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BSSPAR1: Chapter 3Idle Mode Operation
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Module Objectives
List the functions of the MS during the idle mode Explain the parameters used for PLMN selection, cell selection and cell
reselection State the purpose of location updates and the associated parameters
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When the MS is switched ON When there is no dedicated connection
When?
To camp on the best suitable cell
Why?
For MS to receive system info from the NW on DL For MS to be able to initiate a call whenever needed For the NW to be able to locate the MS when there is a MT call/SMS
Why to camp on a specific cell?
PLMN selection Cell selection & re-selection Location updates
Idle Mode Tasks
Idle Mode OperationI
MS switched ON
Search RF channels to find BCCH carrier
Check that the PLMN & cell is
allowed
MS camps on the best
suitable cell
See slide 10 for detail
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CM requestsNAS control radiomeasurements
PLMNselected
PLMNavailable
registrationarea changes
locationregistration
response
indicationto user
manual mode
locationregistration
cell selectionand reselection
PLMN selectionand reselection
automatic mode
Camping on a cell: Motivation
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Value
LAI (locationAreaId)
NCC (Network Colour Code) 0 7 BCC (BTS Colour Code) 0 7
BSIC (bsIdentityCode)
CI (cell-ID 0 65535
Parameter
TSC (trainingSequenceCode) 0 7
MCC (Mobile Country Code) 0 999 MNC (Mobile Network Code) 0 99,
0 999 (optional 3-digit MNC) LAC (Location Area Code) 1 65533
CGI (Cell Global Identity) MCC + MNC + LAC + CI
IDs and ID Codes
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Operator controlled PLMN list
User controlled PLMN list
Last registered PLMN or equivalent
PLMN
Home PLMN
Other PLMNs with RATs the MS is
capable of
Switch on in automatic PLMN selection operation mode
Timer Toften called HPLMN Search Timer6 .. 480 minutesDefault: 60 minutes
PLMN Selection
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Campednormally
(adopted from TS 43.022 V5.1.0 chap. 6
Connectedmode
Normalcell selection
Stored listcell selection
Choose cellNormal
cell re-selection
go here whenever anew PLMN is selected
BA list storedfor PLMN
no BA list storedfor PLMN 1
no suitable cell found
suitable cell foundsuitable cell found
trigger
Suitable cellre-selected
no suitablecell found
suitable cell found
leaveidle
mode
returnto idlemode
no suitablecell found
no suitablecell found
IMSI unknown Illegal MS PLMN not allowed
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2
States and State Transition for Cell Selection
(continued on the next page)
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Any cellselection
Camped on
any cell
Choose cell
cell foundno suitablecell found
suitable cell found
leaveidle
mode
returnto idlemode
Connected mode (emergency call
only)
Anycell re-
selection
trigger
cellre-selected
no suitablecell found
go here when no SIM in MS SIM inserted in MS 1
2
cell foundon selected
PLMN
(adopted from TS 43.022 V5.1.0 chap. 6)
States and State Transition for Cell Selection
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Normal Cell SelectionSearch all the RF channels, take samples during
3-5 s and calculate averages. And put them in ascending order with respect to signal level.
Then tune to the strongest RF channel.
Search for the frequency correction burst in that carrier in order to verify if it is a BCCH carrier
Camp on the cell
Try to synchronize to the carrier and read the BCCH data
Is it a BCCH carrier?
Is it a correct PLMN ?
Is the cell barred?
Is C1>0
Tune to the next highest RF channel which is not
tried before
No
No
NoNo
Yes
Yes
Yes
Yes
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I am outside
I am inside, but have not enough
power
C1 = A max(B,0)= RLA_C RXLEV_ACCESS_MIN max(MS_TXPWR_MAX_CCH P , 0)
RLA_C = avg received RxLev on BCCHP = MS max output power
max(B
,0)
0..63 0..31
Pathloss Criterion C1 for Cell Selection and Reselection
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Cell1LAC1
C1 ( Cell1) C1 (Cell2)
A B C
A= 4 dBB= 6 dBC= 8 dB
Cell2LAC2
In case the neighbouring cells belong to different Location Area, a hysteresis is applied with C1 criteria minimizing ping-pong cell reselections cellReselectHysteresis (HYS)(BTS) (014 dB)
Cell Selection with C1
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C1 + CELL_RESELECT_OFFSET TEMPORARY OFFSET * H(PENALTY_TIME - T)for PENALTY_TIME 640 s
C1 - CELL_RESELECT_OFFSET for PENALTY_TIME = 640 sC2 =
serving cell: C2:
List of 6 strongest carriers: C2: C2: C2: C2: C2: C2:
0 .. 126 dBstep size: 2 dB
0, 10, 20, 30, 40, 50, 60, dB
20 .. 640 sstep size: 20 s
PENALTY_TIME
TEMPORARY OFFSET
CELL_RESELECT_OFFSET
C1
C2
T
new candidate= formerly non-
serving cell
CELL_RESELECT_OFFSET
C1
C2
T
new candidate= former serving
cell
no TEMPORARY OFFSET
Pathloss Criterion C2
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cell 1
cell 2
cell 3
C2
time5 seconds
cellreselection
5 seconds
CELL_RESELECT_HYSTERESIS (HYS)
LAC = A LAC = B
cell reselection &location update
Cell Reselection Based on Pathloss Criterion C2
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Cell "A" Cell "B" Cell "C" Cell "D"
cellReselectOffset 0 dB 20 dB 0 dB 0 dB
temporaryOffset 0 dB 30 dB 0 dB 30 dB
penaltyTime 20 s 20 s 20 s 40 s
Micro 900 "D"Macro 1800 "B"
Macro 900 "A"
Macro 900 "C"Road
Parameters
=30 Cell "A" (Serving Cell)=25 Cell "B"=5 Cell "C"=50 Cell "D"
=30 + 0 (H(x)=0, serving cell) Cell "A"=25 + 20 - 30*H(20 - T) Cell "B"=5 + 0 - 0*H(20 - T) Cell "C"=50 + 0 - 30*H(40 - T) Cell "D"
C1
C2 = C1 + cellReselectOffset -temporaryOffset*H(penaltyTime-T)
C2
Time T: (0 - 19 s)C2 =30 Cell "A"C2 =15 Cell "B"C2 =5 Cell "C"C2 =20 Cell "D"
Time T: (20 - 39 s)C2 =30 Cell "A"C2 =45 Cell "B"C2 =5 Cell "C"C2 =20 Cell "D"
Time T: (> 40 s)C2 =30 Cell "A"C2 =45 Cell "B"C2 =5 Cell "C"C2 =50 Cell "D"
Cell Reselection Based on Pathloss Criterion C2
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When shall I select a new cell?
Pathloss Criterion C1C1 0 for a period of 5 s
Pathloss Criterion C2 neighbours C2 value >
current cells C2 value (same LA) neighbours C2 value >
current cells C2 value + HYS(new LA)
for a period of 5 s.Downlink Signalling Failure
DSC 0
RACH FailureMAX RETRANS + 1 times
Authentication Failurenotification by upper layers
Cell has been barredCELL_BAR_ACCESS & CELL_BAR_QUALIFY
Cell Reselection Events
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BTS
BCCH (...,BS_
PA_MFRMS,..
.)
MS
Downlink radio link failure detected!
DSCinit := round BS_PA_MFRMS90
paging message successfully
decoded?
DSC 0
DSC := min (DSC+1, DSCinit) DSC := DSC - 4
yes no
no
yesCell
UpdateDSC = Downlink Signalling failure Counter
2..9 multi-frame periods
DSC := DSCinit
DL Signalling Failure
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Location Update Procedure
BSS MSC VLR HLR
REQUEST SUBSCRIBER INFO
ALL OK - HLR UPDATE
MS
LOCATION UPDATE REQUEST
SEND SUBSCRIBER ID
REQUEST SUBSCRIBER ID
SEND SUBSCRIBER INFO
AUTHENTICATION
AUTHENTICATION RESPONSE
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Paging LocUp
# of cells in Loc. area
signallingtraffic
optimum numberof cells in Loc. area
function of user density,cell size, call arrival rate ...function of
user mobility
Trade-off between Location Update and Paging Traffic
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Location Updates
MS location & status flag => MSC / VLR Mobile Station switched ON mode
IMSI Attach / Detach Same Location Area => No Location Update Different Location Area => Location Update
Change of the Location Area Location Area under the same MSC / VLR Location Area under another MSC / VLR => HLR will be updated
Service is rejected (MS unknown in VLR) Time-Periodic LU (MS -> MSC/VLR)
PER0.5 hDefines the interval between periodic MS location updates. The value 0 means that the periodic location update is not used.
0...25.5 h, step 0.1 h
timerPeriodicUpdateMs
BTS
ATTYesDefines whether IMSI attach/detach is used in the cell.Yes/NoallowIMSIAttachDetach
BTS
BSC -MML Name
Default value
DescriptionRange And Step
Abbreviated Name
MO Class
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60 12 25.512.5
BSS (BTS) parameter (ZEQO)
TIMER PERIODIC UPDATE MS 6 HRS
VLR Parameters (ZMXO)
IMPLICIT IMSI DETACH USEDIMPLICIT DEREGISTRATION 012 HRS. 30 MINLOITERING 00 DAYS 13 HRSVLR CLEANING START TIME 04:12
MS Makes the last contact with network
(MOC, MTC, SMS). If MS makes a IMSI
DETACH, the loitering time starts
MS Has not made a periodic LU till now. DETACH flag set.
No more paging for the MS; Loitering
time starts
MS Data cleaned up from VLR after Loitering time ends. In case the VLR cleaning time occurs
before this time, the MS data is cleaned earlier
MS does not make a periodic
LU. MS still kept Attached
in VLR.
MS does not make a periodic
LU. MS still kept Attached
in VLR.
Time
LU and VLR Cleaning