AS923
Understanding AS923 LoRaWAN Frequency Plan
LoRaWAN enables long-range, low-power IoT communication — a sensor on a farm can send data to a gateway 10 km away on a single battery charge lasting years. But the radio frequencies and power levels it can use vary by country. AS923 is the frequency plan that harmonizes LoRaWAN operation across the diverse regulatory landscape of Asia-Pacific.
Regional Frequency Variations
Different countries within the AS923 region have different spectrum allocations and regulatory constraints:
- AS923-1 (920.9–923.3 MHz): Used in Japan, Singapore, and several Southeast Asian countries.
- AS923-2 (921.4–922.8 MHz): Used in countries with slightly different ISM band allocations.
- AS923-3/4: Additional subgroups for countries with unique regulatory requirements.
Technical Parameters
AS923 defines spreading factors from SF7 (highest data rate, shortest range) to SF12 (lowest data rate, longest range), with maximum payload sizes ranging from 242 bytes (SF7) to 51 bytes (SF12). Maximum transmit power varies by country, from 14 dBm to 27 dBm depending on local regulations. Japan requires Listen-Before-Talk, while other countries use duty cycle limitations.
Key Equations
AS923 is a regional frequency plan specification for LoRaWAN (Long Range Wide Area Network) networks operating in the 915–928 MHz Industrial, Scientific, and Medical (ISM)...
Key specifications:
928 MHz | 10 km | 923.3 MHz | 922.8 MHz | 242 bytes | 51 bytes
Throughput: R = Nlayers×B×ηSE×(1−OH)
Comparison
| Aspect | AS923 Spec | Typical Range | Impact | Design Note |
|---|---|---|---|---|
| Primary function | AS923 is subdivided into subgroups (AS92... | Application-dep. | Critical | Verify in sim |
| Operating range | Understanding AS923 LoRaWAN Frequency Pl... | Application-dep. | Critical | Verify in sim |
| Performance | But the radio frequencies and power leve... | Application-dep. | Critical | Verify in sim |
| Integration | AS923 is the frequency plan that harmoni... | Application-dep. | Critical | Verify in sim |
| Trade-off | AS923-2 (921.4–922.8 MHz): Used in count... | Application-dep. | Critical | Verify in sim |
Frequently Asked Questions
How does AS923 differ from US902-928?
US902-928 (the Americas frequency plan) uses a wider 902–928 MHz band with 64 uplink channels and 8 downlink channels, supporting higher aggregate capacity. AS923 uses a narrower portion of the 915–928 MHz band with fewer channels, reflecting the more restrictive spectrum allocations in Asia-Pacific. The frequency plans are not interchangeable — a device configured for US902 will not function on an AS923 network.
What is Listen-Before-Talk?
Listen-Before-Talk (LBT) is a spectrum access mechanism required in Japan (under ARIB STD-T108) where a device must listen to the channel for activity before transmitting. If the channel is occupied, the device must wait. This differs from duty-cycle-based access (used in Europe and most AS923 countries), where devices simply limit their transmission time to a defined percentage regardless of channel activity. LBT is more spectrally efficient in dense deployments but adds complexity and latency to device firmware.
Can a single device support multiple AS923 subgroups?
Yes, with proper firmware configuration. The LoRa radio hardware operates across the full 915–928 MHz ISM band. The frequency plan is implemented in software — the device firmware selects the specific channel frequencies, power levels, and access mechanisms based on its configured region. A single hardware SKU can support all AS923 subgroups through firmware configuration, simplifying global product deployment for IoT manufacturers.