Wireless Technology Overview for IoT

By Walter N. Maclay, President, Voler Systems

Contributed By Digi-Key's North American Editors

The Internet of Things (IoT) is both known and unknown in the modern world. It is a common term for individuals in the tech industry and corporate world, but only seldom heard by the general populace although it’s part of their daily lives. IoT is the connectivity of physical objects such as devices, vehicles, buildings, electronics, and networks that allows them to interact, collect and exchange data. It applies to millions of different things, including updated traditional products previously not connected to the internet.

This article will take a look into the many ways these devices can communicate wirelessly.

Three ways to get data into the cloud

One challenge of IoT is getting data from the device’s sensor to the cloud, where that data is used, processed, and stored. The ubiquitous use of Wi-Fi and Bluetooth through smartphones, along with the widespread availability of cell towers and public Wi-Fi access points, provides more access to the cloud for IoT sensors than ever before. There are three basic ways to get data to the cloud.

Sensor to gateway to cloud. In some applications, it is optimal to send the sensor data to a gateway which then transmits the data efficiently to the cloud. Depending on the application needs, the gateway can range from simple relay systems to “smart” platforms that perform more compute-intensive functions called “edge processing”. Devices like parking lot sensors and desk utilization sensors typically rely on gateways to transmit the data. Wi-Fi is an example of a gateway. For in-home use, you need to install a Wi-Fi gateway. In public locations where the gateway is already installed, Wi-Fi operates directly to the cloud. Other types of wireless communications, such as Bluetooth, require a gateway. An example of Wi-Fi in the home is Hatch Baby Grow, a smart changing pad and connected scale. It uses Wi-Fi to transmit data from the scale in the changing pad to the home internet. The parent and pediatrician can track cloud-based information through either an Android or iOS application.

Sensor to cell phone to cloud. In some cases, the gateway can be a cell phone. Smartphones with Wi-Fi or Bluetooth capability act as gateways to send data to the cloud. For instance, Voler helped with the development of earbuds that monitor the elderly for balance. They have Bluetooth LE wireless transmission to a smartphone where there is an associated app. The data is also sent to the cloud from the smartphone where further processing can be done and data can be shared.

Smart device directly to cloud. The sensor can connect directly to the cloud using technology such as NB-IoT, LTE-M, or LoRa. These technologies transmit for miles at very low power, as long as the data rate is low. They connect to the internet through equipment usually installed at cell towers. They work much the same way cell phones work except the data rate and power are much lower. There is a monthly charge, but it is typically very small.

Factors to consider in planning an IoT wireless communication strategy include: how much data will be transferred, how far the data source is from the internet, how much power is required, and how high the cost is for the service, if any. The widespread use of smartphones and the choice of Wi-Fi or Bluetooth radio standards offer very convenient connectivity. Newer standards, such as NB-IoT and LTE-M open up more options for the future Internet of Things.

Why are new technologies needed?

IoT is still evolving. With every iteration comes lower power consumption, longer wireless communication, and better features. New devices can take advantage of the new technology and provide better performance.

What should be considered for trade-offs

Every time Voler designs a wearable device or any battery-operated device, customers require it to:

  • Operate for a long time
  • Transmit lots of data a long distance
  • Have a tiny battery

There are trade-offs to these competing requirements. Engineering is about trade-offs. Consider the system functionality required and make the engineering trade-offs necessary to provide optimum performance in accordance to the system requirements. It is important to simultaneously provide a satisfactory user experience. The result is a design with the best compromises among the many choices.

Trade-off considerations

  • Data rate
  • Transmission distance
  • Battery size
  • Cost
  • Licensed vs. unlicensed spectrum
  • Carrier deployed vs. customer deployed
  • The density of end devices
  • Where it gets deployed
  • Firmware updates
  • Drivers for your OS
  • Component/module selection
  • Antennas
  • Maturity of technology

Voler recently worked with a start-up to improve the battery life of their connected product. It was based on Murata’s impModule™ with an Arm® processor and Wi-Fi transceiver. They needed a battery life of many weeks, and it was less than one week after prototyping. Voler revised the code to meet the needed battery life. The original code was not working as intended.

In wireless transmission, three things must be managed: the power required to transmit, the data rate, and transmission range. Choosing the right wireless standard is important. Refer to the table below when selecting a wireless standard for the IoT device being designed. The table lists the common wireless standards used for IoT devices, along with their characteristics.

Table of common wireless standards and their capabilitiesTable 1: Common wireless standards and their capabilities. (Table source: Voler)

Different wireless standards require very different levels of power. The required power depends on the data rate and range of transmission. For example, referring to Table 1, a device may require 120 mW of power to transmit 100 bits of data per second one kilometer using LTE Cellular. But using Bluetooth LE to transmit 1 meter, a device may only need 0.15 mW of power.

Comparison of IoT wireless standards

Table of comparison of wireless IoT standardsTable 2: A comparison of wireless IoT standards. (Table source: Voler)

Power requirements for popular wireless options

If a device is required only to transmit data as far as 10 meters, BLE and Bluetooth are sufficient. But IoT devices for industrial and commercial purposes such as inventory management or wearable devices for health monitoring may require longer-range communication, such as NB-IoT or LTE-M. If a device sends a lot of data, such as a video camera, BLE cannot handle it. High-power choices such as Wi-Fi and LTE are required.

On the other hand, cellular wireless protocols NB-IoT and LTE-M allow IoT devices to transmit data to distant locations at low power. The same is true for SigFox which can transmit data as far as 50 kilometers. But unlike cellular standards with a high data rate, SigFox can only transmit up to 300 bits of data per second.

Private vs. public network

A private network has a gateway installed and controlled by a provider for one or a limited number of users.  A public network has a gateway that many users can use by paying a monthly fee. An example is cellular service.

Public networks require infrastructure to be installed, such as cell towers. Cell phones are popular and can easily roam because of the widespread installation of cell towers. SigFox and LoRa have limited infrastructure in place in the USA, so a device using this technology would not work in most places. LoRa does have the option of a private network using a gateway.

In 2019 the installation of infrastructure for NB-IoT and LTE-M passed the point where 90% of the United States population is covered. It is approaching the availability of cellular coverage. Although it has been around for years, finally, this technology can be used in new devices. The infrastructure is in place in most major countries in the world as well. Expect a rapid increase in the use of NB-IoT and LTE-M. Sigfox and LoRa are way behind in installation of public infrastructure.

Below is a summary of the private and public wireless options:

Private

  • Both ends of the communication owned privately
  • It can be installed anywhere
  • Unlicensed spectrum
  • Cost to install base stations and endpoints
  • No monthly fee

Public

  • The network owned by provider – for example, cellular
  • Only works where base stations exist
  • Easy roaming
  • Licensed spectrum
  • A monthly charge for the use of the network

When will battery technology improve?

If batteries were better, these trade-offs would be simpler. Chemical energy storage is approaching the limit of its efficiency. There is, however, a lot of research being done on higher density and better safety.

If batteries had progressed like semiconductors over the last 50 years, you would have a battery the size of the head of a pin that would cost a penny and would power your car. Needless to say, that technology is not even remotely close and never will be. Therefore, devices are limited by the space required for the chemical storage of energy.

Today’s batteries are about 10% of the ultimate in chemical energy storage, which would be something like gasoline. However, gasoline has a problem with safety. Another more efficient option is nuclear energy, but there again would be a safety issue not to mention a portability problem. There will be incremental improvements in batteries in the future, but the changes will be slow.

Cost considerations

Many IoT device manufacturers underinvest in security to keep their products affordable and accelerate time-to-market. Integrating security during the development stage can significantly add cost and time to the development. However, building IoT devices with weak IoT security can result in more damaging consequences not just to the customers, but also to the manufacturer’s brand — in terms of lost productivity, legal/compliance fines, damaged reputation, and monetary losses.

The wireless standard chosen for IoT devices can significantly influence its performance, usability, security, and reliability. The best-fit standard for an IoT device depends upon its application. Knowing the purpose of the device can help determine the key requirements for building it, such as how much power it needs to operate efficiently, how fast it should transmit data, and how long the battery needs to last.

Voler System’s team of IoT device development experts can guide a designer through choosing the right wireless standard for IoT machines. Contact an IoT expert now to learn more about choosing the right wireless standard for any IoT device design.

Disclaimer: The opinions, beliefs, and viewpoints expressed by the various authors and/or forum participants on this website do not necessarily reflect the opinions, beliefs, and viewpoints of Digi-Key Electronics or official policies of Digi-Key Electronics.

About this author

Walter N. Maclay, President, Voler Systems

Mr. Walt Maclay, President and founder of Voler Systems, is recognized as a domain expert in Silicon Valley technical consulting associations. He has spoken on sensors, wearable devices, wireless communication, and low power design. He was President of the Professional and Technical Consultants Association (PATCA). He is a senior life member of the Institute of Electrical and Electronic Engineers (IEEE) and a member of the Consultants Network of Silicon Valley. Mr. Maclay holds a BSEE degree in Electrical Engineering from Syracuse University.

About this publisher

Digi-Key's North American Editors