What is a mesh network?

A protocol that enables secure mesh communication between IoT devices with low power consumption

Mesh network

A mesh network is a network system in which wireless devices are connected in a mesh-like pattern and self-form, enabling communication in places where radio waves normally cannot reach.Since multiple terminals (nodes) communicate directly with each other, there are multiple communication paths and data transmission routes are diversified.
In other words, even if a failure occurs somewhere along the communication path, normal communication can be resumed by bypassing the point of failure, making it highly reliable and resistant to failures.

Thread and Zigbee utilize a mesh network topology, where devices are directly linked in a non-hierarchical manner to route data through the network, allowing devices to not only receive data but also act as intermediaries to send data to other devices.

Device Type

As shown in the diagram above, Thread devices can operate as routers (FTDs, or Full Thread Devices) or end devices (MTDs, or Minimal Thread Devices). This is independent of the device's functionality. FTDs are typically connected to mains POWER SUPPLIES, while MTDs are often battery-powered and operate as sleepy end devices. Additionally, the role of an FTD in the network can dynamically change between router and end device to maximize performance.

End Device

End devices communicate only through their parent router and cannot forward messages to other devices. End devices can disable their transceivers to reduce power consumption and operate as sleepy end devices. The relationship between routers and end devices is a parent-child relationship, where the router is always the parent and the end device is the child. An end device can only be connected to one router.

Thread Router

Thread routers provide routing services to Thread devices in a network. Routers also provide joining and security services to devices attempting to join the network. Routers are not designed to sleep, so most are plugged into mains POWER SUPPLIES.

Thread Reader

Thread dynamically elects a leader. Thread expects all routers to be able to act as leader. If the leader fails, another router becomes the leader.

Border Router

Thread provides resilience by maintaining connections to non-Thread devices. Border routers are Thread devices that provide end-to-end IP connectivity between a Thread network and neighboring networks. Many mesh technologies rely on a single hub for connectivity to the outside world. To ensure resilience, Thread supports multiple border routers operating simultaneously, providing redundant paths for communication into the network.

Thread complies with the international standard IEEE802.15.4

The international standards IEEE802.15.1 and IEEE802.11, to which Bluetooth and Wi-Fi conform, initially only supported P2P and Star network topologies, limiting them to relatively simple network configurations such as P2P (1:1) and Star (1:N). In recent years, Bluetooth has been designed with the deployment of large-scale wireless networks in mind as Bluetooth Mesh, making it suitable for smartifying homes and offices with intelligent systems for lighting, heating and cooling equipment, security, and other applications, as well as for building industrial wireless sensor networks.
Furthermore, mesh Wi-Fi automatically configures communication routes like a mesh, making it possible to implement the system without having to worry about network configuration. It is highly reliable and resistant to failures, as it bypasses communication route failures to ensure normal communication.
On the other hand, IEEE802.15.4, which Thread complies with, originally allows all network configurations, including P2P, Star, Tree, and Mesh. In other words, Thread's ability to build a variety of network configurations means it can be used for a variety of applications.

For example, when trying to realize a smart grid, typified by smart meters, it is necessary to network more than 1,000 wireless nodes over a wide area. To achieve this, a mesh network using multi-hopping is required. To realize a mesh network, the IEEE802.15.4 wireless standard, which was formulated with the assumption that it would be compatible with large-scale networks, is required. In other words, it is necessary to select a standard that matches what you want to achieve with your application and the corresponding topology.

6LoWPAN

6LoWPAN, an abbreviation for "IPv6 over Low-power Wireless Personal Area Networks," is a low-power wireless communication protocol designed to efficiently transmit IPv6 packets over IEEE802.15.4. 6LoWPAN specifies packet compression and various optimizations to efficiently transmit IPv6 packets over networks with limited power resources and reliability. This enables efficient IPv6 communication over low-power wireless networks. Thread also uses the 6LoWPAN protocol.

While various low-power wireless networks have been deployed to date, 6LoWPAN is currently considered the primary protocol for IoT. It has the following four main features:

Packet Splitting
Header Compression
Neighbor Discovery
Mesh compatible

The diagram below shows the benefits of packet fragmentation and header compression. First, with packet fragmentation, the data in an IPv6 packet cannot fit directly into an IEEE802.15.4 FRAMES, so the data is fragmented and sent. Next, with header compression, the header portion is compressed to increase the area available for data transmission, thereby improving communication efficiency.

It is necessary to divide the data into pieces that fit within the IEEE802.15.4 FRAMES. Compressing the header section and increasing the area used for data transmission can improve communication efficiency.

Neighbor Discovery is the key process by which devices discover each other and begin communicating within a 6LoWPAN network.

Neighbor Discovery Key Features

1. Address Resolution
The device resolves the IPv6 address of the other device and obtains a link-local address for communication.

2. Neighbor Discovery
Discover other devices in your network and create a list of devices available to connect to.

3. Monitoring connection status
It monitors the connection status between devices and notifies you if a connection is lost or a new device is added.

4. Router Discovery
The device discovers routers in your network and gets information about connecting to the Internet and routing to other networks.

5. Obtaining routing information
Through information from routers, it understands the network topology and available routes.

6. Multicast communication support
It allows you to send messages to multiple devices at once.

6LoWPAN mesh-compatible features

1. Automated routing
6LoWPAN supports automatic routing between devices, allowing each device to not only communicate directly with neighboring devices but also to route data through other devices, maintaining communication even as the network topology changes dynamically.

2. Optimization for low power consumption
6LoWPAN is designed for low-power devices and incorporates protocols for efficient communication within a mesh network. Devices can enter sleep mode when needed and only become active when communication is required.

3. Use of IPv6
6LoWPAN is based on IPv6 and allows each device to be assigned a unique IPv6 address, which allows for a large address space and facilitates direct communication between devices.

As mentioned above, 6LoWPAN is unique compared to other communication standards, particularly in its automatic routing and direct support for IPv6. This allows 6LoWPAN to build flexible networks where low-power devices can dynamically connect and communicate efficiently, making 6LoWPAN a superior choice over other standards, especially in the Internet of Things (IoT) environment.