Power Saving Mode (PSM) is a feature introduced in cellular technologies, particularly for the Internet of Things (IoT) devices using LTE-M and NB-IoT (Narrowband IoT) networks. The primary purpose of PSM is to extend the battery life of IoT devices, many of which need to operate for several years without a battery change. Here’s a breakdown of how PSM works:
Purpose: PSM is designed for devices that only occasionally transmit data. By allowing these devices to enter a deep sleep mode, PSM can significantly extend their battery life.
Functionality:
- When a device is in PSM, it doesn’t need to maintain a regular network connection or perform routine updates. This conserves power.
- Even in PSM, the device remains registered with the network, so there’s no need to re-establish a full network connection (which can be power-intensive) when the device wakes up to transmit data.
PSM Timers:
- Active Time (T3324): After transmitting data, the device will stay active for a specified duration to wait for potential incoming data or commands. Once this time expires, the device goes into a deep sleep mode.
- Sleep Time (T3412): This is the duration for which the device will remain in deep sleep. During this time, the device will not be reachable for communication. After this time expires, the device will “wake up” and check for network signals or pending communication.
Applications: PSM is ideal for devices that only need to transmit data at long intervals, such as:
- Environmental sensors that report data a few times a day.
- Utility meters that might send usage data once every few hours or daily.
- Agricultural sensors that monitor soil conditions and report periodically.
- Asset trackers that provide location updates at set intervals.
Advantages:
- Extended Battery Life: Devices can operate for several years on a single battery charge.
- Reduced Network Overhead: By allowing devices to remain in a deep sleep for extended periods, there’s less routine communication with the network, conserving resources.
Considerations: While PSM is great for conserving power, it does mean that devices are not continuously reachable. This is suitable for many IoT applications but might not be ideal for scenarios where real-time communication is essential.
In summary, Power Saving Mode is a crucial feature for the burgeoning IoT landscape, allowing for efficient, long-lived deployments without the need for frequent human intervention (like battery changes).