The Importance of eDRX and PSM for cellular IoT deployments

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Extended Discontinuous Reception (eDRX) and Power Saving Mode (PSM) are two key technologies that enhance the battery life of IoT devices.

Pat Wilbur

June 5, 2025

In the evolving landscape of cellular IoT, efficient power management is critical for the success of battery-operated devices. Extended Discontinuous Reception (eDRX) and Power Saving Mode (PSM) are two key technologies that enhance the battery life of IoT devices, ensuring they remain operational for extended periods without frequent battery replacements. In this post, we explain the necessity of eDRX and PSM in cellular IoT deployments and how they contribute to the efficiency and sustainability of IoT solutions.

Understanding eDRX and PSM

Extended Discontinuous Reception (eDRX)

eDRX is a feature that allows IoT devices to reduce the frequency of communication with the network, thereby conserving battery life. It enables devices to "sleep" for longer intervals between listening for network messages. This is particularly useful for applications where data transmission is infrequent, such as in smart meters or environmental sensors.

In eDRX mode, the device’s radio periodically wakes up to listen for messages (paging), allowing for a balance between power saving and responsiveness. This makes eDRX ideal for scenarios where the device needs to receive occasional downlink data but can tolerate some latency. For example, environmental sensors that report data at regular intervals or smart meters that need to be reachable for configuration updates can benefit from this approach. The application processor can continue to operate independently, handling sensor readings or other tasks that don’t require network connectivity until the next scheduled wake-up.

Power Saving Mode (PSM)

PSM is a feature that puts the modem into a low-power state when it is not actively communicating. This mode significantly reduces power consumption by turning off certain components of the modem that are not needed for ongoing activities. For example, it may switch off the Wi-Fi radio or reduce transmission power during idle periods. PSM is crucial for battery-powered devices deployed in remote or hard-to-reach areas where replacing batteries frequently is impractical.

While in PSM, the device’s radio is completely switched off for both sending and receiving, though the device remains registered with the network. This deep sleep state maximizes battery life but comes at the cost of responsiveness—the device is unreachable by the network until it wakes up, either on a scheduled timer or when it needs to send data. PSM is best suited for use cases like remote sensors or asset trackers that send data infrequently and do not require regular downlink communication.

How eDRX and PSM work together

Both eDRX and PSM are designed to maximize battery life by minimizing the active time a device spends communicating with the network. They are specified in LTE-based IoT standards, including NB-IoT and LTE-M, and are primarily used for applications where long operational life is more important than instant responsiveness.

Key similarities

Both modes allow the device to remain registered with the network, so there’s no need for time-consuming network reattachment when waking.
Both are essential for IoT deployments where devices communicate infrequently.
Device modules must support and properly configure eDRX and PSM to take advantage of these features.

Main differences

eDRX offers “light sleep” with periodic wake-ups for network paging—providing moderate downlink latency and suitable for devices that need to receive data occasionally.
PSM acts as “deep hibernation,” significantly extending sleep periods and maximizing power savings, but making the device unreachable until it wakes up—ideal for devices that mostly send data and seldom require downlink communication.

Typical use cases

eDRX: Smart meters, environmental sensors, or other devices needing occasional network reachability and tolerable latency.
PSM: Remote monitoring devices or asset trackers that report infrequently and prioritize battery longevity over immediate responsiveness.

By understanding and combining these modes effectively, IoT deployments can achieve a tailored balance between battery life and communication needs, supporting a wide range of use cases and environmental challenges.

Benefits and trade-offs of Power Saving Mode (PSM) in IoT devices

PSM brings a host of advantages for IoT deployments, especially when energy efficiency is a top priority. By allowing devices to enter a low-power “deep sleep” state, PSM minimizes unnecessary energy drain and helps extend battery life dramatically. Devices can remain inactive for anything from a few seconds to several days, tailored to the device’s duty cycle and network settings. This makes PSM especially valuable for smart meters, agricultural sensors, or other devices that send data only occasionally.

However, the enhanced power savings come with a few trade-offs. Perhaps the most significant is increased downlink latency—since the device is offline for extended periods, it can’t receive messages or commands instantly. This makes PSM less suitable for applications that depend on real-time or frequent two-way communication, like emergency alerts or remote control systems. In short, while PSM is a powerful tool for maximizing battery life, it’s best reserved for scenarios where immediate responsiveness isn’t critical.

Comparing eDRX and PSM: How sleep duration, reachability, and communication patterns differ

While both eDRX and PSM serve to conserve battery life, they do so in distinct ways, each impacting device behavior and network interaction differently.

Sleep duration

eDRX can be thought of as a light nap—devices wake up periodically, maintaining relatively short sleep intervals set by the eDRX cycle. This allows devices to check in with the network more frequently. In contrast, PSM is closer to a deep slumber, enabling much longer sleep intervals (sometimes stretching to days, thanks to timers like T3412 in NB-IoT). Devices in PSM can remain inactive for extended periods, significantly reducing power draw.

Reachability

When operating in eDRX, a device is intermittently reachable. It periodically becomes available to receive data during scheduled listening windows. This means that downlink messages can reach the device, although some delay may occur if the timing isn’t quite right. On the other hand, a device in PSM is effectively offline until it decides to wake up or its timer expires. During this deep sleep phase, it cannot receive incoming data, and any messages sent to it are typically stored by the network until the device reconnects.

Communication patterns

eDRX strikes a balance between power efficiency and responsiveness. Devices using eDRX are well-suited to scenarios where occasional two-way communication is necessary, such as smart meters that may need to receive firmware updates or commands while also sending periodic readings. PSM, meanwhile, is optimized for use cases with infrequent uplink communication and very little need for downlink interaction. Think of remote environmental sensors or asset trackers that only report back occasionally and don’t require immediate command responses.

In short, your choice between eDRX and PSM hinges on how often your device needs to communicate and how responsive it must be to incoming messages. For some applications, a quick “catnap” (eDRX) is plenty; for others, “deep hibernation” (PSM) is the key to pushing battery life as far as possible.

Key events and timers in PSM operation

When a device enters Power Saving Mode (PSM), a series of events and timers come into play to manage how and when the device communicates with the network. Here’s how it typically unfolds:

Requesting PSM: The device initiates the process—typically during attachment to the network or when updating its tracking area—by proposing two key timers:
- T3324 (Active Time): This sets the window during which the device remains reachable before entering deep sleep. Essentially, it dictates how long the device will wait in a semi-active state, checking for messages or pages from the network.
- T3412 (Tracking Area Update Timer): This determines how long the device can stay in PSM before it must “check in” with the network again. Once T3412 expires, the device performs a Tracking Area Update, letting the network know it’s still present.
PSM duration: The actual period the device spends in deep sleep mode is calculated as the difference between T3412 and T3324. During this time, most radio components are switched off, and the device is not reachable by the network.
Network’s response: The network may approve or modify these timers based on its own policies and technical limitations. Each mobile operator may have unique restrictions regarding the maximum allowed PSM duration, so it’s important to verify the exact limits for your deployment.
While in PSM: The device enters a deep sleep state to maximize energy savings. It retains its network registration but cannot send or receive data until it “wakes up.” Most networks buffer any incoming messages (up to a minimum defined by standards like those from 3GPP) until the device becomes reachable again. Notably, devices can often wake early if needed, without re-establishing a full network connection.

Developer note: While in PSM, some device interfaces—such as the AT command channel—may not be available, so plan accordingly when designing your system’s behavior during these low-power intervals.

Key considerations for using eDRX and PSM

Device power source

Battery-operated devices: eDRX and PSM are particularly beneficial for battery-operated devices. If your IoT deployment relies on batteries, these power-saving features can drastically extend the device's operational life.

Non-battery devices: For devices connected to a stable power source, the need for eDRX and PSM is less critical but can still contribute to overall energy efficiency and cost savings.

Carrier dependency

Network compatibility: The effectiveness of eDRX and PSM can vary depending on the carrier. Different carriers have specific settings and support levels for these features, which can influence the device's behavior and connectivity performance.

Firmware updates: To ensure optimal performance, it is important to keep the modem's firmware up to date. Consult with your Field Application Engineer (FAE) to follow best practices and access the latest firmware versions.

Connectivity trade-offs

Potential Issues: While eDRX and PSM improve power efficiency, they may introduce challenges in network connectivity, such as delays in inbound communication. Proper configuration and testing are necessary to balance power savings with connectivity requirements.

Network requirements

Request eDRX Requirements: To ensure proper operation, you need to request the eDRX requirements from the network and set your device to match. Different networks have varying eDRX configurations, and aligning your device settings with the network’s specifications is crucial for optimal performance.

Power consumption management

Energy efficiency: By reducing power consumption during idle periods, eDRX and PSM help in lowering electricity costs and minimizing the environmental impact of network operations.

Battery life extension: For battery-powered devices, these features are essential in extending the time between battery replacements, reducing maintenance costs, and enhancing the reliability of IoT solutions in remote areas.

Additional strategies for maximizing IoT device battery life

While eDRX and PSM are foundational for reducing power consumption, they're just part of a broader set of best practices you can adopt to maximize battery life in your IoT deployments.

Optimize device connectivity settings

It’s important to tailor network configurations—such as eDRX cycles and PSM timers—according to the specific needs of your application. For instance, a device that sends infrequent updates can benefit from longer sleep intervals, while latency-sensitive applications may need to strike a balance between responsiveness and power savings.
Keep in mind that network providers may have their own parameters or limitations, so coordination with your provider is crucial.

Select efficient hardware and components

Choose components that are designed for low-power IoT operation. Many modern microcontrollers, such as those from Nordic Semiconductor or Texas Instruments, offer advanced sleep modes and efficient wakeup mechanisms.
Make use of sensors, radios, and peripherals that support energy-saving features.

Implement smart firmware and duty cycling

Write firmware that minimizes unnecessary processing. For example, batch sensor readings or transmissions to reduce the frequency of network activity.
Duty cycle both hardware and software, ensuring that the device spends the majority of its time in low-power states.

Leverage data compression and edge processing

Compress data or process information locally on the device before sending it to the cloud. This reduces transmit frequency and duration, which in turn conserves battery life.

Choose the right metwork technology

Different cellular standards—like LTE-M and NB-IoT—offer varying trade-offs between power consumption, coverage, and data rates. Evaluate which technology best aligns with your deployment’s requirements.

Test and iterate

Conduct real-world battery life tests using your actual workload and update configurations as needed. Tools from providers like Keysight or Anritsu can help you measure and optimize power performance during development.

By combining these methods with eDRX and PSM, you can achieve the longest possible battery life for your IoT devices—especially when deploying at scale or in hard-to-reach locations.

Choosing between eDRX and PSM: Which is right for your IoT device?

Selecting between eDRX and PSM depends largely on how responsive your device needs to be, and how aggressively you need to conserve battery power.

When to Choose eDRX

If your device must remain somewhat reachable for network-initiated messages—think smart meters, livestock trackers, or environmental sensors that only need moderate reporting frequency—eDRX is generally the better fit. It allows your device to “doze” rather than fully power down, waking at preset intervals to check for downlink data. This approach strikes a balance between power savings and the need for timely communication, so your device remains intermittently available and can react to messages with only moderate delay.

When to Choose PSM

On the other hand, PSM is more like sending your device into deep hibernation. This setting is ideal for scenarios where power conservation outweighs the need for rapid network responsiveness, such as water meters, agricultural sensors, or asset trackers that only need to transmit data infrequently and can tolerate being offline for extended periods. With PSM, your device can remain powered down for days at a time, dramatically extending battery life, but it will be unreachable by the network until its next scheduled check-in.

Summary: Responsiveness vs. Power Saving

eDRX:
- Use when your device must occasionally receive commands or updates.
- Good for applications needing reasonable latency for downlink.
- Power savings are significant, though not as deep as PSM.
PSM:
- Use when ultra-long battery life is the top priority.
- Best for devices primarily sending data and rarely receiving it.
- Accept longer periods of being completely offline to the network.

The decision comes down to a trade-off: choose eDRX if your device requires moderate responsiveness and opt for PSM if maximum battery life and infrequent communication suffice. Be sure to test different configurations with your carrier, as real-world performance can vary based on the network environment and application needs.

Practical implementation

To implement eDRX and PSM effectively, consider the following AT commands for managing power-saving settings.

Disabling Power Saving Mode:

AT+CFUN=0

AT+CPSMS=0

AT+CEDRX=0,2

AT+CEDRX=0,4

AT+CEDRX=0,5

AT+CFUN=15

**Checking eDRX Status:**`AT+CEDRXS?`

If the command returns +CEDRXS:OK, then eDRX has been successfully disabled, ensuring no connectivity issues.

Conclusion

eDRX and PSM are essential features for optimizing the power consumption of cellular IoT devices. By carefully implementing these technologies, you can enhance the battery life of your devices, reduce operational costs, and contribute to a more sustainable IoT ecosystem. For further assistance, reach out to your FAE and engage with the community to share experiences and solutions.

By understanding and leveraging eDRX and PSM, you can ensure that your IoT deployments are efficient, reliable, and sustainable, meeting the demands of modern IoT applications.