idle mode_operation_v1.1_chema

1 © Nokia Siemens Networks

BSSPAR1: Chapter 3 Idle 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


• 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


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


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


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


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


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


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


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


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)


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


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


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


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)


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


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


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


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


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