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1 © 2005 Nokia V1-Filename.ppt / yyyy-mm-dd / Initials
3G RANOP
Module 7– Parameter Optimisation
2 © 2005 Nokia V1-Filename.ppt / yyyy-mm-dd / Initials
3G RAN Optimisation
RF Optimisation
and Neighbour Planning
• RF optimisation• New Site Integration• Neighbour plan
optimisation
Signalling Flows
• RRC Establishment• RAB Establishment• SHO• ISHO
Drive Test Analysis
• Drive Survey Analysis• System Performance
(RRC and RAB phases)
ClusterPreparati
on
• Cluster health checks• Parameter consistency
check• Neighbour list
verification• Uplink interference as
a problem indicator
Inter-System Working and Optimisation
• 3G<>2G Cell reselection
• Neighbour Planning• Handover Process and
compressed mode• 3G ISHO service
analysis (AMR and PS)• GSM ISHO Optimisation
Parametric
Optimisation
• Use of Parameters to optimise network performance
Network Statistics
• Cell Resources• RRC/RAB Performance• Handovers• Abnormal Release
3 © 2005 Nokia V1-Filename.ppt / yyyy-mm-dd / Initials
Module 7 – Parameter Optimisation
Objectives
After this module the delegate shall be able to:-
• List some of the parameters that can be tuned for
improved performance
• Match these parameters to Call Setup and Call
Retention improvement areas
4 © 2005 Nokia V1-Filename.ppt / yyyy-mm-dd / Initials
Parameter Optimisation Introduction
• The foundation of good network performance comes from a well optimised:• RF Plan• neighbour plan• Scrambling plan
• The maximum benefits from parameter optimisation can only be realised if the above are in place.
• Although parameter optimisation can provide short term gains they do not correct underlying network problems. (E.g SHO <> Dominance)
• The UE types in the network needs to be taken into account during parameter optimisation
• There are always tradeoffs (e.g setup time versus success rate)
• Parameter values may be different from network to network due to NW plan and operator strategy and therefore these parameters should be tuned in every networkBasic Radio Platform (Site/Antenna Location,etc)
Scrambling Code Planning
Neighbour Definition
Parameterisation
Feature Strategy
5 © 2005 Nokia V1-Filename.ppt / yyyy-mm-dd / Initials
Nokia Parameters an Introduction
• RNC = Radio Network Controller• WBTS = WCDMA Base Station• WCEL = WCDMA Cell• ADJ = Adjacency for WCDMA cell
• ADJS = intra-frequency adjacency
• ADJI = inter-frequency adjacency
• ADJG = inter-system adjacency
• HOP = Handover Path• HOPS, HOPI, HOPG
• FMC = Frequency Measurement Control
• FMCS, FMCI, FMCG• COCO = Radio Network
Connection ConfigurationSee RNC Parameter Dictionary
DN00211177
RNC
WBTS
WCELL
ADJS
HOPS
ADJG
HOPG
FMCG
ADJI
HOPI
FMCI
FMCS
COCO
Managed Objects
6 © 2005 Nokia V1-Filename.ppt / yyyy-mm-dd / Initials
Common Channel Power settings
• Common Channel power settings are critically important as they define the cell edge.
• The latest recommended settings are based on Nokia’s global experience and have been seen to work well. Care should be taken when optimising these parameters.
• The link budget of the PCCPCH and SCCPCH can be compared with Data on the DPCH.
• There tends to be plenty of margin in AICH and PICH.
• In general neighbouring cells should not have CPICH power differences greater than 3dB otherwise this can lead to soft handover radio link failures.
• Exceptions may occur if one cell is an indoor solution and the other is a macrocell
7 © 2005 Nokia V1-Filename.ppt / yyyy-mm-dd / Initials
DL Common Control Channel
• DL Common control channels must be heard over the whole cell.
• The only common physical channel that can have power control is SCCPCH, when it carries the FACH transport channel.
• All other downlink common physical channels don't use power control: PCCPCH, CPICH, P-SCH, S-SCH, PICH, AICH and SCCPCH
• The power of the common physical channels are set relative to the CPICH:
Parameters Default (Relative) Default (Absolute)
PtxPrimaryCPICH 33 dBm 33 dBmPtxPrimarySCH -3 dB 30 dBmPtxSecSCH -3 dB 30 dBmPtxPrimaryCCPCH -5 dB 28 dBmPtxSecCCPCH 0 dB 33 dBmPtxPICH -8 dB 25 dBmPtxAICH -8 dB 25 dBm
8 © 2005 Nokia V1-Filename.ppt / yyyy-mm-dd / Initials
DL Common Control Channel
Different quality requirement for the common channels make power planning a non-trivial task
Pilot coverageP-CCPCHcoverage
In this example the mobile "sees" the cell but cannot access it as it cannot decode the BCH
Possible values in dBm
CPICH = 33dBmP-CCPCH= 28 dBmS-CCPCH= 33 dBmSCH1= SCH2 = P-CCPCH = 28dBm
Possible values in dBm
CPICH = 33dBmP-CCPCH= 28 dBmS-CCPCH= 33 dBmSCH1= SCH2 = P-CCPCH = 28dBm
9 © 2005 Nokia V1-Filename.ppt / yyyy-mm-dd / Initials
DL Common Control Channel
• Not all the CCCH need to be treated in the same way:• Only Power Setting (depending on coverage)
• CPICH• P-CCPCH• P/S-SCH• AICH
• Power Setting and channel availability for multiple access/depending on coverage and traffic)
• PICH depending on paging repetition used per radio frame (10ms)
• S-CCPCH depending on traffic load on FACH
• Setting the DL Common Control Channel Power is a trade off between:• cell coverage: all the channels must be decoded at the cell edge• cell capacity: the common channel power steal resources from the traffic
channels
10 © 2005 Nokia V1-Filename.ppt / yyyy-mm-dd / Initials
Effects CPICH Power modification
CPICH Transmit Power
Increased soft handover overhead
Too much power
Too little power
Less Power Available for traffic
CPICH coverage holes
Unreliable scrambling code detection
Unreliable channel estimation
Early cell reselection /handover
Increased Eb/No requirement
Reduced system capacity
Reduced system capacity
Reduced system coverage
Slow initial synchonisation
Non-ideal traffic distribution
Late cell reselection /handover
Non-ideal traffic distribution
CPICH Transmit Power
Increased soft handover overhead
Too much power
Too little power
Less Power Available for traffic
CPICH coverage holes
Unreliable scrambling code detection
Unreliable channel estimation
Early cell reselection /handout too early
Increased Eb/No requirement
Reduced system capacity
Reduced system capacity
Reduced system coverage
Slow initial synchronisation
Non-ideal traffic distribution
Late cell reselection /handout too late
Non-ideal traffic distribution
11 © 2005 Nokia V1-Filename.ppt / yyyy-mm-dd / Initials
Common Channel Power Configuration
• Soft handover is driven by the CPICH Ec/Io which means that CPICH power allocations are important
• If neighbouring cells have different CPICH allocations then radio links will be unbalanced during soft handover and radio links may fail
• Requirement to align CPICH allocations as much as possible
• Neighbouring Node B with equal CPICH result in balanced radio links during soft handover
• Inner loop power control will be driven by both Node Bs
20 W 20 W
20 W 20 W
33 dBm CPICH
• Scenario results in unbalanced radio links during soft hand over. Inner loop power control will be driven by Node B with 28dBm CPICH and therefore the radio link to the second Node B may fail
33 dBm CPICH
33 dBm CPICH
28 dBm CPICH
30 dBm CPICH
28 dBm CPICH
• Slightly unbalanced radio links during soft handover
• Inner loop power control will be driven primarily by the 28dBm CPICH Node B
20 W 20 W
12 © 2005 Nokia V1-Filename.ppt / yyyy-mm-dd / Initials
Call Setup – Key Areas for investigation
• Cell Selection and Reselection• Initial cell selection to a good cell and subsequent cell reselections to
better cells is essential to increase the Call Setup Success Rate (CSSR) and speed up the call setup time.
• RACH Process• Improve the RRC Setup Performance
• Activation Time Offset• Improve PS Call Setup success rate by allowing more time for Radio
Bearer setup and Reconfiguration procedures
• SRB changes• Decrease call setup time by increasing the speed of the signalling bearer
13 © 2005 Nokia V1-Filename.ppt / yyyy-mm-dd / Initials
Cell Reselection Parameter Examples• Cell reselection triggering time (WCEL-Treselection = 2s)
• Reselection takes place immediately when the UE notices that there is difference between the cells’ Ec/No values (in worst case scenario there can be up to 3dB + Qhyst difference based on the measurement accuracy requirement)
• Cell reselection hysteresis 2 (WCEL-Qhyst2 = 4dB)• This will add 4dB hysteresis to the neighboring cell evaluation (target for the
cell reselection)
• Cell Re-selection Quality Offset 2 (HOPS-AdjsQoffset2 = 0dB)• This parameter is used in the cell re-selection and ranking between WCDMA
cells. The value of this parameter is subtracted from the measured CPICH Ec/No of the neighbor cell before the UE compares the quality measure with the cell re-selection/ ranking criteria
• Sintrasearch (WCEL-Sintrasearch = 12dB)• This parameter is used by the UE to calculate the threshold (CPICH Ec/No) to
start intra frequency (SHO) measurements (Sintrasearch above QqualMin value)
• Minimum required quality level in the cell (WCEL- QqualMin = -18dB)• Minimum required RX level in the cell (WCEL- QrxlevMin = -111dBm)
14 © 2005 Nokia V1-Filename.ppt / yyyy-mm-dd / Initials
Qqualmeas (dB)(CPICH Ec/N0)
Qrxlevmeas (dBm)CPICH RSCP
Qqualmin(–24...0)
Qrxlevmin(–115...–25)
Srxlev > 0
Pcompensation(typ =>0db)
Squal > 0S-Criterion
fulfilledSqual >0 AND
Srxlev > 0
Cell Selection - S Criterion
• The Qqualmin and Qrxlevmin parameters should be tuned carefully as non optimum settings can have significant impact on CSSR, Call setup time and time on 3G
• If the cell does not fulfill the suitable cell criteria (i.e. S-criteria) the UE cannot access the cell and therefore the UE is out of the coverage
15 © 2005 Nokia V1-Filename.ppt / yyyy-mm-dd / Initials
BLER for Each Ec/No
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
> -4 -4 to -
6
-6 to -
8
-8 to -
10
-10 to
-12
-12 to
-14
-14 to
-16
-16 to
-18
-18 to
-21
<-21
Ec/No [dB]
[%]
BLER for Each RSCP
0%
10%
20%
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100%
> -60 -60 to -
70
-70 to -
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-80 to -
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-90 to -
100
-100 to -
112
-112 to -
115
< -115
RSCP (dBm)
[%]
These calls may be unable to setup the call after Qqualmin is changed to –18dB from current –20dB
Call Setup status statistics for each Ec/No rangeCall Setup status statistics for each RSCP range
Cell Selection example
• There is a tradeoff between maximising 3G utilisation and CSSR (end user experience)
• Even though the CSSR is ~ 70% successful in poor RF conditions (Ec/No<-18 dB)
• It is recommended to leave the Qqualmin and Qrxlevmin as –18dB and –111 dBm respectively
16 © 2005 Nokia V1-Filename.ppt / yyyy-mm-dd / Initials
Cell Reselection and Call Setup Time
• Poor cell reselection can lead to poor call setup time distribution (due to UE having to send several RRC Connection Requests
0.0%
20.0%
40.0%
60.0%
80.0%
100.0%
<3.
5s
3.5s
- 3
.7s
3.7s
- 3
.9s
3.9s
- 4
.1s
4.1s
-4.3
s
4.3s
-4.5
s
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-4.7
s
4.7s
-4.9
s
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-5.1
s
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-5.3
s
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-5.5
s
>5.
5s
Setup Time (seconds)
Call Setup Delay (PDF & CDF)
0
10
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0 0 to 3000 3000 to 5000 5000 to 8000 8000 to 10000 > 10000Setup Time [ms]
PDFCDF
Call Setup Delay CDF
Poor Cell Reselection Performance Corrected Reselection Performance
17 © 2005 Nokia V1-Filename.ppt / yyyy-mm-dd / Initials
• Default – ‘Normal’ conditions• Qqualmin = -20dB• Search when CPICH<-8dB, neighbours must be 2dB better, delay reselection by 3s
• Set1 – Aggressive Reselection• Start Searching Earlier (-6dB), no hysteresis to neighbour, change after 1s delay
• Set2 – Faster Change• Change ‘immediately’ but capped by hysteresis
• Set3 – Search earlier with faster Change • Searching starts at -6dB, hysteresis to neighbours but change ‘immediately’
Cell Reselection Test Case Example
Parameter Default Set1 Set2 Set3Sintrasearch 12dB 14dB 12dB 14dBQhyst2 2dB 0 2 2Treselection 3s 1 0 0
18 © 2005 Nokia V1-Filename.ppt / yyyy-mm-dd / Initials
Cell Reselection Test Case Results
•Note: With common channel setting in this network: base Ec/No (own cell) is around -4 dB (that’s why not more than 1 cell at Ec/No > -4 dB)
Start the measurements at Ec/No ~-8dB -> with Qqualmin = -20 dB -> Sintrasearch >= 12dB -> test at least 12dB and 14dB
•If the reselection happens at about –16dB there is only 30% possibility that the second best server is >2dB lower than best server
•This does not leave enough room for deviation between best and second best server
Scanner data chart:•If the measurements for cell reselection happens at about Ec/No –8dB, there is 95% possibility that second best server is >2dB lower than the best server
•This means that the cell reselection has 80% probability it does not to lead to ping pong
19 © 2005 Nokia V1-Filename.ppt / yyyy-mm-dd / Initials
RACH Process
• Optimum RACH performance is needed to ensure;
• High RRC Setup performance and RRC Connection Access Success. • In both cases the testing is concentrated on RRC Setup success rate, and the
number of RRC Connection Requests sent.
• Minimise the impact of UE Tx power (preamble power) to the cell capacity.
• Minimise call setup delay
• Different UE performance is taken into account
20 © 2005 Nokia V1-Filename.ppt / yyyy-mm-dd / Initials
RRC Setup Phase
• This phase starts when UE sends the “RRC CONNECTION REQUEST” message using the PRACH channel
• It is completed when RNC, after reserving all the necessary resources for the RRC Connection (RNC, BTS, Radio and Transmission), replies with DL “RRC CONNECTION SETUP” message, carried over S-CCPCH (FACH sub-channel)
[RACH] RRC:RRC Connection Request
UEUE Node BNode B RNCRNC
ALCAP:ERQ
ALCAP:ECF
NBAP: RL Setup Request
Start TX/RXStart TX/RX
Start TX/RXStart TX/RX
[FACH] RRC: RRC Connection Setup
NBAP: RL Setup Response
[DCH] RRC: RRC Connection Setup Complete
NBAP: Synchronisation Indication
L1 Synchronisation
21 © 2005 Nokia V1-Filename.ppt / yyyy-mm-dd / Initials
RACH Process
DownlinkBS
L1 ACK / AICH
UplinkMS Preamble
1
Not detected
Message partPreamble2
PRACH_preamble_retrans# PRACH preambles transmitted during one PRACH cycle without receiving AICH response
UEtxPowerMaxPRACH
… … … …
RACH_tx_Max# preamble power ramping cycles that can be done before RACH transmission failure is reported
PowerRampStepPRACHpreamble
PowerOffsetLastPreamblePRACHmessage
Initial preample power:•Ptx = CPICHtransmissionPower-RSCP(CPICH) +RSSI(BS) + PRACHRequiredReceivedCI
22 © 2005 Nokia V1-Filename.ppt / yyyy-mm-dd / Initials
RACH Process parameters
• Main parameters to improve the RRC Connection Setup performance are listed below
• WCEL-PRACH_preamble_retrans & RACH_tx_Max (def 8 & 8)• WCEL-PowerOffsetLastPreamblePRACHmessage (def 2dB)• WCEL-PowerRampStepPRACHpreamble (def = 2dB)
• The RRC Connection Access success is highly dependent on the UE so all used UEs should be tested carefully before making any changes.
• Note, Some of the UEs (especially the ones with, early, Qualcomm chipset) could have fixed values for some parameters (an example from Sanyo):
• PRACH_preamble_retrans & RACH_tx_Max = 8 & 8
• PowerRampStepPRACHpreamble = 3dB
23 © 2005 Nokia V1-Filename.ppt / yyyy-mm-dd / Initials
RACH Process test• Two values for PRACHRequiredReceivedCI tested (drive testing)
• -20dB & -25dB : UL interference conditions are at the same level (reported in SIB 7 for both cases)
100%
0% 0% 0%
88%
2% 5% 6%
0%
20%
40%
60%
80%
100%
1 2 3 4
# RRC Connection Request Messages per call setup
%
PRACH req. C/I = -20dB PRACH req. C/I = -25dB
• Clear improvement in number of needed RRC Connection Request messages per call.
• For –20dB 100% of established calls are setup with only 1 RRC Connection Request message
• Clear improvement number of sent preambles per RRC Connection Request for –20dB case.
• For –20dB 50% of cases the needed number of preambles is <=4 where as for –25dB it is ~6.5
• There should also be improvement of the call setup time
0%
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100%
1 2 3 4 5 6 7 8
PRACH req. C/I = -25dB PRACH req. C/I = -20dB
24 © 2005 Nokia V1-Filename.ppt / yyyy-mm-dd / Initials
RACH Process test• Two values for
PRACHRequiredReceivedCI tested (drive testing)
• -20dB• -25dB
• UL interference conditions are at the same level (reported in SIB 7 for both cases)
• Clear improvement in call setup delay for –20dB case. ~65% of the established calls are through with only 3.5 – 3.7s delay and the >5.5s delay “tail” disappears (in this case).
96.2%
100.0%
94%
95%
96%
97%
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100%
-25dB -20dB
Call Setup Success Rate
0.0%
20.0%
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<3
.5s
3.5
s -
3.7
s
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s -
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s
3.9
s -
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s
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s-4
.3s
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s-4
.5s
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.7s
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.9s
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s-5
.1s
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.3s
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s-5
.5s
>5
.5s
Call Setup Delay (seconds) RRC Conn. Req. to Alerting
PRACH req. C/I = -25 PRACH req. C/I = -20
25 © 2005 Nokia V1-Filename.ppt / yyyy-mm-dd / Initials
RNC receives RRC Connection Setup Complete –message ->
RNC receives RRC Connection Setup Complete –message ->
RRC Connection Setup Complete –message SENT after 7 TSLs from DL sync is achieved
RRC Connection Setup Complete –message SENT after 7 TSLs from DL sync is achieved
L1 Synchronization established
BTS sends NBAP: SYNCHRONIZATION
IDICATION -message
L1 Synchronization established
BTS sends NBAP: SYNCHRONIZATION
IDICATION -message
UE initiates physical dedicated channel establishment before sending e.g. RRC Connection Setup Complete –message on DPDCH
UE initiates physical dedicated channel establishment before sending e.g. RRC Connection Setup Complete –message on DPDCH
Timer T312 startedTimer T312 started
“in sync” indicators on L1
“in sync” indicators on L1
Timer T312 stopped
Timer T312 stopped
N312 L1 “in sync” indicators
N312 L1 “in sync” indicators
L1 Synchronizati
on established
L1 Synchronizati
on established
N_INSYNC_IND indicators on
L1
N_INSYNC_IND indicators on
L1
1
• When a physical dedicated channel establishment is initiated by the UE, the UE starts a timer WCEL-T312 (def=10s) and waits for layer 1 to indicate WCEL-N312 (def=4) "in sync" indications
• On receiving N312 "in sync" indications, the physical channel is considered established and the timer T312 is stopped and reset
• On the BTS side after receiving synchronisation indicators the BTS sends NBAP: SYNCHRONIZATION INDICATION –message to RNC after which the closed loop and outer loop PC start to control the powers
RRC Setup & Access Phase
26 © 2005 Nokia V1-Filename.ppt / yyyy-mm-dd / Initials
RRC Setup & Access Phase
• In case UE is not able to establish synchronisation within timer T312 it stops TX on the DCH
• In case BTS is not able to establish synchronisation it does not send NBAP:Synchronization Indication –message to RNC
• The BTS tries to establish synchronization until RNC sends NBAP:Radio Link Deletion message
[RACH] RRC:RRC Connection Request
UEUE Node BNode B RNCRNC
ALCAP:ERQ
ALCAP:ECF
NBAP: RL Setup Request
Start TX/RXStart TX/RX
Start TX/RXStart TX/RX
[FACH] RRC: RRC Connection Setup
NBAP: RL Setup Response
L1 Synchronisation
27 © 2005 Nokia V1-Filename.ppt / yyyy-mm-dd / Initials
• Call Setup Success Rate (CSSR) depends on how well UE responds to the Radio Bearer (RB) Reconfiguration or RB Setup processes
• If UE does not have enough time to setup the lower layers for the new RB configuration then call setup will fail.
• This could be improved by increasing the Activation Time Offset (ATO) parameter:
• Connection Frame Number (CFN) is used in NBAP and RRC messages, when a radio link is reconfigured.
• It is used to indicate the activation time of the reconfiguration, and it is set by the Packet Scheduler
• The CFN, which is set to the "activation time" field in L3 messages, is:
(the CFN provided by FP + (ActivationTimeOffset + SignalingDelayOffset)/10) mod 256
• Call Setup time can be improved by changing ATO and/or changing the Signalling Radio Bearer (SRB) bit rate
• Both call setup delay and access performance should be considered and balanced.
Radio Bearer Process
28 © 2005 Nokia V1-Filename.ppt / yyyy-mm-dd / Initials
ATO• In RAN1.5. 2 ED2 the total offset consists of ActivationTimeOffset parameter
part and fixed SignallingDelayOffset part• ActivationTimeOffset part represents the processing delay of RNC and BTS. • The SignalingDelayOffset is an RNC internal parameter that implies a
required offset based on the SRB bit rate, the actual procedure and the length of a RRC message. The fixed values set in RNC are below (ms)
RB Procedures Transport channel procedures
Service SRB 3,4 SRB 13,6 Service SRB 3,6 SRB 16,6
AMR 280 70 AMR 240 60
CS 280 70 CS 240 60
PS 200 50 PS 160 40
Physical channel and measurement procedures
Service SRB 3,6 SRB 16,6
All services 80 20
• The recommended value for ”ActivationTimeOffset” is 700ms for RAN1.5.2 (For RAN04 it will be 300ms) has been used.
29 © 2005 Nokia V1-Filename.ppt / yyyy-mm-dd / Initials
ATO change case
AMR_701
0
200
400
600
800
1000
1200
1400
1600
1 2 3 4 5 6 7 8 9 10 11 12
Tim
e(m
s)
1500 500 200 1 RRCConnectionRequest <=> RRCConnectionSetup2 RRCConnectionSetup <=> RRCConnectionSetupComplete3 RRCConnectionSetupComplete <=> MM CM Service Request4 MM CM Service Request <=> MM Authentication Request5 MM Authentication Request <=> MM Authentication Response6 MM Authentication Response <=> SecurityModeCommand7 SecurityModeCommand <=> SecurityModeComplete8 SecurityModeComplete <=> CC SetUp9 CC SetUp <=> CC Call Proceeding
10 CC Call Proceeding <=> RadioBearerSetup11 RadioBearerSetup <=> RadioBearerSetupComplete12 RadioBearerSetupComplete <=> CC Alerting
1300ms
1000ms
The difference in call setup time to the previous page is almost the difference between the RadioBearerSetup and RadioBearerSetupcomplete messages (part 11).
30 © 2005 Nokia V1-Filename.ppt / yyyy-mm-dd / Initials
SRB change case
94
95
96
97
98
99
100
RRC Setup SuccessRate RRC Access SuccessRate RRC Setup & Access SuccessRate
SRB 13.6kbpsSRB 3.4kbps
• RRC Connection Access phase Success Rate should be evaluated when changing the SRB bit rate
• Example of RRC performance with SRB 3.5 kbits/s and 13.6 kbits/s
31 © 2005 Nokia V1-Filename.ppt / yyyy-mm-dd / Initials
• If call setups are attempted and are failing in bad Ec/No or RSCP conditions then one solution to improve the call setup success rate might be to tune CPICHtoRefRABOffset
• The max DL power is determined by Admission Control as
Maximum DL power
EbNoref is the (linear) value of the planned downlink Eb/No of the reference service which is defined with parameter Downlink BLER target of the reference service (DLreferenceTargetBLER).
EbNoDCH is the (linear) value of the planned downlink Eb/No of the service transferred on the DCH
RDCH is the maximum transport channel bit rate of downlink DCH.
Rref is the maximum DCH bit rate of the reference service (parameter DLreferenceBitRate).
Ptx,DPCH,max is the value of WCEL-PtxDLabsMax - WCEL-PtxDPCHMax.
Ptx,off defines the power of the primary CPICH in relation to the maximum code power of the ref. service (WCEL-CPICHtoRefRABoffset)
32 © 2005 Nokia V1-Filename.ppt / yyyy-mm-dd / Initials
• However, it should be noted that the minimum power used is increased if Offset is reduced as well (Minimum power=Max power – DL PC Range) which might lead to the situation where too high powers are allocated even in the good coverage conditions -> too much power is wasted in BTS.
• CPICHtoRefRABOffset of 0 dB (default 2 dB) could be tested with RNC-PCrangeDL of 20 dB (default 15 dB)
Maximum DL power
Service Type
3.4 kbps standalone
SRB
13.6 kbps standalone
SRB
12.2 kbpsspeech +3.4 kbps
SRB
64 kbpsdata +
3.4 kbps SRB
128 kbpsdata +
3.4 kbps SRB
384 kbpsdata +
3.4 kbps SRB
Maximum 27.8 dBm 31.8 dBm 32.2 dBm 35.2 dBm 38.0 dBm 40 dBm
Minimum 15 dBm 16.8 dBm 17.2 dBm 20.2 dBm 23.0 dBm 25 dBm
• Example Maximum and Minimum Power for different services• WCEL-CPICHtoRefRABOffset = 2dB and RNC-PCrangeDL = 15dB
33 © 2005 Nokia V1-Filename.ppt / yyyy-mm-dd / Initials
SHO Optimisation
• The main emphasis in SHO optimisation is related to SHO overhead, SHO success rate, call drop rate and average Active Set size.
• Neighbor planning is more important than SHO parameter optimisation, so it should be done properly
• Acceptable SHO overhead in this case is 50 % or less, one example below
0 50 100 150 2000
100
200
300
400
500
600
Soft handover overhead [%]
34 © 2005 Nokia V1-Filename.ppt / yyyy-mm-dd / Initials
SHO Failures
• The SHO failures are mainly related to:
• Initial Synchronization Failure of the new added RL
• Active Synchronization Failure of the existing RL(s)
• Different soft handover parameters can help with synchronization problems between radio links.
• When new radio link is added to the Active set the L1 synchronization between the UE and the new BTS must be achieved. The UL/DL synchronization procedures are needed to establish reliable new connection between BTS and UE.
• Some of the initial synchronization failures are due to the fact that there can be difference in the UL noise rise levels of the adjacent cells (check Noise rise from Module1)
• If a lot of initial synchronization failures for SHO links are seen then one possibility is to try to reduce those by delaying the additions.
35 © 2005 Nokia V1-Filename.ppt / yyyy-mm-dd / Initials
SHO Failure
• If there are many Active Synchronization Failures detected, one action could be to advance the SHO activity (e.g. using cell individual offsets) or in general use different FMCS (usually these conditions are improved when addition is done earlier e.g. add 4dB and drop 6dB).
If UE does not have enough level to receive ActiveSet Update message it is possible that call drop happen because of H/O failure.
Call drop be avoided by setting earlier timing (timing for sending out Measurement report )of H/O between targeted cells.
Use FMC parameter Use ADJSEcNooffset
Impact all of FMC targeted areas
Impact only between 2 targeted
cells
36 © 2005 Nokia V1-Filename.ppt / yyyy-mm-dd / Initials
• The most important FMCS parameters to be used for SHO optimisation are
SHO Parameters
Parameters Default value
CPICH Ec/No Filter Coefficient 600 msAddition Window 2.5 dBAddition Time 100msDrop Window 4 dBDrop Time 640ms
• Default values should work fine, but in some cases more conservative SHO settings (add 4 dB, drop 6 dB) could be used to avoid high ASU period (time between Active Set Update message)
37 © 2005 Nokia V1-Filename.ppt / yyyy-mm-dd / Initials
Packet Scheduler Parameters
• The focus for PS data tests is to minimize the PS call drop and keep the throughput high
• The performance depends on the usage of certain bit rate and different RRC states of the connection.
• Dynamic Link Optimisation (DyLo) feature could impact the achieved throughput
• Maximum allowed bitrate in certain cells (e.g. Rural, Highway) could be set to a lower value if there is risk of capacity shortage (Radio, Iub)
• Further performance/throughput could be optimized with different bearer activity/inactivity timers and traffic volume parameters.
• The optimum set of parameters depend on the used application (FTP, MSS, email) and amount of data.
38 © 2005 Nokia V1-Filename.ppt / yyyy-mm-dd / Initials
DyLO Improves NRT traffic coverage
Dylo restrictions• Radio link conditions under DRNC cannot trigger DyLO• The reconfiguration of Iub AAL2 transmission resources is not
performed due to DyLO• DyLO is not allowed during compressed mode measurement
UE384kbps
128kbps
BTS
Radio link is modified to use lower bit rate (with physical channel reconfiguration
message) when Tx power is getting close to maximum, in order to ensure sufficient
quality
39 © 2005 Nokia V1-Filename.ppt / yyyy-mm-dd / Initials
Triggering of DyLO
time
Ptx, RLdistance
Ptx, ave
Triggering of DyLO
Ptx, maxOffset
Ptx, ave is averaged radio link power, measured and reported to RNC by BTS
Ptx, max is determined by Admission Control
The value of the Offset is fixed at 2 dB
DyLO is triggered if
Ptx, ave > Ptx, max – Offset
Dylo can be started only if the current bitrate is higher than Maximum Allowed DL User Bitrate in HHO
40 © 2005 Nokia V1-Filename.ppt / yyyy-mm-dd / Initials
Dylo Bit Rate Upgrade
• After downgrade of DCH bit rate due to DyLO, upgrade of the bit rate can only be performed from the initial bit rate
• Cell level parameter Initial and minimum allowed bit rate in downlink is configurable by operator
• Bit rate upgrade from any other bit rate is not possible
• Bit rate upgrade is based on downlink traffic volume measurement reports (capacity requests)
• A change in radio link power conditions does not trigger upgrade
• Possible triggering of the DyLO is checked before the bit rate is upgraded, in order to avoid ping-pong effect
• New Ptx, max is calculated by AC according to the new bit rate
• Initial Tx power Ptx, init is calculated by AC according to the new bit rate
• DyLO is possible if Ptx, init < (Ptx, max – Offset)
• Upgrade is not possible, the next lower bit rate is tried (lower power)
Fixed, 2 dB
41 © 2005 Nokia V1-Filename.ppt / yyyy-mm-dd / Initials
DyLO Test example –parameter settings
Time spent on different bearers’ spreading factorsDefault Set1 Set2sf8 36:45.873 24:27.095 16:37.340sf16 00:00.000 12:30.764 24:27.813sf32 02:07.373 08:43.990 08:46.952FACH 14:37.097 09:26.672 10:19.881Idle 00:37.344 00:21.919 00:10.115
Default Set1 Set2PtxDLabsMax 43 43 38 or 36InitialAndMinimumAllowedBitrateDL 384kbps 64kbps 64kbps MaxBitRateDLPSNRT 384kbps 384kbps 384kbps
Set 2 gives smallest time in
idle mode & more time in 128
kbits/s: improved NRT coverage
BTS types of Supreme,Optima : 38dBm, Metrosite 36dBm
384 kbits/s as initial & Minimum Bitrate gives
poor results
42 © 2005 Nokia V1-Filename.ppt / yyyy-mm-dd / Initials
Dylo Test example- compare throughput with the coverage
CPICH RSCP and RB Status (Set2)
0
100
200
300
400
16:4
1:39
:209
16:4
1:44
:736
16:4
1:49
:754
16:4
1:57
:764
16:4
2:05
:265
16:4
2:14
:159
16:4
2:21
:229
16:4
2:25
:084
16:4
2:33
:295
16:4
2:40
:816
16:4
2:50
:761
16:4
2:53
:485
16:4
2:58
:402
16:4
3:07
:605
16:4
3:16
:879
16:4
3:22
:396
16:4
3:28
:805
16:4
3:34
:344
16:4
3:39
:451
16:4
3:45
:459
16:4
3:49
:866
16:4
3:53
:491
16:4
3:54
:864
16:4
3:59
:009
16:4
4:05
:037
16:4
4:13
:620
16:4
4:19
:109
16:4
4:23
:935
16:4
4:25
:667
16:4
4:28
:191
16:4
4:34
:199
16:4
4:41
:209
16:4
4:44
:274
Time
RB
_S
tatu
s
-130
-120
-110
-100
-90
-80
-70
-60
StatusID
RSCP
CPICH Ec/No and RB Status (Set2)
0
100
200
300
400
16:4
1:39
:209
16:4
1:44
:245
16:4
1:49
:252
16:4
1:56
:252
16:4
2:02
:351
16:4
2:11
:234
16:4
2:19
:786
16:4
2:21
:789
16:4
2:28
:799
16:4
2:35
:809
16:4
2:43
:821
16:4
2:51
:702
16:4
2:54
:256
16:4
2:59
:204
16:4
3:07
:875
16:4
3:16
:387
16:4
3:21
:895
16:4
3:27
:894
16:4
3:32
:901
16:4
3:37
:549
16:4
3:43
:416
16:4
3:48
:454
16:4
3:51
:289
16:4
3:54
:502
16:4
3:56
:325
16:4
4:00
:220
16:4
4:06
:039
16:4
4:15
:594
16:4
4:19
:619
16:4
4:23
:935
16:4
4:25
:637
16:4
4:28
:111
16:4
4:32
:206
16:4
4:39
:717
16:4
4:44
:114
Time
RB
_S
tatu
s
-24
-19
-14
-9
-4
StatusID
Ec/No
Sf8
sf16
sf32FACHIdle
Sf8
sf16
sf32FACHIdle
RB Status Statistics(vs EcNo)
0.00%
20.00%
40.00%
60.00%
80.00%
100.00%
120.00%
> -4 -4 to -6 -6 to -8 -8 to -10 -10 to -12 -12 to -14 -14 to -16 -16 to -18 < -18
Ec/No [dB]
sf8
sf16
sf32
100.00%
0.00%0.00%
51.03%
38.30%
10.67%
40.72%
47.55%
11.73%
30.34%
56.40%
13.26%
17.03%
57.16%
25.81%
11.54%
56.09%
32.37%
11.32%
37.74%
50.94%
5.21%
18.75%
76.04%
6.98%
4.65%
88.37%
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
> -4 -4 to -6 -6 to -8 -8 to -10 -10 to -12 -12 to -14 -14 to -16 -16 to -18 < -18
Ec/No [dB]
RB Status Statistics(vs EcNo)
sf32
sf16
sf8
384 128 64
RB Status for each Ec/No
≒-7 ~ -8 ≒-14 ~ -15
43 © 2005 Nokia V1-Filename.ppt / yyyy-mm-dd / Initials
Module 7 – Parameter Optimisation
Summary
• Parameter optimisation is not a substitute for RF
Optimisation
• In optimisation we have to consider the balances
between power (resources) and success/speed
• Call Setup can be improved by improving Cell Selection
and Reselection, SRB Rate and ATO
• Call retention can be improved by adjusting SHO
parameters at the expense of resource usage
• DyLO can affect the measured throughput from surveys
Recommended