Re: How reduce the number of channel to be scanned in active scanning mode?

From: Jouni Malinen (
Date: 2002-07-19 14:05:31 UTC

On Thu, Jul 18, 2002 at 02:44:05PM +0200, Wenhui Zhang wrote:

> In order to reduce the handover delay, we plan to fixed the channel number,
> for example, 3. and let the mobile terminal only send Probe request in that
> channel. I find the defintion in prism2_wlan.h
> #define HFA384X_RID_CHANNELLIST 0xFD10
> What does this mean?

RID_CHANNELLIST (like all FD?? rids) is read-only and this just lists the supported channels (based on regional configuration made during card initial flash writing.

> If I want to limit the scan to only channel 3, how can I change?
> Is that all I need to do to limit the number of channels to be scanned?

Check Host AP driver's host-based roaming code (from the CVS version). HFA384X_RID_SCANREQUEST is used to configure channel list (bitmap) for scanning. Using HFA384X_RID_JOINREQUEST without waiting for new scan results might also be used to reduce handoff latency in some cases (e.g., when old scan results show another AP with raising signal quality and signal quality from current AP drops below some limit, etc.). I haven't tested limiting channels to be scanned or extra join requests, so I'm not sure whether they really work, but these are the parts I would experiment with.  

Jouni Malinen                                            PGP id EFC895FA

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