What is Cellular IoT? A Guide for Embedded Developers

Rob LauerSenior Director of Developer Relations

Introduction

If you're here, you likely already know that cellular IoT is one of the most transformative technologies shaping the future of wireless connectivity. At its core, cellular IoT enables devices to transmit data over existing cellular networks, just like your smartphone, but optimized for machine-to-machine communication in power- and bandwidth-limited implementations. This evolution in connectivity empowers embedded developers to create intelligent, autonomous products that function across vast geographic areas without relying on local infrastructure like Wi-Fi or Ethernet. In short, it helps eliminate the complexity of custom wireless connectivity solutions and accelerates time-to-market for modern IoT applications.

In this article, we'll explore what cellular IoT is, why it matters, and how Blues is solving some of the most persistent challenges in deploying cellular IoT modules through its flagship products: Blues Notecard and its companion cloud service Notehub.

The Rise of Cellular IoT

In the early days of IoT, devices often relied on short-range communication technologies like Bluetooth, Zigbee, Wi-Fi, or LoRa and LoRaWAN. While effective in localized environments, these solutions quickly revealed their limitations when projects scaled geographically or required mobility. As cellular technology matured, developers started experimenting with traditional 2G and 3G networks to connect devices. However, these networks weren't built for IoT use cases and required complex, power-hungry hardware stacks, making them unfeasible for many use cases.

With the global phase-out of 2G and 3G and the rise of 4G LTE, the cellular industry responded by defining new LTE categories optimized for IoT: LTE Cat-1 bis, LTE-M, and NB-IoT. These protocols brought lower power usage, reduced bandwidth needs, and simplified modules, all while leveraging the existing infrastructure of cellular towers. Today, cellular IoT stands at the forefront of global IoT deployments, bridging the gap between isolated sensors and the cloud, no matter the geography.

According to IoT Analytics, the number of licensed cellular IoT connections surpassed 4 billion in 2024, and that number is expected to double in the next five years. Applications range from agriculture and smart cities to transportation and logistics, driven by the global availability, mobility, and security inherent in cellular networks.

The Basics of Cellular IoT

Cellular IoT refers to the use of cellular networks, such as LTE today and 5G tomorrow, for connecting IoT devices to the wider Internet. Unlike traditional mobile devices, IoT endpoints often prioritize characteristics like power efficiency, long-range connectivity, and low bandwidth, rather than high data throughput. These endpoints are often embedded systems that perform specific tasks: monitoring sensor data, reporting equipment status, tracking assets, or automating industrial processes.

To meet the needs of IoT use cases, specialized cellular protocols have emerged within the LTE family as previously mentioned:

• LTE Cat-1: A reasonably high-bandwidth (or "wideband") option offering reliable coverage and high data rates (up to 10 Mbps downlink), suitable for many general-purpose IoT use cases.

• LTE Cat-1 bis: A cost-optimized (or "midband") version of LTE Cat-1 that uses a single antenna, simplifying RF design and reducing BOM cost. Cat-1 bis is ideal for small-form-factor devices.

• LTE-M (a.k.a. LTE Cat-M1): A low-power wide-area network (LPWAN or "narrowband") technology with deep coverage, low power consumption, and mobility support. Excellent for battery-powered applications and global roaming.

• NB-IoT: Ultra-low power, low bandwidth, and deep indoor coverage (like LTE-M considered "narrowband"). Perfect for simple sensors that transmit small packets infrequently, but falling out of favor from some carriers.

Let's break these down a bit further in terms of high-level use cases:

LTE Cat-1 is best for use cases needing moderate data throughput, such as smart video doorbells or real-time POS terminals. LTE Cat-1 bis serves similar functions but at lower cost and with simpler antenna design, making it a favorite for compact and cost-sensitive products like GPS trackers. LTE-M shines in applications requiring long battery life and mobility, like asset tracking or wearable health monitors. NB-IoT is ideal for fixed-location sensors that only need to transmit tiny bursts of data every few hours, like utility meters or parking space sensors.

Deployment Challenges with Traditional Cellular IoT

Before Blues hit the market in 2019, developers faced a daunting list of challenges when launching a cellular IoT device:

• Navigating cellular carrier negotiations and provisioning SIM cards across different regions.
• Managing billing, roaming fees, and opaque pricing models.
• Handling carrier certifications, RF tuning, and antenna design.
• Wrestling with AT command sets and modem firmware.
• Building secure OTA update pipelines and cloud connectivity layers.
• Designing ultra-low power sleep/wake cycles from scratch.

Worse yet, every component of this system often came from a different vendor. The modem, antenna, SIM, carrier, TLS stack, and backend cloud infrastructure... each introduced risk, complexity, and integration overhead. The cost of mistakes was high, and the time to deploy often stretched into months or years.

Blues: Cellular IoT, Simplified

Blues is legitimately redefining cellular IoT by eliminating complexity and providing a developer-first experience. The centerpiece of this approach is Blues Notecard Cellular: a tiny, fully integrated system-on-module that handles all aspects of cellular connectivity. It measures just 30x35mm but includes a cellular modem, eSIM, antenna interfaces, embedded secure element, GPS, and accelerometer. Think of it as a cellular IoT module or an LTE-M dev kit (but with the option to use other cellular protocols as well).

What makes Notecard Cellular revolutionary isn't just the hardware, it's the design philosophy. Every unit ships prepaid with 500MB of data and 10 years of cellular service, with no connection fees or SIM activation costs. Developers can go from concept to prototype without ever dealing with a mobile carrier.

Different Notecard Cellular variants support LTE Cat-1, Cat-1 bis, LTE-M, and NB-IoT, allowing you to choose the ideal cellular protocol for your product. Whether you need high bandwidth for high-res images or ultra-low power for remote sensors, there's a Notecard to match.

Because every Notecard is pre-certified and includes embedded cryptographic keys, you avoid the pain of carrier certification, SIM provisioning, or secure key exchange. And thanks to Notecard's store-and-forward architecture, devices can queue data for transmission when connectivity is available, ensuring reliability even in low-signal or offline environments.

But what's it like to develop a product around Notecard?

JSON-Based Development with Cross-RAT APIs

One of the most frustrating aspects of cellular modem programming is dealing with AT command sets. With Blues, that's gone. All interaction with Notecard happens via a developer-friendly JSON API. You send and receive JSON messages over UART, USB, or I2C with no modem programming or proprietary protocols to learn.

Each data packet you create is referred to as a Note, and Notes are organized into logical groupings called Notefiles. These Notefiles are then synced with Notehub, Blues' secure cloud service that routes your data to any cloud endpoint.

For example, you may need to sync your device's sensor data with the cloud like so:

{
  "req": "note.add",
  "file": "sensor.qo",
  "body": { "temp":35.5, "humid":56.23 },
  "sync": true
}

This JSON interface remains consistent whether you're using a Nordic nRF, STM32, ESP32, or even a Raspberry Pi. Blues supports SDKs for C, Arduino, Go, Python, and Zephyr RTOS. Developers can get started quickly, and firmware complexity stays low even as feature sets grow.

Why JSON is the Right Interface for IoT

Choosing JSON as the universal interface for Notecard wasn't accidental: it was deliberate, practical, and developer-centric.

JSON is human-readable, which means developers can interact with the Notecard API using nothing more than a serial terminal and text editor. When you're debugging in the field or over a USB/UART bridge, being able to see and edit commands without compiling firmware is invaluable.

It's also language-agnostic. JSON plays well with C, Python, JavaScript, Go, and nearly every platform. Whether you're prototyping on a Raspberry Pi or building production firmware on an STM32, the data model remains the same. Moreover, JSON reduces context switching. IoT developers already deal with plenty of protocols, SDKs, and configuration systems. A single JSON-based API means fewer abstractions to learn and less documentation to juggle.

Finally, JSON aligns with how the cloud works. Since your Notes eventually get routed to cloud services, most of which are JSON-first, there's no need for translation layers, protobuf schemas, or binary decoders. The data stays consistent from device to cloud.

Routing, Transforming, and Managing Data with Notehub

Once your data gets from device (Notecard) to cloud (Notehub), what happens then? Let's take a closer look at Notehub and its capabilities.

For starters, Notehub is not a bloated cloud platform. It's a lean, purpose-built intermediary that facilitates secure communication between Notecards and your preferred cloud destination. Whether you're using AWS, Azure, GCP, Snowflake, or a low-code IoT platform like Losant, Datacake, or Ubidots, Notehub makes routing data effortless.

The secure transport path looks like this:

1. Notes are collected on-device using Notecard.
2. When connectivity is established, accumulated Notes are synced with Notehub.
3. Notehub routes that data to your chosen endpoint, applying transformations if necessary.

Notehub also supports bi-directional communication, so your cloud app can send configuration updates, environment variables, or control commands back to the device in the field.

And because Notecard and Notehub handle TLS, retries, and secure identity management automatically, your data stays protected in transit without you needing to manage certs or rotate keys.

Notehub: Secure by Default

Speaking of security, the unfortunate reality of today is that security isn't optional, it's essential. Every Notecard ships with a unique identity and cryptographic keys embedded at the point of manufacture. That means no device claiming, key rotation, or OTA certificate installs.

All traffic between Notecard and Notehub is encrypted by default. Communications occur over cellular networks (which are inherently more secure than open Wi-Fi), and TLS is enforced for all cloud-bound messages. You get end-to-end encryption with zero configuration.

Blues also enables fine-grained access control at the Notehub layer, allowing you to define access policies per project or per device group. This multi-layered approach ensures that devices in the field remain trustworthy, tamper-resistant, and unbrickable.

Notehub: Seamless OTA Firmware Updates and Fleet Management

With Notehub, you can securely push firmware updates to both Notecards and their attached hosts. These updates are version-controlled and resilient, minimizing the risk of bricked devices. OTA is often an afterthought in IoT projects, but Blues bakes it in from day one.

Update delivery is conditional. You can push updates only when a device is idle, in range, or at full battery. This ensures your fleet stays online and healthy without risking uptime.

Notehub also gives you visibility into your fleet: connection frequency, last sync timestamp, data usage, firmware version, and custom metadata. Whether you're monitoring 10 devices or 10,000, you get clear operational insights without building infrastructure.

Notehub: Visualizing the Notecard Data Flow

To illustrate the simplicity of Blues' architecture, imagine a fictional smart parking sensor deployed in a city block:

1. A car arrives in a spot. The sensor detects the change via a magnetic switch.
2. Your host MCU formats a JSON object like { "occupied": true } and sends it to Notecard.
3. Notecard stores the Note locally in a Notefile called parking.qo.
4. Every 15 minutes (or on a triggered sync), Notecard connects to the nearest LTE tower and transmits the Notefile to Notehub.
5. Notehub transforms the message, attaches metadata like GPS location and/or timestamp, and routes it to your chosen cloud endpoint.
6. Your application receives the data and updates a live dashboard. It can also send a downlink Note back to the device to change LED behavior or log occupancy time.

This flow (device --> Notecard --> Notehub --> cloud --> back to device) requires no carrier negotiation, no certificate provisioning, and no infrastructure maintenance.

Blues Notecard Features

Let's take a closer look at a few key features that are standard on Blues Notecard Cellular.

Built-in GPS and Motion Sensing

Notecard Cellular includes a GPS/GNSS module and accelerometer in every variant. This is invaluable for asset tracking, condition monitoring, or geofencing applications. You can acquire location data or wake the device on movement without additional components, reducing BOM complexity and battery power budget.

GPS data can be attached to Notes and sent to Notehub, or used locally to guide application logic. With integrated motion detection, you can design smarter tracking devices that only ascertain their location and/or transmit when they have moved.

Designed for Low Power from Day One

Battery life is non-negotiable for many IoT applications. Notecard Cellular is engineered to be low-power out of the box. In idle mode, it draws just 8-18uA@5V, orders of magnitude lower than most cellular modules. This makes it ideal for battery-powered sensors, remote monitoring stations, or portable asset trackers.

You don't need to build complex power management routines. Notecard handles sleep modes, wake triggers, and data batching automatically. The result? Long-lasting devices with minimal firmware complexity.

One API, Any Network

Blues understands that your network requirements may evolve. That's why the Notecard API is radio-agnostic. The same API is used for Notecards supporting cellular, Wi-Fi, LoRa, or even the cellular and satellite combination powered by Blues Starnote. You can switch between radios without rewriting firmware or retooling your backend infrastructure.

This ability to switch radios is a game-changer when you're designing a family of products for different environments. Deploy the same firmware across a global fleet, and simply swap in the appropriate Notecard!

Cellular vs Wi-Fi, LoRa, and Satellite

While cellular IoT offers unparalleled reach and simplicity, it's not always the only—or even the best—connectivity option (depending on your product's environment). Let's examine where cellular stands relative to Wi-Fi, LoRa, and satellite communications.

Wi-Fi excels in indoor environments with infrastructure already in place. It's a logical choice for smart home devices, appliances, or building automation, but it fails in remote or mobile scenarios, and power consumption is often higher due to constant connection requirements.

LoRa and LoRaWAN are optimized for ultra-low power and long-range transmission in fixed applications like agriculture, industrial telemetry, or smart cities. However, they require dedicated gateways, and offer limited bandwidth.

Satellite connectivity, while truly global, tends to come with high latency and higher cost. It's a great fallback for extreme conditions where no other networks exist, but not ideal for always-on communication.

Cellular hits a sweet spot across these trade-offs. It offers global infrastructure, bidirectional communication, mobility, security, and a balance of performance and power efficiency. And with Blues' multi-radio Notecards, you're not locked in. If your product needs Wi-Fi in urban settings and LTE-M in rural ones, or cellular with satellite fallback, Blues makes that effectively invisible.

How Blues Customers Deploy with Confidence

Let's look at a few examples that mirror real-world deployments with Blues Notecard:

A precision agriculture company deploys 10,000 soil sensors across remote farmland. Each device uses a Notecard Cellular with LTE-M to transmit environmental data every 4 hours. The devices sleep deeply between transmissions, drawing just microamps, and wake on schedule. No SIM management, no cellular contracts: just plug, program, and deploy.

A logistics firm installs Notecards in shipping pallets for real-time asset tracking. Using LTE Cat-1 bis, they get consistent global coverage and location data via Notecard's integrated GPS. Notecard queues data when in transit and uploads when connectivity resumes. OTA firmware updates are pushed via Notehub during warehouse stops.

A wildlife researcher uses solar-powered sensors with cellular connectivity in remote national parks with a satellite backup via Blues Starnote. The devices only transmit once a day and rely on store-and-forward and bi-directional messaging to adjust behavior based on cloud-defined schedules. Power consumption is minimal, and battery replacements are rare.

Design Tips for Building with Cellular IoT

Launching a product on cellular brings unique hardware and software design considerations. Here are some best practices developers should follow when working with Notecard Cellular:

Antenna selection and placement are crucial. Always place the cellular antenna away from high-speed digital traces or metal enclosures. Follow the guidance provided by Blues or your antenna manufacturer to avoid detuning and performance issues.

Power budgeting matters more than you think. Cellular modules experience current spikes during transmission (up to 2A depending on the network). Make sure your power supply (especially in battery-powered applications) can handle peak draw, and use low-dropout regulators where needed.

Take advantage of Notecard's built-in store-and-forward capability. You don't need to maintain a persistent connection. Batch your Notes locally using the ample flash storage and let Notecard handle timing and retry logic. This not only saves power but improves overall reliability in flaky coverage zones.

If you're deploying globally, test multiple protocol options (Cat-1 vs Cat-1 bis vs LTE-M vs NB-IoT) in your target regions. Some operators disable NB-IoT or only offer LTE-M in specific countries. The Blues Notecard datasheets offer country-by-country support information to help you plan.

Final Thoughts

Cellular IoT has never been more accessible. Blues removes the traditional pain points—from RF design to carrier negotiation to cloud integration—by providing a plug-and-play solution that just works. With Notecard Cellular, you get a prepaid, pre-provisioned, secure system-on-module that pairs seamlessly with any host device and any cloud.

Combined with Notehub, you gain secure data routing, fleet management, and over-the-air updates without building a backend from scratch. Add in support for the latest cellular protocols like LTE Cat-1, Cat-1 bis, LTE-M, and NB-IoT, and the result is a platform purpose-built for the real world.

Cellular IoT is no longer the domain of telecom giants and enterprise engineering teams. With Blues, it's in your hands. Visit blues.com to learn more, or just start building with a Blues Starter Kit and our complete developer documentation.