Project : madwifi
Revision : 2775
Author : benoit
Date : 2007-10-19 23:43:47 +0200 (Fri, 19 Oct 2007)
Log Message :
Better algorithm to select a new channel. Close to the required Uniform
Spreading.
Affected Files:
* madwifi/branches/madwifi-dfs/net80211/ieee80211_scan.c updated
Modified: madwifi/branches/madwifi-dfs/net80211/ieee80211_scan.c
===================================================================
--- madwifi/branches/madwifi-dfs/net80211/ieee80211_scan.c 2007-10-19
21:23:02 UTC (rev 2774)
+++ madwifi/branches/madwifi-dfs/net80211/ieee80211_scan.c 2007-10-19
21:43:47 UTC (rev 2775)
@@ -979,20 +979,19 @@
__func__);
}
} else {
- /* No channel wa found via scan module, means no good scanlist
+ /* No channel was found via scan module, means no good scanlist
* was found */
- int chanStart, i, n;
+ int chanStart, i, count;
u_int32_t curChanFlags;
- /* Pick a random channel */
- chanStart = jiffies % ic->ic_nchans;
- curChanFlags = (ic->ic_curchan->ic_flags) &
~(IEEE80211_CHAN_RADAR);
+ if ((ic->ic_curchan != NULL) &&
+ (ic->ic_curchan != IEEE80211_CHAN_ANYC)) {
+ IEEE80211_DPRINTF(vap, IEEE80211_MSG_DOTH,
+ "%s: ic_curchan is %d/%d Mhz\n",
+ __func__, ic->ic_curchan->ic_ieee,
+ ic->ic_curchan->ic_freq);
+ }
- IEEE80211_DPRINTF(vap, IEEE80211_MSG_DOTH,
- "%s: ic_curchan is %d/%d Mhz\n",
- __func__, ic->ic_curchan->ic_ieee,
- ic->ic_curchan->ic_freq);
-
if ((ic->ic_bsschan != NULL) &&
(ic->ic_bsschan != IEEE80211_CHAN_ANYC)) {
IEEE80211_DPRINTF(vap, IEEE80211_MSG_DOTH,
@@ -1001,21 +1000,48 @@
ic->ic_bsschan->ic_freq);
}
+ /* According to FCC/ETSI rules on uniform spreading, we shall
+ * select a channel out of the list of usable channels so that
+ * the probability of selecting a given channel shall be the
+ * same for all channels (reference: ETSI 301 893 v1.3.1
+ * $4.6.2.5.1 */
+
+ /* First, we count the usable channels */
+
+ count = 0;
+ curChanFlags = (ic->ic_bsschan->ic_flags) &
~(IEEE80211_CHAN_RADAR);
for (i=0; i<ic->ic_nchans; i++) {
- n = (i + chanStart) % ic->ic_nchans;
- IEEE80211_DPRINTF(vap, IEEE80211_MSG_DOTH,
- "%s: testing new channel %d/%d Mhz\n",
- __func__, ic->ic_channels[n].ic_ieee,
- ic->ic_channels[n].ic_freq);
- if (ic->ic_channels[n].ic_flags == curChanFlags) {
- new_channel = &ic->ic_channels[n];
- break;
+ if ((ic->ic_channels[i].ic_ieee !=
ic->ic_bsschan->ic_ieee) &&
+ (ic->ic_channels[i].ic_flags == curChanFlags)) {
+ IEEE80211_DPRINTF(vap, IEEE80211_MSG_DOTH,
+ "%s: usable channel %d/%d
Mhz\n",
+ __func__,
ic->ic_channels[i].ic_ieee,
+ ic->ic_channels[i].ic_freq);
+ count ++;
}
}
+
+ if (count != 0) {
+
+ /* Next, we pickup a random usable channel */
+ chanStart = jiffies % count;
+
+ count = 0;
+ for (i=0; i<ic->ic_nchans; i++) {
+ if ((ic->ic_channels[i].ic_ieee !=
ic->ic_bsschan->ic_ieee) &&
+ (ic->ic_channels[i].ic_flags ==
curChanFlags)) {
+ if (count++ == chanStart) {
+ new_channel =
&ic->ic_channels[i];
+ break;
+ }
+ }
+ }
+ }
+
if (new_channel != NULL) {
IEEE80211_DPRINTF(vap, IEEE80211_MSG_DOTH,
- "%s: new random channel found\n",
- __func__);
+ "%s: new random channel found %d/%d
Mhz\n",
+ __func__, new_channel->ic_ieee,
new_channel->ic_freq);
}
}
if(!new_channel) {
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