Advantages of Bluetooth mesh | Disadvantages of Bluetooth mesh

This page covers advantages and disadvantages of Bluetooth mesh technology and its architecture. It mentions benefits or advantages of Bluetooth mesh and drawbacks or disadvantages of Bluetooth mesh technology.

Introduction: The classic bluetooth technology was introduced in 1999. It is managed by bluetooth SIG and uses radio frequencies from 2402 MHz to 2480 MHz. The main function of bluetooth is to transmit data over short distances. Initial version supports 79 channels with 1 MHz spacing. BLE ( Bluetooth Low Energy) 4.0 version was launched in 2010 with the aim of extremely low power consumption. BLE supports about 40 channels at the spacing of 2MHz. BLE technology enables connection between devices using master-slave concept. It uses GATT protocol for data transmission. Bluetooth 5.0 version has been developed to support 240 meters coverage and 2 Mbps speed.

What is Bluetooth mesh technology?

Earlier versions of bluetooth support one to one and one to many topologies. Bluetooth mesh specification was launched in 2017 which allows devices to operate in many to many topology. Bluetooth mesh is built on top of BLE. The main goal to develop bluetooth mesh is to increase range of existing bluetooth networks and to support more industrial applications of BLE technology. BLE mesh uses advertising and scanning states of nodes to relay messages. Devices which are part of mesh network are called nodes. The other bluetooth enabled devices such as smartphones or tablets or any boards are called unprovisioned devices. When these devices get provisioned, they are called as "nodes". As per BLE mesh ver 1.0, it supports about 32767 nodes and 127 hops. It does not use IP (Internet protocol) as it has been developed on top of the BLE stack.

Bluetooth mesh architecture

The figure depicts bluetooth mesh architecture with different types of nodes. It uses managed flooding instead of routing techniques used by other mesh technologies. The functions of bluetooth mesh nodes are as follows.
Node : Any device which has joined bluetooth mesh network is called as "node". Node contains multiple parts called as "elements" which are controlled independently. Elements of a node can be in various conditions known as "STATEs" e.g. ON and OFF of a light bulb. Properties are added to the states such as manufacturer or admin property.
Relay node : This node relays or retransmits messages to other nodes. It functions as intermedia nodes for other nodes. This helps message to traverse the network to distant nodes and extend the coverage of mesh network.
Low Power nodes : These nodes are power constraint nodes which stay asleep most of the time and wake up as programmed. They are used mostly to transmit messages.
Friend nodes : They are not power constaint and keep radio on all the time to listen for broadcast messages. This node has friendship relation with low power nodes. It stores messages for low power nodes when they are asleep. When low power nodes become active, they are delivered messages by related friend node.
Proxy node : This node enables communication between mesh nodes and BLE enabled devices not having mesh capabilities. This node implements both mesh and BLE stack functionalities.

Bluetooth mesh supports three types of messages viz. GET, SET and STATUS. Each of these messages are assigned with unique "opcode". Messages in bluetooth mesh contains source and destination addresses which are used to identify its termination node. The type of addresses used are unicast, group address and virtual address. Messages in mesh network are exchanged using publish and subscribe pattern. Refer bluetooth mesh tutorial for more information.

Following three features of BLE ensures reliability of message delivery.
Heartbeat message : Each BLE nodes transmit heartbeat messages periodically in order to inform other nodes in the network about their active state.
TTL (Time to Live) : It controls how far a message can traverse through the network. This value restricts number of times message can be relayed in the network. Each time message is received and relayed, TTL value is decremented by 1. Heartbeat message can be used to set the correct TTL value by the source node.
Message Cache : Each node maintains cache for received messages. Whenever a node receives any new message, it checks its list of catched messages and ignores if it is already present.

Benefits or advantages of Bluetooth Mesh Technology

Following are the benefits or advantages of Bluetooth Mesh Technology:
➨It offers extended range as nodes can relay messages to the nodes which are far away from them.
➨The bluetooth mesh nodes have self healing capabilities. When any node drops or fails from the network, other nodes in the network take care of transmission of messages to the other nodes.
➨It supports global interoperability. Hence products from one vendor will work seamlessly with the other vendor products.
➨BLE mesh is backward compatible with other BLE devices which do not have mesh protocol.
➨Bluetooth mesh runs on top of BLE. Moreover most of the smartphones support BLE 4.0 and BLE 5.0 versions. Hence BLE mesh technology utilizes the existing smartphones and does not require any external hardware devices. Hence it is very cost effective.
➨BLE mesh nodes support end to end security for messages exchanged between them.
➨It is power efficient compare to other mesh technologies due to its friendship node concept.
➨No internet is required once the configuration is downloaded from the cloud server to the smartphone. Later, this smartphone can be used to recover and configure the status of nodes in a bluetooth mesh topology.

Drawbacks or disadvantages of Bluetooth Mesh Technology

Following are the drawbacks or disadvantages of Bluetooth Mesh Technology:
➨Like wireless mesh, bluetooth mesh topology is more complex and it is difficult to build and maintain.
➨Bluetooth mesh is not applicable for transmission of audio and video.
➨Bluetooth mesh supports lower bandwidth compare to WiFi and hence it is used for transmission of small size commands used for open/close functionalities such as light ON or OFF.


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BLE (Bluetooth Low Energy) Links

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