barker preamble bit in ERP IE

[Jouni Malinen]

On Wed, May 05, 2010 at 03:19:20PM +0300, ronit fichman wrote:
> may be set to 0. *The Barker_Preamble_Mode bit shall be set to 1 by the ERP
> Information Element sender if*
> 
> *one or more associated NonERP STAs are not short preamble capable as
> indicated in their Capability Information*
> 
> *field, or if the ERP Information Element senders
> dot11ShortPreambleOptionImplemented MIB*
> 
> *variable is set to false*

> static u8 ieee802_11_erp_info(struct hostapd_data *hapd)
> * if (hapd->iface->num_sta_no_short_preamble > 0)
>   erp |= ERP_INFO_BARKER_PREAMBLE_MODE;*

> don't we need to sign barker bit also is th hostapd configure to long
> preamble ?

Well.. Strictly speaking, dot11ShortPreambleOptionImplemented is not a
configurable parameter; it is based on implementation, not runtime
configuration. As long as the local end is capable of receiving short
preamble frame even if only long preamble is allowed in the BSS, forcing
of Barker Preamble Mode in ERP IE does not seem to be required. Anyway,
since we do not have mechanism for learning driver capabilities (though,
I'm assuming all modern hardware supports short preamble), we could as
well follow the runtime configuration for preamble. I added this as
another condition for advertising Barker Preamble Mode in ERP IE.

-- 
Jouni Malinen                                            PGP id EFC895FA