RACH Storm Filtration(GBSS14.0_01)

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RACH Storm Filtration

GBSS14.0

Feature Parameter Description

Issue 01

Date 2012-04-28

HUAWEI TECHNOLOGIES CO., LTD.


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Copyright Huawei Technologies Co., Ltd. 2012. All rights reserved.

No part of this document may be reproduced or transmitted in any form or by any means without prior

written consent of Huawei Technologies Co., Ltd.

Trademarks and Permissions

and other Huawei trademarks are trademarks of Huawei Technologies Co., Ltd.

All other trademarks and trade names mentioned in this document are the property of their respective

holders.

Notice

The purchased products, services and features are stipulated by the contract made between Huawei and

the customer. All or part of the products, services and features described in this document may not be

within the purchase scope or the usage scope. Unless otherwise specified in the contract, all statements,

information, and recommendations in this document are provided "AS IS" without warranties, guarantees orrepresentations of any kind, either express or implied.

The information in this document is subject to change without notice. Every effort has been made in the

preparation of this document to ensure accuracy of the contents, but all statements, information, and

recommendations in this document do not constitute the warranty of any kind, express or implied.

Huawei Technologies Co., Ltd.

Address: Huawei Industrial Base

Bantian, Longgang

Shenzhen 518129

People's Republic of China

Website: http://www.huawei.com

Email: [email protected]
http://www.huawei.com/http://www.huawei.com/mailto:[email protected]:[email protected]:[email protected]://www.huawei.com/


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RACH Storm Filtration Contents

Issue 01 (2012-04-28) Huawei Proprietary and Confidential

Copyright Huawei Technologies Co., Ltd.

ii

Contents

1 About This Document .................................................................................................................. 1-11.1 Scope ...................................................................................................................................... 1-11.2 Intended Audience ................................................................................................................... 1-11.3 Change History ........................................................................................................................ 1-11.4 Document Issues ..................................................................................................................... 1-1

2 Overview ........................................................................................................................................... 2-13 Technical Description.................................................................................................................. 3-1

3.1 Working Principles ................................................................................................................... 3-13.2 Feature Implementation............................................................................................................ 3-1

4 Related Features ............................................................................................................................ 4-15 Impact on the Network ................................................................................................................. 5-1

5.1 Impact on System Capacity ...................................................................................................... 5-15.2 Impact on Network Performance .............................................................................................. 5-1

6 Engineering Guidelines ............................................................................................................... 6-16.1 When to Use RACH Storm Filtration ......................................................................................... 6-16.2 Information to Be Collected ...................................................................................................... 6-16.3 Network Planning ..................................................................................................................... 6-16.4 Deploying RACH Storm Filtration.............................................................................................. 6-16.5 Performance Optimization ........................................................................................................ 6-16.6 Troubleshooting ....................................................................................................................... 6-2

7 Parameters ....................................................................................................................................... 7-18 Counters ........................................................................................................................................... 8-19 Glossary ............................................................................................................................................ 9-110 Reference Documents............................................................................................................. 10-1


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RACH Storm Filtration 1 About This Document



1-1

1 About This Document

1.1 Scope

This document describes the GBFD-511505 RACH Storm Filtration feature, including its technicaldescription, related features, network impact, and engineering guidelines.

1.2 Intended Audience

This document is intended for:

Personnel who need to understand the RACH Storm Filtration feature

Personnel who work with Huawei GSM products

1.3 Change History

This section provides information about the changes in different document versions.

There are two types of changes, which are defined as follows:

Feature change: refers to a change in the RACH Storm Filtration feature of a specific product version.

Editorial change: refers to a change in wording or the addition of information that was not described inthe earlier version.

1.4 Document Issues

The document issue is as follows:

01 (2012-04-28)

01 (2012-04-28)

This is the first release of GBSS14.0.

This is a new document.


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RACH Storm Filtration 2 Overview



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2 Overview

When initiating a call, an MS sends a random access request message to the BTS on the randomaccess channel (RACH) to request a channel. The random access request message contains the

following information:

Channel setup cause: paging response, emergency call, mobile-originated call, short messageservice (SMS), location update, or other causes

Random access reference value: five bits randomly selected by the MS

If an MS sends excessive random access request messages to the BTS, an RACH storm may occur,which deteriorates counters. The possible causes for an RACH storm are as follows:

MS exceptions

A large number of abrupt location update requests

A large number of abrupt random access requests due to malicious manual operations

A large number of abrupt paging requests


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RACH Storm Filtration 3 Technical Description



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3 Technical Description

3.1 Working Principles

The RACH Storm Filtration feature effectively restrains the RACH storm.Figure 3-1shows its workingprinciples.

Figure 3-1 Working principles for the RACH Storm Filtration feature

If N consecutive random access request messages with the same random access reference value meet

the specified time and timing advance (TA) filter conditions, the BTS filters out these messages torestrain the RACH storm.

3.2 Feature Implementation

After this feature is enabled, the BTS discards random access request messages that meet the filterconditions. The parameters for implementing this feature are categorized into the following types:

Function Parameters

RACHFLTSWITCH:specifies whether to enable the RACH Storm Filtration feature.

RACHFLTTYPE:specifies whether to filter out the random access request messages whose channelsetup cause is emergency call.
http://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-para/gcellsoft_rachfltswitch.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-para/gcellsoft_rachfltswitch.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-para/gcellsoft_rachflttype.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-para/gcellsoft_rachflttype.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-para/gcellsoft_rachflttype.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-para/gcellsoft_rachfltswitch.html


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3-2

Filter Condition Parameters

After this feature is enabled, the BTS filters out random access request messages that meet the filterconditions specified by the following parameters:

RACHFLTFREQ:specifies the frequency filter condition, which is the maximum number ofconsecutive random access request messages with the same random access reference value. Therecommended value is 4.

If the number of random access request messages with the same random access reference value isgreater than the value of this parameter, the frequency filter condition is met.

RACHFLTTATHD:specifies the TA filter condition, which is the minimum TA difference between two

consecutive random access request messages with the same random access reference value. Therecommended value is 4.

If the actual TA difference is less than or equal to the value of this parameter, the TA filter condition ismet.

RACHFLTTMINTVAL:specifies the time filter condition, which is the minimum interval between two

consecutive random access request messages with the same random access reference value.If the actual interval is less than or equal to the value of this parameter, the time filter condition is met.

If this parameter is set to a large value, two consecutive random access request messages with thesame random access reference value are likely to meet the time filter condition. The recommendedvalue is 1 and the unit is 100 ms.

Within the specified interval, different MSs are highly likely to use the same random access referencevalue because only five bits are used for MSs to select a random access reference value. As a result,some random access request messages are filtered out by mistake after this feature is enabled.

Figure 3-2shows the procedure for implementing the RACH Storm Filtration feature
http://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-para/gcellsoft_rachfltfreq.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-para/gcellsoft_rachfltfreq.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-para/gcellsoft_rachflttathd.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-para/gcellsoft_rachflttathd.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-para/gcellsoft_rachflttmintval.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-para/gcellsoft_rachflttmintval.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-para/gcellsoft_rachflttmintval.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-para/gcellsoft_rachflttathd.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-para/gcellsoft_rachfltfreq.html


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3-3

Figure 3-2 Procedure for implementing the RACH Storm Filtration feature

AB, which stands for access burst, indicates a random access request message.

After this feature is enabled, the BTS discards random access request messages with the samerandom access reference value without reporting any information to the BSC. After filtering out themessages for 5 minutes, the BTS decides on filter conditions again.


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RACH Storm Filtration 4 Related Features



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4 Related Features

None


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RACH Storm Filtration 5 Impact on the Network



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5 Impact on the Network

5.1 Impact on System Capacity

If the interval specified byRACHFLTTMINTVAL exceeds 3000 ms, the traffic volume may decrease.

The larger the value of this parameter, the more significantly the traffic volume may decrease.

5.2 Impact on Network Performance

If this feature is enabled withRACHFLTFREQset to 4 andRACHFLTTATHDset to 4, the RACH storm

can be restrained, increasing the immediate assignment success rate.
http://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-para/gcellsoft_rachflttmintval.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-para/gcellsoft_rachflttmintval.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-para/gcellsoft_rachflttmintval.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-para/gcellsoft_rachfltfreq.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-para/gcellsoft_rachfltfreq.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-para/gcellsoft_rachfltfreq.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-para/gcellsoft_rachflttathd.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-para/gcellsoft_rachflttathd.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-para/gcellsoft_rachflttathd.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-para/gcellsoft_rachflttathd.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-para/gcellsoft_rachfltfreq.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-para/gcellsoft_rachflttmintval.html


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RACH Storm Filtration 6 Engineering Guidelines



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6 Engineering Guidelines

6.1 When to Use RACH Storm Filtration

It is recommended that the RACH Storm Filtration feature be enabled in cells that occasionally meet thefollowing conditions in a week: The traffic volume remains unchanged.

The immediate assignment success rate decreases.

The SDCCH congestion rate increases.

The KPIs, including TCH traffic volume, assignment success rate, and call drop rate, remainunchanged.

6.2 Information to Be Collected

Before deploying this feature, collect the following historical information about cells:

Traffic volume

Immediate assignment success rate

SDCCH congestion rate

6.3 Network Planning

N/A

6.4 Deploying RACH Storm Filtration

For details about how to activate, verify, and deactivate this feature, seeConfiguring RACH Storm

Filtration.

6.5 Performance Optimization

Monitoring

After the RACH Storm Filtration feature is enabled, monitor the counters listed inTable 6-1.

Table 6-1 Counters to be monitored

Measurement Unit

Counter Name Description

KPIMeasurement perCell(CALL.KPICalc.CELL)

CELL.KPI.TCH.TRAF.ERL.TRAF K3014: Traffic Volume on TCH

CELL.KPI.TCHH.TRAF.ERL K3034: TCHH Traffic Volume

ImmediateAssignmentMeasurement perCell(CALL.I

CELL.ESTB.IND.SUCC.RATE.IMM.ASS

RA303I: Success Rate of Call Setup(Immediate Assignment)

CELL.IMM.ASS.CMD.TCHF A3017: Immediate AssignmentCommands (TCHF)
http://localhost/var/www/apps/conversion/tmp/FAGHtml/mbsc/cme-feature-activation-guide/GBFD-511505.htmlhttp://localhost/var/www/apps/conversion/tmp/FAGHtml/mbsc/cme-feature-activation-guide/GBFD-511505.htmlhttp://localhost/var/www/apps/conversion/tmp/FAGHtml/mbsc/cme-feature-activation-guide/GBFD-511505.htmlhttp://localhost/var/www/apps/conversion/tmp/FAGHtml/mbsc/cme-feature-activation-guide/GBFD-511505.htmlhttp://localhost/var/www/apps/conversion/tmp/FAGHtml/mbsc/cme-feature-activation-guide/GBFD-511505.htmlhttp://localhost/var/www/apps/conversion/tmp/FAGHtml/mbsc/cme-feature-activation-guide/GBFD-511505.html


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RACH Storm Filtration 6 Engineering Guidelines



6-2

mmAss.CELL)

CELL.IMM.ASS.CMD.TCHH A3018: Immediate AssignmentCommands (TCHH)

CELL.IMM.ASS.CMD.SD A3010: Immediate AssignmentCommands (SDCCH)

Parameter Optimization

Optimize the parameters related to this feature based on the monitored counters.

If the value of the RA303I counter increases and the values of the K3014 and K3034 counters remainunchanged, parameter optimization is not required.

If the value of the RA303I counter increases and the values of the K3014, K3034, A3017, A3018, andA3010 counters decrease, setRACHFLTTMINTVAL to a smaller value and setRACHFLTFREQto a

larger value.

6.6 Troubleshooting

N/A
http://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-para/gcellsoft_rachflttmintval.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-para/gcellsoft_rachflttmintval.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-para/gcellsoft_rachflttmintval.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-para/gcellsoft_rachfltfreq.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-para/gcellsoft_rachfltfreq.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-para/gcellsoft_rachfltfreq.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-para/gcellsoft_rachfltfreq.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-para/gcellsoft_rachflttmintval.html


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RACH Storm Filtration 7 Parameters



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7 Parameters

Table 7-1 Parameter description

Parameter ID NE MML Command DescriptionRACHFLTFREQ BSC6900 SET

GCELLSOFTMeaning: Minimum number of consecutiverandom access requests with the samerandom access cause. If the number ofconsecutive random access requests with thesame random access cause is greater thanthe value of this parameter, the BTS filtersout the random access requests.

GUI Value Range: 1~20

Actual Value Range: 1~20

Default Value: 4

Unit: None

RACHFLTSWITCH BSC6900 SETGCELLSOFT

Meaning: Whether to enable the RACH stormfiltration algorithm.

GUI Value Range: NO(No), YES(Yes)

Actual Value Range: NO, YES

Default Value: NO(No)

Unit: None

RACHFLTTATHD BSC6900 SETGCELLSOFT

Meaning: TA difference between twoconsecutive random access requests with the

same random access value. If the TAdifference is less than or equal to the value ofthis parameter, the TA filter condition is met.



Default Value: 4

Unit: None

RACHFLTTMINTVAL BSC6900 SETGCELLSOFT

Meaning: Interval between two consecutiverandom access requests with the samerandom access value. If the interval is lessthan or equal to the value of this parameter,the time filter condition is met.



Default Value: 1

Unit: 100ms
http://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-para/gcellsoft_rachfltfreq.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-para/gcellsoft_rachfltfreq.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-mml/set-gcellsoft.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-mml/set-gcellsoft.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-mml/set-gcellsoft.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-para/gcellsoft_rachfltswitch.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-para/gcellsoft_rachfltswitch.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-mml/set-gcellsoft.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-mml/set-gcellsoft.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-mml/set-gcellsoft.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-para/gcellsoft_rachflttathd.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-para/gcellsoft_rachflttathd.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-mml/set-gcellsoft.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-mml/set-gcellsoft.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-mml/set-gcellsoft.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-para/gcellsoft_rachflttmintval.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-para/gcellsoft_rachflttmintval.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-mml/set-gcellsoft.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-mml/set-gcellsoft.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-mml/set-gcellsoft.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-mml/set-gcellsoft.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-mml/set-gcellsoft.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-para/gcellsoft_rachflttmintval.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-mml/set-gcellsoft.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-mml/set-gcellsoft.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-para/gcellsoft_rachflttathd.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-mml/set-gcellsoft.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-mml/set-gcellsoft.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-para/gcellsoft_rachfltswitch.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-mml/set-gcellsoft.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-mml/set-gcellsoft.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-para/gcellsoft_rachfltfreq.html


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RACH Storm Filtration 7 Parameters



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Parameter ID NE MML Command Description

RACHFLTTYPE BSC6900 SETGCELLSOFT

Meaning: Random access type used for theRACH storm filtration algorithm.

GUI Value Range:EMERGENCY_CALL_ALLOWED(EmergencyCall Allowed)

Actual Value Range:EMERGENCY_CALL_ALLOWED

Default Value:EMERGENCY_CALL_ALLOWED-0

Unit: None
http://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-para/gcellsoft_rachflttype.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-para/gcellsoft_rachflttype.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-mml/set-gcellsoft.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-mml/set-gcellsoft.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-mml/set-gcellsoft.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-mml/set-gcellsoft.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-mml/set-gcellsoft.htmlhttp://localhost/var/www/apps/conversion/tmp/RNCParaHtml/mbsc/m-para/gcellsoft_rachflttype.html


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RACH Storm Filtration 8 Counters



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8 Counters

There are no specific counters associated with this feature.


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RACH Storm Filtration 9Glossary



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9 Glossary

For the acronyms, abbreviations, terms, and definitions, see theGlossary.
http://localhost/var/www/apps/conversion/tmp/scratch_7/Glossary.htmhttp://localhost/var/www/apps/conversion/tmp/scratch_7/Glossary.htmhttp://localhost/var/www/apps/conversion/tmp/scratch_7/Glossary.htmhttp://localhost/var/www/apps/conversion/tmp/scratch_7/Glossary.htm


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RACH Storm Filtration 10Reference Documents



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10 Reference Documents

None