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Average wifi ranging results of last 10 seconds #44

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720bafe
Resuse HashMaps in Wifi scanning/ranging code instead of creating them
hlxid Dec 29, 2025
ff4b381
Average wifi ranging results of last 10 seconds
hlxid Dec 29, 2025
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88 changes: 60 additions & 28 deletions CongressRoutePlanner/app/src/main/java/de/c3nav/droid/MainActivity.java
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Original file line number Diff line number Diff line change
Expand Up @@ -29,6 +29,7 @@
import android.os.SystemClock;
import android.preference.PreferenceManager;

import android.util.Pair;
import androidx.annotation.NonNull;
import androidx.annotation.RequiresApi;

Expand Down Expand Up @@ -94,6 +95,7 @@
import java.nio.ByteBuffer;
import java.util.*;
import java.util.stream.Collectors;
import java.util.stream.Stream;

import static android.net.wifi.ScanResult.*;
import static android.net.wifi.rtt.ResponderConfig.RESPONDER_AP;
Expand Down Expand Up @@ -129,7 +131,7 @@ public class MainActivity extends AppCompatActivity
private WifiReceiver wifiReceiver;
private List<SuggestedWifiPeer> suggestedWifiPeers = new ArrayList<>();
private Map<String, ScanResult> lastWifiScanResults = new HashMap<>();
private Map<String, RangingResult> lastWifiRangingResults = new HashMap<>();
private Map<String, List<Pair<Long, RangingResult>>> lastWifiRangingResults = new HashMap<>();

private LinearLayout splashScreen;
private VideoView logoAnimView;
Expand Down Expand Up @@ -938,16 +940,19 @@ protected void startScan() {
wifiManager.startScan();

// Range up to 10 times within interval, result in seconds
int rangeRate = Integer.parseInt(MainActivity.this.sharedPrefs.getString(getString(R.string.wifi_scan_rate_key), "30")) / 10;
int scanRate = Integer.parseInt(MainActivity.this.sharedPrefs.getString(getString(R.string.wifi_scan_rate_key), "30"));
int rangeRate = scanRate / 10;
// Lower limit if scan rate is set low. Scanning more than once per 2s is not really feasible
rangeRate = Math.max(rangeRate, 2);

new Timer().schedule(new TimerTask() {
@Override
public void run() {
MainActivity.this.startWifiRanging();
}
}, 0, rangeRate * 1000L);
for (int delay = 0; delay < scanRate * 1000; delay += rangeRate * 1000) {
new Timer().schedule(new TimerTask() {
@Override
public void run() {
MainActivity.this.startWifiRanging();
}
}, delay);
}
}

protected void setInEditor(boolean inEditor) {
Expand Down Expand Up @@ -1257,12 +1262,11 @@ static class SuggestedWifiPeer {
}

public void processWifiScanResults(List<ScanResult> results) {
Map<String, ScanResult> resultMap = new HashMap<>();
lastWifiScanResults.clear();
for (ScanResult scanRes : results) {
resultMap.put(scanRes.BSSID, scanRes);
lastWifiScanResults.put(scanRes.BSSID, scanRes);
}
this.lastWifiScanResults = resultMap;
Log.d("c3nav", String.format("Nearby total ap count: %d", resultMap.size()));
Log.d("c3nav", String.format("Nearby total ap count: %d", lastWifiScanResults.size()));
pushWifiResultsToApp();
}

Expand Down Expand Up @@ -1314,6 +1318,7 @@ private void startWifiRanging() {

if (rangingPeers.isEmpty()) {
Log.d("rtt", "no aps found for wifi ranging");
isRanging = false;
return;
}
Log.d("rtt", String.format("starting rtt ranging with %d peers", rangingPeers.size()));
Expand Down Expand Up @@ -1369,7 +1374,7 @@ private void performWifiRangingScans(List<ResponderConfig> rangingPeers, List<Ra
@Override
public void onRangingFailure(int code) {
Log.w("rtt", String.format("ranging failure: %d", code));
MainActivity.this.lastWifiRangingResults = new HashMap<>();
MainActivity.this.lastWifiRangingResults.clear();
isRanging = false;
}

Expand Down Expand Up @@ -1401,16 +1406,32 @@ public void onRangingResults(@NonNull List<RangingResult> results) {
private void processWifiRangingResults(List<RangingResult> rangingResults) {
isRanging = false;

Map<String, RangingResult> resultMap = new HashMap<>();
// remove outdated data
final int rangingDateMaxAge = 10000;
for (Map.Entry<String, List<Pair<Long, RangingResult>>> entry : lastWifiRangingResults.entrySet()) {
List<Pair<Long, RangingResult>> withoutOutdated = entry.getValue().stream()
.filter(res -> System.currentTimeMillis() - res.first <= rangingDateMaxAge)
.collect(Collectors.toList());
entry.setValue(withoutOutdated);
}

// add new data
int successfulRanges = 0;
for (RangingResult result : rangingResults) {
MacAddress mac = result.getMacAddress();
if (mac != null && result.getStatus() == RangingResult.STATUS_SUCCESS) {
resultMap.put(mac.toString(), result);
List<Pair<Long, RangingResult>> existingResults = lastWifiRangingResults.get(mac.toString());

if (existingResults == null)
existingResults = new ArrayList<>();
existingResults.add(new Pair<>(System.currentTimeMillis(), result));

lastWifiRangingResults.put(mac.toString(), existingResults);
successfulRanges++;
}
}

Log.d("rtt", String.format("finished wifi ranging. %d/%d ranged successfully", resultMap.size(), rangingResults.size()));
this.lastWifiRangingResults = resultMap;
Log.d("rtt", String.format("finished wifi ranging. %d/%d ranged successfully", successfulRanges, rangingResults.size()));
pushWifiResultsToApp();
}

Expand Down Expand Up @@ -1491,24 +1512,35 @@ private JSONObject serializeWifiScanResult(ScanResult scan) throws JSONException
return jo;
}

private JSONObject serializeWifiRangingResult(RangingResult rttResult) throws JSONException {
private JSONObject serializeWifiRangingResult(List<Pair<Long, RangingResult>> rttResults) throws JSONException {
JSONObject jo = new JSONObject();
if (Build.VERSION.SDK_INT < Build.VERSION_CODES.UPSIDE_DOWN_CAKE)
return jo;
if (rttResults.isEmpty())
return jo;

RangingResult latest = rttResults.get(rttResults.size() - 1).second;

if (latest.getMacAddress() != null)
jo.put("bssid", latest.getMacAddress().toString());
jo.put("frequency", latest.getMeasurementChannelFrequencyMHz());

if (rttResult.getMacAddress() != null)
jo.put("bssid", rttResult.getMacAddress().toString());
jo.put("frequency", rttResult.getMeasurementChannelFrequencyMHz());
double distanceMm = rttResults.stream().mapToInt(res -> res.second.getDistanceMm()).average().orElse(0);
double distanceStdDevMm = rttResults.stream().mapToInt(res -> res.second.getDistanceStdDevMm()).average().orElse(0);
int attemptedMeasurements = rttResults.stream().mapToInt(res -> res.second.getNumAttemptedMeasurements()).sum();
int successfulMeasurements = rttResults.stream().mapToInt(res -> res.second.getNumSuccessfulMeasurements()).sum();

// timestamps are for outdated so we use the newest ones since we know the ap
// was heard in the last ranging averaging interval
JSONObject rtt = new JSONObject();
rtt.put("distance_mm", rttResult.getDistanceMm());
rtt.put("distance_std_dev_mm", rttResult.getDistanceStdDevMm());
rtt.put("num_attempted_measurements", rttResult.getNumAttemptedMeasurements());
rtt.put("num_successful_measurements", rttResult.getNumSuccessfulMeasurements());
rtt.put("ranging_timestamp_millis", rttResult.getRangingTimestampMillis());
rtt.put("measurement_bandwidth", rttResult.getMeasurementBandwidth());
rtt.put("distance_mm", distanceMm);
rtt.put("distance_std_dev_mm", distanceStdDevMm);
rtt.put("num_attempted_measurements", attemptedMeasurements);
rtt.put("num_successful_measurements", successfulMeasurements);
rtt.put("ranging_timestamp_millis", latest.getRangingTimestampMillis());
rtt.put("measurement_bandwidth", latest.getMeasurementBandwidth());
jo.put("rtt", rtt);
jo.put("last", SystemClock.elapsedRealtime() - rttResult.getRangingTimestampMillis());
jo.put("last", SystemClock.elapsedRealtime() - latest.getRangingTimestampMillis());
return jo;
}

Expand Down