Greening by ICT: IoT Sustainability by Design

“Greening by ICT” is a term that is often used to illustrate how information and communications technologies (ICT) can enable sustainability. In the case of IoT applications, access to operational data via remote monitoring technologies can be a massive boon to facilities managers. They can track the status of mission-critical machinery or dispatch supplies when chemical-treatment stock levels in unattended, remote sites are close to depletion.

Two approaches to promoting sustainability in the (ICT) market involve the efficient use of resources and avoiding waste. When applied to IoT systems, these concepts translate into approaches to optimize communications between applications, communications networks, and end-point devices. Sustainability is enhanced when the three function in harmony. If communications between networks and devices can be coordinated, it is possible to design for energy conservation. However, suppose devices remain connected to the network rather than sleep when no applications are interested in communicating with these devices. In that case, this results in non-optimal consumption of devices (e.g., battery) and network resources. Likewise, if applications repeatedly poll devices when these devices have no new information to share, this also results in non-optimal use of resources. This is also the case when devices are sleeping and not connected to the network. These usage scenarios can also potentially consume network resources unnecessarily, which can impair services to other users sharing the network.

Who Is Talking to Whom?

‘Mobile Originated’ is a communication mode involving a connected device initiating communication with an application in the network. For example, this might be a sensor that periodically transmits readings to an application hosted in the cloud. Mobile-originated devices can enter Power Saving Mode (PSM) when not transmitting to conserve power. When in PSM, the device is disconnected from the network but remains registered. When the device wakes up (e.g., to transmit its next sensor reading), it can do so without re-registering to the network. Devices can remain in PSM for periods of hours and as many as 400 days at a stretch. When in PSM, the device is unreachable to applications in the network. Therefore, PSM is best suited for mobile-originated devices that initiate communication with applications.

A different mode of operation, referred to as ‘mobile terminated,’ applies to situations where an application in the network initiates communication with a connected device (e.g., to send commands to an actuator device). This can be the case in logistics, asset tracking, industrial automation, and closed-loop control use-cases. To conserve power, a mobile terminated device relies on a technology known as Extended Discontinuous Rx (eDRX). With eDRX, a device can enter a low power mode in which it listens for an indication of pending mobile terminated data periodically without maintaining a full network connection. If an indication of pending mobile terminated data is detected, the device can re-establish a full network connection to receive the data. Hence eDRX is better suited than PSM for mobile terminated device power savings.

Interworking 3GPP Cellular Capabilities in IoT Systems

When considering PSM and eDRX capabilities in practical deployment scenarios, there is a need to coordinate alternative design approaches at scale. Consider the need to organize schedules for one group of devices using mobile-originated communications and other sensor and applications programmed for mobile-terminated communications. This is where 3GPP and oneM2M standards are complementary and can ease the burden on application developers. 3GPP focuses on cellular communications devices and networks. oneM2M is a middleware standard that acts as an abstraction layer between IoT applications and the underlying communications networks and connectivity protocols associated with issuing commands and gathering data to/from IoT devices.

3GPP standards define a northbound API for exposing underlying cellular network functionality such as configuring PSM and eDRX timers for devices. oneM2M has its API for interworking with 3GPP networks, which translates 3GPP data structures into a format that IoT developers can use as part of their IoT toolkit. Therefore, they can define sleep schedules in the context of their application requirements because oneM2M abstracts the complexity associated with underlying network details. In addition, oneM2M can aggregate and align schedules of devices and the different applications needing to communicate with these devices. oneM2M can then configure device PSM and eDRX timers via the northbound API of the cellular network to ensure mobile originated and mobile terminated devices connect to the network at the optimal times to send and receive data from network applications. This is one benefit of relying on 3GPP and oneM2M standards.

The complementary nature of 3GPP and oneM2M standards extends the idea of managing networks responsibly as encouraged by the GSMA through its IoT connectivity guidelines to ‘do no harm’ to mobile networks.