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1 © Nokia Siemens Networks
BSSPAR1: Chapter 3 Idle Mode Operation
2 © Nokia Siemens Networks
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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 Operation I
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 requests NAS control radio
measurements
PLMN
selected
PLMN
available
registration
area changes
location
registration
response
indication
to user manual mode
location
registration cell selection
and reselection
PLMN selection
and 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
ID’s and ID Codes
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Operator controlled PLMN list
User controlled PLMN list
Last registered PLMN or equivalent
PLMN
Home PLMN
Other PLMN‘s with RAT‘s the MS is
capable of
Switch on in automatic PLMN selection operation mode
Timer T
often called “HPLMN Search Timer“ 6 .. 480 minutes
Default: 60 minutes
PLMN Selection
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Camped
normally
(adopted from TS 43.022 V5.1.0 chap. 6)
Connected
mode
Normal
cell selection
Stored list
cell selection
Choose cell
Normal
cell re-selection
go here whenever a
new PLMN is selected
BA list stored
for PLMN no BA list stored
for PLMN 1
no suitable cell found
suitable cell found suitable cell found
trigger
Suitable cell
re-selected
no suitable
cell found
suitable cell found
leave
idle
mode
return
to idle
mode
no
suitable
cell
found
no suitable
cell found • IMSI unknown
• Illegal MS
• PLMN not allowed
2
2
States and State Transition for Cell Selection
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Any cell
selection
Camped
on
any cell
Choose cell
cell found no suitable
cell found
suitable cell found
leave
idle
mode
return
to idle
mode
Connected mode
(emergency call
only)
Any
cell re-
selection
trigger
cell
re-selected
no suitable
cell found
go here when no SIM in MS SIM inserted in MS 1
2
cell found
on selected
PLMN
(adopted from TS 43.022 V5.1.0 chap.
States and State Transition for Cell Selection
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Normal Cell Selection Search 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
No No
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 BCCH
P = MS max output power
Pathloss Criterion C1 for Cell Selection and Reselection (m)
TXP1 (800/900) 5….39dBm
TXP2 (1800 0….36dBm
TXP2 (1900) 0….32dBm & 33 dBm
Step 2 dBm
Default(900): 33dBm
(RXP) -110…..-47
dBm Step 1 dBm
Default:-105dBm
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Cell1
LAC1
C1 ( Cell1) C1 (Cell2)
A B C
A= 4 dB
B= 6 dB
C= 8 dB
Cell2
LAC2
In case the neighbouring cells belong to different Location Area, a hysteresis is
applied with C1 criteria
• minimizing ping-pong cell reselections
• cellReselectHysteresis (HYS)(SEG) (0…14 dB) Step 2 dB, Default:4dB
Cell Selection with C1 (m)
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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 s C2 =
serving cell:
• C2:
List of 6
strongest
carriers:
• C2:
• C2:
• C2:
• C2:
• C2:
• C2:
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 (m) (REO) (SEG)
0 .. 126 dB
step size: 2 dB
(TEO) (SEG)
0, 10, 20, 30, 40, 50,
60, dB
(PET) (SEG)
20 .. 640 s
step size: 20 s
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cell 1
cell 2
cell 3
C2
time 5 seconds
cell
reselection
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 C1
C1 0 for a period of 5 s
Pathloss Criterion C2
• neighbour‘s C2 value >
current cell‘s C2 value (same LA)
• neighbour‘s C2 value >
current cell‘s C2 value + HYS
(new LA)
for a period of 5 s. Downlink Signalling Failure
DSC 0
RACH Failure
MAX RETRANS + 1 times
Authentication Failure
notification by upper layers
Cell Reselection Events (m)
Cell has been barred
CELL_BAR_ACCESS (BAR)(SEG) &
CELL_BAR_QUALIFY (QUA) (SEG)
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BTS
MS
Downlink radio link
failure detected!
DSCinit := round BS_PA_MFRMS
90
paging message successfully
decoded?
DSC 0
DSC := min (DSC+1, DSCinit) DSC := DSC - 4
yes no
no
yes
Cell Update
DSC = 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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PagingLocUp
# of cells in Loc. area
signalling
traffic
optimum number
of 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 (m)
• 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)
MO
Class
Abbreviated
Name
Range And
Step
Description Default
value
BSC -
MML
Name
BTS –
SEG
allowIMSIAtt
achDetach
Yes/No Defines whether IMSI attach/detach is used in the cell. Yes ATT
BTS -
SEG
timerPeriodic
UpdateMs
0...25.5 h,
step 0.1 h
Defines the interval between periodic MS location
updates.
The value 0 means that the periodic location update is
not used.
0.5 h PER
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6 0 12 25.5 12.5
BSS (BTS) parameter (ZEQO) TIMER PERIODIC UPDATE MS 6 HRS
VLR Parameters (ZMXO) •IMPLICIT IMSI DETACH USED
•IMPLICIT DEREGISTRATION 012 HRS. 30 MIN
•LOITERING 00 DAYS 13 HRS
•VLR 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