10 IoT Glossary: Terms From S Through V
10.1 Start With the Decision
A design review now covers sensors, security, storage, and wireless links. Clear terms keep those choices precise.
10.2 Route Overview
This is part 1 of 2. Continue with IoT Glossary: Terms From W Through Z.
10.3 Part Objectives
- Test s with a concrete scenario and pass criteria.
- Validate u with a concrete scenario and pass criteria.
10.4 Start With the Situation
A design review has moved from routing and reliability to sensors, security, storage, and wireless choices. This second reference route collects the S-Z vocabulary needed to describe those decisions precisely.
10.5 Overview
This route covers S-Z terms, connecting sensing and security vocabulary to time-series systems and late-alphabet wireless protocols.
This is part 2 of 2. Review IoT Glossary: Q-R when you need the first route.
10.6 Learning Objectives
By the end of this chapter, you will be able to:
- define S-Z IoT terms precisely
- distinguish related sensing, security, and storage terms
- apply wireless and time-series vocabulary in design reviews
10.7 Chapter Roadmap
- Start With the Situation
- Overview
- S
- T
- Knowledge Check: Choosing the Right Database
- U
10.8 S
10.8.1 Sampling
Definition: The process of converting continuous signals into discrete values at regular intervals, with sampling rate determining how often measurements are taken.
In simple terms: Taking periodic snapshots - instead of continuous recording, take measurements at regular intervals, like checking temperature every minute instead of watching a thermometer constantly.
Common confusions:
- To reconstruct a band-limited signal, sampling rate needs to exceed twice the highest frequency of interest; many IoT sensing tasks use lower rates when they only need trends or thresholds
- Higher sampling rates produce more data but may not add value
Related terms: ADC, Time Series, Aggregation
Synonyms: data sampling, signal sampling
10.8.2 Schema
Definition: A formal description of data structure defining field names, types, constraints, and relationships, used to validate data and ensure consistency across systems.
In simple terms: A data template - specifies what fields data should have and what types they should be, like a form that defines required fields and their formats.
Common confusions:
- Schema-on-write vs. schema-on-read have different flexibility/reliability tradeoffs
- Schema evolution needs versioning and compatibility rules so older devices and newer services can coexist
Related terms: JSON, Protobuf, Serialization
Synonyms: data schema, data model
10.8.3 Sensor
Definition: A device that detects and measures physical properties (temperature, light, motion, pressure) and converts them into electrical signals that can be processed by electronic systems.
In simple terms: The eyes and ears of IoT - devices that measure the real world and report what they sense, like a thermometer that tells a computer what the temperature is.
Common confusions:
- Sensor vs. transducer - sensors measure, transducers convert energy forms (sensors are a type of transducer)
- Sensor accuracy vs. precision are different characteristics
Related terms: Actuator, ADC, Telemetry
Synonyms: detector, transducer
10.8.4 Serialization
Definition: The process of converting data structures or objects into a format suitable for storage or transmission, enabling reconstruction of the original structure later (deserialization).
In simple terms: Packing for shipment - converting complex data into a flat format that can be sent over a network or saved to disk, then unpacking it at the destination.
Common confusions:
- Serialization format affects size, speed, and compatibility (JSON vs. CBOR vs. Protobuf)
- Deserialization needs validation for malformed, oversized, or malicious data
Related terms: JSON, CBOR, Protobuf, Payload
Synonyms: marshalling, encoding
10.8.5 Serverless
Definition: A cloud computing execution model where the cloud provider dynamically manages server allocation, charging only for actual execution time, abstracting infrastructure management.
In simple terms: Computing without managing servers - write code that runs when needed without worrying about servers, scaling, or paying for idle time, like renting a taxi versus owning a car.
Common confusions:
- Serverless still uses servers, you just don’t manage them
- Cold start latency can affect time-sensitive applications
Related terms: Cloud, Microservices, Platform
Synonyms: Function as a Service (FaaS), Lambda
10.8.6 Sigfox
Definition: A proprietary LPWAN technology using ultra-narrowband modulation for very low-power, low-throughput IoT communication, associated with operated network services where coverage is available.
In simple terms: A managed low-data IoT network - like a phone-network model for simple sensors, intended for devices that send very small payloads infrequently.
Common confusions:
- Sigfox is network-as-a-service (you don’t deploy your own infrastructure)
- Very limited uplink payload size and daily message count in common Sigfox service profiles
Related terms: LPWAN, LoRaWAN, NB-IoT
Synonyms: none common
10.8.7 SoC (System on Chip)
Definition: An integrated circuit that combines a processor, memory, I/O interfaces, and often wireless connectivity into a single chip, providing complete computing functionality for embedded systems.
In simple terms: An entire computer on one chip - everything from the processor to Wi-Fi radio combined into a single piece of silicon, making it easy to build small, integrated devices.
Common confusions:
- SoC vs. microcontroller - SoCs typically include more features like wireless, microcontrollers are simpler
- Examples: ESP32, Nordic nRF52, Raspberry Pi RP2040
Related terms: Microcontroller, GPIO
Synonyms: System on a Chip, integrated SoC
10.8.8 SPI (Serial Peripheral Interface)
Definition: A synchronous serial communication interface using four wires (clock, data in, data out, select) for high-speed communication between a microcontroller and peripheral devices.
In simple terms: Fast wired communication - uses more wires than I2C but is faster, good for sensors and displays that need to transfer lots of data quickly.
Common confusions:
- SPI vs. I2C - SPI is faster but needs more wires and individual select lines per device
- SPI has multiple modes (CPOL/CPHA) that need to match between devices
Related terms: I2C, UART, GPIO
Synonyms: four-wire serial bus
10.8.9 Star Topology
Definition: A network topology where all devices connect to a central hub or coordinator, with all communication flowing through this central point rather than directly between devices.
In simple terms: Hub-and-spoke design - every device connects to one central point, like streets radiating from a town center. Simple, but the center becomes a critical dependency.
Common confusions:
- Star vs. mesh - star is simpler but less resilient, mesh has redundant paths
- Wi-Fi networks typically use star topology with the access point as center
Related terms: Mesh, Routing, Gateway
Synonyms: hub topology, centralized topology
10.8.10 Subscriber
Definition: A client in publish-subscribe messaging that registers interest in specific topics and receives messages published to those topics, without direct connection to publishers.
In simple terms: A listener - signs up to receive certain types of messages from the system, like subscribing to a newsletter to receive updates on topics you care about.
Common confusions:
- Subscriber vs. consumer - essentially the same concept
- Subscribers are decoupled from publishers (don’t know who’s sending)
Related terms: Publisher, Topic, Subscription, Broker
Synonyms: consumer, receiver, listener
10.8.11 Subscription
Definition: A registration with a message broker expressing interest in receiving messages matching certain criteria (typically topic patterns), maintained until explicitly cancelled.
In simple terms: A standing order for messages - tell the broker “send me anything about topic X” and you’ll receive matching messages until you unsubscribe.
Common confusions:
- Subscription vs. topic - subscription is the registration, topic is what you subscribe to
- Durable vs. non-durable subscriptions persist (or not) across disconnections
Related terms: Topic, Subscriber, Filter, Wildcard
Synonyms: topic subscription
10.9 T
10.9.1 Telemetry
Definition: The automated collection and transmission of measurements from remote devices to receiving equipment for monitoring, including sensor readings, status information, and performance metrics.
In simple terms: Remote sensing data - the continuous stream of measurements sent from devices in the field back to a central system, like vital signs monitors sending patient data to nurses’ stations.
Common confusions:
- Telemetry vs. commands - telemetry flows from devices, commands flow to devices
- Telemetry vs. logs - telemetry is structured measurements, logs are event records
Related terms: Sensor, Time Series, MQTT
Synonyms: device telemetry, sensor data, metrics
10.9.2 Thread
Definition: An IPv6-based mesh networking protocol designed for smart home devices, providing secure, low-power communication with mesh routing and border-router connectivity.
In simple terms: Modern smart home mesh - a low-power way for home devices to communicate using IPv6, often used as a network transport for Matter devices.
Common confusions:
- Thread vs. Zigbee - Thread uses IP, Zigbee has its own network layer
- Thread is a transport for Matter (they work together)
Related terms: Matter, Mesh, 6LoWPAN, Zigbee
Synonyms: Thread Group protocol
10.9.3 Throughput
Definition: The actual rate at which data is successfully transferred over a network connection, typically lower than bandwidth due to protocol overhead, errors, and congestion.
In simple terms: Real-world speed - while bandwidth is the maximum theoretical capacity, throughput is how fast data actually moves in practice, accounting for all the overhead and delays.
Common confusions:
- Throughput vs. bandwidth - throughput is achieved rate, bandwidth is capacity
- Throughput varies based on conditions, bandwidth is a fixed characteristic
Related terms: Bandwidth, Latency
Synonyms: actual speed, effective bandwidth
10.9.4 Time Series
Definition: A sequence of data points indexed by time, commonly used in IoT for recording sensor measurements, metrics, and events with timestamps for temporal analysis.
In simple terms: Data ordered by time - measurements collected over time, like temperature readings every minute, stored in time order so you can see trends and patterns.
Common confusions:
- Time series databases are optimized differently than relational databases
- Time series data often requires special handling for gaps and irregular intervals
Related terms: TSDB, Telemetry, Timestamp, Aggregation
Synonyms: temporal data, time-stamped data
10.9.5 TimescaleDB
Definition: An open-source time series database built on PostgreSQL, combining full SQL support with time series optimizations for IoT, monitoring, and analytics workloads.
In simple terms: SQL-friendly time series database - handles sensor data efficiently while letting you use familiar SQL queries and benefiting from PostgreSQL’s ecosystem.
Common confusions:
- TimescaleDB vs. InfluxDB - TimescaleDB uses SQL, InfluxDB has its own query languages
- TimescaleDB is an extension to PostgreSQL, not a standalone database
Related terms: TSDB, InfluxDB, Time Series
Synonyms: none common
10.9.6 Timestamp
Definition: A recorded point in time associated with data, typically expressed in a standardized format like Unix epoch time or ISO 8601, essential for ordering and correlating events.
In simple terms: A date-time stamp - marks when something happened, like the postmark on a letter, essential for knowing when sensor readings were taken.
Common confusions:
- Timestamp precision matters (seconds vs. milliseconds vs. microseconds)
- Timezone handling is crucial for distributed systems
Related terms: Time Series, Metadata, Telemetry
Synonyms: datetime, epoch time
10.9.7 TLS (Transport Layer Security)
Definition: A cryptographic protocol providing secure communication over networks through encryption, authentication, and integrity verification, the successor to SSL.
In simple terms: The “S” in HTTPS - encrypts data in transit so eavesdroppers can’t read it, verifies server identity, and ensures data hasn’t been tampered with.
Common confusions:
- TLS vs. SSL - TLS is the modern successor, SSL is deprecated
- TLS works with TCP, use DTLS for UDP
Related terms: DTLS, HTTPS, Certificate, Encryption
Synonyms: SSL/TLS, secure sockets
10.9.8 Token
Definition: A digital credential used for authentication or authorization, typically a string containing encoded information about identity and permissions with expiration time.
In simple terms: A digital key card - proves who you are and what you’re allowed to do, like a badge that gets you through certain doors for a limited time.
Common confusions:
- Access tokens vs. refresh tokens serve different purposes
- JWT (JSON Web Token) is one common token format
Related terms: Authentication, OAuth, Authorization
Synonyms: access token, bearer token, JWT
10.9.9 Topic
Definition: A named channel or subject in publish-subscribe messaging systems that publishers send messages to and subscribers receive messages from, enabling message routing.
In simple terms: A message address or category - like a TV channel number, publishers broadcast to a topic and anyone tuned to that topic receives the messages.
Common confusions:
- Topic hierarchy (sensors/temperature/room1) enables organized message routing
- Topics are usually strings, not queues (messages aren’t stored by default)
Related terms: Publisher, Subscriber, Subscription, MQTT
Synonyms: channel, subject, message topic
10.9.10 TSDB (Time Series Database)
Definition: A database optimized for storing, querying, and analyzing time-stamped data, featuring efficient compression, time-based indexing, and specialized query functions.
In simple terms: A database built for sensor data - designed to handle high-volume time-stamped measurements efficiently, with features such as retention policies, compression, downsampling, and time-window queries.
Common confusions:
- TSDB vs. relational database - TSDBs optimize for time-based writes and queries
- Examples: InfluxDB, TimescaleDB, Prometheus, QuestDB
Related terms: Time Series, InfluxDB, TimescaleDB
Synonyms: time series database
10.10 U
10.10.1 UART (Universal Asynchronous Receiver/Transmitter)
Definition: A hardware communication protocol for asynchronous serial communication between devices, using two wires (TX and RX) without requiring a shared clock signal.
In simple terms: Basic serial communication - the simplest way for two devices to talk to each other over wires, like an old-fashioned telegraph system for digital data.
Common confusions:
- UART vs. I2C/SPI - UART is point-to-point and asynchronous, I2C/SPI support multiple devices
- Baud rate needs to match between sender and receiver
Synonyms: serial port, RS-232 (related standard)
10.11 Continue to the Next Part
Carry this evidence into IoT Glossary: Terms From W Through Z, which begins with W.