bsspar-idle mode operation
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BSSPAR
Idle Mode Operation
Training Document
BSSPAR CTXX 03
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Contents
1 Module Objectives................................................................................4
2 Idle Mode Control.................................................................................5
3 PLMN Selection....................................................................................83.1 PLMN Access Parameters...................................................................93.2 Cell and Location Area Parameters...................................................103.3 Measurement Reporting ...................................................................12
4 Cell Selection & Reselection.............................................................14
4.1 C1 Criterion 154.2 C2 Criterion 164.3 C31 & C32 Criteria............................................................................19
5 Location Updates...............................................................................205.1 IMSI Attach & Detach........................................................................22
6 Key Learning Points...........................................................................24
7 Review Questions ..............................................................................26
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1 Module Objectives
At the end of the module, the participant will be able to:
List the functions of the MS during the idle mode
Explain the parameters used for PLMN and cell selection
State the purpose of location updates and the associated parameters
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2 Idle Mode Control
Because of the limited radio spectrum that is available, each MS cannot be
allocated a dedicated traffic channel (TCH) at all times. Traffic channels areonly allocated to the user when the need arises. This leads to the distinction
between two states that the mobile can take, namely Idle Mode and Dedicated
Mode.
In the idle mode, an MS does not have a dedicated traffic channel (TCH). It
listens to and transmits on the broadcast channels. All requests for transmission
resources are made while in idle mode. Once the resources are allocated for full
duplex point-to-point communication, the mobile moves from idle mode to
dedicated mode.
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/S
Why to camp on a specific cell?
PLMN selection Cell selection & re-selectio Location updates
Idle Mode Tasks
Figure 1. Idle mode operation
During the idle mode, the MS has to perform a number of functions:
(a) During Power On it has to check if it can access a PLMN and cell.
(b) It has to stay in contact with the BTS by decoding the BSIC and listening to
System Information messages.
(c) Listening to BTS transmission for paging messages to see if it being called.
(d) Monitor the status of radio links from various BTS and choose the most
appropriate BTS.
(e) Listen for cell broadcast short messages.
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locationAreaId
ncc (Network C olour C ode) 0 7bcc (BTS Colour Code) 0 7
bsIdentityCode
cell-ID 0 65535
Parameter Value
trainingSequenceCode 0 7
mcc (Mobile Country Code) 0 999mnc (Mobile Network Code) 0 99lac (L ocation Area Code) 0 65535
Cell G lobal Identity MCC + MNC + LAC +
Figure 2. IDs and ID codes
When the mobile station is in idle mode, it needs some information about the
GSM network in order to know the right frequencies and find the right cells.
This information pertains to Radio Resource Management and to Mobility
Management and includes:
The access parameters to the PLMN
Location Area Identification (LAI), which is composed of the MobileNetwork Code (MNC), the Mobile Country Code (MCC) and Location
Area Code (LAC). LAI = MCC + MNC + LAC
Cell Identification Code
Base Station Identity Code (BSIC) including Network Colour Code
(NCC) and Base Station Colour Code (BCC).
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BSIC is a combination of NCC and BCC
Reported in Measurement Results to BSC
Can be listed in Hex or Decimal
NCC (0...7) BCC (0...7)
4 2 U 4 2 U
32 16 8 4 2 U Range
0 0 0 x x x 0 - 7
0 0 1 x x x 8 - 15
0 1 0 x x x 16 - 23
0 1 1 x x x 24 - 31
1 0 0 x x x 32 - 39
1 0 1 x x x 40 - 47
1 1 0 x x x 48 - 55
1 1 1 x x x 56 - 63
Figure 3. Base Station Identity Code (BSIC)
Once the base station is identified within the network, the initial frequency must
be set for each TRX.
The basic idea in the GSM system is that the mobile is always within the cell
offering the best coverage and that the system knows where the MS is located.
In idle mode, mobility is ensured by setting the following criteria and timers:
Cell selection criteria based on C1 or C2 comparison
Location Update
IMSI attach/detach
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3 PLMN Selection
When a mobile station is switched on, it tries to locate a GSM network. If the
MS is in the home country, it naturally tries to find the home network. If there iscoverage, the MS camps on the home network. If there is no coverage, the MS
attempts to find other networks of competitive operators and this is called
national roaming. Usually this is not possible because different operators are in
competition with each other. Then the only possibility of finding a network in
the home country is to find the home network.
When the MS is abroad, international roaming is usually possible. The Mobile
can select any operator offering GSM service in the foreign country, with which
the operator of the home network has a roaming agreement. The issue is how
the MS selects the network in a foreign country. There are 3 possibilities:
1. The home operator can make a list of preferred operators in different
countries. This list of preferred networks is not used.
2. The MS just selects the network with the best field strength level found
where the mobile is switched on. The Mobile camps on the network
selected and stays on it as long as service (coverage) is available. Usually,
the selection is made based on the field strength level only.
3. Home operator can give a list of forbidden networks.
The PLMN selection criteria mentioned above are chosen by the operator and
they cannot be affected with the parameters which will be discussed next.
An operator can control PLMN selection in a number of ways:
a) Specify a class of MS that is allowed to access a particular cell.
b) Specify the minimum received level signal strength required by the MS.
c) Bar some cells from user access except for emergency calls.
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plmnpermitted 0 ... 7
Parameter Value
NOTEThis parameter is confusing. Its not used fornetworkselection. Its used AFT ER a network has beenselected so thatmeasurementsfrom only one PLM N are reported
Two M odes
Automatic - utilises a list of P LM Ns in priority order. Highest priori(available and allowable) PLMN is selected
Manual - MS indicates to user which P LM Ns are available Three Types of Lists
P referred
Found
Forbidden
Figure 4. PLMN Selection
3.1 PLMN Access Parameters
A number of parameters are needed to control which MS is allowed to access a
PLMN, BTS or Cell.
The parameter notAllowedAccessClasses (ACC)(BTS)(0..9, 11..15) tells
which mobile user classes can not use a particular cell. This allows the operator
to divide the subscriber database into different Access Control Classes and
hence gives the operator some control over the existing load and access to
priority users in congested cells.
The plmn-permitted (PLMN)(BTS)(0..7) parameter is broadcast on the BCCH
and is used by the mobile to report measurements of that PLMN. This
parameter is used after the network selection has been done. The BSIC (Base
Station Identity Code) is broadcast on the SCH, so when the mobile pre-
synchronises, it knows if the BTS belongs to the right PLMN or not (BSIC is
screened by plmn-permitted (PLMN)(BTS)).The parameterplmn-permitted (PLMN)(BTS)(0..7), doesnt affect the PLMN
selection, it is only used for measurements reporting.
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3.2 Cell and Location Area Parameters
AN MS needs information about cell identities. First, there is identity of the
each cell (cell-ID) and in addition to this cell-ID more IDs, which are used forlocation information.
ParameterlocationAreaId (LAC)(BTS) includes the following:
Mobile Network Code, mnc (0..99),
Mobile Country Code, mcc (0..999) and
Location Area Code, lac (0..65535) which describes each location
area as shown in Figure 5.
Location Area Code
MNC =Operator
MCC =Country e.gFinland
LAC 1 =Helsinki LAC 2
LAC 3 LAC 4BSC
BTSBTS BTS1 2 n
Figure 5. Description of a location area.
There is other information used for Radio Channel Management purposes.
Some information is needed in order to separate co-channels used in different
Base Stations in the vicinity as shown in Figure 6.
ParameterbaseStationIdentityCode (BCC)(BTS) includes
Network Colour Code, ncc (0..7) and
Base Station Colour Code, bcc (0..7)
It is possible to set these parameters into the Background Database, to
minimise downtime.
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BaseStationColour Code
f1
f2
f3
f1
f1
bcc=1
bcc =2
bcc =3
Figure 6. Base Station Colour Code.
Parameter Value
bCC HAllocation-ID 1 ... 255bCCHAllocationList 1 ... 124 in GSM (max. 32freq. for all bands)
idleStateBCCHAllocation 0 (BCCH list is taken from the adjacent cell)1 ... 255 (number of the BC CH list used)
measurementBCCHAllocation ADJ (BCCH frequency list taken from adj. cIDL E (active MS uses same list as MS in IDL
initialFrequency 1..124 & 975..1023, 0; 512..885 GSM900;1800 (FRE
Figure 7. Frequencies
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3.3 Measurement Reporting
After the MS accesses one network, it reports the measurements of the network
to the BTS on which it is camped. However, there are also some other
requirements to access one cell. Having coverage might not be enough to access
some particular cells.
The parameter RxLevAccessMin (RXP)(BTS)(-110..-47 dBm) describes the
minimum value of received field strength required by the MS to get any service
from the network in that cell in idle mode.
However, there are still some cases, even if there is good field strength where,
the operator may want to make some tests to keep a cell out of use. For this kind
of purposes the cell can be changed to barred state by using the parametercellBarred (BAR)(BTS)(Yes/No) parameter.
An example of using cell barring for test measurements is given in Figure 8.
Cell Barred
Existing LayerBarred, No
New Microcell LayerBarred, Yes
Easy to test new Microcells with NMS/X 5.24 with Nokia 2110
GPS-satelite
NMS/X 5.2
Figure 8. Use of Cell Barring for test measurements.
NOTE: All adjacent cells have to be also barred.
A Mobile can not use any cell for call establishment, which is in barred state.
An exception to a barred cell could be implemented using parameter
emergencyCallRestricted (EC)(BTS)(Yes/No). This parameter tells if the
mobile has right to use the network for emergency calls even if it has no right to
use the network for normal calls. Only for MS classes 11 to 15.
The network also broadcasts (on the BCCH) some parameters related partly to
network planning to mobiles. When the mobile is moving in Idle mode it has to
know which is the best cell offering service in each area.
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CellReselectHysteresis (HYS)(BTS)(0..14 dB) is a parameter that the mobile
uses as a margin in the comparison of the field strength levels of the adjacent
cells in different Location Areas in Idle mode. This margin prevents ping-pong
location updates, which will result in a waste of SDCCH capacity.
The other parameter which is actually directly related to frequency planning is
msTxPwrMaxCCH (TXP)(BTS)(13..43 dBm) which tells the mobile the
maximum transmitting power when accessing the system.
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4 Cell Selection & Reselection
One basic idea in the GSM system is that the Mobile Station is always within
the cell offering the best coverage. In Dedicated mode this is handled byhandovers, but in Idle mode the concept of handover does not exist because the
MS does not have a dedicated channel. Mobile has to find the best cell in each
area. There is a process for this purpose called Cell Selection, based on C1 or
C2 comparison.
The idea is that the Mobile compares field strength levels coming from different
BTSs and selects the best BTS. The mobile uses the parameter
CellReselectHysteresis (HYS)(BTS)(0..14 dB) parameter between cells that
belong to different Location Areas in order to avoid the "Ping-Pong"
phenomenon. This means that before the mobile changes to a different cell in
Idle mode, between different location areas, the field strength level of the new
cell has to be at least the value ofCellReselectHysteresis (HYS)(BTS) betterthan the value of the serving cell.
There is no margin between the cells that belong to the same Location Area.
The equation for the cell selection is presented next.
Two methods for selecting a cell:
Normal cell selection(a)- MS has no prior knowledge of which RF chanBCCHStored list cell selection - optional(b)- MS uses list of BCCH carriers used
PLMN
If no suitable cell is found using method(b)then(a)is tried.
What constitutes a 'suitable' cell:
Cell is in the selected PLM NCell is not barredIt is not in a forbidden location area for national roamingC1 >0 (range -99..0..+99)If there is no normal priority cell then low priority cell
Figure 9. Cell Selection in Idle mode
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4.1 C1 Criterion
The C1 criterion has been designed to maximise transmission quality. It takes
into account the following
L = Average Level of the signal received by the mobile station on the
beacon frequency.
p1 = RxLevelAccessMin (RXP)(BTS)(-110 -47 dBm) discussed
earlier.
M = Maximum RF power of the MS based on the MS specifications.
p2= MxTxPwrMaxCCH(TXP)(BTS)(13 43 dBm) discusses earlier
C1 is defined as follows
C1 = (A Max (B, 0))
Where A = L p1
And B= p2 M
When looking for cells (neighbouring or during Power On), only cells of
positive C1 computed from the broadcast parameters p1 and p2 values are taken
into account. The cell with the best C1 is chosen. Thus the C1 criteria is used to
determine the coverage limit of each cell and the boundary between adjacent
cells.
A practical example of C1 radio criteria is shown in Figure 10
Radio Criteria
C1 = (A - Max(B,0))
A = Received Level Average - p1
B = p2 - Maximum RF Output P ower of the Mobile Station
p1 =rxLevelAccessMin(Min. received level at the MS required for accesssystem)
(RXP BTS -110..-105 -47dBm)
p2 =msTxPowerMaxCCH(Max. Tx power level an MS may use when accessystem)
(TXP BTS GSM900 5..33..43/2 33; GSM1800
0..30/2 30dB m)
rxLevelAccessMin -110 ... -47dBm 'RXP' (BTS)
msTxPowerM axCC H 0 30dBmGSM1800 (5 43dBmGSM900)'TXP' (BTS)
Parameter Value
Figure 10. Cell (Re-) Selection in Idle modeUsing C1 criterion
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A = 4 dB
B = 6 dB
C = 8 dB A B C 1 2
1
2
MS Moving
A B C
LA 1 LA2
cellReselectHysteresis 0 14 dB 'HYS' (BTS) 2dB steps MMLdef4dB
Parameter Value
Figure 11. Cell selection based on C1 in practice.
(There is a margin only between cells that belong to different location areas.)
4.2 C2 Criterion
The criterion C1 is used in Phase 1. C2 is used in GSM phase 2 with more
features, for use with two-layer microcell / macrocell architecture. C2 uses more
parameters:
Cell re-selection is needed if
P ath Loss criterion C1 < 0 for cell camped on ,for more than 5 seconds.
There is DL signalling failure
The cell camped on has become barred.
There is a better cell in terms of C2 criterion
A random access attempt is s till unsuccessful aftermaxNumberRetransmissionrepetitions.
MS will calculate the C 1 and C 2 for the serving cell, every 5 s
MS will calculate the C 1 and C 2 for the six best neighbour cells, every
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Figure 12. Cell Re-selection in Idle Mode
Using C2 Re-Selection Criterion (PH 2 MS)
The parametercellReselectParamInd (PI)(BTS)(Yes/No)becomes activated if
C2 parameters are sent to the Mobile (activates C2), and the parametercellBarQualify (QUA)(BTS)(Yes/No) controls whether the cell barring can be
overridden.
BCCH
BCCH
fast moving mobil
slow moving mobile
C2
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C1 + cellReselectOffset - temporaryOffset*H(penaltyTime-T)
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During time 0..19 sec (within the set penaltyTime):
C2 =C1+cellReselectOffset-temporaryOffset * H(penaltyTime-T)
C2 =32+20 -30*1
C2=22
=> C2 < C1, so MS will be kept in macro layer i.e. target cell (micro cell) is
NOT attractive.
1. During time 20.. (penaltyTime over):
C2=C1 +cellReselectOffset-temporaryOffset*H(penaltyTime-T)
C2=32+20-30*0
C2=52
=>C2 > C1, now target cell is very attractive and the idle mode MS will
camp on the microcell.
If the C2 > C1 before the penalty time is over, the cell reselection will be done
immediately.
If the C2 = C1 before the penalty time is over, the cell reselection will not be
done until the penalty time is expired.
Note that C2 is just meant for idle mode.
4.3 C31 & C32 Criteria
There are other criteria C31 and C32, which are used in GPRS. For further
information, see the module BSSPAR: GPRS & EGPRS (EDGE).
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5 Location Updates
A subscriber keeps moving from one place to another and the network must be
able to locate it for incoming calls. The transaction that enables the network tokeep track of the subscriber is called a Location Update. The mobile phone
constantly receives information sent by the network. This information includes
the VLR area in which the mobile is currently located. In order to keep track of
its location, the mobile stores the ID of the area in which it is currently
registered. Every time the network broadcasts the ID of the area, the mobile
compares this information to the area ID stored in its memory. When the two
IDs are no longer the same, the mobile sends the network a request, i.e. a
registration inquiry to the area it has just entered. The network receives the
request and registers the mobile in the new VLR area. Simultaneously, the
subscribers HLR is informed about the new VLR location and the data
concerning the subscriber is cleared from the previous VLR as shown below.
Figure 16. Elements involved in location update
Figure 17 Location update procedures
The VLR area is commonly referred to as a location area. As defined in GSM
specifications, it is the smallest area, into which a terminating call towards a
mobile subscriber will be paged. Also a location area is the area in which a
mobile needs not to update its location with its home location register.
Location update is performed in idle mode when the mobile is roaming into acell having a different location area code (LAC). In connected mode, the mobile
will update its location with the network as soon as it becomes idle again, i.e.
after call completion.
While handover boundaries affect only mobiles that are in connected mode,
location area boundaries affect all mobiles in the network, including the (many)
idle mobiles.
Location updating causes signalling and processing load across the entire
network hierarchy up to the mobiles HLR. In case of foreign roaming mobiles
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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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(tourists), this is often even international signalling traffic. Therefore planning
of location area boundaries should be considered with some thought, such as to
avoid oscillating location updates along a heavily frequented road.
Furthermore, different MSCs can not use the same LAC, otherwise the BSCwill not know to which MSC the mobile belongs.
In a location area, there is a trade-off between paging traffic and location
updating traffic. This means that concatenating e.g. a large city into a single
location area will avoid any location updating traffic, but on the other hand
causes a maximum in paging traffic, since every single terminating call within
the area is broadcast to every single cell in the area. (Even several times per call
attempt, depending on network parameters). This can cause significant traffic
loads within the network.
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
Figure 18. Trade-off between location update and paging traffic
Location updates are carried out every time a Mobile changes its location area
under one MSC, or between two different MSCs. When the location area
changes between two MSCs, the HLR is updated.
There are two types of location updates: automatic (random) location update
and periodic location update.
An automatic location update occurs when the Mobile is switched on if
IMSIAttachDetach (ATT)(BTS)parameter is used.
Periodic location updates carried out by the Mobile Station and is used to checkthat the location information in MSC/VLR is correct, because by error in the
MSC/VLR, the location information of Mobile Station can disappear. Periodic
location update is controlled by the timerPeriodicUpdateMS (PER)(BTS)
(0.0..25.5 hours) parameter.
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timerPeriodicUpdateMS 0.0 ... 25.5 hrs 'PER' (BTS) see note in dictiallowIMSIAttachDetach Yes/No 'ATT' (BTS)
Parameter Value
MS => MS C / VLR
Mobile Station switched ON
IMSI Attach / Detach
Same Location Area => No Location Update
Different Location Area => Location Update
Change of the Location Area
Location Area under the same MS C / VLR
Location Area under another MSC / VLR => HLR will be u
Service is rejected (MS unknown in VLR)
Time-P eriodic LU (MS -> MSC/VLR)
Figure 19. Location Updates
5.1 IMSI Attach & Detach
The IMSIAttachDetach (ATT)(BTS)(Yes/No) parameter is used to decreasesignalling load. The Mobile Station sends a message to the MSC notifying that
it is switching on or off. When the MSC knows that the Mobile Station is
switched off it does not try to page it, and useless paging is avoided.
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Search all the RF channels, take samples during3-5 s and calculate averages. And put them inascending order with respect to signal level.
Then tune to the strongest RF channel.
Search for the frequency correction burst in thatcarrier in order to verify if it is a BCC H carrier
Camp on the cell
T ry to synchronize to the carrier and readthe BC CH data
Is it a BCC Hcarrier?
Is it a correctPLMN ?
Is the cell ba rred?
Is C 1>0
Tune to the next highestRF channel which is not
tried before
No
No
NoNo
Y es
Y es
Y es
Y es
Figure 20. Normal Cell Selection
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6 Key Learning Points
During the idle mode, the MS has to perform a number of functions:
1. During Power On it has to check if it can access a PLMN and
cell.
2. It has to stay in contact with the BTS by decoding the BSIC
and listening to System Information messages.
3. It has to listen to BTS transmission for paging messages.
4. It has to monitor the status of radio links from various BTS
and choose the most appropriate BTS using C1 and C2 criteria.
5. It has to listen for cell broadcast short messages.
The parameters used by operators to control PLMN and cell selection and cell
reselection are:
notAllowedAccessClasses (ACC)(BTS)(0..9, 11..15) allows an
operator to define the MS access classes that are not allowed to access a
cell.
plmn-permitted (PLMN)(BTS)(0..7) which is broadcast on the
BCCH and is used by the mobile to report measurements of that PLMN
rxLevAccessMin (RXP)(BTS)(-110..-47 dBm) which describes the
minimum value of received field strength required by the MS to get any
service from the network in that cell, in idle mode.
cellBarred (BAR)(BTS)(Yes/No) parameter to keep a cell out of use
for testing purposes. An exception to a barred cell could be implemented
using parameteremergencyCallRestricted (EC)(BTS)(Yes/No).
cellReselectHysteresis (HYS)(BTS)(0..14 dB) is used as a margin in
the comparison of the field strength levels of the adjacent cells in different
Location Areas in idle mode. This margin prevents ping-pong location
updates, which will result in a waste of SDCCH capacity.
msTxPwrMaxCCH (TXP)(BTS)(13..43 dBm) tells the mobile the
maximum transmitting power when accessing the system.
cellReselectParamInd (PI)(BTS)(Yes/No) becomes activated if C2
parameters are sent to the Mobile.
cellBarQualify (QUA)(BTS)(Yes/No) controls if the cell barring can
be overridden or not.
penaltyTime (PET)(BTS)(20..640 s) describes the time delay before
the final comparison is made between two cells.
temporaryOffset (TEO)(BTS)(0..70 dB) describes how much field
strength could have been dropped during this penalty time.
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cellReselectOffset (REO)(BTS)(0..126 dB) describes an offset to
cell reselection.
Location information is updated by the MS to the network at a regular interval.
This is necessary for the paging to be carried out efficiently by the network.Each paging message is sent from every cell in a location area.
Location updates are carried out every time a Mobile changes its location area
under one MSC, or between two different MSCs. When the location area
changes between two MSCs, the HLR is updated. There are two types of
location updates: automatic location update and periodic location update.
Periodic location updates are carried out by the MS to update the location
information in the MSC/VLR. The interval is set by timerPeriodicUpdateMS
(PER)(BTS)(0.0..25.5 hours) parameter.
The IMSIAttachDetach (ATT)(BTS)(Yes/No) parameter is used to indicate
that an MS is switched off. The MSC does not try to page thus avoiding
unnecessary paging. An automatic location update occurs when the Mobile is
switched on ifIMSIAttachDetach (ATT)(BTS)parameter is used.
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7 Review Questions
Q1. Which of the following functions are not performed by an MS in idle
mode?
a) During Power On it has to check if it can access a PLMN and cell.
b) It has to stay in contact with the BTS.
c) Listen to BTS transmission for paging messages.
d) Monitor the status of radio links to various BTS and choose the most
appropriate BTS using C1 and C2 criteria.
e) Listen for cell broadcast short messages.
f) Listen to RACH messages from other mobiles.
The answers to choose for questions Q2-Q5 are given below a) - e):
a) notAllowedAccessClasses (ACC)(BTS)(0..9, 11..15)
b) plmn-permitted (PLMN)(BTS)(0..7)
c) rxLevAccessMin (RXP)(BTS)(-110..-47 dBm)
d) cellBarred (BAR)(BTS)(Yes/No)
e) cellReselectHysteresis (HYS)(BTS)(0..14 dB)
Q2. Which parameter is used as a margin to prevent ping-pong locationupdates?
Q3. Which parameter is used to keep a cell out of use for testing purposes?
Q4. Which parameter describes the minimum received field strength required
by an MS to get any service from the network in that cell in idle mode?
Q5. Which parameter allows an operator to define MS access classes that are
not allowed to access a cell?
Q6. Which parameter given below is used to tell the mobile the maximum
transmitting power when accessing the system.
a) msTxPwrMaxCCH (TXP)(BTS)(13..43 dBm)
b) cellReselectParamInd (PI)(BTS)(Yes/No)
c) cellBarQualify (QUA)(BTS)(Yes/No)
d) penaltyTime (PET)(BTS)(20..640 s)
e) temporaryOffset (TEO)(BTS)(0..70 dB).
f) cellReselectOffset (REO)(BTS)(0..126 dB)
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Q7. When are location updates carried out?
a) Every time an MS changes its location area under one MSC.
b) Every time an MS changes between two different MSCs.
c) On a periodic basis set by timerPeriodicUpdateMS (PER)(BTS)(0.0..25.5
hours) parameter.
d) All of the above.
Q8. Which of the following is true about IMSIAttachDetach (ATT)(BTS)
(Yes/No) parameter?
a) It is used to indicate that a BTS is switched on.
b) Its purpose is to avoiding unnecessary paging by the BSC.c) An automatic location update occurs when the Mobile is switched on
ifIMSIAttachDetach (ATT)(BTS)parameter is used.
d) It is used for periodic location updates carried out by the MS to
update location information in MSC/VLR.
e) All of the above.