Narrow-band IoT (NB-IoT) is one of several technologies that promise to expand the market for low-power, connected devices, and sensors. This class of devices exposes new application opportunities. They are associated with long service life, small data payloads, and infrequent communications. The size of the market opportunity is set to grow even further with innovative technologies related to 5G’s Internet of Everything and new aspirations for 6G.
However, there is an opposite dimension to the issue of size that relates to processing capabilities, energy consumption, and the communications traffic these devices exchange over mobile networks. In each of these cases, the goal is to minimize these measures. As an example, reductions in the scope of processing capabilities result in lower-cost devices. That eases the path to adoption because connected devices are now more affordable. Standardization can amplify this trend thanks to economies of scale.
In terms of other measures, low energy consumption and low traffic intensity are beneficial for operational costs. A lower power of data transmission and network signaling can also reduce the impact on network resources, which must be shared with many other users. In aggregate terms, low energy consumption can also be good for sustainability.
Optimization for Minimal Sensors
In the case of minimal sensor applications, design and engineering choices can have a material impact on energy consumption and sustainability. There are ways to optimize the bootstrapping process when a sensor and application form a communications link. This involves a management application handling registration functions and setting up the data structures for operational use. Only having to transmit readings reduces the communications and coding impact on the constrained device.
Another optimization that can improve energy usage is the choice of content serialization formats. For example, at one end of the spectrum, a sensor reading can be transmitted in XML format and require the parsing of complex string information for application processing purposes. The other end of the spectrum involves the use of JSON and CBOR formats. In comparison tests, the transmission of a single reading from a humidity sensor demonstrates the potential to reduce payloads by a factor of 5. The smaller JSON and even smaller CBOR formats also help to reduce the computational resources and energy consumption involved in serialization and deserialization tasks.
Putting Devices to Sleep
Another set of approaches to improving energy performance and extending battery-powered remote devices’ service life uses sleep mode techniques. This relies on a pre-arranged sleep schedule so that devices poll their communications networks only when ready to send a reading.
The 3GPP family of standards specifies a Power Save Mode (PSM), allowing a device to avoid paging the network and sleep for intervals as long as 413 days. The main drawback is that the device is unreachable by the network during this time.
Longer-term innovation focuses on zero-energy techniques. These can reduce power consumption by factors of 100x–1000x, thereby paving the path towards 1 trillion mobile and connected things.
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