admission and failures after admission

Admission And Failures After AdmissionAdmission And Failures After Admission
Mirna El-Sigaan
GSDC Lebanon
2010-1-19
ABSTRACT
This presentation explains in details Admission and Failures After Admission, covering counters involved and useful troubleshooting examples.
It would benefit beginners and people looking in to Network Performance and Optimization.
Slide title 32 pt Text 24 pt Bullets level 2-5 20 pt !"# $%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~¡¢£¤¥¦§¨©ª«¬®¯°±²³´¶·¸¹º»¼½ÀÁÂÃÄÅÆÇÈËÌÍÎÏÐÑÒÓÔÕÖ×ØÙÚÛÜÝÞßàáâãäåæçèéêëìíîïðñòóôõö÷øùúûüýþÿŒœŠšŸƒˆ˜–—‘’‚“”„†‡•…‰‹›⁄€™−≤≥ Do not add objects or text in the footer area
2010-1-19
AGENDA
Admission Control Flow
- Troubleshooting Examples
2010-1-19
Admission Control And Failures After Admission
Admission Control is one of the most important Functions in the Capacity Management of WCDMA networks, which aims to control the load in the WCDMA radio access network.
Admission Control blocks new incoming calls as well as handover attempts when the load in the system is high (by taking the input from set of monitors either located in the RBS or in the CRNC), by using measurements of UL interference, DL power as well as the actual number of users.
2010-1-19
Admission Control: Resources Involved
When a new resource is request is made, Admission control will check the amount of the resources needed by the requester and the system load based on the below main monitors which are updated during the addition, deletion and modification of existing radio connections in the cell:
DL TX Cell power( total non HS power used in the cell)
Air Interface Speech Equivalent in UL and DL
DL and UL spreading factor (SF) usage
DL Channelization Codes usage
RBS Hardware utilization in the UL and DL (Channel Elements)
Number of users in compressed mode
Number of HS users in the cell
UL Received total Wide Band Power (RTWP)
2010-1-19
Admission Control Flow
- Admission Control will compare the amount of estimated resources required to establish the new connection, to the available resources and configured limits set up by the operator and a response is sent out to grant or the new radio link access to the cell
2010-1-19
Admission Blocking
Admission blockings can be triggered during 2 stages, either at the RRC establishment or during the RAB establishment phase.
To differentiate at which stage the blocking is triggered, we have to check the following set of counters.
Slide title 48 pt Slide subtitle 30 pt
Admission Counters
2010-1-19
Admission Counters: RRC Stage
In the below figure, we can see Admission Counters that might be pegged at the RRC stage:
-Counters pegged when an RRC Request is blocked by admission:
-pmNoReqDeniedAdm
-pmNoRrcReqDeniedAdm
-pmNoRrcCsReqDeniedAdm
-pmNoRrcPsReqDeniedAdm
-Counters pegged when an RRC Request is blocked by admission due to Licensed capacity:
-pmNoFailedRrcConnectReqHw
-pmNoFailedRrcConnectReqCsHw
-pmNoFailedRrcConnectReqPsHw
-Counters pegged when an RRC Request is blocked by admission due to Transport and Node Congestion:
-pmNoRrcConnReqBlockTnPs
-pmNoRrcConnReqBlockTnCs
-pmNoRrcConnReqBlockNodePs
-pmNoRrcConnReqBlockNodeCs
2010-1-19
-Counters that show the total number of rejected RRC Requests:
-pmTotNoUtranRejRrcConnReq
-pmNoRejRrcConnMpLoadC
2010-1-19
Admission Counters
2010-1-19
Description:
-Number of RAB establishments and RRC requests denied due to admission control.
Condition:
-Incremented by 1, when admission to this cell is denied to a UE.
-The reason for denial can be power, code utilization limits, ASE limit, or compressed mode limit reached.
MO Class:
-Utran Cell
2010-1-19
-Number of RRC requests denied by admission control.
The counter is trigged when an RRC connection request with any cause value is denied by Admission Control .
Condition:
-Incremented by one after denied admission after an RRC CONNECTION REQUEST with any cause value has been received.
MO Class:
-Utran Cell
2010-1-19
Condition:
-Incremented by one when RRC connection request with cause 'Originating Conversational Call' or 'Terminating Conversational Call' or 'emergency call' is denied by Admission Control
MO Class:
-Utran Cell
2010-1-19
Condition:
-Incremented by one after denied admission after an RRC CONNECTION REQUEST with any of the cause values 'Originating Interactive Call', 'Terminating Interactive Call', 'Originating Background Call', 'Originating Subscribed Traffic Call' or 'Terminating Background Call' has been received.
MO Class:
-Utran Cell
2010-1-19
RRC PS denied by Admission
High number of RRC Failures
2010-1-19
Description:
-Number of RRC requests denied by admission control due to insufficient licensed capacity in the RBS.
Condition:
-Incremented by one when an RRC connection request with any cause value is denied by Admission Control due to insufficient licensed capacity in the RBS.
MO Class:
-Utran Cell
2010-1-19
Description:
-Number of CS calls denied by admission control due to insufficient licensed capacity in the RBS.
Condition:
-Incremented by one when an RRC connection request with cause 'Originating Conversational Call', 'Terminating Conversational Call' or 'emergency call' is denied by admission control due to insufficient licensed capacity in the RBS.
MO Class:
-Utran Cell
2010-1-19
Description:
-Number of PS calls denied by admission control due to insufficient licensed capacity in the RBS.
Condition:
-Incremented by one when an RRC connection request with cause 'Originating Conversational Call', 'Terminating Conversational Call' or 'emergency call' is denied by admission control due to insufficient licensed capacity in the RBS.
MO Class:
-Utran Cell
2010-1-19
Description:
-Number of RRC Connection Setup attempts for Packet Switched calls that fail due to Transport Network blocking.
Condition:
-Incremented by one at the establishment of an RRC Connection Request with Establishment Cause = Originating/Terminating Interactive or Background or Originating Subscribed Traffic Call, fails due to congestion on the user plane (AAL2)or control plane (UniSaal or SCTP) of the transport network as a result of user dimensioned transport network resource shortages.
MO Class:
-Utran Cell
2010-1-19
Description:
-Number of RRC Connection Setup attempts for Circuit Switched calls that fail due to Transport Network blocking.
Condition:
-Incremented by one at the establishment of an RRC Connection Request with Establishment Cause = Originating/Terminating Conversational or Emergency , fails due to congestion on the user plane (AAL2)or control plane (UniSaal or SCTP) of the transport network as a result of user dimensioned transport network resource shortages.
MO Class:
-Utran Cell
2010-1-19
Description:
-Number of RRC Connection Setup attempts for Packet Switched calls that fail due to node blocking.
Condition:
-Incremented by one at the establishment of an RRC Connection Request with Establishment Cause = Originating/Terminating Interactive or Background or Originating Subscribed Traffic Call, fails due to node blocking, i.e. node configuration error, node limitation or transport network layer service unavailability.
MO Class:
-Utran Cell
2010-1-19
Description:
-Number of RRC Connection Setup attempts for Circuit Switched calls that fail due to node blocking.
Condition:
-Incremented by one if the establishment of an RRC Connection Request with Establishment Cause = Originating/Terminating Conversational or Emergency, fails due to node blocking, i.e. node configuration error, node limitation or transport network layer service unavailability.
MO Class:
-Utran Cell
2010-1-19
Condition:
-Incremented by one when an RRC Connection Request is received and a connection setup to the RBS fails due to the following reasons:
- no internal UE identity is available in the RNC
- MP load control function
- any internal parameter retrieving or calculations fail
- a downlink channelization code fails to be allocated .
MO Class:
-Utran Cell
2010-1-19
Example: RRC Requests Rejected by UTRAN
The above case shows sudden degradation in RRC success rate, most of the failures were rejected by UTRAN
Utilization of Channel Elements Reached its peak value at that hour
2010-1-19
-Number of rejected RRC connections due to MP load control.
Condition:
-Incremented by one when sending a RRC message RRC Connection Reject with rejection cause congestion, when the congestion cause has been indicated by internal load control.
MO Class:
-Utran Cell
Admission Blockings
2010-1-19
Admission Counters: RAB Stage
In the below figure, we can see Admission Counters that might be pegged at the RAB stage:
-Counters pegged when an RAB Request is blocked by admission due to lack of resources:
- pmNoFailedRabEstAttemptLackDlChnlCode
- pmNoFailedRabEstAttemptLackDlHw
- pmNoFailedRabEstAttemptLackUlHw
- pmNoFailedRabEstAttemptLackDlPwr
- pmNoFailedRabEstAttemptLackDlAse
- pmNoFailedRabEstAttemptLackUlAse
- pmNoFailedRabEstAttemptExceedConnLimit
- pmNoFailedRabEstAttemptLackDlPwr
-Counters to monitor the number of RAB failures due to Transport Network Congestion:
- pmNoRabEstBlockTnSpeech
- pmNoRabEstBlockTnPsStrNonHs
- pmNoRabEstBlockTnPsIntNonHs
2010-1-19
Admission Counters: RAB Stage
-Counters to monitor the number of RAB failures due to Transport Network Congestion:
- pmNoRabEstBlockNodeSpeechBest
- pmNoRabEstBlkNodePsIntNonHsBest
- pmNoRabEstBlkNodePsStrNonHsBest
2010-1-19
Admission Counters
2010-1-19
Description :
Number of failed RAB establishment attempts due to lack of DL channelization codes.
Condition :
Incremented by one when admission control fails with reject reason lack of DL channelization codes.
MO Class :
Utran Cell.
2010-1-19
Description :
- Number of failed RAB establishment attempts due to lack of DL hardware resources.
Condition:
- The counter is incremented for the IubLink containing the first cell to fail admission in the active set.
MO Class :
Utran Cell.
2010-1-19
Description :
-Number of failed RAB establishment attempts due to lack of UL hardware resources.
Condition:
The counter is incremented for the IubLink containing the first cell to fail admission in the active set.
MO Class :
Utran Cell.
2010-1-19
Description :
- Number of failed RAB establishment attempts due to lack of UL ASE.
Condition:
- Incremented by one when admission control fails with reject reason lack of UL ASE.
MO Class :
Utran Cell.
2010-1-19
Description :
Number of failed RAB establishment attempts due to lack of DL ASE.
Condition :
Incremented by one when admission control fails with reject reason lack of DL ASE.
MO Class :
Utran Cell.
2010-1-19
Description :
Number of failed PS RAB establishment attempts due to exceeding the configured connection limit when allocating Spreading Factors
Condition :
Incremented by one when admission control fails with reject reason value SF8, SF16, or SF32
MO Class :
Utran Cell.
2010-1-19
Description :
- Number of failed RAB establishment attempts due to lack of DL power.
Condition:
- Incremented by one when admission control fails with reject reason lack of DL power.
MO Class :
Utran Cell.
2010-1-19
Description:
- Number of RAB establishment attempts for RAB-type Speech that are blocked due to TN congestion or TN failure, counted on the blocking cell.
Condition:
- Incremented by one when the establishment of a Speech RAB fails due to UNI-SAAL or AAl2 congestion, IP resource limitations or blocking as a result of user dimensioned transport network configured capacity. The counter is incremented for the first cell in which the failure occurred but only if the cell is in the SRNC.
MO Class:
- Utran Cell
2010-1-19
Description:
-Number of RAB establishment attempts for RAB-type PS Streaming that are blocked due to TN congestion or TN failure, counted on the blocking cell. .
Condition:
-Incremented by one when the establishment of a PS Streaming RAB, not including PS Streaming for HS, fails due to congestion on the user plane (AAL2) or control plane (UniSaal or SCTP) of the transport network layer as a result of user dimensioned transport network capacity
MO Class:
-Utran Cell
2010-1-19
Description:
- Number of RAB establishment attempts for RAB-type PS Interactive that are blocked due to TN congestion or TN failure, counted on the blocking cell.
Condition:
- Incremented by one when the establishment of a PS Interactive RAB, not including PS Interactive for HS, fails due to congestion on the user plane (AAL2) or control plane (UniSaal or SCTP) of the transport network layer as a result of user dimensioned transport network capacity.
MO Class:
- Utran Cell
2010-1-19
Description:
- Number of RAB establishment attempts for RAB-type PS Interactive that are blocked due to TN congestion or TN failure, counted on the blocking cell.
Condition:
- Incremented by one when the establishment of a PS Interactive RAB, not including PS Interactive for HS, fails due to congestion on the user plane (AAL2) or control plane (UniSaal or SCTP) of the transport network layer as a result of user dimensioned transport network capacity.
MO Class:
- Utran Cell
2010-1-19
Description:
- Number of RAB establishment attempts for RAB-type CS Speech that are blocked due to node congestion or node failure. Incremented in the best cell in the active set.
Condition:
- Incremented by one when the establishment of a CS Speech RAB fails due to node configuration error, node limitation, or transport network layer service unavailability.
MO Class:
- Utran Cell
2010-1-19
Description:
- Number of RAB establishment attempts for RAB-type PS Interactive that are blocked due to node congestion or node failure. Incremented in the best cell in the active set.
Condition:
- Incremented by one when the establishment of a PS Interactive RAB, excluding PS Interactive for HS, RAB fails due to node configuration error, node limitation or transport network layer service unavailability.
MO Class:
- Utran Cell
2010-1-19
Description:
- Number of RAB establishment attempts for RAB-type PS Streaming that are blocked due to node congestion or node failure. Incremented in the best cell in the active set .
Condition:
- Incremented by one when the establishment of a PS Streaming RAB for HS, excluding PS Streaming for HS, fails due to node configuration error, node limitation, or transport network layer service unavailability .
MO Class:
- Utran Cell
Failures After Admission
2010-1-19
Description :
Number of Radio Resource Control (RRC) or Radio Access Bearer (RAB) establishment requests failed after being admitted by admission control.
Condition :
If either a RRC or RAB establishment procedure fails AFTER the admission has been granted for the establishment (RRC or RAB) - this counter will be incremented in the cell or cells where the UE is located.
The counter is not stepped for D-RNC cells.
This counter will increment on both Circuit switched failures and Packet Switched failures.
MO Class :
Utran Cell.
2010-1-19
Example: Failure After Admission
The above case shows sudden degradation in the PS RAB successful rate, most of the failures were recorded as failures after admission
2010-1-19
RAB and RRC Failures:
- If a call fails after being admitted by admission, either at RRC or RAB stages, the counter will be pegged.
Transport Network Blocking and Node Blocking Over Iub: High number of Failures After Admission might occur due to congestion or node miss configuration.
Core Transport Network Congestion: Accessibility issues are observed on all sites at the RNC without major issues with Iub congestion (especially at peak hour)
Parameter Settings: Failures after admission might occur if the admission thresholds does not match to the original planned capacity
Hardware and Transmission Problems
Channel Code Allocation Failures
2010-1-19
For RRC/RAB Establishment, the number of failures of RRC/RAB Establishments after admission can be monitored on UTRAN cell level using:
Number of RRC/RAB failures after admission = pmNoFailedAfterAdm
RAB and RRC Establishment failures which occur after admission control can be due to TN and non TN related,
timeout in the UE, RNC or RBS.
invalid parameter settings.
Coverage issues
If the connection is suddenly lost with a RAB you will get a system RAB release
If it disconnects with RRC you may get an abnormal Disconnect message which is failure to setup a call.
2010-1-19
2010-1-19
Example: Failure's Due To Bad Coverage
-The above case shows degradation in the RRC PS success rate, most of the failures were recorded as failures after admission.
-The result of the trace shows that the connection is lost due to loss of synchronization between the UE and the Network due to bad coverage.
Coverage plot of cell U077213
2010-1-19
Description: Transport Network Blocking And Node Blocking Over Iub
Transport Network Blocking: is defined as blocking due to congestion on the userplane or control plane of the transport network as a result of resource shortage in the operator dimensioned transport network.
Node blocking: is defined as blocking due to a node configuration error (node B, RXI and RNC), node limitation or transport network layer service unavailability.
During a call setup, one or more AAL2 connections must be setup as a part of:
-RAB Establishment
-RRC Establishment
-Addition of a Radio Link to the active set
Any failure in establishing the AAL2 connection, will pmNoFailedAfterAdm is then pegged.
2010-1-19
Description: Transport Network Blocking and Node Blocking Over Iub
Depending on the volume of traffic per service or RAB, certain QoS could be congested at the AAL2. All RABs excluding HSDPA are configured to use Class A or Class B being these two mostly impacted by congestion.
Most of the time Class B is the first QoS to get congested leading to failures after admission events.
Failure to setup an AAL2 connection is considered as transport network blocking for these radio network features. Since different AAL2 QoS classes are used for different radio services, it is possible to see how much each group of radio services is impacted by AAL2 setup connection failures either by using the RN counters on UtranCell level. (refer to previous slides)
2010-1-19
Example: Failure's Due To Bad Transmission Problem
- High number of RRC “ CS and PS” failures caused due to IMA issue.
- Most of the failures were recorded as failures after.
2010-1-19
Description : Parameter’s To Be Checked In Case Of Failures After Admission
Check if the admission thresholds match to the original planned capacity Parameters:
-beMarginDlPwr
-pwrAdm
-pwrAdmOffest
2010-1-19
Description: Hardware Usage (Channel Elements)
Blockings due to lack of CE’s could be due to:
- Insufficient UL (RAX board) or DL (TXB board) capacity
- Software license limitation
- dlHwAdm
- Locked or faulty Board (RAX or TXB board)
sF4AdmUl : parameter value can be reduced if insufficient UL CE is caused by too many users with UL 384kps. If this does not resolve UL CE usage problems then we must perform RAX board upgrade.
sf8Adm: parameter value can be reduced if insufficient DL CE is caused by too many users with UL 384kps.
The average channel element usage in the UL can be monitored form the following RBS counters:
- pmApomcOfRachCap
- pmApomcOfRakeRecUsed
- pmApomcOfUlLinkCap
The average channel element usage in the DL can be monitored form the following RBS counters:
- pmApomcOfMdsr
- pmApomcOfMdlr
- pmApomcOfSpreadersUsed
2010-1-19
Example: Failure's Due To Lack Of Channel Elements
High number of PS RAB failures caused due to lack of channel elements.
- Most of the failures were recorded as failures after.
2010-1-19
Example: Failure's Due To Locked RAXB
RAXB Locked: The above case shows sudden degradation in the PS RAB successful rate, where most of the failures were recorded as failures after admission.
2010-1-19
Example: Failure's Due To Faulty Board
Faulty Boards: The above case shows sudden degradation in the PS RAB successful rate, where most of the failures were recorded as failures after admission.
2010-1-19
Description: Channalization Codes Utilization
Failed RAB establishments due to lack of DL Channelization Codes may increase on cells once HS is deployed as 35% of the available channel codes are used by HS-DSCH.
The number of HS-DSCH codes can be decreased by decreasing the value of numHsPdschCodes.
The values of the following parameters should be checked in case of CC blockings:
- beMarginDlCode
- dlCodeAdm
In sites where high blockings are recorded we must go to second carrier implementation.
2010-1-19
Example: Failure's Due To Lack Of CC
High number of PS RAB failures caused due to lack of channalization codes.
- Most of the failures were recorded as failures after admission.
2010-1-19
Example: Failure's Due To Lack Of Power
High number of PS RAB failures caused due to lack of power.
- High Number of failures were recorded as failures after admission.
2010-1-19
SUMMARY
- Hardware Problems
- Transmission Problems
- Node Misconfiguration
- Iub Congestion
2010-1-19
2010-1-19

admission and failures after admission

Documents