How Should I Configure LTE-M and NB-IoT Values for my Smart Metering Project?

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How should I configure certain LTE-M and NB-IoT values for my smart metering project where consumption should be read every few hours?

 
Nicolas Damour, Director, Technology Partnership Development, Sierra Wireless

What is the value of the “T3412 value” IE sent by the terminal?Mobile IoT devices (terminals) can be configured to use a so-called “Power Saving Mode” to save as much energy as possible when they have an active data bearer and IP address and want to keep it in between uplink transmissions. This is done by entering a deep hibernation state after notifying the network and saving local state onto local memory. This makes sense especially for Mobile IoT applications where uplink transmissions are expected to happen not too often in general (typically no more than once per hour), and also if it is not a requirement that the Mobile IoT device should be reachable quickly at any given time. If these two conditions are met, then the Mobile IoT device can be configured to use Power Saving Mode, in which case it will notify the network of its typical sleep period, noted T3412, which can be hours, days or even weeks or months (theoretical maximum: 413 days). While asleep, the device cannot be contacted (“paged”) by the network, but it is expected to wake up at the latest at the end of every such defined sleep period (the device can also “decide” to wake up earlier) to quickly check in and let the network send any downlink data/command that may have been stored for the device.
Conclusion: the value of T3412 depends on the application, and should be set to whichever typical interval the device is expected to send data to the network.

For PSM, what is the value of the “T3324 value” IE sent by the terminal?
When configured for using “Power Saving Mode” (see above), a Mobile IoT device shall not only inform the network of its sleep period T3412, but also of an “active period” where it will continue to listen to the network so as to allow incoming messages to be sent by the network to the device. This ‘active period” is noted T3324 and can be set to a maximum of 12 days, even though it will be typically set to much smaller values (like 1 minute or even 30 seconds). The longer the active period, the more energy the device will spend listening to the network every time it wakes up, but the easier it will be for cloud-side applications to contact the device in between sleep cycles.
Conclusion: the value of T3324 depends on the application, and should be set to whichever typical interval the device is expected to wait for incoming data in between sleep cycles. A good value can be 1 or 2 minutes to start with.

What is the “Narrowband S1 Mode Paging Period” value requested by the UE?
Mobile IoT devices (terminals) can be configured to use a so-called “Extended DRX” feature, or “Extended Paging”, to save as much energy as possible when they have no active data bearer and IP address. This is achieved by listening to potential incoming messages and data (so-called “pages”) from the network less often than the otherwise standard value of every 1.28 seconds. This makes sense especially for Mobile IoT applications where it is not a requirement that the Mobile IoT device should be reachable too quickly at any given time. In such a case, the Mobile IoT device can then be configured to use Extended DRX: it will first inform the network of its new desired “Paging Period”, which can be minutes or even hours (theoretical maximum: about 44 minutes in LTE-M and about 3 hours in NB-IoT). If the network accepts the request, then the device will just listen to incoming “pages” at the end of the new Paging Period, for a very, very short time, and save a lot of power.
Conclusion: the value of NarrowBand S1 Mode Paging Period depends on the application, and should be set to whichever typical interval where the device should be reachable from the network. In other words, if the application accepts a maximum latency of xxx seconds, then this should be the value of the Paging Period.

What is the “Narrowband S1 Mode PTW Length” value requested by the UE?
When using Extended DRX (see above), the device listens less often to the network. However, due to possible desynchronization of the internal clocks between the device and the network, it may happen that the devices listens at a slightly different time than when the network tries to send a “ping”.
In order to avoid this, the device may inform the network that it will listen not only once at the end of each Paging Period, but one, two, three or more times, making a number of listening attempts over a period of time called the Paging Time Window, that can be explicitly requested by the device (theoretical max value: 20.48 seconds in LTE-M and 30,762 seconds in NB-IoT).
Recommended value: 5.12 seconds or 10.24 seconds.

What is the “Wideband S1 Mode Paging Period” value requested by the UE?
See above Narrowband S1 Mode Paging Period, which is applicable for NB-IoT. This parameter is the same, but when used in LTE-M.

What is the “Wideband S1 Mode PTW Length” value requested by the UE?
See above Narrowband S1 Mode PTW Length, which is applicable for NB-IoT. This parameter is the same, but when used in LTE-M.