add an optional max_rssi attribute to the ieee80211com structure and

allow to export the RSSI Max value with ioctls and by radiotap
headers.

ok damien@ jsg@

description:

we currently use "dB" as an indication for the signal strength in
ifconfig and in the radiotap headers. it means "decibel difference
from an arbitrary, fixed reference". this is quite confusing, because
different chipsets have different references for the dB/rssi values.

we can use the plain RSSI which is described in IEEE 802.11: "The
receive signal strength indicator (RSSI) is an optional parameter that
has a value of 0 through RSSI Max.". all wireless chipsets have
something like a RSSI (normally as a Rx descriptor field), but the
value for RSSI Max is chipset-specific.

if we know the RSSI Max, we can calculate a percentage which is much
easier to understand for the user. we even don't have to use the
absolute RSSI Max, we can use an average RSSI Max, figured out by
monitoring and tuning the RSSI Max of the drivers. if the user gets a
signal of 110%, it would mean "better than the average Max signal".

there's no need to do any RSSI calculations in the kernel, it just
passes the the relative rssi and max_rssi values to userspace. this is
done in the ieee80211_nodereq ioctl structure and possible with a new
radiotap header. the radiotap RSSI header allows to get a flexible but
common signal indicator instead of the complex and unrelated dB/dBm
signal fields. it must include two 8bit values current rssi and RSSI
max.

1 files changed, 6 insertions, 1 deletions

diff --git a/sys/net80211/ieee80211_radiotap.h b/sys/net80211/ieee80211_radiotap.h
index 8c48121be05..938f74b8dad 100644
--- a/sys/net80211/ieee80211_radiotap.h
+++ b/sys/net80211/ieee80211_radiotap.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: ieee80211_radiotap.h,v 1.7 2005/07/30 17:13:17 reyk Exp $ */
+/* $OpenBSD: ieee80211_radiotap.h,v 1.8 2006/06/23 21:34:15 reyk Exp $ */
 /* $FreeBSD: src/sys/net80211/ieee80211_radiotap.h,v 1.3 2004/04/05 22:13:21 sam Exp $ */
 /* $NetBSD: ieee80211_radiotap.h,v 1.9 2004/06/06 04:13:28 dyoung Exp $ */
 
@@ -162,6 +162,10 @@ struct ieee80211_radiotap_header {
  * IEEE80211_RADIOTAP_HWQUEUE           u_int8_t       data
  *
  *	A specific hardware queue (used by WME)
+ *
+ * IEEE80211_RADIOTAP_RSSI              2x u_int8_t    RSSI, max RSSI
+ *
+ *	A relative Received Signal Strength Index
  */
 enum ieee80211_radiotap_type {
 	IEEE80211_RADIOTAP_TSFT = 0,
@@ -180,6 +184,7 @@ enum ieee80211_radiotap_type {
 	IEEE80211_RADIOTAP_DB_ANTNOISE = 13,
 	IEEE80211_RADIOTAP_FCS = 14,
 	IEEE80211_RADIOTAP_HWQUEUE = 15,
+	IEEE80211_RADIOTAP_RSSI = 16,
 	IEEE80211_RADIOTAP_EXT = 31
 };