failed after adm

17
FAILURES AFTER ADMISSION ON ERICSSON UMTS SYSTEM Juan Berrizbeitia and others (see references)

Upload: nagarjuna-daggubati

Post on 15-Jan-2016

799 views

Category:

Documents


138 download

DESCRIPTION

Failed After Adm

TRANSCRIPT

Page 1: Failed After Adm

FAILURES AFTER ADMISSION ON ERICSSON UMTS SYSTEM

Juan Berrizbeitia and others (see references)

Page 2: Failed After Adm

Top right corner for field-mark, customer or partner logotypes. See Best practice for example.

Slide title 40 pt

Slide subtitle 24 pt

Text 24 pt

Bullets level 2-520 pt

© Ericsson AB 2009 FAILURES AFTER ADMISSION ON ERICSSON UMTS SYSTEM2009-02-092

Contents

Background information Possible causes for failures after admission Troubleshooting aids

Page 3: Failed After Adm

Top right corner for field-mark, customer or partner logotypes. See Best practice for example.

Slide title 40 pt

Slide subtitle 24 pt

Text 24 pt

Bullets level 2-520 pt

© Ericsson AB 2009 FAILURES AFTER ADMISSION ON ERICSSON UMTS SYSTEM2009-02-093

Background information: pmNoFailedAfterAdm counter

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 at the cell or cells where the UE is located.

– The counter is not pegged for D-RNC cells.– This counter will increment on both Circuit switched failures

and Packet Switched failures.

MO Class :– Utran Cell.

Page 4: Failed After Adm

Top right corner for field-mark, customer or partner logotypes. See Best practice for example.

Slide title 40 pt

Slide subtitle 24 pt

Text 24 pt

Bullets level 2-520 pt

© Ericsson AB 2009 FAILURES AFTER ADMISSION ON ERICSSON UMTS SYSTEM2009-02-094

Background information: pmNoFailedAfterAdm at Admission control counter flowchart

Page 5: Failed After Adm

Top right corner for field-mark, customer or partner logotypes. See Best practice for example.

Slide title 40 pt

Slide subtitle 24 pt

Text 24 pt

Bullets level 2-520 pt

© Ericsson AB 2009 FAILURES AFTER ADMISSION ON ERICSSON UMTS SYSTEM2009-02-095

Background information: When is this counter pegged?

When a new resource request is made, Admission control checks DL power, ASE, Codes ,etc.- to determine if the new resource request will be granted.

It then adds the new load to those monitors (as they need to be included in the next resource request processing).

If for some reason, the resource request fails then Admission Control must remove those loads (associated with the request) from the load monitors. It is at this time that pmFailedAfterAdm is incremented.

It is important to mention that transmission resources are not checked at admission control, therefore there is a high probability of having blocking due to lack of transmission resources.

Page 6: Failed After Adm

Top right corner for field-mark, customer or partner logotypes. See Best practice for example.

Slide title 40 pt

Slide subtitle 24 pt

Text 24 pt

Bullets level 2-520 pt

© Ericsson AB 2009 FAILURES AFTER ADMISSION ON ERICSSON UMTS SYSTEM2009-02-096

RRC/RAB Failures

This counter can include failures for reasons that are Transport Network (TN) related as well as not TN-related.

RAB and RRC establishment failures which occur after admission control can be due to

– timeout in the UE, RNC or RBS.– invalid parameter settings.– TN failure reasons. – 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.

Page 7: Failed After Adm

Top right corner for field-mark, customer or partner logotypes. See Best practice for example.

Slide title 40 pt

Slide subtitle 24 pt

Text 24 pt

Bullets level 2-520 pt

© Ericsson AB 2009 FAILURES AFTER ADMISSION ON ERICSSON UMTS SYSTEM2009-02-097

This counter will be increment on all cells for a failure on all Radio links that have had admission granted. So, when we have soft/softer handover and 3 RL in the AS are granted admission, then

– RAB failure will be pegged on one link (serving cell) &– pmNoFailedAfterAdm will be pegged on all 3 cells.

pmNoFailedAfterAdm at RAB setup

RAB set-up attempt is on Cell-A, but no success, then : -pmNoFailedAfterAdm will be incremented on all three cells( A, B& C) in active set. But, -RAB failure will only increment in the best cell in the active set (Cell-A)

(pegged)

SoHo

SoHo

pmNoFailedAfterAdm

(pegged)pmNoFailedAfterAdm

(pegged)pmNoFailedAfterAdm

(pegged)pmNoRabEstablishAttempt

(Serving Cell)

CELL A

CELL B

CELL C

Page 8: Failed After Adm

Top right corner for field-mark, customer or partner logotypes. See Best practice for example.

Slide title 40 pt

Slide subtitle 24 pt

Text 24 pt

Bullets level 2-520 pt

© Ericsson AB 2009 FAILURES AFTER ADMISSION ON ERICSSON UMTS SYSTEM2009-02-098

General causes for failures after admission

The counter pmNoFailedAfterAdm is pegged for the reasons stated below :

1. NBAP RL setup failure (RAX or TXB congestion)2. AAL2 setup failure (due to congestion or miss

configuration)3. Channel Code Allocation Failure (code not available)

Page 9: Failed After Adm

Top right corner for field-mark, customer or partner logotypes. See Best practice for example.

Slide title 40 pt

Slide subtitle 24 pt

Text 24 pt

Bullets level 2-520 pt

© Ericsson AB 2009 FAILURES AFTER ADMISSION ON ERICSSON UMTS SYSTEM2009-02-099

Failure After Admission: Iub Congestion

Possible solutions for Iub congestion: Enable Directed retry (short term solution) Correct possible AAL2 miss configuration at Node B, RNC and RXI or MSN (AAL2

profile must match in all three entities) Order new T1s (long term solution) Change AAL2 QoS configuration depending on services request volume (CS voice,

R99 data, HSDPA, etc)

Iub congestion is a common reason for high number of failures after admission events

Depending on the volume of traffic per service or RAB, certain QoS could be congested at the AAL2. All RABs excluding HSDPA are configured tu 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

Iub congestion could be caused by T1 issues Missconfigurations of AAL2 profile at the Node B, RNC or RXI/MSN can lead to Iub

congestion

Background information:

Possible indicators: Check for congestion at the Iub link Check for T1 issues and history of alarms of T1s (for intermittent T1 alarms). Ask

Utran help to check for T1 issues and alarms.

Page 10: Failed After Adm

Top right corner for field-mark, customer or partner logotypes. See Best practice for example.

Slide title 40 pt

Slide subtitle 24 pt

Text 24 pt

Bullets level 2-520 pt

© Ericsson AB 2009 FAILURES AFTER ADMISSION ON ERICSSON UMTS SYSTEM2009-02-0910

Failure After Admission: Core Transport Network Congestion

Possible solutions: This issue will require support from the client in order to determine high utilisation

over Iu-cs and Iu-ps links

Accessibility issues are observed on all sites at the RNC without major issues with Iub congestion (especially at peak hour) Congestion will be observed at Iu-cs (RNC<-->MGW) or Iu-ps (RNC<-->SGSN) links

Possible indicators: Signalling bearer rab (SRB) issues for either CS or PS would increment on these

cases. SRB failures for CS: 1-(pmNoIuSigEstablishSuccessCs / pmNoIuSigEstablishAttemptCs). SRB failures for PS: 1-(pmNoIuSigEstablishSuccessPs / pmNoIuSigEstablishAttemptPs)

Congestion will be observed at Aal2 access point (Aal2Ap) entity starting with “g” (note: Aal2Ap entities starting with “b” correspond to node b, starting with “r” corresponds for Iur links,etc)

Page 11: Failed After Adm

Top right corner for field-mark, customer or partner logotypes. See Best practice for example.

Slide title 40 pt

Slide subtitle 24 pt

Text 24 pt

Bullets level 2-520 pt

© Ericsson AB 2009 FAILURES AFTER ADMISSION ON ERICSSON UMTS SYSTEM2009-02-0911

Failure After Admission: Hardware Usage (Channel Elements)

Possible solutions: Check that ulHwAdm and dlHwAdm parameters are set to 100% Check numHsResources, numEulResources at the node B (long term solution) Reduce value of sf8Adm to 0 (short term solution) Order new RAX or TXB depending on the case Restart Node B and monitor performance if no obvious issues are found

Note: It is possible for lack of channel elements counters to increment even when there should be sufficient channel element capacity (for example due to a software bug in the software revision) so it is important to compare the channel element usage to the channel element capacity of the RBS to make sure that it makes sense for this to be the root of the problem

Lack of channel elements could be due to insufficient UL (RAX board) or DL (TXB board) hardware capacity Channel element capacity could be also software limited (software licenses configured at the RBS) Admission control is restricted by ulHwAdm and dlHwAdm parameters. They should be set at 100% so no hardware is limited for RRC/RAB setup.

Possible indicators: High number of events on LackDlChnlCode counter for lack of channel codes Congestion at RAX or TXB could be indicated by RBS counters (RBS universe in BO)

pmUlCredits and pmDlCredits respectively. Congestion per spreading factor (SF) can be also measured using pmSetupFailureSfXX RBS

counters from the BasebandPool (BBP) on the uplink (UL BBP) and the downlink (DL BBP).

Page 12: Failed After Adm

Top right corner for field-mark, customer or partner logotypes. See Best practice for example.

Slide title 40 pt

Slide subtitle 24 pt

Text 24 pt

Bullets level 2-520 pt

© Ericsson AB 2009 FAILURES AFTER ADMISSION ON ERICSSON UMTS SYSTEM2009-02-0912

Failure After Admission: Other

Possible solutions: Check for hardware failures (for example, failures on RAX and TXB boards) Check for neighboring sites. Remember that neighboring sites having AAL2

congestion can cause other cells to have high number of failures after admission (due to soft handoff)

Check that software revisions are up to date at the Node B Restart Node B and monitor performance if no obvious issues are found

If a site shows none of the previously described issues, then it is likely to be a more complicated problem to resolve; often relating to a software/hardware fault, or perhaps an external source of interference in the area.

Possible indicators: High number of events on LackDlHw would indicate issues

with TXB board and LackUlHw would indicate issues with RAX board.

Congestion at RAX or TXB could be indicated by RBS counters (RBS universe in BO) pmUlCredits and pmDlCredits respectively

Page 13: Failed After Adm

Top right corner for field-mark, customer or partner logotypes. See Best practice for example.

Slide title 40 pt

Slide subtitle 24 pt

Text 24 pt

Bullets level 2-520 pt

© Ericsson AB 2009 FAILURES AFTER ADMISSION ON ERICSSON UMTS SYSTEM2009-02-0913

Flowchart with proposed procedure

High number of pmNoFailedAfterAdm events

Iub congestion observed at

the site?

Double check presence of T1

issues with UTRAN

Address this issue with the customer

T1 issues at the site?

Lack of channel

elements at the site?

Other possible solutions: (when no T1 issues are present at the site)• Enable directed retry• Propose customer to consider changing AAl2 Qos configuration

Check with UTRAN for alarms or hardware

failures, specially at the TXB or RAX board

Alarm or hardware

failures at the TXB or RAX

board?

Re-start TXB or RAX board or

restart the site if issues not at the

boards

Channel Elements shortage

confirmed by Utran?

Recommend ordering new RAX

or TXB borads

Alarms present at the site?

Check if this alarms could be affecting accessibility at your

site and address alarm to the client

Check with the customer for

possible shortages at Iucs or Iups.

Note: shortages at Iucs and Iups would be affecting cs or ps accessibility on all sites at the RNC

Other possible solutions:• Reduce value of sf8Adm to 0

Shortages of Iucs or

Iups?

Note: channel element utilization must be greater than actual channel element capacity before recommending to order new hardware

Yes

Yes

Yes

Yes

Yes

Address this issue with the customer

YesNo

No

No

No

No

No

Yes

Check for neighboring sites, specially those having a high number of pmNoRabEstablishAttempt

Page 14: Failed After Adm

Top right corner for field-mark, customer or partner logotypes. See Best practice for example.

Slide title 40 pt

Slide subtitle 24 pt

Text 24 pt

Bullets level 2-520 pt

© Ericsson AB 2009 FAILURES AFTER ADMISSION ON ERICSSON UMTS SYSTEM2009-02-0914

Summary Proposed actions

Try to see if you have any HW alarms or issues at the site. Check AAL2/transmission issues:

– T1 issues– AAL2 missconfiguration at the Node B, RNC or RXI / MSN

Check for Iub congestion at problem site and sites around. Check for lack of channel elements or congestion at RAX or TXB

boards. If UTRAN support is provided, confirm T1 issues and alarms with

them (In case that counters may not be pegging properly)

Page 15: Failed After Adm

Top right corner for field-mark, customer or partner logotypes. See Best practice for example.

Slide title 40 pt

Slide subtitle 24 pt

Text 24 pt

Bullets level 2-520 pt

© Ericsson AB 2009 FAILURES AFTER ADMISSION ON ERICSSON UMTS SYSTEM2009-02-0915

Case study: Low PS accessibility on TXU04163

• Site TXU0416 had low PS accessibility on sector 3. Site had no alarms, no T1 issues and no Iub congestion. Only failures after admission are seen as explanation on low PS accessibility

• Neighbor site TXU0409 had T1 issues and packet drops on the same time frame possibly explaining low performance on TXU0416

Page 16: Failed After Adm

Top right corner for field-mark, customer or partner logotypes. See Best practice for example.

Slide title 40 pt

Slide subtitle 24 pt

Text 24 pt

Bullets level 2-520 pt

© Ericsson AB 2009 FAILURES AFTER ADMISSION ON ERICSSON UMTS SYSTEM2009-02-0916

References

“pmNoFailedAfterAdmDescription and Detail”: Arun Verma, Soontorn Banchongsirichareon, Jian Shiou Yong

“3G Cell Optimization”: unknown author Counters Flowchart from Alex LNA 108 2040 R5B, WCDMA RAN Performance Management Workshop

Page 17: Failed After Adm

Top right corner for field-mark, customer or partner logotypes. See Best practice for example.

Slide title 40 pt

Slide subtitle 24 pt

Text 24 pt

Bullets level 2-520 pt

© Ericsson AB 2009 FAILURES AFTER ADMISSION ON ERICSSON UMTS SYSTEM2009-02-0917