C-Guide to CDMA2000 1XEV-DO Traffic Statistic Analysis-20060412-A-1.1

Document number

Product

name CDMA network planning and optimization

Used by Huawei engineers Product version

Drafted by CDMA network planning department

Document version

1.1

Guide to CDMA2000 1XEV-DO Traffic Statistic Analysis

Prepared by Chen Junduo Date 2006-3-20

Reviewed by Date

Reviewed by Date

Granted by Date

Huawei Technologies Co., Ltd.

All rights reserved

Revision History

Date Revision version

Description Author

2006-3-6 1.0 First draft completed. Chen Junduo

2006-3-20 1.1 Revision based on review comments. Chen Junduo

Table of Contents

Chapter 1 About this Document ..................................................................................................... 2

Chapter 2 General Concept ............................................................................................................. 3

Chapter 3 Preparations for Traffic Statistic Analysis ................................................................... 5 3.1 Registering Traffic Statistic Tasks ........................................................................................ 5 3.2 Obtaining Existing Network Information and Verifying Network Status................................ 6 3.3 Main EVDO Items ................................................................................................................. 7

Chapter 4 Traffic Statistic Data Collection .................................................................................... 9

Chapter 5 EVDO Traffic Statistic Analysis Methods................................................................... 10 5.1 Analysis Method Determination.......................................................................................... 10 5.2 Traffic Statistic Data Analysis ............................................................................................. 11 5.3 Auxiliary Performance Analysis .......................................................................................... 11

Chapter 6 Proposing Optimization and Adjustment Solution ................................................... 14

Chapter 7 Verifying Effect ............................................................................................................. 15

Chapter 8 Analyzing Main EVDO Items........................................................................................ 16 8.1 Analysis of Main Items........................................................................................................ 16

8.1.1 Connection success ratio ......................................................................................... 16 8.1.2 Call Drop Ratio ......................................................................................................... 18 8.1.3 Service Data Throughput ......................................................................................... 20 8.1.4 Soft Handoff Success Ratio ..................................................................................... 23 8.1.5 Traffic ....................................................................................................................... 24 8.1.6 RSSI ......................................................................................................................... 24

8.2 Possible Causes for Affecting Items................................................................................... 25 8.2.1 Interference .............................................................................................................. 25 8.2.2 Pilot Pollution............................................................................................................ 25 8.2.3 Improper Setting of Adjacency................................................................................. 25 8.2.4 Improper Setting of Search Window Size ................................................................ 26 8.2.5 Improper Setting of PN Design ................................................................................ 26 8.2.6 Improper Settings of Handoff Parameters ............................................................... 26

List of Tables

Table 3-1 Measurement items of EVDO traffic statistic ............................................................ 5

List of Figures

Figure 2-1 Traffic statistic analysis flowchart ............................................................................ 3

Figure 8-1 Checking forward throughput problems ................................................................ 21

Guide to CDMA2000 1XEVDO Traffic Statistic Analysis For interal use only

2006-03-02 All rights reserved Page i of 32

Guide to CDMA2000 1X EVDO Traffic Statistic Analysis

Key words:

EVDO, traffic statistic analysis, measurement item, connection success ratio, call drop ratio, and soft handoff

Abstract:

This document describes CDMA traffic statistic analysis procedure and methods, auxiliary performance analysis tools and methods, and analyzes main EVDO items and makes the optimization suggestions. It can help the on-site optimization engineers to locate the network problems step by step to optimize the EVDO network.

List of references:

Name Author SN Release date

Query location or channel

Publishing house

cBSC Performance Measurement Reference Manual (V2.20)

Wireless documentation department

2005-07-15

Guide to CDMA 1X Traffic Statistic Analysis V3.0

Tang Chunmei and Tan Zhiwei

2005-09-29

EVDO Draft 2005-04-20

Guide to CDMA EVDO BSS Network Planning Parameter Settings

RRM team of CDMA network planning department

2004-10-15

Guide to CDMA2000 1XEV-DO Traffic Statistic Analysis For interal use only

4/25/2008 All rights reserved Page 2 of 32

Chapter 1 About this Document

This document provides traffic statistic methods and concepts for network optimization engineers to help on-site optimization engineers locate the network problems step by step and optimize the EVDO network.

The analysis of main measurement items is based on existing knowledge and experience, but Huawei is short of analyzing internal timers and release mechanism. The shortages will be supplemented in the later version.

This document is for internal use only.



Chapter 2 General Concept

The final purpose of traffic statistic analysis is to instruct the network optimization or network evaluation. Therefore, you need to have an overall understanding of existing network before the traffic statistic analysis, including the planning concept and optimization concept at early stage.

It is ensured that BSC overall performance analysis and carrier performance analysis are conducted when the network runs normally, and assist the performance analysis platform.

For the specific measurement item analysis, see the causes and optimization suggestions on the poor items. This can help locate problems fast.

Figure 2-1 Traffic statistic analysis flowchart



The traffic statistic analysis procedure is as follows:

1) Preparations for traffic statistic analysis include registering new tasks, collecting the information of existing network, and understanding network status, and EVDO measurement items. It is required to analyze traffic statistic data consciously. This step is crucial but ignored easily.

2) When you analyze the problems in an area or a BTS, you may skip BSC overall performance analysis, and directly analyze the specified carrier traffic statistic data. You can create an Excel table to describe the item trend and trace the performance items.

3) If the optimization effect is inconsistent with expected requirements, it is required to re-extract the traffic statistic data to analyze the items. This step may be repeated several times.



Chapter 3 Preparations for Traffic

Statistic Analysis

3.1 Registering Traffic Statistic Tasks

Basic traffic statistic tasks must be registered at the initial stage of deployment and exist permanently, including system optimization stage and maintenance stage. At later stage, new tasks can be registered based on the requirements of optimization maintenance.

Table 3-1 describes measurement set and measurement subnet of EVDO traffic statistic.

Table 3-1 Measurement items of EVDO traffic statistic

Measurement set Measurement subnet

EV-DO connection performance measurement

Performance statistic of BSC EVDO connection

EV-DO connection performance measurement-carrier –carrier

Performance statistic of carrier EV-DO connection

HRPD session performance measurement

Performance statistic of BSC HRPD session

HRPD session performance measurement –carrier

Performance statistic of carrier HRPD session

EV-DO reverse channel soft handoff performance measurement-BSC

Performance statistic of BSC EV-DO reverse channel soft handoff

EV-DO reverse channel soft handoff performance measurement - carrier

Performance statistic of carrier EV-DO reverse channel soft handoff

EV-DO service data throughput measurement --BSC

Performance statistic of EV-DO service data throughput

EV-DO service data throughput measurement -FRAME

Performance statistic of EV-DO service data throughput



EV-DO channel performance measurement

Performance statistic of EV-DO link information measurement

EVDO BSC overall performance measurement

EVDO BSC TCH congestion performance statistic

EVDO BSC traffic performance statistic

EVDO carrier overall performance measurement

EVDO carrier TCH congestion performance statistic

EVDO carrier traffic performance statistic

There are not many EVDO traffic statistic measurement sets, so it is required to register all the measurement sets during the deployment. According to the self-definition item function, you can calculate new measurement items based on the items of existing system.

For the detailed information of traffic statistic measurement points and measurement items, see cBSC Performance Measurement Reference Manual (V2.20).

The minimum BSC performance measurement period is 30 minutes. Generally, each measurement task requires 60-minute traffic statistic, especially the BSC overall performance measurement and carrier performance measurement.

In addition, you can register the tasks of 24-hour BSC overall performance measurement and carrier performance measurement to view the items easily.

In the Measurement Time, select 0-24(h). In the Measurement Type, select Semi-Permanent. In the Measurement Mode, select By Day.

The storage period is recommended for over 7 days. That is, if the storage period of the registered traffic statistic task is 7 days. The data before the 7 days cannot be viewed. Too long a storage period increases the system load. During the network optimization, it is recommended to output a complete traffic statistic result every day to a file in .xls format for the later contrast and comparison.

For more information of M2000 traffic statistic, see Guide to M2000 Traffic Statistic V1.0.

3.2 Obtaining Existing Network Information and Verifying Network Status

To obtain the information of existing network and verify the network status, do as follows:



1) Know the information of network planning at early stage, and obtain the documents, such as planning report, optimization report, engineering parameter table, network topology view, frequency plan report, and cell parameter design specifications. Have a general understanding of network and find some obvious problems.

2) Check whether the software and hardware version of existing network equipment are correct, matched, and consistent, and whether they are the most stable version. If the version has defects, the defects should be mitigated. The version matching table of the maintenance department can help understand the version information.

3) Confirm the calibration test and sensitivity test are conducted for each BTS to ensure that each BTS works normally and forward channel and reverse channel are normal.

4) Confirm unloaded test and loaded test of single BTS are conducted to ensure that single BTS works normally and the coverage is normal.

5) Conduct the antenna SWR test to ensure secure connection of antenna system.

6) Check whether the dialing test after the network is put into use, and the accuracy of engineering installation. The dialing test aims to confirm the normal access, good voice subjective feeling and normal handoff. Check whether PN displayed in the debug window of MS is consistent with the planned PN to confirm the antenna system is installed securely.

7) Check the inconsistence between the actual coverage and planned coverage. If the coverage is abnormal, check whether the antenna azimuth and downtilt angle are consistent with the scheduled target. If yes, but the coverage is inconsistent with coverage target, or the overlap coverage is serious, it is required to adjust the power parameters or engineering parameters.

8) Check whether the sensitive radio functions (such as load control, cell breathing, special handoff algorithm, special channel assignment algorithm, and special power control algorithm) are used. If yes, the traffic statistic analysis methods are different.

Traffic statistic is conducted under a good planning at early stage when the equipment runs normally, so the preparations for traffic statistic analysis are very crucial, but this step is ignored easily.

3.3 Main EVDO Items

According to EVDO R0 data service, the main traffic statistic items include:



1) System access performance items: session setup success ratio, connection success ratio, access congestion ratio, and activation success ratio originated by the terminal and system.

2) System service persistence items: data service call drop ratio, soft handoff success ratio and average call duration.

3) System resource assignment and load items: MACIndex utilization, CPU load, RSSI, and channel congestion ratio.

4) System data rate request and throughput items: PCF/PDSN data throughput ratio, busy-hour sessions, single sector average throughput ratio, and single user forward/reverse throughout ratio.

5) System data service request duration items: PPP connection setup duration, activation duration originated by the system and terminal, and data service average response time.

6) System link performance item: average Eb/Nt.

EVDO commercial networks are not mature like CDMA2000 1X commercial networks, and items to be checked are not definite.

According to EVDO investigation of Korean SKT existing network, they pay more attention to connection success ratio, call drop ratio and forward/reverse peak rate of single user.

In the offices where new EVDO network is constructed based on 1X or the network is construed newly, such as Portugal INQUAM commercial network, the EVDO deploys the BTSs based on 1X only in the hotspot areas. The insufficient coverage affects the connection and persistence performance items. At that time, the operators pay more attention to sector throughput ratio and single user throughput ratio, which represent the system capability.



Chapter 4 Traffic Statistic Data Collection

EVDO traffic statistic data can be collected through the following methods:

Obtain traffic statistic in tasks from M2000 for analysis in Excel table or by way of traffic statistic tools. It is the most common method.

Obtain the folder named with date under the directory: BAM\F$\cdma2000\M2000 for analysis by way of Nastar CDMA2000 tools. Currently, the Nastar does not support EVDO.

Obtain perf*.dat file under the directory: BAM\F$\cdma2000\backup restore the file through Sqlsever, and analyze it by way of Nastar CDMA 2000 or CBSSSTAR tools.



Chapter 5 EVDO Traffic Statistic Analysis

Methods

5.1 Analysis Method Determination

The traffic statistic analysis methods vary with the network. After knowing the existing network status and problems, you need to select one or multiple analysis methods.

The common analysis methods are:

I. TOPN worst cell

According to traffic statistic items (such as call drop ratio, connection success ratio, and soft handoff failure ratio), obtain the busy-hour average value or average value of the whole day, and pay more attention to the worst N BTSs or sectors for the fault analysis and optimization, which is also can be used to determine the optimization priority.

II. Time trend diagram

The trend diagram of traffic statistic item is a common method of traffic statistic. You can find out the change regularity of traffic statistic based on the change trend diagram of single or multiple items of whole network, BTS group or single BTS/sector by hour, day or week.

III. Area location

Network performance items change in some areas. The items in the areas are poor because of traffic increase, traffic model and radio environment change, BTS fault or uplink/downlink interference. The performance items of the whole network are affected. By comparing with network performance items before and after the change, mark the BTS or sector with the most change of network performance in the E-map, and locate the problem areas.

IV. Comparison and contrast

Traffic statistic items are affected by many causes. If the item is changed in one aspect, you can select a comparable item to confirm the problem and locate the cause.



It is required to pay more attention to the relative values of items than the absolute values. Only when the measurement values are great, is the item value meaningful. For example, 50% of call drop ratio does not mean a poor network. Only when the absolute values of successful connections and call drops are valuable for the measurement, is the value meaningful.

Many items are related mutually. For example, the interference and coverage may affect multiple items, such as connection success ratio, call drop ratio, and throughput ratio. Similarly, if the handoff success ratio is increased, the call drop ratio also can be improved. Therefore, it is also required to analyze other items when you analyze an item.

5.2 Traffic Statistic Data Analysis

After determining the analysis methods, you can collect the traffic statistic data. The analysis principle is: the whole prior to part. The whole can be BSC overall performance, or BTS group. The part can be single site, single sector, or single carrier. That is, after knowing the overall status of network, analyze sector carrier performance statistic. For the analysis of items, see Chapter 8 .

5.3 Auxiliary Performance Analysis

After the collected traffic statistic data is analyzed, the problems still are not located, such as the call drop ratio. According to the traffic statistic data, the release causes include Um interface loss, dormant timer timeout and other causes. It is still hard to locate fast the problems. At that time, by way of alarm information, drive test, RFMT tracing, and CDR tracing, further analyze the release cause values to assist the optimization.

I. Alarm information

The preparations for traffic statistic analysis contain checking the alarm information of the whole network.

When analyzing the traffic statistic data of a specific carrier, you can view the historical alarm information. The alarm information can reflect the equipment status in real time.

If an item in the traffic statistic is abnormal, it may be caused by the equipment alarm. Discriminating different alarm information and integrating traffic statistic items can help use the time effectively.

The alarm information can be viewed through M2000 centralized fault management system and alarm system of AirBridge.



In addition, the M2000 can implement task-based performance alarm function and define the performance items. If an item exceeds the threshold, the M2000 sends a performance alarm to the alarm server. The alarm information can be viewed through the centralized alarm customer station.

II. Drive test

For the new offices whose throughput of the overall network is still low, it is inaccurate to extract traffic statistic data for network performance analysis. At that time, it is required to measure connection success ratio, call drop ratio and throughput ratio based on the drive test data.

The operators pay more attention to the throughput ratio of single user in static state and dynamic state, but they do not exist in the traffic statistic, and can be obtained through the drive test only.

In addition, the drive test is a direct and accurate method for understanding network quality and locating the problems. From the perspective of radio network coverage structure, the drive test is irreplaceable compared with other methods, such as traffic statistic.

The drive test can help specific problems but is limited. The drive test route and time are limited, so it is impossible to obtain all the network data.

For example, it is difficult to locate the call drops and then analyze the call drop causes through drive test. Supposed that the call drop ratio is 3%, that is, there are 3 call drops out of 100 successful connections, and it is hard to locate the call drops. It is more impossible to know the call drop causes through the drive test.

The drive test can help ensure the radio network structure and engineering installation. The detailed analysis of traffic statistic items can help find the methods of improving the items. Integrating the macroscopical traffic statistic with specific test can solve the problem.

III. Signaling message tracing and debugging console printing

It is used to solve complicated problems.

AirBridge service maintenance system can trace the signaling messages of each interface, including the single user tracing of Um interface and Abis interface

When the complicated problems occur, on one hand, conduct the drive test, and on the other hand, trace the interface of test MS, especially signaling message of Um interface and locate the problems in terms of procedure.

cBSC debugging console abnormal printing can provide much information to help locate the problem. It is used only when the R&D engineers locate the problems.



IV. RFMT/CDR tracing

RFMT records the forward/reverse radio link information, including MS Rx, forward C/I, and forward FER.

Execute SET RFMTDO to trace the call information of specified IMSI (at most 10).

CDR records the call setup information, call release information and key events and status information of the call.

Execute MOD CDRFILTER to trace the call information of specified subrack.



Chapter 6 Proposing Optimization and

Adjustment Solution

After the network problems are located through traffic statistic analysis, you can propose optimization and adjustment solution to adjust the system parameters or solve the problems.

It is required to pay more attention to the parameter adjustment. For example, when the timer is modified, the timer length should not be too long and affect system load, causing other problems.

When the EVDO and CDMA2000 1X coexist, generally, the EVDO network is deployed based on the CDMA2000 1X, but the network layout adjustment cannot affect the coverage effect of CDMA2000 1X, especially the network sharing antenna system.

Before the EVDO network is deployed, CDMA2000 1X network has been optimized, and the parameters are very perfect. Therefore, the engineering parameters should not be adjusted largely. Adjusting the EVDO power parameters change the EVDO coverage range.



Chapter 7 Verifying Effect

The engineering parameters and system parameters should be adjusted step by step. Before next step adjustment, check the items for a period. Actually, the network items change largely, and the random is strong.

The items may be poor one hour before the adjustment, but the items are good immediately after the parameter adjustment. It does not indicate that the parameter adjustment is effective, because the items may be poor in next one hour.

You may make correct conclusions after checking the items for over one day by comparing with the items at the same period before the parameter adjustment (the items at the same period of the same day one week ago are best). In addition, the alarm information at the period must be concerned.

If the items after the optimization do not reach planned target, it is required to re-analyze the new traffic statistic data of abnormal items or carriers. This procedure must be repeated until the planned target is met.

For the poor items due to insufficient coverage and congestion, if the later expansion solution cannot be implemented and confirmed by the customer, it is regarded that the planned target is met.



Chapter 8 Analyzing Main EVDO Items

Some items are related, so the possible causes for low items may be similar. The common causes are analyzed in section 8.2 .

8.1 Analysis of Main Items

8.1.1 Connection success ratio

I. Call resource assignment failure

Call resource assignment failure means that BSC request call resource failure. The call resources include radio resource, terrestrial circuit resource, and hardware resources.

It is measured when the AN sends a TrafficChannelAssignment message to the AT and notifies the AT of monitoring channel and pilot in active set failure.

When the failure occurs, the AN does not send a TrafficChannelAssignment message. When there are many call resource assignment failures, you need to analyze the radio resource congestion, terrestrial link congestion, or transmission link congestion. Transmission link congestion can be checked based on the alarm information of link fault and then the analysis of system hardware.

II. Capturing reverse TCH failure

In the case of connection setup, the AN waits for a TrafficChannelComplete message after sending a TrafficChannelAssignment message. It is measured when AN fails to capture AT service frames on the reverse TCH to cause access failure.

Capturing reverse TCH failure is the most important cause of connection setup failure, and also the most common failure cause.

When the connection success ratio is low, you need to pay more attention to the low connection success ratio and solve the items with the most failures. If the failures are similar, you can pay attention to the capturing reverse TCH failure first.



According to Portugal INQUAM network measurement, capturing reverse TCH failure is the main cause of call connection failure. The possible causes of capturing reverse TCH failure are:

Forward signal is poor, and the terminal does not receive forward message or forward TCH that cannot be demodulated successfully by the terminal.

Reverse signal is poor, and the BTS cannot receive reverse TCH frames sent by the terminal, and the BTS timer expires.

III. No receiving TrafficChannelComplete

In the case of connection setup, if the AN does not receive a TrafficChannelComplete message after sending a TrafficChannelAssignment message and capturing AT reverse TCH frames, it is measured.

The possible causes for connection failure include:

Improper network structure

Improper network structure causes poor coverage or dead zones, and it is required to adjust the antenna system and even the site location to improve the radio network structure.

When the EVDO and CDMA2000 1X share the antenna system, you must ensure seamless coverage of voice service before adjusting the antenna system. It is required to avoid the coverage holes of CDMA 2000 1X voice service because the EVDO adjusts the antenna system.

Improper settings of power control parameters

The PCT initial value is too low. Data transmission is very crucial for the data service. Therefore, the PCT initial value can be greater. In addition, the improper settings of MAXPCT and MINPCT may reduce the system performance. According to of Portugal INQUAM existing EVDO optimization results, the parameter values are defaulted to optimal values.

Improper settings of access parameters

After receiving the TrafficChannelAssignment message from the BTS, the terminal sends pilot and DRC channel flow only through the reverse TCH.

If terminal receives the BTS ACK within the specified time, it indicates reverse TCH setup success. Otherwise, the terminal transmits the message at larger power.

Improper settings of reverse access parameters may decrease the Tx power of terminal and they cannot be demodulated by the system. The parameters include Probe Initial Adjust, Power Step, and Probe Num Step.



When the access parameters are adjusted, it is required to pay attention to the effect on the RSSI.

During the Portugal INQUAM EVDO test optimization, in 10 seamless sites of the capital, the above parameters are adjusted. The existing network traffic is still very low, so Probe Initial Adjust, Power Step, and Probe Num Step are increased compared with the default values. The optimization result verification shows that connection success ratio is increased by 4%, and reverse load is improved but receivable.

Access authentication failure

Before the TCH is established, the access authentication is required through the access channel. If the access authentication fails, the BTS sends a ConnectionReject message to the terminal, and the call setup fail.

The access authentication does not require too much Um interface signaling data exchange. Therefore, the probability of access authentication failure caused by the radio environment fading is low, and most of failures are caused by the incompatibility between the network and terminal.

You can trace the calls of terminal, analyze the signaling and judge the compatibility between the terminal and network to solve the problem through the network or terminal upgrade.

Reverse link overload

Reverse link load increases vary with the number of active terminals. The terminal should transmit at larger power to demodulate correctly the reverse link Rx signals. This further improves the reverse noises and the repeated process affects largely the access performance.

In the areas with high connection failure ratio but low requirement for data throughput, the reverse link overload control threshold can be small. The reverse link overload also can be solved through increasing the pilot overlap areas and sharing traffic with the BTSs surrounding. However, this increases the handoff ratio, and reduces the forward capacity. The best solution is to adding carriers or BTSs.

Interference Pilot pollution

8.1.2 Call Drop Ratio

Call drop ratio is an important item for evaluating EVDO system. Call drop means the abnormal release after the connection is established successfully, including Um interface lost and other cause.



Call drop ratio reflects the radio environment and system quality of EVDO network. A certain proportion of call drop is normal for the wireless network, but the cell with high call drop ratio must be optimized.

I. Connection release (Um interface lost)

The successful connection (after the AN receives an A9-Update A8 Ack message) is released because the Um interface is lost, that is, the AN cannot capture the signals of AT within a period and releases the connection.

At that time, the AT may disable the power amplifier or is transited to CDMA2000 1X network. The connection release due to the dormant timer timeout is not in the call drop measurement items.

Abnormal connection release includes the connection release because the AT thinks radio link loss, and abnormal connection release due to other causes. For example,

When the number of good frames of DRC channel received by the BTS within the specified time is less than the threshold, the BTS may think the radio link loss and releases the connection. The call drop occurs. This case is present when:

---- The BTS cannot receive the Tx signals from the terminal due to large fading (at the back of the buildings).

----- The terminal cannot demodulate forward link correctly within the specified time and stops the transmission.

------ When the terminal does not receive a message (such as PathUpdate message and TCHComplete message) within the specified time, the terminal stops sending the messages.

Handoff failure. This case occurs when the BTS sends a TraffiChannelAssignment message to the terminal, and notifies the terminal of the change in active set, and the terminal returns a TCHComplete message. If the BTS does not receive the TCHComplete message, the BTS releases the connection.

In the EVDO system, the possible causes for call drop include poor radio link, transmission link fault, software/hardware fault, interference, handoff, and improper settings of parameters.

This section mainly describes the call drop due to poor radio link and its optimization. For detail, see the following:

Forward coverage Interference Pilot pollution



Improper setting of adjacency Improper setting of search window Improper setting of PN design Improper settings of handoff parameters

Different from the voice services of CDMA2000 1X, the data services do not raise high demands on the realtime. In the case of call drop, the network and terminal will fast the re-establish the connection before the users know of the disconnection.

When the call drop occurs in the voice network, the voice services may be interrupted, and the user satisfactions are bad. Therefore, the effect on user satisfactions when the call drop occurs in the EVDO network is smaller than that in CDMA2000 1X network. The call drop ratio is less important than that of voice service.

When the voice network and data network conflict, the call drop ratio requirement for the voice network must be considered. When the EVDO overlays CDMA2000 1X network, the inconsistence probability can be reduced to the least to ensure the performance requirements for voice network and data network.

8.1.3 Service Data Throughput

The data in the EVDO BSC service data throughput performance statistic means the net load (PPP data packet), excluding the data header overhead, such as RLP header. The data throughput can be defined at different network layers. For example, data throughput at RLP layer is the data transmitted at RLP layer within the unit time, but the error retransmitted data is not calculated. The data throughput is consistent with actual user feeling.

BSC service data throughput can be used to evaluate the overall network traffic. During the actual network optimization, for the EVDO (Rel0), the peak throughput of single user at physical layer should reach 2.457Mbps. The user pays the most attention to the property. The following analyzes the forward/reverse throughput of single user.

The peak rate raises high demands on the radio environment, portable computer, terminal settings, system bandwidth, and PS network stability. May problems are derived.

For Huawei existing version, the downlink peak rate of single user at application layer should reach over 2.1Mbps. If the peak rate is not satisfied, you can start to check the system.

The possible causes for affecting EVDO forward link data throughput include:



The radio environment is poor, such as poor coverage, strong interference and BTS hardware fault, so the DRC request rate is less than the maximum rate supported by the radio channel.

Multiple users request data services in the BTS, but the user has no complete data transfer time.

The configuration of functional entity in the core network affects largely the data throughput ratio, such as the important functional entity PDSN of data service. Even if a router between the PDSN and PCF is not configured well or the quality is poor, the data throughput ratio may be affected largely.

The possible causes for affecting EVDO reverse link data throughput are similar to that of CDMA2000 1x. They are:

The radio environment is poor, so the reverse PER is higher than target value (such as 1%). The reverse rate control can help request the low rate.

If the system resources are insufficient or reverse link load is too heavy, the reverse link load control may restrict the reverse data rate.

In the core network, the setting of each functional entity is improper.

When the data throughput is decreased, it is required to judge the restricted points and troubleshoot the problems.

If the forward throughput cannot meet the system requirement, check the following:

Figure 8-1 Checking forward throughput problems

1) Settings of portable computer and terminal

Check the setting of TcpWindowSize in the registry.

TCP window size should be integral multiplies of 8k byte, and TcpWindowSize >= bi-directional delay × rate. Generally, TCP window size is set to 64000Byte.

For example, after the dialing connection is established, you can Ping the network server. If round-trip delay (RBT) is 200ms and expected FTP download rate is 2Mbps, TcpWindowSize >= 0.2*2000000/8 = 50000byte, and the value should be approximate to 64000byte.

For the Windows XP operating system, you also need to check DefaultRcvWindow in the registry. The DefaultRcvWindow should be set to 65535 to ensure large Rx buffer area of portable computer. ,



In the case of single user throughput test of EVDO, you must ensure that the hybrid-mode terminal works in EVDO single mode state. If the terminal works in dual-mode state, the terminal will be prior to stay in the EVDO state, and then is transited to CDMA2000 1X based on its timeslot period.

When the terminal monitors the CDMA2000 1x channel, EVDO does not send the data. From the perspective of download effect, the rate changes periodically, and the average rate is low.

2) Radio environment quality

In the case of download through the FTP, CAIT or the debugging console of BSC can help check whether the FER is greater than 1%, and there are many NAK frames at the Um interface.

If the cases occur, you need to confirm radio weak coverage or interference, and adjust reverse power control parameters of BSC to increase the terminal Tx and improve the FER, but the capacity is wasted.

The radio coverage of the terminal is a key factor of affecting data throughput ratio. When the terminal is in the weak coverage area (for example, the Rx power is -90dBm and the SNR of the strongest pilot is less than -10dB), the low SNR affects the data transmission rate but increases the retransmission probability, and decreases the data throughput ratio. This can be analyzed through the drive test.

In addition, in the case of virtual soft handoff, ping-pong handoff cannot occur easily between two strong carriers. If the ping-pong handoff occurs, if the DRC channel request rate in the AT through the CAIT or other tools reaches 1.23mbps, the actual rate is 300-400kbps. You need to pay more attention to this case especially the compared test.

3) Setting of radio access network bandwidth

The system bandwidth must meet the requirement of service flow. According to the paths of system service flow, check the bandwidth between BTS and BIE, between BIE and FMR, and between FMR and PPU. The PPU cannot be a bottleneck of the upper part.

In the case of calculating the bandwidth between BTS and BIE,

For the test offices of single DO sector, it is required to provide 2.457/0.71=3.46Mbps of PV bandwidth at the Abis interface. At the Abis interface, when PVC bandwidth of DO carrier >=3.6Mbps, it is required to provide 2E1 or 3T1 physical configuration.

For 3-sector DO site, provide the configuration based on actual conditions. In the limit conditions, it is required to configure 6E1 or 7T1, and 9.3Mbps of



PVC bandwidth. PVC bandwidth between the BSC boards is configured at the maximum value.

4) Packet transmission stability

In the test offices, the BSC, the PDSN, and the service server are in the equipment room, and the network structure is simple. If the connections between BSC and PDSN, and between PDSN and service server are secure, the problems do not occur generally.

5) Settings of packet core network

In the packet core network, no bottleneck exists in the bandwidth. The network from the PDSN to content server should be simple as possible to reduce the effect of delay and jitter.

For the test use only, the FTP server can be in the firewall. Meanwhile, it is required to ensure the virus-protection of core network, and install standard anti-virus software in each computer. This can avoid the core network breakdown due to the burst of worm viruses.

8.1.4 Soft Handoff Success Ratio

It means the BSC EVDO reverse soft handoff success ratio, including common soft handoff and softer handoff.

The BSC checks the added and deleted branches in the soft handoff decision. The soft handoff requests include adding branches and deleting branches.

If two branches are added and one branch is deleted during each soft handoff decision, one decision measures three soft handoff requests. Adding or deleting a branch is regarded as a soft handoff request. Adding or deleting a branch failure is regarded as a failure.

The items of carrier EV-DO reverse channel handoff performance statistic are same completely as that of BSC EVDO reverse channel soft handoff performance statistic.

The definitions, types, measurement methods and measurement points of the items are consistent, but carrier EV-DO reverse channel soft handoff performance statistic is carrier-specific, and BSC EVDO reverse channel soft handoff performance statistic is BSC specific.

I. No available radio resource

After trigger the handoff and receiving a TrafficChannelComplete message, the BSC checks the soft handoff branch failures, and discriminate the failure causes:

Handoff branch carrier unavailable



Carrier logic channel count overflow Redundant physical reverse CE = 0.

II. Requested terrestrial resource unavailable

It is related to BTS terrestrial link setup failure. After receiving a TrafficChannelComplete message, the BSC checks the soft handoff failures and discriminates the handoff causes. The terrestrial resources include BTS, CBIE, CFMR, and TIE.

III. Radio interface fault

After trigger the soft handoff, the BSC does not receive a TrafficChannelComplete message within a period. It indicates the radio interface fault, because forward or reverse radio link is too poor, and the MS does not receive a TrafficChannelAssignment message or the BTS does not receives a TrafficChannelComplete message.

Interference Improper setting of adjacency design Improper setting of PN design Improper settings of handoff parameters

IV. Congestion

8.1.5 Traffic

I. TCH Seizure Duration (Excluding Handff) (Second)

It means the TCH seizure duration of all the EVDO calls (excluding handoff). The traffic (excluding handoff) is the actual user traffic. It is an item for the operator to measure the service development and also the most direct item for the optimization engineer to know the network load. The carrier traffic can help understand the user distribution and behaviors. Only the items whose traffic is heavy are meaningful.

8.1.6 RSSI

The RSSI of EVDO system and that of CDMA2000 1X are in the Performance Measurement subnet. The measurement is carrier-specific. The definition and analysis method are same as that of CDMA2000 1X.



8.2 Possible Causes for Affecting Items

Most possible causes are similar to that of CDMA2000 1X. For the specific analysis and processing suggestions, see Guide to CDMA2000 1X Traffic Statistic Analysis. This section describes the contents of EVDO only.

8.2.1 Interference

The interference includes EVDO system interference itself and external system (including CDMA2000 1X). When the system receives interference, in the reverse link, the MS transmit power is high, and the PER is high. In the forward link, the Rx is high, but the C/I is poor, and the PER is high. The system interference itself can be adjusted based on the quality, capacity and coverage.

The external interference can be detected and cleared through the interference tester. The RSSI of BTS can help understand the reverse interference. Generally, under a loaded condition, the RSSI should not be greater than -90dBm. When RSSI is greater than -90 dBm, especially greater than -80 dBm, the access is difficult, and the call drop occurs and the throughput is reduced.

8.2.2 Pilot Pollution

The pilot pollution is different from that of CDMA2000 1X. The EVDO uses virtual soft handoff in the forward link. In the forward direction, the system can send service data to a terminal only within each timeslot. If only there are multiple pilots, the non-primary pilot will interfere with primary pilot. The primary pilot C/I decreases, but the PER increases. This brings about connection failure, handoff failure, and throughput decrease.

8.2.3 Improper Setting of Adjacency

Improper setting of adjacency means the missing neighbor. If the signals of missing neighbor are strong, the interference is also large. This brings about sharp decrease of data throughput, call drop, and connection failure and MS reverse power increase. The case can be found easily. Generally, the signals of missing neighbor are not strong, and it does not cause many call drops and call failures. The effect on system performance items cannot be ignored, but it is not obvious.

The setting of adjacency is similar to that of CDMA2000 1X. In principle, the EVDO should configure the adjacent cells as neighbor cells of other sectors in the same BTS. When the EVDO system and CDMA2000 1x system share the antenna system, the coverage prosperities are very similar. After the optimization



of CDMA2000 1x for a long time, the neighbor setting is appropriate. Therefore, at the early stage of EVDO network design, see neighbor setting of CDMA2000 1x network.

8.2.4 Improper Setting of Search Window Size

The principle is similar to that of CDMA2000 1X. If the search window of EVDO active set and neighbor set is too small, a strong multipath or pilot is located beyond the search window to cause the interference. This reduces the Rx SNR of terminal, and affects sector throughput and connection performance and leads to the call drop. If the search window is too great, the terminal search speed is slow and the call drop occurs easily.

8.2.5 Improper Setting of PN Design

The PN design of EVDO is similar to that of CDMA2000 1X. Different EVDO cells or sectors are differentiated based on the PN codes. The strong interference caused by the PN offset will bring about connection failure, call drop, and data throughput decrease. The effect and solution are also similar to that of CDMA2000 1X.

8.2.6 Improper Settings of Handoff Parameters

The reverse soft handoff principle of EVDO is similar to that of CDMA 1X. The common handoff parameters are PILOTADD, PILOTCMP, and PILOTDROP. The improper settings of handoff parameters will cause handoff failure, increase the call drop ratio, and affect the system capacity.

The PILOTADD can increase the soft handoff threshold. This may reduce soft handoff zones and decrease the soft handoff ratio, but cause handoff delay and coverage holes. A too small value of the parameter may reduce the soft handoff ratio. This can extend soft handoff zones and increase the soft handoff ratio.

If the PILOTCMP is too small, the pilots in candidate set can replace easily that in active set, and the ping-pong handoff occurs easily. If the parameter is too great, the pilots in candidate set can hardly replace that in active set, and the AT cannot enjoy services from the strongest pilot in time.

If the PILOTDROP is too great, an available signal can be deleted from the active set quickly. If the parameter is too small, the soft handoff threshold is reduced, and the pilots in active set are deleted hardly from the active set.

Date post:	21-Oct-2015
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C-Guide to CDMA2000 1XEV-DO Traffic Statistic Analysis-20060412-A-1.1

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