Solutions for Dual PAN IEEE 802.15.4 Use Cases

With the introduction of Matter, the need for smart home devices to support multiple networks has become more important. Matter, a unified application layer that delivers interoperability across brands and ecosystems, was purposefully designed to enable secure interoperability by building the foundation on the Internet Protocol and to coexist with the millions of smart home devices already in homes today.

A typical smart home network will most likely consist of multiple technologies, as seen in the figure below. For example, there could be battery-powered or power sensitive devices using Zigbee or Matter over Thread and more advanced or always-powered devices using Matter over Wi-Fi.

For a better viewing experience, download the block diagram.

In this network topology, there is at least one central device ensuring coexistence of the ecosystems by managing and interconnecting these devices. A gateway/hub is typically the optimal device to do these tasks and must embed multiple roles for the smart home local network: Zigbee Coordinator, Thread Border Router, Matter Controller and a Zigbee to Matter bridge. The Dual PAN use cases include:

• Migrating to or adding support for Matter while continuing to support Zigbee-based devices
• Building a gateway/hub that is capable of managing multiple wireless protocols, e.g., gateway/hub that runs Matter, Thread Border Router and Zigbee

Dual PAN Design Considerations

Dual PAN is a feature that allows devices to participate in two IEEE 802.15.4 personal networks at the same time. Being able to do this enables interoperability of Matter with existing market devices and more intelligent automation, e.g., automatically dimming lights and turning off or pausing appliances during a peak demand of energy.

Determining the most effective way to implement Dual PAN for a given use case entails assessing and prioritizing the requirements and priorities. These include:

• Quality-of-service / network performance
• Role of devices on each network
• Ownership and control of each network
• System cost

NXP performed extensive testing for two architectures to provide context and data to facilitate design decisions. The two architectures evaluated are shown in the figure below. Note that RF Channels A and B in the figure could be the same or different depending on the ecosystem configuration and constraints.

For a better viewing experience, download the block diagram.

With these architectures defined, NXP created two configurations on which to perform the testing.

A comprehensive application note is available to provide details on the test setup, the tests run, the data collected and the takeaways.

Dual PAN Implementations and Test Data

As mentioned earlier, each device's role in the network contributes to the Dual PAN results. The devices can be sleepy or mains-powered (where the radio is always listening) and networks can use the same or different RF channels. Dual PAN use cases typically involve two routing (always on) devices.

For a better viewing experience, download the block diagram.

• Concurrent receiving/sending from and to two different RF channels is physically possible with a single radio.
  • Radio must switch between the RF channels to perform the communication
  • When tuned on one channel, the other channel cannot receive or send
  • This can be effective in use cases where ‘'always receive on' is not mandatory on both channels, e.g., a sleepy device is on one network
• Concurrent receiving/sending from and to the same RF channel is easier to achieve with a single radio.
  • Radio stays tuned and the handling of two separate PAN IDs is determined by its capabilities
  • NXP's solutions used for this testing both provide hardware features to enable multiple PAN ID MAC filtering without software intervention.
    • MCX W71: Fast switch RF channels, multiple PAN ID filtering and MAC acks
    • IW612: Separate receive paths for Bluetooth LE and 15.4 Multiple PAN ID filtering and MAC acks

Dual PAN Implementation Takeaways

Dual PAN can be architected as a single or dual radio solution depending on the intended use case and priority of the requirements. These requirements include quality-of-service (network performance), role of device(s) on each network, ownership and control of each network and system cost. Overall, the data demonstrates that there is a significant improvement for error packet loss and latency observed in a dual radio architecture, especially when there is a higher payload size and increased RF activity.

• Single Radio Solution: Lowest Cost, Least Flexible
  • Relies on multiplexing the radio between the two PANs, using the same channel or different channels
    • The probability of dropped packets on a single channel is low due to the way 802.15.4 does channel assessments before transmitting
    • A single channel can become crowded in a dense environment when all devices use the same channel
  • If there is control of only one network and the second network is owned by another entity (e.g., smart home platforms), there is a risk of the other network changing its channel (more likely with Matter)
    • Lower flexibility of RF channel selection due to limitations on the PAN context switching
• Dual Radio Solution: Optimal Performance, Most Flexible
  • Device can receive packets 100% of the time with dedicated receive for each RF channel
    • No dropped packets
  • Offers optimal performance for both single channel and different channels scenarios, proving more flexibility with an increased cost

NXP's comprehensive portfolio provides solutions for the various Dual PAN use cases which have different requirements for processing and networking. The table below provides a snapshot of NXP's system-level solutions per application and use case.

Enabling the Autonomous Home

As Matter adoption continues to grow, device makers building smart home devices must enable the transformation of the smart home to the intelligent and autonomous home while also ensuring an ease-of-use experience for consumers. This means supporting existing technologies, especially devices already in millions of homes today. NXP understands the complexities involved in creating this seamless experience and remains committed to providing tailored solutions that address the key technology requirements outlined in this article and the associated application note.

Authors