management

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06-Channel scanning configuration
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06-Channel scanning configuration 89.06 KB

Configuring channel scanning

About channel scanning

Channel scanning enables APs to scan channels and capture wireless packets. The device analyzes the captured wireless packets to obtain wireless service information, including interferences, error bit rate, and wireless signal strength. Channel scanning provides data for WLAN RRM and WIPS, and enhances wireless service quality.

Basic concepts

·     Scanning period—In this period, an AP only scans a channel and does not provide wireless services.

·     Service period—In this period, an AP scans its working channel and provides wireless services simultaneously for a time period that is the same as the scanning period. After that, the AP only provides wireless services.

Work mechanism

An AP scans each channel on the channel scanning list in turn regardless of whether the AP provides wireless services, and each channel is scanned for a scanning period. If the AP does not provide wireless services, it starts scanning periods consecutively. If the AP provides wireless services, it starts service periods and scanning periods alternatively.

For example, Figure 1 shows the channel scanning mechanism for an AP when the AP works on channel 6 and the channel scanning list contains channels 1, 6, and 11.

Figure 1 Channel scanning mechanism

 

Channel scanning tasks at a glance

To configure channel scanning, perform the following tasks:

·     Setting the scanning period

·     Setting the maximum service period

·     Setting the service idle timeout timer

·     (Optional.) Configuring the channel scanning blacklist or whitelist

·     (Optional.) Configuring all-channel scanning

·     (Optional.) Scanning only the working channel

Setting the scanning period

About this task

The scanning period defines the time period in which an AP scans a channel. In a service period, an AP scans its working channel and provides wireless services simultaneously for a time period that is the same as the scanning period.

Restrictions and guidelines

The scanning period cannot be greater than the maximum service period.

Procedure

1.     Enter system view.

system-view

2.     Enter radio interface view.

interface wlan-radio interface-number

3.     Set the scanning period.

scan scan-time scan-time

By default, the scanning period is 100 milliseconds.

Setting the maximum service period

About this task

To ensure both scanning and service quality, you can set the maximum service period. When the maximum service period is reached, the AP starts a scanning period regardless of whether it has traffic to forward. To ensure wireless service quality, you can configure the AP to not limit the service period. The AP does not start a scanning period unless the service idle timeout timer expires.

Procedure

1.     Enter system view.

system-view

2.     Enter radio interface view.

interface wlan-radio interface-number

3.     Set the maximum service period.

scan max-service-time { max-service-time | no-limit }

By default, the maximum service period is not limited. An AP does not start a scanning period unless the service idle timeout timer expires.

Setting the service idle timeout timer

About this task

During a service period, an AP does not begin a new scanning period until the current service period exceeds the scanning period even if the specified service idle timeout timer expires.

Restrictions and guidelines

The service idle timeout timer cannot be greater than the maximum service period.

Procedure

1.     Enter system view.

system-view

2.     Enter radio interface view.

interface wlan-radio interface-number

3.     Set the service idle timeout timer.

scan idle-time idle-time

By default, the service idle timeout timer is 100 milliseconds.

Configuring the channel scanning blacklist or whitelist

About this task

If you configure the blacklist for an AP, the AP will not scan non-working channels in the blacklist. If you configure the whitelist for an AP, the AP will scan only channels in the whitelist and the working channel.

Restrictions and guidelines

You cannot configure both the channel scanning blacklist and whitelist for the same AP.

Procedure

1.     Enter system view.

system-view

2.     Enter radio interface view.

interface wlan-radio interface-number

3.     Choose one option as needed:

¡     Configure the channel scanning blacklist.

scan channel blacklist channel-list

¡     Configure the channel scanning whitelist.

scan channel whitelist channel-list

By default, no channel scanning blacklist or whitelist is configured.

Configuring all-channel scanning

About this task

An AP alternatively scans 2.4 GHz channels and 5 GHz channels at the specified interval when all-channel scanning is enabled. When all-channel scanning is disabled, an AP scans only channels of the configured band.

Restrictions and guidelines

This feature is applicable only to dual-band radios. As a best practice, do not enable all-channel scanning and wireless access services at the same time.

If you configure the settings of an AP such as radio mode, channel, bandwidth, and transmit power after enabling the AP to scan all channels, the configuration might not take effect.

Procedure

1.     Enter system view.

system-view

2.     Enter radio interface view.

interface wlan-radio interface-number

3.     Configure all-channel scanning.

scan mode all { disable | enable }

By default, all-channel scanning is disabled.

4.     Set the interval for the radio to scan all channels.

scan mode all interval interval-value

By default, the interval for an AP to scan all channels is 3000 milliseconds.

Scanning only the working channel

About this task

Enable this feature to enable an AP to scan only the working channel.

Procedure

1.     Enter system view.

system-view

2.     Enter radio interface view.

interface wlan-radio interface-number

3.     Enable the radio to scan only the working channel.

scan work-channel-only { disable | enable }

By default, a radio scans all supported channels in turn.

Channel scanning configuration examples

Example: Configuring relative forwarding preferred channel scanning

Network configuration

To ensure both channel scanning and wireless service quality, configure channel scanning and set the maximum service period for the AP, as shown in Figure 2.

Figure 2 Network diagram

Procedure

# Enter interface view of Radio 1/0/1.

<AP> system-view

[AP] interface wlan-radio 1/0/1

# Set the scanning period to 200 milliseconds.

[AP-WLAN-Radio1/0/1] scan scan-time 200

# Set the maximum service period to 5000 milliseconds.

[AP-WLAN-Radio1/0/1] scan max-service-time 5000

# Set the service idle timeout timer to 100 milliseconds.

[AP-WLAN-Radio1/0/1] scan idle-time 100

Example: Configuring absolute forwarding preferred channel scanning

Network configuration

To ensure wireless service quality, configure channel scanning and configure the AP to not limit the service period, as shown in Figure 3.

Figure 3 Network diagram

Procedure

# Enter interface view of Radio 1/0/1.

<AP> system-view

[AP] interface wlan-radio 1/0/1

# Set the scanning period to 100 milliseconds.

[AP-WLAN-Radio1/0/1] scan scan-time 100

# Configure the radio to not limit the service period.

[AP-WLAN-Radio1/0/1] scan max-service-time no-limit

# Set the service idle timeout timer to 100 milliseconds.

[AP-WLAN-Radio1/0/1] scan idle-time 100