Question

Within the context of cellular IoT, what is the precise difference between the Power Saving Mode (PSM) and Extended Discontinuous Reception (eDRX) regarding the device&#x27;s ability to be reached by the network?

Accepted Answer

Power Saving Mode (PSM) and Extended Discontinuous Reception (eDRX) are both energy-saving features in cellular IoT, but they differ fundamentally in how they maintain network reachability. In PSM, the device enters a deep sleep state where it stops listening for incoming data entirely, effectively becoming unreachable by the network for the duration of the sleep timer. The device remains registered with the network, meaning it does not need to re-attach when it wakes up, but the network cannot deliver any data to it until the device proactively sends an uplink message to wake itself up. In contrast, eDRX allows a device to sleep for extended periods while still periodically checking for incoming data from the network. During eDRX, the device cycles between long sleep intervals and short, defined windows called paging occasions where it briefly listens for network traffic. Because the device checks for messages at these predictable intervals, the network can reach the device without waiting for the device to wake up on its own. While PSM provides the maximum power savings by disabling all receiver activity, eDRX provides a balance by allowing the network to contact the device with a latency delay determined by the length of the sleep cycle.

Home → All Courses → Engineering and Technology Courses → Internet of Things (IoT) Engineering → Flashcard

Within the context of cellular IoT, what is the precise difference between the Power Saving Mode (PSM) and Extended Discontinuous Reception (eDRX) regarding the device's ability to be reached by the network?