IRAT Optimization / tuning Initial tuning -
start with site shake down o verify basic datafill datafill – scrambling code, code, neighbors, parameters Call utran support to check if the site has any major / critical alarms before stating drive o test. conduct calls on each sector / cell to test if all sectors are ok and do not have any o hardware issues Drive around the site to determine if the feeders are not swapped o o Drive away from site to determine if the site plumbing ./ antennas are ok o 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 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 po llution • Identify missing neighbors umts to umts • Identify missing irat neighbors if scan is conducted for gsm.
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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, o vershooting 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
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Difference between Open power control / Closed loop power control
Power Ramp Step – power increment between successive preambles Time between preambles Max number of prema Time between preamble and AI (access indication sent on downlink) Time between preamble and message powerOffsetP0 - power increment between successive preambles preambleRetransMax – max number of p re ambles constantValueCprach – constant value powerOffsetPpm maxTxPowerUl
As a concept Preamble_Initial_Power = Primary CPICH TX power – CPICH_RSCP + UL interference + Constant Value
where 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
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For optimization of IRAT HO o Verify data fill – definition of external GSM cells in umts- bcch, b sic, lac, o Verify any W2G missing neighbors from analysis of GSM and umts scanner data Verify definition of remote LAC in MSC datafill o o Verify definition of data fill in GSM and UMTS SGSN Verify coverage of GSM in the area of IRAT failures o Verify if GSM cell has congestion / blocking, that could lead to failed IRATs o
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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 sa y -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.
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Various UMTS KPIs - Drive test KPIs and Stats KPIs HS and PS KPI Attempts Successfully connected Dropped Successfully completed Mean DL rate all DL rate > 400k
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 -
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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 ??
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 -
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UMTS Drive Test Summary UMTS CPICH Level Analysis 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 UMTS Call Setup Analysis - failed called attempts, # call attempts, call setup time, call set-up failure causes UMTS Handoff Analysis –# of 1a, 1b nd 1c events. For HS # of e1d – change of best cell UMTS Quality Analysis – DL bler Aggregate, bler per call or bler during sho, CQI plots for HS calls. 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.
Example Voice Call Flow (MOC) UE
RRC: RRC Connection Request (CCCH)
RNC
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)
Call Setup Phase
RRC: Uplink Direct Transfer - Auth & Ciph Response (DCCH) RRC: Security Mode Command (DCCH) RRC: Security Mode Complete (DCCH) RRC: Uplink Direct Transfer - SETUP (DCCH)
KPIs: Call Setup Success Rate Call Setup Time
RRC: Downlink Direct Transfer – CALL PROCEEDING (DCCH) Total Call Time KPIs: Dropped Call
RRC: Radio Bearer Setup (DCCH) RRC: Radio Bearer Setup Complete (DCCH) RRC: Downlink Direct Transfer – ALERTING (DCCH) RRC: Downlink Direct Transfer - CONNECT (DCCH) RRC: Downlink Direct Transfer – CONNECT ACK (DCCH) RRC: Measurement Control (DCCH) RRC: Measurement Report (DCCH) RRC: Uplink Direct Transfer - DISCONNECT (DCCH) RRC: Direct Transfer - Release (DCCH) RRC: Uplink Direct Transfer – Release Complete (DCCH)
RRC Connection is released after the Call Release.
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Example PS R99 Call Flow UE
RRC: RRC Connection Request (CCCH)
RNC
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)
Call Setup Phase
RRC: Uplink Direct Transfer - Auth & Ciph Response (DCCH) RRC: Security Mode Command (DCCH) RRC: Security Mode Complete (DCCH)
Total Call Time KPIs: Dropped Call
RRC: Uplink Direct Transfer – SM ACTIVATE PDP CONTEXT REQUEST (DCCH) RRC: Radio Bearer Setup (DCCH) RRC: Radio Bearer Setup Complete (DCCH)
KPIs: Call Setup Success Rate Call Setup Time
RRC: Downlink Direct Transfer –SM ACTIVATE PDP CONTEXT ACCEPT (DCCH) RRC: Transport Channel Reconfiguration (DCCH) RRC: Transport Channel Reconfiguration Complete (DCCH)
Channel Switching
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)
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Example HSDPA Call Flow UE
RRC: RRC Connection Request (CCCH)
RN C
RRC: RRC Connection Setup (CCCH) KPI Call Setup Success Rate Call Setup Time
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) RRC: Measurement Report (e1d) (DCCH) RRC: Active Set Update (DCCH) RRC: Active Set Update Complete (DCCH)
KPI HS Cell Change Success Rate HS Cell Change time
RRC: Physical Channel Reconfiguration (DCCH)
E1A: Radio Link Addition Not a HS Cell Change. Here the procedure is to realign the parameters. E1D: Change of Best Server HS Cell Change
RRC: Physical Channel Reconfiguration Complete (DCCH)
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