KPIs Orientation

SDCCH Blocking RateTCH Blocking RateHandover Success RateCall Setup Success RateDrop Call Rate

SDCCH Blocking Rate (Siemens)This indicator will give you the SDCCH Traffic Loss Rate by meaning the rate where new SDCCH Seizure Attempts could not be handled, because all SDCCH were occupied / blockedNATTSDPE: Number of Attempted SDCCH Seizures in a PeriodTrigger events

Receipt of a valid CHANNEL REQUIRED (BTS --> BSC) (immediate assignment procedure, SDCCH assignment request only)Receipt of a valid ASSIGNMENT REQUEST (MSC --> BSC) (assignment procedure, SDCCH assignment request only)

Receipt of an INTERCELL HANDOVER CONDITION INDICATION (BTS --> BSC) during the SDCCH phase (SDCCH-SDCCH handover, intra-BSC)Receipt of a HANDOVER REQUEST (MSC --> BSC) containing the channel type SDCCH (incoming SDCCH-SDCCH handover, Inter-BSC)ATSDCMBS: Attempted SDCCH Seizures Meeting an SDCCH Blocked State

Factors Affecting SDCCH Blocking RateIncrease in Location Updates LAC Boundary Cells Wrong Timer Settings in Core/BSS

Increase in Supplementary ServicesIncrease in MOC/MTC Core Network Overload cause high number of reattemptsAbis on SatelliteFaulty TRXsDimensioningTolerable Values: 0.1 to 0.5 %Max SDCCHs per TRX: 2 in Nokia & 4 in SiemensDynamic Channel Configuration

(tch_call_req -tch_norm_seiz) (msc_o_sdcch_tch + bsc_o_sdcch_tch + cell_sdcch_tch); DR calls+ tch_succ_seiz_for_dir_acc)- (tch_rej_due_req_ch_a_if_crc ; Aif type mismatch or congestion-(bsc_i_unsucc_a_int_circ_type ; Aif circuit pool handover failures+ msc_controlled_in_ho+ ho_unsucc_a_int_circ_type))--------------------------------------------------------------------------(tch_call_req)-(tch_rej_due_req_ch_a_if_crc ; Aif type mismatch or congestion-(bsc_i_unsucc_a_int_circ_type ; Aif circuit pool handover failures+ msc_controlled_in_ho+ ho_unsucc_a_int_circ_type))TCH Blocking Rate (Nokia)

TCH Call Request is number of TCH requests for a normal assignment (both successful and unsuccessful). Its updated When the RRM receives a TCH request in a call attempt

TCH Norm Seiz is number of successful TCH requests for a normal assignment. Its updated when the Radio Resource Manager allocates a TCH as a response to a TCH request in a call attempt

Compensation Factor . msc_o_sdcch_tch: MSC Controlled Successful Outgoing Directed Retries bsc_o_sdcch_tch: BSC Controlled Successful Outgoing Directed Retriescell_sdcch_tch: Internal Directed Retries when Super Reuse TRX/Intelligent Underlay Overlay feature is deployed

tch_succ_seiz_for_dir_acc: Number of successful TCH seizures in direct accesses toa super-reuse TRX during the call set-up phase tch_rej_due_req_ch_a_if_crc: Number of rejected TCH requests due to mismatch between the requested channel type and the A-interface circuit type, whether queuing occurred or not

bsc_i_unsucc_a_int_circ_type: Counter is incremented when the internal inter-cell handover attempt has been interrupted because BSC wishes to change the A-interface circuit pool before TCH allocationho_unsucc_a_int_circ_type:Counter is incremented when the internal intra-cell handover attempt has been interrupted because BSC wishes to change the A-interface circuit pool before TCH allocation msc_controlled_in_ho: Counter is incremented when the handover attempt has been failed due to unsuccessful TCH allocation attempt because of the mismatch between the requested TCH channel type and A-interface circuit type. The cause Switch circuit pool will be sent in the HANDOVER FAILURE message to the A-interface

Factors Affecting TCH Blocking RateHigh TrafficFaulty TRXsFluctuations Neighboring sites downBig Coverage Area Sites1800 Propagation Losses causing underutilized 1800 band in coverage sitesImbalance Traffic Distribution between 900/1800DimensioningTolerable value: 2%Half Rate (Trade Off between Quality & Capacity)Traffic Balancing between 900 & 1800 layers

There are three main types of HandoversIntra Cell Handover:An intra-cell handover occurs when an MS is transferred from one channel to another within a cell. This usually includes Full Rate-Half Rate & Half Rate-Full Rate Handovers.BSC Controlled Handover:This type of handover involves an MS being transferred from one cell to another, when both cells are being controlled by the same BSC. This type of handover is generally controlled by the BSC. This can be both incoming & outgoingMSC Controlled Handover:This type of handover involves an MS being transferred from one cell to another, when the target cell is controlled by a different BSC to that of the source cell. This type of handover is always controlled by the MSC. This can be both incoming & outgoingHandover Success Rate (Nokia)

Mentioned below is Nokias HOSR Formula:

Successful HOs HOSR = ---------------------------- HO Attempts MSC Controlled Successful HOs + BSC Controlled Successful HOs + Intra Cell Successful HOsHOSR = ------------------------------------------------------------------------------------- MSC Controlled HO Attempts+ BSC Controlled HO attempts + Intra Cell HO Attempts

HO are of three types in all the above categories

tch_tch_at = handover attempt from one TCH to another TCH (Normal HO)sdcch_tch_at= handover attempt from TCH to SDCCH (Directed Retry HO)sdcch_sdcch_at= handover attempt from one SDCCH to another SDCCH (Disabled in Our Network)

Factors Affecting Handover Success RateThings that affect HOSR are:

TCH Blocking:TCH blocking can be the major reason for low HOSR. It usually affect Incoming (BSC & MSC Controlled) & intra Cell Hanover. When a MS comes from a source cell to a destination cell and there are no resources available in destination cell (No free TCHs) handover is failed. Same is the case with Intra Cell HO. In case MS is trying to Handover From Half Rate to Full Rate & there are no resources available

Handover Drops:Handover drops represent the category of failed handover when MS is in the process of Hanover and the call is dropped. Cause of Handover drops can be the same as normal TCH Drops (RF Failures, Abis Failures, Transcoder Failures & A-If Failures etc.)Neighbor & LAC Definitions:Improper neighbor and LAC definition can be another reason for handover failures. In case of MSC Controlled handover the LACs of MSC boundary Cells should be defined as external LACs in the neighboring MSCs.

Wrong BCCH/BSIC Plan:This is the most common and basic reason for handover failures

Weak Neighbors:Handover attempts on weak neighbors also cause low HOSR due to high chances of failures. Parameter Optimization carried out in such scenarios

Call Setup Success Rate (Siemens)

Factor-1: ImmAssSuccRate Factor-2: ImmAssAGCHSuccRateFactor-3:ImmAssSeizRate Factor-4: AssSuccRateFactor-5: SDCCHSuccRate

Factor-1: Immediate Assignment Success Rate

Factors Affecting Immediate Assignment Success RateSDCCH BlockingTCH Blocking in case of Direct AssignmentBTS Channel Activation Failures

Phantom RACHs: These are channel required messages not foreseen for the observed cell. The Immediate Assignment procedure to allocate an SDCCH/TCH is then started, but will not be successful, because no MS will reply with a SABM message and therefore a BTS Timer will expire. These unforeseen messages will also be counted.

The RACH attempt for Immediate Assignment has to be evaluated by the procedures as below: RSSI SOVA( BSS Soft Decision Criterion ) SNR Convolution Code Training sequence Additional criteria to discard Phantom RACH CRC check Received signal level ( Discard the RACH that the signal level < RACHBT) MS - BTS distance check

Increase the RACHBT will cause more weak RACH to be discarded. This will cause the increase of NINVRACH sub counter 1.

Factor-2: Immediate Assignment AGCH Success RateNACSUCPR: Number of Accesses with a Successful Result by Procedure (AGCH)The successful accesses to the AGCH are determined by taking the difference between the number of transmitted IMMEDIATE ASSIGNMENT command messages(BSC --> BTS) and the number of received DELETE INDICATION messages (BTS --> BSC)These indicators will give you the number AGCH losses by meaning of not transmitted Immediate Assignment Command messages over the AGCH on the Air Interface. Reason for AGCH failures are mainly AGCH overload. This formula is related to MS point of view, by meaning each MS related immediate assignment procedure should be stepped once.Factors Affecting Immediate Assignment AGCH Success Rate

Factor-3: Immediate Assignment Seizure RateFactors Affecting Immediate Assignment Seizure RatePhantom RACHsL2 SABM not received due to Air Interface Problems

Factor-4: Assignment Success RateTASSSUCC: Total Number of Successful Assignments(FR/HR)

SINTHINT: Successful Outgoing Internal Inter Cell-DR

SUINBHDO: Successful Outgoing Inter-BSC DR

TASSATT: Total Number of Assignment Attempts (FR/HR)Factors Affecting Assignment Success RateNo Radio Resource Available (TCH Blocking)Unsuccessful Directed RetriesRadio Interface Message FailuresOther CausesSub Counters for Assignment Failures are

NRFLSDCC: Number of Lost Radio Links while using an SDCCHFactor-5: SDCCH Success Rate

Drops after TCH assignment TCH Re-AssignmentsDCR=--------------------------------------------------------------------- %TCH assignments for new callsDrop Call Rate Rate (Nokia)Note:

Calls that are dropped during Handover on the old (source) channel are also pegged as dropped calls in source cell

This formula includes the drops that occur between ASSIGNMENT_COMPLETE and DISCONNECT commands

We are not using the Re-Assignments feature in our network.

TCH Drop Call Rate basically represents any call which is dropped possibly due to any failure. The main reasons for these failures can be

Radio FailuresAbis FailuresTranscoder FailuresA-Interface FailuresRadio FailuresMain Reason for Radio Failures are low RX Quality (Uplink/downlink), low RX level (Uplink/downlink), Interference (Uplink/downlink), Distance (High Timing Advance). Any malfunctioning RF Hardware (TRXs, Combiners etc) will also cause increase in Radio Failure

ABIS Failure:

Number of TCH transaction failures due to an Abis interface failure during normal call & during Handover on old channelThe failure reasons may include missing acknowledgement of channel activation, missing indication of call establishment, receipt of an error indication, corrupted messages, missing measurement results from the BTS, excessive timing advance or some internal reasons. The fluctuations of Abis links (between BSC & BTS) can also be the main reason for these failures.

Transcoder Failure:

Number of radio TCH transactions ended due to a transcoder failure during normal call & during Handover on old channel. This counter is updated when conn_fail_rem_trans_fail_c is updated which is when CONNECTION FAILURE message is received and its cause is remote transcoder failure. The main reason for these drops can be the fluctuation of Aters (Between BSC & Transcoder).

A-Interface Failure:

Number of TCH transaction failures due to an A interface failure normal call & during Handover on old channel. The main reason for these failures are related to MSC which may include SCCP connection establishment failure, erroneous & invalid BSSMAP messages, unsupported speech coder version & TCH type, fault in the 2-Mbit PCM connection etc.

TCH Failures Other Reasons:

BTS Failures (When a TCH transaction ends because of a TRX blocked by a BTS)BCSU resets (When a TCH transaction ends because of a TRX blocked by a BCSU restart)LAPD Failures (When a TCH transaction ends because of a TRX blocked by an LAPD failureFailure due to user Actions (When the user disconnects a busy TCH by blocking the TSL/TRX with an MML command)