Umts Possible Cause

7/29/2019 Umts Possible Cause

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What are the possible causes for an IRAT Failure?

There are several reasons for IRAT failure in cellular network optimization.Major 4 reasons which played good role inWCDMA Optimization.

Missing 2G relations

Non availability of 2G Resources

Poor 2G Coverage

Missing 3G Relations

What are the possible causes for a Drop Call on a UMTS

network?There are several reasons for RAB Drop in WCDMA network.

Poor Coverage (DL / UL)

Pilot Pollution / Pilot Spillover Missing Neighbor

SC Collisions

Delayed Handovers

No resource availability (Congestion) for Hand in

Loss of Synchronization

Fast Fading

Delayed IRAT Triggers

Hardware Issues

External Interference

hat is a typical soft handover gain in your link budget?

CS-12.2k: 3dB (UL), 2dB (DL)

PS-64k: 1dB (UL), 0dB (DL)



Know more about

ief describe the advantages and disadvantages of soft handover?Advantages:

Overcome fading through macro diversity.

Reduced Node B power which in turn decreases interference and increases

capacity. Reduced UE power (up 4dB), decreasing interference and increasing battery

life.

Disadvantages:
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UE using several radio links requires more channelization codes, and more

resources on the Iub and Iur interfaces.

More Dowload For You:

hat are the processing gains for CS and PS services?CS12.2: 25dBPS-64: 18dBPS-128: 15dBPS-384: 10dB

HSDPA: 2dB

hy is Eb/No requirement lower for PS than for CS?PS has a better error correction capability and can utilize retransmission,therefore it can afford to a lower Eb/No. CS is real-time and cannot toleratedelay so it needs a higher Eb/No to maintain a stronger RF link.

Explore More:

E Book on WCDMA for UMTS NetworksDownload WCDMA IRAT Handover Document.Good Discussion Topic on Congestion Control

What is Eb/No?By definition Eb/No is energy bit over noise density, i.e. is the ratio of theenergy per information bit to the power spectral density (of interference andnoise) after dispreading.

Eb/No = Processing Gain + SIR

For example, if Eb/No is 5dB and processing gain is 25dB then the SIR shouldbe -20dB or better.

Lots people have some confusion related to RSCP,RSSI and EcNo.

Here is the solution.

RSSI is Rx level before descrembling. Its just RxLev of UARFCH.

Discuss Your Optimization Problem at Our Forum

CPICH_RSCP is Rx level after descrembling.

CPICH_Ec/No is result of filtering after dechanalization.

In dBm is:RSCP=RSSI+EcNo

If I am wrong than Discuss it here
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Small Steps to Helping Friends..Keep Reading

If you are interested to write this type of article than write to us [email protected]

Tagged EcIo, EcNo, RSCP, RSSI. Bookmark the permalink.

What is SIR?What is SIR?

SIR is the Signal-to-Interference Ratio the ratio of the energy indedicated physical control channel bits to the power density of interference andnoise after dispreading.

How Power Control is implemented in HSDPA?Initial Power is set in the same way as open Loop Power control of DCH &

there is no further power control onHSDPAShared Channel HS-DSCH. The

Channel Rate is controlled by adaptive modulation & coding formats.

The principles and functionality of the power control for

theHSDPAassociated dedicated channels are the same as for the DPCH

power control.

HS-DPCCH power is an offset relative to DPCCH depending upon whether the

UE is in soft handoff or not.

The Power for HS-SCCH is fixed.

How is Initial RACH Power is calculated?

The initial power on the PRACH - the power of the first preamble - is determinedaccording to equation

P_PRACH = L_PCPICH + RTWP + constantValueCprach

Where L_PCPICH is the path loss estimated by UE since it knows transmit &receive CPICH power RTWP is received Total Wideband Power(uplinkinterference) measured by RBS .constantValueCprach is used by the UE to calculate the initial power onthe PRACH . This parameter is configurable and decides at which level below

RTWP preamble ramping will start.

DownloadUMTS KPI Introduction Doc

What is a typical CPICH power?

CPICHpower typically takes about 8~10% of the total NodeB power. Fora 20W (43dBm) NodeB,CPICHis around 2W (35.1 ~ 33dBm).
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In urban areas where in-building coverage is taken care of by in-buildinginstallations, theCPICHmay sometimes go as low as 5% because:1) The coverage area is small since users are close to the site, and2) More power can be allocated to traffic channels

ow much power usually a NodeB is allocated to controlchannels?

The power allocated to control channels may depend on equipmentvendor recommendation. Typically no more than 20% of the total NodeB poweris allocated to control channels, includingCPICH. However, ifHSDPAisdeployed on the same carrier then the total power allocated to control channelmay go up to 25 to 30% because of the additionalHSDPAcontrol channelsrequired.You might also like:

ow does UE camp (synchronize) to a NodeB?1. UE uses the primary synchronization channel (P-SCH) for slot alignment (TSsynchronization).2. After aligning to NodeB time slot, UE then uses secondary synchronization

channel (SSCH) to obtain frame synchronization and scrambling code groupidentification.

3. UE then uses scrambling code ID to obtain CPICH, thus camping to a NodeB.

Online 3G Tutorial

How many slots are there in a WCDMA Frame? How big is aframe in ms. how many chips are there in a slot?

WCDMA Frame is 15 slots wide. It is 10ms in length. There are 2560 chips inone slot. Chip rate is 3840 Kc/sLength of frame = 10 msNumber of chips in a frame = 3840 *10=38400 chips.Number of chips in a slot = 38400/15= 2560 chips

How many channelization codes are available?The number of channelization codes available is dependent on the length of

code. In the uplink the length is defined as between 4 and 256. In thedownlink the length is defined as between 4 and 512.

Know more about Scrambling Code

What is channelization code?
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Channelization codes are orthogonal codes used to spread the signal and hence provideschannel separation, that is, channelization codes are used to separate channels from acell.

What is the usage of Channelization code in downlink and

uplink?

Uplink separation of physical data (DPDCH) and control channel (DPCCH) fromsame terminal.Downlink separation of downlink connections to different users within one cell.

s UMTS an Uplink limited or Downlink limited System?

Initially, A typical WCDMA network is Uplink Limited. Later a Loaded Network becomesDownlink Limites.

Downlaod Document on RRC KPIs

When is System information sent to UE?

The system information is regularly broadcast to the UE on the BCCH. When aparameter in the system information is changed, all UE in a cell are notified by apaging message or by a system information change indication message.You might also like:

What is Hard Handover in UMTS? When will it happen?

What are different Idle mode tasks UE performs?

What can we try to improve when access failure is high?

Is UMTS an Uplink limited or Downlink limited System?

What is a typical UE sensitivity level?LinkWithin

Posted byTele Talkat7:40 AM

What is a typical UE sensitivity level?The service and load determines the UE sensitivity; in general, in no-loadcondition, the sensitivity is between -105dBm and -120dBm. For Ericsson, theUE sensitivity level is calculated at around:

CS12.2: -119 dBm

PS-64: -112 dBmPS-128: -110 dBmPS-384: -105 dBmHSDPA: -95 dBm

enefits ofCPICH Optimization

Improving current 3G coverage and increase 3G traffic

Improve in-building penetration for 3G
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Reduce IRAT HO to 2G

Offload traffic from 2G layer

You might also like:

Pilot Channel failure - High Downlink Interference

CPICH Optimization

What is a typical CPICH power? What is a typical CPICH power?

HSDPA Frame LossLinkWithin

Posted byTele Talkat5:44 PM

HSDPA Frame LossThese counters relating to frame loss are available on the RBS to monitor HighSpeed data service in

the downlink direction.

IubDataStreams::pmHsDataFramesLostSpiXX

- the number of HSdata frames lost, destroyed and errored over Iub in the RBS. There areseparatecounters for each of the priority classes.

IubDataStreams::pmHsDataFramesReceivedSpiXX- the totalnumber of HS data frames correctly received over Iub in the RBS. Thereare separate

counters for each of the priority classes.

The XX suffix represents the priority class and can range from 00 to 15.The counters can be used toindicate data loss rate for the HS service.High frame loss will indicate potential congestion problems.

RecommendedPerformance Indicator for this is:

What are Events that can trigger the HSDPA Cell Change?Event 1d HS Change of Best Cell in the Active SetEvent 1b or Event 1c Removal of the Best Cell from the Active Set

What is Eb/No requirement for HSDPA?The Eb/No requirement forHSDPAvaries with user bit rate (data rate),

typically 2 for768kbps and 5 for 2Mbps.

Frame Loss Rate on the path from SRNC to RBS

What Resources are monitored for Capacity Management?
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Simple definition of Pole Capacity

Power control In WCDMA

What is the family of codes used for Chanelization in WCDMA?

What are the major differences between GSM and UMTS handover?


hat are the Eb/No targets in your design?The Eb/No targets are dependent on the service: On the uplink, typically CS is 5 to 6dB and PS is 3 to 4dB PS is about

2dB lower.

On the downlink, typically CS has 6 to 7dB and PS is 5 to 6dB PS is

about 1dB lower.

ilot Channel failure - High Downlink InterferenceSymptoms:

From the drive test, following symptoms will be observed by usingTEMS: Received Ec/No of the pilot channel is less than 16dB and

Received RSCP of the pilot channel is high enough to maintain the connection,e.g. > - 100dBmand

DL RSSI is very high and The connection finally drops.

Good Excel Sheet onCPICH Calculator

Reason 1

no dominant cellSolution:The most direct and effective way to solve this problem is to increase the

pilot channel powerPrimary CPICH powerof the desired cell.

Reason 2 dominant interfererSolution:The simplest solution to overcome this problem is to include the

overshooting cell into the neighboring cell list. This means the interferer now

becomes a useful radio link.

Reason 3 low best serving PPilot/PTotSolution:The received Ec/No of the best serving pilot channel is very low (near or

less than16dB) even though there is no other cell. It means the pilot power setting is

not large enough to fulfill existing downlink load.

Solution 1The best solution is to add a new site with good coverage control at the problematic

area.

Solution 2The direct but ineffective solution is to increase the pilot channel power
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PrimaryCPICH power of the problematic cell.With high pilot power, the common

channel powers and the required power for the downlink DPCHs will be increased. At

the end, the ratio of the PPilot/PTot does not increase much.

What is Pilot Pollution?Simply speaking, when the number of strong cells exceeds the active set size,there is pilot pollution in the area. Typically the active set size is 3, so if

there are more than 3 strong cells then there is pilot pollution.

Definition of strong cell: pilots within the handover window size from thestrongest cell. Typical handover window size is between 4 to 6dB. For example,if there are more than 2 cells (besides the strongest cell) within 4dB of thestrongest cell then there is pilot pollution.

Cell selection is based on:

Qmean: the average SIR of the target cell.

Qmin: minimum required SIR.

Pcompensation: a correction value for difference UE classes.

S = Qmean - Qmin - Pcompensation

If S>0 then the cell is a valid candidate.

A UE will camp on the cell with the highest S.

What do you understand by Directed Retry? When there is a co-existing GSM RAN, excess traffic in aWCDMAcell

may be offloaded to GSM If a call is chosen for Directed Retry to GSM,

the request for the speech RAB will be rejected with cause "Directedretry" and then a request is made to the core network to relocate the

UE to a specific GSM cell, using the Inter-RAT handover procedure.This handover is a blind one since the target cell is chosen not based

on UE measurements. Therefore, the target cell must be co-locatedwith theWCDMAcell. Co-located GSM cells are assumed to have

similar coverage and accessibility as their respectiveWCDMAcells.

What do you understand by CQI Measurements? Channel Quality Estimation (CQI) for HSDPA sessions only.

In order to aid scheduling and TFRC selection in the RBS, the UE sends a

channel quality indicator (CQI) report on the uplink.

The CQI report estimates the number of bits that can be transmitted to
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the UE using a certain assumed HS-PDSCH power with a block error rate

of 10%.

What do you understand by DRX cycle?

The UE listens to the PICH only at certain predefined times, reducing

power consumption. The periodicity of these searches is set by thesystem and the time interval is called Discontinuous Reception (DRX)

cycle. Different DRX cycles are used for circuit switched and packet switched

services in Idle mode. A separate DRX cycle is also used to pageConnected mode UEs in state URA_PCH.


What effect is there on signal by spreading and

dispreading?

Spreading will increase the bandwidth of a as signal. A signal of 10Kb/s will become 40 Kb/s after spreading and will become 10 Kb/s after

despreading. The processing gain term expresses the gain achieved byspreading a narrow band signal over a wideband spectrum.

This gain is the ratio between the spreading chip rate and the actualservice bit rate measured at the RLC level.


What is Cell Breathing and why? The cell coverage shrinks as the loading increases, this is called

cell breathing.

In the uplink, as more and more UE are served by a cell, each UE needs

to transmithigher power to compensate for the uplink noise rise. As a

consequence, the UEwith weaker link (UE at greater distance) may not

have enough power to reach theNodeB therefore a coverage shrinkage.

In the downlink, the NodeB also needs to transmit higher power as more

UE arebeing served. As a consequence UE with weaker link (greater

distance) may not bereachable by the NodeB.

How Power Control is implemented in HSDPA? Initial Power is set in the same way as open Loop Power control of

DCH & there is no further power control onHSDPAShared ChannelHS-DSCH. The Channel Rate is controlled by adaptive modulation &

coding formats.

The principles and functionality of the power control for

theHSDPAassociated dedicated channels are the same as for the

DPCH power control.

HS-DPCCH power is an offset relative to DPCCH depending upon
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whether the UE is in soft handoff or not.

The Power for HS-SCCH is fixed.

What HS Channels are introduced in HSDPA in L1? HS-PDSCH High Speed Physical Downlink Shared Channel

HS-SCCH High Speed Shared Control Channel

What are different Idle mode tasks UE performs?

In Idle mode, the UE has no connection to the radio network.Keeping UEs in

Idle mode minimizes the use of resources both for the UEs and in the network.However, the UEs must still be able to access the system and be reached by the

system with acceptable delays. For this, the following procedures need to beperformed.

PLMN selection and reselection Cell selection and reselection

Location Area (LA) and Routing Area (RA) updating

Paging

System information broadcast

What is Compressed Mode?

Compressed mode is a physical layer function that allows the UE to

temporarily tune to another frequency, and measure the RF

environment of another UMTS frequency (e.g. IFHO) or anothertechnology (e.g. IRAT), while maintaining an existing dedicated

channel.

hat is the typical event sequence of IRAT Handover from

3G to 2G Simple IRAT Handover Flow

Event 2d entering into compressed mode measurement of 2G

candidates Event 3a Verification of 2G resources

Handover from UTRAN Command from 3G RNC to UE

What is the typical Call Setup Time for a 3G UE to 3G UE Call?

What are the possible RF related causes for a delayed CST in

this type of call? 6 to 9 seconds

Multiple RRC Attempts (UE is on poor coverageneed more than Access Attempt)


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Delayed Page Responses

High Load on Paging and/or Access Channel

Paging / Access Parameters

What is Paging Success Ratio? What is the typical PSR that

you have seen in a WCDMA UMTS network?

Paging Success Ratio:

Its Paging Responces to the Paging Attempts in WCDMA UMTS network.

Typical Value for Good WCDMA Cellular Network is greater than 90%. You might also like:

What are the possible causes for a lower PSR? There are several different reason for low Paging Success Ratio

- Non-continuous RF Coverage UE going in and out of coverage area frequently

- Very High Periodic Location Update Timer Keeping UEs in VLR long time after

it moved out of coverage

- Lower Paging Channel Power

- Access Channel Parameter Issues

- Delayed Location Update when crossing the LA / CN Boundaries

What is the typical Call Setup Time for a 3G UE to 3G UE Call?

What are the possible RF related causes for a delayed CST in

this type of call? 6 to 9 seconds

Multiple RRC Attempts (UE is on poor coverageneed more than Access Attempt)

Delayed Page Responses

High Load on Paging and/or Access Channel

Paging / Access Parameters

What is Paging Success Ratio? What is the typical PSR that you

have seen in a WCDMA UMTS network?

Paging Success Ratio:

Its Paging Responces to the Paging Attempts in WCDMA UMTS network.

Typical Value for Good WCDMA Cellular Network is greater than 90%.


What are the possible causes for a lower PSR?
http://rfnetworkoptimization.blogspot.com/2012/03/what-are-possible-causes-for-lower-psr.htmlhttp://rfnetworkoptimization.blogspot.com/2012/03/what-are-possible-causes-for-lower-psr.htmlhttp://rfnetworkoptimization.blogspot.com/2012/03/what-are-possible-causes-for-lower-psr.html


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What are the typical KPIs you use to measure a network and what criteria?

What is the typical Call Setup Time for a 3G UE to 3G UE Call? What are the possible RF

related causes for a delayed CST in this type of call?

What is Soft Handover Overhead? What is the typical value in UMTS network?

What are the possible causes for a Drop Call on a UMTS network?

What are the typical KPIs you use to measure a network and

what criteria? Access failure rate ( 2%).

Call setup time (CS: over 95% of the time < 6-second for mobile-to

PSTN, 9-second for mobile-mobile. PS: over 95% of the time -100dBm and

DL RSSI is very high and

The connection finally drops.

Good Excel Sheet onCPICH Calculator

Reason 1 no dominant cellSolution:The most direct and effective way to solve this problem is to increase

the pilot channel powerPrimary CPICH powerof the desired cell.Reason 2 dominant interfererSolution:The simplest solution to overcome this problem is to include the

overshooting cell into the neighboring cell list. This means the interferer now

becomes a useful radio link.

Reason 3 low best serving PPilot/PTotSolution:The received Ec/No of the best serving pilot channel is very low (near

or less than16dB) even though there is no other cell. It means the pilot power

setting is not large enough to fulfill existing downlink load.

Solution 1

The best solution is to add a new site with good coverage control at theproblematic area.

Solution 2The direct but ineffective solution is to increase the pilot channel power

PrimaryCPICH power of the problematic cell.With high pilot power, the

common channel powers and the required power for the downlink DPCHs will

be increased. At the end, the ratio of the PPilot/PTot does not increase much.
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What is Pilot Polution? In idle or cell_FACH mode, phenomenon of the pilot pollution is that a UE cannot firmly

camp on a cell at one location because of receiving many pilot channels with similar quality

(or signal strength), i.e., Ec/No (or RSCP).The condition to determine the area has pilot pollution in idle or cell_FACH mode is that

third pilot appears in the cell re-selection region.In cell_DCH mode, phenomenon of the pilot pollution is that a UE at one location frequently

changes its active set cells (active set update rate is very high) because of receiving manypilot channels with similar quality (or signal strength), i.e., Ec/No (or RSCP). It causes highsignaling load in RRC and Iub interfaces and the capacity of RNC is consequently reduced.

May be useful to you

WCDMA Tilt and CPICH Power Adjustment

Solution for Pilot Polution in the network:

Reason no dominant cellThe reason is too many overlapping cells at an area due to poor cell planning.

Solution 1The direct solution is to remove the cells overlapping by changing the antenna configurations

or reducing pilot powers of the unwanted cells.

Solution 2The most effective solution is to increase the pilot channel power Primary CPICH power of

the desired cell.

Solution 3For the pilot pollution in idle or cell_FACH mode, Q Offset 2sn (CPICH Ec/No) parameterof the desired cell can be increased to create a dominated cell.

Benefits of CPICH OptimizationBenefits ofCPICH Optimization

Improving current 3G coverage and increase 3G traffic

Improve in-building penetration for 3G

Reduce IRAT HO to 2G

Offload traffic from 2G layer


Capacity Management and Its functions- WCDMACapacity Management is responsible for the control of the load in the cell.

It consists of 3 main functions:

1. Dedicated Monitored Resource Handling: tracks utilization of critical resources

ofthe system.

2. Admission Control: accepts/refuses admission requests based on the current

loadon the dedicated monitored resources and the characteristics of the request

3. Congestion Control: detects/resolves overload situations.

What Resources are monitored for Capacity Management?DL Power
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Received Total Wideband powerOVSF Codes

What Radio Measurements are used for Congestion Monitoring?Downlink Received Power

Uplink Received Total Wideband Power

What is the family of codes used for Chanelization in WCDMA?Family of codes used for Chanelization in WCDMA used is Orthogonal VariableSpreading Factor.(OVSF)

What Radio Measurements are used for Congestion Monitoring?Downlink Received PowerUplink Received Total Wideband Power

Simple definition of Pole Capacity

The pole capacity is the theoretical maximum capacity of the system.In WCDMA, this capacity is only theoretical since, once reached, the systemgoes in an instable state that leads to its collapse. However it is still a referencefor expressing the load.The uplink noise increases with the loading exponentially. When the uplinknoise approaches infinity then no more users can be added to a cell and thecell loading is close to 100% and has reached its pole capacity.Mathematically, to calculate the uplink pole capacity we need to know:

W: chip rate (for UMTS 3,840,000 chips per second)R: user data rate (assuming 12,200 kbps for CS-12.2k)

f: other-cell to in-cell interference ratio (assuming 65%)EbNo: Eb/No requirement (assuming 5dB)

AF: Activity factor (assuming 50%)Pole Capacity = (W/R) / ((1+f) * AF * 10^(EbNo/10)) = 120.6To calculate the downlink pole capacity we also need to know:: downlink channels orthogonality factor (assuming 55%)Pole Capacity = (W/R) / ((1- +f) * 10^(EbNo/10)) = 64.06You might also like:

How to calculate maximum number of users on a cell?To calculate the maximum number of users (M) on a cell, we need to know:

W: chip rate (for UMTS 3,840,000 chips per second)

EbNo: Eb/No requirement (assuming 3dB for CS-12.2k)

i: other-cell to in-cell interference ratio (assuming 60%)

R: user data rate (assuming 12,200 kbps for CS-12.2k)

: loading factor (assuming 50%)

Take 12.2kbps as example:


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M = W / (EnNo * (1 + i) * R) * = 3,840,000 (3 * (1 + 0.6) * 12,200) * 0.5 =

32.8

The number of users could also be hard-limited by OVSF code space. Take

CS12.2k for example:

A CS-12.2k bearer needs 1 SF128 code. Total available codes for CS-12.2k = 128 2 (1 SF64) 2 (4 SF256) = 124.

Consider soft-handover factor of 1.8 and loading factor of 50%: 124 / 1.8

*.05 = 34 uers/cell.

Consider downlink only, what are the major components in

calculating maximum path loss, starting from NodeB? NodeB CPICH transmit power.

Jumper and feeder connector loss.

Antenna gain.

Over-the-air loss. Building / vehicle penetration loss.

Body loss.

What is a typical maximum path loss?The maximum path loss is dependent on the service and vendor

recommendations; typically it is in between 135 to 140dB for urban areas and

between 150 to 160dB for rural areas.

How WCDMA OSS Works?

Doc For This with Below Containing : Cell & Channel Management

Adjacent Cell Configuration Management

Radio Network Optimization

WCDMA Neighboring Cell Support (WNCS)

WCDMA Measurement Result Recording (WMRR)

Alarms Status Matrix

Alarm Log Browser

Alarm List Viewer

Element Manager

RNC Element Manager

RBS Element Manager

Bulk Configuration C

How much power usually a NodeB is allocated to control

channels?
http://rfnetworkoptimization.blogspot.in/2011/09/how-much-power-usually-nodeb-is.htmlhttp://rfnetworkoptimization.blogspot.in/2011/09/how-much-power-usually-nodeb-is.htmlhttp://rfnetworkoptimization.blogspot.in/2011/09/how-much-power-usually-nodeb-is.htmlhttp://rfnetworkoptimization.blogspot.in/2011/09/how-much-power-usually-nodeb-is.htmlhttp://rfnetworkoptimization.blogspot.in/2011/09/how-much-power-usually-nodeb-is.htmlhttp://rfnetworkoptimization.blogspot.in/2011/09/how-much-power-usually-nodeb-is.htmlhttp://rfnetworkoptimization.blogspot.in/2011/09/how-much-power-usually-nodeb-is.html


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The power allocated to control channels may depend on equipment

vendor recommendation. Typically no more than 20% of the total NodeB

power is allocated to control channels, including CPICH. However, if

HSDPA is deployed on the same carrier then the total power allocated to

control channel may go up to 25 to 30% because of the additional HSDPA

control channels required.

ow does UE camp (synchronize) to a NodeB? 1. UE uses the primary synchronization channel (P-SCH) for slot

alignment (TS

synchronization).

2. After aligning to NodeB time slot, UE then uses secondary

synchronization channel (SSCH) to obtain frame synchronization and

scrambling code group identification.

3. UE then uses scrambling code ID to obtain CPICH, thus camping to aNodeB.

How much power usually a NodeB is allocated to control

channels?


vendor recommendation. Typically no more than 20% of the total NodeB

power is allocated to control channels, including CPICH. However, if

HSDPA is deployed on the same carrier then the total power allocated to

control channel may go up to 25 to 30% because of the additional HSDPAcontrol channels required.

RRC Establishment Cause DescriptionCause 0 Originating Conversational Call

Cause 1 Originating Streaming CallCause 2 Originating Interactive Call

Cause 3 Originating Background CallCause 4 Originating Subscribed traffic CallCause 5 Terminating Conversational CallCause 6 Terminating Streaming CallCause 7 Terminating Interactive CallCause 8 Terminating Background CallCause 9 Emergency CallCause 10Inter-RAT Cell re-selectionCause 11 Inter-RAT Cell change order

Cause 12 RegistrationCause 13 DetachCause 14 Originating High Priority Signaling
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Cause 15 Originating Low Priority SignalingCause 16 Call re-establishmentCause 17 Terminating High Priority SignalingCause 18 Terminating Low Priority SignalingCause 19 Terminating cause unknown

What could be the cause of soft handover failure? Undefined neighbors

One way Neighbor definition

UE issue

Resource unavailable at target NodeB

Inadequate SHO threshold defined

What can we try to improve when access failure is high?When access failure is high we can try the following to improve RACH performance:

Increase maximum UE transmit power allowed: Max_allowed_UL_TX_Power.

Increase power quickly: power_Offset_P0.

Increase number of preambles sent in a given preamble cycle: preamble_Retrans_Max.

Increase the number of preamble cycles: max_Preamble_Cycle.

Increase number of RRC Connection Request retries: N300.

w is inter-frequency Handover triggered?The network decides that inter frequency measurements need to be

performed and sends the MEASUREMENT CONTROL MESSAGE withMeasurement type set to Inter-Frequency measurements. Generally it will

set an Event as well along with the measurements. The following are list of

Events that can trigger Measurement Report. Event 2a: Change of Best Frequency

Event 2b: The estimated quality of the currently used frequency isbelow a certain threshold and the estimated quality of a non-usedfrequency is above a certain threshold

Event 2c: The estimated quality of a non-used frequency is above acertain threshold

Event 2d: The estimated quality of the currently used frequency is

below a certain threshold

Event 2e: The estimated quality of a non-used frequency is below acertain threshold

Event 2f: The estimated quality of the currently used frequency is

above a certain threshold

The Inter-Frequency Handover Evaluation bases its decision on P-CPICH

quality measures on the currently used frequency and on one or more non-used frequencies. If the evaluation result is positive, one cell on a non-usedfrequency is proposed to Inter-FrequencyhandoverExecution.
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Inter-Frequency Handover is a hard handover where the UE is ordered by

the network to tune to another frequency. This means that there will besmall interruptions in the data flow to and from the UE.

Power control In WCDMA Open Loop Inner Loop

Outer Loop

Open Loop Power control-The Open loop power control technique requires

that the transmitting entity measures the channel interference and adjusts itstransmission power accordingly. This can be done quickly, but the problem is

that the interference estimation is done on the received signal, and thetransmitted signal probably uses a different frequency, which differs from thereceived frequency by the systems duplex offset. As uplink and downlink fastfading (on different frequency carriers) do not correlate, this method gives the

right power values only on average.Inner Loop-In this method the received signal-to interference ratio (SIR) ismeasured over a 667- microsecond period (i.e., one time slot), and based onthat value, a decision is made about whether to increase or decrease thetransmission power in the other end of the connection. Note that the delayinherent in this closed-loop method is compensated for by making themeasurements over a very short period of time. The transmit power control(TPC) bits are sent in every time slot within the uplink and the downlink.There is not a neutral signal; all power control signals contain either an increaseor decrease command.Outer Loop-The outer loop power control functions within the base station

system, and adjusts the required SIR value (SIRtarget), which is then used inthe inner loop control. Different channel types, which can be characterized by,for example, different coding and interleaving methods, constitute a channelsparameters. Different channel parameters may require different SIRtargetvalues. The final result of the transmission process can only be known after thedecoding process, and the resulting quality parameter is then used to adjust therequired SIR value. If the used SIR value still gives a low quality bit stream,then the outer loop power control must increase the SIRtarget value. Thischange in the outer loop will trigger the inner loop power control to increase themobile station transmission power accordingly.

How many time Inner Loop Power Control happens and whattype of fading it compensates?

How many time Inner LoopPower Controlhappens and what type of fadingit compensates?Ans:1500Hz and compensates Fast Fading.
http://www.telecomfunda.com/forum/viewtopic.php?f=29&t=440http://www.telecomfunda.com/forum/viewtopic.php?f=29&t=440http://www.telecomfunda.com/forum/viewtopic.php?f=29&t=440http://www.telecomfunda.com/forum/viewtopic.php?f=29&t=440


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ow much power usually a NodeB is allocated to control

channels?


vendor recommendation. Typically no more than 20% of the total NodeB poweris allocated to control channels, includingCPICH. However, ifHSDPAisdeployed on the same carrier then the total power allocated to control channelmay go up to 25 to 30% because of the additionalHSDPAcontrol channelsrequired.You might also like:

UE MeasurementsIntra-frequency measurements: measurements on downlink physicalchannels at the same frequency as the active set. A measurement object

corresponds to one cell.

Inter-frequency measurements: measurements on downlink physicalchannels at frequencies that differ from the frequency of the active set. Ameasurement object corresponds to one cell.Inter-RAT measurements: measurements on downlink physical channelsbelonging to another radio access technology than UTRAN, e.g. GSM. Ameasurement object corresponds to one cell.Traffic volume measurements: measurements on uplink traffic volume. Ameasurement object corresponds to one cell.Quality measurements: Measurements of downlink quality parameters, e.g.downlink transport block error rate. A measurement object corresponds to one

transport channel in case of BLER. A measurement object corresponds to one

timeslot in case of SIR (TDD only).UE-internal measurements: Measurements of UE transmission power and UEreceived signal level.

UE positioning measurements: Measurements of UE position.The UEsupports a number of measurements running in parallel. The UE also supports

that each measurement is controlled and reported independently of every othermeasurement.

What is Soft Handover Overhead? What is the typical value in

UMTS network? Soft Handover Overhead is calculated in two ways. 1) Average Active Set SizeTotal

Traffic / Primary Traffic. 2) Secondary / Total Traffic

Typical Values are like 1.7 (Avg Active Set Size) or 35% (Secondary / Total )

Explain Soft and Softer handover? Give some advantage

and disadvantage for soft handover
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In Soft Handover, the UE connection consists of at least two radiolinks established with cells belonging to different RBSs. In Softerhandover, the UE connection consists of at least two radio linksestablished with cells belonging to the same RBS.

It acts as macro diversity since UE is connected to more than one radio

link at any given point, adds redundancy and reducesinterference. However there is a tradeoff between soft/softer handover &system capacity.

A UE involved in Soft/Softer Handover uses several radio links, moreDL channelization codes, and more DL power than a single-linkconnection.

Consequently, if all the UEs connected to a particular RNC are considered,more resources are needed in the RBSs, more resources over the Iub andIur interfaces, and more resources in the RNC. For this reason, the

number of radio links involved in the Soft/Softer handover must belimited.

Why is there soft handover gain?Soft handover gain comes from the following:

Macro diversity gain over slow fading.

Micro diversity gain over fast fading.

Downlink load sharing over multiple RF links. By maintaining multiple

links each link could transmit at a lower power, resulting in lower interferencetherefore a gain.

Define Processing Gain for WCDMA?

Processing Gain is ratio between rate of spreaded signal and rate of non spreaded signal.

Processing Gain = 10 log (Chip rate /Bit rate)

What is Significance of Eb_No?

Eb_No is related to QOS of a service which in terms related to bit errorrate.Technically it is the minimum signal to noise needed by infrastructureequipment after despreading it signal. This is a value used to comparedifferent infrastructure vendors. Eb_No changes with the service type.

For AMR 12.2 is ~ 4db for Node BFor AMR 12.2 is ~ 8db for MS

What is SIR? What is SIR?

SIR is the Signal-to-Interference Ratio the ratio of the energy in

dedicated physical control channel bits to the power density ofinterference and noise after dispreading.


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Explain Timer T3212? Periodic LA and RA updating is used to notify the network of the

UEs availability, and to avoid unnecessary paging attempts for a UE thathas lost coverage and is not able to inform the CN that it is inactive.

The periodic LA update procedure is controlled by a timer, called t3212,

which gives the time interval between two consecutive periodic locationupdates. The value is sent by the WCDMA RAN to UEs on the BCCH.

Explain the functionality of TPC

During Power Control, TransmitPower control(TPC) commands are

used to power up or power down based on SIR target in the step of 0.5

dB ( 1 dB if the connection is made over Iur).

What are the functionality of eNodeB? E-UTRAN consists solely of the evolved Node B (eNB), which is responsible for all radio

interface functionality.

eNB is the RAN node in the EPS architecture that is responsible for radio transmission to andreception from UEs in one or more cells.The eNB is connected to EPC nodes by means of an S1 interface.The eNB is also connected

to its neighbor eNBs by means of theX2 interface. Some significant changes have been made to the eNB functional allocation

compared to UTRAN. Most Rel-6 RNCfunctionality has been moved to the E-UTRAN eNB. Below follows a description of the

functionality provided by eNB.

Good PDF Document onLTE Functionality

1. Cell control and MME pool support

eNB owns and controls the radio resources of its own cells.Cell resources are requested byand granted to MMEs in an ordered fashion. This arrangement supports the MME poolingconcept. S-GW pooling is managed by the MMEs and is not really seen in the eNB.

2. Mobility control

The eNB is responsible for controlling the mobility for terminals in active state. This is doneby ordering the UE to perform measurement and then performing handover when necessary.

Find more onWCDMA Radio Resource Management

3. Control and User Plane security The ciphering of user plane data over the radio interface is terminated in the eNB. Also the

ciphering and integrity protection of RRC signaling is terminated in the eNB.

4. Shared Channel handling Since the eNB owns the cell resources, the eNB also handles the shared and random access

channels used for signaling and initial access.

5. Segmentation/Concatenation

Radio Link Control (RLC) Service Data Units (SDUs) received from the Packet DataConvergence Protocol (PDCP) layer consist of whole IP packets and may be larger than thetransport block size provided by the physical layer. Thus, the RLC layer must supportsegmentation and concatenation to adapt the payload to the transport block size.

6. HARQA Medium Access Control (MAC) Hybrid Automatic Repeat reQuest (HARQ)

layer with fast feedback provides a means for quickly correcting most errors from the radio
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channel. To achieve low delay and efficient use of radio resources, theHARQ operateswitha native error rate which is sufficient only for services with moderate error rate requirements

such as for instance VoIP. Lower error rates are achieved by letting an outer Automatic

Repeat reQuest (ARQ) layer in the eNB handle the HARQ errors.

7. Scheduling A scheduling with support for QoS provides for efficient scheduling of UP and CP data.

8. Multiplexing and Mapping The eNB performs mapping of logical channels onto transport channels.

9. Physical layer functionality The eNB handles the physical layer such as scrambling, Tx diversity, beamforming

processing and OFDM modulation. The eNB also handles layer one functions like linkadaptation and power control.

10. Measurements and reporting

eNB provides functions for configuring and making measurements on the radio environmentand eNB-internal variables and conditions. The collected data is used internally for RRM butcan be reported for the purpose of multi-cell RRM.

Good PDF Document onLTE Functionality You might also like:

hat will be the impact when you change reportingrange1a from

3 to 4 dB and timetotrigger1a 100 to 320 ms, without changing

any other parameters? Reduction in number of Event1a

Delayed Event1a trigger

Reduction in Average Active Set Size

Delay in Event1a could increase DL interference, which could lead to a drop call or increasein Average Power Per User (reduction in cell capacity)

What are the typical KPIs you use to measure a network and

what criteria? Access failure rate ( 2%).

Call setup time (CS: over 95% of the time < 6-second for mobile-to

PSTN, 9-second for mobile-mobile. PS: over 95% of the time

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Umts Possible Cause