There are many technologies like Zigbee,BLE,Z-waveANT ,Thread etc. supporting mesh, are doing rounds in the IOT space.The Zigbee and Z-wave are the older versions of short range technologies working reliably. But the Z-Wave and Zigbee require the Hus or Getway to communicate the data to the clouds. This may alter the data integrity or may cause the data-loss. The Thread protocol, promoted by Thread Group tries to solve this issue by providing direct connectivity to the cloud as it is IP based. That eases the case for cloud communication with mesh network.
What is Thread Protocol?
The Thread is a secure,low power ,ipv6 wireless protocol which supports mesh.This Protocol operates in the Licence free-band i.e. 2.4 Ghz. This protocol is based on the 6 Lowpan.This is independent of application layer. Any manufacturer can use it for whatever Application layer it prefers i.e. Zigbee,Matter.(which is latest technology for Home Automation)
Thread is promoted by the Thread Group which is formed by big players like Google,Amazon,Samsumg,nxp etc.The thread was initially was targeting Home Automation but it extended to Building Automation,Lighting, Hvac etc. The thread is secure,scalable and flexible network which can work independent of Internet.
Thread Network
The Thread supports the different device types and different roles.
Device Roles
The Tread devices can take on the roles like End Device,Router,Router Eligible end device,Border Router,Leader Router. Initially every device in the network is End Device.As per the requirement the REED can be promoted to the role of Router.
End Device:This thread device does not relay the messages but remains connected to its parent router.The end device sleeps and wakes up when it is required to send the data or poll the parent for any message.
REED or Router Eligible End Device:It is an End device with capability to become router when needed.Otherwise its acts as a End device which does not forward the messages in the mesh network but depends on the parent Router for communicating messages.
Router:This device can receive and transmits and forward the data in the mesh network.It can play the role of a Parent Router for one or multiple End Devices.The Router maintains the data regarding next hop,cost,Link and list of Routers in the mesh network.
Leader Router:This Router acts as a leader of the mesh network which can take decisions like role upgrade,current active commissioner and controlling the router.It is elected by the Router present in the thread network.
Border Router:This router acts as bridge between outside network which may be non-Thread network like Cloud.It supports the both protocol WiFi and thread.
Thread Device Types: Thread has two types of Devices,FTD(Full Thread Device) and MTD(Minimal Thread Device).
FTD or Full Thread Device: The full thread Device has its receiver always on and are generally,mains powered.The Full Thread Devices are Router,an End Device,Leader Router,REED and Border Router.Initially all devices join as an End Device.When need arises then REED can upgrade to Router or Router changes to End Device Role.The Full End Device receives the messages form the Parent Router.The Full End Devices also receives messages form neighbouring Routers.
MTD or Minimal Thread Device:The minimal Thread Devices are restricted to End Devices only..The Minimal thread Devices are of two types Minimal End Device and sleepy End Device.The receiver of minimal thread device is always on so it does not have to poll the parent.While sleepy End Device sleeps for most of the time and wakes up to poll the parent or send the data.
Joining Thread Network
Joining the network consists of Commissioning and Attaching.
Commissioning: The commissioning is a process where an unattached device is authenticated and securely brought into the thread network. The commissioning is of two types and external commissioning and internal commissioning.In external commissioning,the commissioner lies off-mesh network i.e may Ble Or WiFi network.In this case,the communication is done using Border Router.In Internal commissioning case,the commissioner lies on on-mesh network.
Attaching: When commissioning process is complete then process of attaching starts.In this case the device sends the multicast Parent Request, the nearby routers receive the request and sends Parent Response.The Device then selects the appropriate parent and send Child ID request to the Parent.The Parent Router then responds with child ID response. Thus the device becomes part of the network.
Network Maintenance
The network maintenance is done through out the lifetime the network to keep reliability.The Router and REED does this job to maintain reliable connectivity. The Router or REED does following functions.
Advertisement:The Router sends advertising across the network using Trickle Algorithm.When a router or Reed multicast the advertisement it informs other routers about its path.
Other Router use information from this path to evaluate link quality, cost for reliable connectivity.The Router discover the optimal path and can adapt that path. The advertisement updates data regarding the neighboring Routers.
Dynamic Routers: The Router REED may changes their roles as per need of the network. The REED can covert itself to Router role for better network connectivity or to accommodate more end devices. The Router may convert to REED when there is sufficient redundancy of router. To decision to change the is to be approved by the Leader Router.
Partition: The goal of the Thread network is to keep the connectivity intact. Sometimes, Router or REED may find that they are disconnected from the leader of the network.It may be due to several reasons .i.e. Leader would have lost power/In that case, the Router can find the nearby partition to join. But it does not find one then it can form partition of own. It may also try to find new strong partition to join. A thread network can have many partitions. The Network may optimize few partitions to form less but powerful partitions.
Applications
1. Home Automation
2. Lighting
3. Building Automation
4, Industrial Automation
5. Healthcare
6. HVAC
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