Configuration Guide Configuring Band Select
Active scanning: The STA broadcasts a Probe Request frame on all channels of all supported bands. After receiving
the Probe Request frame, the APs providing WLAN access service sends a Probe Response frame including some
WLAN information to the STA.
Generally, the STA summarizes the SSIDs of all discovered WLANs and provides an accessible WLAN list for users.
Dual-band STA
WLAN network interface cards (WNICs) used by STAs to connect to WLANs are classified into a, b, g and n types, which
indicate the 802.11 protocol types supported by the WNICs. 802.11a operates at 5 GHz, 802.11b/g at 2.4 GHz, and
802.11n at 5 GHz and 2.4 GHz.
Therefore, if the specification of a WNIC includes both a and b/g, this WNIC supports both the two bands, namely, a
dual-band STA. A dual-band STA can access both the 5 GHz band and the 2.4 GHz band.
Dual-band AP
A dual-band AP is able to access two bands. Therefore, a dual-band AP requires at least two RF interfaces, one for 5 GHz
and the other for 2.4 GHz.
A WLAN enabled with Band Select must be mapped to the two RF interfaces of the dual-band AP and provides access
service at the two bands.
Overview
The Band Select function identifies whether an STA is a dual-band STA.
Controlling the Active Scanning Process
The Band Select function controls active scanning of the dual-band STA to
prevent the STA from discovering WLANs of the 2.4 GHz band.
Rejecting Accessing the 2.4 GHz Band
The Band Select function rejects the dual-band STA from accessing the 2.4
GHz band and improves the chance of accessing the 5 GHz band.
2.3.1 Identifying STA Types
To lead a dual-band STA to access the 5 GHz band, you should first identify whether the STA is a dual-band STA; that is,
identify the band supported by the STA.
Working Principle
Active scanning is an approach for an STA to discover WLANs. When using active scanning, the STA sends a Probe
Request frame on each supported channel. If the channel information in the Probe Request frame sent by the STA can be
obtained, the bands supported by the STA can be identified.
For example, if an AP receives the Probe Request frame on channels 1-13, the AP learns that the STA supports the 2.4
GHz band. If the AP receives the Probe Request frame on channels 149-165, the AP learns that the STA supports the 5
GHz band.
Since a single-band AP can receive the Probe Request frame only at one band, only a dual-band AP can correctly identify
the STA type. This is why the Band Select function requires a dual-band AP be used.
STA Classification Standards
A dual-band AP classifies STAs based on the following standards:
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