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BSC3120 Nokia GSM/EDGE BSS, Rel. BSS12, System Documentation, v.1

GSM Voice Key Performance Indicators

Nokia Proprietary and Confidential

BSS12 GSM Voice Key Performance Indicators

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Contents

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Contents

1 About this document .............................................................................5

2 GSM voice KPI categories.....................................................................6

3 GSM voice KPI definitions and formulas .............................................8 3.1 Accessibility..............................................................................................8 3.1.1 TCH call blocking, DR compensated (blck_8i) .........................................8 3.1.2 SDCCH access probability, (gsm voicef_1) .............................................8 3.1.3 HO failure % due to radio interface blocking, (hfr_55a) ...........................9 3.2 Retainability............................................................................................10 3.2.1 SDCCH drop ratio without timer T3101 expiry %, (sdr_4)......................10 3.2.2 TCH dropped conversation %, area, (dcr_5a)........................................11 3.2.3 TCH dropped conversation %, area, re-est. considered,

(dcr_5b)..................................................................................................11 3.2.4 Total HO failure %, (hfr_2a) ...................................................................12 3.2.5 HO drop ratio, (hfr_68a) .........................................................................13 3.3 Quality ....................................................................................................14 3.3.1 UL cumulative quality % in class X, S1 (ulq_2a) ....................................14 3.3.2 DL cumulative quality % in class X, S1 (dlq_2a) ....................................15 3.4 Traffic share ...........................................................................................16 3.4.1 TCH traffic sum (trf_1d)..........................................................................16 3.4.2 Average SDCCH traffic (trf_11b)............................................................16 3.4.3 DTM CS traffic ratio (dtm_2) ..................................................................17 3.4.4 TCH traffic share of non-AMR calls (trf_120a) .......................................18 3.4.5 TCH traffic share of FR AMR calls (trf_121)...........................................19 3.4.6 TCH traffic share of HR AMR calls (trf_122a) ........................................20

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About this document

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1 About this document This document defines Nokia recommendations for the GSM voice Key Performance Indicators (KPIs).

These definitions are subject to change. Nokia improves the definitions and the list of KPIs according to received feedback and results from testing and field operations.

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2 GSM voice KPI categories GSM voice KPIs are divided into the following categories:

• Accessibility – establishing a successful connection

• Retainability – maintaining an ongoing connection

• Quality – having a good service experience during a connection

• Traffic Share – finding out the traffic share between different services

Table GSM voice KPIs lists the GSM voice KPIs and formula IDs by category. Table 1. GSM voice KPIs

KPI Category Description Formula ID Accessibility TCH call blocking, DR compensated blck_8i SDCCH access probability gsm voicef_1

HO failure % due to radio interface blocking hfr_55a

Retainability

SDCCH drop ratio without timer T3101 expiry % sdr_4

TCH dropped conversation %, area dcr_5

TCH dropped conversation %, area, re-est. considered dcr_5b

Total HO failure % hfr_2a HO drop ratio hfr_68a Quality UL cumulative quality % in class X, S1 ulq_2a, x=5 DL cumulative quality % in class X, S1 dlq_2a, x=5 Traffic Share TCH Traffic Sum trf_1d Average SDCCH traffic trf_11b DTM CS traffic ratio dtm_2 TCH traffic share of non-AMR calls % trf_120a

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TCH traffic share of FR AMR calls % trf_121 TCH traffic share of HR AMR calls % trf_122a

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3 GSM voice KPI definitions and formulas

This chapter includes definitions and formulas for the GSM voice KPIs. The KPIs are listed by category. For an overview of the categories, see chapter GSM voice KPI categories.

3.1 Accessibility

With the following KPIs , accessibility is examined from the point of view of traffic channel, SDCCH and handover.

3.1.1 TCH call blocking, DR compensated (blck_8i)

Description: This KPI measures the traffic channel congestion.

Use:

This KPI is applicable on the BTS level even when the BTS is part of a multi-BTS segment. Note that this version can only be used in S11 with BSC CD 7.2, and in S11.5 with BSC CD 4.0.

Formula (NetAct names): sum(TCH_REQUESTS_CALL_ATTEMPT

- SUCC_TCH_SEIZ_CALL_ATTEMPT) 100 * -----------------------------------

sum(TCH_REQUESTS_CALL_ATTEMPT)

Counters from table(s): p_nbsc_traffic

3.1.2 SDCCH access probability, (gsm voicef_1)

Description:

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This KPI measures SDCCH congestion.

Use: This KPI gives the probability to access SDCCH without the effect of FGSM VOICE. It is used on the area and BTS level. All types of SDCCH allacation are included (Call Setup, SMS, LU, etc.). This KPI can be used for the dimensioning of static SDCCH or probable activation of dynamic SDCCH allocation.

Formula:

sum(sdcch_busy_att) 100 * (1 - -----------------------------) %

sum(sdcch_seiz_att)

Counters from table(s): p_nbsc_traffic

3.1.3 HO failure % due to radio interface blocking, (hfr_55a)

Description: This KPI can be used for the dimensioning of clusters to provide need capacity for MS mobility. Handover failure in Nokia BSS can occur without the actual HO command. (e.g. there is a reason for a HO, but the target cell is full).

Use: This KPI is used on the area level.

Formula:

sum(msc_o_fail_lack /* handovers failing due to blocking */

+bsc_o_fail_lack +cell_fail_lack)

100 * -------------------------------------- % sum(msc_o_ho_cmd /* all HO attempts */

+ bsc_o_ho_cmd_assgn

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+ bts_ho_assgn)

Counters from table(s): p_nbsc_ho

3.2 Retainability

With the following KPIs, retainability is examined from the point of view of traffic channel, SDCCH, and handover.

3.2.1 SDCCH drop ratio without timer T3101 expiry %, (sdr_4)

Description:

This KPI defines the ratio of dropped SDCCH without considering the drops caused by timer T3101. It is used to analyse SDCCH drops and reasons in case of Call Setup, SMS, LU, etc. Call Setup failure is mostly visible to end (MS) users. Use: This KPI is used to follow up the performance of SDCCH from a technical point of view.

Formula:

sum(a.sdcch_radio_fail

+ a.sdcch_rf_old_ho + a.sdcch_user_act + a.sdcch_bcsu_reset + a.sdcch_netw_act + a.sdcch_abis_fail_call + a.sdcch_abis_fail_old + a.sdcch_bts_fail + a.sdcch_lapd_fail + a.sdcch_a_if_fail_call + a.sdcch_a_if_fail_old - b. T3101_EXPIRED)

100 * --------------------------------------- %

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sum(sdcch_assign+sdcch_ho_seiz)

a = p_nbsc_traffic b = p_nbsc_service

Counters from table(s): p_nbsc_traffic p_nbsc_service

3.2.2 TCH dropped conversation %, area, (dcr_5a)

Description: This KPI defines the ratio of calls dropped while A and B are talking, that is after conn_ack. Inter-BSC handovers are subtracted in the denominator because they trigger conver_started. Compensation is 100% true only if the area has no inter-BSC HOs from outside the area. Use:

This KPI is used on the area level.

Formula: sum(b.dropped_calls)

100 * ------------------------------ % sum(b.conver_started) - sum(a.msc_i_tch_tch)

Counters from table(s): a = p_nbsc_ho b = p_nbsc_service

3.2.3 TCH dropped conversation %, area, re-est. considered, (dcr_5b)

Description: This KPI defines the ratio of calls dropped while A and B are talking, that is after conn_ack. Inter-BSC handovers are subtracted in the

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denominator because they trigger conver_started. Compensation is 100% true only if the area has no inter-BSC HOs from outside the area. Use:

This KPI is used on the area level.

Formula:

sum(b.dropped_calls) - sum(tch_re_est_release)

100 * ----------------------------------------- % sum(b.conver_started) - sum(a.msc_i_tch_tch)

Counters from table(s): a = p_nbsc_ho b = p_nbsc_service

3.2.4 Total HO failure %, (hfr_2a)

Description: This KPI can be used for dimensioning clusters to provide need capacity for MS mobility. HO failure in Nokia BSS can occur without the actual HO command. (e.g. there is reason for a HO, but the target cell is full.) This KPI includes both failed HOs where the HO command is sent and those where the HO command is not sent to the MS. HO failures are not visible to end (MS) users.

Use:

This KPI is used on the area or network level.

Formula (logical): HO attempts - successful HOs

100 * --------------------------------- % =

HO attempts

successful HOs

100 * (1- ----------------------------------) % =

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HO attempts

Formula (NetAct Names): sum(msc_o_succ_ho

+ bsc_o_succ_ho

+ cell_succ_ho)

100 * (1- ---------------------------------- )%

sum(msc_o_ho_cmd

+ bsc_o_ho_cmd_assgn

+ bts_ho_assgn)

Counters from table(s):

p_nbsc_ho

3.2.5 HO drop ratio, (hfr_68a)

Description: This KPI defines how big a share of the started handovers are dropped. It indicates the quality of the handovers. HO drops are visible as dropped calls to end (MS) users.

Use: This KPI is used in optimization of HO quality. Formula: Sum(bsc_o_drop_calls /* all HO attempts */ + msc_o_call_drop_ho + cell_drop_calls)

100* ------------------------------------------- % sum(msc_o_ho_cmd /* handovers failing due to blocking */ + bsc_o_ho_cmd_assgn + bts_ho_assgn)

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-sum(msc_o_fail_lack /* handovers failing due to not allowed */ + bsc_o_fail_lack + cell_fail_lack) -sum(msc_o_not_allwd /* wrong Aif circuit type */ + bsc_o_not_allwd + cell_not_allwd) -sum(bsc_o_unsucc_a_int_circ_type + msc_controlled_out_ho + ho_unsucc_a_int_circ_type ) Counters from table(s): p_nbsc_ho

3.3 Quality

Quality of Voice can be examined by two counters. The first counter measures uplink quality and the second counter measures downlink quality.

3.3.1 UL cumulative quality % in class X, S1 (ulq_2a)

Description: This KPI gives the cumulative percentage of call samples in classes 0 to X.X = 5 and is normally used as a quality indicator. If X = 5 and this figure is 100 %, the MS users have not perceived any quality problems in case of EFR codec.

Use: This KPI is used to estimate actual voice quality perceived by end (MS) users. Actual values are not comparable between different codec versions (e.g. AMR and non-AMR). Formula: sum(freq_ul_qual0 + ... + freq_ul_qualX)

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100 * ----------------------------- % sum( freq_ul_qual0 + ... + freq_ul_qual7 ) Counters from table(s): p_nbsc_rx_statistics

3.3.2 DL cumulative quality % in class X, S1 (dlq_2a)

Description: This KPI gives a cumulative percentage of call samples in classes 0 to X. X = 5 and is normally used as a quality indicator. If X = 5 and this figure is 100 %, the MS users have not perceived any quality problems in case of EFR codec.

Use: This KPI is used to estimate actual voice quality perceived by end (MS) user. Actual values are not comparable between different codec versions (e.g. AMR and non-AMR). Formula: sum(freq_dl_qual0 + ... + freq_dl_qualX)

100 * ------------------------------ % sum(freq_dl_qual0 + ... + freq_dl_qual7)

Counters from table(s): p_nbsc_rx_statistics

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3.4 Traffic share

The purpose of the following KPIs is to examine the traffic share of different features in the network. The traffic share KPIs are used for measuring total traffic and SDDCH traffic, examining DTM traffic and measuring AMR traffic share.

3.4.1 TCH traffic sum (trf_1d)

Use:

This KPI is used on the BTS and area level. Formula (NetAct names): sum((0.5*a.DTM_duration_sum_HR +

a.DTM_duration_sum_FR) /100) ------------------------------------------ sum (period_duration*60) + sum(b.ave_busy_tch) ------------------------------------------ sum(b.res_av_denom14)

Counters from table(s): a = p_nbsc_ps_dtm b = p_nbsc_res_avail

3.4.2 Average SDCCH traffic (trf_11b)

Use: This KPI is used on the BTS level. For area (or segment) level, first use the formula for all the BTSs and then sum this formula over all underlying BTSs. Formula (NetAct names):

sum(ave_busy_sdcch)

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------------------------------- sum(res_av_denom15) Counters from table(s): p_nbsc_res_avail

3.4.3 DTM CS traffic ratio (dtm_2)

Description: DTM is a new S12 application software that allows simultaneous CS and PS use. This KPI defines the ratio of DTM CS traffic (in Erlang) to all CS traffic. Formula notes:

1) Unit of DTM_duration_sum_HR and DTM_duration_sum_FR is 10ms (devided by 100 in the formula)

2) S12 does not support DTM CS HR connections (hence the counter will always be zero).

3) BSC has two counters (c2046 as numerator, c2047 as denominator) for busy full rate TCH and two counters (c2048 as numerator, c2049 as denominator) for busy half rate TCH. NetAct stores the division results as counter c2046 (ave_tch_busy_full) and c2048 (ave_tch_busy_half). Therfore counters c2047 and c2049 are redundant and not visible in NetAct.

Formula: DTM CS Erlangs/(DTM CS Erlangs + non-DTM CS Erlangs) sum((0.5*a.DTM_duration_sum_HR +

a.DTM_duration_sum_FR) / 100) / (period_duration*60) 100 * ---------------------------------------- sum((0.5*a.DTM_duration_sum_HR + a.DTM_duration_sum_FR) / 100) / (period_duration*60)) + sum(period_duration

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* (0.5 * b.ave_tch_busy_half + b.ave_tch_busy_full) / 60))

Counters from table(s): p_nbsc_ps_dtm p_nbsc_res_avail

3.4.4 TCH traffic share of non-AMR calls (trf_120a)

Description: This KPI indicates TCH use % (sampling interval 480 ms) for non-AMR calls.

Formula: 100*trf_115a/ trf_119

Trf_115a formula: sum(nvl(FREQ_UL_QUAL0,0)+ + nvl(FREQ_UL_QUAL7,0)

-sum(nvl(AMR_FR_MODE_1_UL_RXQUAL_0,0)+..+ nvl(AMR_FR_MODE_1_UL_RXQUAL_7,0)

+nvl(AMR_FR_MODE_2_UL_RXQUAL_0,0)+..+ nvl(AMR_FR_MODE_2_UL_RXQUAL_7,0)

+nvl(AMR_FR_MODE_3_UL_RXQUAL_0,0)+..+ nvl(AMR_FR_MODE_3_UL_RXQUAL_7,0)

+nvl(AMR_FR_MODE_4_UL_RXQUAL_0,0)+..+ nvl(AMR_FR_MODE_4_UL_RXQUAL_7,0)

+nvl(AMR_HR_MODE_1_UL_RXQUAL_0,0)+..+ nvl(AMR_HR_MODE_1_UL_RXQUAL_7,0)

+nvl(AMR_HR_MODE_2_UL_RXQUAL_0,0)+..+ nvl(AMR_HR_MODE_2_UL_RXQUAL_7,0)

+nvl(AMR_HR_MODE_3_UL_RXQUAL_0,0)+..+ nvl(AMR_HR_MODE_3_UL_RXQUAL_7,0)

+nvl(AMR_HR_MODE_4_UL_RXQUAL_0,0)+..+ nvl(AMR_HR_MODE_4_UL_RXQUAL_7,0)

)*0,48/3600

Trf_119 formula:

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sum(nvl(FREQ_UL_QUAL0,0) + ..+ nvl(FREQ_UL_QUAL7,0))*0,48/3600

Counters from table(s): p_nbsc_rx_qual p_nbsc_rx_statistics

3.4.5 TCH traffic share of FR AMR calls (trf_121)

Description: This KPI indicates TCH use % (sampling interval 480 ms) for full rate AMR.

Formula: 100*trf_117/ trf_119

Trf_117 formula: sum(

nvl(AMR_FR_MODE_1_UL_RXQUAL_0,0)+..+ nvl(AMR_FR_MODE_1_UL_RXQUAL_7,0)

+nvl(AMR_FR_MODE_2_UL_RXQUAL_0,0)+..+ nvl(AMR_FR_MODE_2_UL_RXQUAL_7,0)

+nvl(AMR_FR_MODE_3_UL_RXQUAL_0,0)+..+ nvl(AMR_FR_MODE_3_UL_RXQUAL_7,0)

+nvl(AMR_FR_MODE_4_UL_RXQUAL_0,0)+..+ nvl(AMR_FR_MODE_4_UL_RXQUAL_7,0)

) *0,48/3600

Trf_119 formula: sum(nvl(FREQ_UL_QUAL0,0) + ..+

nvl(FREQ_UL_QUAL7,0))*0,48/3600

Counters from table(s): p_nbsc_rx_qual p_nbsc_rx_statistics

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3.4.6 TCH traffic share of HR AMR calls (trf_122a)

Description: This KPI indicates TCH use % (sampling interval 480 ms) for half rate AMR.

Formula: 100*trf_118a/ trf_119

Trf_118a formula: sum(

nvl(AMR_HR_MODE_1_UL_RXQUAL_0,0)+..+ nvl(AMR_HR_MODE_1_UL_RXQUAL_7,0)

+nvl(AMR_HR_MODE_2_UL_RXQUAL_0,0)+..+ nvl(AMR_HR_MODE_2_UL_RXQUAL_7,0)

+nvl(AMR_HR_MODE_3_UL_RXQUAL_0,0)+..+ nvl(AMR_HR_MODE_3_UL_RXQUAL_7,0)

+nvl(AMR_HR_MODE_4_UL_RXQUAL_0,0)+..+ nvl(AMR_HR_MODE_4_UL_RXQUAL_7,0)

) *0,48/3600

Trf_119 formula: sum(nvl(FREQ_UL_QUAL0,0) + ..+

nvl(FREQ_UL_QUAL7,0))*0,48/3600

Counters from table(s): p_nbsc_rx_qual p_nbsc_rx_statistics