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Energy Profiling of Bluetooth Mesh Nodes in Wireless Sensor Networks

This example shows energy profiling of different types of nodes in a Bluetooth® mesh network using the Communications Toolbox™ Library for the Bluetooth® Protocol. Energy is computed based on the time profiled by End nodes, Low Power nodes (LPNs), Friend nodes, and Relay nodes in transmission, listen, sleep, and idle state. Using this example, you can:

  • Create and configure a Bluetooth mesh network

  • Visualize the impact of mesh message exchange on the energy performance of End node, LPN, Friend node, and Relay node

  • Observe the energy consumption of mesh nodes by varying the number of source-destination pair, Friend node-LPN pair, and the application traffic.

  • Estimate the node lifetime based on the hardware-specific energy parameters

  • Modify the hardware-specific energy parameters to suit your requirements

  • Explore the impact of poll timeout and receive window size on the node lifetime

The simulation calculates the lifetime of an LPN with the specified configuration and the hardware-specific energy parameters. The results validate that LPN always consume less energy by spending more time in sleep, resulting in energy conservation and increased lifetime.

Bluetooth Mesh Stack

The Bluetooth Core Specification [ 1 ] includes a Low Energy version for low-rate wireless personal area networks, referred to as Bluetooth low energy (BLE) or Bluetooth Smart. The BLE stack consists of generic attribute profile (GATT), attribute protocol (ATT), security manager protocol (SMP), logical link control and adaptation protocol (L2CAP), link layer (LL) and physical layer. The Special Interest Group (SIG) added BLE to the Bluetooth standard for low energy devices which generate small amounts of data such as notification alerts used in such applications as home automation, health-care, fitness, and Internet of Things (IoT). For more information about BLE protocol stack, see Bluetooth Protocol Stack.

The Bluetooth mesh profile [ 2 ] defines the fundamental requirements to implement a mesh networking solution for BLE. The mesh stack is located on top of the BLE core specification and consists of model layer, foundation model layer, access layer, upper transport layer, lower transport layer, network layer and bearer layer. Bluetooth mesh networking enables large-scale device networks in the applications such as smart lighting, industrial automation, sensor networking, asset tracking, and many other IoT solutions. For more information about Bluetooth mesh stack, see Bluetooth Mesh Networking.

Each Bluetooth mesh node can possess some optional features enabling them to acquire additional, special capabilities. These features include the Relay, Proxy, Friend, and the Low Power features. The Bluetooth mesh nodes possessing these features are known as Relay nodes, Proxy nodes, Friend nodes, and Low Power nodes (LPNs), respectively. To reduce the duty cycles of the LPN and conserve energy, the LPN must establish a Friendship with a mesh node supporting the Friend feature. This Friendship between the LPN and the Friend nodes (mesh nodes supporting the Friend feature) enables the Friend node to store and forward messages addressed to the LPN. Forwarding by the Friend node occurs only when the LPN wakes up and polls the Friend node for messages awaiting delivery. This mechanism enables all of the LPNs to conserve energy and operate for longer durations.

For more information about devices, nodes, and the Friendship in Bluetooth mesh network, see Bluetooth Mesh Networking.

The main objectives of this example are:

  1. Create and configure a Bluetooth mesh network

  2. Visualize message flooding

  3. Analyze the behavior of Friendship in the Bluetooth mesh network

  4. Profile the energy consumed by each node in the Bluetooth mesh network

Check for Support Package Installation

% Check if the 'Communications Toolbox Library for the Bluetooth Protocol'
% support package is installed or not.
commSupportPackageCheck('BLUETOOTH');

Bluetooth Mesh Energy Profiling Simulation

In the simulation, a source node initiates and relays a sample mesh message to a destination node. To relay mesh messages to multiple destination nodes, the source nodes transmits the messages to a common group address. During the simulation, the Friend nodes and LPNs exchange Friendship messages. Each node computes the time spent in various states (transmission, listen, idle and sleep) and calculates its lifetime.

To create and visualize the mesh network, use helperBLEMeshNode and helperBLEMeshVisualizeNetwork classes. Specify the number of nodes (NumberofNodes) and the type of node position (NodePositionType) in helperBLEMeshVisualizeNetwork function. The default type of node position is 'Grid'. To specify your own network, set the value of NodePositionType to 'UserInput' and node positions to Positions.

% Set random number generator seed to 'default'
sprev = rng('default');

% Specify the number of nodes in the mesh network
totalNodes = 55;

% Initialize 'bleMeshNodes' vector with objects of type helperBLEMeshNode
meshNodes(1, totalNodes) = helperBLEMeshNode();

% Configure each mesh node with unique identifier
for nodeIdx = 1:totalNodes
    meshNode = helperBLEMeshNode();
    meshNode.Identifier = nodeIdx;
    meshNodes(nodeIdx) = meshNode;
end

% Load node positions from the MAT file
load('bleMeshNodesPositions.mat');

% Create and Configure the visualization object for Bluetooth mesh network
meshNetworkGraph = helperBLEMeshVisualizeNetwork();
meshNetworkGraph.NumberOfNodes = totalNodes;

% Set the type of the node position allocation as 'Grid' or 'UserInput'
meshNetworkGraph.NodePositionType = 'UserInput';

% Set node positions based on number of nodes (applicable for 'UserInput'),
% in meters
meshNetworkGraph.Positions = bleMeshNodesPositions;

% Set vicinity range (in meters) based on node positions, in meters
meshNetworkGraph.VicinityRange = 25;

% Set title to the network visualization
meshNetworkGraph.Title = 'Energy Profiling in Bluetooth Mesh Network';

Specify the number of source and destination pairs by using sourceDestinationPairs variable. To specify Friend node and LPN pairs, use friendLowPowerPairs variable. To specify the Relay nodes in the network, use relayNodeIDs variable. Configure the mesh node objects related to each mesh node. The paths variable store the paths obtained for each source and destination pair.

% Specify the simulation time (in milliseconds)
simulationTime = 6000;

% Enable or disable visualization
enableVisualization = true;

% Enable or disable the animation in the visualization. If
% "enableVisualization" is set to false, the simulation does not considers
% "enableAnimation".
enableAnimation = false;

% Specify the source and destination pairs. Source node transmits sample
% mesh message to destination node.
sourceDestinationPairs = [1 52; 1 17; 12 7; 6 53; 54 51; 9 33; 18 52; ...
    29 52; 31 7; 12 9; 54 53; 55 1; 9 17; 18 35];

% Specify the time to live (TTL) value (in the range [0, 127]) for each
% source and destination pair
ttl = [20 23 35 21 23 30 22 20 23 35 21 23 30 22];

% Specify the Friend node and LPN
friendLowPowerPairs = [16 52];

% Specify the receive window (in milliseconds) for each Friend and LPN
% pair. This value is in the range [120, 255]
receiveWindow = 180;

% Specify the poll timeout (in seconds) for each Friend and LPN pair. The
% value is in the range [2 seconds, 95.9 hours].
pollTimeout = 20;

% Specify the relay nodes
relayNodeIDs = [3 4 5 8 10 11 15 19 20 21 23 25 28 30 32 34 36 37 38 39 41 ...
    42 43 44 45 46 47 48 49 26 2 16 13 27];

% Simulate the Bluetooth mesh network
[meshNodes, paths] = helperBLEMeshSimulation(meshNodes, totalNodes, meshNetworkGraph, ...
    simulationTime, sourceDestinationPairs, ttl, friendLowPowerPairs, receiveWindow, ...
    pollTimeout, relayNodeIDs, enableVisualization, enableAnimation);

% Restore the previous setting of random number generation
rng(sprev);

Simulation Results

At each mesh node, the simulation captures these statistics.

  • Time spent in transmission state

  • Time spent in listening state

  • Time spent in sleep state

  • Time spent in idle state

  • Number of messages transmitted from the node

  • Number of messages received by the node

  • Number of messages relayed by the node

  • Number of messages dropped at the node

  • Number of messages received with cyclic redundancy check (CRC) failures

The workspace variable, statisticsAtEachNode, contains the cumulative value of the preceding statistics for all the nodes in the network. For a given simulation run, you can view the statistics for first five nodes. The network statistics for the first five nodes in the network are:

% Statistics for first five nodes
statisticsAtEachNode = helperBLEMeshNodesStatistics(meshNodes);
statisticsForFirstFiveNodes = statisticsAtEachNode(1:min(totalNodes, 5), :)
statisticsForFirstFiveNodes =

  5x14 table

              NodeType    TransmittedMsgs    ReceivedMsgs    ReceivedMsgsFromLPN    ReceivedApplicationMsgs    RelayedMsgs    DroppedMsgs    CRCFailedMsgs    TotalTransmittedBytes    TotalReceivedBytes    SleepTime (milliseconds)    IdleTime (milliseconds)    ListenTime (milliseconds)    TransmissionTime (milliseconds)
              ________    _______________    ____________    ___________________    _______________________    ___________    ___________    _____________    _____________________    __________________    ________________________    _______________________    _________________________    _______________________________

    Node_1     End               6                10                  0                        1                    0              9               0                   171                    284                       0                         123.5                        5871                           1.368             
    Node_2     Relay            15                 6                  0                        0                    5              1               0                   426                    170                       0                           187                        5800                           3.408             
    Node_3     Relay            15                24                  0                        0                    5             19               0                   426                    685                       0                           178                        5809                           3.408             
    Node_4     Relay            12                20                  0                        0                    4             14               2                   339                    566                       0                           168                      5821.5                           2.712             
    Node_5     Relay            12                10                  0                        0                    4              4               2                   339                    285                       0                           168                      5821.5                           2.712             

This plot shows the average time spent by different type of mesh nodes in different states. The results conclude that the LPN spend most of the time in sleep state, resulting in energy conservation and increased lifetime.

fprintf('Average time statistics of different Bluetooth mesh nodes are:\n');
meshNodesAvgStats = helperBLEMeshNodeAverageTime(meshNodes)
Average time statistics of different Bluetooth mesh nodes are:

meshNodesAvgStats =

  4x5 table

    Type of Bluetooth mesh node    Transmission time (milliseconds)    Listen time (milliseconds)    Idle time (milliseconds)    Sleep time (milliseconds)
    ___________________________    ________________________________    __________________________    ________________________    _________________________

          Low Power node                         2.304                              720                         103                       5166.5          
          Friend node                            6.192                           5771.5                       205.5                            0          
          Relay node                            3.3869                           5801.4                       185.7                            0          
          End node                              0.4836                           5907.4                        90.3                            0          

The simulation consists of single message transmission from source node to destination node. Configure the traffic between the mesh nodes by using the pushModelMessage function periodically. The transmission time at the End node depends on the application traffic. The transmission time at the LPN depends on the poll timeout value.

Further Exploration

Calculate Lifetime of LPN:

Use helperBLEMeshNodeLifetime function to calculate the lifetime of a node in the Bluetooth mesh network at the end of simulation. To compute node lifetime, the simulationTime and the mesh node object of type helperBLEMeshNode is given as an input to the helperBLEMeshNodeLifetime function. The node lifetime is calculated by using the energy parameters that are hardware dependent. To update these hardware parameters, use helperBLEMeshNodeLifetime function.

% Fetch one of the Low Power nodes for calculating the lifetime
meshNode = meshNodes(52);
lifeTime = helperBLEMeshNodeLifetime(meshNode, simulationTime);
fprintf('Lifetime of node %d is %.4f days.\n', meshNode.Identifier, lifeTime);
Configured hardware parameters for a 1200 mAh battery are:

hardwareParameters =

  7x2 table

       Hardware parameters        Configured values (mA)
    __________________________    ______________________

    Self-discharge                      0.0013699       
    Transmission on channel 37               7.57       
    Transmission on channel 38               7.77       
    Transmission on channel 39                7.7       
    Listening                                10.3       
    Sleep                                     0.2       
    Idle                                     1.19       

Statistics at node 52 are:

statisticsAtNode =

  4x2 table

     Time variables      Time (milliseconds)
    _________________    ___________________

    Transmission time           2.304       
    Listen time                   720       
    Sleep time                 5166.5       
    Idle time                     103       

Lifetime of node 52 is 34.8927 days.

Lifetime of LPN by Varying Poll Timeout

The lifetime of a LPN depends on the time for which the node is in the listen state. In a given poll timeout, a LPN is in listen or sleep state for most of the time. The receive window for each poll request of a LPN determines the time spent in listen state. The time spent in transmission state is negligible.

Visualize the impact of the poll timeout and receive window on the lifetime of LPN by using the helperBLEMeshLPNLifetimeVSPolltimeout function.

The preceding plot concludes that the lifetime of LPN is directly proportional to the poll timeout. The poll timeout specifies the maximum time between two consecutive requests from an LPN to Friend node. As the poll timeout increases, the LPN spends more time in sleep state that results in increasing the lifetime of the LPN.

This example shows how to create and configure a multinode Bluetooth mesh network and analyze the message exchange in the network. This example also enables you to analyze the behavior and the advantages of the Friendship between Friend node and LPN. To calculate the time spent by each node on different states the Bluetooth mesh node is simulated with multiple Friend and Low Power node pairs. The plot of the average time spent by each node in different states show that the LPNs always consume less energy by spending more time in sleep state. You can further explore the energy profiling of LPN by varying the poll timeout and receive window values.

Appendix

The example uses these features:

The example uses these helpers:

Selected Bibliography

  1. Bluetooth Special Interest Group (SIG). "Bluetooth Core Specification". Version 5.0. https://www.bluetooth.com/.

  2. Bluetooth Special Interest Group (SIG). "Bluetooth Mesh Profile". Version 1.0. https://www.bluetooth.com/.

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