SARA-R4/N4 series - System Integration Manual
UBX-16029218 - R11 System description Page 48 of 157
For the definition and the description of the SARA-R4/N4 series operating modes, including the events
forcing transitions between the different operating modes, see section 1.4.
The SARA-R4/N4 series modules achieve the low power deep sleep mode by powering down all the
Hardware components with the exception of the 32 kHz reference internally generated.
☞ From the host application point of view, the serial port will not be available during low power deep
sleep mode, as the SARA-R4/N4 series module will act as if it is in Power-Off mode.
1.13.9.3 Timers and network interaction
The SARA-R4/N4 series modules goes in low power deep sleep mode entering in the Power Saving Mode
(PSM) defined in 3GPP Release 13.
Two timers have been specified on the PSM Signaling: the “Periodic Update Timer” and “Active Timer”.
The “Active Timer” is the time defined by the network where the SARA-R4/N4 series module will keep
listening for any active operation, during this time the module is in Active mode.
The “Periodic Update Timer” is the Extended Tracking Area Update (TAU) used by the SARA-R4/N4 series
module to periodically notify the network of its availability.
The SARA-R4/N4 series module requests the PSM by including the “Active Timer” with the desired value in
the Attach, TAU or Routing Area Update (RAU) messages. The “Active Timer” is the time the module listens
to the Paging Channel after having transitioned from connected to active mode. When the “Active Timer”
expires, the module enters PSM low power deep sleep mode.
SARA-R4/N4 series module can also request an extended “Periodic Update Timer” value to remain in PSM
low power deep sleep mode for longer than the original “Periodic Update Timer” broadcasted by the
network.
The grant of PSM is a negotiation between SARA-R4/N4 series module and the attached network: the
network accepts PSM by providing the actual value of the “Active Timer” (and “Periodic Update Timer”) to
be used in the Attach/TAU/RAU accept procedure. The maximum duration, including the “Periodic Update
Timer”, is about 413 days. The SARA-R4/N4 series module enters PSM low power deep sleep mode only
after the “Active Timer” expires.
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