IRAT Optimization / tuning

Initial tuning

- start with site shake downo verify basic datafill – scrambling code, neighbors, parameters o Call utran support to check if the site has any major / critical alarms before stating drive

test. o conduct calls on each sector / cell to test if all sectors are ok and do not have any

hardware issueso Drive around the site to determine if the feeders are not swappedo Drive away from site to determine if the site plumbing ./ antennas are oko Once site is cleared, start with cluster tuning

Cluster tuning – scanner, short voice call, long voice call, hs calls if needed , R99 calls if needed, idle mode UE, if needed.

KPI from drive test –

Metrics from Pilot scanner• Measured Ec/Io : Purpose: Verify that the Ec/Io corresponds to loading.• Measured RSCP: Purpose: Verify that the intended area is covered.

The UE and the Pilot scanner might report different values; the more stringent reading should be used to optimize the RF configuration.

• Best Server PSC : Purpose: Identify the best server in the test area; check for overshoot/fragmentation and clean cell boundaries.

• Number of servers within a threshold : to determine pilot pollution• Identify missing neighbors umts to umts• Identify missing irat neighbors if scan is conducted for gsm.• Pilot pollution – identify most polluting cell and suggest down tilt

Metrics from idle mode • Percentage of Ec/Io (below Qualmin) – determine no UMTS coverage• RSCP. EcIo• Change of best cell and re selection parameters ( in case we need to tune these)

Metrics from connected modeRscp, ecio, drop call rate, call set-up time, % time in umts, UE tx power, pilot pollution

- Identify missing neighbors – in TEMS shows detected set- UE set to umts only mode to determine poor quality / coverage on umts- Test IRAT handover with UE in dual mode

For ps and hs calls – R99 thruput, hs thru’put, cqi plot for hsdpa

Neighbor list tuning – add neighbors / delete / re order neighbors

TIPS on HSDPA optimization

• Network performing well for R’99 may have sub-optimal HSDPA performance

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– Impact of frequent changes of best server would NOT be visible in connected mode for R’99 but would lead to sub-optimal HSDPA performance

– No soft handover in downlink on HSDPA for data channel

• RF optimization is the key to improving HSDPA performance– Poor RF conditions results in lower CQI reported by UE and smaller Mac-HS TB sizes to

be scheduled – Numerous cell-changes impact throughput due to

• During drive tests, run one of the UR in idle mode and collect idle mode log. Generate serving cell plot and identify fragmented cells. Tilt / azimuth changes to create Pilot dominance

How will you evaluate call setup failures using Drive test post processing tool

- identify if the UE initiated call in correct cell – cell re selection parameters and from idle mode drive test

- Check if ue was in good / poor radio environment . If UE was in poor radio environment, check scanner logs to identify split cells, overshooting cells and alarms on the site

- If ue was in good radio environment, check ue tx power – check if sector has ul interference – rssi value from sib 7

- Layer 3 message to identify the stage of failure in the rrc process. - Add layer 3 details

Difference between Open power control / Closed loop power control

Open loop is during call set-up – explained in next point

Closed loop is during a call – connected mode - has 2 sections inner and outer loop Inner loop is during a call ue and node b exchange power control bits at 1500hz. The system sets up a target SIR and tx power is adjusted ( increased / decreased) to meet / maintain the SIR target.

Outer loop -At the RNC, the signal is combined from multiple node b and checks if the set SIR target is sufficient to meet the BLER target. If no, the SIR target is shifted.

How does initial UE Tx power is determined?

Determined from rach control parameters – ue sends an initial burst – preamble and waits to receive an AI access indication on the AICH channel…if there is no answer, ramps up the power until receives an ack. Power steps and the time between the bursts is sent in the SIB -5 and 6.

Preamble Initial Power – initial PRACH transmit power

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Power Ramp Step – power increment between successive preamblesTime between preamblesMax number of premaTime between preamble and AI (access indication sent on downlink)Time between preamble and messagepowerOffsetP0 - power increment between successive preambles

preambleRetransMax – max number of pre ambles constantValueCprach – constant value powerOffsetPpmmaxTxPowerUl

As a concept - Preamble_Initial_Power = Primary CPICH TX power – CPICH_RSCP + UL interference + Constant Valuewhere CPICH_RSCP is calculated, and the other three parameters are sent on SIB 5 and 6

The Power Ramp Step is from an RRC signaling message. It is in dBs, and tells the UE how much it should increase its power from the previous preamble..

Different IRAT parameters – Event 2D , 2C and 3a

2D Start compressed mode The estimated quality of the currently-used frequency is below a certain threshold – Active Set based measurement

2F Stop compressed mode The estimated quality of the currently-used frequency is above a certain threshold – Active Set based measurement

6A Start compressed mode The UE Tx power becomes larger than an absolute threshold

6B Stop compressed mode The UE Tx power becomes less than an absolute threshold

usedFreqThresh2dEcnousedFreqThresh2dRscpusedFreqThresh2fEcnousedFreqThresh2fRscpgsmThresh3a – GSM is better than specified threshold.timeToTrigger2d, 2f and 3aIRAT Tuning

Determine why the Ue is moving from W2G. - Poor quality on WCDMA – fix pilot pollution, overshooting pilots, missing umts neighbors, alarms

on adjacent sites - Poor coverage on WCDMA - missing sites, delayed integration of new sites, edge of the network. - check for time spent on UMTS to decide if IRAT settings are too steep / lenient- Verify IRAT KPI from table GSM Relation to view umts to gsm neighbor irat statistics to isolate

neighbor relationships with high failure rate.

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- For optimization of IRAT HOo Verify data fill – definition of external GSM cells in umts- bcch, bsic, lac,o Verify any W2G missing neighbors from analysis of GSM and umts scanner datao Verify definition of remote LAC in MSC datafillo Verify definition of data fill in GSM and UMTS SGSNo Verify coverage of GSM in the area of IRAT failureso Verify if GSM cell has congestion / blocking, that could lead to failed IRATs

- check if an event 2d was triggered just before a drop call – indication that event 2d threshold should be increased ( ecio from -12 to say -9 or rscp from say -105 to say -102 or higher.) Check the cause of IRAT – ecio – bad quality or rscp –poor coverage in order to adjust these thresholds.

- Layer 3 message: measurement report contains the event 2d. - Layer 3 message: measurement control - has information on gsm neighbors ( bcch, bsic) to

measure and the event 3a thresholds- Layer 3 message: measurement report after the above will have the 3a event.

Various UMTS KPIs - Drive test KPIs and Stats KPIs

HS and PS KPI

AttemptsSuccessfully connectedDroppedSuccessfully completedMean DL rate allDL rate > 400kDownload Completed within 200 sec (%)Max DL timer (s)

KPI from statistics CS Speech (AMR12.2 Quality at 95% percentile (UL & DL

Throughput Channels DL R99

Throughput Channels UL R99

Throughput Channels HS

Throughput Channels Eul

CS Speech Dropped Call Rate

PS Dropped Call Rate

HS Dropped Call Rate

Eul Dropped Call Rate

CS Speech Call Success Rate

PS Call Success Rate

HS Call Success Rate

Eul Call Success Rate

Successful Active Set Update Rate

CS Hard Inter-RAT UMTS->GSM HO Success Rate

Hard Inter-Frequency HO Success Rate

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HS Mobility for Target Cell

Eul Mobility for Target Cell

Congestion - User Perceived Blocking

CS Speech Traffic

Active Set Size Distribution Per Cell

Cell Availability

HS Availability

Eul Availability

Circuit-Switched (CS) Users

PS Data DCH Interactive Users

HS Data DCH Interactive Users

Eul Data DCH Interactive Users

RSSI

Transmit Power

T1 Error

Uplink CE usage

Downlink CE Usage

How do you find Uplink interference using drive testing - High UE Tx power very the location of the node b- Check SIB 7 – there is a value for ul rssi – for a new network with almost no traffic, this value

should be -102 to -104. Value of say -98 or higher indicate ul interference- If we have network statistics, check average rssi for the cell

How to evaluate if UE is R99 / HSDPA ??

In initial call set-up UE sends MS class mark in CM service request – telling the network its capability

Definition of AMR – Variable / Fixed AMR ?

What is the voice rate for AMR? -

12.2 Ericsson also allows amr7.950, amr5.900 but these are not used.

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Using post processing drive test tools

- Creation of super stream for data analysis of a small cluster - Run missing neighbor analysis. Set-up thresholds for reporting range, % thresholds

for addition and removal, use of existing neighbor lists, min # of reports to consider missing neighbor, max distance of nbr cell.

- Using network Image – Loading log files into say Actix and using facility of Network image. The network image is a filtered version of all the data collected from drive test logs. The “image” stores user defined parameters for a drive test log, instead of all the parameters collected in the drive test. Helps to create a single log file from a collection of multiple drive test logs for say a cluster. Also the data can be binned to say 50m binns allowing further reduction of log files.

- Analysis and benchmarking is performed to generate the following - o UMTS Drive Test Summaryo UMTS CPICH Level Analysiso UMTS Call Statistics - # calls, call set-up success rate, call success rate, # drops,

drop call rate, drop call reasons, Mobile originated and mobile terminated call statistics

o UMTS Call Setup Analysis - failed called attempts, # call attempts, call setup time, call set-up failure causes

o UMTS Handoff Analysis –# of 1a, 1b nd 1c events. For HS # of e1d – change of best cell

o UMTS Quality Analysis – DL bler Aggregate, bler per call or bler during sho, CQI plots for HS calls.

o HS and PS Call Analysis - Mean DL rate all, DL rate > 400k, download completed within 200 sec (%), Max DL time, %tile time of download < 120, Mean rate of download t > 120sec for say a 5MB download.

Pl review additional document on call flow

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Example Voice Call Flow (MOC)UE RNC

RRC: RRC Connection Request (CCCH)

RRC: RRC Connection Setup (CCCH)

RRC: RRC Connection Setup Complete (DCCH)

RRC: Initial Direct Transfer - CM Service Request (DCCH)

RRC: Downlink Direct Transfer – Auth & Ciph Request (DCCH)

RRC: Uplink Direct Transfer - Auth & Ciph Response (DCCH)

RRC: Security Mode Command (DCCH)

RRC: Security Mode Complete (DCCH)

RRC: Uplink Direct Transfer - SETUP (DCCH)

RRC: Downlink Direct Transfer – CALL PROCEEDING (DCCH)

RRC: Radio Bearer Setup (DCCH)

RRC: Downlink Direct Transfer – ALERTING (DCCH)

RRC: Radio Bearer Setup Complete (DCCH)

RRC: Downlink Direct Transfer - CONNECT (DCCH)

RRC: Downlink Direct Transfer – CONNECT ACK (DCCH)

RRC: Measurement Control (DCCH)RRC: Measurement Report (DCCH)

Call Setup Phase

KPIs: Call Setup Success RateCall Setup Time

RRC: Uplink Direct Transfer - DISCONNECT (DCCH)

RRC: Direct Transfer - Release (DCCH)

RRC: Uplink Direct Transfer – Release Complete (DCCH)

Total Call Time

KPIs: Dropped Call

RRC Connection is released after the Call Release.

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Example PS R99 Call FlowUE RNC

RRC: RRC Connection Request (CCCH)

RRC: RRC Connection Setup (CCCH)

RRC: RRC Connection Setup Complete (DCCH)

RRC: Initial Direct Transfer - CM Service Request (DCCH)

RRC: Downlink Direct Transfer – Auth & Ciph Request (DCCH)

RRC: Uplink Direct Transfer - Auth & Ciph Response (DCCH)

RRC: Security Mode Command (DCCH)

RRC: Security Mode Complete (DCCH)

RRC: Uplink Direct Transfer – SM ACTIVATE PDP CONTEXT REQUEST (DCCH)

RRC: Radio Bearer Setup (DCCH)

RRC: Downlink Direct Transfer – SM ACTIVATE PDP CONTEXT ACCEPT (DCCH)

RRC: Radio Bearer Setup Complete (DCCH)

RRC: Measurement Control (DCCH)

RRC: Measurement Report (DCCH)

RRC: Uplink Direct Transfer – SM Deactivate PDP Context Request (DCCH)

RRC: Direct Transfer – SM Deactivate PDP Context Accept (DCCH)

RRC: RRC Connection Release (DCCH)

Call Setup Phase

KPIs: Call Setup Success RateCall Setup Time

Total Call Time

KPIs: Dropped Call

RRC: Transport Channel Reconfiguration (DCCH)RRC: Transport Channel Reconfiguration Complete (DCCH)

Channel Switching

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Example HSDPA Call FlowUE

RNCRRC: RRC Connection Request (CCCH)

RRC: RRC Connection Setup (CCCH)

RRC: RRC Connection Setup Complete (DCCH)

RRC: Uplink Direct Transfer – SM ACTIVATE PDP CONTEXT REQUEST (DCCH)

RRC: Downlink Direct Transfer – SM ACTIVATE PDP CONTEXT ACCEPT (DCCH)

RRC: Measurement Report (e1a) (DCCH)

RRC: Active Set Update (DCCH)

RRC: Active Set Update Complete (DCCH)

RRC: Physical Channel Reconfiguration (DCCH)

RRC: Physical Channel Reconfiguration Complete (DCCH)

E1A:Radio Link AdditionNot a HS Cell Change. Here the procedure is to realign the parameters.RRC: Measurement Report (e1d) (DCCH)

RRC: Active Set Update (DCCH)

RRC: Active Set Update Complete (DCCH)

RRC: Physical Channel Reconfiguration (DCCH)

RRC: Physical Channel Reconfiguration Complete (DCCH)

E1D:Change of Best ServerHS Cell ChangeKPI

HS Cell Change Success RateHS Cell Change time

KPICall Setup Success RateCall Setup Time

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