3G Optimization Guidelines
1
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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)
2)
3)
4)
5)
6)
7)
8)
RRC establishment analysis observation point
RAB establishment analysis observation point
Soft handover analysis observation point
Call drop analysis observation point
CS/PS intersystem handover analysis observation point
Traffic analysis observation point
Key interface process analysis observation point
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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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
Point
Categories of
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Condition
Observe various
Possible
Analysis Idea
Cause
If there are many streaming class called
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Observation
Point
Condition
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Possible
Analysis Idea
Cause
RRC
types of RRC
establishment connection
requests
establishment
requests and
their proportional
distribution. If any
abnormality, we
need to give an
early warning.
service requests (accounting for over 10%
of total connection establishment
requests), we need to pay much attention
to them. This is because when UE changes
from DCH status into IDLE status, PS
needs to transmit packets, then ps paging
occurs and the corresponding RRC
requests are streaming class called service
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
AAL2
establishment
failure
transmission resource or transmission
fault. You may query the cell downlink
throughput at the moment from associated
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
Number of RRC
RL
establishment
failure
connection
establishment
RRC
failures (>=5);
establishment
RRC connection
failure
establishment
failure rate
(>=10%)
query the maximum downlink CE of a cell
from associated traffic statistics index. If
the maximum uplink CE is less than 20,
then traffic is not high and the problem lies
in abnormal NodeB equipment.
RRM admission decision cannot establish
any new RRC connection due to too high
Power
congestion
radio load within a cell. In this case, you
need to query the maximum RTWP and the
maximum TCP of the cell to confirm uplink
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
congestion
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within an RNC. You need to query the
number of uplink CEs of a cell from
relevant parameters and judge whether to
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Observation
Point
Condition
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Possible
Analysis Idea
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
Downlink CE
congestion
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.
Code resource fails to be allocated during
RRC connection establishment. Code
Code
congestion
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congestion is generally caused by too
many network users. It may be seen in high
traffic scenarios with microcell coverage.
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
leads to RRC
unknown insufficient resources. For
example, license resource and high CPU
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Observation
Point
Condition
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Possible
Analysis Idea
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
Transmission
congestion
from associated traffic statistics indexes. If
the downlink cell throughput is lower than
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
Other factors
lead to RRC
rejection.
in-depth location based on RNC logs. The
known problem is that the system
redirection function of the network is
enabled. During redirection, a mobile
phone does not support GSM and thus
failure rejection occurs.
No response
from UE
This is generally caused by poor coverage.
The downlink FACH and RACH have
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.
Other factors
lead to RRC
establishment
failure.
There was a problem with the designated
access DSP of node B. The RRC
CONNECTION SETUP REQUEST
message fails to be sent to RNC. The
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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1.1.2 RAB Establishment Analysis Observation Point
Table 2 RAB establishment observation point
Observation
Point
Condition
Possible
Cause
Analysis Idea
Generally transmission equipment fault or
Transmission
network
insufficient transmission capacity. You
need to query the transmission utilization of
that time.
In starting migration, RNC receives a RAB
Migration
establishment request, but does not
process it. This is mainly caused by flow
nesting and seldom occurs. It is related to
user behavior sequence. This is generally
avoided in a core network.
RRM admission decision cannot establish
Number of
CS/PS RAB
establishment
failures (>=5);
establishment
CS/PS RAB
failure
establishment
failure rate
(>=10%)
Power
congestion
CS/PS RAB
any new RRC connection due to too high
radio load within a cell. In this case, you
need to query the maximum RTWP and the
maximum TCP of the cell to make sure of
uplink 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
within an RNC. You need to query the
number of uplink CEs of a cell from
Uplink CE
congestion
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
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.
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Observation
Point
Condition
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Possible
Cause
Analysis Idea
Downlink CE resource admission
congestion within an RNC. You need to
query the number of downlink CEs of a cell
Downlink CE
congestion
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
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.
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
congestion
traffic scenarios with microcell coverage.
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
Transmission
congestion
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by insufficient transmission resource. You
may query the downlink cell throughput
from associated traffic statistics indexes. If
the downlink cell throughput is lower than
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.
Others
Abnormal causes. We need to make an
in-depth location based on RNC logs.
Air interface
The air interface failure occurring during
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Observation
Point
Condition
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Possible
Cause
failure
Analysis Idea
RB establishment is generally caused by
poor coverage or mobile phone
compatibility.
The compatibility of a mobile phone itself
becomes faulty in some unknown
Configuration
not supported
scenarios. For example, when a Huawei
mobile phone drops network abnormally, it
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
Physical
channel failure
Cell update
to DCH and sets up RB. The downlink
physical layer of a terminal is not
synchronized, which leads to RB
establishment failure. This is mainly caused
by poor coverage.
The Cell Update flow occurs during RB
establishment. This nested flow leads to
RB establishment failure.
UE considers parameter configuration
illegal. Network and terminals have an
inconsistent understanding of parameter
Illegal
configuration
No response
from UE
processing. If RB establishment failure
occurs in the domain of CS, it is possible
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.
Generally poor coverage makes UE unable
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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Observation
Point
Condition
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Possible
Cause
Analysis Idea
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
Point
Condition
Possible
Cause
Analysis Idea
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
RAB
preemption
causes a link to be released. This kind of
call drop occurs in the case of load and
insufficient resource. Determine whether
expansion is necessary according to the
number of occurrences.
Within a cell, UTRAN leads to abnormal
CS/PS call
drop
High CS/PS call
drop rate
UTRAN
link release. This case generally
corresponds to processing abnormality. We
need to make a further analysis by means
of CDL.
Uplink or downlink signaling RB reaches
the maximum retransmission times and
Uplink/downlink
RLC reset
Uplink
synchronization
failure
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resets. This causes a link to be released.
This case is mainly caused by poor
coverage quality (including missing
configuration of adjacent cells and small
handover area).
RNC receives RL Failure reported by
NodeB, which causes a link to be
abnormally released. In this case, poor
coverage quality (including missing
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Observation
Point
Condition
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Possible
Cause
Analysis Idea
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
Downlink
synchronization
failure
by a mobile phone. The cause is downlink
RL Failure, which makes a link abnormally
released. In this case, poor coverage
quality (including missing configuration of
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.
Other RF
causes
out and waiting for active set update
completion times out. This case is
generally caused by poor coverage.
RF cause; due to poor coverage quality
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
GTPU
interface is abnormal and starts abnormal
release. The cause may be equipment fault
or defect.
Possibly the call drop (but traffic statistics
Others
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does not dot) occurring during flow
interaction or cell update, or abnormal call
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Observation
Point
Condition
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Possible
Cause
Analysis Idea
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
Point
Condition
Possible
Analysis Idea
Cause
Possible causes of too high (>= 40%) a
soft handover rate:
1)
Handover parameter setting makes
addition easy, but deletion difficult.
2)
In the early days of network
Soft handover
Soft
handover
rate
rate based on
cell resource
allocation and
soft handover
rate based on
IUB transmission
resource
allocation.
construction, there are few base
stations and insufficient coverage.
Therefore, capacity gives way to
quality.
3)
The CN side of some partners does
not deliver Iu release. After a user’s
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
Soft
handover
execution
failure
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Configuration
soft/softer
handover failures not supported
(>=5) and
soft/softer
Synchronization
handover failure reconfiguration
UE considers that the content of the active
set update of RNC adding/deleting a link is
not supported. Generally, this scenario will
not appear in commercial use.
UE gives the feedback that the softer/soft
handover process of RNC adding/deleting
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Observation
Point
Condition
rate (>=10%)
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Possible
Analysis Idea
Cause
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
set update of RNC adding/deleting a link is
Illegal
configuration
illegal. Generally, this scenario will not
appear in commercial use..
RNC does not receive the active set
No response
from UE
update command response for
adding/deleting a link. This is the main
cause of softer/soft handover failure. This
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
Point
Condition
Possible Cause
Analysis Idea
Preparation
Hard
handover
preparation
failure
failures (>=5) of
hard handover
into this cell and
preparation
failure rate
(>=10%) of hard
handover into
this cell
Radio link establishment failure occurs
during RL establishment. For details, see
the RL establishment process analysis of
the IUB interface.
For other causes, we need to make a
further analysis based on RNC logs.
Preparation
Preparation
A target cell has
failure of
transition out
of cell
accompanied
failures (>=5) of
transition out of
cell accompanied
by hard handover
no wireless
network
resource
available.
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A target cell has no resource available, or
there is some RNC parameter
configuration error. We need to make an
analysis based on RNC logs.
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Observation
Point
by hard
handover
Condition
and preparation
failure rate
(>=10%) of
transition out of
cell accompanied
by hard handover
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Possible Cause
Analysis Idea
Transition
timeout of target
The problem often lies in CN parameter
configuration or a related link connection.
We need to make an analysis based on
system
Transition failure
It generally corresponds to core network
in the target
CN/RNC or
configuration error.
system
Transition in the
target CN/RNC
or system not
supported
Often an MSC parameter configuration
objective not
allowed
error. We need to check the parameter
configuration of a core network.
OM intervention
Failure caused by operation and
maintenance
No available
resource
Often an MSC parameter is configured
incorrectly, or a target RNC has no
resource available.
A core network does not return a
Waiting for
transition
command
timeout
preparation
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statistics.
RNC logs.
Preparation
outgoing
handover
Failure causes are not defined in traffic
We need to make an analysis based on
Others
failures (>=5) of
RNC-level
CS/PS domain
intersystem
outgoing
handover,
Generally, RNC does not support some
hard handover parameters. We need to
make an analysis based on RNC logs.
Transition
Undefined
Preparation
failure of
RNC-level
foreign
RNC logs.
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corresponding command of handover
preparation request. In this case, there is
some problem with the parameter
configuration or related link connection of
a core network. We need to analyze the
cause according to the signaling trace of
the core network and BSS.
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Observation
Point
Condition
failure rate
(>=10%)of CS
domain
intersystem
outgoing
handover
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Possible Cause
Analysis Idea
Upon requesting handover preparation,
RNC receives the release command from
a core network. Two cases: intersystem
Transition
cancelled
Transition
timeout
Transition failure
in the target
CN/RNC or
system
Unknown target
RNC
No available
resource
handover request occurs during signaling
process like location update. The location
update flow has been finished before one
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
configuration error. We need to analyze
the cause according to the signaling
tracing of a core network and a BSS.
The problem often lies in the parameter
configuration or related link connection of
a core network. We need to analyze the
cause according to the signaling tracing of
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
configured. We need to check the
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 resource available. We need to analyze
the cause according to the signaling
tracing of a core network and a BSS.
We need to analyze the cause according
Others
2010-01-31
to the signaling tracing of a core network
and a BSS.
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Observation
Point
Condition
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Possible Cause
Transition
Preparation
Preparation
failure of
Cell-level
foreign
outgoing
handover
Outgoing
hard
handover
failures within
NODE B,
between
different
NodeBs
within RNC,
failures (>=5) of
CELL-level CS
domain
intersystem
outgoing
handover and
preparation
failure rate
(>=10%) of CS
domain
intersystem
outgoing
handover.
Failures (>=5) of
hard handover
out of a cell,
failure rate
(>=10%) of hard
handover out of a
cell
timeout
The problem often lies in the parameter
configuration or related link connection of
a core network. We need to analyze the
cause according to the signaling tracing of
a core network and a BSS.
It generally corresponds to core network
Transition failure
configuration error or BSS not supporting.
in the target
We need to analyze the cause according
CN/RNC or
to the signaling tracing of a core network
system
and a BSS.
Transition in the
In this case, a BSC does not support some
target CN/RNC
or system not
supported
parameters of intersystem handover
requests. We need to analyze the cause
according to the signaling tracing of a core
network and a BSS.
Others
We need to analyze the cause according
to the signaling tracing of a core network
and a BSS.
Configuration
not supported
UE considers that the command for hard
handover out of a cell is not supported.
The problem generally lies in the
compatibility of a mobile phone.
Physical channel Possibly poor coverage or severe
failure
interference
Synchronization
reconfiguration
not supported
UE gives the feedback that hard handover
process is incompatible with other
concurrent processes. The problem may
lie in the compatibility of a mobile phone
itself.
Cell Updating
Procedure
Cell update happens during hard
handover out of a cell. This flow nesting
leads to the failure of hard handover out of
a cell.
and between
RNCs
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Analysis Idea
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Observation
Point
Condition
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Possible Cause
Illegal
configuration
Analysis Idea
UE considers that the command for hard
handover out of a cell is illegal. The
problem generally lies in the compatibility
of a mobile phone.
We need to make a further analysis based
on RNC logs.
Others
UE considers that the command for
Configuration
not supported
Execution
Failure of
transition out
of a cell
accompanied
by hard
handover
transition out of a cell accompanied by
hard handover is not supported. The
problem generally lies in the compatibility
of a mobile phone.
Physical channel Possibly poor coverage or severe
failure
interference
failures (>=5) of
transition out of a
cell accompanied Synchronization
by hard
reconfiguration
handover,
incompatible
execution failure
rate (>=10%) of
transition out of a
cell accompanied Illegal
by hard handover configuration
UE gives the feedback that the hard
handover process of RNC adding a link is
incompatible with other concurrent
processes. The problem may lie in the
compatibility of a mobile phone itself.
UE considers that the command for
transition out of a cell accompanied by
hard handover is illegal. This case seldom
occurs.
Configuration
not finished
We need to make a further analysis based
on RNC logs.
Others
CS/PS
foreign
handover
failure
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CS/PS domain
Configuration
intersystem
handover failures not supported
(>=5), CS/PS
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The handover command terminal in a
network does not provide support. The
problem generally lies in the compatibility
of a mobile phone.
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Observation
Point
Condition
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Possible Cause
domain
intersystem
handover failure
rate (>=10%)
Physical channel
failure
Analysis Idea
1)
Poor 2 G signal or severe interference
leads to UE access failure.
2)
The channel parameters, including
the encryption mode sent from
network to UE, are inconsistent with
those of a BSC. We need to compare
and confirm the parameters of a
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
configuration of 2 G cell makes high-rate
service unable to start a pressing mould,
Others
which leads to system PS handover
failure.
1.1.6 Traffic Analysis Observation Point
Table 6 Traffic analysis observation point
Observation
Point
Condition
Analysis Idea
Lay an emphasis upon
Uplink CE
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the analysis of “average
uplink CE resource
occupied” and “the
maximum uplink CE
resource occupied”.
Observe whether “the maximum uplink CE
resource occupied” approaches 128. If it does, an
early warning needs to be given to expansion.
Normally, when the “average uplink CE resource
occupied” is less than 60 CE Erlang,
whole-network busiest-hour cell traffic is very
small.
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Observation
Point
Downlink CE
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Condition
Analysis Idea
Lay an emphasis upon
the analysis of “average
downlink CE resource
Observe whether “the maximum downlink CE
resource occupied” approaches 128. If it does, an
early warning needs to be given to expansion.
Normally, when the “average downlink CE
occupied” and “the
maximum downlink CE
resource occupied”
resource occupied” is less than 60 CE Erlang,
whole-network busiest-hour cell traffic is very
small.
List the average TCP,
Average transmit the maximum TCP and
power of cell
the minimum TCP of a
cell.
Maximum
List the average TCP,
the maximum TCP and
transmit power of
the minimum TCP of a
cell
cell.
Minimum
Observe whether the
transmit power of minimum transmit power
cell
of a cell is abnormal.
Average RTWP
If the maximum transmit power of a cell is large
and there is small traffic, it indicates that power
peak shock may lead to power congestion.
If the minimum transmit power of a cell is
abnormal, the transmit channel may become
faulty.
List the average RTWP,
the maximum RTWP,
If the average RTWP of a cell is higher than -95
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
are many peaks.
-70 dBm, often appear. This may be caused by the
power of access process or handover process.
Minimum RTWP
Observe whether the
minimum RTWP is less
than -105.5 dBm.
Effective
utilization of
codes
Observe whether the
code utilization is
abnormal.
Uplink
Observe the uplink
throughput of cell throughput of a cell.
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If the average transmit power of a cell is large and
there is small traffic, it indicates that there is poor
downlink coverage.
If the minimum RTWP is lower than -108 dBm, a
channel fails to be corrected, or a base station
encounters power-down.
If the effective utilization of codes is not high (<=
30%), but code congestion leads to access failure,
it is possible that the code distribution algorithm is
abnormal.
Observe whether the uplink throughput of a cell is
great. If it amounts to 75% of the transmission
capability of a base station, transmission
expansion needs to be considered.
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Observation
Point
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Condition
Analysis Idea
Observe whether the downlink throughput of a cell
is great. If it amounts to 75% of the transmission
capability of a base station, transmission
expansion needs to be considered..
Downlink
Observe the downlink
throughput of cell throughput of a cell.
This is generally caused by transmission
Cell status
monitoring
Missing
configuration of
adjacent cell
List the cell unavailability
duration and its
proportion.
List the number of cell
1A events.
interruption or intermittent transmission failure.
Some offices are greatly influenced by weather
due to the use of microwave transmission.
Thunder storm always leads to intermittent
transmission failure.
If 1A events often happen within many
consecutive days, there may be missing
configuration of adjacent cells.
Excess
configuration of
adjacent cells
Pilot Pollution:
List the number of cell
1C events.
If 1C events often happen within many
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
Point
Security mode
flow failure
Condition
IU security mode
failures, IU
security mode
failure rate
Possible
Cause
Analysis Idea
Radio
network layer
The problem may lie in the compatibility
of a mobile phone. A mobile phone
terminal may detect the SQN error of in
an AUTN message, which leads to
failure. Cause value: Synch failure!
Respective encryption modes of CS
domain and PS domain may also lead to
a security mode failure.
Transmission
layer
Correspond to transmission link
abnormality.
Network
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Observation
Point
Condition
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Possible
Cause
Analysis Idea
optimization
Undefined
RL
establishment
failure of the IUR
interface
RL
synchronization
configuration
failure of the IUR
interface
RL addition
failure of the IUR
interface
RL
establishment
failure of the
IUB interface RL
reconfiguration
failure of the IUB
interface
RL addition
failure of the IUB
interface
OM
RL failure of IUR interface caused by
intervention
operation and maintenance
Hardware
failure
This generally corresponds to equipment
abnormality. We should first query
related equipment alarm.
List the number of
RL establishment
failures (>= 5) of
RNC resource
the Iur interface of unavailable
the SRNC, RL
establishment
failure rate (>=
This is caused by insufficient RNC
internal resource. You need to query the
quantity of related users to judge
10%) of the Iur
interface of the
SRNC, and main
failure causes.
content of RNC establishment is not
supported. The problem lies in the
compatibility of a mobile phone.
Configuration
not supported
whether there is any equipment
abnormality.
UE considers that the RL configuration
Others
Abnormal causes. We need to make an
analysis based on RNC logs.
No response
This generally corresponds to equipment
abnormality. We need to query whether
there is any power-down.
Configuration
not supported
The problem lies in the compatibility of a
mobile phone itself in some unknown
scenarios.
List the number of
RL establishment
failures of the IUB
interface, RL
establishment
failure rate of the No available
Iub interface, and resource
main failure
causes.
Insufficient RNC internal resource or
abnormal RNC equipment. You need to
query cell CE resource from relevant
parameters to judge whether there is any
equipment abnormality. Equipment is
known to encounter repeated power
failure and air-conditioner fault due to
thunder storm. As a result, high
temperature leads to abnormality of
various kinds. Besides, the NLPA board
encounters shutdown.
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Observation
Point
Condition
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Possible
Analysis Idea
Cause
Equipment
fault
This generally corresponds to equipment
abnormality. We should first query
related equipment alarm.
OM
RL establishment failure caused by
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
Others
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
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
establishment
failure
RB
reconfiguration
failure
RB deletion
failure
RB establishment
failure generally
corresponds to
poor air interface
coverage or a
mobile phone
compatibility
problem.
Configuration
not supported
mobile phone itself in some unknown
scenarios. For example, when a Huawei
mobile phone drops network abnormally,
it may not release any RB. When PS RB
is reestablished next time, this case may
occur. This case also happens to SE
V800 mobile phone. Or when some UEs
implement VP and high-speed (greater
than or equal to 64K) PS service, failure
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Observation
Point
Condition
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Possible
Cause
Analysis Idea
may also due to unsupported capability.
Physical
channel
failure
This generally occurs when FACH
migrates to DCH and establishes RB.
The downlink physical layer of a terminal
is not 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
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
configuration
resides in a GSM network and does not
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.
No response
from UE
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Generally poor coverage makes UE
unable to receive any RB command. In
Hong Kong, the balance mechanism of
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
Point
Condition
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Possible
Analysis Idea
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
various types of
distribution of
RB service bearer
uplink/downlink
and the
service
proportion are
Uplink/downlink
abnormal. If there
RB bearer
is any
distribution of BE
abnormality, an
service
early warning
needs to be given
and 384k RB bearer. This will consume a
large number of resources and there is
poor coverage. We need to verify
whether RB bearer is consistent with
actual demands with first-line personnel.
Observe whether the RB distribution of
BE service is rational. According to the
distribution, DCCC strategy and related
system parameters can be adjusted.
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)
3)
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.
RL Fail: During RRC establishment, NodeB considers establishment fails. This
4)
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.
AAL2 Fail: This is mainly the AAL2 Path establishment failure of an Iub interface.
5)
6)
7)
8)
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.
Redir.Inter.Att: Inter-frequency redirection failure starts rejection.
Redir.Intrat: Foreign redirection failure starts rejection.
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.
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)
2)
3)
Consolidate signaling flow and deepen an understanding of each UTRAN PI.
Performance analysis has a more definite object in view.
Basic special topic analysis enables us to make a preliminary analysis of network
performance and locate simple problem causes.
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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