Internet of Things
(IoT) is a computing concept where everyday objects have internet connectivity
and they can collect and exchange data. IoT is a network which can comprise of
a wide variety of physical devices, vehicles, buildings, and any other
device/object used in our daily lives. They are embedded with sensors, software
and network connectivity which help them communicate with other devices in the
network and can be controlled remotely thus increasing efficiency, accuracy and
economic benefit. Any device/object which has to be a part of the IoT network
This feature is license controlled. Please consult your Cisco
Account Representative for information about the specific license.
Power Saving Mode
(PSM) was introduced in 3GPP Release 12, to improve device battery life of IoT
devices. The most significant benefit of this feature is the UE has more
control in terms of power management required for its application. There are a
wide range of IoT applications where flexibility of the UE to manage its power
is very important and also implementation of PSM can prevent network
congestion. The timers of all the devices can be managed using PSM, and the
wake-up periods can be adjusted to be offset as much as possible. This way all
of the devices will not wake at the same time and attempt to access the
network. The PSM mode is similar to power-off but the UE remains registered on
The UE activates
PSM by including two timer values in the Attach or Tracking Area Update (TAU).
The first timer is the T3324, which defines the time the UE stays active after
idle mode following the Attach or TAU procedure. The second timer is an
extended T3412 which defines the extended time for an UE to send periodic TAU.
T3324 Active Timer
The UE requests for
a T3324 Active Timer value during Attach and TAU procedures. The MME allocates
the T3324 value to the UE. The T3324 active timer determines the duration
during which the device remains reachable for mobile terminated transaction on
transition from connected to idle mode. The device starts the active timer when
it moves from connected to idle mode and when the active timer expires, the
device moves to Power Saving Mode. The MME takes the UE requested value and MME
local configuration into account for determining the Active Timer value. The
MME includes the T3324 value IE in the ATTACH ACCEPT/TAU ACCEPT message only if
the T3324 value IE was included in the ATTACH REQUEST/TAU REQUEST message. A UE
using PSM is available for mobile terminating services only for the period of
an Active Time after a mobile originated event like data transfer or signaling
for example after a periodic TAU/RAU procedure.
The MME allows a
value of '0' for the T3324 timer. In this case the UE enters the Power Saving
The Mobile reachability timer is set equal to the T3324 timer (Active
Time). The MME allows a value of '0' for the T3324 timer. In this case the UE
enters the Power Saving Mode immediately.
If a session recovery occurs then the
active timer re-starts only for the remaining time of the total time configured
before session recovery. Once the remaining time of the active timer elapses
the UE moves to the power saving mode.
T3412 Extended Timer
The T3412 timer is
also referred to as the periodic Tracking Area Update (TAU) timer. Periodic
tracking area updating is used to periodically notify the availability of the
UE to the network. The procedure is controlled in the UE by the periodic
tracking area update timer (timer T3412). The value of timer T3412 is sent by
the network to the UE in the ATTACH ACCEPT message and can be sent in the
TRACKING AREA UPDATE ACCEPT message. The UE shall apply this value in all
tracking areas of the list of tracking areas assigned to the UE, until a new
value is received. A longer periodic TAU timer is possible using T3412 extended
timer. When the UE includes the T3324 value IE and the UE indicates support for
extended periodic timer value in the MS network feature support IE, it may also
include the T3412 extended value IE. Apart from the value requested by the UE,
the MME verifies the local configuration into account while selecting a value
for the T3412 extended timer. When the MME includes the T3412 extended value IE
in the ATTACH ACCEPT message or TRACKING AREA UPDATE ACCEPT message , the MME
uses timer T3412 extended value IE as the value of timer T3412. The Implicit
Detach Timer (IDT) is set to 4 minutes greater than the T3412 extended timer.
The MME allows a
value of "0" for timer T3324 (Which implies the UE enters Power Saving Mode
MME may also
include Downlink buffer duration and "Downlink suggested packet count" in DDN
ACK if it is configured.
The following new
flags are introduced as part of this feature; these flags are supported in
GTPCv2 Indication IE:
Initiated PDN Connection Signaling Indication (PNSI): The source MME supports
sending of PNSI flag in GTPCv2 Indication IE of Context response.
UE Available for
Signaling Indication (UASI): The MME supports sending of the UASI flag in
GTPCv2 Indication IE of Create Session Request and Modify Bearer Request to
indicate to the PGW that the UE is available for end to end signaling.
Connection Indication (DTCI): The MME supports receiving the DTCI flag in
Create Session Response from the SGW. The MME supports receiving of the DTCI
flag in Context Response and Forward Relocation Request from peer MME or
The MME rejects
CBR/UBR when PPF is False. The cause "UE is temporarily not reachable due to
power saving" is sent in the response by the MME if the corresponding PDN was
marked "Delay tolerant" by PGW.