Devices on a network generally need to listen for network notifications and send tracking information at regular intervals. As a rule, to keep battery drain to a minimum, it’s better to let a device remain in idle (sleep) mode for as long as possible, waking periodically to report to the network and to check if there is any pending data for it.
LTE networks usually provide a power-saving feature called Discontinuous Reception (DRX). This enables devices to frequently stop listening for data and sleep for very short durations at a time (usually 1-2 seconds).
DRX works fine for smartphones. However, many IoT devices don’t need to be as reachable or transmit data a lot less frequently than a phone. Extended DRX (eDRX) is essentially a variation on the DRX principle that allows an IoT device to stay in low-power sleep mode for longer.
With DRX, the network provider decides how long devices go into sleep mode. By contrast, with eDRX, the sleep time length (i.e. the eDRX cycle) can be configured by the device owner or application developer, albeit the networks will have final say on what timers are allowed. Nonetheless, this gives developers a lot of flexibility in striking a balance between ensuring device responsiveness and limiting power consumption to match the needs of specific use cases.
When in an eDRX cycle, a device cannot receive any data sent to it. That data is not delivered until the device wakes up. On waking, the device can listen for pending data without having to establish a full network connection, thereby further helping to preserve power.
