The impact of the communication technology protocol on your IoT application’s power consumption

Connectivity is key to any Internet of Things (IoT) deployment. Many different communication protocols have been created over the years, allowing devices and servers to send each other data in new, interconnected ways. Each technology has its own strengths and weaknesses in terms of coverage, range, scalability, cost and network requirements that will address specific IoT use cases and applications needs.  When selecting a wireless technology for your IoT device, a few considerations must be taken into account: the maximum throughput, the distance range, the availability in the deployment zone, but also the power consumption. Indeed, some technologies can provide larger coverage, but they consume excessive energy. In this article, we will be studying the main communication protocols and their impact on power consumption.
 

What are the wireless IoT Connectivity Technologies available?

Wireless IoT Connectivity Technologies have a range from a few centimeters to many kilometers:

• Wireless Personal and Local Area Network technologies (WPAN\LAN) such as Bluetooth, ZigBee, 6LowPAN, RFID and Wi-Fi are ideal for short to medium range communication like home or indoor applications.
• Wireless Wide Area Network technologies (WWAN) are divided into two types: Cellular (3G/4G and 5G) and Low-Power Wide Area Networks (LPWANs), themselves split into licensed (LTE-M, NB-IoT EC-GSM) or unlicensed long-range technologies (LPWA LoRa, Sigfox and other). They are best suited for long-range communication such as smart meters, animal or assets tracking.  

Visual @ Industry Today 
 

Why does the choice of network influence the battery life?

An IoT application contains groups of sensors that inform another group of nodes called sensor nodes. These nodes are powered by a battery whose life-time is influenced by several factors, external from the battery technology, design and manufacturing quality:

• the nature of the application (remote location or not, pulse rate and frequency, etc.…)
• the chosen Wireless Communication Protocol (each communication protocols has its own consumption profile as we will explain later.)
• the module/chip that is used for the chosen Wireless Communication Protocol (the chip/module that allows the connection to the network uses more or less power depending on the manufacturers) and more broadly, the electronics design.
• and finally the necessary coverage range and the distance between sensor nodes. The distance between two nodes, the data rate and the message size all influence the transmission time, that in turn impacts the power consumption. Indeed, the higher the data rate, the less time is needed to receive/transmit the data, resulting in energy consumption reduction.  

Image @ ScienceDirect.com

For the project to be sustainable, the battery has to function for years. This is why the battery lifetime is one of the most important parameter in the design of sensor nodes for IoT applications. For the purpose of this article, we’ll be looking at Wireless Communication Protocol’s consumption. We won’t be going into the details of the consumption profile of each protocol’s module. If you’d like to know more about it, you can read this study by Mahmoud Shuker Mahmoud and Auday Mohamad: A Study of Efficient Power Consumption Wireless Communication Techniques/ Modules for Internet of Things (IoT) Applications
 

The impact of Connectivity Technologies on the power consumption

Wireless Personal Area Network (WPAN)

According to IoT Analytics’ latest “State of the IoT & Short-term outlook” update, the majority of IoT devices are connected through short-range technology: Wireless Personal Area Network (WPAN) that does not exceed a maximum range of 100m. Devices include Bluetooth-connected headsets for example, but also Zigbee and Z-wave connected devices mostly used in home applications such as building control systems, smart alarms, or smart thermostats but also Industry 4.0 applications.
ZigBee and 6LoWPAN protocols are designed for low power consumption applications such as low power wireless sensor networks. However, the transmission time for those protocols is longer than the low power Wi-Fi, due to its low data rate (250 Kb/s). The average consumption profile is therefore considered as low to medium depending on the application and the module used.
 

Wireless Local Area Networks (WLAN)

Next up is Wireless Local Area Networks, a network that enables connectivity of up to 1 kilometer. In this category, Wi-Fi is the most common standard. The technology is supporting devices such as home assistants, smart TVs, and smart speakers and is sometimes used in industrial settings like factories. Wi-Fi was historically designed for laptops or PCs, where the power requirements were not so important. It was deemed too power hungry for battery-powered smart objects which led manufacturers to develop new standards for the Internet of Things. New generation, low power Wi-Fi operates at much higher data rates ranging from 1 Mb/s to 54 Mb/s. This allows Wi-Fi enabled sensors to spend very little time with actual transmission or reception. The chips ‘sleep mode’ power consumption was also greatly reduced (convenient for IoT applications since these devices are mostly in the sleep state) thus reducing the modules overall power consumption.  
 

Low Power Wide Area Networks (LPWAN)

IoT applications’ requirements have driven the emergence of Low Power Wide Area Networks (LPWAN) and we can expect a massive growth in the number of IoT devices connected through them. According to McKinsey, 100 percent of the population should have LPWAN coverage by 2022 and by 2025, it is expected that more than 2 billion devices will be connected through LPWAN.

The technology offers low power, long range (up to 10–50 km in rural zones and 1–10 km in urban zones) together with low-cost specifications.  Four main competing standards are currently sharing the market: Sigfox, LoRaWAN, LTE-M and NB-IoT. They are presently being rolled-out worldwide with more than 25 million devices already connected, the majority of which are smart meters. These protocols may be based on cellular technology, such as LTE-M and NB-IoT or radio-based (LoRa, Sigfox),they can be licensed (NB-IoT, LTE-M) or unlicensed (LoRa, Sigfox) which also differentiates their availability and prices.

In long range connectivity, LoRaWAN requires more transmission time compared to small range connectivity protocols because of its low rate data rate. However, the optimizations brought to power savings mode, small data maximization, and flexible sleep all reduce the power consumption of devices which makes LoRaWAN a good candidate for numerous IoT applications.
 

Cellular technology (2G, 3G, 4G and 5G)

Before the advent of LPWAN, cellular technology (2G, 3G, and 4G) was the only option for long-range remote device connectivity (up to 100km). The new, much talked about, 5G technology that is currently being deployed, promises a massive bandwidth and extremely low latency which could favor its adoption. Cellular connectivity has historically been focused on range and bandwidth at the expense of power consumption. The high amount of data produced by devices was hard to process quickly and the amount of time between when data is sent from a connected device to when it returns to the same device—the latency—was high. However, new cellular technologies like 5G transmit data about 10 times faster than 4G, promising ultra-low latency and lower power consumption.
 

Wireless Neighborhood Area Networks (WNAN)

Finally, somewhere in between WLAN and long-range technologies, lies Wireless Neighborhood Area Networks (WNAN), a medium range technology that covers areas between 5-10 km with its typical proponents, Mesh networks (Wi-Sun (6LoWPAN), JupiterMesh or ZigBee-NAN). The technology can be used as an alternative for LPWA/Cellular (e.g, in Utilities Field Area Networks) or as a complimentary element (e.g., for remote metering where other protocols do not have sufficient range to be implemented) such as gas metering applications).
WNAN networks are generally deemed as high-energy consumers but mesh technologies such as Wi-SUN can provide high data rates and low latency. Additionally, Wi-SUN modules use less power for listening which enable customers to configure devices to listen frequently and still maintain a long-life.

The table below shows a comparison between the main protocols that may be used in IoT applications  

Choosing a connectivity solution for your IoT device has serious consequences on the choice of the components of your application, on the performance of the connected object and on its energy consumption. It’s important to spend some time properly digesting the options and thinking about the possible solutions. These connectivity solutions do not come free either and the expenses involved with the choice of one or the other of the communication protocols will have a direct impact on your business case and on the commercial attractiveness of your solution.

Telecom operators offer a wide panel of solutions. Some cellular network operators will even allow the deployment of unlicensed solutions such as LoRaWAN since they remain very interesting for connected devices communicating small amounts of data and needing a great autonomy. Regarding the choice of a battery, there is no ready-made solution, and choosing between the network protocols is a decision based on a compromise between the device’s requirement and strategic orientations that we want to give to the IoT solution. If you need help choosing a battery and calculating its lifetime according to your choice of communication protocol, our experts will happily advise you, making sure your solution can give the best of its capacity, for the longest possible time. Feel free to get in touch!