States aggregation (#82)

* initial

Signed-off-by: zhiqiand <zhiqian@fb.com>

* fix some comments

Signed-off-by: zhiqiand <zhiqian@fb.com>

* fix comments on AggregatedState and ModelerUtils

Signed-off-by: zhiqiand <zhiqian@fb.com>

* reformat and thread-safe

Signed-off-by: zhiqiand <zhiqian@fb.com>

* add buffer size for state

Signed-off-by: zhiqiand <zhiqian@fb.com>

* fix some comments

Signed-off-by: zhiqiand <zhiqian@fb.com>

* add javadoc

Signed-off-by: zhiqiand <zhiqian@fb.com>

* fix comments in TestUtils

Signed-off-by: zhiqiand <zhiqian@fb.com>

* fix some comments

Signed-off-by: zhiqiand <zhiqian@fb.com>

* fix some comments

Signed-off-by: zhiqiand <zhiqian@fb.com>

* fix some comments

Signed-off-by: zhiqiand <zhiqian@fb.com>

* fix tx_power

Signed-off-by: zhiqiand <zhiqian@fb.com>

* fix channel number

Signed-off-by: zhiqiand <zhiqian@fb.com>

* fix long type

Signed-off-by: zhiqiand <zhiqian@fb.com>

Signed-off-by: zhiqiand <zhiqian@fb.com>

src/main/java/com/facebook/openwifirrm/RRMConfig.java

@@ -309,6 +309,12 @@ public class RRMConfig {
 			 * ({@code MODELERPARAMS_WIFISCANBUFFERSIZE})
 			 */
 			public int wifiScanBufferSize = 10;
+
+			/**
+			 * Maximum rounds of States to store per device
+			 * ({@code MODELERPARAMS_STATEBUFFERSIZE})
+			 */
+			public int stateBufferSize = 10;
 		}
 
 		/** Modeler parameters. */
@@ -532,6 +538,9 @@ public class RRMConfig {
 		if ((v = env.get("MODELERPARAMS_WIFISCANBUFFERSIZE")) != null) {
 			modelerParams.wifiScanBufferSize = Integer.parseInt(v);
 		}
+		if ((v = env.get("MODELERPARAMS_STATEBUFFERSIZE")) != null) {
+			modelerParams.stateBufferSize = Integer.parseInt(v);
+		}
 		ModuleConfig.ApiServerParams apiServerParams =
 			config.moduleConfig.apiServerParams;
 		if ((v = env.get("APISERVERPARAMS_HTTPPORT")) != null) {

src/main/java/com/facebook/openwifirrm/modules/Modeler.java

@@ -8,6 +8,7 @@
 
 package com.facebook.openwifirrm.modules;
 
+import java.util.Collections;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
@@ -93,8 +94,9 @@ public class Modeler implements Runnable {
 		public Map<String, List<List<WifiScanEntry>>> latestWifiScans =
 			new ConcurrentHashMap<>();
 
-		/** List of latest state per device. */
-		public Map<String, State> latestState = new ConcurrentHashMap<>();
+		/** List of latest states per device. */
+		public Map<String, List<State>> latestStates =
+			new ConcurrentHashMap<>();
 
 		/** List of radio info per device. */
 		public Map<String, JsonArray> latestDeviceStatusRadios =
@@ -267,7 +269,10 @@ public class Modeler implements Runnable {
 			if (state != null) {
 				try {
 					State stateModel = gson.fromJson(state, State.class);
-					dataModel.latestState.put(device.serialNumber, stateModel);
+					dataModel.latestStates.computeIfAbsent(
+						device.serialNumber,
+						k -> Collections.synchronizedList(new LinkedList<>())
+					).add(stateModel);
 					logger.debug(
 						"Device {}: added initial state from uCentralGw",
 						device.serialNumber
@@ -299,8 +304,18 @@ public class Modeler implements Runnable {
 				if (state != null) {
 					try {
 						State stateModel = gson.fromJson(state, State.class);
-						dataModel.latestState
-							.put(record.serialNumber, stateModel);
+						List<State> latestStatesList = dataModel.latestStates
+							.computeIfAbsent(
+								record.serialNumber,
+								k -> Collections
+									.synchronizedList(new LinkedList<>())
+							);
+						if (latestStatesList.size() >= params.stateBufferSize) {
+							latestStatesList.remove(0);
+						}
+						latestStatesList.add(stateModel);
+						dataModel.latestStates
+							.put(record.serialNumber, latestStatesList);
 						stateUpdates.add(record.serialNumber);
 					} catch (JsonSyntaxException e) {
 						logger.error(
@@ -423,7 +438,7 @@ public class Modeler implements Runnable {
 			logger.debug("Removed some wifi scan entries from data model");
 		}
 		if (
-			dataModel.latestState.entrySet()
+			dataModel.latestStates.entrySet()
 				.removeIf(e -> !isRRMEnabled(e.getKey()))
 		) {
 			logger.debug("Removed some state entries from data model");

src/main/java/com/facebook/openwifirrm/modules/ModelerUtils.java

@@ -13,6 +13,7 @@ import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
+import java.util.concurrent.ConcurrentHashMap;
 import java.util.stream.Collectors;
 
 import org.slf4j.Logger;
@@ -24,6 +25,11 @@ import com.facebook.openwifirrm.modules.Modeler.DataModel;
 import com.facebook.openwifirrm.ucentral.WifiScanEntry;
 import com.facebook.openwifirrm.ucentral.informationelement.HTOperation;
 import com.facebook.openwifirrm.ucentral.informationelement.VHTOperation;
+import com.facebook.openwifirrm.ucentral.models.AggregatedState;
+import com.facebook.openwifirrm.ucentral.models.State;
+import com.facebook.openwifirrm.ucentral.models.State.Interface;
+import com.facebook.openwifirrm.ucentral.models.State.Interface.SSID;
+import com.facebook.openwifirrm.ucentral.models.State.Interface.SSID.Association;
 
 /**
  * Modeler utilities.
@@ -381,4 +387,173 @@ public class ModelerUtils {
 		}
 		return aggregatedWifiScans;
 	}
+
+	/**
+	 * This method converts the input State info to an AggregatedState
+	 * and adds it to the bssidToAggregatedStates map. If the bssid&station
+	 * of the input State does not exist in the map, create a new
+	 * AggregatedState list. If the bssid&station of the input State exists,
+	 * then convert State to AggregatedState and check if there exits an
+	 * AggregatedState of the same radio. If there does, append the value
+	 * of aggregation field to the existing AggregatedState, if not, create
+	 * a new AggregatedState and add it to the list.
+	 *
+	 * @param bssidToAggregatedStates map from bssid&station to a list of AggregatedState.
+	 * @param state the state that is to be added.
+	 */
+	static void addStateToAggregation(
+		Map<String, List<AggregatedState>> bssidToAggregatedStates,
+		State state
+	) {
+		for (Interface stateInterface : state.interfaces) {
+			if (stateInterface.ssids == null) {
+				continue;
+			}
+			for (SSID ssid : stateInterface.ssids) {
+				Map<String, Integer> radioInfo = new HashMap<>();
+				radioInfo.put("channel", ssid.radio.get("channel").getAsInt());
+				radioInfo.put(
+					"channel_width",
+					ssid.radio.get("channel_width").getAsInt()
+				);
+				radioInfo
+					.put("tx_power", ssid.radio.get("tx_power").getAsInt());
+
+				for (Association association : ssid.associations) {
+					if (association == null) {
+						continue;
+					}
+					String key = getBssidStationKeyPair(
+						association.bssid,
+						association.station
+					);
+					List<AggregatedState> aggregatedStates =
+						bssidToAggregatedStates
+							.computeIfAbsent(key, k -> new ArrayList<>());
+					AggregatedState aggState =
+						new AggregatedState(association, radioInfo);
+
+					/**
+					 * Indicate if the aggState can be merged into some old AggregatedState.
+					 * If true, it will be merged by appending its mcs/rssi field to the old one.
+					 * If false, it will be added to the list aggregatedStates.
+					*/
+					boolean canBeMergedToOldAggregatedState = false;
+					for (
+						AggregatedState oldAggregatedState : aggregatedStates
+					) {
+						if (oldAggregatedState.add(aggState)) {
+							canBeMergedToOldAggregatedState = true;
+							break;
+						}
+					}
+					if (!canBeMergedToOldAggregatedState) {
+						aggregatedStates.add(aggState);
+					}
+					bssidToAggregatedStates.put(key, aggregatedStates);
+				}
+			}
+		}
+	}
+
+	/**
+	 * This method aggregates States by bssid&station key pair and radio info.
+	 * if two States of the same bssid&station match in channel, channel width and tx_power
+	 * need to be aggregated to one {@code AggregatedState}. Currently only mcs and
+	 * rssi fields are being aggregated. They are of List<Integer> type in AggregatedState,
+	 * which list all the values over the time.
+	 *
+	 * @param dataModel the data model which includes the latest recorded States.
+	 * @param obsoletionPeriodMs the maximum amount of time (in milliseconds) it
+	 *                           is worth aggregating over, starting from the
+	 *                           most recent States and working backwards in time.
+	 * 							 A State exactly {@code obsoletionPeriodMs} ms earlier
+	 * 							 than the most recent State is considered non-obsolete
+	 *                           (i.e., the "non-obsolete" window is inclusive).
+	 *                           Must be non-negative.
+	 * @param refTimeMs	the reference time were passed to make testing easier
+	 * @return  Map<String, Map<String, List<AggregatedState>>> A map from serial number to
+	 * 							a map from bssid_station String pair to a list of AggregatedState.
+	 */
+	public static Map<String, Map<String, List<AggregatedState>>> getAggregatedStates(
+		Modeler.DataModel dataModel,
+		long obsoletionPeriodMs,
+		long refTimeMs
+	) {
+		if (obsoletionPeriodMs < 0) {
+			throw new IllegalArgumentException(
+				"obsoletionPeriodMs must be non-negative."
+			);
+		}
+		Map<String, Map<String, List<AggregatedState>>> aggregatedStates =
+			new HashMap<>();
+
+		for (
+			Map.Entry<String, List<State>> deviceToStateList : dataModel.latestStates
+				.entrySet()
+		) {
+			String serialNumber = deviceToStateList.getKey();
+			List<State> states = deviceToStateList.getValue();
+
+			if (states.isEmpty()) {
+				continue;
+			}
+
+			/**
+			 * Sort in reverse chronological order. Sorting is done just in case the
+			 * States in the original list are not chronological already - although
+			 * they are inserted chronologically, perhaps latency, synchronization, etc.
+			 */
+			states.sort(
+				(state1, state2) -> -Long.compare(state1.unit.localtime, state2.unit.localtime)
+			);
+
+			Map<String, List<AggregatedState>> bssidToAggregatedStates =
+				aggregatedStates
+					.computeIfAbsent(serialNumber, k -> new HashMap<>());
+
+			for (State state : states) {
+				if (refTimeMs - state.unit.localtime > obsoletionPeriodMs) {
+					// discard obsolete entries
+					break;
+				}
+
+				addStateToAggregation(bssidToAggregatedStates, state);
+			}
+		}
+		return aggregatedStates;
+	}
+
+	/**
+	 * This method gets the most recent State from latestStates per device.
+	 *
+	 * @param latestStates list of latest States per device.
+	 * @return Map<String, State> a map from device String to latest State.
+	 */
+	public static Map<String, State> getLatestState(
+		Map<String, List<State>> latestStates
+	) {
+		Map<String, State> latestState = new ConcurrentHashMap<>();
+		for (
+			Map.Entry<String, List<State>> stateEntry : latestStates.entrySet()
+		) {
+			String key = stateEntry.getKey();
+			List<State> value = stateEntry.getValue();
+			if (value.isEmpty()) {
+				latestState.put(key, null);
+			} else {
+				latestState.put(key, value.get(value.size() - 1));
+			}
+		}
+		return latestState;
+	}
+
+	/**  Create a key pair consisted of bssid and station string */
+	public static String getBssidStationKeyPair(String bssid, String station) {
+		return String.format(
+			"bssid: %s, station: %s",
+			bssid,
+			station
+		);
+	}
 }

src/main/java/com/facebook/openwifirrm/optimizers/channel/ChannelOptimizer.java

@@ -154,7 +154,7 @@ public abstract class ChannelOptimizer {
 		// Remove model entries not in the given zone
 		this.model.latestWifiScans.keySet()
 			.removeIf(serialNumber -> !deviceConfigs.containsKey(serialNumber));
-		this.model.latestState.keySet()
+		this.model.latestStates.keySet()
 			.removeIf(serialNumber -> !deviceConfigs.containsKey(serialNumber));
 		this.model.latestDeviceStatusRadios.keySet()
 			.removeIf(serialNumber -> !deviceConfigs.containsKey(serialNumber));

src/main/java/com/facebook/openwifirrm/optimizers/channel/LeastUsedChannelOptimizer.java

@@ -21,6 +21,7 @@ import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import com.facebook.openwifirrm.DeviceDataManager;
+import com.facebook.openwifirrm.modules.ModelerUtils;
 import com.facebook.openwifirrm.modules.Modeler.DataModel;
 import com.facebook.openwifirrm.ucentral.UCentralConstants;
 import com.facebook.openwifirrm.ucentral.UCentralUtils;
@@ -340,8 +341,10 @@ public class LeastUsedChannelOptimizer extends ChannelOptimizer {
 				AVAILABLE_CHANNELS_BAND
 			);
 
+		Map<String, State> latestState =
+			ModelerUtils.getLatestState(model.latestStates);
 		Map<String, String> bssidsMap =
-			UCentralUtils.getBssidsMap(model.latestState);
+			UCentralUtils.getBssidsMap(latestState);
 
 		for (String band : bandsMap.keySet()) {
 			// Performance metrics
@@ -373,7 +376,7 @@ public class LeastUsedChannelOptimizer extends ChannelOptimizer {
 				}
 
 				// Get current channel of the device
-				State state = model.latestState.get(serialNumber);
+				State state = latestState.get(serialNumber);
 				if (state == null) {
 					logger.debug(
 						"Device {}: No state found, skipping...",

src/main/java/com/facebook/openwifirrm/optimizers/channel/RandomChannelInitializer.java

@@ -20,6 +20,7 @@ import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import com.facebook.openwifirrm.DeviceDataManager;
+import com.facebook.openwifirrm.modules.ModelerUtils;
 import com.facebook.openwifirrm.modules.Modeler.DataModel;
 import com.facebook.openwifirrm.ucentral.UCentralUtils;
 import com.facebook.openwifirrm.ucentral.WifiScanEntry;
@@ -128,8 +129,10 @@ public class RandomChannelInitializer extends ChannelOptimizer {
 				AVAILABLE_CHANNELS_BAND
 			);
 
+		Map<String, State> latestState =
+			ModelerUtils.getLatestState(model.latestStates);
 		Map<String, String> bssidsMap =
-			UCentralUtils.getBssidsMap(model.latestState);
+			UCentralUtils.getBssidsMap(latestState);
 
 		for (Map.Entry<String, List<String>> entry : bandsMap.entrySet()) {
 			// Performance metrics
@@ -183,7 +186,7 @@ public class RandomChannelInitializer extends ChannelOptimizer {
 						? rng.nextInt(availableChannelsList.size()) : defaultChannelIndex
 				);
 
-				State state = model.latestState.get(serialNumber);
+				State state = latestState.get(serialNumber);
 				if (state == null) {
 					logger.debug(
 						"Device {}: No state found, skipping...",

src/main/java/com/facebook/openwifirrm/optimizers/tpc/LocationBasedOptimalTPC.java

@@ -175,7 +175,8 @@ public class LocationBasedOptimalTPC extends TPC {
 		// Filter out the invalid APs (e.g., no radio, no location data)
 		// Update txPowerChoices, boundary, apLocX, apLocY for the optimization
 		for (String serialNumber : serialNumbers) {
-			State state = model.latestState.get(serialNumber);
+			List<State> states = model.latestStates.get(serialNumber);
+			State state = states.get(states.size() - 1);
 
 			// Ignore the device if its radio is not active
 			if (state.radios == null || state.radios.length == 0) {

src/main/java/com/facebook/openwifirrm/optimizers/tpc/MeasurementBasedApApTPC.java

@@ -154,8 +154,9 @@ public class MeasurementBasedApApTPC extends TPC {
 	 */
 	protected static Set<String> getManagedBSSIDs(DataModel model) {
 		Set<String> managedBSSIDs = new HashSet<>();
-		for (Map.Entry<String, State> e : model.latestState.entrySet()) {
-			State state = e.getValue();
+		for (Map.Entry<String, List<State>> e : model.latestStates.entrySet()) {
+			List<State> states = e.getValue();
+			State state = states.get(states.size() - 1);
 			if (state.interfaces == null) {
 				continue;
 			}
@@ -311,7 +312,8 @@ public class MeasurementBasedApApTPC extends TPC {
 			buildRssiMap(managedBSSIDs, model.latestWifiScans, band);
 		logger.debug("Starting TPC for the {} band", band);
 		for (String serialNumber : serialNumbers) {
-			State state = model.latestState.get(serialNumber);
+			List<State> states = model.latestStates.get(serialNumber);
+			State state = states.get(states.size() - 1);
 			if (
 				state == null || state.radios == null ||
 					state.radios.length == 0

src/main/java/com/facebook/openwifirrm/optimizers/tpc/MeasurementBasedApClientTPC.java

@@ -291,10 +291,10 @@ public class MeasurementBasedApClientTPC extends TPC {
 	public Map<String, Map<String, Integer>> computeTxPowerMap() {
 		Map<String, Map<String, Integer>> txPowerMap = new TreeMap<>();
 
-		for (Map.Entry<String, State> e : model.latestState.entrySet()) {
+		for (Map.Entry<String, List<State>> e : model.latestStates.entrySet()) {
 			String serialNumber = e.getKey();
-			State state = e.getValue();
-
+			List<State> states = e.getValue();
+			State state = states.get(states.size() - 1);
 			if (state.radios == null || state.radios.length == 0) {
 				logger.debug(
 					"Device {}: No radios found, skipping...",

src/main/java/com/facebook/openwifirrm/optimizers/tpc/RandomTxPowerInitializer.java

@@ -122,7 +122,7 @@ public class RandomTxPowerInitializer extends TPC {
 		if (!setDifferentTxPowerPerAp) {
 			List<Integer> txPowerChoices =
 				new ArrayList<>(DEFAULT_TX_POWER_CHOICES);
-			for (String serialNumber : model.latestState.keySet()) {
+			for (String serialNumber : model.latestStates.keySet()) {
 				for (String band : UCentralConstants.BANDS) {
 					txPowerChoices = updateTxPowerChoices(
 						band,

src/main/java/com/facebook/openwifirrm/optimizers/tpc/TPC.java

@@ -70,7 +70,7 @@ public abstract class TPC {
 		this.model.latestWifiScans.keySet()
 			.removeIf(serialNumber -> !deviceConfigs.containsKey(serialNumber)
 			);
-		this.model.latestState.keySet()
+		this.model.latestStates.keySet()
 			.removeIf(serialNumber -> !deviceConfigs.containsKey(serialNumber)
 			);
 		this.model.latestDeviceStatusRadios.keySet()
@@ -184,9 +184,10 @@ public abstract class TPC {
 	 */
 	protected Map<Integer, List<String>> getApsPerChannel() {
 		Map<Integer, List<String>> apsPerChannel = new TreeMap<>();
-		for (Map.Entry<String, State> e : model.latestState.entrySet()) {
+		for (Map.Entry<String, List<State>> e : model.latestStates.entrySet()) {
 			String serialNumber = e.getKey();
-			State state = e.getValue();
+			List<State> states = e.getValue();
+			State state = states.get(states.size() - 1);
 
 			if (state.radios == null || state.radios.length == 0) {
 				logger.debug(

src/main/java/com/facebook/openwifirrm/ucentral/models/AggregatedState.java

@@ -0,0 +1,221 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+package com.facebook.openwifirrm.ucentral.models;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+
+import com.facebook.openwifirrm.ucentral.models.State.Interface.SSID.Association;
+import com.facebook.openwifirrm.ucentral.models.State.Interface.SSID.Association.Rate;
+
+/**
+ * Aggregation model for State aggregation. Only contains info useful for
+ * analysis.
+ */
+public class AggregatedState {
+
+	/** Rate information with aggregated fields. */
+	public static class AggregatedRate {
+		/**
+		 * This is the common bitRate for all the aggregated fields.
+		 */
+		public long bitRate;
+
+		/**
+		 * This is the common channel width for all the aggregated fields.
+		 */
+		public int chWidth;
+
+		/**
+		 * Aggregated fields mcs
+		 */
+		public List<Integer> mcs = new ArrayList<>();
+
+		/** Constructor with no args */
+		private AggregatedRate() {}
+
+		/** Add a Rate to the AggregatedRate */
+		private void add(Rate rate) {
+			if (rate == null) {
+				return;
+			}
+			if (mcs.isEmpty()) {
+				bitRate = rate.bitrate;
+				chWidth = rate.chwidth;
+			}
+			mcs.add(rate.mcs);
+		}
+
+		/**
+		 * Add an AggregatedRate with the same channel_width to the
+		 * AggregatedRate
+		 */
+		private void add(AggregatedRate rate) {
+			if (rate == null || rate.chWidth != chWidth) {
+				return;
+			}
+			if (mcs.isEmpty()) {
+				bitRate = rate.bitRate;
+				chWidth = rate.chWidth;
+			}
+			mcs.addAll(rate.mcs);
+		}
+	}
+
+	/**
+	 * Radio information with channel, channel_width and tx_power.
+	 */
+	public static class Radio {
+		public int channel;
+		public int channelWidth;
+		public int txPower;
+
+		private Radio() {}
+
+		public Radio(int channel, int channelWidth, int txPower) {
+			this.channel = channel;
+			this.channelWidth = channelWidth;
+			this.txPower = txPower;
+		}
+
+		private Radio(Map<String, Integer> radioInfo) {
+			channel = radioInfo.getOrDefault("channel", -1);
+			channelWidth = radioInfo.getOrDefault("channel_width", -1);
+			txPower = radioInfo.getOrDefault("tx_power", -1);
+		}
+
+		@Override
+		public int hashCode() {
+			return Objects.hash(channel, channelWidth, txPower);
+		}
+
+		@Override
+		public boolean equals(Object obj) {
+			if (this == obj) {
+				return true;
+			}
+			if (obj == null) {
+				return false;
+			}
+			if (getClass() != obj.getClass()) {
+				return false;
+			}
+
+			Radio other = (Radio) obj;
+			return channel == other.channel &&
+				channelWidth == other.channelWidth && txPower == other.txPower;
+		}
+	}
+
+	public String bssid;
+	public String station;
+	public long connected;
+	public long inactive;
+	public List<Integer> rssi;
+	public long rxBytes;
+	public long rxPackets;
+	public AggregatedRate rxRate;
+	public long txBytes;
+	public long txDuration;
+	public long txFailed;
+	public long txPackets;
+	public AggregatedRate txRate;
+	public long txRetries;
+	public int ackSignal;
+	public int ackSignalAvg;
+	public Radio radio;
+
+	/** Constructor with no args */
+	public AggregatedState() {
+		this.rxRate = new AggregatedRate();
+		this.txRate = new AggregatedRate();
+		this.rssi = new ArrayList<>();
+		this.radio = new Radio();
+	}
+
+	/** Construct from Association and radio */
+	public AggregatedState(
+		Association association,
+		Map<String, Integer> radioInfo
+	) {
+		this.rxRate = new AggregatedRate();
+		this.txRate = new AggregatedRate();
+		this.rssi = new ArrayList<>();
+
+		this.bssid = association.bssid;
+		this.station = association.station;
+		this.connected = association.connected;
+		this.inactive = association.inactive;
+		this.rssi.add(association.rssi);
+		this.rxBytes = association.rx_bytes;
+		this.rxPackets = association.rx_packets;
+		this.rxRate.add(association.rx_rate);
+		this.txBytes = association.tx_bytes;
+		this.txDuration = association.tx_duration;
+		this.txFailed = association.tx_failed;
+		this.txPackets = association.tx_packets;
+		this.txRate.add(association.tx_rate);
+		this.txRetries = association.tx_retries;
+		this.ackSignal = association.ack_signal;
+		this.ackSignalAvg = association.ack_signal_avg;
+		this.radio = new Radio(radioInfo);
+	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hash(bssid, station, radio);
+	}
+
+	@Override
+	public boolean equals(Object obj) {
+		if (this == obj) {
+			return true;
+		}
+		if (obj == null) {
+			return false;
+		}
+		if (getClass() != obj.getClass()) {
+			return false;
+		}
+
+		AggregatedState other = (AggregatedState) obj;
+
+		return bssid == other.bssid && station == other.station &&
+			connected == other.connected && inactive == other.inactive && rssi
+				.equals(other.rssi) &&
+			rxBytes == other.rxBytes && rxBytes == other.rxPackets &&
+			Objects.equals(rxRate, other.rxRate) &&
+			txBytes == other.txBytes && txDuration == other.txDuration &&
+			txFailed == other.txFailed && txPackets == other.txPackets &&
+			Objects.equals(txRate, other.txRate) &&
+			txRetries == other.txRetries && ackSignal == other.ackSignal &&
+			ackSignalAvg == other.ackSignalAvg &&
+			Objects.equals(radio, other.radio);
+	}
+
+	/**
+	 * Add an AggregatedState to this AggregatedState. Succeed only when the two
+	 * matches in hashCode.
+	 *
+	 * @param state input AggregatedState
+	 * @return boolean true if the two matches in bssid, station, channel,
+	 *         channel_width and tx_power
+	 */
+	public boolean add(AggregatedState state) {
+		if (hashCode() == state.hashCode()) {
+			this.rssi.addAll(state.rssi);
+			this.rxRate.add(state.rxRate);
+			this.txRate.add(state.txRate);
+			return true;
+		}
+		return false;
+	}
+}

src/test/java/com/facebook/openwifirrm/modules/ModelerUtilsTest.java

@@ -15,7 +15,9 @@ import static org.junit.jupiter.api.Assertions.assertTrue;
 
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.HashMap;
 import java.util.LinkedList;
+import java.util.List;
 import java.util.Map;
 
 import org.junit.jupiter.api.Test;
@@ -24,6 +26,8 @@ import com.facebook.openwifirrm.aggregators.MeanAggregator;
 import com.facebook.openwifirrm.modules.Modeler.DataModel;
 import com.facebook.openwifirrm.optimizers.TestUtils;
 import com.facebook.openwifirrm.ucentral.WifiScanEntry;
+import com.facebook.openwifirrm.ucentral.models.AggregatedState;
+import com.facebook.openwifirrm.ucentral.models.State;
 
 public class ModelerUtilsTest {
 	@Test
@@ -32,9 +36,9 @@ public class ModelerUtilsTest {
 		double[][][] rxPower = ModelerUtils.generateRxPower(
 			500,
 			4,
-			new ArrayList<>(Arrays.asList(408.0, 507.0, 64.0, 457.0)),
-			new ArrayList<>(Arrays.asList(317.0, 49.0, 140.0, 274.0)),
-			new ArrayList<>(Arrays.asList(20.0, 20.0, 20.0, 20.0))
+			Arrays.asList(408.0, 507.0, 64.0, 457.0),
+			Arrays.asList(317.0, 49.0, 140.0, 274.0),
+			Arrays.asList(20.0, 20.0, 20.0, 20.0)
 		);
 		assertNull(rxPower);
 	}
@@ -44,9 +48,9 @@ public class ModelerUtilsTest {
 		double[][][] rxPower = ModelerUtils.generateRxPower(
 			500,
 			4,
-			new ArrayList<>(Arrays.asList(408.0, 453.0, 64.0, 457.0)),
-			new ArrayList<>(Arrays.asList(317.0, 49.0, 140.0, 274.0)),
-			new ArrayList<>(Arrays.asList(20.0, 20.0, 20.0, 20.0))
+			Arrays.asList(408.0, 453.0, 64.0, 457.0),
+			Arrays.asList(317.0, 49.0, 140.0, 274.0),
+			Arrays.asList(20.0, 20.0, 20.0, 20.0)
 		);
 		assertEquals(-108.529, rxPower[0][0][0], 0.001);
 		double[][] heatMap = ModelerUtils.generateHeatMap(
@@ -74,9 +78,9 @@ public class ModelerUtilsTest {
 		double[][][] rxPower = ModelerUtils.generateRxPower(
 			500,
 			4,
-			new ArrayList<>(Arrays.asList(408.0, 453.0, 64.0, 457.0)),
-			new ArrayList<>(Arrays.asList(317.0, 49.0, 140.0, 274.0)),
-			new ArrayList<>(Arrays.asList(30.0, 30.0, 30.0, 30.0))
+			Arrays.asList(408.0, 453.0, 64.0, 457.0),
+			Arrays.asList(317.0, 49.0, 140.0, 274.0),
+			Arrays.asList(30.0, 30.0, 30.0, 30.0)
 		);
 		assertEquals(-98.529, rxPower[0][0][0], 0.001);
 		double[][] heatMap = ModelerUtils.generateHeatMap(
@@ -547,4 +551,295 @@ public class ModelerUtilsTest {
 			aggregateMap.get(apB).get(bssidA)
 		);
 	}
+
+	@Test
+	void testAddStateToAggregation() {
+		final String bssidA = "aa:aa:aa:aa:aa:a";
+		final String stationA1 = "stationA1";
+		final String stationA2 = "stationA2";
+		final String bssidB = "bb:bb:bb:bb:bb:bb";
+		final String stationB = "stationB";
+		final String stationC = "stationC";
+		final String bssidC = "cc:cc:cc:cc:cc:cc";
+
+		AggregatedState aggStateA1 = TestUtils.createAggregatedState(
+			1,
+			20,
+			10,
+			bssidA,
+			stationA1,
+			new int[] { 10, 20, 30 }
+		);
+		AggregatedState aggStateA2 = TestUtils.createAggregatedState(
+			6,
+			20,
+			10,
+			bssidA,
+			stationA2,
+			new int[] { 20, 30, 40 }
+		);
+		AggregatedState aggStateB = TestUtils.createAggregatedState(
+			11,
+			20,
+			20,
+			bssidB,
+			stationB,
+			new int[] { 10, 20, 30 }
+		);
+		AggregatedState aggStateC = TestUtils.createAggregatedState(
+			1,
+			20,
+			10,
+			bssidC,
+			stationC,
+			new int[] { 100, 200, 300 }
+		);
+
+		Map<String, List<AggregatedState>> bssidToAggregatedStates =
+			new HashMap<>();
+		bssidToAggregatedStates.put(
+			ModelerUtils.getBssidStationKeyPair(bssidA, stationA1),
+			new ArrayList<>(Arrays.asList(aggStateA1))
+		);
+
+		bssidToAggregatedStates.put(
+			ModelerUtils.getBssidStationKeyPair(bssidA, stationA2),
+			new ArrayList<>(Arrays.asList(aggStateA2))
+		);
+		bssidToAggregatedStates.put(
+			ModelerUtils.getBssidStationKeyPair(bssidB, stationB),
+			new ArrayList<>(Arrays.asList(aggStateB))
+		);
+		bssidToAggregatedStates.put(
+			ModelerUtils.getBssidStationKeyPair(bssidC, stationC),
+			new ArrayList<>(Arrays.asList(aggStateC))
+		);
+
+		State toBeAggregated1 = TestUtils.createState(
+			6,
+			20,
+			10,
+			bssidA,
+			new String[] { stationA1, stationA1, stationA2 },
+			new int[] { 40, 50, 60 },
+			1
+		);
+
+		ModelerUtils
+			.addStateToAggregation(bssidToAggregatedStates, toBeAggregated1);
+
+		assertEquals(
+			bssidToAggregatedStates
+				.get(ModelerUtils.getBssidStationKeyPair(bssidA, stationA1))
+				.get(0).rssi,
+			Arrays.asList(10, 20, 30)
+		);
+
+		assertEquals(
+			bssidToAggregatedStates
+				.get(ModelerUtils.getBssidStationKeyPair(bssidA, stationA1))
+				.get(1).rssi,
+			Arrays.asList(40, 50)
+		);
+		assertEquals(
+			bssidToAggregatedStates
+				.get(ModelerUtils.getBssidStationKeyPair(bssidA, stationA2))
+				.get(0).rssi,
+			Arrays.asList(20, 30, 40, 60)
+		);
+
+		State toBeAggregated2 = TestUtils.createState(
+			11,
+			20,
+			20,
+			bssidB,
+			new String[] { stationB },
+			new int[] { 40 },
+			1
+		);
+		ModelerUtils
+			.addStateToAggregation(bssidToAggregatedStates, toBeAggregated2);
+		assertEquals(
+			bssidToAggregatedStates
+				.get(ModelerUtils.getBssidStationKeyPair(bssidB, stationB))
+				.get(0).rssi,
+			Arrays.asList(10, 20, 30, 40)
+		);
+	}
+
+	@Test
+	void testGetAggregatedStates() {
+		final long obsoletionPeriodMs = 60000000;
+		final String serialNumberA = "aaaaaaaaaaaa";
+		final String bssidA = "aa:aa:aa:aa:aa:a";
+		final String serialNumberB = "bbbbbbbbbbbb";
+		final String bssidB = "bb:bb:bb:bb:bb:bb";
+		final String serialNumberC = "cccccccccccc";
+		final String bssidC = "cc:cc:cc:cc:cc:cc";
+		final String stationA1 = "stationA1";
+		final String stationA2 = "stationA2";
+		final String stationA3 = "stationA3";
+		final String stationA4 = "stationA4";
+		final String stationB = "stationB";
+		final String stationC = "stationC";
+
+		final long refTimeMs = TestUtils.DEFAULT_LOCAL_TIME;
+
+		DataModel dataModel = new DataModel();
+
+		// This serie of StateA is used to test a valid input states.
+		State time1StateA = TestUtils.createState(
+			1,
+			80,
+			10,
+			bssidA,
+			new String[] { stationA1, stationA2, stationA2, stationA3 },
+			new int[] { -84, -67, -67, 10 },
+			6,
+			40,
+			20,
+			bssidA,
+			new String[] { stationA1 },
+			new int[] { -80 },
+			TestUtils.DEFAULT_LOCAL_TIME
+		);
+
+		State time2StateA = TestUtils.createState(
+			1,
+			80,
+			10,
+			bssidA,
+			new String[] { stationA1, stationA3 },
+			new int[] { 27, 100 },
+			6,
+			40,
+			20,
+			bssidA,
+			new String[] { stationA2, stationA2 },
+			new int[] { 180, 67 },
+			TestUtils.DEFAULT_LOCAL_TIME - 800
+		);
+
+		//As State time3StateA is obsolete, it should not be aggregated.
+		State time3StateA = TestUtils.createState(
+			1,
+			80,
+			10,
+			bssidA,
+			new String[] { stationA1, stationA2, stationA4 },
+			new int[] { 24, 27, 1000 },
+			6,
+			40,
+			20,
+			bssidA,
+			new String[] { stationA1, stationA2 },
+			new int[] { 180, 180 },
+			// Set the localtime exactly obsolete
+			TestUtils.DEFAULT_LOCAL_TIME - obsoletionPeriodMs - 1
+		);
+
+		dataModel.latestStates.put(
+			serialNumberA,
+			new ArrayList<>(
+				Arrays.asList(
+					time1StateA,
+					time2StateA,
+					time3StateA
+				)
+			)
+		);
+
+		Map<String, Map<String, List<AggregatedState>>> aggregatedMap =
+			ModelerUtils
+				.getAggregatedStates(dataModel, obsoletionPeriodMs, refTimeMs);
+
+		assertEquals(
+			aggregatedMap.get(serialNumberA).get(ModelerUtils.getBssidStationKeyPair(bssidA, stationA1)).size(),
+			2
+		);
+		assertEquals(
+			aggregatedMap.get(serialNumberA).get(ModelerUtils.getBssidStationKeyPair(bssidA, stationA1)).get(0).radio,
+			new AggregatedState.Radio(1, 80, 10)
+		);
+		assertEquals(
+			aggregatedMap.get(serialNumberA).get(ModelerUtils.getBssidStationKeyPair(bssidA, stationA1)).get(0).rssi,
+			Arrays.asList(-84, 27)
+		);
+		assertEquals(
+			aggregatedMap.get(serialNumberA).get(ModelerUtils.getBssidStationKeyPair(bssidA, stationA1)).get(1).radio,
+			new AggregatedState.Radio(6, 40, 20)
+		);
+		assertEquals(
+			aggregatedMap.get(serialNumberA).get(ModelerUtils.getBssidStationKeyPair(bssidA, stationA1)).get(1).rssi,
+			Arrays.asList(-80)
+		);
+		assertEquals(
+			aggregatedMap.get(serialNumberA).get(ModelerUtils.getBssidStationKeyPair(bssidA, stationA2)).get(0).radio,
+			new AggregatedState.Radio(1, 80, 10)
+		);
+		assertEquals(
+			aggregatedMap.get(serialNumberA).get(ModelerUtils.getBssidStationKeyPair(bssidA, stationA2)).get(0).rssi,
+			Arrays.asList(-67, -67)
+		);
+		assertEquals(
+			aggregatedMap.get(serialNumberA).get(ModelerUtils.getBssidStationKeyPair(bssidA, stationA2)).get(1).radio,
+			new AggregatedState.Radio(6, 40, 20)
+		);
+		assertEquals(
+			aggregatedMap.get(serialNumberA).get(ModelerUtils.getBssidStationKeyPair(bssidA, stationA2)).get(1).rssi,
+			Arrays.asList(180, 67)
+		);
+		assertEquals(
+			aggregatedMap.get(serialNumberA).get(ModelerUtils.getBssidStationKeyPair(bssidA, stationA3)).get(0).radio,
+			new AggregatedState.Radio(1, 80, 10)
+		);
+		assertEquals(
+			aggregatedMap.get(serialNumberA).get(ModelerUtils.getBssidStationKeyPair(bssidA, stationA3)).get(0).rssi,
+			Arrays.asList(10, 100)
+		);
+
+		// Test more clients operate on the same channel (stationB and stationA)
+		State time1StateB = TestUtils.createState(
+			1,
+			80,
+			10,
+			bssidB,
+			new String[] { stationB },
+			new int[] { -30 },
+			TestUtils.DEFAULT_LOCAL_TIME
+		);
+		dataModel.latestStates
+			.computeIfAbsent(serialNumberB, k -> new ArrayList<>())
+			.add(time1StateB);
+
+		State time1StateC = TestUtils.createState(
+			6,
+			40,
+			20,
+			bssidC,
+			new String[] { stationC },
+			new int[] { -100 },
+			TestUtils.DEFAULT_LOCAL_TIME
+		);
+		dataModel.latestStates
+			.computeIfAbsent(serialNumberC, k -> new ArrayList<>())
+			.add(time1StateC);
+
+		Map<String, Map<String, List<AggregatedState>>> aggregatedMap2 =
+			ModelerUtils
+				.getAggregatedStates(dataModel, obsoletionPeriodMs, refTimeMs);
+
+		assertEquals(
+			aggregatedMap2.get(serialNumberB).get(ModelerUtils.getBssidStationKeyPair(bssidB, stationB)).get(0).rssi, Arrays.asList(-30)
+		);
+
+		assertEquals(
+			aggregatedMap2.get(serialNumberC).get(ModelerUtils.getBssidStationKeyPair(bssidC, stationC)).get(0).rssi, Arrays.asList(-100)
+		);
+
+		assertEquals(
+			aggregatedMap2.get(serialNumberA).get(ModelerUtils.getBssidStationKeyPair(bssidA, stationA1)).size(),
+			aggregatedMap.get(serialNumberA).get(ModelerUtils.getBssidStationKeyPair(bssidA, stationA1)).size()
+		);
+	}
 }

src/test/java/com/facebook/openwifirrm/optimizers/TestUtils.java

@@ -21,6 +21,7 @@ import com.facebook.openwifirrm.DeviceTopology;
 import com.facebook.openwifirrm.ucentral.UCentralConstants;
 import com.facebook.openwifirrm.ucentral.UCentralUtils;
 import com.facebook.openwifirrm.ucentral.WifiScanEntry;
+import com.facebook.openwifirrm.ucentral.models.AggregatedState;
 import com.facebook.openwifirrm.ucentral.models.State;
 import com.google.gson.Gson;
 import com.google.gson.JsonArray;
@@ -39,6 +40,12 @@ public class TestUtils {
 	/** Default tx power in dBm */
 	public static final int DEFAULT_TX_POWER = 20;
 
+	/**
+	 *  Default local time in unix timestamps in seconds
+	 * 	GMT: Fri Sep 24 2021 23:47:55 GMT+0000
+	 */
+	public static final long DEFAULT_LOCAL_TIME = 1632527275;
+
 	/** Create a topology from the given devices in a single zone. */
 	public static DeviceTopology createTopology(
 		String zone,
@@ -428,26 +435,28 @@ public class TestUtils {
 		return radio;
 	}
 
-	/** Create a {@code State.Unit}. */
-	private static State.Unit createStateUnit() {
+	/** Create a {@code State.Unit} with specifying localtime in unix timestamp in seconds. */
+	private static State.Unit createStateUnit(long localtime) {
 		// @formatter:off
+		String jsonStr = String.format(
+		"  {\n" +
+		"    \"load\": [\n" +
+		"      0,\n" +
+		"      0,\n" +
+		"      0\n" +
+		"    ],\n" +
+		"    \"localtime\": %d,\n" +
+		"    \"memory\": {\n" +
+		"      \"free\": 788930560,\n" +
+		"      \"total\": 973561856\n" +
+		"    },\n" +
+		"    \"uptime\": 684456\n" +
+		"  }\n", localtime);
+		// @formatter:on
 		return gson.fromJson(
-			"  {\n" +
-			"    \"load\": [\n" +
-			"      0,\n" +
-			"      0,\n" +
-			"      0\n" +
-			"    ],\n" +
-			"    \"localtime\": 1632527275,\n" +
-			"    \"memory\": {\n" +
-			"      \"free\": 788930560,\n" +
-			"      \"total\": 973561856\n" +
-			"    },\n" +
-			"    \"uptime\": 684456\n" +
-			"  }\n",
+			jsonStr,
 			State.Unit.class
 		);
-		// @formatter:on
 	}
 
 	/**
@@ -463,7 +472,9 @@ public class TestUtils {
 	 * @param channelWidths array of channel widths (MHz)
 	 * @param txPowers array of tx powers (dBm)
 	 * @param bssids array of BSSIDs
+	 * @param stations 2-D array of client station codes
 	 * @param clientRssis 2-D array of client RSSIs
+	 * @param localtime unix timestamp in seconds.
 	 * @return the state of an AP with radios described by the given parameters
 	 */
 	public static State createState(
@@ -471,15 +482,19 @@ public class TestUtils {
 		int[] channelWidths,
 		int[] txPowers,
 		String[] bssids,
-		int[][] clientRssis
+		String[][] stations,
+		int[][] clientRssis,
+		long localtime
 	) {
 		if (
 			!(channels.length == channelWidths.length &&
 				channelWidths.length == txPowers.length &&
-				txPowers.length == bssids.length)
+				txPowers.length == bssids.length &&
+				bssids.length == stations.length &&
+				stations.length == clientRssis.length)
 		) {
 			throw new IllegalArgumentException(
-				"All arguments must have the same length."
+				"All array-type arguments must have the same length."
 			);
 		}
 		final int numRadios = channels.length;
@@ -503,12 +518,49 @@ public class TestUtils {
 					new State.Interface.SSID.Association();
 				state.interfaces[i].ssids[0].associations[j].rssi =
 					clientRssis[i][j];
+				state.interfaces[i].ssids[0].associations[j].station =
+					stations[i][j];
+				state.interfaces[i].ssids[0].associations[j].bssid = bssids[i];
+				state.interfaces[i].ssids[0].radio = gson
+					.fromJson(gson.toJson(state.radios[i]), JsonObject.class);
 			}
 		}
-		state.unit = createStateUnit();
+		state.unit = createStateUnit(localtime);
 		return state;
 	}
 
+	/**
+	 * Create a device state object with one radio.
+	 *
+	 * @param channel channel number
+	 * @param channelWidth channel width in MHz
+	 * @param txPower tx power in dBm
+	 * @param bssid bssid
+	 * @param stations array of station codes
+	 * @param clientRssis array of client RSSIs
+	 * @param localtime unix timestamp in seconds.
+	 * @return the state of an AP with one radio
+	 */
+	public static State createState(
+		int channel,
+		int channelWidth,
+		int txPower,
+		String bssid,
+		String[] stations,
+		int[] clientRssis,
+		long localtime
+	) {
+		return createState(
+			new int[] { channel },
+			new int[] { channelWidth },
+			new int[] { txPower },
+			new String[] { bssid },
+			new String[][] { stations },
+			new int[][] { clientRssis },
+			localtime
+		);
+	}
+
 	/**
 	 * Create a device state object with one radio.
 	 *
@@ -571,7 +623,9 @@ public class TestUtils {
 			new int[] { channelWidth },
 			new int[] { txPower },
 			new String[] { bssid },
-			new int[][] { clientRssis }
+			new String[][] { new String[clientRssis.length] },
+			new int[][] { clientRssis },
+			DEFAULT_LOCAL_TIME
 		);
 	}
 
@@ -599,52 +653,84 @@ public class TestUtils {
 		String bssidB
 	) {
 		return createState(
-			channelA,
-			channelWidthA,
-			txPowerA,
-			bssidA,
-			new int[] {},
-			channelB,
-			channelWidthB,
-			txPowerB,
-			bssidB,
-			new int[] {}
+			new int[] { channelA, channelB },
+			new int[] { channelWidthA, channelWidthB },
+			new int[] { txPowerA, txPowerB },
+			new String[] { bssidA, bssidB },
+			new String[][] { new String[] {}, new String[] {} },
+			new int[][] { new int[] {}, new int[] {} },
+			DEFAULT_LOCAL_TIME
 		);
 	}
 
 	/**
-	 * Create a device state object with two radios.
-	 *
-	 * @param channelA channel number
-	 * @param channelWidthA channel width (MHz) of channelA
-	 * @param txPowerA tx power for channelA
-	 * @param bssidA bssid for radio on channelA
-	 * @param clientRssisA array of client RSSIs for channelA
-	 * @param channelB channel number
-	 * @param channelWidthB channel width (MHz) of channelB
-	 * @param txPowerB tx power for channelB
-	 * @param bssidB bssid for radio on channelB
-	 * @param clientRssisB array of client RSSIs for channelB
-	 * @return the state of an AP with two radios
-	 */
+	* Create a device state object with two radios.
+	*
+	* @param channelA channel number
+	* @param channelWidthA channel width (MHz) of channelA
+	* @param txPowerA tx power (dB) for channelA
+	* @param bssidA bssid for radio on channelA
+	* @param clientRssisA array of client RSSIs for channelA
+	* @param channelB channel number
+	* @param channelWidthB channel width (MHz) of channelB
+	* @param txPowerB tx power (dB) for channelB
+	* @param bssidB bssid for radio on channelB
+	* @param clientRssisB array of client RSSIs for channelB
+	* @param localtime local time for the State
+	* @return the state of an AP with two radios
+	*/
 	public static State createState(
 		int channelA,
 		int channelWidthA,
 		int txPowerA,
 		String bssidA,
+		String[] stationsA,
 		int[] clientRssisA,
 		int channelB,
 		int channelWidthB,
 		int txPowerB,
 		String bssidB,
-		int[] clientRssisB
+		String[] stationsB,
+		int[] clientRssisB,
+		long localtime
 	) {
 		return createState(
 			new int[] { channelA, channelB },
 			new int[] { channelWidthA, channelWidthB },
 			new int[] { txPowerA, txPowerB },
 			new String[] { bssidA, bssidB },
-			new int[][] { clientRssisA, clientRssisB }
+			new String[][] { stationsA, stationsB },
+			new int[][] { clientRssisA, clientRssisB },
+			localtime
 		);
 	}
+
+	/**
+	 * Create an AggregatedState from given radio info.
+	 *
+	 * @param channel channel number
+	 * @param channelWidth channel width (MHz) of channelA
+	 * @param txPower tx power (db) for this channel
+	 * @param bssid bssid for radio on this channel
+	 * @param station station string for radio on this channel
+	 * @param clientRssi array of client RSSIs.
+	 * @return AggregatedState creating from the given radio.
+	 */
+	public static AggregatedState createAggregatedState(
+		int channel,
+		int channelWidth,
+		int txPower,
+		String bssid,
+		String station,
+		int[] clientRssi
+	) {
+		AggregatedState state = new AggregatedState();
+		state.radio = new AggregatedState.Radio(channel, channelWidth, txPower);
+		state.bssid = bssid;
+		state.station = station;
+		for (int rssi : clientRssi) {
+			state.rssi.add(rssi);
+		}
+		return state;
+	}
 }

src/test/java/com/facebook/openwifirrm/optimizers/channel/LeastUsedChannelOptimizerTest.java

@@ -55,9 +55,12 @@ public class LeastUsedChannelOptimizerTest {
 			deviceA,
 			TestUtils.createDeviceStatus(band, aExpectedChannel)
 		);
-		dataModel.latestState.put(
+		dataModel.latestStates.put(
 			deviceA,
-			TestUtils.createState(aExpectedChannel, channelWidth, dummyBssid)
+			Arrays.asList(
+				TestUtils
+					.createState(aExpectedChannel, channelWidth, dummyBssid)
+			)
 		);
 		dataModel.latestWifiScans.put(
 			deviceA,
@@ -77,9 +80,9 @@ public class LeastUsedChannelOptimizerTest {
 			deviceB,
 			TestUtils.createDeviceStatus(band, 40)
 		);
-		dataModel.latestState.put(
+		dataModel.latestStates.put(
 			deviceB,
-			TestUtils.createState(40, channelWidth, dummyBssid)
+			Arrays.asList(TestUtils.createState(40, channelWidth, dummyBssid))
 		);
 		dataModel.latestWifiScans.put(
 			deviceB,
@@ -98,9 +101,11 @@ public class LeastUsedChannelOptimizerTest {
 			deviceC,
 			TestUtils.createDeviceStatus(band, 149)
 		);
-		dataModel.latestState.put(
+		dataModel.latestStates.put(
 			deviceC,
-			TestUtils.createState(149, channelWidth, dummyBssid)
+			Arrays.asList(
+				TestUtils.createState(149, channelWidth, dummyBssid)
+			)
 		);
 		dataModel.latestWifiScans.put(
 			deviceC,
@@ -142,9 +147,12 @@ public class LeastUsedChannelOptimizerTest {
 			deviceA,
 			TestUtils.createDeviceStatus(band, aExpectedChannel)
 		);
-		dataModel.latestState.put(
+		dataModel.latestStates.put(
 			deviceA,
-			TestUtils.createState(aExpectedChannel, channelWidth, dummyBssid)
+			Arrays.asList(
+				TestUtils
+					.createState(aExpectedChannel, channelWidth, dummyBssid)
+			)
 		);
 		dataModel.latestWifiScans.put(
 			deviceA,
@@ -164,9 +172,9 @@ public class LeastUsedChannelOptimizerTest {
 			deviceB,
 			TestUtils.createDeviceStatus(band, 6)
 		);
-		dataModel.latestState.put(
+		dataModel.latestStates.put(
 			deviceB,
-			TestUtils.createState(6, channelWidth, dummyBssid)
+			Arrays.asList(TestUtils.createState(6, channelWidth, dummyBssid))
 		);
 		dataModel.latestWifiScans.put(
 			deviceB,
@@ -182,9 +190,9 @@ public class LeastUsedChannelOptimizerTest {
 			deviceC,
 			TestUtils.createDeviceStatus(band, 6)
 		);
-		dataModel.latestState.put(
+		dataModel.latestStates.put(
 			deviceC,
-			TestUtils.createState(6, channelWidth, dummyBssid)
+			Arrays.asList(TestUtils.createState(6, channelWidth, dummyBssid))
 		);
 		dataModel.latestWifiScans.put(
 			deviceC,
@@ -235,9 +243,12 @@ public class LeastUsedChannelOptimizerTest {
 			deviceA,
 			TestUtils.createDeviceStatus(band, aExpectedChannel)
 		);
-		dataModel.latestState.put(
+		dataModel.latestStates.put(
 			deviceA,
-			TestUtils.createState(aExpectedChannel, channelWidth, dummyBssid)
+			Arrays.asList(
+				TestUtils
+					.createState(aExpectedChannel, channelWidth, dummyBssid)
+			)
 		);
 		dataModel.latestWifiScans.put(
 			deviceA,
@@ -256,9 +267,9 @@ public class LeastUsedChannelOptimizerTest {
 			deviceB,
 			TestUtils.createDeviceStatus(band, 40)
 		);
-		dataModel.latestState.put(
+		dataModel.latestStates.put(
 			deviceB,
-			TestUtils.createState(40, channelWidth, dummyBssid)
+			Arrays.asList(TestUtils.createState(40, channelWidth, dummyBssid))
 		);
 		dataModel.latestWifiScans.put(
 			deviceB,
@@ -276,9 +287,11 @@ public class LeastUsedChannelOptimizerTest {
 			deviceC,
 			TestUtils.createDeviceStatus(band, 149)
 		);
-		dataModel.latestState.put(
+		dataModel.latestStates.put(
 			deviceC,
-			TestUtils.createState(149, channelWidth, dummyBssid)
+			Arrays.asList(
+				TestUtils.createState(149, channelWidth, dummyBssid)
+			)
 		);
 		dataModel.latestWifiScans.put(
 			deviceC,
@@ -328,9 +341,12 @@ public class LeastUsedChannelOptimizerTest {
 			deviceA,
 			TestUtils.createDeviceStatus(band, aExpectedChannel)
 		);
-		dataModel.latestState.put(
+		dataModel.latestStates.put(
 			deviceA,
-			TestUtils.createState(aExpectedChannel, channelWidth, dummyBssid)
+			Arrays.asList(
+				TestUtils
+					.createState(aExpectedChannel, channelWidth, dummyBssid)
+			)
 		);
 		dataModel.latestWifiScans.put(
 			deviceA,
@@ -351,9 +367,9 @@ public class LeastUsedChannelOptimizerTest {
 			deviceB,
 			TestUtils.createDeviceStatus(band, 40)
 		);
-		dataModel.latestState.put(
+		dataModel.latestStates.put(
 			deviceB,
-			TestUtils.createState(40, channelWidth, dummyBssid)
+			Arrays.asList(TestUtils.createState(40, channelWidth, dummyBssid))
 		);
 		dataModel.latestWifiScans.put(
 			deviceB,
@@ -372,9 +388,11 @@ public class LeastUsedChannelOptimizerTest {
 			deviceC,
 			TestUtils.createDeviceStatus(band, 149)
 		);
-		dataModel.latestState.put(
+		dataModel.latestStates.put(
 			deviceC,
-			TestUtils.createState(149, channelWidth, dummyBssid)
+			Arrays.asList(
+				TestUtils.createState(149, channelWidth, dummyBssid)
+			)
 		);
 		dataModel.latestWifiScans.put(
 			deviceC,
@@ -418,9 +436,12 @@ public class LeastUsedChannelOptimizerTest {
 			deviceA,
 			TestUtils.createDeviceStatus(band, aExpectedChannel)
 		);
-		dataModel.latestState.put(
+		dataModel.latestStates.put(
 			deviceA,
-			TestUtils.createState(aExpectedChannel, channelWidth, dummyBssid)
+			Arrays.asList(
+				TestUtils
+					.createState(aExpectedChannel, channelWidth, dummyBssid)
+			)
 		);
 		dataModel.latestWifiScans.put(
 			deviceA,
@@ -442,9 +463,9 @@ public class LeastUsedChannelOptimizerTest {
 			deviceB,
 			TestUtils.createDeviceStatus(band, 40)
 		);
-		dataModel.latestState.put(
+		dataModel.latestStates.put(
 			deviceB,
-			TestUtils.createState(40, channelWidth, dummyBssid)
+			Arrays.asList(TestUtils.createState(40, channelWidth, dummyBssid))
 		);
 		dataModel.latestWifiScans.put(
 			deviceB,
@@ -463,9 +484,11 @@ public class LeastUsedChannelOptimizerTest {
 			deviceC,
 			TestUtils.createDeviceStatus(band, 149)
 		);
-		dataModel.latestState.put(
+		dataModel.latestStates.put(
 			deviceC,
-			TestUtils.createState(149, channelWidth, dummyBssid)
+			Arrays.asList(
+				TestUtils.createState(149, channelWidth, dummyBssid)
+			)
 		);
 		dataModel.latestWifiScans.put(
 			deviceC,
@@ -483,9 +506,9 @@ public class LeastUsedChannelOptimizerTest {
 			deviceD,
 			TestUtils.createDeviceStatus(band, 40)
 		);
-		dataModel.latestState.put(
+		dataModel.latestStates.put(
 			deviceD,
-			TestUtils.createState(40, channelWidth, dummyBssid)
+			Arrays.asList(TestUtils.createState(40, channelWidth, dummyBssid))
 		);
 		dataModel.latestWifiScans.put(
 			deviceD,
@@ -536,9 +559,12 @@ public class LeastUsedChannelOptimizerTest {
 			deviceA,
 			TestUtils.createDeviceStatus(band, aExpectedChannel)
 		);
-		dataModel.latestState.put(
+		dataModel.latestStates.put(
 			deviceA,
-			TestUtils.createState(aExpectedChannel, channelWidth, dummyBssid)
+			Arrays.asList(
+				TestUtils
+					.createState(aExpectedChannel, channelWidth, dummyBssid)
+			)
 		);
 		dataModel.latestWifiScans.put(
 			deviceA,
@@ -558,9 +584,9 @@ public class LeastUsedChannelOptimizerTest {
 			deviceB,
 			TestUtils.createDeviceStatus(band, 36)
 		);
-		dataModel.latestState.put(
+		dataModel.latestStates.put(
 			deviceB,
-			TestUtils.createState(36, channelWidth, dummyBssid)
+			Arrays.asList(TestUtils.createState(36, channelWidth, dummyBssid))
 		);
 		dataModel.latestWifiScans.put(
 			deviceB,
@@ -579,9 +605,11 @@ public class LeastUsedChannelOptimizerTest {
 			deviceC,
 			TestUtils.createDeviceStatus(band, 149)
 		);
-		dataModel.latestState.put(
+		dataModel.latestStates.put(
 			deviceC,
-			TestUtils.createState(149, channelWidth, dummyBssid)
+			Arrays.asList(
+				TestUtils.createState(149, channelWidth, dummyBssid)
+			)
 		);
 		dataModel.latestWifiScans.put(
 			deviceC,
@@ -601,9 +629,9 @@ public class LeastUsedChannelOptimizerTest {
 			deviceD,
 			TestUtils.createDeviceStatus(band, 36)
 		);
-		dataModel.latestState.put(
+		dataModel.latestStates.put(
 			deviceD,
-			TestUtils.createState(36, channelWidth, dummyBssid)
+			Arrays.asList(TestUtils.createState(36, channelWidth, dummyBssid))
 		);
 		dataModel.latestWifiScans.put(
 			deviceD,
@@ -626,9 +654,12 @@ public class LeastUsedChannelOptimizerTest {
 			deviceE,
 			TestUtils.createDeviceStatus(band, eExpectedChannel)
 		);
-		dataModel.latestState.put(
+		dataModel.latestStates.put(
 			deviceE,
-			TestUtils.createState(eExpectedChannel, channelWidth, dummyBssid)
+			Arrays.asList(
+				TestUtils
+					.createState(aExpectedChannel, channelWidth, dummyBssid)
+			)
 		);
 		dataModel.latestWifiScans.put(
 			deviceE,
@@ -672,9 +703,12 @@ public class LeastUsedChannelOptimizerTest {
 			deviceA,
 			TestUtils.createDeviceStatus(band, aExpectedChannel)
 		);
-		dataModel.latestState.put(
+		dataModel.latestStates.put(
 			deviceA,
-			TestUtils.createState(aExpectedChannel, channelWidth, dummyBssid)
+			Arrays.asList(
+				TestUtils
+					.createState(aExpectedChannel, channelWidth, dummyBssid)
+			)
 		);
 		dataModel.latestWifiScans.put(
 			deviceA,
@@ -693,9 +727,9 @@ public class LeastUsedChannelOptimizerTest {
 			deviceB,
 			TestUtils.createDeviceStatus(band, 48)
 		);
-		dataModel.latestState.put(
+		dataModel.latestStates.put(
 			deviceB,
-			TestUtils.createState(48, channelWidth, dummyBssid)
+			Arrays.asList(TestUtils.createState(48, channelWidth, dummyBssid))
 		);
 		dataModel.latestWifiScans.put(
 			deviceB,
@@ -725,9 +759,11 @@ public class LeastUsedChannelOptimizerTest {
 			deviceC,
 			TestUtils.createDeviceStatus(band, 149)
 		);
-		dataModel.latestState.put(
+		dataModel.latestStates.put(
 			deviceC,
-			TestUtils.createState(149, channelWidth, dummyBssid)
+			Arrays.asList(
+				TestUtils.createState(149, channelWidth, dummyBssid)
+			)
 		);
 		dataModel.latestWifiScans.put(
 			deviceC,

src/test/java/com/facebook/openwifirrm/optimizers/channel/RandomChannelInitializerTest.java

@@ -11,6 +11,7 @@ package com.facebook.openwifirrm.optimizers.channel;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertNotEquals;
 
+import java.util.Arrays;
 import java.util.Map;
 import java.util.Random;
 
@@ -46,13 +47,17 @@ public class RandomChannelInitializerTest {
 
 		// A and B will be assigned to the same channel
 		DataModel dataModel = new DataModel();
-		dataModel.latestState.put(
+		dataModel.latestStates.put(
 			deviceA,
-			TestUtils.createState(6, channelWidth, deviceABssid)
+			Arrays.asList(
+				TestUtils.createState(6, channelWidth, deviceABssid)
+			)
 		);
-		dataModel.latestState.put(
+		dataModel.latestStates.put(
 			deviceB,
-			TestUtils.createState(11, channelWidth, deviceBBssid)
+			Arrays.asList(
+				TestUtils.createState(11, channelWidth, deviceBBssid)
+			)
 		);
 		dataModel.latestDeviceStatusRadios.put(
 			deviceA,
@@ -91,13 +96,17 @@ public class RandomChannelInitializerTest {
 
 		// A and B will be assigned to the same channel
 		DataModel dataModel = new DataModel();
-		dataModel.latestState.put(
+		dataModel.latestStates.put(
 			deviceA,
-			TestUtils.createState(6, channelWidth, deviceABssid)
+			Arrays.asList(
+				TestUtils.createState(6, channelWidth, deviceABssid)
+			)
 		);
-		dataModel.latestState.put(
+		dataModel.latestStates.put(
 			deviceB,
-			TestUtils.createState(11, channelWidth, deviceBBssid)
+			Arrays.asList(
+				TestUtils.createState(11, channelWidth, deviceBBssid)
+			)
 		);
 		dataModel.latestDeviceStatusRadios.put(
 			deviceA,

src/test/java/com/facebook/openwifirrm/optimizers/channel/UnmanagedApAwareChannelOptimizerTest.java

@@ -56,9 +56,13 @@ public class UnmanagedApAwareChannelOptimizerTest {
 			deviceA,
 			TestUtils.createDeviceStatus(band, aExpectedChannel)
 		);
-		dataModel.latestState.put(
+		dataModel.latestStates.put(
 			deviceA,
-			TestUtils.createState(aExpectedChannel, channelWidth, bssidA)
+			Arrays
+				.asList(
+					TestUtils
+						.createState(aExpectedChannel, channelWidth, bssidA)
+				)
 		);
 		dataModel.latestWifiScans.put(
 			deviceA,
@@ -80,9 +84,9 @@ public class UnmanagedApAwareChannelOptimizerTest {
 			deviceB,
 			TestUtils.createDeviceStatus(band, 40)
 		);
-		dataModel.latestState.put(
+		dataModel.latestStates.put(
 			deviceB,
-			TestUtils.createState(40, channelWidth, bssidB)
+			Arrays.asList(TestUtils.createState(40, channelWidth, bssidB))
 		);
 		dataModel.latestWifiScans.put(
 			deviceB,
@@ -114,9 +118,9 @@ public class UnmanagedApAwareChannelOptimizerTest {
 			deviceC,
 			TestUtils.createDeviceStatus(band, 149)
 		);
-		dataModel.latestState.put(
+		dataModel.latestStates.put(
 			deviceC,
-			TestUtils.createState(149, channelWidth, bssidC)
+			Arrays.asList(TestUtils.createState(149, channelWidth, bssidC))
 		);
 		dataModel.latestWifiScans.put(
 			deviceC,
@@ -160,9 +164,13 @@ public class UnmanagedApAwareChannelOptimizerTest {
 			deviceA,
 			TestUtils.createDeviceStatus(band, aExpectedChannel)
 		);
-		dataModel.latestState.put(
+		dataModel.latestStates.put(
 			deviceA,
-			TestUtils.createState(aExpectedChannel, channelWidth, bssidA)
+			Arrays
+				.asList(
+					TestUtils
+						.createState(aExpectedChannel, channelWidth, bssidA)
+				)
 		);
 		dataModel.latestWifiScans.put(
 			deviceA,
@@ -182,9 +190,9 @@ public class UnmanagedApAwareChannelOptimizerTest {
 			deviceB,
 			TestUtils.createDeviceStatus(band, 6)
 		);
-		dataModel.latestState.put(
+		dataModel.latestStates.put(
 			deviceB,
-			TestUtils.createState(6, channelWidth, bssidB)
+			Arrays.asList(TestUtils.createState(6, channelWidth, bssidB))
 		);
 		dataModel.latestWifiScans.put(
 			deviceB,
@@ -200,9 +208,9 @@ public class UnmanagedApAwareChannelOptimizerTest {
 			deviceC,
 			TestUtils.createDeviceStatus(band, 6)
 		);
-		dataModel.latestState.put(
+		dataModel.latestStates.put(
 			deviceC,
-			TestUtils.createState(6, channelWidth, bssidC)
+			Arrays.asList(TestUtils.createState(6, channelWidth, bssidC))
 		);
 		dataModel.latestWifiScans.put(
 			deviceC,

src/test/java/com/facebook/openwifirrm/optimizers/tpc/LocationBasedOptimalTPCTest.java

@@ -132,17 +132,19 @@ public class LocationBasedOptimalTPCTest {
 				device,
 				TestUtils.createDeviceStatus(UCentralConstants.BANDS)
 			);
-			dataModel.latestState.put(
+			dataModel.latestStates.put(
 				device,
-				TestUtils.createState(
-					DEFAULT_CHANNEL_2G,
-					DEFAULT_CHANNEL_WIDTH,
-					DEFAULT_TX_POWER,
-					dummyBssid,
-					DEFAULT_CHANNEL_5G,
-					DEFAULT_CHANNEL_WIDTH,
-					DEFAULT_TX_POWER,
-					dummyBssid
+				Arrays.asList(
+					TestUtils.createState(
+						DEFAULT_CHANNEL_2G,
+						DEFAULT_CHANNEL_WIDTH,
+						DEFAULT_TX_POWER,
+						dummyBssid,
+						DEFAULT_CHANNEL_5G,
+						DEFAULT_CHANNEL_WIDTH,
+						DEFAULT_TX_POWER,
+						dummyBssid
+					)
 				)
 			);
 		}
@@ -199,17 +201,19 @@ public class LocationBasedOptimalTPCTest {
 				device,
 				TestUtils.createDeviceStatus(UCentralConstants.BANDS)
 			);
-			dataModel2.latestState.put(
+			dataModel2.latestStates.put(
 				device,
-				TestUtils.createState(
-					DEFAULT_CHANNEL_2G,
-					DEFAULT_CHANNEL_WIDTH,
-					DEFAULT_TX_POWER,
-					dummyBssid,
-					DEFAULT_CHANNEL_5G,
-					DEFAULT_CHANNEL_WIDTH,
-					DEFAULT_TX_POWER,
-					dummyBssid
+				Arrays.asList(
+					TestUtils.createState(
+						DEFAULT_CHANNEL_2G,
+						DEFAULT_CHANNEL_WIDTH,
+						DEFAULT_TX_POWER,
+						dummyBssid,
+						DEFAULT_CHANNEL_5G,
+						DEFAULT_CHANNEL_WIDTH,
+						DEFAULT_TX_POWER,
+						dummyBssid
+					)
 				)
 			);
 		}
@@ -220,13 +224,15 @@ public class LocationBasedOptimalTPCTest {
 					Arrays.asList(UCentralConstants.BAND_5G)
 				)
 			);
-		dataModel2.latestState.put(
+		dataModel2.latestStates.put(
 			deviceC,
-			TestUtils.createState(
-				DEFAULT_CHANNEL_5G,
-				DEFAULT_CHANNEL_WIDTH,
-				DEFAULT_TX_POWER,
-				dummyBssid
+			Arrays.asList(
+				TestUtils.createState(
+					DEFAULT_CHANNEL_5G,
+					DEFAULT_CHANNEL_WIDTH,
+					DEFAULT_TX_POWER,
+					dummyBssid
+				)
 			)
 		);
 
@@ -308,17 +314,19 @@ public class LocationBasedOptimalTPCTest {
 				device,
 				TestUtils.createDeviceStatus(UCentralConstants.BANDS)
 			);
-			dataModel2.latestState.put(
+			dataModel2.latestStates.put(
 				device,
-				TestUtils.createState(
-					DEFAULT_CHANNEL_2G,
-					DEFAULT_CHANNEL_WIDTH,
-					DEFAULT_TX_POWER,
-					dummyBssid,
-					DEFAULT_CHANNEL_5G,
-					DEFAULT_CHANNEL_WIDTH,
-					DEFAULT_TX_POWER,
-					dummyBssid
+				Arrays.asList(
+					TestUtils.createState(
+						DEFAULT_CHANNEL_2G,
+						DEFAULT_CHANNEL_WIDTH,
+						DEFAULT_TX_POWER,
+						dummyBssid,
+						DEFAULT_CHANNEL_5G,
+						DEFAULT_CHANNEL_WIDTH,
+						DEFAULT_TX_POWER,
+						dummyBssid
+					)
 				)
 			);
 		}
@@ -367,17 +375,19 @@ public class LocationBasedOptimalTPCTest {
 				device,
 				TestUtils.createDeviceStatus(UCentralConstants.BANDS)
 			);
-			dataModel3.latestState.put(
+			dataModel3.latestStates.put(
 				device,
-				TestUtils.createState(
-					DEFAULT_CHANNEL_2G,
-					DEFAULT_CHANNEL_WIDTH,
-					DEFAULT_TX_POWER,
-					dummyBssid,
-					DEFAULT_CHANNEL_5G,
-					DEFAULT_CHANNEL_WIDTH,
-					DEFAULT_TX_POWER,
-					dummyBssid
+				Arrays.asList(
+					TestUtils.createState(
+						DEFAULT_CHANNEL_2G,
+						DEFAULT_CHANNEL_WIDTH,
+						DEFAULT_TX_POWER,
+						dummyBssid,
+						DEFAULT_CHANNEL_5G,
+						DEFAULT_CHANNEL_WIDTH,
+						DEFAULT_TX_POWER,
+						dummyBssid
+					)
 				)
 			);
 		}
@@ -416,17 +426,19 @@ public class LocationBasedOptimalTPCTest {
 				device,
 				TestUtils.createDeviceStatus(UCentralConstants.BANDS)
 			);
-			dataModel4.latestState.put(
+			dataModel4.latestStates.put(
 				device,
-				TestUtils.createState(
-					DEFAULT_CHANNEL_2G,
-					DEFAULT_CHANNEL_WIDTH,
-					DEFAULT_TX_POWER,
-					dummyBssid,
-					DEFAULT_CHANNEL_2G,
-					DEFAULT_CHANNEL_WIDTH,
-					DEFAULT_TX_POWER,
-					dummyBssid
+				Arrays.asList(
+					TestUtils.createState(
+						DEFAULT_CHANNEL_2G,
+						DEFAULT_CHANNEL_WIDTH,
+						DEFAULT_TX_POWER,
+						dummyBssid,
+						DEFAULT_CHANNEL_2G,
+						DEFAULT_CHANNEL_WIDTH,
+						DEFAULT_TX_POWER,
+						dummyBssid
+					)
 				)
 			);
 		}

src/test/java/com/facebook/openwifirrm/optimizers/tpc/MeasurementBasedApApTPCTest.java

@@ -92,13 +92,15 @@ public class MeasurementBasedApApTPCTest {
 		for (int i = 0; i < devices.size(); i++) {
 			String device = devices.get(i);
 			String bssid = bssids.get(i);
-			model.latestState.put(
+			model.latestStates.put(
 				device,
-				TestUtils.createState(
-					channel,
-					DEFAULT_CHANNEL_WIDTH,
-					MAX_TX_POWER,
-					bssid
+				Arrays.asList(
+					TestUtils.createState(
+						channel,
+						DEFAULT_CHANNEL_WIDTH,
+						MAX_TX_POWER,
+						bssid
+					)
 				)
 			);
 			model.latestDeviceStatusRadios.put(
@@ -130,17 +132,19 @@ public class MeasurementBasedApApTPCTest {
 		for (int i = 0; i < devices.size(); i++) {
 			String device = devices.get(i);
 			String bssid = bssids.get(i);
-			model.latestState.put(
+			model.latestStates.put(
 				device,
-				TestUtils.createState(
-					channel2G,
-					DEFAULT_CHANNEL_WIDTH,
-					MAX_TX_POWER,
-					bssid,
-					channel5G,
-					DEFAULT_CHANNEL_WIDTH,
-					MAX_TX_POWER,
-					bssid
+				Arrays.asList(
+					TestUtils.createState(
+						channel2G,
+						DEFAULT_CHANNEL_WIDTH,
+						MAX_TX_POWER,
+						bssid,
+						channel5G,
+						DEFAULT_CHANNEL_WIDTH,
+						MAX_TX_POWER,
+						bssid
+					)
 				)
 			);
 			model.latestDeviceStatusRadios.put(
@@ -569,13 +573,15 @@ public class MeasurementBasedApApTPCTest {
 		);
 
 		// now test when device C does not have a 5G radio
-		dataModel.latestState.put(
+		dataModel.latestStates.put(
 			DEVICE_C,
-			TestUtils.createState(
-				1,
-				DEFAULT_CHANNEL_WIDTH,
-				MAX_TX_POWER,
-				BSSID_C
+			Arrays.asList(
+				TestUtils.createState(
+					1,
+					DEFAULT_CHANNEL_WIDTH,
+					MAX_TX_POWER,
+					BSSID_C
+				)
 			)
 		);
 		dataModel.latestDeviceStatusRadios.put(

src/test/java/com/facebook/openwifirrm/optimizers/tpc/MeasurementBasedApClientTPCTest.java

@@ -55,25 +55,41 @@ public class MeasurementBasedApClientTPCTest {
 		);
 
 		DataModel dataModel = new DataModel();
-		dataModel.latestState.put(
+		dataModel.latestStates.put(
 			deviceA,
-			TestUtils.createState(36, 20, 20, null, new int[] {})
+			Arrays.asList(
+				TestUtils.createState(36, 20, 20, null, new int[] {})
+			)
 		);
-		dataModel.latestState.put(
+		dataModel.latestStates.put(
 			deviceB,
-			TestUtils.createState(36, 20, 20, "", new int[] { -65 })
+			Arrays.asList(
+				TestUtils.createState(36, 20, 20, "", new int[] { -65 })
+			)
 		);
-		dataModel.latestState.put(
+		dataModel.latestStates.put(
 			deviceC,
-			TestUtils.createState(36, 40, 21, null, new int[] { -65, -73, -58 })
+			Arrays.asList(
+				TestUtils.createState(
+					36,
+					40,
+					21,
+					null,
+					new int[] { -65, -73, -58 }
+				)
+			)
 		);
-		dataModel.latestState.put(
+		dataModel.latestStates.put(
 			deviceD,
-			TestUtils.createState(36, 20, 22, null, new int[] { -80 })
+			Arrays.asList(
+				TestUtils.createState(36, 20, 22, null, new int[] { -80 })
+			)
 		);
-		dataModel.latestState.put(
+		dataModel.latestStates.put(
 			deviceE,
-			TestUtils.createState(36, 20, 23, null, new int[] { -45 })
+			Arrays.asList(
+				TestUtils.createState(36, 20, 23, null, new int[] { -45 })
+			)
 		);
 
 		TPC optimizer = new MeasurementBasedApClientTPC(
@@ -136,35 +152,41 @@ public class MeasurementBasedApClientTPCTest {
 
 		DataModel dataModel = new DataModel();
 		// 2G only
-		dataModel.latestState.put(
+		dataModel.latestStates.put(
 			deviceA,
-			TestUtils.createState(1, 20, 20, null, new int[] {})
+			Arrays.asList(
+				TestUtils.createState(1, 20, 20, null, new int[] {})
+			)
 		);
 		// 5G only
-		dataModel.latestState.put(
+		dataModel.latestStates.put(
 			deviceB,
-			TestUtils.createState(36, 20, 20, null, new int[] {})
+			Arrays.asList(
+				TestUtils.createState(36, 20, 20, null, new int[] {})
+			)
 		);
 		// 2G and 5G
-		dataModel.latestState.put(
+		dataModel.latestStates.put(
 			deviceC,
-			TestUtils.createState(
-				1,
-				20,
-				20,
-				null,
-				new int[] {},
-				36,
-				20,
-				20,
-				null,
-				new int[] {}
+			Arrays.asList(
+				TestUtils.createState(
+					1,
+					20,
+					20,
+					null,
+					36,
+					20,
+					20,
+					null
+				)
 			)
 		);
 		// No valid bands in 2G or 5G
-		dataModel.latestState.put(
+		dataModel.latestStates.put(
 			deviceD,
-			TestUtils.createState(25, 20, 20, null, new int[] {})
+			Arrays.asList(
+				TestUtils.createState(25, 20, 20, null, new int[] {})
+			)
 		);
 
 		TPC optimizer = new MeasurementBasedApClientTPC(
@@ -220,17 +242,29 @@ public class MeasurementBasedApClientTPCTest {
 		deviceDataManager.setDeviceLayeredConfig(deviceLayeredConfig);
 
 		DataModel dataModel = new DataModel();
-		dataModel.latestState.put(
+		dataModel.latestStates.put(
 			deviceA,
-			TestUtils.createState(36, 20, 20, null, new int[] {})
+			Arrays.asList(
+				TestUtils.createState(36, 20, 20, null, new int[] {})
+			)
 		);
-		dataModel.latestState.put(
+		dataModel.latestStates.put(
 			deviceB,
-			TestUtils.createState(36, 20, 20, "", new int[] { -65 })
+			Arrays.asList(
+				TestUtils.createState(36, 20, 20, "", new int[] { -65 })
+			)
 		);
-		dataModel.latestState.put(
+		dataModel.latestStates.put(
 			deviceC,
-			TestUtils.createState(36, 40, 21, null, new int[] { -65, -73, -58 })
+			Arrays.asList(
+				TestUtils.createState(
+					36,
+					40,
+					21,
+					null,
+					new int[] { -65, -73, -58 }
+				)
+			)
 		);
 
 		TPC optimizer = new MeasurementBasedApClientTPC(

src/test/java/com/facebook/openwifirrm/optimizers/tpc/RandomTxPowerInitializerTest.java

@@ -63,26 +63,30 @@ public class RandomTxPowerInitializerTest {
 	 */
 	private static DataModel createModel() {
 		DataModel dataModel = new DataModel();
-		dataModel.latestState.put(
+		dataModel.latestStates.put(
 			DEVICE_A,
-			TestUtils.createState(
-				36,
-				DEFAULT_CHANNEL_WIDTH,
-				DEFAULT_TX_POWER,
-				BSSID_A,
-				2,
-				DEFAULT_CHANNEL_WIDTH,
-				DEFAULT_TX_POWER,
-				BSSID_A
+			Arrays.asList(
+				TestUtils.createState(
+					36,
+					DEFAULT_CHANNEL_WIDTH,
+					DEFAULT_TX_POWER,
+					BSSID_A,
+					2,
+					DEFAULT_CHANNEL_WIDTH,
+					DEFAULT_TX_POWER,
+					BSSID_A
+				)
 			)
 		);
-		dataModel.latestState.put(
+		dataModel.latestStates.put(
 			DEVICE_B,
-			TestUtils.createState(
-				2,
-				DEFAULT_CHANNEL_WIDTH,
-				DEFAULT_TX_POWER,
-				BSSID_B
+			Arrays.asList(
+				TestUtils.createState(
+					2,
+					DEFAULT_CHANNEL_WIDTH,
+					DEFAULT_TX_POWER,
+					BSSID_B
+				)
 			)
 		);
 		return dataModel;