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If you’re just beginning your smart home journey and unsure which technology stack to choose, then you’re in the right place! In this post, I deep dive into two leading smart home communication protocols: Zigbee and Thread. 

I discuss their key features, differences, and how they fit into the new, interoperable Matter standard. 

By the end of this post, you should have a clear understanding of these technologies and be better equipped to make an informed decision on which protocol is the best fit for your smart home.

Before I begin, here’s a quick intro to both technologies.

What is Zigbee?

Zigbee is a low-power, wireless mesh networking protocol designed for IoT devices, enabling smart home automation, energy management, and industrial applications.

What is Thread?

Thread is an IPv6-based, low-power, secure, and scalable wireless mesh networking protocol for IoT devices, designed to seamlessly integrate with other IP networks and provide reliable communication in smart home and automation applications.

What do Zigbee and Thread have in common?

As you can see from both descriptions, these technologies have a lot in common.

Both Zigbee and Thread operate in the globally available 2.4 GHz frequency band, which offers a good balance between range and bandwidth for IoT devices.

Zigbee and Thread both support mesh networking, allowing devices to connect and communicate with one another in a decentralized manner. This feature increases network coverage, resilience, and reliability, as devices can route messages through multiple paths and bypass potential points of failure.

Both protocols prioritize low-power consumption, which is essential for battery-operated devices in smart home and IoT environments. This focus on energy efficiency enables devices using either protocol to have extended battery life and reduced overall energy usage.

Zigbee and Thread both utilize the IEEE 802.15.4 standard as their underlying wireless communication technology. This standard is specifically designed for low-power, low-data-rate, and short-range communication, making it well-suited for smart home and IoT applications. 

What are the key differences between Zigbee and Thread?

The primary difference between Zigbee and Thread is that Zigbee is a complete IoT solution with its own application layer and network layer.

Thread, on the other hand, is solely an IPv6-based networking protocol that can work with various application layers, including Matter, for device communications.

Let’s get into the key differences.

Latency

Thread generally has lower latency compared to Zigbee, thanks to its more efficient routing mechanism.

In other words, it's faster which is an advantage over Zigbee. When you turn on a smart light switch in a smartphone app, you want to see that light come on as fast as possible!

Zigbee networks may have slightly higher latency, which can cause minor delays when controlling devices, especially in larger or more congested networks.

Security

Thread features built-in end-to-end security with AES-CCM and mandatory device commissioning, while Zigbee's security is based on AES-128 encryption with optional device commissioning.

Thread's built-in end-to-end security and mandatory commissioning process help ensure that devices joining the network are authenticated and secure, reducing the risk of unauthorized access. Zigbee, with its optional commissioning, may present varying levels of security depending on the implementation, which could be a concern for privacy-conscious end users.

Market Adoption

Zigbee has been around for a much longer time and has a larger market presence, with a wider range of compatible devices and solutions available. 

As a newer protocol, there are much fewer Thread-compatible devices on the market compared to Zigbee. However, Thread's growing adoption, particularly in the Apple HomeKit ecosystem and the Matter protocol, is rapidly closing this gap.

Device Roles & Self-Healing

Zigbee and Thread both have distinct device roles. Zigbee utilizes the Coordinator, Router, and End Device roles, while Thread employs Leader, Router, and End Device roles. 

The key difference lies in the Leader role in Thread networks, which dynamically manages the network and can be reassigned among Router devices, providing increased resilience and stability. 

Zigbee relies on a single Coordinator, which, if it goes offline, may cause the network to become unstable. 

Both Zigbee and Thread have self-healing capabilities, where routers can re-route messages around failed nodes. However, being able to dynamically re-assign the Thread Leader role, give Thread the edge over Zigbee's more rigid Coordinator-based approach.

Scalability

In terms of the number of devices that can be theoretically supported, Zigbee has an advantage over Thread. Zigbee networks can theoretically support up to 65,000 devices, while Thread networks are limited to 250 devices per border router. 

However, in a residential IoT / smart home network, the number of devices would be in the tens or hundreds. In this case, Thread's IPv6-based addressing and more efficient routing mechanism may provide better scalability in terms of network performance and resilience.

Network, Application Layers & Addressing

Zigbee uses a custom network and application layer, while Thread employs an IPv6-based network layer, enabling seamless integration with other IP-based systems, like Wi-Fi networks and internet services.

Zigbee's custom layers use short addresses that generally require additional translation or gateways to bridge communication with other protocols, potentially adding complexity to a smart home setup.

Ecosystem support

Thread is natively supported by Apple HomeKit and is a core component of the Matter protocol, which means in the future it is more likely to be compatible with a wider range of devices and ecosystems.

Zigbee often requires a gateway or bridge for integration with popular IoT platforms (or you would need to use a smart home platform that has a Zigbee radio built-in like Hubitat or the Amazon Echo 4).

Network Topology

Zigbee supports three types of network topologies: star, tree, and mesh, providing more versatility in network design, whereas Thread focuses solely on mesh topology. 

The star and tree topologies in Zigbee can be advantageous in certain use cases or environments where a centralized network structure is preferred or required. 

However, the mesh topology, used by both Zigbee and Thread, is the most common and practical choice for IoT and smart home networks due to its flexibility, reliability, and self-healing capabilities. 

Thread networks have an advantage in terms of routing efficiency and network resilience, thanks to the Mesh Link Establishment (MLE) protocol, which enables dynamic, secure, and bidirectional communication between neighboring devices. 

Zigbee networks use the Ad-hoc On-demand Distance Vector (AODV) routing protocol, which discovers and maintains routes only as long as they are in use.

Interoperability

Zigbee's multiple profiles (including custom manufacturer profiles), frequency bands, and application layers can sometimes lead to compatibility issues, where devices from different manufacturers or with different profiles might not communicate seamlessly with each other. 

This fragmentation can limit the ability to create a fully integrated smart home ecosystem using Zigbee devices. 

On the other hand, Thread networks have a standardized application layer (especially with the introduction of Matter) and a consistent IP-based communication protocol, ensuring that all Thread devices can work together smoothly, regardless of the manufacturer. 

Frequency Bands

Thread operates exclusively in the 2.4 GHz frequency band, while Zigbee can operate in the 2.4 GHz band globally and in the 868 MHz and 915 MHz bands regionally.

The 2.4 GHz band in both Zigbee and Thread consists of 16 channels (numbered 11 through 26) with 5 MHz bandwidth and 2 MHz separation. 

There are advantages to Zigbee's multiple frequency bands such as less congestion in the lower bands and avoiding interference with other devices in specific regions. 

The disadvantage of this is ZigBee devices operating on different frequency bands cannot directly communicate with each other on the same network.

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Thread and Zigbee in the context of Matter

Matter is an open-source, royalty-free connectivity standard developed by the Connectivity Standards Alliance (formerly known as the Zigbee Alliance), which aims to simplify and improve the interoperability of smart devices across various ecosystems. 

Matter is IP-Based, utilizing both Wi-Fi and Thread as its network protocols. The Zigbee networking layer is not being used, as it runs on its own custom technology.

So for Zigbee to become interoperable with Thread and Matter, there are two approaches.

Firmware updates for existing Zigbee devices

Some existing Zigbee devices could potentially receive firmware updates that add Matter support, allowing them to operate with both the Zigbee and Matter application layers. 

This dual compatibility would enable these devices to communicate with both Zigbee-only and Matter-compliant devices in a smart home.

However, this would depend on the device's hardware capabilities, memory, and processing power.

Bridging devices

A bridging device that supports both Zigbee and Thread / Matter can be used to enable communication between Zigbee devices and Thread-based Matter devices. 

The bridging device would translate and route messages between the Zigbee and Thread / Matter networks, allowing for seamless communication between devices that use different protocols.

As of the time of writing, there are no Zigbee Matter bridges available. However Homey Pro, Philips Hue Bridge and SwitchBot Hub may soon get upgrades to become bridges. While Samsung SmartThings have confirmed their hub will not act as a bridge in the short term.

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What is the difference between a Thread Border Router vs a Zigbee Hub or Gateway?

A Thread Border Router and a Zigbee Hub/Gateway serve as the primary points of connection and communication between their respective networks and external networks, like the internet. They have some similarities but also differ in functionality and network management.

Thread Border Router

The Thread Border Router connects a Thread network to external networks (e.g., Wi-Fi, Ethernet) and provides access to cloud services, remote management, and external control interfaces like mobile apps.

It translates and routes messages between Thread devices and devices on external networks, leveraging IPv6-based addressing. 

It doesn't dictate the network topology or manage the network configuration, as that responsibility lies with the Leader device in a Thread network. 

Multiple Thread Border Routers can be present in a single Thread network, providing redundancy and ensuring network connectivity even if one border router fails.

Zigbee Hub/Gateway

A Zigbee Hub (or Gateway) connects a Zigbee network to external networks, providing access to cloud services, remote management, and control interfaces like mobile apps.

It translates and routes messages between Zigbee devices and devices on external networks, using Zigbee's application layer protocols.

In a Zigbee network, the Coordinator device (often integrated into the Zigbee Hub/Gateway) is responsible for starting the network, assigning addresses, and maintaining overall network stability.

Generally, a single Zigbee Hub/Gateway is present in a Zigbee network, which can be a single point of failure if the hub goes offline.

Can a Thread Device communicate with a Zigbee Device?

If you want to connect a local Thread device to a local Zigbee device, the communication would typically need to be relayed through both a Thread Border Router and a Zigbee hub or gateway.

  1. The Thread device would send a message to the Thread Border Router, via the Thread mesh network.
  2. The Thread Border Router would then forward the message to the Zigbee hub on the local network.
  3. The Zigbee hub would then receive the message from the IP-based network and translate it into a format that the Zigbee device can understand.
  4. The Zigbee hub then communicates the message to the Zigbee device through the Zigbee mesh network.

Is Thread going to replace ZigBee?

While it's difficult to predict the future, I think it's highly unlikely that Thread will completely replace Zigbee in the short to medium term. 

Both Thread and Zigbee have their own strengths and are suited for different applications and use cases. 

According to a report from CSA, over 500 million Zigbee chips had been sold up to 2018 with that number expected to rise to just shy of 4 billion this year. As of 2021, there were over 4,000 certified Zigbee products and 1,000 Zigbee 3.0 devices. So Zigbee is clearly a very popular technology.

Thread, on the other hand, is a newcomer to the industry with a small number of certified devices available. However, the emergence of the Matter protocol is almost certainly going to lead to the rapid adoption of Thread and potentially impact the market share of Zigbee.

Zigbee vs Thread Comparison Table

Feature/AspectThreadZigbee
Networking ProtocolIEEE 802.15.4IEEE 802.15.4
Mesh NetworkingYesYes
Network TopologyMeshMesh, Star, Tree
Frequency Band2.4 GHz2.4 GHz (Global), 868/915 MHz (Regional)
Data Rate250 kbps250 kbps (2.4 GHz), 20-40 kbps (868/915 MHz)
Network SizeScalable up to hundreds of nodesUp to 65,000 nodes
IPv6 SupportYesNo
SecurityAES-CCM with 128-bit keys, secure commissioningAES-128 encryption, network key for association
Device RolesLeader, Router, End Device, Sleepy End Device, Border RouterCoordinator, Router, End Device
CommissioningSecure, user-friendly process with Commissioner roleAssociation process managed by Coordinator or Router
Application LayerCan use Matter or other custom application layersZigbee Application Layer. Can support other layers including Matter.
InteroperabilityHigh (when used with Matter)High (when used with Matter)
Power ConsumptionOptimized for low-power devicesOptimized for low-power devices
Self-HealingYesYes
RoutingRouters handle routing and forwarding messagesRouters and Coordinator handle routing and forwarding messages
Communication Range10-100 meters per hop (depending on environment and device)10-100 meters per hop (depending on environment and device)
LatencyLowLow to moderate
Bandwidth UtilizationEfficient use of bandwidthEfficient use of bandwidth
Network ManagementBuilt-in network management and diagnosticsBuilt-in network management and diagnostics
External Network AccessThread Border Router for connecting to other networks (e.g., Wi-Fi)Zigbee gateway/hub for connecting to other networks (e.g., Wi-Fi)

How do Zigbee and Thread compare with other IoT protocols?

Zigbee and Thread are both designed for low-power, low-data-rate IoT applications and offer mesh networking capabilities, which enable greater coverage and resilience. 

Wi-Fi, on the other hand, is better suited for high data rates (such as video transmission) and more power-hungry applications but lacks native mesh networking support. 

Bluetooth is suitable for short-range, low-power communication and has added mesh capabilities in Bluetooth 5.0, while LoRaWAN is designed for long-range, low-power communication in wide-area networks but does not support mesh networking.

About the Thread Group

The Thread Group is an organization that consists of several member companies working together to develop, promote, and certify the Thread networking protocol for IoT devices. Members of the Thread Group include leading technology companies, IoT device manufacturers, and other industry stakeholders.

About the Connectivity Standards Alliance (Previously the Zigbee Alliance)

The Connectivity Standards Alliance (CSA), is an organization responsible for developing and promoting Zigbee technology, among other IoT standards. Established in 2002, the alliance consists of a group of companies, including major manufacturers, technology developers, and service providers, that collaborate to create and maintain the Zigbee standard for low-power, wireless IoT communication.

In addition to Zigbee, the CSA also drives the development and adoption of other IoT standards such as Matter.

Citations

https://www.threadgroup.org/

https://csa-iot.org/all-solutions/zigbee/

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