[PATCH] Re: throughput and tx rate in marginal signal conditions

[Joe Parks]

Marty had trouble getting the list to accept this, so now I'll try:

-Joe

----

Here's a patch that allows you to set the number of consective dropped
packets before lowering the transmit rate.  This patch defaults to 2 (per
Jean Tourrilhes' suggestion on June 3), but you can change that easily
enough via WLAN_RATE_DECREASE_THRESHOLD.  My colleagues and I are still
testing it, but so far so good.

- Marty


Martin Lamb
ROI Computer Services, Inc.

------------------------------------------------------------


--- driver/modules/hostap_ap.h	2003-05-22 00:09:20.000000000 -0400
+++ driver/modules/hostap_ap.h.rajant	2003-06-05 11:10:43.000000000 -0400
@@ -39,6 +39,9 @@
 /* Try to increase TX rate after # successfully sent packets */
 #define WLAN_RATE_UPDATE_COUNT 50
 
+/* Decrease TX rate after # consecutive dropped packets */
+#define WLAN_RATE_DECREASE_THRESHOLD 2
+
 struct sta_info {
 	struct list_head list;
 	struct sta_info *hnext; /* next entry in hash table list */
@@ -76,6 +79,7 @@
 					*/
 	u32 tx_since_last_failure;
 	u32 txexc;
+        u32 tx_consecutive_exc;
 
 	struct prism2_crypt_data *crypt;
 
--- driver/modules/hostap_ap.c	2003-05-28 23:59:42.000000000 -0400
+++ driver/modules/hostap_ap.c.rajant	2003-06-05 11:15:55.000000000 -0400
@@ -2730,6 +2730,7 @@
 
 	sta->tx_count[sta->tx_rate_idx]++;
 	sta->tx_since_last_failure++;
+        sta->tx_consecutive_exc = 0;
 	if (sta->tx_since_last_failure > WLAN_RATE_UPDATE_COUNT &&
 	    sta->tx_rate_idx < sta->tx_max_rate) {
 		/* use next higher rate */
@@ -2904,7 +2905,12 @@
 
 	sta->txexc++;
 	sta->tx_since_last_failure = 0;
-	if (sta->tx_rate_idx > 0 && txdesc->tx_rate <= sta->tx_rate) {
+        sta->tx_consecutive_exc++;
+        
+	if (sta->tx_consecutive_exc > WLAN_RATE_DECREASE_THRESHOLD 
+        	&& sta->tx_rate_idx > 0 
+                && txdesc->tx_rate <= sta->tx_rate) {
+                
 		/* use next lower rate */
 		int old, rate;
 		old = rate = sta->tx_rate_idx;
@@ -2927,6 +2933,7 @@
 			       "to %d\n", local->dev->name, MAC2STR(sta->addr),
 			       sta->tx_rate);
 		}
+                sta->tx_consecutive_exc = 0;
 	}
 	spin_unlock(&local->ap->sta_table_lock);
 }