UTRAN KPI Analysis Guide

Overview

In a commercial network, the QoS and network operation are reflected through KPI. UTRAN KPI analysis is a major method used for monitoring and evaluating network operation. UTRAN KPI analysis is also served to track the network traffic, monitor the resource distribution, and facilitate the network expansion and optimization. Huawei UTRAN traffic statistics provides sufficient KPI for network operation, algorithm management, and resource distribution. These traffic statistics can be used to locate network problems and optimize network KPI.

Call Completion Rate This consists of the following parts:

RRC Setup Analysis

RAB Setup Analysis

RRC Setup Analysis There are two reasons for RRC Setup Fail No Response:

Downlink FACH and RACH are covered unevenly.

The networks, built during the early period, are covered poorly. In particular, inter-system reselection areas are covered poorly.

A certain area has too many subscribers or any equipment in this area is faulty.

RRC Setup Scenario Analysis

One of the reasons for RRC Setup Fail No Response is poor coverage

Most RRC setup requests are caused by:

RRC REQ CELL RESEL

If network coverage is poor, inter-system reselection may occur.

RRC REQ REG

If network coverage is poor, subscribers attempt to register for many times.

Low RRC SETUP SUCC RATE REG indicates that many registrations are attempted within the area (Ec/Io falls between -14 dB and -18 dB), which has poor coverage. High RRC SETUP SUCC RATE ORG (99%) indicates that the network is covered by PCH and RRC SETUP SUCC RATE can be high in a well-covered network.RRC Setup Reject Analysis

RRC setup reject are caused by:

Admission reject due to crowded subscribers

Access failure due to equipment faults

RRC setup reject may be caused by the following reasons:

(1) Power Congestion

RRM performs the admission algorithm decision but uplink or downlink admission decision is rejected, so RRC setup reject occurs. If network load is heavy, power congestion may occur.

(2) CE Congestion If there are many subscribers, CE resources may become insufficient in RNC.

(3) RL Fail During the RRC setup process, NodeB recognizes RRC setup fail because NodeB fails or NodeB resource is insufficient.

(4) AAL2 Fail If transmission resource is insufficient or any transmission equipment is faulty, the AAL2 path setup of lub interface may fail .(5) FP Fail If the transmission fails or an equipment is faulty, FP synchronization may fail.

(6) Code Congestion If there is high traffic in the indoor micro cell, code resource may be

insufficient. To locate the problem, start Cell OVSF Code Allocation Analysis to analyze the code allocation and confirm major services.

RAB Setup Analysis Low RAB setup success rate may occur in the cells that have lowest setup times. To locate the problem, focus on the cells that have the lowest setup failures because the KPI is affected mostly by these cells.

Cell CS RAB setup failures may be caused by the following reasons:

(1) RNC regards the parameters transmitted by core network as invalid parameters. This reason seldom occurs. To locate the problem, track the signaling and check the RAB setup messages in specific cells.

(2) When initializing the migration process, RNC receives the RAB setup request messages but RNC does not process the request

(3) TNL_CELL RAB setup fails because IU transmission setup fails.

(4) CONG_CELL This may be caused by RNC resource allocation failure. To

locate the problem, analyze the RNC logs and obtain the detailed resource

failure information.

(5) According to RRM admission decision, new RAN cannot be set up because cell load is too heavy.

(6) CE_CONG_CELL CE resource admission fails in RNC. CE must be

expanded.

In a commercial network, RAB setup failure is mainly caused by admission failure and RB setup failure.

Cell RB setup failure may be caused by the following reasons:

(1) UE acknowledges the RB setup failure because of configuration unsupported. This reason seldom occurs in the network. It is mainly caused by compatibility problem of UE in some unknown scenarios.

(2) PHYCH_FAIL The RB setup failure may occur if FACH is migrated to DCH

but downlink physical layers are not synchronized during the RB setup

process.(3) SIMU_RECFG_INCOMP UE regards that the RB setup process and other processes simultaneously occur and they are incompatible. RNC processing ensures RRC processes nesting. This reason seldom occurs. It is mainly caused by UE defects.

(4) CELL_UPDT During the RB setup process, the Cell Update process occurs. The RB setup failure is caused by process nesting.

(5) CFG_INVALID

UE regards the configured parameters are invalid ones. This reason seldom occurs. It is mainly caused by inconsistent understanding of network and UE.

(6) NO_RESPONSE

UE does not acknowledge the RB setup request. This reason frequently occurs. It is mainly caused by poor coverage, so UE cannot receive the RB setup request message.

Soft Handover Analysis Soft handover failure may be caused by the following reasons:

(1) SHO_RL_ADD_FAIL_CFG_UNSUPP

UE does not support to add radio links in RNC during the active set update. This reason seldom exists in a commercial network.

(2) SHO_RL_ADD_FAIL_SIMU_RECFG_INCOMP

UE feeds back that the soft handover process is incompatible with other concurrent processes when radio links are added in RNC. When handling the processes, RNC performs the serial connection. The problem is mainly caused by some handsets.

(3) SHO_RL_ADD_FAIL_CFG_INVALID

UE regards active set update of adding radio links in RNC as invalid configuration. This reason seldom occurs in a commercial network. (4) SHO_RL_ADD_FAIL_NO_RSP RNC does not receive the acknowledgement of

active set update of adding radio links. Soft handover failure is mainly caused

by this reason. If network coverage is poor or soft handover area is small, soft

handover failure easily occurs. Thus, the RF optimization is required.

(5) SHO_RL_DEL_FAIL_CFG_UNSUPP

UE does not support to delete radio links in RNC during the active set update. This reason seldom occurs in a commercial network.

(6) SHO_RL_ADD_FAIL_SIMU_RECFG_INCOMP UE feeds back that the soft

handover is incompatible with other concurrent processes when radio links are

deleted in RNC. When handling the processes, RNC performs the serial

connection. The problem is mainly caused by some handsets.

(7) SHO_RL_ADD_FAIL_CFG_INVALID

UE regards the active set update of deleting radio links in RNC as invalid configuration. This reason seldom occurs in a commercial network.

(8) SHO_RL_ADD_FAIL_NO_RSP

RNC does not receive the acknowledgement of active set update of deleting radio links. Soft handover failure is mainly caused by this reason. If network coverage is poor or soft handover area is small, soft handover failure easily occurs. Thus, the RF optimization is required.

CS Inter-RAT Handover Analysis CS inter-RAT handover failure may be caused by the following reasons:

(1) CS_INTERRAT_HO_ FAIL_UNSPEC CS inter-RAT handover failure is caused by Unspecified (cause value). This reason seldom occurs in a network.

(2) CS_INTERRAT_HO_ FAIL_PHYCN_FAIL

CS inter-RAT handover failure is caused by Physical Channel Failure (cause value). CS inter-RAT handover failure is mainly caused by:

The signals of 2G network are weak or UE fails to access the network due to serious interference.

Some parameters (such as ciphering mode) transmitted to UE are inconsistent with that of BSC.

To locate the problem, compare the parameters of UE with that of BSC.

(3) CS_INTERRAT_HO_ FAIL_ CFG_UNSUPP

CS inter-RAT handover failure is caused by Configuration Unsupported (cause value) because UE does not support the handover request. This reason may be mainly caused by abnormal UE.

(4) CS_INTERRAT_HO_ FAIL_ RELOC_ABORT

After sending the handover request message to UE, RNC receives the release message from core network. However, the cause is not Normal Release because the link is released abnormally due to other reasons. This reason is caused by the nesting of handover process and release process.

(5) CS_INTERRAT_HO_ FAIL_NO_RSP

After RNC sends the handover request message to UE, UE does not acknowledge the request because network coverage is poor.

(6) CS_INTERRAT_HO_ FAIL_OTHER

CS inter-RAT handover failure is caused by other reasons. To locate the problem, analyze the RNC logs.

PS inter-RAT handover failure may be caused by the following reasons:

(1) PS_INTERRAT_HO_ FAIL_UNSPEC

PS inter-RAT handover failure is caused by Unspecified (cause value). This reason seldom occurs in a network.

(2) PS_INTERRAT_HO_ FAIL_PHYCN_FAIL

PS inter-RAT handover failure is caused by Physical Channel Failure (cause value) because the signals of 2G network are weak or UE fails to access the network due to serious interference.

(3) PS_INTERRAT_HO_ FAIL_ CFG_UNSUPP

PS inter-RAT handover failure is caused by Configuration Unsupported (cause value) because UE does not support the handover request. This reason may be mainly caused by abnormal UE.

(4) PS_INTERRAT_HO_ FAIL_NO_RSP

After RNC sends the handover request message to UE, UE does not acknowledge the request because network coverage is poor or UE does not support the handover.

Call Drop Analysis This section consists of the following parts:

CS Call Drop Analysis

PS Call Drop Analysis

Cell Call Drop Analysis

CS call drops may be caused by the following reasons:

(1) RAB_CS_REL_RF_LOSS

CS call drop may be caused by abnormal release caused by the lost synchronization of links because of poor network coverage (including adjacent cell missing, small handover area. As a result, UE closes the transmitter abnormally or uplink demodulation is asynchronous. To solve the problem, network coverage must be improved

(2) RNC_CS_RAB_REL_TRIG_BY_RNC_SRB_RESET CS call drops may be caused by link releasing due to downlink SRB reset. This reason is mainly caused by poor network coverage (including adjacent cell missing and small handover area). To solve the problem, the network coverage must be improved. In the early network, call drops are mainly caused by this reason.

(3) RNC_CS_RAB_REL_TRIG_BY_RNC_AAL2_LOSS

If IU CS interface (AAL2 path) is abnormal, RNC initializes the release. In practice, this reason seldom occurs. If this reason occurs, the problem may be caused by any faulty or defective equipment. In some versions of RNC, normal release is recorded as abnormal release during the RB setup process.

(4) CS_RAB_DROP_OTHER

CS call drops may be caused by other reasons. There are few call drop statistics in RNC (Version 12). Such reasons as process interaction timeout and cell update failure are recorded in CS_RAB_DROP_OTHER. In practice, many call drops are caused by process interaction timeout and cell update failure. Therefore, these call drops are recorded in CS_RAB_DROP_OTHER.

PS Call Drop Analysis PS call drop may be caused by the following reasons:

(1) RAB_PS_REL_RF_LOSS

PS call drops may be caused by abnormal release because the links are asynchronous. This reason is mainly caused by poor network coverage (including adjacent cell missing and small handover area). As a result, UE closes the transmitter abnormally or uplink demodulation is asynchronous.

(2) RNC_PS_RAB_REL_TRIG_BY_RNC_SRB_RESET PS call drops may be

caused by link releasing due to downlink SRB reset. This reason is mainly

caused by poor network coverage (including adjacent cell missing and small

handover area).

(3) RNC_PS_RAB_REL_TRIG_BY_RNC_TRB_RESET PS call drops may be caused by link releasing due to downlink TRB reset. This reason is mainly caused by poor network coverage (including adjacent cell missing and small handover area).

(4) RNC_PS_RAB_REL_TRIG_BY_RNC_GTPU_LOSS If IU CS interface (AAL2 path) is abnormal, RNC initializes the release. In practice, this reason seldom occurs. If this reason occurs, the problem may be caused by any faulty or defective equipment.

Cell Call Drop Analysis CS Cell call drops may be caused by the following reasons:

(1) RNC_CS_RAB_REL_CELL_TRIG_BY_RNC_OM

Cell call drops may be caused by CS link releasing due to operation and maintenance (for example, cell block). Actually, cell call drops caused by this reason are normal

(2) RNC_CS_RAB_REL_CELL_TRIG_BY_RNC_SRB_RESET Cell call drops may be caused by link releasing due to downlink SRB reset. This reason is mainly caused by poor network coverage (including adjacent cell missing and small handover area).

(3) RNC_CS_RAB_REL_CELL_TRIG_BY_RNC_UTRAN Cell call drops may be caused by abnormal link releasing due to UTRAN

(4) RNC_CS_RAB_REL_CELL_TRIG_BY_RNC_AAL2_LOSS If IU CS interface (AAL2 path) is abnormal, RNC initializes the release. In practice, this reason seldom occurs

(5) RNC_CS_RAB_REL_CELL_TRIG_BY_RNC_RAB_PREM Cell call drops may be caused by CS link releasing due to high priority preemption.