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www.huawei.com
Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
GPRS Traffic Statistics
Page 2Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 2
Objectives
� GPRS traffic measurement indicates the basic performance of the
GPRS.
� Each traffic measurement item indicates the features of the
network.
� Traffic measurement helps to quickly handle the network problems.
� A complete performance measurement system is provided for the
network performance analysis, network optimization, and fault
location of the GPRS network.
2
Page 3Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 3
Contents
1. GPRS Traffic Structure
2. GPRS Traffic Analysis
Page 4Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 4
GPRS Traffic Statistics Introduction� GPRS performance measurement involves the CPU performance, Um
interface performance, Pb interface performance, and PCU overall
performance. The GPRS performance measurement provides data
support for the GPRS performance familiarity, GPRS optimization, and
fault location.
� GPRS counters can be categorized into:
� Service model establishment
� Network performance optimization
� Troubleshooting
3
Page 5Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 5
There are 7 kinds of measure type :
� BSC Overall Performance Measurement
� BSSGP Performance Measurement
� CPU Performance Measurement
� G-Abis Interface Performance Measurement
� NS Performance Measurement
� Pb Interface Performance Measurement
� Cell Performance Measurement
GPRS Traffic Statistics Introduction
Page 6Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 6
� The BSC overall performance analysis include:
� Traffic load model: Number of Uplink TBF Establishment Attempts and Number of Downlink TBF Establishment Attempts;
� GPRS output: Total Number of Uplink LLC_PDUs Sent, Total Bytes of Uplink LLC_PDUs Sent, Total Number of Downlink LLC_PDUsReceived and Total Bytes of Downlink LLC_PDUs Received;
� Paging load: Number of Circuit Paging Requests Sent and Number of Packet Paging Requests Sent;
� Packet channel resource: Mean Number of Available PDCHs and Mean Number of Occupied PDCHs.
BSC Overall Performance Measurement
4
Page 7Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 7
� The BSC overall performance analysis is to check the overall running state of the BSS. The results of the measurement are used to Analyze the QoS of GPRS BSS.
� If the measurement result exceeds the reference range, the radioenvironment, network parameter configuration, network resource configuration and network equipment should be optimized, such asNumber of Successful Uplink TBF Establishment, Number of Successful Downlink TBF Establishment, Number of Uplink TBF Normal Release and Number of Downlink TBF Normal Release.
BSC Overall Performance Measurement
Page 8Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 8
� The object of the measurement is board, which includes POMU and RPPU.
� It measure the load of cpu
� the value of average CPU occupancy is too high: Check whether the operations such as FTP, performance measurement task register and file operating are being implemented.
CPU Performance Measurement
5
Page 9Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 9
� Cell Performance Measurement focus on RLC/MAC layer performance:
such as access performance, TBF establishment and release
measurement, PDCH resource measurement
Cell Performance Measurement
Page 10Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 10
Uplink RLC Data Transmission Measurement
10
Downlink LLC Data Transmission Measurement
9
Uplink LLC Data Transmission Measurement
8
Downlink TBF Establishment/Release Measurement
7
Uplink TBF Establishment/Release Measurement
6
Paging Request Measurement5
Rate of Successful Packet Assignment4
Packet Access Performance Measurement on PACCH
3
Packet Access Performance Measurement on PCCCH
2
Packet Access Performance Measurement on CCCH
1
Measurement itemNo.
EGPRS 8PSK_MEAN_BEP Different Value Measurement
21
EGPRS GMSK_MEAN_BEP Different Value Measurement
20
Downlink EGPRS RLC Data Transmission Measurement
19
Uplink EGPRS RLC Data Transmission Measurement
18
Downlink EGPRS TBF Establishment/Release Measurement
17
Uplink EGPRS TBF Establishment/Release Measurement
16
PDCH Extreme Value Measurement15
PDCH Resource Performance Measurement 14
Resource Maintenance Performance Measurement
13
Cell Radio Channel Performance Measurement12
Downlink RLC Data Transmission Measurement11
Cell Performance Management
6
Page 11Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 11
� NS Performance Measurement:
� Analyze the traffic load of GPRS BSS.
� Monitor the service of NS layer of Gb interface
� BSSGP performance measurement The object of the measurement is cell The results of the measurement are used to create traffic model
� G-Abis Interface Performance Measurement indicate the performance of G-Abis transmission.
� Pb Interface Performance Measurement, The object of the measurement is LAPD. The initial items can be used to reflect the performance of Pbinterface, and they are also helpful for troubleshooting of the GPRS network. Please refer to the analysis and application part of each item for the detailed usage.
GPRS Traffic Statistics Introduction
Page 12Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 12
Contents
1. GPRS Traffic Structure
2. GPRS Traffic Analysis
7
Page 13Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 13
GPRS Traffic Analysis ProcessStart
Regular analysis of traffic data
Whether the trafficdata is faulty? Locate the fault
Whether the trafficstatistical item is faulty?
BSC overall analysis
Traffic modelaccumulationand analysis
Whether the BSCitem is faulty?
Faulty occurs
Checklist
Analyze the BSC traffic data
Locate the abnormal cell
Analyze the cell traffic data
Analyzetransmission link
Analyzecongestion rate
Analyze cell-drop rate
Solve theequipment fault
Solve thetransmission
fault
optimize thenetwork
End
Yes
No
No
Yes
Yes
No
Page 14Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 14
BSC Overall Performance Analysis
� In the current GPRS network, the cell handover is unavailable and the MS
reselects a cell totally by itself. If cell reselection is performed during
transmission, call drop occurs inevitably. However, the TBF transmission
time is short (2 to 3 seconds), the impact on services is relatively small
although the call drop rate in the GPRS system is higher than that in the
speech system.
� If the call drop rate is high, need to check the traffic measurement data of
cells in the suspicious period of time and find the cells with extremely high
call drop rate. Locate the faults (the common case is faulty cell channel
status and network optimization problems) and rectify them. For details,
refer to the check of the retain ability KPIs of cells.
8
Page 15Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 15
� Resource utilization KPIs are used to analyze the PDCH data to check
whether the system is overloaded.
� The PDCH is of two types: dynamic PDCH and static PDCH. One RPPU
of the PCU supports a maximum of 120 available PDCHs (if upgraded to
EDGE, the maximum number of available PDCHs decreases).
Resource Utilization Analysis
Page 16Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 16
Pb Interface Link Analysis
� The Pb interface is the signaling interface between the PCU and the BSC.
� As a semi-dependent device, the PCU can connect multiple BSCs. The
communication between the PCU and the BSC is realized through
transmission devices or even long distance transmission devices.
� The LAPD traffic measurement data indicates the transmission quality of
the Pb interface and the basic conditions of high-layer data.
9
Page 17Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 17
� LAPD performance counters include the following:
� Number of SABM frames sent
� Number of message retransmissions
� You can determine the stability of links by checking the number of
message retransmissions.
Pb Interface Link Analysis
Page 18Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 18
Cell-level Performance Analysis
� In the cell-level performance analysis, the KPIs of the following four
aspects should be checked:
� Transmission performance
� Access performance
� Resource utilization
� Retain ability
10
Page 19Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 19
Transmission Performance Analysis� The transmission path between the MS and the GPRS core
network is called the transmission link of the cell. It includes the
Um interface, G-Abis interface, Pb interface, and Gb interface.
� Um interface analysis
� Abnormality rate of N3101, N3103, and N3105 (talked together
with call drop later)
� Retransmission rate of RLC uplink and downlink data block and
the number of CS upgrade and demolition
� G-Abis interface analysis
� The TRAU Link Measurement in the G-Abis Interface Performance
Measurement is a cell-level measurement unit used for analysis of
transmission quality on the link layer.
Page 20Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 20
� For the GPRS network, if the retransmission rate is too high, the setting of
the initial coding scheme may be inappropriate. The retransmission rate
can be excessively high if a high rate is adopted for data transmission.
� Another possibility is that the setting of the coding rate adjustment
threshold in the CSPARA parameter table is inappropriate, and thus the
MS and the network cannot use the optimal coding scheme for
transmission.
� For the EDGE network, check the setting of the initial coding scheme (the
rate adjustment threshold for the EDGE network is fixed).
� If the data configuration is correct, you need to check whether there is
interference on the Um interface.
Um Interface Analysis ---retransmission and CS upgrade
11
Page 21Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 21
G-Abis Interface Analysis� TRAU Link Measurement includes three important counters:
Number of Out-of-Synchronization Frames Received, Number of
Check Error Frames Received, and Number of Normal Burst frames
Received. The check error frames are the transmission link check
error after channel synchronization. They directly indicate the link
quality.
00050
numberframenormalreceivednumberframeeerrorcheckreceived
rateerrorframeAbisG .≤=−
Page 22Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 22
Access Performance
12
Page 23Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 23
Assignment Success Rate
%100×=ABRateSuccessAssignmentUplink
A − Number of Uplink TBF Establishment Attempts
B − Number of Successful Uplink TBF Establishment
%100×=DCRateSuccessAssignmentDownlink
C − Number of Downlink TBF Establishment Attempts
D − Number of Successful Downlink TBF Establishment
Page 24Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 24
Uplink TBF Establishment Attempts� The mobile station initiates stage-1 access procedure by sending of
CHANNEL REQUEST messages on RACH. When the PCU receives this
message from MS, one time of Uplink TBF Establishment Attempt is
counted.
MS
A
CHANNEL REQUEST
NETWORK
13
Page 25Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 25
� The mobile station initiates stage-2 access procedure by sending of
CHANNEL REQUEST messages on RACH.
� When the PCU receives PACKET RESOURCE REQUEST message for
establishing uplink TBF from the MS, one time of Uplink TBF Establishment
Attempt is counted.
M S Network
A
RESOURCE REQUEST
PACKET UPLINK ASSIGNMENT
UPLINK DATA BLOCK
Uplink TBF Establishment Attempts
Page 26Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 26
� Uplink TBF establishment during a downlink TBF. The mobile station may
request establishment of an uplink transfer during a downlink TBF . A
Channel Request Description information element will be included in the
PACKET DOWNLINK ACK/NACK message.
� When the PCU receives the this message from the ACK/NACK from MS,
one time of Uplink TBF Establishment Attempt is counted.
Uplink TBF Establishment Attempts
M S Network
PACKET UPLINK ASSIGNMENT
UPLINK DATA BLOCK
A
Packet Downlink Ack/Nack
14
Page 27Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 27
M S Network
A
CHANNEL REQUEST
IMMEDIATE ASSIGNMENT
UPLINK DATA BLOCK
Uplink TBF Establishment Success� Uplink TBF will be successfully established in stage-1 access if uplink
data blocks on the PDCH assigned are received by PCU after it sent
IMMEDIATE ASSIGNMENT.
Page 28Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 28
M S Network
A
RESOURCE REQUEST
PACKET UPLINK ASSIGNMENT
UPLINK DATA BLOCK
Uplink TBF Establishment Success
� Uplink TBF will be successfully established in stage-2 access if uplink
data blocks on the PDCH assigned are received by PCU after it sent
Packet Uplink Assignment.
15
Page 29Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 29
M S Network
A
PACKET UPLINK ASSIGNMENT
UPLINK DATA BLOCK
Uplink TBF Establishment Success� Successful uplink TBF establishment on PACCH. Uplink TBF will be
successfully established on PACCH if uplink data blocks on the PDCH
assigned are received by PCU after it sent Packet Uplink Assignment.
Page 30Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 30
Assignment Success Rate Analysis
� Due to the speech service preferred and the data service features, the
assignment success rate of the GPRS network is usually higher than that
of the GSM network.
� If the assignment success rate is low, you need to check the traffic
measurement data of cells in the suspicious period of time. Usually, you
can find the cells with extremely high congestion rate. Locate the faults
and rectify them. For details, refer to the check of the radio access KPIs
of cells.
16
Page 31Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 31
� Check the counter Number of uplink/downlink TBF establishment failures
due to no channel. If the congestion rate is high because of these two
counters, the possible causes are as follows:
� The user manually blocks the channel or cell, leading to MS access
difficulties. Check the Number of BSC-originated channel blocking,
Number of BSC-originated cell blocking, and Number of Gb-originated
cell blocking in the Resource Maintenance Capability Measurement to
determine whether channels are blocked in the statistic period.
Access Performance –no channel available
Page 32Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 32
Access Performance –no channel available
� If no channels are blocked, the number of multiplexed packet channels
and MSs may reach the maximum value, leading to MS access
difficulties. Adjust MaxUlHighLd/MaxDlHighLd of the pdchpara table on
the PCU maintenance terminal to allow the cell to carry more PS
services.
� If you only adjust the maximum number of multiplexed MSs on the
channel, the transmission rate of the MS is affected. If the cell does not
have static PDCHs, configure a static PDCH. If the cell has static
PDCHs, add more dynamic PDCHs.
17
Page 33Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 33
Access Performance --no channel available
� When wide coverage is available, one RPPU[Pb] of the PCU may be
configured with more than 120 cells, When the PS services on the board
is busy, if the cell is configured with only dynamic channels the cell may
be congested because of insufficient channels.
� CCCH random access collision may affect the success rate of CCCH
uplink assignment. Analyze the cause together with the Mean Interval of
Packet Access Requests on CCCH (s).
� PDCH out-of-synchronization may also lead to insufficient PS resources
and assignment failure. If the PDCH out-of-synchronization alarm is
reported, check whether the links between the PCU and the BSC and
between the BTS and the BSC are normal.
Page 34Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 34
Access Performance –MS no response� The counter Number of Uplink/Downlink TBF Establishment Failures due
to MS No Response are the main cause of the low Assignment success
rate.
� The quality of the transmission links of the cell is poor and the block
BER is high.
� You can adjust the GPRS network parameters, such as T3168, to improve
the success rate of TBF access.
� If the traffic volume of PS services is high, the queue is long and the
assignment message delay is long, leading to TBF establishment
failure.
� If the traffic volume of PS services and the duration exceed the adjustment
capability of optimization, capacity expansion is recommended.
18
Page 35Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 35
Resource Utilization
� Through the measurement of PDCH seizure, you can obtain the
information about the preemption of the PS resources by the CS services.
� The counters that reflect the preemption of the CS services to the PS
services are Number of Dynamic PDCHs Reclaimed by BSC and Number
of Successful Conversions from TCH to PDTCH.
%100AB
RateSuccess Reclaimed TrafficPacket Carrying PDCH Dynamic Empted-Pre ×=
A − Number of Dynamic PDCHs Reclaimed by BSC
B − Number of Preempted PDCHs Carrying Packet Traffic
Page 36Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 36
Resource Utilization
� The PDCH utilization can reflect the traffic volume of the cell to some
extent. The relevant counters are Mean Number of Available PDCHs, Mean
Number of Occupied PDCHs, and Mean occupied Duration of All Available
PDCHs( s ).
� If the cell is configured with static channels, in normal conditions, the Mean
Number of Available PDCHs should be equal to or greater than the number
of static channels configured in the cell. Otherwise, the cell status is faulty
in the statistic period.
19
Page 37Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 37
Resource Utilization
� If all the channels configured in the cell are dynamic channels, you can
determine whether there is any request for the dynamic channel through
the two counters: Mean Number of Available PDCHs and Mean Number of
Occupied PDCHs.
� According to the Mean Number of Occupied PDCHs, you can determine
whether the PS services in the cell are busy or idle. Then you can adjust
the channel configuration according to the cell status. The idle cell shall be
configured with more dynamic channels and the busy cell can be
configured with more static channels.
Page 38Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 38
Resource Utilization
� The channel utilization rate considers the block utilization rate on the
PDCH both when the PCU is busy and when it is idle. Thus if the channel
utilization rate is low, the possible cause is that there is no PS service in
the cell or the traffic volume of the PS services is small.
� The uplink/downlink PDTCH/PACCH channel utilization can to some
extent reflect the traffic volume of the PS services in the current cell. The
relevant counters are as follows:
� Cell Mean PDCH Bearer Rate (%)
� Uplink PDTCH/PACCH Utilization Rate (%)
� Downlink PDTCH/PACCH Utilization Rate (%)
20
Page 39Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 39
Retain Ability –Drop Rate Analysis
Page 40Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 40
Drop Rate Analysis
( ) %100×=ABRateDropTBFGPRSUplink
A − Number of Successful Uplink TBF Establishment
B − Number of Uplink TBF Abnormal Release
( ) %100×=ABRateDropTBFGPRSDownlink
A − Number of Successful Downlink TBF Establishment
B − Number of Downlink TBF Abnormal Release
21
Page 41Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 41
Uplink TBF Normal Release
M S Network
A
PACKET UPLINK ACK/NACK FAI=1
PACKET CONTROL ACKNOWLEDGEMENT
� When the network receives the uplink RLC data block with CV=0, it will
send PACKET UPLINK ACK/NACK with FAI=1 to initiate uplink TBF
release procedure.
� When the uplink TBF is normally released, the network then will
receive the PACKET CONTROL ACKOWNLEDGEMENT from MS
Page 42Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 42
Abnormal Release Analysis � Poor transmission quality of the Um interface leads to the abnormal
release of the TBF and the increase of the TBF call drop rate.
� The counter Number of Uplink TBF Abnormal Release due to N3101
Overflow (Ms No Response) and the counter Number of Uplink TBF
Abnormal Release due to N3103 Overflow (Ms No Response) of the
Uplink TBF Establishment/Release Measurement refer to the number
of abnormal releases due to the poor quality of the Um interface. If the
values of the two counters are high, you need to check the quality of
the links on the Um interface.
22
Page 43Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 43
Abnormal Release Analysis � The counter Number of Downlink TBF Abnormal Release due to N3105
Overflow of Downlink TBF Establishment/Release Measurement refers
to the number of abnormal releases due to the poor quality of the links
on the Um interface. A high number of overflows indicates poor quality
of the downlink.
� Similar to the counters related to the GPRS TBF, the counters related
to the EGPRS TBF are used to measure the abnormal TBF releases
due to N3101, N3103, and N3105 overflows.
Page 44Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 44
Abnormal Release Due to N3101� This statistics item is used to measure the number of uplink TBF
abnormal releases due to overflow of the uplink monitoring counter
N3101.
Network schedule every uplink data block resource by allocating valid
USF for every MS which has accessed into the network, and attach the
USF information in every downlink block. N3101 will be increased by 1
every time no uplink data block is received on corresponding frame,
otherwise N3101 will be reset. The TBF will be released by network if
N3101 reaches the threshold.
23
Page 45Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 45
Abnormal Release Due to N3101
M S Network
A
RLC block(with USF valid)
RLC block (with USF valid)
NO RESPONSE FROM MS
N3101=N3101_MAX
� As the measurement point A referred in Figure , the number of uplink
TBF abnormal release due to N3101 overflow will be increased by one.
Page 46Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 46
Abnormal Release Due to N3103
� Network initiates uplink TBF release procedure by sending a PACKET
UPLINK ACK/NACK message with FAI=1, and wait MS reply PACKET
CONTROL ACKOWNLEDGEMENT message to release the uplink TBF
normally.
� N3103 will be incremented by 1 every time no expected message is
received on corresponding frame, otherwise N3103 will be reset.
� The TBF will be released by network if N3103 reaches the threshold.
24
Page 47Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 47
Abnormal Release Due to N3103
M S Network
A
PACKET UPLINK ACK/NACK(FAI=1)
NO RESPONSE FROM MS
N3103=N3103_MAX
PACKET UPLINK ACK/NACK(FAI=1)
� As the measurement point A referred in Figure below, the number of
uplink TBF abnormal release due to N3103 overflow will be increased
by one.
Page 48Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 48
Abnormal Release Due to N3105
� This statistics item is used to measure the number of TBF abnormal
releases due to overflow of the downlink monitoring counter N3105.
� Network will send the RLC data block with RRBP periodically to wait
response of PACKET DOWNLINK ACK/NACK message from MS.
N3105 will be increased by 1 every time no PACKET DOWNLINK
ACK/NACK is received on the same corresponding frame, otherwise
N3105 will be reset.
� The TBF will be released by network if N3105 reaches the threshold,
25
Page 49Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 49
MS Network
A
DOWNLINK DATA BLOCK (RRBP)
DOWNLINK DATA BLOCK (RRBP)
DOWNLINK DATA BLOCK (RRBP)
MS no response.....
Abnormal Release Due to N3105� As the measurement point A referred in Figure , the number of downlink
TBF abnormal release due to N3105 overflow will be increased by one.
Page 50Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 50
Call Drop Analysis� Determine whether the high TBF call drop rate is common for the entire
BSC or appears only in some sites or cells. If it appears only in some cells, check and troubleshoot the equipment based on the trafficmeasurement results.
� Check the equipment, including the BTS and PCU hardware. Then troubleshoot the transmission links, including the Um interface links, TRAU links, and Pb interface links. The equipment and transmission problems always cause alarms, which can be used for reference.
� The two counters Number of uplink/downlink TBF abnormal release due to no channel in the same statistic period can show that the TBF call drop is caused by the preemption of the PS resources by the CS services.
26
Page 51Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 51
Call Drop Analysis� Number of uplink/downlink TBF abnormal release due to SUSPEND
shows the impact of the CS services on the PS services, for example, a
call or location updating is initiated when the PS services are performed.
� If cell reselection is initiated when the PS services are performed, the
TBF is abnormally released. According to Number of uplink/downlink
TBF abnormal release due to FLUSH, together with Number of Times a
Cell Is Selected by MS, Number of Cell Reselections by MS at Short
Interval, and Number of Cell Ping-Pong Reselections by MS, check
whether the ping-pong reselections occur.
Page 52Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 52
Call Drop Analysis � Pay attention to the following condition: the values of Number of
uplink/downlink TBF abnormal release due to no channel are high, but the
value of Number of Preempted PDCHs Carrying Packet Traffic is 0. This
indicates that the abnormal release is not caused by CS preemption.
Check whether there are channels or cells blocked in the statistic period.
� If no channels or cells are blocked, check whether the transmission
resources of each interface incur faults or intermittent faults.
� If the transmission is normal, check the GPRS/EDGE TRXs. Locate the
implicit faults of TRXs through replacement or other methods.
27
Page 53Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 53
� In many networks, the GPRS/EDGE and the GSM share radio resources.
If the number of N3101, N3103, and N3105 overflows on the Um interface
is too high, some GSM counters can be used to troubleshoot the GPRS
network.
� The Interference Band Measurement and the cell frequency scan of the
GSM network can be used to locate the uplink interference.
� The TCHF/TCHH Receive Level Measurement of the GSM network is
used to measure the MRs received in a statistic period with different
receive levels and receive quality ranks. The measurement results
indicate the distribution of uplink/downlink receive level and receive quality
by ranks.
Optimization of Call Drop
Page 54Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 54
Other Often-used Items� EGPRS 8PSK_MEAN_BEP Different Value Measurement: This item is
used to measure the number of EGPRS PACKET DOWNLINK
ACK/NACK messages carrying EGPRS BEP Link Quality
Measurements with 8PSK_MEAN_BEP = 1 to 31 received by BSS.
The items can be used to reveal the traffic load of the cell and thus
help to create the traffic model.
MS Network
A
EGPRS PACKET DOWNLINK ACK/NACK(8PSK_MEAN_BEP=1)
28
Page 55Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 55
Other Often-used Items
Times of 8MSK_MEAN_BEP=3131
Times of 8MSK_MEAN_BEP=3030
Times of 8MSK_MEAN_BEP=2929
Times of 8MSK_MEAN_BEP=2828
Times of 8MSK_MEAN_BEP=55
Times of 8MSK _MEAN_BEP=44
Times of 8MSK_MEAN_BEP=33
Times of 8MSK_MEAN_BEP=22
Times of 8PSK_MEAN_BEP=11
Measurement itemNo.
Page 56Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 56
Other Often-used Items� Cell reselection is of key importance to the GPRS network performance.
There are relevant counters monitoring ping-pong reselection and
network-controlled cell reselection (NC2)
� Number of Cell Reselections by MS at Short Interval: This counter is
used to measure the total number of times that the duration between
the MS switches into and out of the cell is less than the specified
time (20 seconds by default).
� Number of Cell Ping-Pong Reselections by MS: This counter is used
to measure the number of times that the MS switches from cell A to
cell B and then switches back to cell A at the predefined interval (20
seconds by default).
29
Page 57Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 57
Other Often-used Items� Number of Network Controlled Cell Reselection Attempts due to Downlink
Quality: This counter is used to measure the number of cell reselections
controlled by the network in a statistic period. These cell reselections are
caused by the deteriorating quality of downlink transmission.
� Number of Network Controlled Cell Reselection Attempts due to Traffic Load:
This counter is used to measure the number of cell reselections in a statistic
period. The information about cell reselections is sent because the cell is
overloaded.
� Number of Network Controlled Cell Reselection Attempts for Better Cell: This
counter is used to measure the number of cell reselections in a statistic
period. The information about cell reselections is sent because of higher
signal level in neighbor cells.
Page 58Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 58
Other Often-used Items
� Uplink/Downlink LLC Data Transmission Measurement
� you can get the LLC PDU length and the LLC mean rate and
then get the traffic model for RNP.
� Mean Length of Uplink LLC_PDUs
� Mean Length of Downlink LLC_PDUs
� Mean LLC_PDU Bytes per Uplink TBF
� Mean LLC_PDU Bytes per Downlink TBF
30
Page 59Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 59
Summary
� During the early stage of GPRS traffic measurement, pay
attention to the call drop rate and congestion rate. During
the late stage of GPRS traffic measurement, pay attention
to the resource utilization.
� The GPRS and GSM share radio resources. Sometimes the
GSM traffic measurement can be used to locate the GPRS
problems.
� For the GPRS network, analyze the PCU-level counters first,
and then the cell-level counters.
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