The document presents a comprehensive analysis of WCDMA congestion, discussing its causes and methodologies for identifying and mitigating congestion within UMTS networks. Key congestion types include channel element congestion, downlink power, code, and IUB congestion, with specific metrics and actions recommended for each type. The analysis highlights the importance of resource management and suggests various optimization techniques to enhance network accessibility and stability.

1. Wcdma Congestion Analysis

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Abstract
› Technology: WCDMA
› Service Function: Optimization
› Standard Process: Congestion Analysis (CE, DL Power, Code, Iub)
› Congestion Types
 Channel Element(CE) Congestion(DL/UL)
 DL Power Congestion
 Code Congestion
 Iub Congestion

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Overview
 In UMTS the radio resource management functions are jointly handled in two different
protocol layers, the Radio Resource Control (RRC) and the Medium Access Control (MAC).
Congestion control functions are performed in the RRC layer. Therefore congestion control
requires strong interactions between the radio interface protocol layers, including measurement
reports which are transmitted, as well as reconfiguration procedures. In a simulation
environment different radio resource reconfiguration procedures are evaluated for congestion
control.
 Congestion control is to ensure network stability and achieve a reasonably fair distribution of
the network resources amongst the users. The main objective of this audit is to identify the cells
contributing towards congestion and may in turn impact the Accessibility KPIs. Congestion
Check is performed at cluster level on weekly basis.

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Methodology
› For Congestion Check below is the standard flow for various resources utilized in the system:
›
› Extract pmdata for the specific counters related to the various radio resources in use in the
system. Counters for each resource are specified in the sections to follow.
› Identify the cells where resource shortage is seen based on the daily trend of the relevant
counters. Ideally 15 days trend to be considered.
› Extract XML dump for RNC from OSS Common Explorer Utility.
› Parse XML dump using NEPA & export the MO class containing the relevant parameter/network
configuration to be optimized for improved resource utilization in Excel format.
› Provide parameter modification for relevant parameters in line with customer (Orange France)
guidelines.

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Main Affected Accessibility KPI’s due to Congestion:

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Types of Resource Congestions Checked:
DL Transmitted Carrier Power
DL Channelization Code
UL / DL HW (CE)
FAILURE AFTER ADM
Iub

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Main Counters for the Congestion Analysis per resource required:
Congestion
Analysis

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1. DL Power Congestion
› WCDMA Networks TCP (Tx Carrier Power) is always an important resource. Available RBS Downlink TCP is limited by
MCPA capability (20W, 30W & 40 W)
›
› FAILURE Counters:
– RRC : pmNoRrcReqDeniedAdmDlPwr
– RAB : pmNoFailedRabEstAttemptLackDlPwr
›
› CRITERIA:
– ADMISSION REJECTION : Power > pwradm
– CONGESTION REJECTION : Power > pwradm+pwroffset
›
› Action:
– Check and align the Power parameters & DL attenuation parameters.
– Increase the value for pwrAdm+ pwrOffset and could be less than 95%
– Optimize the parametrs minPwrRl, minPwrMax, interPwrMax, maxPwrMax, maximumTransmissionPower.
– If other carrier cell is not congested then share traffic by Qoffset (Idle mode).
– If other carrier is congestion also, then check neighbor cells and try to off load traffic by reducing Qoffset values.
– Do physical optimization incase of overshooting

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2. DL Code Congestion
› WCDMA Code tree is considered as one of the important Resource.
› Sample Code Tree Usage
FAILURE Counters:
RRC : pmNoRrcReqDeniedAdmDlChnlCode
RAB : pmNoFailedRabEstAttemptLackDlChnlCode
CRITERIA:
ADMISSION REJECTION : code > dlcodeadm
Action:
Increase dlCodeAdm.
Reduce the SRB Value from 13.6 to 3.4 [Parameter – standaloneSRBselector]
Reduce the values for sf4Adm, sf8Adm, sf16Adm to free codes for other users.

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3. Channel Element (CE) Congestion(UL/DL):
› CE is short for Channel Element and is a measure of board capacity and radio bearer (RB)
capacity cost.
› Uplink CE is offered by RAXB and downlink CE is offered by TXB.
› CE is also controlled by LICENSE.
› Both EUL and R99 are consumed CE resource. The table in the right shows the CE
consumption of services. When the consumption reaches the Max, the CE congestion is
triggered.
› To expand the CE recourse, we can get more license permission. If limited usage either,
more hardware is required.

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a. UL CE Congestion
› FAILURE Counters:
– RRC : pmNoFailedRabEstAttemptLackUlHwBest
– RAB : pmNoFailedRabEstAttemptLackUlHW
› CRITERIA:
– ADMISSION REJECTION : CE Usage > Available CEs in DUW
› Action:
– Check availableRbsChannelElementsUplink & licenseCapacityRbsChannelElementsUplink to align with
customer specified license capacity.
– Rejection in only one DUW (out of available two DUWs) - Tune the ulLicFractBbPool2 based on the CE
Utilization
– Recommend for CE addtion.
– Reduce the values for sf4AdmUl, sf8AdmUl, sf16AdmUl.
– Switch off the 2ms TTI for EUL eulServingCellUsersAdmTti2.
– Increase UlHwAdm.

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b. DL CE Congestion
› FAILURE Counters:
– RRC : pmNoFailedRabEstAttemptLackDlHwBest
– RAB : pmNoFailedRabEstAttemptLackDlHW
› CRITERIA:
– ADMISSION REJECTION : CE Usage > Available CEs in DUW
› Action:
– Check availableRbsChannelElementsDownlink & licenseCapacityRbsChannelElementsDownlink to
align with customer specified license capacity.
– Rejection in only one DUW (out of available two DUWs) - Tune the dlLicFractBbPool2 based on CE
utilization.
– Recommend for CE addtion.
– Reduce the values for sf4Adm, sf8Adm, sf16Adm.
– Increase DlHwAdm.

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4. FAILEDAFTERADM
› Number of Radio Resource Control (RRC) or Radio Access Bearer (RAB) establishment requests failed
after being admitted by admission control.
› RRC and RAB establishment failures which occur after admission control can be due to
– Iub transport Network blocking
– Node blocking
– NBAP RL setup failure (RAX or TXB congestion)
– Channel Code Allocation Failure (code not available)
– Core transport network congestion or failures
– Timeout in the UE, RNC or RBS
– Invalid parameter settings or Software Bug
›
› FAILURE Counters:
– pmNoFailedafteradm
› Action:
– Check Failures are due to Congestion in Transport or Radio
– Check and clear Hardware issues
– Check and clear Iub Link outages.
– Recommended to restart NodeB/RNC

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5. Iub Congestion:
› FAILURE Counters:
– pmDchFramesTooLate
– pmDchFramesReceived
– pmNoRabEstBlockTnSpeech
– pmNoRabEstBlockTnPsIntNonHs
– pmNoRabEstBlockTnPsIntHs
– pmNoRrcConnReqBlockTnPs
– pmNoRrcConnReqBlockTnCs
› Formulae:
› Below mentioned is the formula for checking the Iub Congestion based on the Frames
›
›
› Action:
– Check Failures are due to Congestion in Transport or Radio
– Check and clear Hardware issues
– Check and clear Iub Link outages
– Need to inform the Onsite Eng. to raise Ticket for Site Visit.
100
Re

ceived
s
pmDchFrame
+
sTooLate
pmDchFrame
sTooLate
pmDchFrame

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Tools:
› Dump Extraction: OSS Common Explorer.
› FTP Client: Filezilla.
› Dump Parsing: Nepa.
› Audit Processing: MS Excel.
› pmData extraction: ENIQ/BO/ITK etc.