DRX

Paging

9 th July 2016

2015 © Samsung Electronics 1

 Table of contents
 Network Architecture
 DRX
 Paging

2015 © Samsung Electronics 2

 ENB – Interface and Protocol
The Protocols that run between UE and
eNB are called Access Stratum Protocols or
AS Protocols
The Protocols that run between UE and
Core Network are called as NAS Protocols
or Non Access Stratum Protocols

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 MME – Interface and Protocol

2015 © Samsung Electronics 4

 MME – Interface and Protocol

2015 © Samsung Electronics 5

 SAE GW – Interface and Protocol

2015 © Samsung Electronics 6

 SAE GW – Interface and Protocol

• Ip Packet is tunneled between P GW and UE using GPRS Tunneling Protocol GTP

• Each Bearer has associated QCI
• Each QCI has GBR/ Non GBR, Priority, packet delay , Packet Error Rate defined
• PCRF decides the Bearer Type
• P GW performs the DHCP functionality = allocates IP addresses to each UE
2015 © Samsung Electronics 7
 DRX

8
2015 © Samsung Electronics 8
 DRX Parameters (Under Finalization)

- Release :DRX Not in Used

- Setup: Normal DRX Profile is used in normal status and report CGI DRX
Range of values Profile is used in report CGI Status.
- Report CGI: DRX is not used in normal Status and report CGI DRX Profile is
used in report CGI Status.
2015 © Samsung Electronics 9
 UE Based ANR
 Overall Call Flow

#UE reports unknown PCI

#eNB orders UE to report eCGI by sending

“RRCConnectionReconfig”.
Point 1) Samsung eNB does not trigger
report CGI process for those UE with GBR
bearer.  VoLTE UE does not report eCGI

#In order for UE to get eCGI information,

UE has to go to Idle mode with help of
DRX mode or Meausurement GAP (only
applicable for inter FA) to get eCGI
information in SIB1 of the target cell.

#Data Scheduling has higher priority than

DRX mode by 3GPP Standard.
Point2) If UE continuously receives or
transmits
traffic, UE cannot go to DRX mode.
UE-based-ANR is triggered before LSM-based-
ANR

2015 © Samsung Electronics 10

 Discontinuous Reception in Connected State
 In RRC_Connected state, the UE wakes up every DRX Cycle sub frames in a sub frame
defines by DRX start offset. It monitors the PDCCH continuously for a duration known
as active time and then goes back to sleep.

The UE stays awake for

‘on duration’ waiting
for a scheduling
message on the
PDCCH. If one arrives
then the UE remains
awake for a time of
DRX ‘inactivity timer’
after every such
PDCCH command.

Inactivity timer gets restarted

upon receiving PDCCH
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 DRX Definitions
 DRX Cycle: Specifies the periodic repetition of the On Duration followed by a possible
period of inactivity (see figure below).

Figure 1 : DRX Cycle

 drx-InactivityTimer: Specifies the number of consecutive PDCCH-subframe(s) after
successfully decoding a PDCCH indicating an initial UL or DL user data transmission for
this UE.
 drx-RetransmissionTimer: Specifies the maximum number of consecutive PDCCH-
subframe(s) for as soon as a DL retransmission is expected by the UE.
 drxShortCycleTimer: Specifies the number of consecutive subframe(s) the UE shall
follow the Short DRX cycle.
 drxStartOffset: Specifies the subframe where the DRX Cycle starts.
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 DRX Definitions
 onDurationTimer: Specifies the number of consecutive PDCCH-subframe(s) at the
beginning of a DRX Cycle.
 The UE may be configured by RRC with a DRX functionality that controls the UE’s
PDCCH monitoring activity for the UE’s C-RNTI, TPC-PUCCH-RNTI, TPC-PUSCH-RNTI
and Semi-Persistent Scheduling C-RNTI (if configured).
 When in RRC_CONNECTED, if DRX is configured, the UE is allowed to monitor the
PDCCH discontinuously using the DRX operation specified; otherwise the UE monitors
the PDCCH continuously.
 When using DRX operation, the UE shall also monitor PDCCH according to
requirements found in other sub clauses of this specification. RRC controls DRX
operation by configuring the timers onDurationTimer, drx-InactivityTimer, drx-
RetransmissionTimer (one per DL HARQ process except for the broadcast process),
the longDRX-Cycle, the value of the drxStartOffset and optionally the
drxShortCycleTimer and shortDRX-Cycle. A HARQ RTT timer per DL HARQ process
(except for the broadcast process) is also defined

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 DRX Discontinuous Reception
 In RRC_CONNECTED state, the E-UTRAN allocates radio resources to the UE.
 The UE monitors the PDCCH channel for the same. The UE provides the eNode B with the buffer
status, down link channel quality and neighboring cell measurement.
 To extend the battery life, the UE in RRC_CONNECTED state may be configured with DRX
Discontinuous Reception.
 RRC connection control covers all procedures related to establishment, modification and release of
an RRC connection including paging, initial security activation, establishment of SRB Signaling Radio
Bearers and of radio bearers carrying user data (Data Radio Bearers DRBs), handover within LTE,
access class barring and radio link failure.
 A DRX cycle consists of an ‘On Duration’ during which the UE should monitor the PDCCH and a ‘DRX
Period’ during which a UE can skip reception of PDCCH
 The parameters used for DRX involve a trade off between battery savings and latency
 Two DRX cycles - a short cycle and a long cycle can be defined for each UE. The transition between
short DRX, long DRX cycle and continuous reception is controlled either by timer or by explicit
commands
 If no data arrives at the eNodeB during the short DRX cycle the UE enters the long DRX cycle.

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 DRX
 For highly predictable traffic e.g. VoIP the on duration can be set to 1 sub frame and
DRX cycle to 20 ms or 40 ms (if packet staggering is used)
 HARQ retransmissions are planned outside of the predefined DRX Inactivity Timer
 DRX Inactivity Timer – the UE keeps awake
 DRX Retransmission Timer - UE does not have to wait for full DRX cycle for an
expected retransmission that has been lost due to either ACK/NACK misinterpretation
or PDCCH failed detection.
 Signaling of SRS and CQI is tied to the DRX parameters to reduce the use of PUCCH
resources in long DRX periods
 For very long DRX periods and a long time between SRS transmissions , the network
and UE may lose time alignment and so the UE has to restart transmission to the
network using RACH.
 The short DRX cycle can be triggered that allows for periodic activity within the
regular DRX cycle if additional and time distributed scheduling resources are needed
to facilitate the best power savings and QoS tradeoff for the given UE
 When the short DRX inactivity timer expires the UE returns to the normal DRX
pattern immediately.

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 DRX Parameters
After expiry of DRX
Inactivity Timer (specified
in psf) the UE should go
into DRX Mode

Short DRX is the first type

of DRX (if defined) that
needs to be followed when
UE goes in DRX Mode
Cycle
On duration timer specifies
the number of ‘psf’ at the
beginning of each DRX and
is applied to both long and
short DRX cycles
Short DRX Timer indicates
the number of short DRX
to be followed before
entering Long DRX

If short DRX cycle is configured

the duration of long DRX cycle
shall be multiple of short DRX
to ensure no overlap between
OFF
2015 and ON
© Samsung duration
Electronics 16
 Example of DRX Settings
Apart from DRX timers, the eNode B MAC can transmit DRX command MAC CE when it
does not have any more data to transmit to the UE – the UE then enters short DRX cycle
if configured else in long DRX cycle – this shortens the UE On period

The On Duration
Timer is a part of
a DRX Cycle

‘psf’ is a PDCCH sub frame – in FDD every frame can be a PDCCH sub frame while in TDD only
downlink frames are PDCCH sub frames including DwPTS
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 DRX Operation
 When there is no data activity for ‘DRX Inactivity Timer’ amount of time (i.e. expiry of
DRX Inactivity Timer) or ‘DRX Command MAC CE’ is received –
 If short DRX cycle is configured the UE should start ‘DRX Short Cycle Timer’ and start using
short DRX cycle. Else if short DRX is not configured the UE should use the Long DRX Cycle

 If ‘DRX Short Cycle Timer’ expires i.e. maximum number of short cycles are already used,
then the UE should enter the Long DRX Cycle.

 If a DRX Command MAC Control Element is received, the UE should stop ‘On Duration
Timer’ and ‘DRX Inactivity Timer’

 During the active time, the UE shall monitor the PDCCH, if the PDCCH indicates a new
transmission (DL or UL) in sub frame #n, then the UE should start/restart DRX
Inactivity Timer in sub frame n+1.

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 DRX Operation
 The UE should start the ‘On Duration Timer’ in a sub frame which satisfied the following
equation depending on whether Short DRX is configured or not
 - If the Short DRX Cycle is used and [(SFN * 10) + subframe number] modulo (shortDRX-Cycle) =
(drxStartOffset) modulo (shortDRX-Cycle); or
 - if the Long DRX Cycle is used and [(SFN * 10) + subframe number] modulo (longDRX-Cycle) =
drxStartOffset:
 When down link assignment has been configured and if the configured assignment recurs
in sub frame that does not fall in Active Time, the UE need no decode PDSCH, it is the
eNode B’s responsibility to make sure that the configured assignment falls in the ‘On
Duration Timer’
 On monitoring the PDCCH; if the PDCCH indicates a DL transmission or if a DL assignment
has been configured for this sub frame:
 - start the HARQ RTT Timer for the corresponding HARQ process;
 - stop the drx-RetransmissionTimer for the corresponding HARQ process.
 - if the PDCCH indicates a new transmission (DL or UL):
 - start or restart drx-InactivityTimer.

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 HARQ RTT
 In addition to the DRX behavior, a HARQ RTT Timer is defined with the aim of allowing the
UE to sleep during the HARQ RTT.

 When decoding a down link Transport Block fails, the UE can assume that the next
retransmission of the TB will occur at least after ‘HARQ RTT’ sub frames

 With HARQ RTT timer is running the UE does not need to monitor the PDCCH

 At the expiry of the HARQ RTT timer, if the received data for a downlink HARQ process is
not correctly decoded, the U stats a DRX Retransmission Timer for that HARQ process

 This timer is fixed and not configured by RRC. For FDD the HARQ RTT Timer is set to 8 sub
frames. For TDD the HARQ RTT Timer is set to k+4 sub frames where k is the interval
between the down link transmission and the transmission of associated HARQ feedback.

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 DRX Steps
 When a DRX cycle is configured, the Active Time includes the time while:
 - onDurationTimer or drx-InactivityTimer or drx-RetransmissionTimer or mac-
ContentionResolutionTimer is running; or
 - a Scheduling Request is sent on PUCCH and is pending ; or
 - an uplink grant for a pending HARQ retransmission can occur and there is data
in the corresponding HARQ buffer; or
 - a PDCCH indicating a new transmission addressed to the C-RNTI of the UE has
not been received after successful reception of a Random Access Response for
the preamble not selected by the UE.

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 DRX Steps
 When DRX is configured, the UE shall for each subframe:
 - if a HARQ RTT Timer expires in this subframe and the data of the corresponding
HARQ process was not successfully decoded:
 - start the drx-RetransmissionTimer for the corresponding HARQ process.
 - if a DRX Command MAC control element is received:
 - stop onDurationTimer;
 - stop drx-InactivityTimer.

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 DRX Steps
 if drx-InactivityTimer expires or a DRX Command MAC control element is received in
this subframe:
 if the Short DRX cycle is configured:
—start or restart drxShortCycleTimer;
—use the Short DRX Cycle.
 else:
 use the Long DRX cycle.
 if drxShortCycleTimer expires in this subframe:
 use the Long DRX cycle.
 If the Short DRX Cycle is used and [(SFN * 10) + subframe number] modulo (shortDRX-
Cycle) = (drxStartOffset) modulo (shortDRX-Cycle); or
 if the Long DRX Cycle is used and [(SFN * 10) + subframe number] modulo (longDRX-
Cycle) = drxStartOffset:
 start onDurationTimer.

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 DRX Steps

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 Paging
 PDSCH is used for paging
 Similar to broadcast data, paging indicators on the PDCCH use a single fixed identifies called the Paging
RNTI P-RNTI – UE looks for any information encrypted by P-RNTI. If PDCCH indicates a paging message
is transmitted in the sub frame, the UE needs to demodulate the PCH to see if the paging message is
directed to it.
 Different UEs monitor different paging sub frames for their paging messages
 Paging messages may be received in sub frame 0,4,5,or 9 in each radio frame for FDD and in sub frame
0,1,5 and 6 for FDD
 Public Warnings – the ETWS Earthquake and Tsunami Warning System uses paging message to both
Idle State and Connected State UEs 128 frames set

The UE wakes up once every DRX

cycle frame to listen to the paging
frame
Within that frame the UE inspects
a sub frame known as paging
occasion which also depends on
IMSI
When DRX is used the UE needs
only to monitor one PO per DRX
cycle.
The paging message contains S-
TMSI if available or IMSI otherwise

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 DRX in Idle Mode - Paging
 UE may use DRX in idle mode defined in SIB2 (monitor PDCCH discontinuously for P-RNTI)
 UE should be able to calculate when to wake up and to check the correct sub frame. For
this the UE stores the default paging cycle and the number of paging groups when it
receives the necessary information from SIB2
 To receive the paging message from E-UTRAN, UEs in idle mode monitor the PDCCH
channel for P-RNTI value used to indicate paging
 For receiving paging, the UE calculates the radio frame (the Paging Frame (PF)) and the
sub frame within the PF (the Paging Occasion (PO)) as follows
Parameter nB is used to get number of paging
occasion per cycle
Larger value of nB larger is paging capacity

Feature / Parameter Reference

configuration Value
defaultPagingCycle 1280 ms
Paging
nB 1T

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 Paging Parameter - defaultPagingCycle
This Parameter required the value to calculate the paging frame and paging
occasion. When DRX is used, UE monitors a single occasion per DRX. If UE
Description
specific DRX is not set by the upper layer, defaultpaging cycle is applied as the
default DRX Cycle.
Unit rf(Radio Frame)

Diagram

Indicates the number of radio frames in the paging cycle. Larger the value of
Identifying this parameter, lesser the UE battery power consumption. Whereas smaller
Appropriate Value the value of DRX cycle, increase in the UE battery power consumption. But
there is possibility with to set higher value to miss important Alert.
Range of values rf32,rf64,rf128,rf256
Recommended value rf128

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 Paging Parameter - nB
This Parameter required the value to calculate the paging frame and paging occasion. LTE UE in RRC IDLE mode use DRX to
reduce the power consumption. DRX cycle will determine how frequently UE will check for paging messages. DRX cycle is
broadcast within SIB2. It can have values of 32, 64, 128 or 256 radio frames. These corresponds to time intervals of 320, 640,
1280 and 2560ms.
The UE can also propose its own DRX cycle length within ATTACH REQUEST and TRACKING AREA UPDATE REQUEST messages.
The set of allowed values are same as used in SIB2.
Paging frame occurs when following equation satisfies:
Description SFN mod T = (T/N) x (UE_ID mod N)
Where, T = DRX cycle length in radio frames
N = Min(T,nB)
nB is broadcast within SIB2 and can have values of {4T,2T,T,T/2,T/4,T/8,T/16,T/32} N can have values of
{T,T/2,T/4,T/8,T/16,T/32}
UE_ID = IMSI mod 1024
UE do not need to check for all 1ms sub frames within its paging frames. A UE only needs to check the sub frame identified by
its paging occasion.
Unit T = DRX Cycle Length
When nB is set to a value smaller than T, it affects the System Frame Number of the PF, position of PO in the PF, and also
Identifying
distribution of User Equipments into “groups” with the same PF. When is set to a smaller value, the “groups” will be fewer but
Appropriate Value
larger and vice versa.
Range of values 4T, 2T, T, 1/2T, 1/4T, 1/8T, 1/16T, 1/32T
Parameter nB is used to calculate the number and position of Paging Occasions (PO) and Paging Frames (PF).
The numerical value of nB is dependent on the value of the defaultPagingCycle (T). When nB is set to T, 2T or 4T, it determines
Remarks the number of POs per PF, and the PO position in PF. When nB is set to a value smaller than T, it affects the System Frame
Number of the PF, position of PO in the PF, and also distribution of User Equipment into “groups” with the same PF. When is set
to a smaller value, the “groups” will be fewer but larger and vice versa.
Recommended value T

Maximum value of N[=min(T,nB)] =1 i.e. maximum one radio frame per DRX cyrcle can be used for paging
Maximum value of Ns= max(1,nB/T) would be 4 – which means maximum four sub frames per radio
frame
2015 used
© Samsung for paging can be allocated for paging and minimum is one sub frame
Electronics 28
 Paging Example
T = min (Tc,Tue)
PF occurs when
SFN mod T = (T/N) x N = min (T,nB)
(UE_ID mod N)
Ns = max(1,nB/T)

i_s= [UE_ID/N]mod Ns

 In case A and B, N=64 and 32 respectively – thus one out of every four radio frames (N : T)
is used for paging, using one sub frame in each those radio frames (Ns)
 For case B, there are 32 paging frames within the UEs paging cycle across which the UEs
are distributed based on the UE identity
 In case C two sub frames in each radio frame are used for paging i.e. Ns=2. In this case
there are 128 paging frames (=N) within UEs paging cycle and the UEs are distributed
across the two sub frames within the paging frame
 The LTE specifications include a Table that indicates sub frames applicable for each
combination of Ns and i_s
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 Sub frames applicable as per i_s and Ns
FDD

TDD

Current Network Settings :

Default Paging Cycle : T= 128rf = 1280 ms, nB=T= 128rf
Thus N = Number of frames for paging in Paging Cycle = min(T,nB)= 128 which means every
radio frame used for paging.
Ns= max(1,nB/T) = 1 this means one sub frame per radio frame for paging
Thus the UE wakes up every 1.28 s and monitors one sub frame depending on its IMSI for
the paging messages
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 RRC Timers

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 RRC Timers
Timer Start Stop At expiry
Reception of RRCConnectionSetup or
Transmission of RRCConnectionReject message, cell re- Perform the actions as specified in
T300
RRCConnectionRequest selection and upon abortion of connection 5.3.3.6
establishment by upper layers
Reception of
Transmission of RRCConnectionReestablishment or
T301 RRCConnectionReestabilshme RRCConnectionReestablishmentReject Go to RRC_IDLE
ntRequest message as well as when the selected
cell becomes unsuitable
Reception of
RRCConnectionReject while Upon entering RRC_CONNECTED and Inform upper layers about barring
T302
performing RRC connection upon cell re-selection alleviation as specified in 5.3.3.7
establishment
Access barred while
performing RRC connection Upon entering RRC_CONNECTED and Inform upper layers about barring
T303
establishment for mobile upon cell re-selection alleviation as specified in 5.3.3.7
originating calls
Reception of
In case of cell change order from E-
RRCConnectionReconfiguratio
UTRA or intra E-UTRA handover,
n message including the Criterion for successful completion of
initiate the RRC connection re-
MobilityControl Info or handover to EUTRA or cell change order
T304 establishment procedure; In case of
reception of is met (the criterion is specified in the
handover to E-UTRA, perform the
MobilityFromEUTRACommand target RAT in case of inter-RAT)
actions defined in the specifications
message including
applicable for the source RAT.
CellChangeOrder
Access barred while
performing RRC connection Upon entering RRC_CONNECTED and Inform upper layers about barring
T305
establishment for mobile upon cell re-selection alleviation as specified in 5.3.3.7
originating signalling

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 RRC Timers
Timer Start Stop At expiry
Access barred while performing
Inform upper layers about
RRC connection establishment Upon entering RRC_CONNECTED and upon cell
T306 barring alleviation as specified in
for mobile originating CS re-selection
5.3.3.7
fallback.
Upon detecting physical layer Upon receiving N311 consecutive in-sync If security is not activated: go to
problems i.e. upon receiving indications from lower layers, upon triggering the RRC_IDLE else: initiate the
T310
N310 consecutive out-of-sync handover procedure and upon initiating the connection re-establishment
indications from lower layers connection re-establishment procedure procedure
Upon initiating the RRC
Selection of a suitable E-UTRA cell or a cell using
T311 connection re-establishment Enter RRC_IDLE
another RAT.
procedure
Upon receiving t320 or upon cell
(re)selection to E-UTRA from
Upon entering RRC_CONNECTED, when PLMN
another RAT with validity time Discard the cell reselection
selection is performed on request by NAS, or upon
T320 configured for dedicated priority information provided by
cell (re)selection to another RAT (in which case the
priorities (in which case the dedicated signalling.
timer is carried on to the other RAT).
remaining validity time is
applied).
Initiate the measurement
Upon acquiring the information needed to set all
Upon receiving measConfig reporting procedure, stop
fields of cellGlobalId for the requested cell, upon
T321 including a reportConfig with the performing the related
receiving measConfig that includes removal of the
purpose set to reportCGI measurements and remove the
reportConfig with the purpose set to reportCGI
corresponding measId
Upon receiving Upon log volume exceeding the suitable UE
Perform the actions specified in
T330 LoggedMeasurementConfigurati memory, upon initiating the release of
5.6.6.4
on message LoggedMeasurementConfiguration procedure

Constant Usage
N310 Maximum number of consecutive "out-of-sync" indications received from lower layers

N311 Maximum number of consecutive "in-sync" indications received from lower layers
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 Copyright and Confidentiality
Copyright © 2015, SAMSUNG Electronics Co., Ltd. SAMSUNG Electronics reserves the right to make changes to the specifications of
the products detailed in this document at any time without notice and obligation to notify any person of such changes. Information
in this document is proprietary to SAMSUNG Electronics Co., Ltd. No information contained here may be copied, translated,
transcribed or duplicated by any form without the prior written consent of SAMSUNG Electronics.
2015 © Samsung Electronics 34
 Other Actions Taken to Avoid Call Drop

 All eNBs upgraded to PKG 5.0.0
 Multi-Band Implementation
 Forward Hand Over enabled


 Equal SAEGW Traffic distribution
 TA/TAL/BTAL Configuration Audited
 GBR Bearer preservation set to “ON” (i.e. In Test Area Serving 7 MMEs Only )
S1AP - Cause
Cause Description Old Value New Value Benefit
Code Value
Handover Failure In Target EPC/eNB Or Target
06 OFF ON
System
Failure in the Radio Interface Reduction in Call Drops due to
26 OFF ON RLF for fractions of seconds
Procedure
21 UE Connection Lost OFF ON

 Function Flag #9 (NOT_USE_PRSV_GBR_FOR_ACT_S1) to “ON”

 To the preserve status of S1AP CAUSE (tx2 relocation timer expiry)


 Clear Test Area Service Impacting Alarms
 Check Test Area Availability Status
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