Psr Process Flow
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Transcript of Psr Process Flow
PAGING SUCCESS RATE
1.Purpose The purpose of this document is to provide an overview of Paging Strategy analysis.
It also gives direction to the Paging Process, message flows in Paging, performance
monitoring for Paging Success in the network, problems affecting paging performance
and some solutions for the problems.
2.Overview Paging Success Rate (PSR ) gives an indication about the performance of an MSC, in
terms of Terminating Traffic (Voice as well as SMS). Paging Success Rate is calculated
as the ratio of the total no. of successful page attempts (first and repeated) to the total no.
of first attempts.
PAGING SUCCESS RATE= Total No. of Successful Page Attempts/ Total No. of First
Attempts
3.Paging Flow
When a Mobile Station (MS) is paged, a Paging message is sent from the MSC to each
Base Station Controller (BSC) belonging to that MSC's service area (global page), or to
those BSCs serving at least one cell belonging to the LA where the MS is registered
(local page).
For each Paging message received by the BSC, Paging Command messages have to be
sent to all cells belonging to the LA where the target MS is registered. The number of
cells in an LA ranges from a few tens up to perhaps one hundred cells, sometimes even
more. This means that one incoming Paging message to the BSC leads to a considerably
larger number of outgoing Paging Commands from the BSC.
The BTSs have to broadcast all the incoming pages. The Paging Request messages are
sent on the Paging Channel (PCH) on the Common Control Channel (CCCH). Too large
LAs may lead to a too high paging load in the BTS resulting in congestion and lost pages
due to capacity limitation on the air interface.
Smaller LAs reduce the paging load in the BTSs as well as in the BSCs. However,
smaller LAs also mean a larger number of LA border cells in the network. Each time an
MS crosses the boarder between two LAs, a Location Updating is performed. The
Location Updating affects the load on the signaling sub-channels, SDCCH, in the LA
border cells. The SDCCH signaling capacity depends on the SDCCH configuration in the
cell .
4.Paging Strategies
Paging strategy in the MSC is determined by the AXE parameters or the exchange
property settings. With the right paging strategy set in the network, we can always
minimize the unnecessary paging and the risk of paging overload in the interfaces is
always in the minimum level.
5.PAGING PROCESS FLOW
Start
Collect the statistics (Paging Success
Rate) from BO
Start the LAC wise analysis on
the node .
Is the
PSR(Paging
Success
rate)>96%
Stop
Check the Paging
Strategy on basis of
following AXE
parameters from
dbtsp command. 1.PAGTIMEFRST1LA 2.PAGREP1LA 3.PAGTIMEFRSTGLOB 4.PAGREPGLOB 5.PAGTIMEREP1LA 6.PAGTIMEREPGLOB 7.PAGTIMEREPLATA 8.TMSILAIMSC 9.TMSIPAR 10.SECPAGEPATH 11.TIMPAGINGM 12.TIMNREAM
Check the
value of
BTDM,
GTDM
and TDD
from
mgidp and
mgadp
command
respectively.
Check the values
of following
BSC parameters
using rldep and
rlsbp commands
respectively.
1. MFRMS
2. AGBLK
3. BCCHTYPE
& 1. T3212
2. ATT
3. MAXRET
Check
the
EOS-
400
EOS-
398
and
EOS-
3377
Check the
exchange
property PAGNUMBERLA
using
mgepp command.
Recommend a proper value
for each parameter inorder
to improve PSR.
Check for the appropriate values for
various parameters.
Validations
through BO
report.
END
YES
NO
Improved
Check for
PCH
Congestion
(Old
Paging
Mess and
Full Pagng
Queue)
Check for SDCCH Cong-
estion
Check
for
Paging
Load
If PCH DIS>
THRESHLD
Change the MFRMS
values in
the congested
cells
Check for
Paging
Discards, No
of Cells and
recommend for LAC
splitting.
Is
Paging
load>65
%
If
SDCCH
Observed
Check
for
Border
Cells
Change the CRH
parameter
SD Addition can be
done in the possible
cells
NO
YES
YES
YES YES
6.Data collection and Monitoring
We collect the statistics from,
Tools: BO, OSS/Winfiol
Inputs: Updated Capacity Information from BO and LA borders info from Site Data.
7.Data Analysis
The parameters of the best node and worst node are compared in terms of AXEPARS and Paging
Success Rate %.The Object types and counters for checking Paging success rate in CORE and
RADIO Level are:
MSC LEVEL
PAGING
UPDLOCAT
BSC LEVEL
BSCGPRS
LOAS
BSC
LOCATION AREA LEVEL
LOCAREAST
CELL LEVEL
CELLPAG
CLSDCCH
CCCHOLD
RANDOMACC
RANDACCEXT
7.1 MSC Level
Formulas:
Overall Paging Success Rate, P_12_SUC-1 (%) =100x (NPAG1RESUCC +
NPAG2RESUCC) /(NPAG1GLTOT+NPAG1LOTOT)
1st Paging Success Rate, P_1_SUC-1 (%) = 100 x (NPAG1RESUCC)/ (NPAG1GLTOT
+NPAG1LOTOT)
Percentage of 1st Page result into 2nd Page, % 2nd_PAGE (%) 100 x (NPAG2GLTOT
+NPAG2LOTOT)/ (NPAG1GLTOT+NPAG1LOTOT)
Percentage of 1st Global Page, % PAGE1STGLOB (%) = 100 * NPAG1GLTOT/
(NPAG1GLTOT+NPAG1LOTOT)
7.2 BSC Level
Formulas:
Central Processor Load, CPLOAD (%) = ACCLOAD / NSCAN
BSC Paging Discard, BSCPAGDISC (%) = 100 x (TOTCONGPAG / TOTPAG)
7.3 Location Area Level
Formulas:
Paging Intensity, PL_INT (Pages per Second) = (PAGPSBSC+ NLAPAG1LOTOT +
NLAPAG2LOTOT) / 3600 sec
Overall Paging Success Rate, PL_SUC-1 (%) = 100 x ((NLAPAG1RESUCC+
NLAPAG2RESUCC) / NLAPAG1LOTOT)
st
Page Success Rate, PL_1_SUC-1 (%) = 100 x (NLAPAG1RESUCC /
NLAPAG1LOTOT)
Percentage of 1st Page result into 2nd Page, % 2nd_PAG (%) = 100 x
(NLAPAG2LOTOT / NLAPAG1LOTOT) Location Update Success Rate,
LU_SUC_TOT (%) = 100 x (NLALOCSUCC / NLALOCTOT)
7.4 Cell Level
Formulas:
Cell Paging Discard, CELPAGDISC (%) = 100 x (PAGPCHCONG+PAGETOOOLD) /
( TOTPAG+ PAGCSBSC+PAGPSBSC)
If the BSC has more than 1 LA, then the paging ratio between LAs has to be evaluated by
using the establishment cause Answer to Paging in Channel Request message for each
LA in the BSC.
Paging Ratio between LA1, LA_1_Dist = SUM (RAANPAG + RAAPAG1 +
RAAPAG2) for all cells in LA1 / SUM (RAANPAG + RAAPAG1 + RAAPAG2) for all
cells in BSC
Cell Paging Discard, CELPAGDISC (%) =100 x (PAGPCHCONG+PAGETOOOLD) /
{(TOTPAG+PAGCSBSC+PAGPSBSC) x LA_1_Dist}
SDCCH Congestion, SCONG (%) = 100 x (CCONGS / CCALLS)
Random Access Failure, RA_FAIL (%) =100 x RAACCFA / (RAACCFA + CNROCNT)
8. TROUBLESHOOTING
Problems with paging are either due to a fault in the software or congestion, since the
paging function crosses 3 nodes (4 if you include the MS) the first task is to find out in
which node the problem is,whether its MSC, BSC or Cell Level Parameter.
The parameters of the best node and worst node are compared in terms of AXEPARS and
Paging Success Rate %.
8.1 MSC parameters
The following MSC parameters and exchange properties are relevant for paging and
Location Updating:
BTDM implicit detach supervision should be equal (or longer) than T3212 in the BSC. If
T3212 is increased, BTDM must also be increased. Note that BTDM is set in minutes and
T3212 is set in deci-hours.
GTDM is an extra guard time in minutes before the subscriber is set to detached.
TDD sets the time (in days) that an inactive IMSI is stored in the VLR before it is
removed.
PAGTIMEFRST1LA is the time supervision for the page response of the first page. The
MS is paged in the LA with the first page if the Location Area Identity (LAI) information
exists in the VLR. The parameter is set according to the default values.
PAGETIMEFRSTGLOB is the time supervision for the first global page. It is used
instead of PAGTIMEFRST1LA if the LAI information does not exist in the VLR.
PAGEREP1LA decides how the second page is sent:
0 Paging in LA is not repeated
1 Paging is repeated in LA with either TMSI or IMSI
2 Paging is repeated in LA with IMSI
3 Paging is repeated as global paging with IMSI
PAGEREPGLOB defines how global paging is repeated according to:
0 Global paging is not repeated
1 Global paging is repeated with IMSI
PAGTIMEREP1LA is the time supervision for the second page to LA. This is the timer
used for the second page when PAGEREP1LA is set to 1 or 2.
PAGTIMEREPGLOB, the time supervision for the second page, if it is global.
TMSIPAR indicates if TMSI should be used or not:
0 TMSI is not allocated. Note that this setting this
means that TMSI is not used. The paging capacity will
be decreased if TMSI is not used.
1 TMSI is allocated only on encrypted connection
2 TMSI is allocated
TMSILAIMSC states if a new TMSI shall be allocated at a change of LAI within the
MSC/VLR. Only applicable if TMSIPAR is not equal to 0.
0 Allocation only once
1 Allocation on every change of LAI
If TMSI is used it will be used (at least) in the first page. Then, depending on how
PAGEREP1LA is set the page is repeated with either TMSI or IMSI.
However, there will always be some pages that are sent out globally in the first page. The
reason for this is that information about the MS did not exist in the VLR. Normally, this
is due to that the MS was removed from the VLR, due to being inactive for too long (see
parameter TDD above). At an incoming call, the HLR has information about the most
recent location, i.e. VLR, where the MS was registered. Then, when the call is connected
to the VLR a global page will be sent out due to that no information exists in the VLR
about this particular MS. If the MS would have been registered in the VLR but not active,
no page would have been sent out.
The following LATA exchange properties are valid only if the function Equal Access and
Transit Network Selection in MSC/VLR and Gateway MSC (GMSC) is implemented.
This is an optional GSM 1900 function.
LATAUSED defines the usage of LATA administration:
0 LATA administration is not used
1 LATA administration is used
PAGLATA defines if LATA paging is used for mobile terminating calls or not:
0 LATA paging is not used
1 LATA paging is used
PAGREPCT1LA defines how the paging in one location area is repeated, if the first
Paging Attempt was local. This parameter is only valid when PAGLATA is set to 1.
0 Paging in one LA is not repeated
1 Paging in one LA is repeated with either TMSI or
IMSI
2 Paging in one LA is repeated with IMSI
3 Paging is repeated as call delivery LATA paging with
IMSI
PAGTIMEREPLATA defines the time supervision for page response of repeated LATA
paging. After expiration of this timer no new paging repetition for this call is done.
TIMPAGINGM defines the timer for supervision over the Gs-interface. At expiry of the
timer, according to the parameter SECPAGEPATH.
SECPAGEPATH defines over which interface
0 No paging.
1 Paging over the Gs-interface.
The default values of the MSC Parameters are given below:-
PARAMETERS
DEFAULT
VALUE COMMANDS
PAGTIMEFRST1LA 4 dbtsp:tab=axepars,name=PAGETIMEFRST1LA;
PAGETIMEREP1LA 7 dbtsp:tab=axepars,name=PAGETIMEREP1LA;
PAGETIMEFRSTGLOB 4
dbtsp:tab=axepars,name=PAGETIMEFRSTGLOB
;
PAGETIMEREPGLOB 7 dbtsp:tab=axepars,name=PAGETIMEREPGLOB;
PAGEREP1LA 2
dbtsp:tab=axepars,setname=GSMMMSC,name=
PAGEREP1LA;
PAGEREPGLOB 0
dbtsp:tab=axepars,setname=GSMMMSC,name=
PAGEREPGLOB;
TMSILAIMSC 0
dbtsp:tab=axepars,setname=GSMMMSC,name=
TMSILAIMSC
TMSIPAR 0
dbtsp:tab=axepars,setname=GSMMMSC,name=
TMSIPAR;
SECPAGEPATH 1
dbtsp:tab=axepars,setname=GSMMMSC,name=
SECPAGEPATH;
TIMPAGINGM 9
dbtsp:tab=axepars,setname=GSMMMSC,name=
TIMPAGINGM;
BTDM 240 MGIDP;
GTDM 6 MGIDP;
TDD 4 MGAPP;
TIMNREAM
15 dbtsp:tab=axepars,name=TIMNREAM;
8.2 BSC parameters
In this section some of the most important BSC parameters for paging performance are
explained
MFRMS is the multi-frame period and defines the transmission interval of paging
messages to the same paging group.
AGBLK sets the number of CCCH blocks in each multi-frame that will be reserved for
access grants. Setting AGBLK to a value other than 0 will reduce the paging capacity.
BCCHTYPE can be either:
COMB = Combined; the cell has a combined BCCH,
CCCH and SDCCH/4.
COMBC = Combined with CBCH; The cell has a
combined BCCH, CCCH and SDCCH/4 with a CBCH
sub-channel.
NCOMB = Not combined; The cell does not have a
SDCCH/4.
If COMB is used the maximum capacity of the CCCH will decrease to a third (If
AGBLK set to 0), compared to the NCOMB case.
T3212 is the time between the periodic registration.
ATT determines if attach/detach is allowed.
MAXRET defines maximum number of retransmission of MS may do when accessing
the system on RACH. The settings parameter must be always in the optimum level
because this is the trace off between call success and the paging capacity in the cell.
CRH is the hysteresis value used when the MS in idle mode crosses an LA border. As
default this parameter is set to 4. A higher setting might be advantageous in areas with
many LA borders and thus problems with many Location Updating.
PAGLIMIT defines the max number of paging orders allowed to be sent to the TRH per
second. Set per BSC as a BSC Exchange Property. Since there are also other mechanisms
in the BSC that prevents overload due paging, there should normally not be any need to
change the parameter value. The only case when reducing it can be useful is o preventing
congestion on the paging channel PCH.
The default values of the BSC Parameters are shown below :-
PARAMETERS
DEFAULT
VALUES COMMANDS
PAGLIMIT 0 RAEPP;
MFRMS 6 RLDEP:CELL=ALL;
AGBLK 1 RLDEP:CELL=ALL;
BCCHTYPE NCOMB RLDEP:CELL=ALL;
T3212 40 RLSBP:CELL=ALL;
ATT YES RLSBP:CELL=ALL;
MAXRET 4 RLSBP:CELL=ALL;
9. Improvement Solution
If there is any finding then the solution is recommended to that finding.
For improvement change, design as well as configuration is checked. Some Timers and
MSC Parameters need to be change and coordinate with Radio Capacity and parameters
setting.
9.1 A and Abis INTERFACE
› Compare paging message received by BSC side and paging message sent by MSC
side, if the difference is big, it means that A interface should have problem, such
as congestion.
› Need core engineer assistance, to check A interface, expand A interface.
› If the value of COVERLOAD (LAPD) is high, it means that the LAPD signaling
is overload.
› Adjust LAPD concentration method, or expand ABIS interface.
9.2 Um INTERFACE
› Adjust paging strategy: change to TMSI paging, increase single paging block.
capacity, therefore increase the paging message volume through Um interface.
› Check BCCHTYPE setting, adjust COMB to NCOMB to add more CCCH
channels
› Optimize AGBLK and MFRAMS setting.
› Control the coverage area of cells by adjusting antenna bearing and down tilt,
avoid cells with high traffic and large coverage area.
› Optimize LAC plan, reduce LAC size to decrease the paging message volume in
this LAC.
9.3 Congestion and Rand Access
› SDCCH congestion impacts paging - Add more SDCCH channels
› Optimize cell coverage
› Optimize LAC border
› Using features: Adaptive configuration of logical channels, Immediate assignment
on TCH, Increased SDCCH capacity.
› Expansion.
› Low Rand Access performance
› Frequency optimization
› Optimize cell coverage
› Hardware check
› Parameter optimization: ACCMIN, MAXTA…
9.4 UL /DL Unbalance and LAC border
› Unbalance in UL/DL
› Control cell coverage
› Check antenna, cable and connectors
› Install TMA
› Optimize LAC border
› Do not set LAC border in dense region of people, such as main road, plaza, and
train/bus station.
9.5 TIMERS Optimization
› T3212 and BTDM
› BTDM should equal or be more than T3212, the correct setting of BTDM should
be a multiple of T3212
› T3212 settings for all cells should be the same in one BSC
› According to different coverage environment, reducing properly the value of
T3212 and BTDM can increase paging performance and user satisfaction
› Shorten the setting of BTDM to decrease the unwanted paging message
› After changing T3212 and BTDM, SDCCH capacity should be evaluated again
9.6 Coverage Optimization
› Most of no paging responses are caused by poor/no coverage.
› Enhancing coverage is the best method to improve paging performance.
› We can find out the problem cells by tracing feature, then point out the poor/no
coverage area.
› Power adjustment or using the antennas with bigger gain.
› Adjust antenna to enhance the coverage.
› Install repeater to compensate the coverage.
› Install indoor system to strengthen in-building coverage.
› Add more sites.
9.7 Tracing no paging response
› Analyze the distribution situation of users with no paging responses, check if they
locates in the poor/no coverage area, then give suggestions to strengthen the
coverage of these areas
› Analyze the cell situation resided recently by user with no paging response, to
check if there are some problems in that cell (hardware, parameter…), then give
advices to troubleshoot
› We can find out the msisdn with no paging response and the cell information
resided by the MS by analyzing tracing log
› Then we can point out the important areas with poor/no coverage
› And also, we can call back to the users with no paging response to see what was
the situation We can find out the phone number with no paging response and the
cell information resided by the MS by analyzing tracing log
› Then we can point out the important areas with poor/no coverage
› And also, we can call back to the users with no paging response to see what was
the situation at that time
9.8 Blocks for tracing in MSC MPAG
MRRM
MTB
9.9 Blocks for tracing in BSC
RMPAG
RMRCS
10.Improvement Solution Execution Improvement plan is shared with circle D&P team for raising CR and get it executed by
GNOC-CM team
11.Validation after Execution After the change is executed, performance data is again fetched from BO and compared
with the data collected initially.If the improvement is remarkable, shows change is
successful, else change will be reverted and data will be analyzed again.