Cellular

In addition to the broad use cases mentioned above, there are a number of considerations to take into account to make an energy efficient choice for cellular connectivity.  For devices that communicate using LTE modems, select network operators that support eDRX (Extended Discontinuous Reception) and PSM (Power Save Mode).  These are two complementary features that can be used together to optimize power consumption in LTE devices.

In PSM, LTE devices enter a low-power sleep mode for extended periods of time, waking up at pre-defined intervals to reconnect to the network without a full negotiation, greatly reducing power consumption. With PSM, while the device is asleep the radio can be considered to be completely off, in contrast to eDRX, which continues a paging cycle. This means that if a page or network-initiated downlink request were to be made, the device in PSM mode would not receive anything. This can result in an increased disconnected window compared to eDRX.

eDRX allows the device to more precisely define the interval between listening periods, which can reduce power consumption while still maintaining connectivity. This is useful for devices that need to remain connected to the network for longer periods of time, such as mobile devices. This increased paging window means that latency between a request to the device is increased but the device is nonetheless available.

 PSM is more power efficient than eDRX.  However, there is an inflection point at which it may make more sense for a device to use one versus the other. While building an application you should test your particular hardware for overall power consumption during a typical window of sleep and active states. Use both PSM and eDRX at the predefined eDRX paging windows and then choose the methodology that best optimizes your device's power usage during its typical usage.  eDRX is also a more recent technology and might not be supported by all network providers.