IOT GLOSSARY

A practical dictionary of IoT and M2M connectivity

The terms you will run into most often in IoT projects, explained in plain language. From APN to NB-IoT, with eSIM, OCPP and MQTT along the way.

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In-depth definitions

These entries have their own page with examples, FAQs and related links.

What is eUICC

An eUICC (embedded Universal Integrated Circuit Card) is a programmable SIM chip that can hold several carrier profiles and switch between them over the air. It is the GSMA standard underpinning every modern eSIM, in phones, vehicles, and IoT devices.

What is a private APN

A private APN is a mobile network access point dedicated to a single company or project. Your IoT traffic never touches the public internet: it exits the carrier straight to your data center over a private tunnel, with your own IP plan, firewall rules, and routing.

What is Multi-IMSI

Multi-IMSI is a SIM technology that hosts several IMSIs (subscriber identifiers) on a single card and picks one based on country, signal quality, or cost. The device authenticates as a customer of carrier A in one place and as carrier B in another, with no hardware change.

What is permanent roaming

Permanent roaming is when a SIM connects continuously (beyond a few months) to a network other than its home carrier, never returning home. In IoT it is the norm, not the exception: a tracker deployed in Mexico can live for 10 years on Mexican networks with a Spanish-issued SIM.

What is LTE-M

LTE-M (also LTE Cat-M1) is an LTE variant designed for IoT: moderate bandwidth (up to 1 Mbps), very low power, voice support, and real cell-to-cell mobility. It is the sweet spot between NB-IoT (cheaper but static) and Cat-1 (faster but power-hungry).

What is NB-IoT

NB-IoT (Narrowband IoT) is a 4G/5G LPWA technology optimized for small messages from static, multi-year battery devices. It runs in a 200 kHz sub-band and prioritizes deep coverage and extreme power efficiency over throughput.

What is LTE Cat-1

LTE Cat-1 is the LTE device category targeted at general-purpose IoT: up to 10 Mbps down, 5 Mbps up, voice support, and works on any 4G network worldwide. Its Cat-1 bis variant runs on a single antenna, cutting hardware cost. It is the workhorse behind POS terminals, alarms, gateways, and low-bitrate CCTV.

What is MFF2

MFF2 (Machine-to-Machine Form Factor 2) is the solderable SIM: a 6x5 mm chip mounted directly on the PCB, no tray or socket. It is the de-facto standard in industrial IoT, automotive, and any device facing vibration, humidity, or extreme temperatures.

What is SGP.32

SGP.32 is the GSMA Remote SIM Provisioning standard built specifically for IoT, published in 2023. It supersedes SGP.02 (M2M) and removes the dependency on SGP.22 (Consumer) for headless devices. It introduces the IPA (IoT Profile Assistant) and a Pull model where the device requests profiles by country or event.

What are PSM and eDRX

PSM (Power Saving Mode) and eDRX (extended Discontinuous Reception) are 3GPP-defined mechanisms that let a cellular IoT device draw microamps while idle. PSM turns the modem off between long windows (up to days); eDRX spaces paging listening in short intervals (seconds to minutes) without losing network registration.

What is VPLMN

VPLMN (Visited Public Land Mobile Network) is the mobile network a SIM attaches to when away from its HPLMN (the home carrier's network). In international IoT, the VPLMN choice drives roaming cost, latency, and tech availability (LTE-M, NB-IoT) in each country.

ICCID, IMSI, and IMEI

ICCID identifies the physical SIM chip. IMSI identifies the subscriber on the mobile network. IMEI identifies the device (modem) holding the SIM. Three different identifiers, all three needed to manage an IoT fleet.

What is a CDR in IoT

A CDR (Call Detail Record) is the detailed record of every data, voice, or SMS session of a SIM. In IoT it is the source of truth for billing, fraud detection (anomalous traffic), and diagnostics (knowing why a device is silent).

What is MQTT

MQTT (Message Queuing Telemetry Transport) is a very lightweight publish/subscribe protocol designed for devices with little CPU, little RAM, and flaky links. It works against a central broker (Mosquitto, HiveMQ, EMQX, AWS IoT Core) and carries most modern industrial IoT traffic.

What is an IoT VPN

An IoT VPN is an encrypted tunnel between the carrier exit and the customer infrastructure. It lets devices on the cellular network reach private servers without going over the public internet. Typical options are IPSec, WireGuard, and L2TP/IPSec.

What is a static-IP IoT SIM

A static-IP SIM is an IoT card the carrier always assigns the same IP address to, instead of a different dynamic IP per session. It can be public (reachable from the internet) or private (reachable from your private APN or VPN). It is essential whenever a server needs to initiate the connection to the device.

What is iSIM

iSIM (integrated SIM) is a SIM whose silicon lives inside the modem or SoC, not as a separate chip. It shares the same eUICC logic and the same GSMA standards, but takes zero extra board space and trims bill of materials.

What is IoT eSIM

IoT eSIM is the eUICC SIM designed for headless devices. It inherits smartphone eSIM programmability but uses a Pull provisioning flow (SGP.32) where the device asks the server for a profile, without scanning a QR code or entering an activation code.

2

2G / GSM: Second-generation mobile networks. Still useful for very low-power, low-data devices, though several carriers are shutting down their 2G networks.

3

3G / UMTS: Third generation. Introduced for faster mobile data. Being progressively retired across Europe in favor of 4G and 5G.

4

4G / LTE: Fourth generation. The current standard for devices that need real bandwidth (video streaming, IP cameras, EV chargers).

5

5G: Fifth generation. Higher bandwidth, lower latency, higher device density per cell. Relevant for Industry 4.0, connected vehicles and edge computing.

A

APN (Access Point Name): The access point a device uses to reach the internet over the mobile network. Can be public or private. A private APN isolates M2M traffic from public internet traffic.

B

BESS (Battery Energy Storage System): Battery-based energy storage. In solar PV it is connected over IoT for telemetry of state of charge, cycles, temperature and degradation.

C

CPO (Charge Point Operator): Operator of EV charging stations. Manages the charger fleet, session authorization and pricing.

E

eMSP (eMobility Service Provider): E-mobility service provider. Delivers the driver-facing app or RFID card and does roaming across CPOs via OCPI.
eSIM / eUICC: Embedded SIM soldered into the device (MFF2 or eUICC form factors). Lets you switch carrier profile in software without touching hardware.

G

GPRS: Data service over 2G. Still around in older industrial telemetry deployments that only need a few bytes now and then.

I

ICCID: Unique identifier printed on every SIM card. 19 or 20 digits. Used to locate and manage the SIM from the portal.
IMEI: Unique identifier of the mobile device itself (hardware). It does not travel with the SIM; it travels with the equipment.
IMSI: Unique subscriber identifier on the mobile network. Lives inside the SIM and is what the carrier uses to authenticate the device.
IoT (Internet of Things): Ecosystem of connected devices that gather and send data over the internet. IoT covers everything from water sensors to cameras and vehicles.
IoT SIM / M2M SIM: A SIM designed for unattended devices: extreme temperature tolerance, long shelf life, support for private APN, static IP and multi-carrier.

L

LPWA (Low-Power Wide Area): Family of low-power, wide-coverage radio technologies: LTE-M, NB-IoT, LoRaWAN, Sigfox. Designed for battery-powered sensors that must last years.
LTE-M (LTE Cat-M1): LTE variant optimized for IoT: lower power, better indoor coverage, voice and mobility support. Ideal for wearables and moving assets.

M

M2M (Machine-to-Machine): Direct communication between machines without human intervention. The industrial precursor to IoT, focused on telemetry and remote control.
MQTT: Lightweight publish/subscribe messaging protocol, widely used in IoT for its low overhead and resilience on flaky networks.
Multi-carrier: SIM capable of automatically connecting to several mobile carriers. Increases coverage and resilience against individual network outages.
MVNO: Mobile Virtual Network Operator. Offers mobile services on top of another carrier's (MNO) network. iot.cards operates as an M2M-focused MVNO.

N

NB-IoT (Narrowband IoT): LPWA technology on top of mobile networks. Ultra-low power, deep indoor coverage. Ideal for meters, parking sensors and static monitoring points.
NVR (Network Video Recorder): Network-based video recorder. In CCTV it receives the streams from IP cameras and stores them. Many NVRs need a static IP for remote access.

O

OCPI (Open Charge Point Interface): Protocol that enables roaming between charging networks, so a driver from one eMSP can charge at any participating CPO.
OCPP (Open Charge Point Protocol): Open protocol between EV chargers and the CPO platform. Versions 1.6 and 2.0.1 are the most widely deployed.
OEM (Original Equipment Manufacturer): The manufacturer of the end device. In IoT, OEMs integrate connectivity modules and SIMs (or eSIMs) into their own products.

P

Permanent roaming: Long-term use of a SIM outside its home country. Some countries (Brazil, Turkey, India, China) restrict it by regulation and require local solutions.
PLC (Programmable Logic Controller): The industrial automation workhorse: receives commands and performs real-time control on motors, valves and sensors.
POS terminal: Point-of-sale card reader. Connected via IoT SIM when there is no WiFi or a 4G backup is required. Needs low latency to authorize transactions.
PR (Performance Ratio): Performance indicator for a solar PV plant: actual vs theoretical energy production. Key metric for O&M and shading/soiling detection.
Private APN: A dedicated APN for one company or project, with its own IP rules, firewall and optional VPN straight to the customer data center. Recommended for critical deployments.

R

Roaming: A device's ability to connect to a mobile network other than its home one in a different country or territory. In IoT this usually means permanent, surcharge-free roaming.
RTSP (Real-Time Streaming Protocol): Protocol for controlling video streaming. Used by virtually every professional IP CCTV camera.

S

Smart metering: Remote meter reading for electricity, gas or water. Huge device counts, little traffic per device, long service life.
Static IP: An IP address that does not change between sessions. Required whenever a backend needs to open an inbound connection to the device (CCTV NVR, OCPP charger, remote PLC access).
Static-IP SIM: A SIM with a fixed public or private IP assigned. Used whenever the server needs to reach the device (camera, charger, industrial gateway).

V

VPN (Virtual Private Network): Encrypted tunnel between the mobile network and the customer infrastructure. Combined with a private APN, it delivers a dedicated, secure channel for all M2M traffic.

Missing a term?

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