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					         3G Optimization Guidelines                                                     Mian Rizwan




                         1               Key Observation Point
                                      and Analysis Examples of
                                             Typical Problems

             An observation point is a PI which reflects a specific performance problem. The
             analysis based on an observation point is a process that goes deeper based on the
             familiarization of the UTRAN PI. Observation point analysis associates signaling
             process with performance index. Observation points are categorized as follows:
             1)   RRC establishment analysis observation point
             2)   RAB establishment analysis observation point
             3)   Soft handover analysis observation point
             4)   Call drop analysis observation point
             5)   CS/PS intersystem handover analysis observation point
             6)   Traffic analysis observation point
             7)   Key interface process analysis observation point
             8)   HSDPA analysis observation point
             An in-depth performance analysis can be made only after you have gained a mastery
             of observation points. The Nastar tool provides special topic query of most observation
             points. We may also make special topic query of other observation points by means of
             customization. Special topic drilling analysis of basic observation point helps deepen
             the understanding of signaling processes and various PIs and strengthen the mastery
             of the Nastar tool.




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         3G Optimization Guidelines                                                  Mian Rizwan




             Figure 1 Special topic analysis


1.1 Observation Points of Typical Problems
1.1.1 RRC Establishment Analysis Observation Point

Table 1 RRC Establishment Observation Point

 Observation                           Possible
                    Condition                                      Analysis Idea
    Point                                Cause

Categories of   Observe various                      If there are many streaming class called


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         3G Optimization Guidelines                                                       Mian Rizwan


 Observation                             Possible
                   Condition                                          Analysis Idea
    Point                                 Cause
RRC           types of RRC                             service requests (accounting for over 10%
establishment connection                               of total connection establishment
requests      establishment                            requests), we need to pay much attention
              requests and                             to them. This is because when UE changes
              their proportional                       from DCH status into IDLE status, PS
              distribution. If any                     needs to transmit packets, then ps paging
              abnormality, we                          occurs and the corresponding RRC
              need to give an                          requests are streaming class called service
              early warning.                           requests. If there are too many requests of
                                                       this type, it is possible that the timer from
                                                       DCH status to IDLE status is not properly
                                                       set.

                                                       It is generally caused by insufficient
                                                       transmission resource or transmission
                                      AAL2
                                                       fault. You may query the cell downlink
                                      establishment
                                                       throughput at the moment from associated
                                      failure
                                                       traffic statistics indexes. If it is lower than
                                                       200 kbps, transmission fault may occur.

                                                       It may be caused by NodeB fault or
                                                       insufficient NodeB resource. You may
                                      RL               query the maximum downlink CE of a cell
                                      establishment    from associated traffic statistics index. If
                Number of RRC
                                      failure          the maximum uplink CE is less than 20,
              connection
                                                       then traffic is not high and the problem lies
              establishment
RRC                                                    in abnormal NodeB equipment.
              failures (>=5);
establishment
              RRC connection                           RRM admission decision cannot establish
failure
              establishment                            any new RRC connection due to too high
              failure rate                             radio load within a cell. In this case, you
              (>=10%)                                  need to query the maximum RTWP and the
                                      Power            maximum TCP of the cell to confirm uplink
                                      congestion       congestion or downlink congestion and
                                                       judge whether any expansion is necessary.
                                                       Meanwhile, we should check whether
                                                       related admission strategy settings, such
                                                       as DCCC, are proper.

                                                       Uplink CE resource admission congestion
                                      Uplink CE        within an RNC. You need to query the
                                      congestion       number of uplink CEs of a cell from
                                                       relevant parameters and judge whether to


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         3G Optimization Guidelines                                                        Mian Rizwan


 Observation                             Possible
                   Condition                                           Analysis Idea
    Point                                 Cause
                                                        expand CE. If the number of uplink CEs is
                                                        less than 20, then traffic is not high and the
                                                        problem may lie in abnormal NodeB
                                                        equipment.
                                                        At present, RNC does not make an
                                                        accurate estimate of CE resource. It is
                                                        quite possible that RNC judges CE to be
                                                        sufficient, but actual NodeB CE resource is
                                                        insufficient. In addition, inconsistent
                                                        capability of RNC and NodeB may also
                                                        lead to NodeB RL establishment failure.

                                                        Downlink CE resource admission
                                                        congestion within an RNC. You need to
                                                        query the number of downlink CEs of a cell
                                                        from relevant parameters and judge
                                                        whether to expand CE. If the number of
                                                        uplink CEs is less than 40, traffic is not high
                                                        and the problem may lie in abnormal
                                      Downlink CE
                                                        NodeB equipment.
                                      congestion
                                                        At present, RNC does not make an
                                                        accurate estimate of CE resource. It is
                                                        quite possible that RNC judges CE to be
                                                        sufficient, but actual NodeB CE resource is
                                                        insufficient. In addition, inconsistent
                                                        capability of RNC and NodeB may also
                                                        lead to NodeB RL establishment failure.

                                                        Code resource fails to be allocated during
                                                        RRC connection establishment. Code
                                                        congestion is generally caused by too
                                                        many network users. It may be seen in high
                                      Code              traffic scenarios with microcell coverage.
                                      congestion        You may query the effective utilization of
                                                        codes from associated traffic statistics
                                                        indexes. If the effective utilization of codes
                                                        is lower than 30%, it is possible that the
                                                        code distribution algorithm is abnormal.

                                      Other             Generally the congestion caused by
                                      congestion        unknown insufficient resources. For
                                      leads to RRC      example, license resource and high CPU


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         3G Optimization Guidelines                                                      Mian Rizwan


 Observation                             Possible
                   Condition                                          Analysis Idea
    Point                                  Cause
                                      rejection.       utilization make flow control and FMR
                                                       processing capacity insufficient. In addition,
                                                       E1 fault also appears. This cause value is
                                                       dotted.

                                                       Transmission congestion is mainly caused
                                                       by insufficient transmission resource. You
                                                       may query the downlink cell throughput
                                                       from associated traffic statistics indexes. If
                                      Transmission     the downlink cell throughput is lower than
                                      congestion       200 kbps, it is possible that there is
                                                       abnormal equipment. The power-down of a
                                                       base station once led to transmission
                                                       interruption, but the cause in traffic
                                                       statistics is transmission congestion.

                                                       Abnormal causes. We need to make
                                                       in-depth location based on RNC logs. The
                                      Other factors    known problem is that the system
                                      lead to RRC      redirection function of the network is
                                      rejection.       enabled. During redirection, a mobile
                                                       phone does not support GSM and thus
                                                       failure rejection occurs.

                                                       This is generally caused by poor coverage.
                                      No response
                                                       The downlink FACH and RACH have
                                      from UE
                                                       unbalanced coverage.

                                                       This is generally caused by an RNC fault.
                                                       At present, there is a problem with traffic
                                                       statistics mode, which may lead to some
                                                       wrong dotting of this cause.
                                                       There was a problem with the designated
                                      Other factors
                                                       access DSP of node B. The RRC
                                      lead to RRC
                                                       CONNECTION SETUP REQUEST
                                      establishment
                                                       message fails to be sent to RNC. The
                                      failure.
                                                       RACH packet decoding of this cell fails. We
                                                       may make a judgment by checking whether
                                                       the index
                                                       VS.MAC.CRNCIubBytesRACH.Tx is
                                                       abnormal.




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         3G Optimization Guidelines                                                     Mian Rizwan

1.1.2 RAB Establishment Analysis Observation Point

Table 2 RAB establishment observation point

 Observation                             Possible
                   Condition                                         Analysis Idea
   Point                                  Cause

                                                      Generally transmission equipment fault or
                                      Transmission    insufficient transmission capacity. You
                                      network         need to query the transmission utilization of
                                                      that time.

                                                      In starting migration, RNC receives a RAB
                                                      establishment request, but does not
                                                      process it. This is mainly caused by flow
                                      Migration
                                                      nesting and seldom occurs. It is related to
                                                      user behavior sequence. This is generally
                                                      avoided in a core network.

                                                      RRM admission decision cannot establish
                                                      any new RRC connection due to too high
                                                      radio load within a cell. In this case, you
                Number of                             need to query the maximum RTWP and the
                CS/PS RAB             Power           maximum TCP of the cell to make sure of
                                      congestion      uplink congestion or downlink congestion
               establishment
 CS/PS RAB                                            and judge whether any expansion is
               failures (>=5);
 establishment                                        necessary. Meanwhile, we should check
               CS/PS RAB
 failure                                              whether related admission strategy
               establishment
               failure rate                           settings, such as DCCC, are proper.
               (>=10%)                                Uplink CE resource admission congestion
                                                      within an RNC. You need to query the
                                                      number of uplink CEs of a cell from
                                                      relevant parameters and judge whether to
                                                      expand CE. If the number of uplink CEs is
                                                      less than 20, then traffic is not high and the
                                                      problem may lie in abnormal NodeB
                                      Uplink CE
                                                      equipment.
                                      congestion
                                                      At present, RNC does not make an
                                                      accurate estimate of CE resource. It is
                                                      quite possible that RNC judges CE to be
                                                      sufficient, but actual NodeB CE resource is
                                                      insufficient. In addition, inconsistent
                                                      capability of RNC and NodeB may also
                                                      lead to NodeB RL establishment failure.



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         3G Optimization Guidelines                                                         Mian Rizwan


 Observation                             Possible
                   Condition                                            Analysis Idea
   Point                                  Cause

                                                         Downlink CE resource admission
                                                         congestion within an RNC. You need to
                                                         query the number of downlink CEs of a cell
                                                         from relevant parameters and judge
                                                         whether to expand CE. If the number of
                                                         uplink CEs is less than 40, then traffic is not
                                                         high and the problem may lie in abnormal
                                      Downlink CE
                                                         NodeB equipment.
                                      congestion
                                                         At present, RNC does not make an
                                                         accurate estimate of CE resource. It is
                                                         quite possible that RNC judges CE to be
                                                         sufficient, but actual NodeB CE resource is
                                                         insufficient. In addition, inconsistent
                                                         capability of RNC and NodeB may also
                                                         lead to NodeB RL establishment failure.

                                                         Code resource fails to be allocated during
                                                         RRC connection establishment. Code
                                                         congestion is generally caused by too
                                                         many network users. It may be seen in high
                                      Code               traffic scenarios with microcell coverage.
                                      congestion         You may query the effective utilization of
                                                         codes from associated traffic statistics
                                                         indexes. If the effective utilization of codes
                                                         is lower than 30%, it is possible that the
                                                         code distribution algorithm is abnormal.

                                                         Transmission congestion is mainly caused
                                                         by insufficient transmission resource. You
                                                         may query the downlink cell throughput
                                                         from associated traffic statistics indexes. If
                                      Transmission       the downlink cell throughput is lower than
                                      congestion         200 kbps, it is possible that there is
                                                         abnormal equipment. The power failure of
                                                         a base station once led to transmission
                                                         interruption, but the cause in traffic
                                                         statistics is transmission congestion.

                                                         Abnormal causes. We need to make an
                                      Others
                                                         in-depth location based on RNC logs.

                                      Air interface      The air interface failure occurring during



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         3G Optimization Guidelines                                                        Mian Rizwan


 Observation                             Possible
                   Condition                                            Analysis Idea
   Point                                  Cause
                                      failure             RB establishment is generally caused by
                                                          poor coverage or mobile phone
                                                          compatibility.

                                                          The compatibility of a mobile phone itself
                                                          becomes faulty in some unknown
                                                          scenarios. For example, when a Huawei
                                      Configuration       mobile phone drops network abnormally, it
                                      not supported       may not release any RB. When PS RB is
                                                          set up next time, this case may occur. This
                                                          case also happens to the SE V800 mobile
                                                          phone.

                                                          This generally occurs when FACH migrates
                                                          to DCH and sets up RB. The downlink
                                      Physical            physical layer of a terminal is not
                                      channel failure     synchronized, which leads to RB
                                                          establishment failure. This is mainly caused
                                                          by poor coverage.

                                                          The Cell Update flow occurs during RB
                                      Cell update         establishment. This nested flow leads to
                                                          RB establishment failure.

                                                          UE considers parameter configuration
                                                          illegal. Network and terminals have an
                                                          inconsistent understanding of parameter
                                                          processing. If RB establishment failure
                                      Illegal
                                                          occurs in the domain of CS, it is possible
                                      configuration
                                                          that a user dials a wrong telephone number
                                                          and at once goes onhook. RB SETUP
                                                          failure may also occur at this time. The
                                                          cause is illegal configuration.

                                      No response         Generally poor coverage makes UE unable
                                      from UE             to receive any RB establishment command.

                                                      RNC considers the parameter delivered by
                                                      a core network invalid. You need further
                                                      cell signaling tracing to determine the
                                      Parameter error cause. Among the known causes is that the
                                                      uplink subscription and activation
                                                      application information of user PS service
                                                          exceeds the capacity of a mobile phone, or


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         3G Optimization Guidelines                                                      Mian Rizwan


 Observation                             Possible
                   Condition                                          Analysis Idea
   Point                                  Cause
                                                        that the network negotiation rate in PDP
                                                        activation acceptance messages is less
                                                        than the minimum guaranteed rate.



1.1.3 Call Drop Analysis Observation Point

Table 3 CS/PS call drop observation point

 Observation                             Possible
                   Condition                                          Analysis Idea
   Point                                  Cause

                                                      Call drop caused by operation and
                                                      maintenance. For example, the execution
                                      OM intervention
                                                      of TRG RABRel on LMT causes users to
                                                      be released.

                                                        High-priority users preempt low-priority
                                                        users when admission is rejected. This
                                                        causes a link to be released. This kind of
                                      RAB
                                                        call drop occurs in the case of load and
                                      preemption
                                                        insufficient resource. Determine whether
                                                        expansion is necessary according to the
                                                        number of occurrences.

                                                        Within a cell, UTRAN leads to abnormal
                                                        link release. This case generally
 CS/PS call     High CS/PS call
                                      UTRAN             corresponds to processing abnormality. We
 drop           drop rate
                                                        need to make a further analysis by means
                                                        of CDL.

                                                         Uplink or downlink signaling RB reaches
                                                        the maximum retransmission times and
                                                        resets. This causes a link to be released.
                                      Uplink/downlink
                                                        This case is mainly caused by poor
                                      RLC reset
                                                        coverage quality (including missing
                                                        configuration of adjacent cells and small
                                                        handover area).

                                                        RNC receives RL Failure reported by
                                      Uplink
                                                        NodeB, which causes a link to be
                                      synchronization
                                                        abnormally released. In this case, poor
                                      failure
                                                        coverage quality (including missing



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         3G Optimization Guidelines                                                          Mian Rizwan


 Observation                             Possible
                   Condition                                             Analysis Idea
   Point                                  Cause
                                                         configuration of adjacent cells and small
                                                         handover area) makes UE abnormally shut
                                                         down the transmitter, or uplink
                                                         demodulation out-of-sync.

                                                         Receive the Cell Update message reported
                                                         by a mobile phone. The cause is downlink
                                                         RL Failure, which makes a link abnormally
                                      Downlink           released. In this case, poor coverage
                                      synchronization    quality (including missing configuration of
                                      failure            adjacent cells and small handover area)
                                                         makes UE abnormally shut down the
                                                         transmitter, or uplink demodulation
                                                         out-of-sync.

                                                      RNC delivers a message and waits for the
                                                      response from a mobile phone, but timeout
                                      The UU          occurs. For example, waiting for RB
                                      interface makes reconfiguration completion message times
                                      no response.       out and waiting for active set update
                                                         completion times out. This case is
                                                         generally caused by poor coverage.

                                      Other RF
                                                         RF cause; due to poor coverage quality
                                      causes

                                                    RNC finds that the AAL2 Path of the IU CS
                                                    interface is abnormal and starts abnormal
                                                    release. It is possible that the transmission
                                      Abnormal AAL2 equipment of the Iu interface is abnormal.
                                      link          The known problem is that immediate
                                                    normal release during RB establishment is
                                                    classified by traffic statistics into abnormal
                                                         release.

                                                         RNC finds that the GTPU of the IU PS
                                      Abnormal           interface is abnormal and starts abnormal
                                      GTPU               release. The cause may be equipment fault
                                                         or defect.

                                                         Possibly the call drop (but traffic statistics
                                      Others             does not dot) occurring during flow
                                                         interaction or cell update, or abnormal call



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         3G Optimization Guidelines                                                   Mian Rizwan


 Observation                          Possible
                   Condition                                       Analysis Idea
   Point                               Cause
                                                    drop and cell blocking caused by the
                                                    transmission fault of the Iub interface, RNC
                                                    internal cause, and Bug. There may be call
                                                    drop for abnormal causes. We need to
                                                    make an analysis based on RNC logs. The
                                                    call drop caused by violent change (corner
                                                    effect or driving out from the shadow area
                                                    of a building) of uplink signal is known to be
                                                    classified into this cause.




1.1.4 Soft Handover Analysis Observation Point

Table 4 Soft handover analysis observation point

 Observation                           Possible
                   Condition                                       Analysis Idea
     Point                              Cause

                                                    Possible causes of too high (>= 40%) a
                                                    soft handover rate:
                                                    1)   Handover parameter setting makes
                                                         addition easy, but deletion difficult.
                Soft handover
                rate based on                       2)   In the early days of network
                cell resource                            construction, there are few base
 Soft           allocation and                           stations and insufficient coverage.
 handover       soft handover                            Therefore, capacity gives way to
 rate           rate based on                            quality.
                IUB transmission                    3)   The CN side of some partners does
                resource                                 not deliver Iu release. After a user’s
                allocation.                              dial-up access is disconnected, there
                                                         is only user plane release instead of
                                                         signaling plane release. Users have
                                                         soft handover even after a network is
                                                         disconnected.

                Number of                           UE considers that the content of the active
 Soft           soft/softer       Configuration     set update of RNC adding/deleting a link is
 handover       handover failures not supported     not supported. Generally, this scenario will
 execution      (>=5) and                           not appear in commercial use.
 failure        soft/softer       Synchronization   UE gives the feedback that the softer/soft
                handover failure reconfiguration    handover process of RNC adding/deleting



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          3G Optimization Guidelines                                                           Mian Rizwan


 Observation                               Possible
                     Condition                                               Analysis Idea
     Point                                  Cause
                  rate (>=10%)         not supported       a link is incompatible with other concurrent
                                                           processes. RNC has guaranteed serial
                                                           flow processing. Soft handover execution
                                                           failure is mainly caused by the problematic
                                                           processing of some mobile phones.

                                                           UE considers that the content of the active
                                       Illegal             set update of RNC adding/deleting a link is
                                       configuration       illegal. Generally, this scenario will not
                                                           appear in commercial use..

                                                           RNC does not receive the active set
                                                           update command response for
                                                           adding/deleting a link. This is the main
                                       No response
                                                           cause of softer/soft handover failure. This
                                       from UE
                                                           happens in the region with poor coverage
                                                           or a small handover area. It needs RF
                                                           optimization.




1.1.5 CS/PS Intersystem Handover Analysis Observation Point

Table 5 Intersystem handover observation point

 Observation
                     Condition         Possible Cause                        Analysis Idea
   Point

                  Preparation
                  failures (>=5) of
                                                               Radio link establishment failure occurs
                  hard handover
 Hard                                                          during RL establishment. For details, see
                  into this cell and
 handover                                                      the RL establishment process analysis of
                  preparation
 preparation                                                   the IUB interface.
                  failure rate
 failure                                                       For other causes, we need to make a
                  (>=10%) of hard
                                                               further analysis based on RNC logs.
                  handover into
                  this cell

 Preparation      Preparation          A target cell has
                                                               A target cell has no resource available, or
 failure of       failures (>=5) of    no wireless
                                                               there is some RNC parameter
 transition out   transition out of    network
                                                               configuration error. We need to make an
 of cell          cell accompanied     resource
                                                               analysis based on RNC logs.
 accompanied      by hard handover     available.




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         3G Optimization Guidelines                                                           Mian Rizwan


 Observation
                   Condition          Possible Cause                       Analysis Idea
   Point
 by hard        and preparation                              The problem often lies in CN parameter
 handover       failure rate          Transition
                                                             configuration or a related link connection.
                (>=10%) of            timeout of target
                                                             We need to make an analysis based on
                transition out of     system
                                                             RNC logs.
                cell accompanied
                by hard handover      Transition failure
                                      in the target      It generally corresponds to core network
                                      CN/RNC or          configuration error.
                                      system

                                      Transition in the
                                                             Generally, RNC does not support some
                                      target CN/RNC
                                                             hard handover parameters. We need to
                                      or system not
                                                             make an analysis based on RNC logs.
                                      supported

                                      Transition             Often an MSC parameter configuration
                                      objective not          error. We need to check the parameter
                                      allowed                configuration of a core network.

                                                             Failure caused by operation and
                                      OM intervention
                                                             maintenance

                                                             Often an MSC parameter is configured
                                      No available
                                                             incorrectly, or a target RNC has no
                                      resource
                                                             resource available.

                                                             Failure causes are not defined in traffic
                                      Undefined
                                                             statistics.

                                                             We need to make an analysis based on
                                      Others
                                                             RNC logs.

                Preparation                                  A core network does not return a
 Preparation    failures (>=5) of                            corresponding command of handover
 failure of     RNC-level             Waiting for            preparation request. In this case, there is
 RNC-level      CS/PS domain          transition             some problem with the parameter
 foreign        intersystem           command                configuration or related link connection of
 outgoing       outgoing              timeout                a core network. We need to analyze the
 handover       handover,                                    cause according to the signaling trace of
                preparation                                  the core network and BSS.




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         3G Optimization Guidelines                                                          Mian Rizwan


 Observation
                   Condition          Possible Cause                       Analysis Idea
   Point
                failure rate                                 Upon requesting handover preparation,
                (>=10%)of CS                                 RNC receives the release command from
                domain                                       a core network. Two cases: intersystem
                intersystem                                  handover request occurs during signaling
                outgoing                                     process like location update. The location
                handover              Transition             update flow has been finished before one
                                      cancelled              flow is finished. The core network starts
                                                             release; the user who sets up a call goes
                                                             onhook during handover preparation, and
                                                             the core network starts release. No
                                                             handover is finished in either case, but
                                                             either is normal flow nesting.

                                                             It generally corresponds to core network
                                      Transition             configuration error. We need to analyze
                                      timeout                the cause according to the signaling
                                                             tracing of a core network and a BSS.

                                                             The problem often lies in the parameter
                                      Transition failure
                                                             configuration or related link connection of
                                      in the target
                                                             a core network. We need to analyze the
                                      CN/RNC or
                                                             cause according to the signaling tracing of
                                      system
                                                             a core network and a BSS.

                                                             The problem often lies in an MSC
                                                             parameter configuration error. That is, the
                                                             LAC of the target cell fails to be
                                      Unknown target
                                                             configured. We need to check the
                                      RNC
                                                             parameter configuration of a core network.
                                                             This case is often seen after the
                                                             adjustment of 2 G network.

                                                             The problem often lies in an MSC
                                                             parameter configuration error, or BSC has
                                      No available
                                                             no resource available. We need to analyze
                                      resource
                                                             the cause according to the signaling
                                                             tracing of a core network and a BSS.

                                                             We need to analyze the cause according
                                      Others                 to the signaling tracing of a core network
                                                             and a BSS.




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          3G Optimization Guidelines                                                           Mian Rizwan


 Observation
                      Condition        Possible Cause                       Analysis Idea
   Point

                                                              The problem often lies in the parameter
                                                              configuration or related link connection of
                                       Transition
                                                              a core network. We need to analyze the
                                       timeout
                   Preparation                                cause according to the signaling tracing of
                   failures (>=5) of                          a core network and a BSS.
                   CELL-level CS
                   domain                                 It generally corresponds to core network
                                       Transition failure
 Preparation       intersystem                            configuration error or BSS not supporting.
                                       in the target
 failure of        outgoing                               We need to analyze the cause according
                                       CN/RNC or
 Cell-level        handover and                           to the signaling tracing of a core network
                                       system
 foreign           preparation                            and a BSS.
 outgoing          failure rate                               In this case, a BSC does not support some
 handover          (>=10%) of CS       Transition in the
                                                              parameters of intersystem handover
                   domain              target CN/RNC
                                                              requests. We need to analyze the cause
                   intersystem         or system not
                                                              according to the signaling tracing of a core
                   outgoing            supported
                                                              network and a BSS.
                   handover.
                                                              We need to analyze the cause according
                                       Others                 to the signaling tracing of a core network
                                                              and a BSS.

                                                              UE considers that the command for hard
                                       Configuration          handover out of a cell is not supported.
                                       not supported          The problem generally lies in the
 Outgoing                                                     compatibility of a mobile phone.
 hard
 handover          Failures (>=5) of   Physical channel Possibly poor coverage or severe
 failures within   hard handover       failure          interference
 NODE B,           out of a cell,                             UE gives the feedback that hard handover
 between           failure rate        Synchronization        process is incompatible with other
 different         (>=10%) of hard     reconfiguration        concurrent processes. The problem may
 NodeBs            handover out of a   not supported          lie in the compatibility of a mobile phone
 within RNC,       cell                                       itself.
 and between
 RNCs                                                         Cell update happens during hard
                                       Cell Updating          handover out of a cell. This flow nesting
                                       Procedure              leads to the failure of hard handover out of
                                                              a cell.




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           3G Optimization Guidelines                                                           Mian Rizwan


 Observation
                     Condition          Possible Cause                       Analysis Idea
   Point

                                                               UE considers that the command for hard
                                        Illegal                handover out of a cell is illegal. The
                                        configuration          problem generally lies in the compatibility
                                                               of a mobile phone.

                                                               We need to make a further analysis based
                                        Others
                                                               on RNC logs.

                                                               UE considers that the command for
                                                               transition out of a cell accompanied by
                                        Configuration
                                                               hard handover is not supported. The
                                        not supported
                                                               problem generally lies in the compatibility
                                                               of a mobile phone.

                                        Physical channel Possibly poor coverage or severe
                  Execution
                                        failure          interference
                  failures (>=5) of
                  transition out of a                          UE gives the feedback that the hard
 Failure of
                  cell accompanied Synchronization             handover process of RNC adding a link is
 transition out
                  by hard             reconfiguration          incompatible with other concurrent
 of a cell
                  handover,           incompatible             processes. The problem may lie in the
 accompanied
                  execution failure                            compatibility of a mobile phone itself.
 by hard
                  rate (>=10%) of
 handover                                                      UE considers that the command for
                  transition out of a
                  cell accompanied Illegal                     transition out of a cell accompanied by
                  by hard handover configuration               hard handover is illegal. This case seldom
                                                               occurs.

                                        Configuration
                                        not finished

                                                               We need to make a further analysis based
                                        Others
                                                               on RNC logs.

 CS/PS            CS/PS domain                                 The handover command terminal in a
 foreign          intersystem       Configuration              network does not provide support. The
 handover         handover failures not supported              problem generally lies in the compatibility
 failure          (>=5), CS/PS                                 of a mobile phone.




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 Observation
                    Condition          Possible Cause                        Analysis Idea
   Point
                 domain                                        1)   Poor 2 G signal or severe interference
                 intersystem                                        leads to UE access failure.
                 handover failure                              2)   The channel parameters, including
                 rate (>=10%)                                       the encryption mode sent from
                                                                    network to UE, are inconsistent with
                                                                    those of a BSC. We need to compare
                                       Physical channel
                                                                    and confirm the parameters of a
                                       failure
                                                                    terminal and those of a BSC. Physical
                                                                    channel failure generally occurs in a
                                                                    network with partners’ equipment as
                                                                    the CN. We need to check the
                                                                    encryption algorithm configuration of
                                                                    an MSC and an SGSN.

                                                               We need to make a further analysis
                                                               according to RNC logs, together with the
                                                               signaling tracing of a core network and a
                                                               BSS. Improper service capability
                                       Others
                                                               configuration of 2 G cell makes high-rate
                                                               service unable to start a pressing mould,
                                                               which leads to system PS handover
                                                               failure.




1.1.6 Traffic Analysis Observation Point

Table 6 Traffic analysis observation point

   Observation
                            Condition                                    Analysis Idea
     Point

                                                    Observe whether “the maximum uplink CE
                    Lay an emphasis upon
                                                    resource occupied” approaches 128. If it does, an
                    the analysis of “average
                                                    early warning needs to be given to expansion.
                    uplink CE resource
 Uplink CE                                          Normally, when the “average uplink CE resource
                    occupied” and “the
                                                    occupied” is less than 60 CE Erlang,
                    maximum uplink CE
                                                    whole-network busiest-hour cell traffic is very
                    resource occupied”.
                                                    small.




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   Observation
                             Condition                             Analysis Idea
       Point

                                                Observe whether “the maximum downlink CE
                     Lay an emphasis upon
                                                resource occupied” approaches 128. If it does, an
                     the analysis of “average
                                                early warning needs to be given to expansion.
                     downlink CE resource
 Downlink CE                                    Normally, when the “average downlink CE
                     occupied” and “the
                                                resource occupied” is less than 60 CE Erlang,
                     maximum downlink CE
                                                whole-network busiest-hour cell traffic is very
                     resource occupied”
                                                small.

                  List the average TCP,
                                                If the average transmit power of a cell is large and
 Average transmit the maximum TCP and
                                                there is small traffic, it indicates that there is poor
 power of cell    the minimum TCP of a
                                                downlink coverage.
                  cell.

                     List the average TCP,
 Maximum                                        If the maximum transmit power of a cell is large
                   the maximum TCP and
 transmit power of                              and there is small traffic, it indicates that power
                   the minimum TCP of a
 cell                                           peak shock may lead to power congestion.
                   cell.

 Minimum           Observe whether the          If the minimum transmit power of a cell is
 transmit power of minimum transmit power       abnormal, the transmit channel may become
 cell              of a cell is abnormal.       faulty.

                     List the average RTWP,
                     the maximum RTWP,      If the average RTWP of a cell is higher than -95
 Average RTWP
                     and the minimum RTWP dBm, there may be downlink interference.
                     of a cell.

                                                Among various items, RTWP peaks, for example,
              Observe whether there
 Maximum RTWP                                   -70 dBm, often appear. This may be caused by the
              are many peaks.
                                                power of access process or handover process.

                     Observe whether the        If the minimum RTWP is lower than -108 dBm, a
 Minimum RTWP        minimum RTWP is less       channel fails to be corrected, or a base station
                     than -105.5 dBm.           encounters power-down.

                                                If the effective utilization of codes is not high (<=
 Effective           Observe whether the
                                                30%), but code congestion leads to access failure,
 utilization of      code utilization is
                                                it is possible that the code distribution algorithm is
 codes               abnormal.
                                                abnormal.

                                                Observe whether the uplink throughput of a cell is
 Uplink             Observe the uplink          great. If it amounts to 75% of the transmission
 throughput of cell throughput of a cell.       capability of a base station, transmission
                                                expansion needs to be considered.



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   Observation
                            Condition                                 Analysis Idea
       Point

                                                   Observe whether the downlink throughput of a cell
 Downlink           Observe the downlink           is great. If it amounts to 75% of the transmission
 throughput of cell throughput of a cell.          capability of a base station, transmission
                                                   expansion needs to be considered..

                                                   This is generally caused by transmission
                                                   interruption or intermittent transmission failure.
                    List the cell unavailability
 Cell status                                       Some offices are greatly influenced by weather
                    duration and its
 monitoring                                        due to the use of microwave transmission.
                    proportion.
                                                   Thunder storm always leads to intermittent
                                                   transmission failure.

 Missing                                           If 1A events often happen within many
                    List the number of cell
 configuration of                                  consecutive days, there may be missing
                    1A events.
 adjacent cell                                     configuration of adjacent cells.

 Excess
 configuration of
 adjacent cells

                    List the number of cell        If 1C events often happen within many
 Pilot Pollution:
                    1C events.                     consecutive days, there may be pilot pollution.




1.1.7 Key Interface Flow Analysis Observation Point

Table 7 Key interface flow analysis observation point

   Observation                                Possible
                        Condition                                          Analysis Idea
       Point                                   Cause

                                                             The problem may lie in the compatibility
                                                             of a mobile phone. A mobile phone
                                                             terminal may detect the SQN error of in
                                          Radio              an AUTN message, which leads to
                    IU security mode      network layer      failure. Cause value: Synch failure!
 Security mode      failures, IU                             Respective encryption modes of CS
 flow failure       security mode                            domain and PS domain may also lead to
                    failure rate                             a security mode failure.

                                          Transmission       Correspond to transmission link
                                          layer              abnormality.

                                          Network


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   Observation                               Possible
                         Condition                                       Analysis Idea
       Point                                    Cause
                                           optimization

                                           Undefined

                                           OM               RL failure of IUR interface caused by
                                           intervention     operation and maintenance

                                                            This generally corresponds to equipment
                                           Hardware
                                                            abnormality. We should first query
                                           failure
                                                            related equipment alarm.
 RL
                      List the number of
 establishment                                              This is caused by insufficient RNC
                      RL establishment
 failure of the IUR                                         internal resource. You need to query the
                      failures (>= 5) of   RNC resource
 interface                                                  quantity of related users to judge
                      the Iur interface of unavailable
 RL                                                         whether there is any equipment
                      the SRNC, RL
 synchronization                                            abnormality.
                      establishment
 configuration
                      failure rate (>=                      UE considers that the RL configuration
 failure of the IUR
                      10%) of the Iur      Configuration    content of RNC establishment is not
 interface
                      interface of the     not supported    supported. The problem lies in the
 RL addition
                      SRNC, and main                        compatibility of a mobile phone.
 failure of the IUR
                      failure causes.
 interface
                                                            Abnormal causes. We need to make an
                                           Others
                                                            analysis based on RNC logs.

                                                            This generally corresponds to equipment
                                           No response      abnormality. We need to query whether
                                                            there is any power-down.

                                                            The problem lies in the compatibility of a
                                           Configuration
                                                            mobile phone itself in some unknown
                                           not supported
 RL                                                         scenarios.
                      List the number of
 establishment                                              Insufficient RNC internal resource or
                      RL establishment
 failure of the                                             abnormal RNC equipment. You need to
                      failures of the IUB
 IUB interface RL                                           query cell CE resource from relevant
                      interface, RL
 reconfiguration                                            parameters to judge whether there is any
                      establishment
 failure of the IUB                                         equipment abnormality. Equipment is
                      failure rate of the No available
 interface                                                  known to encounter repeated power
                      Iub interface, and resource
 RL addition                                                failure and air-conditioner fault due to
                      main failure
 failure of the IUB                                         thunder storm. As a result, high
                      causes.
 interface                                                  temperature leads to abnormality of
                                                            various kinds. Besides, the NLPA board
                                                            encounters shutdown.




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   Observation                            Possible
                       Condition                                          Analysis Idea
      Point                                  Cause

                                                         This generally corresponds to equipment
                                        Equipment
                                                         abnormality. We should first query
                                        fault
                                                         related equipment alarm.

                                                         RL establishment failure caused by
                                        OM
                                                         operation and maintenance (for example,
                                        intervention
                                                         cell blocking)

                                                         The problem may lie in cell unavailability
                                                    or equipment fault. You need to query
                                        NodeB makes
                                                    the cell unavailability duration from
                                        no response
                                                    relevant parameters to judge whether
                                                    there is any equipment fault.

                                                         RL establishment failure caused by
                                                         abnormal factors. We need to make an
                                                         analysis based on RNC logs
                                                         RL reconfiguration failure caused by
                                                         abnormal factors. We need to make an
                                                         analysis based on RNC logs. The known
                                                         causes are that transmission congestion
                                                         (Received Iub AAL2 type1 setup
                                                         response message from AL but result is
                                        Others
                                                         5 not success!) and improper T314/T315
                                                         parameter setting make there not be any
                                                         opportunity of RL reconfiguration. RL
                                                         addition failure caused by abnormal
                                                         factors. We need to make an analysis
                                                         based on RNC logs. It is known that RL
                                                         addition failure caused by restricted IUB
                                                         transmission bandwidth will be classified
                                                         into this cause value.
                                                         The problem lies in the compatibility of a
 RB                RB establishment                      mobile phone itself in some unknown
 establishment     failure generally                     scenarios. For example, when a Huawei
 failure           corresponds to                        mobile phone drops network abnormally,
 RB                poor air interface   Configuration    it may not release any RB. When PS RB
 reconfiguration   coverage or a        not supported    is reestablished next time, this case may
 failure           mobile phone                          occur. This case also happens to SE
 RB deletion       compatibility                         V800 mobile phone. Or when some UEs
 failure           problem.                              implement VP and high-speed (greater
                                                         than or equal to 64K) PS service, failure


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   Observation                          Possible
                       Condition                                   Analysis Idea
      Point                              Cause
                                                      may also due to unsupported capability.
                                                      This generally occurs when FACH
                                                      migrates to DCH and establishes RB.
                                      Physical
                                                      The downlink physical layer of a terminal
                                      channel
                                                      is not synchronized, which leads to RB
                                      failure
                                                      establishment failure. This is mainly
                                                      caused by poor coverage.
                                                      The Cell Update flow occurs during RB
                                      Cell update     establishment. This nested flow leads to
                                                      RB establishment failure.
                                                      UE considers parameter configuration
                                                      illegal. Network and terminals have an
                                                      inconsistent understanding of parameter
                                                      processing. If RB establishment failure
                                                      occurs in the domain of CS, it is possible
                                                      that a user dials a wrong telephone
                                                      number and immediately goes onhook.
                                                      RB SETUP failure may also occur at this
                                                      time. The cause is illegal configuration.
                                                      Or when a 3 G terminal as the caller
                                                      implements VP service, the called party
                                      Illegal         resides in a GSM network and does not
                                      configuration   support VP service. Thus, after RNC
                                                      receives an RAB assignment request, a
                                                      core network immediately delivers the
                                                      Disconnect command upon Call
                                                      Proceeding (the cause is Bearer
                                                      capability not authorized). But UE has
                                                      just received an RB_SETUP command
                                                      at this time and has no time to complete
                                                      RB establishment. Upon receiving this
                                                      Disconnect command, UE initiates a
                                                      response “RB establishment failure” and
                                                      RNC returns RAB establishment failure.
                                                      Generally poor coverage makes UE
                                                      unable to receive any RB command. In
                                      No response     Hong Kong, the balance mechanism of
                                      from UE         IUB once made signaling established on
                                                      one E1, but service was established on
                                                      another E1. Thus, there has been no


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   Observation                               Possible
                         Condition                                        Analysis Idea
      Point                                   Cause
                                                            problem with signaling, but RB
                                                            establishment may fail. In this case, it is
                                                            this cause value that is returned.
                     Observe whether
                                                            PS has a large amount of 128k, 144k,
                    the number of
 RB bearer                                                  and 384k RB bearer. This will consume a
                    various types of
 distribution of                                            large number of resources and there is
                    RB service bearer
 uplink/downlink                                            poor coverage. We need to verify
                    and the
 service                                                    whether RB bearer is consistent with
                    proportion are
 Uplink/downlink                                            actual demands with first-line personnel.
                    abnormal. If there
 RB bearer                                                  Observe whether the RB distribution of
                    is any
 distribution of BE                                         BE service is rational. According to the
                    abnormality, an
 service                                                    distribution, DCCC strategy and related
                    early warning
                                                            system parameters can be adjusted.
                    needs to be given




1.1.8 HSDPA Analysis Observation Point

              RNC1.6 version supports the following KPI monitoring: HSDPA service establishment
              success rate, HSDPA call drop rate, HSDPA cell throughput, H <-> H
              intra-/inter-frequency serving cell update success rate and H <-> R99 intra-frequency
              handover success rate. It does not support the following KPI monitoring: HSDPA
              average uplink and downlink throughput for a single user, H <-> R99 inter-frequency
              handover success rate, H -> GPRS intersystem handover success rate, statistics of
              the causes for HSDPA service establishment failure, statistics of the causes for
              HSDPA call drop failure, statistics of the causes for H <-> H intra-/inter-frequency
              serving cell update failure, statistics of the causes for H <-> R99 intra-/inter-frequency
              handover failure, statistics of the causes for H -> GPRS intersystem handover failure.
              Therefore, we cannot use traffic statistics for HSDPA all-KPI monitoring and analysis,
              but need to use other supplementary means. It is recommended to use driving test
              and signaling tracing for routine monitoring of the indexes not supported by RNC1.6
              version. Meanwhile, analyze and locate KPI abnormality.
              RNC1.7 traffic statistics is being collated and remains to be supplemented.

1.2 Example of Analysis Based on Observation Point
              Take RRC establishment problem analysis for example.
              1. Overall analysis of RRC establishment
              As shown in Figure 1 the task window of the Nastar is embedded with the special topic
              analysis of call completion rate——RRC Setup Analysis. Double click to start this



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             query to get the general information about RNC-level RRC establishment. As shown in
             the following figure, RRC establishment success rate reaches 98.84%. Most of RRC
             establishment failure is because there is no response to RRC Setup command
             delivery (7,373 times). Eighteen failures are because of RRC Setup Reject.




             Figure 2 General information about RRC setup


             The main cause of the exemplified RRC establishment failure is that there is no
             response to RRC Setup command delivery. It is unbalanced coverage of downlink
             FACH and uplink RACH. For an early network, coverage cannot be guaranteed, so
             there are a large number of areas with poor coverage quality. These areas with poor
             coverage always correspond to intersystem rerouting areas. On the other hand, where
             there are many users or equipment problems within a cell, RRC establishment
             rejection is also a major cause of RRC establishment failure.
             2. Analysis of RRC establishment scenario
             One important reason for RRC establishment failure is poor coverage. We may make
             a further analysis by using the establishment cause distribution and success rate of
             different RRCs establishment. Get results by starting related query and selecting
             Scenario Analysis to present a selected RNC in the form of a pie chart and a bar chart.




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             Figure 3 Distribution of RRC setup scenario




             Figure 4 Comparison of RRC setup scenario success rate


             Scenario Analysis makes a comparative analysis of several commonly used scenarios.
             The pie chart shows the RRC establishment distribution of a main scenario. The
             example in the chart indicates that RRC establishment requests mainly exist in
             network registration with REG as the cause. When an LAC area is not well planned or
             there is poor coverage (the margin of LAC division is in a prosperous area), there may
             be a lot of registration. On the other hand, the cause of RRC establishment during
             intersystem reselecting of this mobile phone is registration. A large number of mobile
             phones fail to be registered due to poor coverage and will try again and again. Thus,
             the cause of RRC establishment is registration in many cases. This indicates that
             there is poor network coverage in some areas.


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             As shown in Figure 4, the bar chart compares the RRC establishment success rates of
             various main scenarios. It can be seen from the examples in the figure that the called
             voice service has the highest RRC establishment success rate while the calling voice
             has the lowest success rate (which corresponds to a large amount of UENoRsp
             analyzed earlier). The RRC establishment success rate of registration is also relatively
             low. In Huawei networks, the present resident threshold is Ec/Io greater than -18 dB.
             The intersystem reselecting starting threshold is Ec/Io less than -14 dB. A low
             registration success rate indicates that some terminals have attempted to register at a
             network in the areas without good coverage (Ec/Io is between -14 dB and -18 dB). The
             called RRC establishment success rate is as high as 99.3%. If the called party starts
             RRC establishment, it indicates that he is covered by a PCH. From another point of
             view, this indicates that the RRC establishment success rate of expected network
             coverage area may be very high.
             3. Analysis of RRC establishment rejection
             Another cause of RRC establishment failure is RRC establishment rejection. In the
             case of RRC establishment rejection, generally too many users lead to admission
             rejection, or cell equipment fault leads to access failure. RRC establishment rejection
             always corresponds to some areas instead of a large network area. RRC
             establishment rejection is generally analyzed based on problematic areas. In the
             query results of RRC Setup Analysis, start related query to make TOPN query of Cell
             RRC Analysis. Query results cover two pages, which respectively list 10 cells with the
             most VS.RRC.FailConnEstab.Cell and VS.RRC.SuccConnEstab.Rate.Cell. For the 10
             cells with the most RRC establishment failures and the cells with the most Rej, start
             Cell RRC Reject Analysis of related query to analyze the causes for rejection.




             Figure 5 Analyzing the cause of RRC rejection



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             According to the results of Cell RRC Reject Analysis, draw a pie chart of cause
             distribution for a selected cell. Figure 5 is an exemplified pie chart of cause distribution
             of RRC rejection. In this example, two RRC rejections of a cell are because of Power
             Congestion. The following shows the commonly seen causes of rejection:
             1)   Power Congestion: RRM makes an admission algorithm decision. Downlink
                  admission decision occurs. Therefore, RRM starts RRC establishment rejection.
                  This often occurs when heavy network load leads to congestion. Further, we may
                  start Cell Traffic Load Analysis of related query, pay much attention to the
                  maximum RTWP and the maximum TCP of this cell and make sure whether there
                  is uplink congestion or downlink congestion. For congestion, we may check
                  whether a threshold is properly set and judge whether there is any radio
                  interference, whether expansion is necessary.
             2)   CE Congestion: This is mainly because RNC considers CE resource insufficient.
                  CE congestion always corresponds to many users. These users exceed CE
                  capacity and we need to expand the capacity of this area. Further, we may start
                  Cell Traffic Load Analysis of related query, know about the quantity of DCH User
                  and predict the required CEs according to the traffic model.
             3)   RL Fail: During RRC establishment, NodeB considers establishment fails. This
                  may be NodeB fault or insufficient NodeB resource. Further, we may start Cell
                  Traffic Load Analysis of related query and know about the quantity of DCH users.
                  Determine whether the problem lies in insufficient resource or equipment fault by
                  analyzing the board configuration, CE configuration and logs of a corresponding
                  NodeB.
             4)   AAL2 Fail: This is mainly the AAL2 Path establishment failure of an Iub interface.
                  It is generally caused by insufficient transmission resource or transmission
                  problems. Further, we may start Cell Traffic Load Analysis of related query, know
                  about the quantity of DCH users and compare it with the AAL2 Path bandwidth of
                  transmission configuration. Thus, we can determine whether the problem lies in
                  equipment or insufficient transmission resource.
             5)   Redir.Inter.Att: Inter-frequency redirection failure starts rejection.
             6)   Redir.Intrat: Foreign redirection failure starts rejection.
             7)   Code Congestion: This is mainly because of insufficient resource. Insufficient
                  code resource may be seen in high traffic scenarios with microcell coverage, and
                  expansion is necessary. Cell OVSF Code Allocation Analysis of related query
                  helps analyze the use of channel codes and clarify main services.
             8)   Other: This is mainly an RNC internal processing problem. Its cause needs to be
                  confirmed according to R&D logs.

1.3 Summary
             Make a similar analysis of several other special topics according to the
             above-mentioned idea of the RRC connection analysis. Keep summarizing
             experiences in your analysis. Special topic analysis will help greatly improve basic
             skills of performance analysis.


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             Basic special topic analysis practice contributes to the following aspects:
             1)   Consolidate signaling flow and deepen an understanding of each UTRAN PI.
                  Performance analysis has a more definite object in view.
             2)   Basic special topic analysis enables us to make a preliminary analysis of network
                  performance and locate simple problem causes.
             3)   Summarize the relationship between performance KPIs and network problems,
                  and lay a foundation for the use of other Nastar functions and an in-depth
                  analysis of network performance.




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