Calculate LoRaWAN airtime and Class A receive-window budgets

Calculate how spreading factor, payload size and report interval affect modeled airtime and Class A receive-window timing.

Use the LoRaWAN operations chapter to prepare and review evidence for device-class timing and slow-data-rate payload decisions., your practice guide

Use the LoRaWAN operations chapter to prepare and review evidence for device-class timing and slow-data-rate payload decisions.
Predict the reading, then compare it with the measurement.

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Python · no install

Calculate how spreading factor, payload size and report interval affect modeled airtime and Class A receive-window timing.

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Version tested: Python 3.12.7 / Pyodide 0.27.6 in JupyterLite 0.6.4; Chromium 151.0.7922.34; captureSource playwright:jupyterlite. Date: 2026-10-08.

Open the notebook in your browser and run each Python cell; no install or account is needed.

Three ways to run: use JupyterLite here with no install; run main.py locally from the downloadable lab folder; or open the same notebook in Google Colab.

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Steps

Screens captured against Python 3 in your browser (JupyterLite) Python 3.12.7 / Pyodide 0.27.6 in JupyterLite 0.6.4; Chromium 151.0.7922.34; captureSource playwright:jupyterlite on 2026-10-08; the tool may have moved on — the text steps are the contract.

  1. Step 1

    Do
    In the notebook editor, run the Step 1 notebook cell. Freeze the hypothetical LoRa radio inputs.
    You will see
    The run prints 21 PHYPayload bytes, 125000 Hz bandwidth, coding rate 4/5 and eight preamble symbols.
    Why it matters
    A timing result needs its framing assumptions.

  2. Step 2

    Do
    In the notebook editor, run the Step 2 notebook cell. Compute airtime at SF7, SF9 and SF12.
    You will see
    The SF7 and SF12 airtimes are 56.576 ms and 1482.752 ms for 21 bytes.
    Why it matters
    A slower data rate can change channel occupancy sharply.

  3. Step 3

    Do
    In the notebook editor, run the Step 3 notebook cell. Change the payload size.
    You will see
    At 35 bytes, SF7 uses 77.056 ms and SF12 uses 1810.432 ms.
    Why it matters
    Payload growth must be reviewed at the slowest allowed setting.

  4. Step 4

    Do
    In the notebook editor, run the Step 4 notebook cell. Place RX1 and RX2 after the uplink.
    You will see
    The modeled SF12 uplink ends at 1.483 s; RX1 opens at 2.483 s and RX2 at 3.483 s.
    Why it matters
    Class A downlink timing follows the uplink end.

  5. Step 5

    Do
    In the notebook editor, run the Step 5 notebook cell. Compare three report intervals against a hypothetical 1% budget.
    You will see
    At 60 s, SF12 airtime share is 2.471% and exceeds the assumed budget; at 300 s it is 0.494%.
    Why it matters
    The interval can determine whether a chosen radio setting is feasible.

  6. Step 6

    Do
    In the notebook editor, run the Step 6 notebook cell. Record a bounded Class A design decision.
    You will see
    The run recommends lengthening the interval when the hypothetical 1% budget is exceeded.
    Why it matters
    A model cannot replace regional rule, network or field checks.

Chapter checks

These questions refer to the chapter’s examples. Use the return links to review their answers.

  1. A LoRaWAN deployment has missing readings after devices move from the lab bench to final placement. Which first review step keeps the diagnosis bounded?

    Return to the chapter’s knowledge check

  2. A payload works near the gateway but fails after final installation when the network selects a slower data rate. What is the best review response?

    Return to the chapter’s knowledge check

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