WCDMA Radio Optimization
Contents Radio planning planning optimizat optimization ion ............ .................. ............ ............ ............ ............ ............ ...... 3-14 Quality of Service .............................................................. 15-22 Measurement and statistics collection ............................... 23-29 KPI .................................................................................... 30-32 Accessibility....................................................................... Accessibility....................................................................... 33-38 Retainability....................................................................... 39-44 Integrity Integrity ............ .................. ............ ............. ............. ............ ............ ............ ............ ............ ............ .......... .... 45-47 HSDPA-HSU HSDPA-HSUPA PA ............. ................... ............ ............ ............ ............ ............ ............ ............ ......... ... 48-55
-2-
Radio planning optimization
-3-
Antenna height
Since WCDMA performance is interference limited the cell dominance areas should be kept as controlled as possible lf the antenna is located “too high” (no proper tilting) then The cell gathers more traffic and external interference and thus the “effective” capacity is decreased Produced interference decreases the capacity of the surrounding network Also surrounding network’s service probability is negatively effected
Antenna azimuth
Natural obstacles and buildings should be used to create good dominance areas for WCDMA cells This improves the SHO performance and decrease interference Example of a UMTS cell, that is naturally bordered (wall effect) by buildings
Antenna height simulation
When re-using the GSM sites, analysis should be made whether the UMTS antennas should be positioned lower This analysis is done with simulations and visiting the site locations in practise Part of network reused few +40meter GSM antenna heights
High UMTS antenna positions lowered to 25-35m
Dominance areas become clear, so less interference is introduced and HO performance is better. Capacity is increased and performance enhanced!
-4-
Antenna tilt
ln addition to antenna height, downtilting is very important physical means for interference minimizing in WCDMA Basic rule of designing antenna tilt is that the height of the antenna should be selected with respect to the wanted amount of cell range If the cell range with respect to available antennas and their tilting with a feasible amount of tx-power becomes too large to suit the network plan, then the antenna must be lowered According to experience, the analysis should start with the optimum tilting and not by reducing the tx-powers of the cell, which can be optimized after the tiltings are done Horizontal plane h
Antenna tilt
According to experience even 15 degrees of downtilting is not impossible (lf the radiation pattern of the antenna supports it), although in practice not very often needed.
There has also been lot of discussion of a potential need to change the tilts often during the network lifecycle (even regularly)
However practice have not shown such need if the tilts are design well from the start with help from simulations
But once WCDMA gets congested this might be given another look (Remote tilts).
-5-
Sectorisation
According to simulations and analysis, sectorisation of WCDMA site helps to improve capacity of the network However, as permissions for additional antennas are quite hard to come by, e.g. 6-sector sites might be very rare Antenna 3 Other to own dB cell Beam interference width ratio, i
Sectorisation can increase the capacity if correct beamwidth antennas are selected and SHO properly controlled
Served users
Soft handover overhead
UL coverage probability (outdoor to indoor) For 8/64/144 kbps
OMNI CASE Omni
0.79
240
28%
70/32/40%
THREE SECTORS CASE 120 900 650
1.33 1.19 0.88
0
441 461 575
39% 35% 34%
85/50/59% 87/55/62% 86/59/62%
FOUR SECTOR CASE 1200 900 650 330
1.72 1.49 1.09 0.92
489 510 604 691
54% 51% 41% 40%
90/62/68% 92/67/72% 92/70/71% 88/65/64%
SIX SECTOR CASE 120 900 650 330
2.18 1.97 1.43 1.15
0
593 627 758 880
64% 59% 55% 48%
95/75/79% 96/80/82% 96/80/81% 93/76/76%
Served users in DL
UL coverage probability (outdoor to indoor) for 8/64/144 hbps
Master head amplifier
The MHA can be used in WCDMA in the uplink direction to compensate for the cable losses and thus reducing the required mobile station’s transmit powers Using MHA the performance in uplink can be improved also in WCDMA systems. However in practice if the network turns to downlink limited then the MHA won’t help
Other to Served own cell users in interference UL ratio, I
THREE SECTORED CASE, 65O antenna No MHA With MHA
0.60 0.61
1038 1064
807 746
93/78/78% 95/82/82%
FOUR SECTTORED CASE, 65O antenna No MHA With MHA
0.73 0.73
1089 1107
884 846
96/86/85% 98/89/89%
SIX SECTORED CASE, 33O antenna no MHA with MHA No MHA 4dB cable losses WITH mha 4 DbN CABLE LOSSES
-6-
0.88 0.90
1124 1132
1052 1021
97/87/86% 98/90/90%
0.88
1109
1057
95/83/82%
0.90
1132
1016
98/90/90%
Master head amplifier
Increases uplink coverage/capacity in low loaded network Compensates for feeder and combiner losses in the uplink direction, increasing coverage for suburban, rural and road sites where antennas are in very high positions and the feeder lines are long Allows UEs to reduce transmission power level With heavily loaded network (i.e. high interference) the benefit of the mast head amplifier is negligible Also in downlink limited 3G networks (DL oriented traffic, users in cell edge, DL tx-power per user low e.g. in for high bit rate indoor users) the usage of mast head amplifier is not justified Needs extra space in the masts and increase the wind load
MHA is sometimes called as Tower Mounted Amplifier (TMA)
Transmit power increase
-7-
Transmission powers
Default transmission powers are determined by the equipment vendors. In initial phase of the planning Transmission powers of TCHs and CCHs needs to be set Maximum UE transmission power is to be defined In DL the power tuning between TCHs and CCHs has effect on network performance More power to CCHs —> better channel estimation, which improves the Eb/No performance and thus improves coverage More power to TCHs —> better capacity Rule of thumb: 15-20% of DL total power is used for CCHs Maximum UE transmission power should be set to 21-24 dBm (network operation and battery life) Most important control channel is the common pilot channel (CPICH)
Transmission powers
Also other control channels beside CPICH need power (for example BCH) to enable correct functioning of the system All the other common control channels are powered in relation to the P-CPICH The goal of allocating power to the common channels is to find a minimum power level needed for each channel to secure the network operation and to provide the same cell coverage area as with CPICH, but not to waste any capacity left for the traffic channels.
Typical DL power recommendations Channel
Allocated power
Max power of the Node B
43 dBm
CPICH
Max power-10dB
PCH
Max power-11 …-13 dB
SCH
Max power-11 …12dB
FACH
Max power-12…-13dB
BCH
Max power-11 …13dB
-8-
Recall: Some control channels
PCH: Paging channel initiates the communication from network side SCH: Synchronization channel FACH: Forward access channel carries control information to terminals that are known to be located in the given cell. ls used to answer to the UL RACH message. BCH: Broadcast channel carries network specific information to the given cell (random access slots for UL, antenna configuration etc) PICH: Paging indicator channel is used to provide sleep mode operation for UE AICH: Acquisition indicator channel is used to indicate the reception of RACH CCPCH: Primary and secondary common control physical channels (P-CCPCH and S-CCPCH) are physical channels that carry BCH, FACH and PCH.
Transmission powers • • • • • •
P-CCPCH transmitted with activity factor 0,9 S-CCPCH transmitted with activity factor 0,25 SCHs transmitted with activity factor 0,1 AICH, PICH and CPICH are transmitted continuously The BCH is transmitted on the P-CCPCH and FACH and PCH on the S-CCPCH The BCH is transmitted on the P-CCPCH continuously expect during the 256 first chips, when the P-SCH and S-SCh are transmitted we can assume 0,1 activity factor for the SCHs and 0,9 for the P-CCPCH Channel
Allocated power
Power out of the total common channel powers
Power out of the maximum Node B transmission power (20W)
P-SCH
0,331W
S-SCH
0,224W
PICH
0,1W
AICH
0,126W
P-CCPCH
0,245W
S-CCPCH
1,165W
CPICH
1W
31%
5%
All common ch.
3,191W
100%
16%
-9-
Carrier addition
Adding a carrier to less transmit power per carrier, if no additional PA is installed Additional carrier can also be used for e.g. optimisation of indoor coverage with clever network planning and parametrisation (not with power reduction) Even with less transmit power, there is a capacity gain possible especially for high traffic areas (low cell range) Actual gain produced is heavily dependent on the traffic mix
Carrier configuration 1C>2C 2C>3C
Dense Urban 350m 92% 41%
DL Capacity gain Urban Suburban 550m 1700m 87% 37%
77% 27%
Rural 7km 60% 15%
Indoor coverage aspects
Most of the UMTS users are indoors. Therefore good indoor coverage is vital for UMTS success In GSM indoor coverage is pretty straightforward to plan. However this is not the case with WCDMA Indoor coverage provided from outdoor base stations is highly sensitive to cell load increase in WCDMA If outdoor users is given a high-data rate bearer this can result in loss of coverage to users indoors INDOOR COVERAGE ANALYSIS • Consider different RAB / coverage scenarios • Carefully estimate the effect of cell loading to the coverage • Use repeaters if possible • Assess the need for indoor sites • Carry out real-life verification of the planning - 10 -
Pilot pollution
Pilot pollution is faced on a certain area when there is no clearly dominant CPICHs over the others. The pilot pollution creates an abnormally high level of interference, which is likely to result in the performance problems Increased interference level Poor service quality, decreased throughput or increased delay Decreased service access Frequent changes in Active Set and potential risk for unnecessary handovers. Higher non-controllable load
Pilot pollution
The yellow dots represent points where 4-5 CPICHs were received within 6dB window As Active Set size is typically 3, in this situation the rest of the Pilots produce unnecessary interference
Pilot pollution
Pilot pollution can be (at least partly) avoided by planning the CPICH powers and SHO parameters so that throughout the network there is only 2-3 CPICHs available for the UE’s, strong enough to be included in the Active Set. All CPICH outside Active Set should be clearly weaker Antenna design, height and tilt are selected carefully Balanced UL & DL SCH/DCH power adjustments
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Neighbour cell relations
The Monitored Set is also called as a Neighbour List. This list can be defined in network planning and it can be later changed in network optimization. The list of neighbours play an important role since WCDMA is interference limited. Insufficient planning of neighbour relations will lead to unnecessary high interference E.g. if suitable SHO candidate is not in the monitore set and thus it is not selected to active set then it’s turning to a “pilot poIIuter” On the other hand, unnecessary neighbours increase signalling and effects the SHO selection negatively Accurate neighbour relations planning is much more important than in GSM In GSM it is possible to “hide” cell planning mistakes by frequency planning, in CDMA the such inaccuracies will effect the system capacity The effort saved in frequency planning is spent in more detailed cell planning
Neighbour cell relations
The parameters to control the neighbour relations and the algorithms how system evaluates neighbours for cell lists, depend on vendor minimum CPICH RSCP or Ec/lo Ec/lo margin maximum number of neighbours A neighboring set (or monitored set) is defined for each cell Utilise planning tools automatised functions and check with drive tests Optimise according to CPICI-l coverage and SHO parameters UE monitors the neighboring set that may contain Intra-frequency monitored list: Cells on the same WCDMA carrier (Soft HO) Inter-frequency neighbor list: Cells on another WCDMA carrier (hard HO) Inter-system neighbor list: For each neighboring PLMN Missing neighbour can be detected during drive tests If the best cell shown in the 3G scanner does not enter the active set missing neighbour - 12 -
Incilude the missing cell to neighbour list if it’s wanted to active set or change cell plan if FIO
SHO optimisation
Soft/Softer HO planning and correct operation is one of the most important means of optimizing WCDMA networks The importance is high because of the high biterate (pathloss sensitive) and RT (delay sensitive) RABs SHO is measured in terms of probability, the percentage of all connections that are in SHO state The probability is effected by network planning and parameter settings
SHO optimisation SHOs have effect to the network performance Advantages Required to avoid near-far effects Coverage increases when more distant users can connect Capacity can be “increased” if more users can be connected Alongside with PC, SHO is the main interference migitation means in WCDMA Inconvenient Requires more connections, thus eats DL transmission power and decreases capacity Introduces more interference to DL Increases the traffic in lub 40% SHO probability1.4 times the traffic!
- 13 -
SHO optimisation
Probability for soft HO should be set to 30-50% and for softer HO to 5-15%, depending on the area Too high SHO% results in excess overlapping between cells —> other-cell interference increases —> capacity decreases Too high SHO% also leads to poorly utilised network capacity (unnecessary links) With too low SHO% the full potential of network is not utilised and transmission powers cannot be minimized —> trouble with interference SHO performance is planned with a planning tool and optimised by measurements in live network. In early stage SHO% can be planned high, since the traffic density is smaller. With increasing traffic coverage decreases and SHO areas become smaller. SHO% can be tuned with related parameters and dominance areas SHO most important in urban areas due to serious shadowing
Summary KPI Indicator
KPI
Coverage
Interference
Measured RSCP > -88 dBm over 97% of area (value should be adapted based on required margins) Measured Ec/No > -9 dB over 95% of area
Cell overlap
Cell overlay
< 3 cells over 95% of area
Qualitative
Cell Overshoot
No cell detected above -111 dBm (CPICH RSCP) No cell fragmentation detected
Integrity of cell coverage Best server plot
KPI target example
Clean boundary without unnecessary change of best server
- 14 -
Quality of Service
- 15 -
Quality of Service – – definitions (1) QoS (ITU-T): << The collective effect of service performance which determines the degree of satisfaction of a user of the service>>. Network Performance, NP (ITU-T): << The ability of a network portion to provide the functions related to communication between users>>.
Quality of Service – – definitions (2) User domain: throughput, accuracy, dependability (reliability, availability), … Provider domain: delay, loss, utilisation, … User QoS Requirements
QoS offered by Provider
QoS experienced By Users
QoS achieved by User
Quality of Service –definitions (3) QoS and NP, Performance network (ITU Rec. E800)
- 16 -
Quality of Service and user satisfaction Commercial offer
Competition
Trends
User expectations in terms of QoS
Users satisfaction
Technical QoS
Network performance
Non-technical QoS
Terminal performance
Sales points
Radio Access Bearer QoS
- 17 -
Customer care
Radio Access Bearer
Main task of the UTRAN is to create and maintain RAB for communication between UE and CN. RAB is build up in order to give for CN elements an illusion about fixed communication path to UE. The network builds up the end-to-end QoS connection from small pieces, which compose a complete chain without bottlenecks These pieces are called Bearers When the connection is set up, the network elements negotiate the QoS requirements of the bearers set up between them The result is a compromise, in which the QoS requirements and network’s capacity is taken into account.
UMTS QoS Classes Traffic Class
Example application
Conversation class
Speech and video calls
Streaming class
Real-time streaming video
Interactive class
Web surfing
Background class
File downloading, e-mails
UMTS QoS Classes Traffic Class
Properties
Conversation class
Minimum fixed delay, no buffering, symmetric traffic, guaranteed bit rate Minimum variable delay, buffering allowed, asymmetric, guaranteed bit rate Moderate variable delay, buffering allowed, asymmetric traffic, no guaranteed bit rate Big variable delay, buffering allowed, asymmetric traffic, no guaranteed bit rate
Streaming class
Interactive class
Background class
- 18 -
UMTS QoS Parameters Parameter
Explanation
Maximum bit rate
Defines the maximum bit rate when delivering information between end points of UMTS bearer (<2Mbps) Defines the bit rate that the UMTS bearer must carry between its end points
Guaranteed bit rate
Allowed transfer delay Set the limits for delay (>80ms) QoS negotiable
QoS of some services are not negotiable (speech), packet data services admit various QoS classes
Some values of QoS UMTS parameters classes Traffic class
Conversation Streaming Interactive
Background
Maximum <2048 throughput (kb/s) Scheduling Yes/No Max. SDU size <_ 1500 or 1502 (octers) Corrupted SDU Yes/No delivery Residual BER 5* 10-2, 10-2, 5* 10-2, 10-2, 4* 10-3, 10- 4* 10-3, 105, 5, 5* 10-3, 10-4, 5* 10-3, 10-3, 10-6 10-4, 10-5, 10-6 6* 10-8 6* 10-8 SDU error rate 10-2, 7*10-3, 10-1, 10-2, 10-3, 10-4, 10-3, 10-4, 10-3 7* 10-3, 10-3, 10-6 10-6 10-4, 10-5 10-4, 10-5 Transfer delay (ms)
100 –maximum 250 – maximum value value
- 19 -
QoS Negotiation UTRA (NB, RNC)
UE
CN
E2E service request
Maximum bit rate Guaranteed bit rate Transfer delay QoS negotiable (y/n)
UMTS bearer service: Request for UMTS QoS Class Maximum bit rate Guaranteed bit rate Transfer delay QoS negotiable (y/n) RAB assignment request RRM: Admission control
Radio bearer and radio link establishment
QoS negotiation RAB assignment response
UMTS Bearer service with negotiated QoS
QoS in UMTS
In early UMTS Release 99 all conversational and streaming class traffic were offered over the CS bearer Voice RT multimedia (e.g. videotelephony) In early Release 99 only Interactive and background class traffic utilisises the PS bearer Release 4 capable networks introduce some streaming class traffic on PS bearer as well Release 5 brings along a full portofolio of PS bearers also utilised for conversation traffic
- 20 -
QoS in UMTS
The QoS over the air interface is implemented by matching each radio bearer with a transport channel whose format set defines the QoS parameters The mapping is performed during the establishment of the RAB RNC performs the mapping of RAB characteristics to actual resource requirements (vendor dependent) Example of mapping for web service, which belongs to the interactive class
Parameters
Interactive Class
Radio Resource mapping
Maximum bit rate
128 kb s
SF=16
Maximum SDU size
1500
Ma to Trans ort formats
Residual BER
10 -6
1/3 turbo encoder
Transfers Dela
NA
Interleaver=40 or 80 msec
Guaranteed bit rate
64 kb s
SF=16
Deliver order
es
Use Acknowled ed RLC
SDU Error Ratio
1%
Set appropriate threshold
Deliver of errorneous
NO
Use Acknowled ed RLC
QoS in UMTS
Operators can define the wanted QoS profile (in HLR) per subscriber Users can be categorised (QoS differentiation) for various tariffing schemes Traffic handling priorities can be set (THP)
Business Remote office Basic free time Traffic class All four allowed All four allowed Only converational (voice calls) and background Max bit rate 400 kbps 800 kbps 64 kbps Guaranteed bit 384 kbps 64 kbps 12 kbps rate Allowed THPs THP 1 (e.g. for THP 2 (e.g. for THP 3 e-mail file tranfer) download)
- 21 -
QoS in UMTS
- 22 -
Measurement and statistics collection
- 23 -
Measurement tools typology Field Measurements Generic Measurement tools
OMC counters Specific System Measurements
Passive capture tools Calls generators
A. Field measurements Drive test equipment measures and softwares
GPS
Controler
Energy Processing
Mobile QoS test equipment
Man to machine interface
Poor Coverage example
- 24 -
External antennas
Poor Cell Dominance example
Pilot Pollution example
- 25 -
Example of neighbor missing (Ec/Io)
Corner effect (Ec/Io)
- 26 -
QVOICE QVS
PSTN / ISDN Cellular Network
QVP-Server
Data collection Post processing
QVP-Client
3 parts: QVM (QV Mobile), QVS (QV Stationary) et QVP (QV Post processing).
B. System measurements OMC measurements Specific • Alcatel: RNO • Siemens: SPOTS • Ericsson: TEMS Analyser •…
Generic • APIC from Metrica • MyCom from MYCom • AirCom • NetAct SQM: Nokia • OVPI: HP (for IP equipments)
- 27 -
KPI processing tools Commercial tools:
• BiVision • ADC/Metrica, • NetAct (Nokia, for 3G) • UTRAN Network and service Analyzer (Tektronix)
• Actix
Analysis based on OMC-R counters Analysis tools using these counters (generally they are specific). Example: RNO or NPA of Alcatel, SPOTS from Siemens, etc.
- 28 -
Passive tools examples • • • • •
HP : Ovis (data services tests, producers KPIs). RamCom : Network Consultant (A, Gb, Gi, Gn, Iub, Iur, Gi and Gn interfaces) Trafica (NetAct from Nokia) Ipanema : Ipanema (2,5 G and 3G data traffic). Cigale (Astellia): 2 and 3G traffic.
GIS display
- 29 -
KP I
- 30 -
Optimization process Performance measurements Update of parameters, site configuration
Key Performance Indicators (KPI)
Network tuning
• Reasons that lead to otimisation:
Performance analysis
– Improve the performance – Business reasons (cost-effective) – Troubleshooting
Network statistics • • • •
Network statistics are collected from different network elements with counters Different types of counters are used KPIs are needed to provide information of the network performance Raw counter data too detailed to be used in monitoring and optimisation (Some counters can be used as KPIs)
KPI definition • •
•
•
KPIs are composed from several counters KPI categories – Accessibility – Retainability – Integrity Documentation of KPIs is important – Same KPI can be defined from different counters or formula can be incorrect Measurement period must be reasonable – Too much averaging if too long – Not enough statistical information if too short - 31 -
KPI Example
Optimisation based on KIPs: • Optimisation is performed for each category • Find the worst performing cells • Find the reasons behind the poor performance • Make the changes in the network • Monitor the performance after the changes
- 32 -
Accessibility
- 33 -
Accessibility : call set-up MS Originating Call Setup Random Access RRC Connection Setup Service Request Authentication Security
RAB Assignment
Accessibility workflow
Performance Measurements
Alarms Cell Availability Counters
Performance Analysis
Idle mode RRC Connection Random Access NAS RAB Assignment
Recommendation & Im lementation
Verification of changes
Squal, Srxlev, qQualmin, qRxLevMin, maxTxPowerUl, t3212, t3312, aichPower, powerOffsetP0, preambleRetransMax, constantValueCprach
O t h e r M o d u l e s
pmTotNoRrcConnectCsSucc pmTotNoRrcConnectPsSucc pmNoRabEstablishAttempt pmNoRabEstablishSuccess pmNoPageDiscardCmpLoadC pmNoPagingAttemptUtranRejected
Worst performing cell for CS and PS pmTotNoRrc ConnectReq CsSuccess pmTotNoRab EstablishS uccess < RAB > × 100 × pmTotNoRrc ConnectReq Cs pmmTotNoRa bEstablish Attempt RAB < >
pmTotNoRrc ConnectReq PsSuccess pmTotNoRab EstablishS uccess < RAB > × 100 × pmTotNoRrc ConnectReq Ps pmmTotNoRa bEstablish Attempt < RAB >
- 34 -
Service success set up rate (CS) Speech 100x
pmTotNoRrcConnectReqCsSucc x pmTotNoRrcConnectReqCs
pmTotNoRabEstablishSuccessSpeech pmmTotNoRabEstablishAttemptSpeech
Circuit-Switched 64 100x
pmTotNoRrcConnectReqCsSucc x pmTotNoRrcConnectReqCs
pmTotNoRabEstablishSuccessCS64 pmmTotNoRabEstablishAttemptCS64
Circuit-Switched 57 100x
pmTotNoRrcConnectReqCsSucc x pmTotNoRrcConnectReqCs
pmTotNoRabEstablishSuccessCS57 pmmTotNoRabEstablishAttemptCS57
Service success set up rate (PS) Packet-Switched Data Streaming 100 x (Y) x
pmTotNoRabEstablishSuccessPacketStream + pmRabEstablishSuccessPacketStream128 pmTotNoRabEstablishAttemptPacketStream + pmRabEstablishAttemptPacketStream128
Where Y =
pmTotNoRrcConnectReqPsSuccess PmTotNoRrcConnectReqPs
Packet-Switched Data pmTotNoRabEstablishSuccessInteractive 100 x (Y) x pmTotNoRabEstablishAttemptPacketInteractive + HS1_HardHO_Flow
Where Yx
pmTotNoRrcConnectReqPsSuccess pmTotNoRrcConnectReqPs
HS1_HardHO_Flow= pmNoOutgoingHsHardHoAttempt – pmNoHsHardHoReturnOidSource -pmNoIncomingHsHardHoAttempt - pmNoHsHardHoReturnOldChTarget
- 35 -
Idle mode paging Successful First and Repeated Page attempts of total number of first attempts, Paging success rate in aMSC 100 x
NPAAG1RESUCC + NPAG2RESUCC NPAG1GLTOT + NPAG1LOTOT
Paging intensity per cell in a RNC (if RNC, LA and RA consist of exact same cells): pmCnlnitPagingToldleUeLa + pmCninitPagingToldieUeRa + pmCnlnitPagingToldleUe Measurement period x total number of cells in tha t RNC
Random access: preamble detection Number/percentage of false detections, which is the case that preamble is detected but there is no enough energy in message part, due to noise on the random access channel for a carrier (it could be due to loss of AICH, wrong recognition of preamble or loss of RACH message part after the UE sends message out):
pmNoPreambleFalseDetection or pmNoPreambleFalseDetection x100% pmPositiveMessages
Random access: AICH detection Percentage of getting AICH but no RRC connection setup, excluding cell (re)selection:
No of AICH_ACK-No of RRC connection setup-No of cell (re)selection during RRC establishment No of AICH_ACK
- 36 -
x100%
Admission control: DL transmission carrier power DL transmission carrier power Average DL TX power for a cell-carrier: 102
i pmTransmittedCarrierPower i x 2
=0
102
pmTransmittedCarrierPower i
=0
Admission control: UL RSSI Average UL RSSI for a cell-carrier: 62
[pmAverageRssi i x (0.5xi – 110.5 )]
=0
62
pmAverageRssi
i
=0
Admission control: Air Interface Speech Equivalent (ASE) Average UL ASE for a cell:
Average DL ASE for a cell:
- 37 -
pmSumOfSampleAseUI pmNoOfSampleAseUI
pmSumOfSampleAseDI pmNoOfSampleAseDI
Admission control: code allocation Code allocation failure for SFn, where n is the spreading factor for a cell could be found in the following formula (as an example the SF 128 was used):
pmNoDIChCodeAllocFailureSF128
x100%
mNoDIChCodeAllocAttem tSF128
Admission control: compressed mode How many users are in compressed mode? Well the average number of users in compressed mode for a cell:
pmSumCompMode pmSampesCompMode
Admission control: load sharing Ratio between RRc connection returning and redirection due to load sharing for a cell:
pmNoOfReturingRrcConn mNoLoadSharin RrcConn
The failures can be observed by the successful rate of directed retry to GSM for a cell:
pmNoDirRetrySuccess mNoDirectionRetr Att
- 38 -
x100%
Retainability
- 39 -
Service retainability workflow
Performance Measurements
Performance Analysis
Recommendation & Im lementation
pmSystemRabRelease pmNormalRabRelease pmNoSysRelSpeechULSynch pmNoOfTermSpeechCong pmNoSysRelSpeechSoHo
Verification of changes
ReleaseConnOffset maxTxPowerUl,SirMax, MinPwrRl, treselection, timetotrigger1, reportingrange1
O t h e r M o d u l e s
UL out of Synch Congestion control, SHO functions IFHO functions IRAT Handovers
Dropped call rate CS Speech 100x
pmNoSystemRab ReleaseSpeech (pmNoNormalrAB ReleaseSpeech + pmNoSystemRab ReleaseSpeech)
Circuit-switched 64 100x
pmNoSystemRabReleaseCs64 (pmNoNormalRab ReleaseCs64 + pmNoSystemRab ReleaseCs64)
Circuit-switched Streaming 100x
pmNoSystemRabReleaseCsStream (pmNoNormalrRab ReleaseCsStream + pmNoSystemRab ReleaseCsStream)
Dropped call rate PS Packet Switched data Streaming 100x
pmNoSystemRab ReleasePacketStream + pmNoSystemRab ReleasePacketStream128 (pmNoNormalRabReleasePacketStream + pmNoSystemRabReleasePacketStream + pmNosystemRabReleasePacketStream128)
Packet Switched data Interactive 100x
pmNoSystemRab ReleasePacket (pmNoNormalRab ReleasePacket + pmNoSystemRab ReleasePacket)
- 40 -
Minutes per drop CS Speech 100x
Sp_U_User pmNoSystemRab ReleaseSpeech
x number of minutes
Circuit-switched 64 100x
Cs64_U_User pmNoSystemRab ReleaseCs64
x number of minutes
Circuit-switched Streaming 100x
Cs57_U_User
x number of minutes pmNoSystemRab ReleaseCsStream
Minutes per drop PS Packet Switched data Streaming 100
Pstr_P8_U_User pmNoSyatemRab ReleasePacketStream + pmNoSystemRab ReleasePacketStream128
x No of minutes
Packet Switched data Interactive 100
Plntdch_U_User+PlntHs_U_User+PlntFach_U_User pmNoSystemRab ReleasePacket
x No of minutes
Packet Switched data Interactive HS 100
PlntHs_U_User pmNoSystemRab ReleaseHs
x No of minutes
Handover failure rate The following formula shows the failure rate for RL addition/replacement to active set 100x
pmNoTimesCellFailAddToActSet (pmNoTimesCellFailAddToAct + pmNoTimesRlAddToActSet
- 41 -
Handover failure rate: HS cell change The following metric measures the success rate for HS Cell Change in target cell
100x
pmHsCcSuccess pmHsCcAttempt
Handover failure rate: out of synchronization Shows fraction of drop due to uplink Out of Sync reason. 100x
(pmNoSysRelSpeechULSynch) (pmNoNormalRabReleaseSpeech + pmNoSystemRabReleaseSpeech)
Handover failure rate: missing neighbor 100x
pmNoSysRelSpeechSoHo (pmNoSystemRabReleaseSpeech + pmNoNormalRabReleaseSpeech)
Shows fraction of speech drop due to HO action when a valid or non-valid cell cannot be added to active set. This includes also drop due to missing neighbour. 100x
pmNoSysRelSpeechNeighbr (pmNoSystemRabReleaseSpeech + pmNoNormalRabReleaseSpeech)
Shows fraction of speech drop due to missing neighbour reason when a non-valid cell cannot ne added to active set.
- 42 -
Inter-frequency handover failure rate (CS) Drop due to IHO failure for speech: Outgoing IFHO failure when UE failed to return to present active set.
100x
pmFailNonBlindInterFreqHoFailRevertCsSpeech12 pmAttNonBlindInterFreqHoCsSpeech12
Inter-frequency handover failure rate (PS) Drop due to IFHO failure for PS less or equal to 64 kbps: Outgoing IFHO failure when UE failed to return to present active set. 100x
pmFailNonBlindInterFreqHoFailRevertPsInteractiveLess64 pmAttNonBlindInterFreqHoPsInteractiveLess64
Drop due to IFHO failure for PS greater than 64 kbps: Outgoing IFHO failure when UE failed to return to present active set. 100x
pmFailNonBlindInterFreqHoFailRevertPsInteractiveGreater64 pmAttNonBlindInterFreqHoPsInteractiveGreater64
Drop due to IFHO failure for PS streaming and others: Outgoing IFHO failure when UE failed to return to present active set. 100x
pmFailNonBlindInterFreqHoFailRevertStreamingOther pmAttNonBlindInterFreqHoStreamingOther
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IRAT handover The following metric measures hard handover success rate between UtranCell and target GSM cell for speech calls. The formula is considering the GsmRelation. 100x
pmNoSuccessOutIratHoSpeech pmNoAttOutIratHoSpeech
The following metric measures hard handover success rate between UtranCell and target GSM cell for streaming calls. The formula is considering the GsmRelation. 100x
pmNoSuccessOutIratHoCs57 pmNoAttOutIratHoCs57
IRAT handover The following metric measures hard handover success rate between UtranCell and target GSM cell for Multi-RAB calls. The formula is considering the GsmRelation. 100x
pmNoSuccessOutIratHoMulti pmNoAttOutIratHoMulti
The following metric measures cell change failure rate between UtranCell and target GSM cell for PS calls when the UE successfully returns to UtranCell. The formula is considering the GsmRelation. 100x
pmNoOutIratCcReturnOldCh pmNoOutIratCcAtt
Congestion Shows fraction of speech drop due to cogestion action 100x
(pmNoOfTermSpeechCong) (pmNoNormalRabReleaseSpeech + pmNoSystemRabReleaseSpeech)
Shows fraction of video call drop due to cogestion action 100x
(pmNoOfTermSpeechCong) (pmNoNormalRabReleaseCs64 + pmNoSystemRabReleaseCs64)
- 44 -
Integrity
- 45 -
Service integrity workflow Performance Measurements
Performance Analysis
BLER counters and Down Switching counters
Recommendation & Implementation
BLER, power, SIR parameters
Test the settings
Verification of changes
Check statistics If not OK, roll back
Throughput
pmFaultyTransportBlocksBcUl pmTransportBlocksBcUl pmNoOfSwDownNgCong PmNoOfSwDownNgAdm PmDl Traffic volume counters
BLER The method for finding worst performing cells is based on top to down analysis. Initial worst 10-15 performing cells can be identified based on the Uplink Block Error rate before combining. pmFaultyTranspoertBlocksBcUL 100x
pmTransportBlocksBcUI
Throughput Average throughput per cell and RAB in the DL, excluding HSDPA: Throughput =
pmDlTrafficVolume pmSumRabEstablish
pmSamplesRabEstablish
*ROPsec
RAB efficiency excluding HSDPA The RAB efficiency can also be checked RABEfficiency =
Actual Bitrate per RAB Nominal Bitrate per UeRc=x
UeRc stands for different RAB’s UeRc=2, Speech UeRc=3, Video Call UeRc=4, Packet Common Channel UeRc=5, PS 64/64 UeRc=6, PS64/128 UeRc=7, PS 64/384 UeRc=10 multirab Speech+PS 0 or PS 64/64).
- 46 -
Payload counters Radio UL Payload counter DL Payload counter Connection type Speech pmUITrafficVolumeCs12 pmUITrafficVolumeCs12 PS64/64 pmUITrafficVolumePs64 pmUITrafficVolumePs64 PS64/128 pmUITrafficVolumePs128 pmUITrafficVolumePs128 PS64/384 pmUITrafficVolumePs384 pmUITrafficVolumePs384 CS 57.6 pmUITrafficVolumeCs57 pmUITrafficVolumeCs57 (streaming) CS 64 (UDI) pmUITrafficVolumeCs57 pmUITrafficVolumeCs57 Speech/PS pmUITrafficVolumeCs12Ps64 pmUITrafficVolumeCs12Ps64 64 multirab PS pmUITrafficVolumePsCommonpmUITrafficVolumePsCommon Common
- 47 -
HSDPA-HSUPA
- 48 -
HSPA Key features-AMC Cood CQI Bad CQI
High Code Effective Rate
Good coverage
Low Code Effective Rate
Channel Quality Feedback (CQI) UE measures channel quality (SNR or Ec/No) and reports to Node B every 2ms or longer time. Node B chooses modulation scheme, transport block size and code effective rate based on CQI
Bad coverage
AMC could improve radio bandwidth and fit for high speed radio transmission.
HSPA Key feature – – System resource Resource allocation Reasonable resource allocation can improve throughput performance
OVSF Code resource
Minimum Code available for HSPA but not for R99, so this resource can’t allocated too much to avoid no code for HSPA access channel.
DCH Code HSPA Maximum For R99 and HSPA access and traffic channel Code
Power resource
Threshold for R99 load control, which should not be allocated too much to avoid no power for HSPA user
- 49 -
HSPA Minimum Code
HSPA Key feature-Scheduling Transmission slot 2 ms UE2 UE1
UE3
Data transmission slot
Mobility management
- 50 -
Sample message flow to begin HSDPA operation UE
Bode B
RNC
1
UTRAN decides to start HSDPA for the UE Measurement Control message (Setup Event 1d) 2 Measurement Report message (Report Event 1d) Radio link reconfiguration prepare 3 Radio link reconfiguration ready Radio link reconfiguration commit Radio Bearer Reconfiguration message 4
User plan data can flow on the HS-DSCH Radio Bearer Reconfiguration Complete message
Sample message flow to stop HSDPA operation UE
1
Bode B
RNC
UTRAN decides to stop HSDPA but keep DCH for the UE due to: • Low Downlink data activity • High UE mobility
Radio link reconfiguration prepare
2
Radio link reconfiguration ready Radio link reconfiguration commit Radio Bearer Reconfiguration message 3
User plane data only flows on the DCH Radio Bearer Reconfiguration message
- 51 -
Cell change triggering with event 1d Ec/No
Cell 1
Cell 2
H steresis
Time-to-
Cell chan e
HS-DSCH on Cell 1
A
HS-DSCH on
B
C
Time
Differences about information collection between R99 and HSPA
- 52 -
HSPA dimensioning optimization
HSPA Optimization target – – Improve CQI HSPA RF optimization target
R99 RF optimization target
CQI
RSCP & Ec/Io
Make sure that CQI is distributed as appropriate proportion. Cell edge throughput requirement could be fulfilled in the door coverage area.
Make sure that cell gets target coverage probability
CDI
9>CQI
15>CQI9
CQI15
User experience
Poor
Fair
Good
Equipment Ec/Io
-15dB
-15 dB - -9dB
- 53 -
-9dB
Performance Optimization Procedure The three kind of KPI of should be paid more attention HSPA CALL SUCCESS RATIO HSPA HANDOVER SUCCESS RATIO HSPA THROUGHPUT PERFORMANCE KPI Collection DT/CQT/Statistics
Performance optimization
Problem Analyze
• Modify the load balance policy
• Code congestion
• Carry out smart admission algorithm such as DRD or Downsize Access
• Power overload • HSPA subscriber number overload
• Power and lub bandwidth congestion means the capacity should be expanded
• lub bandwidth congestion • Unsupported configuration by UE
• The higher bit rate such as 13.6K DCH channel can help to improve access performance
Inter-freq Handover is the most difficult for HSPA mobility optimization
- 54 -
HSPA Throughput Optimization The Power and Codes available for HS-PDSCH, the lub bandwidth and RF environment of UE position will all impact throughput user got. Available Codes for HSPA Available Power for HSPA
Available lub backhaul for HSPA The Data Power to be transmitted Node B
DATA DATA DATA
Check oint
CQI
The air environment condition
DATA
RNC
CQI
CQI
The data should be delivered
GSN Process ability
CQI The web sever performance.
SGSN/GGSN App Sever
- 55 -
Firewall
