3g counters and kpis for paging

1 Pavel Romanenko/NWS LTE RA E2E SA NE © Nokia Siemens Networks

3G counters and KPIs for Paging


Agenda

• Counters and KPIs defined for Paging procedure and the RRC Connection

• Detailed investigation by using Iub, RRC and Traffic measurements


Counters and KPIs

• It is possible to have counters for messages discarded by RANAP or RC3.

• With some assumption it is possible to monitor the cell flow through the RRC-c master and MAC-c.

• The starting point A is given by the L3Iu counter:

• This counter returns the paging messages received from CN.


Counters and KPIs

Paging Flow in RNC - RANAP

• Iub mater in RANAP functional block forward the received paging message to UTRAN.

• Only a check on load is performed when UTRAN/RANAP receive a RANAP: Paging message from CN/RANAP.


Counters and KPIs

• In case of RNC is not capable to forward the paging message due to over-load condition as in Table above the counter M1003C47 DEL_PAG_MSG_ICSU_OVERLOAD is incremented.

• As result, having counter granularity of 1hour, the Iuv Flow (msg/sec) can be:

• Iub_Flow = M1003C36 REC_PAG_MSG - M1003C47 DEL_PAG_MSG_ICSU_OVERLOAD / 3600 (msg/sec)



Counters and KPIs



• RANAP forward paging messages to RC3 entity in RRMU that checks the load

• If no overload is detected the paging messages is forwarded normally.

• If the number of “unhandled messages” become greater than 550 the RC3 entity start discarding messages.

• The related counter M1003C48 DEL_PAG_MSG_RRMU_OVERLOAD is incremented

• As result, having counter granularity of 1hour, the RC3 Flow (msg/sec) can be:

• RC3_Flow = M1003C36 REC_PAG_MSG - M1003C47 DEL_PAG_MSG_ICSU_OVERLOAD - M1003C48 DEL_PAG_MSG_RRMU_OVERLOAD / 3600 (msg/sec)

Counters and KPIs



• When number of “unhandled messages” in RRC Master become greater than 100 the RRC Master entity start reading the messages and counting the paging messages.

Counters and KPIs

Paging Flow in RNC - RRC


• If all the “unhandled 100 messages” are all paging messages RRC starts discarding otherwise it create/fill buffer in DMCU.

• When buffering a paging message the RRC master associate the correct DRXcycle to be used for the message.

• The RRC Master can be considered the trigger entity for counters:

• M1006C25_PAGING_TYPE_1_CN_ORIG

• M1006C26_PAGING_TYPE_1_RNC_ORIG (Cell-PCH)

• M1006C27_PAGING TYPE 2_ATT

• As result, having counter granularity of 1hour, the RRC Flow (msg/sec) can be:

• RRC-c_Flow = (M1006C25_PAGING_TYPE_1_CN_ORIG + M1006C27_PAGING TYPE 2_ATT +

• M1006C26_PAGING_TYPE_1_RNC_ORIG / 3600 (msg/sec)

Counters and KPIs

Paging Flow in RNC - RRC


Counters and KPIs

Paging Flow in RNC - MAC


• MCFTOR entity are responsible for scheduling paging messages to a cell.

• MAC-c scheduling over PCH channel monitoring is available using the following counter:

• M1000C70 AVE_PCH_THROUGHPUT

• M1000C71 PCH_THROUGHPUT_DENOM_0

• Considering that in actual NSN configuration 1 paging message takes 80bits, using the following formula it is possible to have the MAC-c Flow (msg/sec)

• MAC-c Flow = (M1000C70 AVE_PCH_THROUGHPUT / M1000C71 PCH_THROUGHPUT_DENOM_0) / 80 (msg/sec)

Counters and KPIs

Paging Flow in RNC - MAC


P_Blocking - KPI

• Paging messages from CN to UTRAN (repetition included) are given by M1003C36 _REC_PAG_MSG_.

• Results from this counter can be aggregated by PLMN-RNC, RMSC, RSGSN, MCC-MNC.

• Results from this counter can be compared with the sum of M1006C25 _PAGING_TYPE_1_CN_ORIG and M1006C27_PAGING TYPE 2 ATT to have an indicator for the overall procedure (Iuv, RC3, RRC Master and DRX)

• Possible KPI (valid at LA/RA area) to have the overall (Iuv, RC3, RRC Master and DRX) UTRAN blocking probability per LA (or CN-UTRAN failure rate), could be:

• P_Block (overall) = 1 - (M1006C25_PAGING_TYPE_1_CN_ORIGLA + sum_cell_LA(M1006C27_PAGING TYPE 2 ATT)) / sum_CN_id(M1003C36_REC_PAG_MSG).

Counters and KPIs


P_Blocking - KPI

where the M1006C25 _PAGING_TYPE_1_CN_ORIGLA indicates the minimum of the counters:

006C25 _PAGING_TYPE_1_CN_ORIG among all the cells of same LA/RA, having PCH_availability=1 and cell_availability=1.

Counters and KPIs


P_Blocking - KPI

Counters and KPIs

This manipulation is due to the fact that counter M1006C25_PAGING_TYPE_1_CN_ORIG does not distinguish between paging sent to a specific cell and paging sent to the whole LA/RA.

• The residual paging messages per cell exceeding the m.c.m. value given by M1006C25_PAGING_TYPE_1_CN_ORIGLA can be considered summing over the LA/RA:

• (M1006C25_PAGING_TYPE_1_CN_ORIG - M1006C25_PAGING_TYPE_1_CN_ORIGLA) contributes for all the cells belonging to LA/RA.


P_Blocking - KPITwo counters for overload

1. M1003C47_NBR OF DELETED PAGING MESSAGES DUE TO ICSU OVERLOAD and

2. M1003C48_NBR OF DELETED PAGING MESSAGES DUE TO RRMU OVERLOAD

are in related to

• M1003C36_REC_PAG_MSG to have detailed Iub and RC3 failure rate.

• The following KPIs for Iub and RC3 can be used to monitor overload condition:

• P_Block(Iub) = sum_cell_LA(M1003C47_NBR OF DELETED PAGING MESSAGES DUE TO ICSU OVERLOAD) / sum_CN_id(M1003C36_REC_PAG_MSG)

Counters and KPIs


P_Blocking - KPI

Counters and KPIs

P_Block(RC3) = sum_cell_LA(M1003C48_NBR OF DELETED PAGING MESSAGES DUE TO RRMU OVERLOAD) / sum_CN_id(M1003C36_REC_PAG_MSG)

The number of paging sent in the PCH is given by:

•N_paging = (PERIOD_MEAS in sec) * (M1000C70_AVE_PCH_THROUGHPUT / M1000C71_PCH_THROUGHPUT_DENOM_0) / 80bits.

where PERIOD_MEAS is the observation time in seconds

•This formula returns an extimated number of type1 messages on PCH channel.


P_Blocking - KPI

Counters and KPIs

• A comparison with the messages sent by RRC can be attempted as in the following:

• P_Block (MAC-c) = 1 - (N_paging)) / (M1006C25_PAGING_TYPE_1_CN_ORIG + M1006C26_PAGING_TYPE_1_RNC_ORIG)

• For this calculation it becames foundamental that the cells have PCH_availability=1 and cell_availability=1.

• It has to be considered that calculating the number of paging starting from Tput is an Approximation.

• The state transition between UTRAN, GMM and MM (idle, connected, detached) in the RRCConnection Setup procedure can add some residual innaccuracy


Paging and Call Setup - KPI

Counters and KPIs

Paging Type1 for MTC SR

• Two KPIs are possible to monitor the relationship between type1 paging forwarded and the successful MTC in the LA/RA

• Considering that the counter M1006C25_PAGING_TYPE_1_CN_ORIG does not distinguish between paging sent to a specific cell and paging sent to the whole LA/RA, some manipulation are required.

• Two formulas (valid at cell level) are possible using different counter families:

• Paging_SR=sum_cell(M1006C1-C3-C5-C7-C15-C16-

C17_RRC_Conn_Req_MTC_xxx_Call) / M1006C25_PAGING_TYPE_1_CN_ORIGLA


Paging and Call Setup - KPI

Counters and KPIs

Paging_SR=sum_cell(M1001C32-C34-C36-C38-C52-C56-

C60_MTC_xxx_Call_Attempts - M1001C578-C579-C580-C581-C590-C591-C592_RRC_Att_Rep_xxx) / M1006C25_PAGING_TYPE_1_CN_ORIGLA

- The simplified notation MTC_xxx stands for all the MTC available call type

- The notation M1006C25_PAGING_TYPE_1_CN_ORIGLA indicates the minimum of the counters M1006C25_PAGING_TYPE_1_CN_ORIG among all the cells of same LA/RA having PCH_availability=1 and cell_availability=1.


Improving MTC

Counters and KPIs

To improve the Paging Type1 for MTC SR KPI given by formula:

• Paging_SR=sum_cell(M1006C1-C3-C5-C7-C15-C16-

C17_RRC_Conn_Req_MTC_xxx_Call) / M1006C25_PAGING_TYPE_1_CN_ORIGLA

• The following procedures should be analyzed:

1) OLPC

2) Link Budget and possible unbalancing

3) Reselection Procedure

4) Paging repetition from CN

5) Coverage Analysis


Location area shared among different RNCs

Detailed investigation

The estimation of PAG_TYPE_1_ATT_CN_ORIGLA is more complex.

• to each CN paging type 2 (cases 3.1 and 4.1) in a cell of RNC 1 corresponds a CN paging type 1 (cases 3.2 and 4.2) in all the cells of LA in RNC2 (and vice versa);

• to each CN-CS paging type 1 (case 2.2) in a cell of RNC 1 corresponds a CN-CS paging type 1 (case 2.3) in all the cells of LA in RNC2 (and vice versa).


Location area shared among different RNCs


• PAGING_TYPE_1_CN_ORIGLA= Min(PAG_TYPE_1_ATT_CN_ORIGcell)

• where (cellAvailability=1 and pchAvailability= 1 and cellLA=LA and cellRNC=RNCx)] –X2–X34


Paging response counters


• The responses to paging messages can be counted considering RRC connection setups due to MTC and cell update related to paging messages.


Paging response counters


• The counters related to MTC are present both in RRC (updated for the Controlling RNC) and Service Level (updated in Serving RNC) tables.

• It’s more accurate to use the RRC counters when building paging success rate formulas: the paging counters come from RRC table as well.

• MTC counters include also repetitions of the RRC connection request.


Paging repetitions in RNC


• In case of cell_PCH activation, RNC shall repeat the paging for UE (in cell_PCHstate) not reached by the first paging procedure. The repetition is executed as defined by the following RNC parameters

• The RNC also accepts a cell update with a cause different than paging response as a valid paging response even if this response comes via a different cell than the UE originally was paged from.


Paging originated by CS-CN to Uein cell_PCH


• The RANAP paging from CS-CN is buffered, then the RNC originates paging attempts to bringthe UE in cell_FACH(Cell Update due to uplinkDataTransmission); the overall procedure includes also a paging at LA level.

The overall procedure:

• 5 repetitions in the cell

• 1 repetition at LA level.

The incremented counter is PAG_TYPE_1_ATT_CN_ORIG


Paging originated by RNC due to DL PDU from SGSN


• The RANAP paging from CS-CN is buffered, then the RNC originates paging attempts to bring UE in cell_FACH (Cell Update due to uplink DataTransmission)

• The overall procedure includes also a paging at LA level.

• The overall procedure:

• 11 repetitions in the cell

• 3 repetition at RNC

level.

The incremented counter is PAG_TYPE_1_ATT_RNC_ORIG


Paging success rate at LA level, cell_PCH not active


KPI for the calculation of the percentage of not reachable UE should take into account the repetition of the paging in the CN. This KPI is not consistent with theuser perception.

It’s based on the hypothesis that the paging is not sent to more than 1 LA at the same time: in this case the paging can be successful in one LA only.


Paging success rate at LA level, cell_PCH active



Paging success rate at LA level, cell_PCH active


Apparent degradation after activation of cell_PCH: it’s due to low response rate to RNC pagings.

Possible reasons:• Too short repetition time of RNC paging attempts

• Underestimation of the number of cell update due to paging response (the cell update could be attributed to other causes, then not counted)


Paging success rate at cell level


• The overestimation of PAG_TYPE_1_ATT_RNC_ORIGRNC determines an underestimation of PAG_TYPE_1_ATT_RNC_ORIG cell=>paging_SR is overestimated.

• PAG_TYPE_1_ATT_CN_ORIGcell is not included in the formula because the CN-CS paging attempts to UEs in cell_PCH don’t increment any paging response counter (cell update due to uplink Data Transmission).


PCH throughput: paging requests blocked


The number of transmitted paging (on the radio interface) is:

Paging_requests[pagings/hour] = 3600 * PCH_THROUGHPUT / (80 bits)

The number of paging attempts forwarded to be transmitted on PCH is:

Paging_type_1 [pagings/hour] = PAG_TYPE_1_ATT_CN_ORIG + PAG_TYPE_1_ATT_RNC_ORIG

The number of paging attempts not sent on air due to congestion of PCH channel is:

Paging_requests_blocked[paging/hour] = paging_type_1 -paging_requests


PCH throughput: paging requests blocked


• The PCH blocking is calculated around 0.2% for a PCH throughput of 60000 paging sent / hour / cell.

A formula for the estimation of the PCH blocking is proposed, as a function of:

• the PCH throughput

• the paging buffering in RNC.


Observations about RNC counters


• RNC counters PAG_TYPE_1_ATT_CN_ORIG and PAG_TYPE_1_ATT_RNC_ORIG don’t distinguish paging attempts issued at cell, LA and RNC level.

• Pre-processing of these counters is required to implement success rate formulas;

• When CELL_PCH is active, paging repetitions in RNC increment PAG_TYPE_1_ATT_CN_ORIG and PAG_TYPE_1_ATT_RNC_ORIG, resulting in an underestimation of the paging success rate

• When a UE in Cell_PCH is paged by MSC, the RANAP paging attempt is buffered and sent later (type 2 paging), when the UE has already answered to a type 1 paging .


Observations about RNC counters


• In this case two paging counters are incremented: PAG_TYPE_1_ATT_CN_ORIG and PAG_TYPE_2_ATT

• LA sharing among different RNCs originates a surplus of paging attempts. It reduces the advantages of Cell_PCH activation

• The out of coverage probability can be estimated combining MSC and RNC counters

• The PCH blocking can be calculated at cell level using the appropriate RNC counters

• Formula is proposed for the estimation of the PCH blocking probability as function of the PCH throughput.

3g counters and kpis for paging

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