18_Reliability and Redundancy of Flexi Multiradio BTS

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Document Code/Version © 2010 Nokia Siemens Networks PageSharenet 445958/3.0 Proprietary and Confidential 1 (18 )

RELIABILITY COMMUNICATION MATERIAL

FLEXI MULTIRADIO BTS

BTS Systems and Configurations Reliability

Version 3.0

4. February 2010



The information in this document is subject to change without notice and describes only the product definedin the introduction of this documentation. This documentation is intended for the use of Nokia SiemensNetworks customers only for the purposes of the agreement under which the document is submitted, and nopart of it may be used, reproduced, modified or transmitted in any form or means without the prior writtenpermission of Nokia Siemens Networks. The documentation has been prepared to be used by professionaland properly trained personnel, and the customer assumes full responsibility when using it. Nokia SiemensNetworks welcomes customer comments as part of the process of continuous development andimprovement of the documentation.

The information or statements given in this documentation concerning the suitability, capacity, orperformance of the mentioned hardware or software products are given "as is" and all liability arising inconnection with such hardware or software products shall be defined conclusively and finally in a separateagreement between Nokia Siemens Networks and the customer. However, Nokia Siemens Networks hasmade all reasonable efforts to ensure that the instructions contained in the document are adequate and freeof material errors and omissions. Nokia Siemens Networks will, if deemed necessary by Nokia Siemens

Networks, explain issues which may not be covered by the document.

Nokia Siemens Networks will correct errors in this documentation as soon as possible. IN NO EVENT WILLNokia Siemens Networks BE LIABLE FOR ERRORS IN THIS DOCUMENTATION OR FOR ANYDAMAGES, INCLUDING BUT NOT LIMITED TO SPECIAL, DIRECT, INDIRECT, INCIDENTAL ORCONSEQUENTIAL OR ANY LOSSES, SUCH AS BUT NOT LIMITED TO LOSS OF PROFIT, REVENUE,BUSINESS INTERRUPTION, BUSINESS OPPORTUNITY OR DATA,THAT MAY ARISE FROM THE USEOF THIS DOCUMENT OR THE INFORMATION IN IT.

This documentation and the product it describes are considered protected by copyrights and otherintellectual property rights according to the applicable laws.

The wave logo is a trademark of Nokia Siemens Networks Oy. Nokia is a registered trademark of Nokia

Corporation. Siemens is a registered trademark of Siemens AG.

Other product names mentioned in this document may be trademarks of their respective owners, and theyare mentioned for identification purposes only.

Copyright © Nokia Siemens Networks 2010. All rights reserved




Nokia Siemens Networks





Contents

1. INTRODUCTION............................................................................................................................ 4 2. RELIABILITY ENGINEERING........................................................................................................ 4

2.1 Definition of reliability concepts ............................................................................................... 4 2.2 Reliability terminology and calculation principles .................................................................... 5

3. RELIABILITY METHODS TO OPTIMIZE DESIGN FUNCTIONALITY .......................................... 7 3.1 Redundancy ............................................................................................................................ 7 3.2 Recovery functionality ............................................................................................................. 7 3.3 Remote controllability .............................................................................................................. 7

4. FLEXI MULTIRADIO BTS RELIABILITY PRINCIPLES ................................................................. 8 4.1 Standard reliability functionalities ............................................................................................ 8 4.2 Reliability performance optimization during R&D work............................................................ 8

4.2.1 HW reliability .................................................................................................................... 8 4.2.2 Software reliability ............................................................................................................ 9

5. FLEXI MULTIRADIO BTS SYSTEM RELIABILITY...................................................................... 10 5.1 Flexi WCDMA BTS (HW Release 1) Reliability Performance................................................ 10 5.2 Flexi Multiradio BTS (HW Release 2) System Reliability Performance ................................. 11

5.2.1 MTBF values for one System Module and one 3-sector RF Module configurations ...... 11 5.2.2 MTBF values for one System Module and two 3-sector RF Module configurations....... 11 5.2.3 MTBF values for two System Module and one 3-sector RF Module configurations....... 12 5.2.4 MTBF values for two System Module and two 3-sector RF Module configurations ....... 12 5.2.5 MTBF values one System Module and 3x Remote Radio Head configurations............. 13 5.2.6 Redundancy and capacity definitions in Flexi Multiradio BTS........................................ 14 5.2.7 System Availability and Downtime ................................................................................. 14

5.3 Prerequisites and assumptions for predicted data ................................................................ 15 5.4 Temperature trend for system MTBF and thermal protectioning........................................... 16 5.5 RF-power effect to the system MTBF.................................................................................... 17







Document Code/Version © 2010 Nokia Siemens Networks Page

1. INTRODUCTION

Purpose of this document is to represent the Flexi Multiradio BTS product predicted reliability data andintroduce the reliability and calculation methods. Document also introduces the Flexi BTS functionalityreliability point of view.

2. RELIABILITY ENGINEERING

2.1 Definit ion of reliability concepts

Reliability Engineering consists of the management and engineering tasks needed to specify, plan, manage,achieve and measure a product reliability.

The term "reliability" as used in this document considers reliability in its broadest sense and comprises allaspects that ensure the product continues to meet its availability requirement. Availability performance is notonly affected by product reliability but by maintainability performance and maintenance support strategies. Themethod of providing maintenance support varies from customer to customer depending on if a maintenanceagreement is made and the type of agreement.

In Figure 1., reliability (dependability) aspects and their relationships are presented in accordance with thedefinitions of international standard IEC 50(191).

Figure 1: Dependability concepts.

Dependability

The collective term used to describe the availability performance and its influencing factors: reliabilityperformance, maintainability performance and maintenance support performance. This term is often replaced

by “reliability” term.

Availabili ty performance

The ability of an item to be in state to perform a required function at a given instant of time or at any instant oftime within a given time interval, assuming that the external resources, if required, are provided.

Reliability performance

The ability of an item to perform a required function under given conditions for a given time interval.

Maintainability performance

The ability of an item under stated conditions of use, to be retained in, or restored to a state in which it canperform a required function, when maintenance is performed under given conditions and using statedprocedures and resources.

Sharenet 445958/3.0 Proprietary and Confidential 4 (18 )








Maintenance support performance

The ability of a maintenance organization, under given conditions, to provide upon demand the resourcesrequired to maintain an item, under a given maintenance policy.

2.2 Reliability terminology and calculation principles

Reliability of BTS system and modules is typically expressed with next terminologies and calculation formulas.Please note that terminologies and calculation principles can differ between organizations and reliabilitystandards. To avoid conflicts between contract participants, the details of terms need to be understood andclarified more exactly to avoid misreading.

Mean (operating) Time Between Failures (MTBF) The expectation of the operating time duration between two consecutive system failures of a repaired item.Only the failures that affect to system traffic capacity are included.

System MTBFSystem MTBF indicates the expected failure rate for the defined configuration. MTBF value is stated for the fulland partial sector capacity in nominal cases.

MTBF for Repair comprises all failures requiring repair whether they affect the system functionality or not. Itsummaries the parts FITs (Failure In Time) and indicates the probability for unplanned site visit.

Mean Repair Time (MRT)The expectation of active corrective maintenance time when repair actions are performed for an item. Consistof module replace time with actions to perform the replacement and power-up the module to initial state.

• Flexi BTS MRT = 0.5 hours (30 minutes)

Mean Time To Recovery (MTTR)The expectation of the time interval during which an item is in a down state due to a failure. MTTR includesmean active repair time (MRT) and logistical and administrative delay times (MLD).

Due to differing national conditions, logistic delay times may vary from country to country and therefore maynot be subject to international recommendation. Therefore the availability performance values are calculatedbased on the active repair time only (MRT). MTTR is expressed in some standards as Mean Time ToRestoration (same as Recovery), but also as Mean Time To Repair. To avoid conflicts, it is necessary tounderstand differences between operational and intrinsic availability.

Availabili ty (A) is the intrinsic availability ( A i) at time infinity for a mature product and assumes an ideal

maintenance and operational conditions. Intrinsic availability includes only the active repair times (MRT) andexcludes logistic delays caused by traveling, spare part availability and preventive maintenance actions, whichare part of logistical delays (MLD). Intrinsic availability is sometimes spoken as inherent availability and issimilar to steady-state availability.

• Operational availability ( Ao) can be calculated to represent total system downtime, but because thelogistical delays depends on the operators maintenance actions, it is not relevant in the predictions.

Intrinsic availability ( A i) calculation formula and parameters:

A i = MTBF / (MTBF + MRT)

• MRT (Flexi BTS) = 0.5 hours (30 minutes)

o To calculate operational availability (Ao) and total downtime, next formula andparameters shall be used.

Ao = MTBF / (MTBF + MTTR)








MTTR = MRT + MLD

MLD (Mean Logistical Delay) = 4,0 hours (average estimation).

Unavailability (U) presents the value to condition when a system is down and is used for mean down timecalculation.

U = 1 - Ai

Mean Down Time (MDT)The expectation of the time interval during which an item is in a down state and cannot perform its function.MDT is calculated from the inherent availability including only the active repair times (MRT) and excludeslogistic delays caused by traveling, spare part availability and preventive maintenance actions, which are partof logistical delays (MLD). Typically it is calculated in annual bases.

MDT [min/year] = U * 8760h/year *60 minutes/h

LifetimeDesign lifetime (design life, useful life) defines the expected minimum time for design functionality. Starts whenthe design is first time taken into use and continues without interruption to failure when the design is notanymore possible to repair with reasonable costs. Lifetime and MTBF are two separate terms and not confidedto each other. Typically MTBF should be must higher than lifetime.

Lifetime is defined for a large population installed components in service, not for a single component. Lifetimeis expressed often as design life and service life and it is not same than a product life span or life-cycle.

MTTFMedian Time To Failure is the time from the moment of installation to the point when 50% of the componentpopulation have failed. This time is longer than the lifetime defined at a low failure probability.It is used for the components whose lifetime distribution is relatively narrow. MTTF is most relevant parameterfor non-repairable parts and must be much higher than whole product lifetime.

L10 lifeThe L10 specifications states that less than 10% of a statistically significant numbers of cooling fans or similarkind of equipment will fail before the L10 life expectation in the specified conditions. Cooling fans containstypically both electrical and mechanical parts and because of the electrical parts, is it usual to define relevantMTBF for the fan also to estimate spare part need. L10 life need to be higher than the specified lifetime.Typically L10 is the value for rotor life in cooling fan design.








3. RELIABILITY METHODS TO OPTIMIZE DESIGN FUNCTIONALITY

To optimize a design robustness and possibility to maintain certain capacity level in the failure cases, it ispossible to use several design techniques.

3.1 Redundancy

Reliability predictions based on the module, unit and system level Reliability Block Diagrams (RBD) and takeaccount unit and module level redundancy, which have significant effects on the complete system'sfunctionality.Redundancy can be performed on next ways.

Duplication: If the spare unit is designated for only one active unit the software in the unit pair is keptsynchronized so that taking the spare in use in fault situations (switchover) is very fast. The spare unitcan be said to be in hot standby. This redundancy principle is called duplication, abbreviated "2N".

Replacement: For less strict reliability requirements, the one or more spare units may also bedesignated to a group of functional units. One spare unit can replace any unit in the group. In this casethe switchover is a bit slower to execute, because the spare unit synchronization (warming) isperformed as a part of the switchover procedure. The spare unit is in cold standby. This redundancyprinciple is called replacement, abbreviated "N+1".

Load sharing: A unit group may be allocated no spare unit at all, if the group acts as a resource pool.The number of units in the pool is selected so that there is some overcapacity. If a few units of thepool are disabled because of faults, the whole group can still perform its designated functions. Thisredundancy principle is called load sharing, abbreviated "SN+" or "N+1/L"

Some functional units have no redundancy at all (do not need to be backed-up). This is because theyare otherwise protected or offer non-critical services or a failure in them does not prevent the functionor cause any drop in the capacity.

3.2 Recovery functionality

To optimize BTS functionality it contains several recovery and remote control functionalities. Most commonrecovery actions are:

• Restart:o Self-reset or forced reset to recover in the failure cases.

• Diagnostics features:o Self-test and loop-tests to detect functionality errors.o Alarm generation in the error cases (internal and BTS level alarms).

• Temperature control with alarm to shut down module or reduce electrical stress if overheated.

3.3 Remote controllability

Every BTS and most of its modules are possible to control remotely to avoid site visits. Remote connectioncan be take by using specific element manager or from other core network element.








4. FLEXI MULTIRADIO BTS RELIABILITY PRINCIPLES

4.1 Standard reliability functionaliti es

Flexi WCDMA and LTE BTSs hava designed to achieve optimum reliability performance on system level. Thedesign contains functionalities, which maintain operability in error and failure cases. During the R&D workseveral actions have been completed to achieve optimum reliability level.

4.2 Reliability performance optimization during R&D work

Flexi BTS is highly integrated and high capacity BTS in small size. When combining functionality of severalmodules to one entity, it increases critical parts amount and thus number of single point failures in thatpackage. Benefit of high integration level is that it makes possible to combine certain functionalities to one partand reduce signal routing between parts and sub-modules. This reduces component and connection amounts.This is one reason for better HW-reliability expectations, because the design contains less parts and contacts,

risk for HW-level failures is smaller. HW-level reliability (MTBF for repair value) can be expected to be aboutthree times better than in older BTS’s in minimum. This will be seen in reduced site visit needs.

High integration level improves the system level reliability performance also, but there the improvement is notso significant as in the part level HW-reliability.

Small size and high RF-power makes temperature behavior more critical and that is emphasized in R&D workas well actions to ensure good durability of mechanical design.

Normal R&D work contain several actions to ensure adequate design margins and verify the reliabilityperformance.

Component and material selection. All the materials are selected to fulfill durability over 10 years lifetime.

Derating. To ensure the components functionality over the design lifetime their accepted electrical stress isanalyzed and limited to safe performance level when seen reasonable.

Thermal design. The design internal temperature behavior is verified and design actions completed to keepthe components thermal stress in safe level. This contains the active components junction temperatureanalysis as part of derating analysis and reliability testing to verify results.

Failure modelling and r isk analysis. The design failure modelling and risk analysis starts in the beginning ofthe design work to prevent or minimize the design risk.

Reliability testing. Module and system level reliability testing is completed to verify the design functionality inthe specified conditions and ensure adequate margins for the limits. Typical reliability testing contains different

kind of accelerated or highly accelerated life tests (ALT/HALT), which are completed for functional designduring the R&D-phases.

Trialing and piloting. All new products are in normal cases taken to trial or pilot tests in the real fieldconditions to ensure their maturity before volume production.

4.2.1 HW reliability

HW-reliability means the actions to prevent field failures caused by mechanics and electrical HW-design.

• Redundancy. To minimize single point failures and minimize severity of most critical failures, it isanalysed possibilities to duplicate functionality in the design. Redundancy can be arranged bypooling the baseband capacity and arrange redundant RF-paths (diversity and parallel RF-parts).

• Baseband pooling. All the signal processing is in the pool ensuring flexible baseband capacityusage (Rel.2 feature).








• Thermal protection.

o

Mechanical thermal design to optimize location of high thermal parts in the cooling optimizedchassis.o Possibility to use cooling fans for forced air routing with adjustable rotation speed.o Internal temperature sensors for over-temperature protection to be used for temperature alarm

and for module shut down or electrical stress reduction.o Over-voltage and short circuit protection.o Prevention to install modules for wrong slot or cables to wrong connection.

4.2.2 Software reliability

• BTS diagnostics. Modules and BTS SW contains internal diagnostics to trace functionality,perform recovery actions and make possible to detect failed part.

• Recovery actions:

o Alarms. In the failure cases modules are able to send an alarm messages to start internal orexternal failure action.

o Self-tests (BIST) are run in the start-up’s and in some cases in via element manager to verifyfunctionality and detect possible failure.

o Automatic or forced restarts are possible to run to get module or BTS to initial state.

• Remote control. Possibility to control and run recovery actions for BTS from the other networkelement or locally by using the element manager or other special tool and connection.

• Special features:

o Memory handling to prevent exceeding of memory budget.o Storing of old memory until new release is loaded and activated correctly with data check.

o Task monitoring and rejuvenation.o Saving the internal reporting (log information) for later analysis purposes.








5. FLEXI MULTIRADIO BTS SYSTEM RELIABILITY

Estimated reliability of Flexi Multiradio BTS for the main configurations is presented in this chapter.

Estimated values contains the values of MTBF dependency to the RF-power. That is explainedmore in chapter 5.5.

o Tables in this chapter presents the predicted values for most common configurations.MTBF values in table are hours/years.

Redundancy is taken account in system level calculations, more details in chapter 5.3.1.

All the values are calculated for +25°C ambient temperature. Temperature effect to MTBF ispresented in graph 1 in chapter 5.4.

For transmission modules it is used one typical value, which is based on the FTEB values.

5.1 Flexi WCDMA BTS (HW Release 1) Reliabi lity Performance

BTS Configuration System MTBF

3-sectors of 3

System MTBF

2-sectors of 3

1+1+1@ 20/40W

FSMB + 2-sector RF + 1-sector RF

80 000 h 120 000 h

BTS Configuration System MTBF3-sectors of 3

System MTBF2-sectors of 3

2+2+2@ 20W

2*FSMB + 2-sector RF + 1-sector RF

50 000 h 140 000


3-sectors of 3

System MTBF

2-sectors of 3

2+2+2 @ 40W

2*FSMB + 3x 2-sector RF

50 000 h 140 000


3-sectors of 3

System MTBF

2-sectors of 3

1+1+1 @ 20W

FSMB + 3x 1-sector RF

70 000 h 160 000














5.2.6 Redundancy and capacity definit ions in Flexi Mult iradio BTS

Flexi Multiradio BTS contains redundancy in System Module, RF Modules and Remote Radio Heads. SystemModule has redundancy with two parallel signal processor cards in FSMD and tree cards in FSME. Basebandcapacity (BB capacity) in system values is calculated in every case for > 50% capacity allowing one signalprocessor card failure in FSMD or FSME.

RF Module internal redundancy is in the form of parallel identical TRXs. 3-sector RF Module is able tomaintain 67% RF capacity if one sector fails. With two 3 sector RF Modules is possible to have full 1+1redundancy for 3-sector BTS site.

New 2TX RRH has internal redundancy in the form of two parallel identical TRXs. RRH is able to maintain50% RF capacity if one TRX fails.

Redundant two System Module configuration requires redundant System Module feature, please checkWCDMA or LTE release roadmap.

Next pictures clarifies redundancy principles in BTS reliability calculations.

FSMD

250

BB - Common

250

FSMD

BB

BB - Common

BB

FSME

250

BB -Common

250 250

FSME

BB

BB -Common

BB BB

BB- capacity

2 baseband cards100% = Both cards inuse.>50% = One card inuse.

BB-capacity

3 baseband cards100% = All 3 cards in use.>50% = Two cards in use.

Figure 2: System Module capacity principles from reliability point of view

Dual TRX

Common

RX RX

TXY

RX RX

TXY

Dual TRX

Common

RX RX

TXY

RX RX

TX

RX RX

TXY

RX RX

TXY

RX RX

TX

RX RX

TXY

RX RX

TXY

Triple TRX

Common

RX RX

TXY

RX RX

TXY

RX RX

TXY

RX RX

TX

RX RX

TXY

Triple TRX

Common

RX RX

TXY

RX RX

TX

RX RX

TXY

RX RX

TXY

RX RX

TX

RX RX

TXY

Single TRX

Common

RX RX

TXY

Single TRX

Common

RX RX

TXY

Common

RX RX

TXY

RX RX

TX

RX RX

TXY

RF-capacity

100% = Div

RX can fail

≥ 50% = NA

RF-capacity

100% = “Div RX can fail

≥ 50% = 1 of 2 TRX

works

RF-capacity

100% = Div RX’s can fail

> 50% = 2 of 3 TRX works

Figure 3: RF Modules and RRHs RF capacity principles from reliability point of view

5.2.7 System Availabi lity and Downtime

The presented systems intrinsic availability Ai is expected to be 99.999% in minimum for the conditionsmentioned in the chapter 5.3 and calculated with formulas defined in chapter 2.2.

Five nines (99.999%) availability is indicating better than 5.5 minutes yearly downtime (M AIDT).









5.3 Prerequisites and assumptions for predicted data

When the field failure rates (MTBF) are compared to predicted value, it is absolutely necessary to notice thedifference of component failures used in prediction and the field failures. To make the field MTBF valuecomparable to predicted one, it is needed to use next restrictions for data:

• Module must have about 10 000 000 hours (1 100 years) field use hours before the field results is ableto state accurate enough MTBF level.

o This can be reached when > 1000 modules is one year on the field.

• Predicted value is valid during the product lifetime only (BTS 10 years).

• Failure rates (MTBF) are defined for electrical parts only and typically only for repairable items. Non-repairable items reliability is assumed to fulfill 10 years lifetime if not otherwise stated and they are notincluded to predicted value typically.

• Predicted values are valid in the calculation conditions only, not in the product specified conditionsdirectly.

o BTS air (ambient) temperature, which is used based on the common climate conditions:• Humid Temperate, average +15 C.

• Warmest month > 10 C (> 50 °F).

• Coldest month > 0 C but < 18 C (> 32 °F but < 64.4 °F ).

• Most populated, about 55 % of world's population.

• Like Mid-European, Mediterranean, Mid Asia and North-America costal climates.

• Value is also valid for typical air-conditioned indoor site.

• Tropical/Sub-tropical climate, average +25 C.

• Coldest month > 18 C (> 64.4 °F ).

• Like South Asia, most India and equator climates.

• Daily and annual temperature range about +10…+50°C.o Assumes an average RF-output power.

•

Long-term RF-power load about 50% of maximum.o Operating more than 30 minutes in temperatures over +40°C is not recommended to avoid

errors or total failure in operation.

• Excludes the failures, which are not direct design weaknesses.o “No Fault Found” (NFF’s).o External and misuse failures.

• Equipment handling and usage errors.

• Failures caused by other network element or external system.

• Excludes systematic failures caused by 3rd party.o Systematic part failures caused by manufacturer process weakness.

• Cooling fans are included if not otherwise stated.

For selected units for which MTBF for repair values are not relevant (like non-repairable items mostly), design

lifetime, MTTF (Mean Time To Failure) or L10 life or similar life values are given. It is expected that non-repairable items can work in normal conditions over the product lifetime.








5.4 Temperature trend for system MTBF and thermal protectioning

Next graph is showing an average temperature trend for system MTBF. It is based on the module levelthermal analysis. Thermal analysis is done for the worst case conditions and assumes the maximum RF-power in the maximum temperature.

Fanless modules are usually more critical for temperature rise, but with derating, component selection andmechanical design structure solutions their thermal stress can be kept near the modules with fans. Moduleswith cooling fans have higher and more stable raliability performance over the design lifetime. In highertemperatures cooling fans enforce the air flow and keep the module internal temperature lower whencompared to fanless module.

BTS modules are equipped with thermal protectioning. It’s purpose is to detect an over-heating condition,create temperature alarm and reduce RF-power and capacity at first step. If temperature safe limit isexceeded, module is shut-down to avoid permanent design failure. Module and system should start to operate

after possible thermal shut-down immediately when the safe conditions are restored.

NSN uses the +25°C temperature as a reference temperature. That temperature corresponds in outdoor

conditions the tropical climate, where daily temperature can rise over +40°C on day time and be less than

10°C during night time. That temperature is most common for indoor sites also as a constant temperature. It isassumed that more than 50% of BTS sites are locating in more favourable climates than tropical one (sub-tropical and moderate) and presented value should cover all normal site locations.

MTBF

x 0.5

< +15 +25 + 40 + 55 °C

x 1.3

x 1.0

x 1.8

Module with fans

Module

without fans

x 0.7

MTBF

x 0.5

< +15 +25 + 40 + 55 °C

x 1.3

x 1.0

x 1.8

Module with fans

Module

without fans

x 0.7

Graph 1. Effect of BTS ambient temperature to the system MTBF in average.









5.5 RF-power effect to the system MTBF

Next graphs are showing the average RF-power effect of RF Modules and RRHs. Higher RF-power increasesthe RF Module and RRHs internal temperatures and thus reduces the MTBF on some part. Because site andBTS usage conditions are different often, it is impossible to prove an exact model for RF-power level andsystem reliability dependencies.

In BTS systems, where the System Module is also included, the effect of RF-power is lower. That is presentedin graph 3.

RF-power effect to MTBF is lower from 40W to 60W mode, because thermal design has been optimized forhigh temperatures to avoid permanent component failures and more stable system functionality in hot climateareas.

20 W 40 W 60 W RF-power

MTBF

x 1.0

x 1.20

x 1.5

x 0.7

RF Module

RRH


MTBF

x 1.0

x 1.20

x 1.5

x 0.7

RF Module

RRH

MTBF

x 1.0

x 1.20

x 1.5

x 0.7

RF Module

RRH

Graph 2. The RF-power effect to the module MTBF in average, 60W module.










MTBF

x 1.00

x 1.10

x 1.3

x 0.85

RF Module

RRH


MTBF

x 1.00

x 1.10

x 1.3

x 0.85

RF Module

RRH

Graph 3 The RF-power average affect to the system MTBF, 60W module.

Note! 40W RF behaves similarly to 60W and graph is valid to 40W module assuming samechange from 40W to 60W.

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18_Reliability and Redundancy of Flexi Multiradio BTS

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