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.