IoT Hacking Series #1: IoT Hardware Guide to Cellular Connectivity for Dummies

Tags: IoT
A picture of Ken-Tristan  Peterson
Written by
Ken-Tristan Peterson
1oT is excited to announce that it will feature a new blog post series - IoT Hacking Series.
We want to bring insight into cellular hardware with technical blog posts and DIY hardware projects, that can be fun to experiment but also helpful to start with your product prototyping. Let’s kick off this series with a hardware guide for newcomers!

In a need of a connectivity solution for your Internet of Things (IoT) or Machine-to-Machine (M2M) product under development or in mind? Are you just starting out and don’t know what prototyping board to use? We have compiled a hardware guide for you to follow along and get your product started. The goal of this blog post is to give a basic overview of hardware components that can be used in cellular connected IoT devices.

Cellular connectivity?

First, we need to choose the right connectivity, which is dependent on our products use case. What hardware specifications should you consider when choosing between 2G/3G/4G, Narrowband IoT, LTE-M1 technologies or should you already have a look towards 5G? Below is a brief overview of different cellular connectivity frequencies that will help with picking the right hardware.

Name
Frequency
Speed/Data rate

2G (GSM)

900/1800 MHz

50 - 500 kbps
3G (UMTS)
2100 MHz
200 kbps - 2Mbps
4G (LTE)
800/1800/2600 MHz
100 Mbps - 1Gbps
5G
30 - 300 GHz
1Gbps <
Narrowband IoT
3GPP Rel. 13, 14, 15 defined frequencies200 kbps
LTE-M
800/1800/2600 MHz
375 kbps/1 Mbps
The most frequently used technology is still 2G, it’s hardware is inexpensive and coverage is good. We have discussed different connectivity solutions before, therefore we will not go more in depth right now, but it is important to note that: 

  • Some carriers are closing down 2G and/or 3G networks
  • 5G is being tested and predicted to be released by 2020
  • NarrowBand IoT and LTE-M have recently been launched in developed cities, but no roaming protocol is in place yet

More on this can be found in our previous blog posts:

What hardware do I need?

When it comes to hardware, here is a short checklist to go through and some questions to keep in mind:

  • What controller am I going to use
  • What connectivity module suits my needs
  • How can I make sure that the signal strength is strong enough in the areas where my device will be used
  • What is the power consumption of the whole package?

In this stage of prototyping, development boards like Raspberry Pi, Arduino or Particle are handy and can help you get started with your product without big investments. Development boards also make it possible to connect a wide variety of different modules to test through and can be used even when moving forward from the prototyping phase to initial Minimum Viable Product (MVP) phase.

How to choose the right connectivity module?

IoT is quickly moving forward and choosing the right module that is built to last and is also future proof is important. The module choice mainly depends on the cellular technology you are going to use, but there are modules with some additions:

  • Fallback - have a plan B when connection with the preferred connectivity is failing. For example NB-IoT module with a fallback to 2G

  • Multiband - work within different frequencies

When ordering a module, most of the time you have the ability to decide if you are interested in multiband and/or fallback support. The downside is price, as fallback and multiband options can significantly increase the cost of the module.

Consumer devices typically have a short life cycle and are used in controlled environmental conditions, unlike IoT & M2M devices which tend to be required to manage vibrations, extreme temperatures or humidity. To minimize the risk of hardware failure you’ll want to go with a reliable and established supplier like:

These suppliers have a wide range of modules, and only some of the most popular ones are pointed out here:

Module
Supported frequencies
uBlox SARA-G350
850/ 900/ 1800/ 1900MHz
Telit GE910
850/ 900/ 1800/ 1900MHz
Quectel M66
850/ 900/ 1800/ 1900MHz
Quectel M95
850/ 900/ 1800/ 1900MHz
Quectel UG95
800/ 850/ 900/ 1900/ 2100MHz
SIMCom SIM5360A
850/ 1900MHz
SIMCom SIM800
850/ 900/ 1800/ 1900MHz

Which antenna provides the best connection?

When you need to choose the right antenna you should already have a plan of what cellular connectivity and modules will be used. There is no single antenna that will 100% guarantee a stable connection, choosing the right antenna requires experience and testing to find the perfect match. Important specifications to note here include:

  • Frequency

  • Gain

  • Beam angle

Antennas have a frequency range where they are supposed to operate, this range has to match the cellular technology and connectivity module specifications. There are multi-band antennas for modules with fallbacks and/or GPS that cover multiple frequencies.
You can once again have a look at the cellular table at the beginning of the post to make sure your antenna works in the right frequency range.

Gain is the performance indicator of an antenna, measured in decibel (dB). It describes how well input power is converted into radio waves and vice versa. Simply, you can say that the higher the gain the longer the range. But in the real world, it depends on many environmental factors such as obstacles and radio interference.
The laws of physics govern that high gain cannot be achieved with a small antenna and that is often one of the bigger challenges for IoT - how to provide a compact solution with good connectivity.

Often underestimated is the placement of the antenna. To get the maximum result of an antenna you will have to consider issues like mounting the antenna near metal which is interfering with the signal or bad placement that results in pointing the antenna beam angles towards the ground.

(Gain and antenna beam angle)
(Gain and antenna beam angle)

Finally, we have different types of antennas to consider.

  • Chip antennas - best option for very small form factors, delivers low frequencies even at a small size. But comes with midrange to low efficiency.

  • PCB antennas - can be a separate unit or directly printed onto the PCB. Their efficiency is good and increases with antenna size.

  • Patch antennas - can be mounted directly onto the module itself, making it compact. Comes with relatively good efficiency. Used most often in mobile phones and also IoT applications.

  • Dipole antennas - most widely used antennas. Omnidirectional meaning that the signal is emitted in all directions. Good efficiency and size relationship.

Whip antennas - flexible antennas that don’t easily break. The larger dimensions can be a blocking point for smaller IoT devices but it remains a good choice for vehicle tracking or similar applications.
 


A cheap and easy antenna solution for the first prototype is the Taoglas PC104 PCB antenna for 2G and 3G frequencies. Taoglas and Antenova are good quality manufacturers that are definitely big players on the market and they are recommended by 1oT.

Battery to power your product!

Whether an IoT device is gathering temperature readings in a forest or is buried into asphalt to capture data about car parking, it needs to be battery powered for up to 10 years without having a giant battery pack. We have to focus on power optimization not only from the hardware but also from the software side as very small power savings can lead to years of extra battery life. The development of batteries has been slow despite the fact that we are more and more dependent on them. This puts IoT product batteries into a challenging situation:

  • To be small in dimensions

  • To be inexpensive, to make IoT products affordable

  • Make it possible to monitor the battery conditions remotely

  • Avoid self-discharging as much as possible

The most frequently used batteries consist of electrochemical cells which convert chemical reactions to electrical energy.

Lithium-ion or polymer batteries are used due to their good power to weight ratio and dimensions. These are often found in phones, wearables, and IoT devices and are the most popular choices.

Type
Cell voltage
Energy density
Self-discharge
Alkaline
1.5v
600 kJ/Kg
Low self-discharge rate
Lithium Ion
3.6v
460 kJ/Kg
Moderate self-discharge rate
Lithium Polymer
3.7v
950 kJ/Kg
Moderate self-discharge rate

The listed ratings in the table are theoretical and depend on the environment. Also, it is important to note that even though a cell voltage can be 1.5v, it doesn’t mean your system has to run at this voltage. Most modules use a voltage range from 2.8-3.6v and connecting battery cells in parallel increases the voltage to the desired output while connecting in a series increases the capacity. Of course, there are a lot of other parameters that are important and need consideration but this already gives you some idea on what battery types are generally used.

(Battery in parallel and in series)

How to proceed past prototyping?

Prototyping’s purpose is to test out the product components and make sure that your hardware works as intended. The hardware used is usually never in the same form factor as your final product and it most certainly is a mess of wires, but the main idea is to have the functions working. Development boards are modular, affordable and easy to use but once you are scaling the costs and reliability of custom printed circuit board(PCB) makes a big difference.

When you are at the stage of producing custom PCB that have integrated circuits and modules you have tested before, you can be assured that these components work as intended.
As turning a prototype into a production unit is a very technical task, it is best to consult with experts in this field. The last thing you want is a high volume production of units that don’t work as intended.

Need help with your hardware?

We would love to help your hardware get connected! If you don’t have the expertise to build IoT hardware on your own or need help to troubleshoot connectivity problems, feel free to contact us at hacking [at] 1oT.mobi  

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