SoftSIM moves the SIM application into the device: no plastic cards, instant provisioning, smaller BOMs and measurable battery wins. This webinar walks you through Nordic’s nRF9151 SiP, the exact firmware and SDK prerequisites, secure storage and KMU patterns, Onomondo’s provisioning tooling, and AirBolt’s real-world production results — all the practical detail you need to pilot SoftSIM and avoid the hidden connectivity costs that quietly destroy margins.
Watch the full webinar here or read the summary below.
nRF9151: a secure SiP built for SoftSIM
Nordic’s nRF9151 (part of the nRF91 family) is a compact System-in-Package that combines a cellular modem with a Cortex-M33 application core, Arm TrustZone and CryptoCell. By integrating modem, application core, PMIC and RF front-end, Nordic removes the need for an external MCU or separate secure element — cutting BOM, board space and power. The nRF Connect SDK (Zephyr-based), VS Code tooling and Nordic’s developer resources make prototyping and debugging fast. For SoftSIM, the device’s KMU and TrustZone provide a secure host for the SIM application and key storage inside the SiP.
Key takeaway: nRF9151 is purpose-built for SoftSIM: integrated modem and secure app core for lower BOM, smaller devices and simpler integration.
Why SoftSIM: the commercial and engineering case
SoftSIM is the SIM application as code running in a secure host — not a physical card. The business wins are immediate: lower BOM, no customs or shipment delays, instant provisioning and smaller devices.
Engineering wins are equally practical: better power profiles because the SIM lives on the low-power application core, and simpler supply chains. Security is achieved with TrustZone, KMU and PSA crypto APIs — so SoftSIM can be certifiable when implemented correctly.
Nordic and Onomondo stress that SoftSIM is a different security posture, not a weaker one — follow secure storage and provisioning rules and you get both security and operational benefits.
Key takeaway: SoftSIM reduces cost and complexity while improving battery and time-to-market — if you design for secure storage and provisioning.
How SoftSIM runs on nRF91: the integration pattern
SoftSIM requires modem firmware that supports an internal APDU data path — modem firmware v1.3.4+ enables this on nRF9151. The modem exposes a request/response handler so the application core can serve SIM APDUs internally (no external IO).
Onomondo supplies a SoftSIM library and a GitHub integration sample that plugs into the Nordic stack; prerequisites include nRF Connect SDK ≥ 2.5 and the nRF9151 SDK. The provisioning payload (“SoftSIM profile”) is compact (commonly <350 bytes). Onomondo supports profile generation via API or an open-source Rust CLI to automate production workflows.
Key takeaway: SoftSIM = modem firmware and in-SiP APDU path + Onomondo SDK/sample — meet the firmware & SDK prerequisites for a smooth integration.
Engineering rules: storage, keys, provisioning and flashing
Engineering details matter: allocate a small flash partition for the SoftSIM filesystem (example: 32KB allocated, ~8KB populated), enable the caching layer to reduce flash wear, and store secrets inside KMU/TrustZone. KMU slots may be consumable — avoid burning them in tests.
The demo shows a VS Code flow to build, flash and paste a SoftSIM profile over serial; for production, automate provisioning using Onomondo APIs or the CLI and a secure CI/CD pipeline. In short: make secure storage and provisioning a first-class engineering task.
Key takeaway: Plan storage, KMU usage and secure provisioning from day one — the right layout and tooling prevent costly mistakes.
AirBolt: production outcomes and commercial impact
AirBolt replaced physical SIMs with SoftSIM on Nordic hardware and Onomondo provisioning and saw immediate commercial benefits: reduced BOM and environmental waste, no eSIM customs delays, faster time-to-market, and improved power (MQTT keep-alive extended from ~5–7 minutes to ~19 minutes).
Engineers valued the open-source libraries and CLI that enabled production-grade profile generation and provisioning. AirBolt’s case proves SoftSIM is not a lab novelty — it delivers measurable ROI in production.
Key takeaway: SoftSIM delivered real product, production and power improvements for AirBolt — proven ROI in the field.
Closing summary
SoftSIM on the nRF91 series (nRF9151) is a secure, production-ready way to remove the physical SIM: faster provisioning, smaller BOMs, sustainable design and measurable battery improvements.
The engineering path is clear: meet firmware (v1.3.4+) and SDK (nRF Connect SDK ≥ 2.5) prerequisites, plan flash/KMU layout, use Nordic dev tools with Onomondo provisioning APIs, and pilot thoroughly.
AirBolt’s outcome proves the approach works in production — engineering wins and business returns together.
SoftSIM on nRF91 — build smaller, ship faster and save power in production: meet the firmware, secure the keys and pilot it.