The UE saves energy by turning off regular paging reception. The network cannot deliver a page until the next listening window.
NB-IoT eDRX Reachability Workbench
Explore how extended DRX trades battery life against downlink reachability.
NB-IoT eDRX Reachability Workbench
Stretch the idle paging cycle, choose the Paging Time Window, and drop a downlink command onto the timeline. Watch when the device sleeps, when it can hear the network, and what the battery and latency trade-off becomes.
During the Paging Time Window, the device wakes and checks assigned paging occasions for downlink work.
Longer eDRX means lower average current, but commands may wait minutes or hours before the UE listens again.
For pure uplink sensors, PSM can save more energy. For occasional commands, eDRX gives predictable reachable moments.
Follow one eDRX cycle
The orange marker is a network downlink command. The dark cursor is the device's current position in the cycle.
Device state: extended sleep
The UE is in idle mode and is not checking normal paging occasions. It keeps enough context to wake for the negotiated eDRX paging window.
Power profile
The estimate covers the paging-listen budget only. Uplink reports, attach, retransmissions, and poor coverage can dominate real battery life.
Use the controls like a network designer
Each task changes one decision, so the effect on reachability and energy is easy to see.
Choose the commandable valve preset, then shorten the eDRX cycle until the worst-case waiting time is acceptable.
Select the smart meter preset and make the PTW as short as practical. Notice that most energy is still spent while listening.
Use the diagnosis text: eDRX is periodically reachable; PSM is usually not network-reachable until the device wakes itself.
Scenario
Computed readouts
NB-IoT Quick Reference: eDRX pieces to remember
eDRX cycle
- Total interval between extended idle paging opportunities.
- Longer cycle lowers paging-listen duty cycle.
- NB-IoT can use very long cycles, up to about 2.91 hours in the value set used here.
Paging Time Window
- Short window where the UE listens for paging.
- Common teaching values are 2.56 s steps from 2.56 s to 40.96 s.
- Longer PTW improves scheduling flexibility but costs more energy.
PSM contrast
- eDRX keeps periodic network reachability.
- PSM usually removes paging reachability until the device wakes itself.
- Many designs combine eDRX during active time with PSM for longer quiet periods.
Technical values and assumptions
| Item | Workbench assumption | Why it matters |
|---|---|---|
| eDRX value set | 5.12 s to 10485.76 s, selected by a 4-bit value for this teaching model. | Shows the full latency and energy range without hiding the long-cycle NB-IoT behavior. |
| PTW value set | 2.56 s to 40.96 s in 2.56 s increments. | Lets learners see how a short listening window can still dominate energy because listen current is much larger than sleep current. |
| Current model | 3 uA sleep, 50 mA paging listen, and a small 20 mA wake overhead for visual comparison. | Numbers are realistic-order teaching defaults, not a modem data-sheet guarantee. |
| Latency model | A downlink waits until the next shown paging occasion inside PTW, or until the next cycle if it misses the window. | Real networks also depend on paging identity, radio conditions, repetition, scheduling, and operator configuration. |
Primary references and next study links
- 3GPP TS 24.301: EPS mobility management procedures - eDRX support and NAS parameter negotiation context.
- 3GPP TS 24.008: Mobile radio interface layer 3 specification - timer and information-element value definitions used across cellular systems.
- 3GPP TS 36.304: E-UTRA UE procedures in idle mode - idle-mode cell selection, paging, and DRX context.
- NB-IoT Power Saving Mode animation - compare eDRX reachability with PSM deep sleep.
- NB-IoT Coverage Enhancement workbench - see how repetition and coverage enhancement can change radio-on time.
- NB-IoT Deployment Mode workbench - connect power behavior to deployment and spectrum planning choices.