From 5eb4a0fe8d8ee2df98a838eb0f2a7694d81d5783 Mon Sep 17 00:00:00 2001
From: adamdunkels <adamdunkels>
Date: Mon, 11 Oct 2010 23:34:02 +0000
Subject: [PATCH] Rewrote the initial link estimate logic: link estimates are
 now computed only over the actual samples, not over the entire buffer. Also,
 the initial link estimate is much more conservative now (16 transmissions) to
 favor links that have been probed, and which therefore are likely to have
 better ETXs.

---
 core/net/rime/collect-link-estimate.c | 29 ++++++++++++++++-----------
 1 file changed, 17 insertions(+), 12 deletions(-)

diff --git a/core/net/rime/collect-link-estimate.c b/core/net/rime/collect-link-estimate.c
index 4ab16aa17..4616ba839 100644
--- a/core/net/rime/collect-link-estimate.c
+++ b/core/net/rime/collect-link-estimate.c
@@ -32,7 +32,7 @@
  *
  * This file is part of the Contiki operating system.
  *
- * $Id: collect-link-estimate.c,v 1.4 2010/10/03 20:06:25 adamdunkels Exp $
+ * $Id: collect-link-estimate.c,v 1.5 2010/10/11 23:34:02 adamdunkels Exp $
  */
 
 /**
@@ -51,7 +51,7 @@
    collect-link-estimate.h. */
 #define ETX_HISTORY_WINDOW 8
 
-#define INITIAL_LINK_ESTIMATE 4
+#define INITIAL_LINK_ESTIMATE 16
 
 #define DEBUG 0
 #if DEBUG
@@ -77,7 +77,7 @@ collect_link_estimate_new(struct collect_link_estimate *le)
 {
   /* Start with a conservative / pessimistic estimate of link quality
      for new links. */
-  set_all_estimates(le, INITIAL_LINK_ESTIMATE);
+  set_all_estimates(le, 0/*INITIAL_LINK_ESTIMATE*/);
   le->historyptr = 0;
   le->num_estimates = 0;
 }
@@ -86,13 +86,13 @@ void
 collect_link_estimate_update_tx(struct collect_link_estimate *le, uint8_t tx)
 {
   if(tx == 0) {
-    printf("ERROR tx == 0\n");
+    /*    printf("ERROR tx == 0\n");*/
     return;
   }
   if(le != NULL) {
-    if(le->num_estimates == 0) {
-      set_all_estimates(le, tx * 2);
-    } else {
+    /*    if(le->num_estimates == 0) {
+      set_all_estimates(le, tx);
+      } else*/ {
       le->history[le->historyptr] = tx;
       le->historyptr = (le->historyptr + 1) % ETX_HISTORY_WINDOW;
     }
@@ -121,14 +121,19 @@ collect_link_estimate(struct collect_link_estimate *le)
   int i;
   uint16_t etx;
 
+  if(le->num_estimates == 0) {
+    return INITIAL_LINK_ESTIMATE * COLLECT_LINK_ESTIMATE_UNIT;
+  }
+
   PRINTF("collect_link_estimate: ");
   etx = 0;
-  for(i = 0; i < ETX_HISTORY_WINDOW; ++i) {
-    PRINTF("%d ", le->history[i]);
-    etx += le->history[i];
+  for(i = 0; i < le->num_estimates; ++i) {
+    PRINTF("%d+", le->history[i]);
+    etx += le->history[(le->historyptr - i - 1) & (ETX_HISTORY_WINDOW - 1)];
   }
-  PRINTF(", %d\n", (COLLECT_LINK_ESTIMATE_UNIT * etx) / ETX_HISTORY_WINDOW);
-  return (COLLECT_LINK_ESTIMATE_UNIT * etx) / ETX_HISTORY_WINDOW;
+  PRINTF("/%d = %d\n", i,
+         (COLLECT_LINK_ESTIMATE_UNIT * etx) / i);
+  return (COLLECT_LINK_ESTIMATE_UNIT * etx) / i;
 }
 /*---------------------------------------------------------------------------*/
 int