Rapid Growth in the Internet of Things is Threatened due to the Energy Challenge
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Dr Ambuj Varshney
We are witnessing rapid growth in the number of Internet of Things (IoT) devices. Many predictions state that we already have billions of IoT devices deployed globally, and this number is fast increasing, and it will approach a trillion soon. IoT enables numerous applications, and they are having a transformative impact across application domains and industry verticals, driving the massive growth in the number of IoT devices.
Applications enabled through IoT already impact our lives: For example, we use fitness trackers to track our movements and health parameters. Electronic devices such as thermostats in our homes can help us maintain the temperature to be comfortable. Even outside of our homes, IoT devices are starting to have a significant impact. In industrial environments, IoT devices that are equipped with accelerometers track machine vibrations, infer machine health, and predict and prevent expensive breakdowns.
However, despite the massive recent growth in IoT devices, In this article, I argue that there is a significant challenge related to the energy consumption that threatens to restrict or even block this massive growth. I argue, and believe, that it can prevent us from unlocking trillions of dollars of economic value enabled through numerous applications that are enabled through IoT.
What is the energy challenge of IoT devices?
Most of the IoT devices today are energy-expensive. A typical IoT device consumes a few to tens of milliwatts of power consumption. This figure still represents substantially lower power consumption than a device such as a smartphone. However, this power consumption figure is prohibitively large. IoT devices commonly operate on tiny batteries such as AA/AAA sized batteries, coin cells, or other such batteries with minimal capacity. Due to the high power consumption, when operating on these tiny batteries, the IoT devices require either frequent (within a few days or a month or two) replacements or charging of these exhausted batteries.
Why are the limited lifetime and frequent replacement of batteries a significant challenge for the growth of IoT devices?
Many IoT devices operating on batteries present several challenges: First, replacing exhausted batteries on billions of IoT devices would significantly challenge. It may be further tricky as many of these IoT devices may be located in hard to reach places such as below bridges or in extreme environments in factories, where getting access to these devices to replace the exhausted batteries might not be straightforward.
Second, commonly employed batteries on IoT devices use toxic chemicals in their chemistry. Disposing of billions of depleted batteries can also negatively impact the environment, which influences the overall sustainability of the environment. Third, the energy-expensive operation requires operation on bulky batteries such as AA/AAA sized batteries. This limits the form factor, as the sensors are usually bulky, making it challenging to realise novel form factors such as sticker form factor sensors.
Finally, operation on conventional batteries can also limit the reach of IoT devices. It can be difficult to deploy such sensors in challenging environment, such as inside the wall or at extreme heat where batteries may not perform well or might be challenging to replace batteries altogether.
What is the reason for the high energy consumption of IoT devices?
To understand the reason why present-day IoT devices are so energy expensive, we look into their architecture. We find that their architecture has largely remained unchanged over the past two decades. IoT devices follow a pipelined architecture similar to as shown in the figure below:
A typical IoT device operates in the following manner: The device senses a physical phenomenon. Then, it processes the sensor reading and communicates these sensor readings to a powerful device. Consequently, the IoT device performs these operations in a series of steps. In the first step, it uses a sensor to track these parameters, then it amplifies the sensor signal, transforms it into the digital domain using an ADC, the digital representation of the sensor value is locally processed by the microcontroller, and finally, the IoT devices communicates the sensor reading using a radio transceiver (such as those support standard of ZigBee, LoRa, BLE) to a more powerful device.
To further elaborate on the operation of this architecture, we look at the specific case of an activity tracker: An activity tracker uses an accelerometer to detect our motion. The signal from the accelerometer is digitised using an ADC. Some processing such as a machine-learning algorithm is performed to infer steps. Finally, the information about steps walked or other classified motion is transmitted to a powerful device such as a smartphone.
So what makes this architecture to be energy expensive?
There is a significant asymmetry in the energy consumption between different components of the architecture. We find that over the past two decades, the sensors have become exceedingly energy efficient. However, the rest of the architecture is significantly more energy-expensive when compared to sensors. This large asymmetry in performing sensing, computation, and communication causes the overall power consumption of the IoT devices to be high and forces them to operate on bulky batteries with a minimal lifetime. In fact, the radio consumes the most energy on these devices. Performing wireless communication is typically 100–1000 X more energy-expensive when compared to processing or sensing operation on IoT devices.
Conclusion
We described the energy challenge of IoT devices and looked at the growing energy asymmetry between various components of the architecture. In the following article, we will look at possible solutions and directions to overcome the energy challenge of IoT devices. We will also look at the implications of overcoming the energy challenge which opens up the exciting potential of battery-free Internet of Things or opening new form factor for IoT devices.
BIO: Dr Ambuj Varshney is a researcher and developer who has been working in the area of Internet of Things and Embedded Systems for more than ten years. His doctoral dissertation tackled the energy challenges of embedded devices. His doctoral dissertation was awarded the prestigious 2019 ABB Research Award. He has studied and worked at leading universities: Uppsala University, Royal Institute of Technology, and the University of California, Berkeley. His research contributions have been published at flagship and selective scientific venues of embedded systems, mobile computing and the Internet of Things. Before embarking on an academic path, he worked as a software engineer at NXP Semiconductors working on protocol stacks for wireless embedded systems.
