The iSIM takes the next step after the eSIM. Instead of a separate chip, the SIM function runs in a tamper-resistant area inside the modem’s system on chip, certified to the same security standards as a discrete SIM. The device gains the same remote provisioning features as an eSIM, so profiles can still be downloaded and switched over the air.
The point is cost, space and power. Removing a component and its footprint matters in small, cheap devices such as NB-IoT sensors made in the millions, and integrating the SIM into the SoC shaves a little current from the power budget. The trade-offs are newer and less uniform support across modem vendors and operators, and a tighter coupling between SIM and chip supply chains, since the SIM software must be loaded during chip or module manufacture.
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