Sovereign Airwaves · the physical layer

The hardware stack

Five node roles, one radio family — Semtech SX1262 on 920–925 MHz. Every device sits inside the NBTC envelope: transmit power + antenna gain capped at ≤ 50 mW e.i.r.p.

ชั้นฮาร์ดแวร์ — วิทยุ LoRa SX1262 ย่าน 920–925 MHz · กำลังส่ง ≤ 50 mW ตามข้อกำหนด กสทช.

SX1262

one radio family across every node

920–925

MHz · Thailand LoRa (use US915 hardware)

≤ 50 mW

e.i.r.p. · NBTC-legal, enforced in software

5 roles

gateway · relay · merchant · driver · tag

Five node roles

Gateway — Intel N100 hub with LoRa concentrator

Gateway hub

Intel N100 + concentrator

x86 host: Go gateway, offline routing, dispatch. Core 0 ingest · Cores 1–3 route.

≈ 50 mW e.i.r.p. · 8 m mast

Mesh relay

Radxa Zero 3W + SX1262

The real edge_node firmware target — Rust driving the radio over SPI.

≈ 40 mW e.i.r.p. · 4 m mast

Merchant node

Heltec WiFi LoRa 32 V3

ESP32-S3 + SX1262 at the counter — carries the offline POS uplink.

≈ 25 mW e.i.r.p. · indoor

Driver companion

LilyGO T-Beam + GPS

Mobile dispatch node — onboard GNSS for the rider and delivery breadcrumbs.

≈ 25 mW e.i.r.p. · mobile

IoT tracker

SX1262 asset tag

Low-power telemetry & presence — GPS-free traffic calibration from the mesh.

≈ 10 mW e.i.r.p. · low duty

Images are schematic illustrations — the RF parameters (TX dBm + antenna dBi, mast height) are the exact values the coverage planner models against the legal cap. Drop real product photos into hardware/hw/ to replace them.

Two compute hosts, two jobs

🖧 Gateway — Intel N100 (x86)

Runs the Go gateway: Ed25519 auth, Postgres persistence, offline OpenStreetMap/Valhalla routing, the Hungarian dispatch solver, and Prometheus metrics. Fanless, ~6 W. Its four cores are why the design pins Core 0 to ingestion and Cores 1–3 to routing.

📟 edge_node — Radxa Zero 3W (SBC)

The real firmware target: Rust + rppal driving the SX1262 over SPI. Linux on the device; a mock_spi fallback lets the same code build and test off-Linux while the radio driver (the one hardware-blocked seam) is finished.

Both hosts are low-power, fanless, and field-deployable — the gateway is the concentrator hub; every relay is a Radxa running the same edge firmware as a future merchant/driver node.

Band and compliance — get it right at purchase

ตรวจสอบตามประกาศ กสทช. (มท. 1033-2560) — ย่าน US915, กำลังส่ง ≤ 50 mW, รอบการส่ง ≤ 1%/ชม.

Band

Thailand LoRa is 920–925 MHz → buy US915 (902–928) hardware and presets. EU868 does not cover our band — it will not work. Get this right in every tool and every purchase.

Power

≤ 50 mW e.i.r.p. — NBTC TS 1033-2560 SDoC self-declaration tier. Enforced in software: TX dBm + antenna dBi is capped at 17 dBm e.i.r.p. on every device.

Duty cycle

≤ 1%/hr cumulative TX per device; the ≥20-channel FHSS path (≤ 0.4 s dwell/channel) allows 10%/hr. No transmit loop faster than the per-SF legal frame budget.

Buy cheap beats rent — or wait

Commercial LoRa rental barely exists, and at these prices it makes no sense: a 3–5 node bench is ~$75–150 total, less than any plausible monthly rental — and you keep it.
A ~$100 board bench validates in days what waiting for a custom build cannot: real 920–925 MHz RF behaviour, mesh topology, SF / packet-loss in actual Udon Thani geography, and gateway-over-a-real-radio integration.
Two buys answer two questions: Heltec / T-Beam (ESP32/nRF running Meshtastic) validate RF + mesh + gateway; a Radxa Zero 3W + SX1262 module exercises the exact edge_node Rust driver. Both are cheap.

~$150

RF-validation bench (boards + target SBC)

days

to validate real RF vs planner predictions

buy > rent > wait

rental is worse than owning at this price

Request for quotation — one pilot cell

Qty	Item	Key spec	Indicative unit (USD)	Ext.
1	Gateway — Intel N100 + LoRa concentrator + outdoor antenna	x86 host · US915 · ≤ 50 mW	quote requested	~$250–360
2	Mesh relay — Radxa Zero 3W + SX1262 module + antenna	Rust `edge_node` target	$25–55	$50–110
5	Merchant node — Heltec WiFi LoRa 32 V3	ESP32-S3 + SX1262	$20–25	$100–125
3	Driver companion — LilyGO T-Beam + GPS	SX1262 + GNSS, mobile	$30–45	$90–135
5	IoT tag — bare SX1262 asset tag	low-power telemetry	$5–20	$25–100
lot	Antennas · cabling · outdoor enclosures (US915, IP-rated)	weatherproofing	quote requested	~$60–120
Indicative pilot-cell total				≈ $575–950

Band — non-negotiable

920–925 MHz → quote US915 (902–928) variants. EU868 does not cover our band and will not be accepted.

Compliance

Capable of ≤ 50 mW e.i.r.p. — NBTC TS 1033-2560 SDoC tier. Please state antenna-gain options.

Requested from supplier

Unit price at qty · lead time · US915 confirmation · ship to Udon Thani, TH.

Prices indicative (internal RF reference, 2026-07) — verify at purchase. The N100 gateway and weatherproofing are marked quote requested. This cell is the Pilot step: it follows the ~$150 RF-validation bench and proves real 920–925 MHz behaviour against the planner before the 100-node scale-up.

The radio is the last mile

Everything above the radio is built and tested today — authenticated gateway, offline POS, the full dispatch pipeline, offline routing, ~290 automated tests. The SX1262 TX/RX is the one mocked seam.
The coverage planner already models these exact devices against the legal cap — place them on the real Udon Thani map and watch coverage, duty cycle, and dispatch update live.
Bench → pilot cell (the RFQ above) → 100-node scale. A sub-$150 buy confirms the software fits real radios; the pilot cell stands up one city-center mesh; scale is Phase 2.

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