Windows Vista and later includes a shared-spectrum model to support AFH for Bluetooth radios that are based on version 2.0 and later versions of the Bluetooth specification. However, this feature is disabled by default. For a system to support the shared spectrum model, the OEM must explicitly enable the feature and specify the width of the frequency band that should be blocked around an active Wi Fi channel. To specify the width of the frequency band, create a value of type REG_DWORD that is named ChannelAvoidanceRange under the following registry key:
HKLM\\System\\CurrentControlSet\\Services\\BthServ\\Parameters
The ChannelAvoidanceRange value enables or disables spectrum sharing and specifies the width of the blocked frequency band. To enable spectrum sharing, set ChannelAvoidanceRange to the full width of the frequency band that should be blocked around an active Wi-Fi channel. The units are in MHz and can range from 20 to 40 (0.02 to 0.04 GHz). OEMs must determine an appropriate bandwidth based on a selected set of radios, antenna characteristics, and radio manufacturer feedback.
A new ChannelAvoidanceRange value takes effect only after the system has been rebooted. Ideally, the OEM should set the ChannelAvoidanceRange value during the preinstallation process.
For the Windows shared-spectrum model to work effectively, Wi-Fi miniport drivers must report their channel usage to the networking connections manager. The networking stack then passes the channel-use information to the Bluetooth stack.