From fa63c306fdebe587ebb082807bf2815ca183fb76 Mon Sep 17 00:00:00 2001
From: Orne Brocaar <info@brocaar.com>
Date: Tue, 15 Apr 2025 10:15:39 +0100
Subject: [PATCH] Add default ADR example in JS.

---
 examples/adr_plugins/default.js | 145 ++++++++++++++++++++++++++++++++
 1 file changed, 145 insertions(+)
 create mode 100644 examples/adr_plugins/default.js

diff --git a/examples/adr_plugins/default.js b/examples/adr_plugins/default.js
new file mode 100644
index 00000000..bba1d7da
--- /dev/null
+++ b/examples/adr_plugins/default.js
@@ -0,0 +1,145 @@
+export function name() {
+  return "JS example for default ADR algorithm";
+}
+
+export function id() {
+  return "js_example_default";
+}
+
+export function handle(req) {
+  let resp = {
+    dr: req.dr,
+    txPowerIndex: req.txPowerIndex,
+    nbTrans: req.nbTrans,
+  };
+
+  if (!req.adr) {
+    return resp;
+  }
+
+  if (req.dr > req.maxDr) {
+    resp.dr = req.maxDr;
+  }
+
+  // Set the new Nb Trans.
+  resp.nbTrans = getNbTrans(req.nbTrans, getPacketLossPercentage(req));
+
+  // Calculate the number of steps.
+  let snrMax = getMaxSnr(req);
+  let snrMargin = snrMax - req.requiredSnrForDr - req.installationMargin;
+  let nStep = Math.floor(snrMargin / 3);
+
+  // In case of negative steps the ADR algorithm will increase the TxPower
+  // if possible. To avoid up / down / up / down TxPower changes, wait until
+  // we have at least the required number of uplink history elements.
+  if (nStep < 0 && getHistoryCount(req) != requiredHistoryCount()) {
+    return resp;
+  }
+
+  let [desiredTxPowerIndex, desiredDr] = getIdealTxPowerIndexAndDr(
+    nStep,
+    resp.txPowerIndex,
+    resp.dr,
+    req.maxTxPowerIndex,
+    req.maxDr,
+  );
+
+  resp.dr = desiredDr;
+  resp.txPowerIndex = desiredTxPowerIndex;
+
+  return resp;
+}
+
+function getIdealTxPowerIndexAndDr(nbStep, txPowerIndex, dr, maxTxPowerIndex, maxDr) {
+  while (nbStep !== 0) {
+    if (nbStep > 0) {
+      if (dr < maxDr) {
+        // Increase the DR.
+        dr++;
+      } else if (txPowerIndex < maxTxPowerIndex) {
+        // Decrease the Tx Power.
+        txPowerIndex++;
+      }
+      nbStep--;
+    } else {
+      // Incease the TxPower.
+      if (txPowerIndex > 0) {
+        txPowerIndex--;
+      }
+      nbStep++;
+    }
+  }
+
+  return [txPowerIndex, dr];
+}
+
+function requiredHistoryCount() {
+  return 20;
+}
+
+function getHistoryCount(req) {
+  let count = 0;
+  for (let uh of req.uplinkHistory) {
+    if (uh.txPowerIndex === req.txPowerIndex) {
+      count++;
+    }
+  }
+
+  return count;
+}
+
+function getMaxSnr(req) {
+  let maxSnr = -999.0;
+
+  for (let uh of req.uplinkHistory) {
+    if (uh.maxSnr > maxSnr) {
+      maxSnr = uh.maxSnr;
+    }
+  }
+
+  return maxSnr;
+}
+
+function getNbTrans(currentNbTrans, pktLossRate) {
+  const pktLossTable = [
+    [1, 1, 2],
+    [1, 2, 3],
+    [2, 3, 3],
+    [3, 3, 3],
+  ];
+
+  if (currentNbTrans < 1) {
+    currentNbTrans = 1;
+  }
+  if (currentNbTrans > 3) {
+    currentNbTrans = 3;
+  }
+
+  const nbTransIndex = currentNbTrans - 1;
+
+  if (pktLossRate < 5.0) {
+    return pktLossTable[0][nbTransIndex];
+  } else if (pktLossRate < 10.0) {
+    return pktLossTable[1][nbTransIndex];
+  } else if (pktLossRate < 30.0) {
+    return pktLossTable[2][nbTransIndex];
+  }
+
+  return pktLossTable[3][nbTransIndex];
+}
+
+function getPacketLossPercentage(req) {
+  if (req.uplinkHistory.length < requiredHistoryCount()) {
+    return 0.0;
+  }
+
+  let lostPackets = 0;
+  let previousFCnt = req.uplinkHistory[0].fCnt;
+
+  for (let uh of req.uplinkHistory.slice(1)) {
+    lostPackets += uh.fCnt - previousFCnt - 1;
+    previousFCnt = uh.fCnt;
+  }
+
+  return lostPackets / req.uplinkHistory.length * 100.0;
+}