Battery-Optimized LPWA Connectivity: eDRX or PSM 

This is the first post in a two-part series examining the role of technologies that support low power wide area (LPWA) networks and how best to optimize device battery life that powers a large segment of IoT called Massive IoT. In this post, we examine choosing eDRX or PSM technologies.

One of the hallmark benefits of low power wide area (LPWA) networks is increased battery life savings, which can be optimized by choosing either eDRX or PSM technologies. 

LPWA networks are leveraged in cases of digital solutions that need to be deployed into the field for long periods of time. These, typically Massive IoT use cases, entail hundreds or thousands of devices dispersed across wide geographic areas and sometimes in difficult-to-reach locations. Ideally, these devices can last their entire lifecycle on a single battery, and, in some cases, these devices have lifecycles of 10 or more years. 

These simple devices typically wake, take a reading, transmit the data, and then return to sleep mode. Instead of continuously staying awake and quickly using battery life, they can do this through eDRX or PSM. 

eDRX for LPWA

eDRX (Extended Discontinuous Reception) is designed to improve the battery life of IoT devices by allowing them to stay in a low-power sleep mode for extended periods while still maintaining connectivity with the network. 

In standard DRX, a device periodically wakes up to check for incoming messages or data from the network. This wake-up period is relatively short and frequent, which can consume significant power. But in eDRX, the interval between these wake-up periods is extended, allowing devices to stay in a low-power sleep mode for much longer. Depending on the device’s configuration and application needs, this extension can range from a few seconds to several minutes or even hours.

In addition to the power savings of eDRX, this technology can also support maintained connectivity and scalability for IoT networks. The network load can be managed efficiently by spreading out the times when devices wake up and communicate with the network. This can reduce congestion and improve overall network performance. 

Ultimately, developer flexibility allows for programming a device how often to wake up and when, which creates a tailored approach to battery life optimization. 

What Are Some Challenges with eDRX?

With any technology, there are complexities and even a few hurdles to overcome. Specifically with eDRX, two are notable:

Implementation Complexity:

• Device and Network Coordination: Properly implementing and managing eDRX requires coordination between the device and the network. Ensuring compatibility and optimal configuration can add complexity to device firmware and network infrastructure.
• Firmware Development: Developing and maintaining firmware that effectively uses eDRX can be more complex than developing and maintaining simpler power-saving modes.

Network Support and Configuration:

• Operator Support: Not all network operators support eDRX, and those that do might have different configurations and capabilities. This can limit the deployment options for devices using eDRX.
• Configuration Variability: Different networks may offer different eDRX cycle lengths and configurations, requiring devices to adapt to varying network conditions.

It is important to note that—again, just like with any other technology—the partnerships chosen to deliver key benefits in LPWA, eDRX, or otherwise should support the requirements within the use case and have the knowledge and experience to optimize the benefits. 

floLIVE has direct carrier relationships, technical expertise and support, and ownership of the core network technology that allows for streamlined eDRX implementation.

Is eDRX a Must-Have?

While eDRX can benefit certain use cases where infrequent communication and extended battery life are priorities, it is not mandatory. The decision to use eDRX depends on the specific requirements of the application, including factors such as:

• Battery Life Requirements: If the device needs to maximize battery life, eDRX can be very useful.
• Data Transmission Frequency: If the application requires frequent data transmission or low latency, shorter DRX cycles or continuous connectivity might be preferred over eDRX.
• Network Operator Support: Not all network operators may support eDRX, so availability might be a factor.
• Device and Application Requirements: eDRX might be suitable or not, depending on the device’s capabilities and the application’s need for responsiveness.

Overall, eDRX is a tool to enhance power efficiency, but it is not a necessity for LPWA deployment. 

PSM for LPWA

The choice between eDRX or PSM can come down to how long a device sleeps and how deeply it sleeps. PSM (Power-Saving Mode) allows a device to remain registered with the network while entering a low-power state for extended periods, reducing the need for frequent reconnections and minimizing power consumption.

PSM allows for extended sleep periods through long idle times, where devices can remain in a low-power sleep state for days, weeks, or even months, depending on the application’s requirements. The device will wake up periodically to check for network messages and perform necessary tasks, such as sending data or checking for updates. All of this occurs while maintaining network registration, unlike traditional idle modes. This eliminates the need for re-registration upon waking up and thus saving energy. 

What are Some Challenges with PSM? 

The effectiveness of PSM depends on network operator support and configuration. Different operators may offer varying levels of support and configurability for PSM. Again, two notable hurdles can complicate leveraging PSM. 

Network Operator Support

• Variability in Support: Not all network operators support PSM, and those that do may have different configurations and limitations. This variability can impact the device’s ability to fully utilize PSM in different regions or with different operators.
• Inconsistent Implementations: Differences in how operators implement and manage PSM can lead to inconsistent behavior across networks, complicating deployment and operation.

Firmware and Software Complexity:

• Increased Development Effort: Implementing PSM in device firmware and ensuring it operates correctly with network infrastructure adds complexity to software development. This includes handling different sleep modes, wake-up triggers, and ensuring seamless communication with the network.
• Debugging and Maintenance: Diagnosing issues related to PSM can be challenging, as problems may arise from interactions between the device’s firmware, the network’s configuration, and the specific PSM settings.

It bears repeating that leveraging the right provider that can manage these complexities and overcome the hurdles through technology ownership and direct relationships with network operators. floLIVE is able to deliver and optimize the right connectivity and technology solution design to maximize the benefits of PSM. 

Is PSM a Must-Have? 

While PSM is a useful feature for extending battery life and reducing power consumption, its use depends on the specific requirements of your application and the characteristics of your LPWA deployment.

• Battery Life Requirements: If your application requires long battery life and can tolerate delays in communication, PSM is beneficial. Devices can remain in a low-power state for extended periods, significantly reducing power consumption.
• Communication Frequency: If your application requires infrequent communication with the network, PSM can help save power by minimizing the time the device spends in active mode. However, for applications requiring frequent data transmissions or low latency, PSM might not be suitable.
• Latency Tolerance: Applications that can tolerate higher latency in receiving downlink messages and can operate effectively with delayed responses can benefit from PSM. Real-time or near-real-time applications may need to avoid PSM due to the inherent delays.

In Our Next Post: Latency Considerations with LPWA

One important aspect of battery saving and LPWA networks is latency associated with data communication. LPWA, eDRX, and PSM are all great tools of technology, but if you’re sending your data halfway around the world and back, you’re not truly optimizing your battery life. 

In the second blog in this series, I’ll discuss how latency, packet gateways, and localized global data are the final keys to unlocking power-optimized connectivity. Want to discuss battery-optimizing technologies in the meantime? Reach out  – we’d love to talk!