Unlocking Smarter Wi-SUN Networks with Mode Switch and Concurrent Detection

Wi-SUN delivers resilient, long-range, low-power mesh networking for large-scale field-area networks—spanning utilities (electric, gas, water), industrial campuses, transportation corridors, logistics hubs, agriculture, and municipalities. These environments demand reliability, flexibility, and efficiency under changing RF conditions and mixed device capabilities. Fixed-PHY sub-GHz designs trap you in a zero-sum game: range, throughput, or power. Worse, they can’t adapt when conditions change.

Wi-SUN FAN 1.1 addresses these challenges with adaptive PHY capabilities. Silicon Labs extends this further with two complementary approaches: Mode Switch , the standards-based method defined in Wi-SUN FAN 1.1, and Concurrent Detection, a Silicon Labs innovation. Together, they give developers the flexibility to balance performance, coexistence, and interoperability in large-scale Wi-SUN deployments.

Wi-SUN Mode Switch: Standards-Based PHY Agility

Mode Switch uses FSK as the base PHY for coverage. When higher data rates are needed, a Mode Switch PPDU signals devices to temporarily change PHY (e.g., FSK to OFDM). After transmission, nodes revert back to FSK. This ensures the best PHY and data rate for channel conditions, reducing errors and retransmissions. It adapts to each use case - (OFDM for OTAs, FSK for routine traffic) - and aligns with device capabilities so nodes only use PHY modes they support.

Because it is defined in Wi-SUN FAN 1.1, Mode Switch delivers full multi-vendor interoperability. The tradeoff is signaling overhead and potential delays due to clear channel assessment (CCA) (~160 µs) and settling times (0.5–1.5 ms). In very fast-CCA environments, coexistence performance may degrade.

Silicon Labs Wi-SUN Concurrent Detection

Concurrent Detection avoids signaling altogether. Devices listen to FSK and OFDM in parallel, locking to the first valid preamble. This makes it faster than Mode Switch with no settling time overhead. It improves coexistence in fast -CCA networks such as 802.11ah and supports hybrid networks that use FSK for robust links and OFDM for high-speed transfers.

It also boosts throughput without consuming airtime on signaling packets. The tradeoff is that it can only receive one payload at a time, and today it is limited to predefined PHY pairs like FSK and OFDM, though more can be added based on customer needs.

Wi-SUN Adaptive PHY: Two Paths, One Goal

Mode Switch and Concurrent Detection complement each other. Mode Switch ensures standards compliance and interoperability across multi-vendor fleets, while Concurrent Detection adds speed and efficiency in dense RF environments. Developers can deploy Mode Switch as the baseline and enable Concurrent Detection on endpoints that support it with- no application changes required.

As Wi-SUN networks scale, adaptive PHY solves the tradeoffs between range, throughput, and power. Mode Switch provides standards-based PHY agility and interoperability, while Concurrent Detection accelerates performance and coexistence without signaling overhead. Together, they enable developers to build future-ready Wi-SUN networks that are flexible, reliable, and efficient at scale.

Request a Wi-SUN development kit and see Adaptive PHY in action.