RRC Iu and Radio Failures

AIRCOM International

to

Orange

RRC Active IU Failures

And

RRC Access Radio Failures

RRC Active IU Failures

SummarySummary

According to network statistics a large percentage of failures in the RRC Active phase is attributed to problems with the Iu Interface.

Most RRC Active Iu failures occur while there was an active PS NRT RAB. This RAB would also fail with the Iu reason.

Correlation with NRT Connections drops while performing Inter-System HHO to GSM/GPRS was found.

From Drive tests done to specifically target the fault, it was seen that at the application level, the active FTP session was not terminated .i.e. user is not aware of the fault.

The possible scenarios that may lead this counter to increment even though no abnormal condition is present are:

The old Radio Link times out and the Nobe B sends a radio link failure message to the RNC before the Iu Release Command is received from the CN. The RNC then misinterprets the failure and pegs the Iu failure counter (unsure if an Iu Release request is issued towards the CN). If this is the case then RRC_CONN_ACC_FAIL_RADIO should be incremented instead.

A timer in the CN expires before the GSM/GPRS network informs the CN that the mobile has successfully connected to the GSM/GPRS network. The CN then sends the Iu Release Command to the RNC with a cause value that the RNC misinterprets.

Most likely this is a bug with the RNC but if not then the timers involved in the Inter-System HHO to GSM procedure should be checked to see if they allow enough time for the handover to complete.

Analysis Work FlowAnalysis Work Flow

A large percentage of Failures occurring in the RRC Active phase was being associated with problems with the Iu Interface.

KPI:

A search was conducted to find possible correlations between RRC_CONN_ACT_FAIL_IU and other Service Level counters.

Result : Correlation with the Iu failures for PS Background Service

- RAB_ACT_FAIL_PS_BACKG_IU

Now knowing that that the PS Background Service was reported as the main contributor, counters involving PS and NRT services were investigated.

Result : Correlation with NRT Connections drops while performing Inter-System HHO to GSM/GPRS

-

xxxxFAILACTCONNRRC

IUFAILACTCONNRRC

____

____

NRTxxxxHHOISDRPSCON _____


Since only CS drive tests were previously loaded into database, it was decided to use the e1f (HHO to GSM measurement) events in the log files and plot them on a map. This pinpointed the locations where intersystem handovers (and most likely where Cell Change Orders for PS calls) most often occur.

Cells near clusters of such events were checked to see if their Iu failures were high and if so added to a list of test candidates.

Cell GLN0177C1, which had a high RRC_CONN_ACT_FAIL_IU count, was selected to be tested.

The test was as follows: Start a PS background call on the cell and download a file using ftp. Drive towards an area where no or poor 3g coverage is found but

the 2g coverage is good.

A route was planned to force Inter-RAT Cell Reselections (3g to 2g and 2g to 3g) in order that the impact on the ftp session (user perception) and statistics (network perception) could be assessed.

StatisticsStatistics Statistics during a 20 day period as shown below for RNC

EnfieldComparison between RRC Active IU Failures and RAB Active IU Failures with ISHO PS Drops

0

50

100

150

200

250

300

350

400

Occ

ura

nce

s

con_drps_is_hho_all_nrt 63 166 78 51 89 136 165 102 90 85 119 172 162 94 181 151 332 107 192 172

rab_act_fail_ps_backg_iu 59 152 72 44 82 126 160 69 77 80 111 165 153 87 172 143 323 95 176 161

rrc_conn_act_fail_iu 77 161 84 60 98 170 176 83 104 93 123 280 235 116 210 183 348 113 191 179

01/01 02/01 03/01 04/01 05/01 06/01 07/01 08/01 09/01 10/01 11/01 12/01 13/01 14/01 15/01 16/01 17/01 18/01 19/01 20/01

Statistics (Test Candidate)Statistics (Test Candidate) Statistics during a 20 day period as shown below for

GLN0177C1

Comparision between RRC Active IU failures and RAB Active IU Failures with ISHO PS Drops

0

5

10

15

20

25

30

35

Date

Occu

ran

ces

RRC_CONN_ACT_FAIL_IU 1 1 1 0 1 2 0 3 0 8 6 3 2 9 1 1 1 1 0 31

RAB_ACT_FAIL_PS_BACKG_IU 0 0 1 0 1 2 0 1 0 7 3 3 0 9 1 0 1 0 0 31

CON_DRPS_IS_HHO_ALL_NRT 0 0 0 0 1 2 0 0 0 7 3 3 0 10 1 1 1 0 0 33

01/01 02/01 03/01 04/01 05/01 06/01 07/01 08/01 09/01 10/01 11/01 12/01 13/01 14/01 15/01 16/01 17/01 18/01 19/01 20/01

Test SetupTest Setup

From Orange London Drivetest Methodology Document1.1.1 PS Data collection

1.1.1.1 Methodology

Methodology wll be dependant upon which tests are being conducted. The following test are

defined:-

Data 1 (SF)

GPRS Attach

PDP Context Activation

500 byte ping

FTP Login

100kB FTP download

FTP Log off

PDP Context Deactivation

GPRS Detach

Data 2 (MF)

GPRS Attach


500 byte ping

FTP Login

500kB FTP download

FTP Log off


GPRS Detach

Data 3 (LF)

GPRS Attach


500 byte ping

FTP Login

1MB FTP download

FTP Log off


GPRS Detach

Data 4 (SF)

GPRS Attach


500 byte ping

FTP Login

100kB FTP upload

FTP Log off


GPRS Detach

Example Trace (Network View)Example Trace (Network View)

NodeB informs RNC of Loss of Sync with MS

PS-CN asks RNC to release resources

RNC does not respond in in 3 secs

PS-CN re-asks RNC to release resources

RNC Releases the IU connection

RNC sends Connection Release

But MS not on channel any more

Drive Test Example (Subscriber View)Drive Test Example (Subscriber View)13:17:38.397 DCCH PHYSICAL_CHANNEL_RECONFIGURATION

13:17:38.948 DCCH PHYSICAL_CHANNEL_RECONFIGURATION_COMPLETE

13:17:40.549 DCCH CELL_CHANGE_ORDER_FROM_UTRAN

13:17:41.050 BCCH SYSTEM_INFORMATION_TYPE_3

13:17:41.290 BCCH SYSTEM_INFORMATION_TYPE_4

13:17:43.223 RACH CHANNEL_REQUEST

13:17:43.413 CCCH IMMEDIATE_ASSIGNMENT

13:17:43.533 SDCCH LOCATION_UPDATING_REQUEST

13:17:43.744 DCCH UE_RADIO_ACCESS_CAPABILITY_INFO

13:17:43.744 DCCH INTER_RAT_HANDOVER_INFO

13:17:43.774 SDCCH CLASSMARK_CHANGE

13:17:44.004 SDCCH GPRS_SUSPENSION_REQUEST

13:17:44.475 SDCCH UTRAN_CLASSMARK_CHANGE

13:17:44.915 SDCCH AUTHENTICATION_REQUEST

13:17:45.416 SDCCH AUTHENTICATION_RESPONSE

13:17:45.676 SDCCH CIPHERING_MODE_COMMAND

13:17:45.887 SDCCH CIPHERING_MODE_COMPLETE

13:17:46.087 SDCCH IDENTITY_REQUEST

13:17:46.357 SDCCH IDENTITY_RESPONSE

13:17:47.579 SACCH SYSTEM_INFORMATION_TYPE_5

13:17:47.980 SDCCH LOCATION_UPDATING_ACCEPT

13:17:48.240 SDCCH TMSI_REALLOCATION_COMPLETE

13:17:48.440 SDCCH CHANNEL_RELEASE

………..

13:18:09.220 PACCH PACKET_DOWNLINK_ACK/NACK

13:18:09.300 PACCH PACKET_UPLINK_ASSIGNMENT




13:18:09.621 PACCH PACKET_UPLINK_ACK/NACK

13:18:09.621 PACCH PACKET_CONTROL_ACKNOWLEDGEMENT



13:18:09.881 PTCCH TIMING_ADVANCE_BLOCK

Time 13:17:39.337Cellular System UMTS 2100 FDDService Info Status Service receivedRRC State Cell DCHPacket State PDP ActiveSpreading Factor DL 8Application Throughput Downlink 101173Application Throughput Uplink n/a

Data Transferred Bytes Downlink 202848Data Transfer Host Address ftp.aircom.co.uk

Time 13:18:09.300Cellular System GSM 1800Service Info Status Service receivedPacket State PDP ActiveApplication Throughput Downlink 21928Application Throughput Uplink n/aData Transferred Bytes Downlink 223428Data Transfer Host Address ftp.aircom.co.uk

Cell Reselection to 2g cell

View from statistics from test periodView from statistics from test period Statistics during the testing period as shown below for

GLN0177C1Comparison between RRC Active IU Failures and RAB Active IU Failures with ISHO PS Drops

0

1

2

3

4

5

6

7

Time

Occ

ura

nce

s

RRC_CONN_ACT_FAIL_IU 6 1 1 3 1 0 1 1 1 0 1 3 0 4 0 3 3

RAB_ACT_FAIL_PS_BACKG_IU 6 1 1 3 1 0 1 1 1 0 1 3 0 4 0 3 3

CON_DRPS_IS_HHO_ALL_NRT 6 1 2 3 1 0 1 1 1 1 1 3 0 4 0 3 3

11:30 11:45 12:00 12:15 12:30 12:45 13:00 13:15 13:30 13:45 14:00 14:15 14:30 14:45 15:00 15:15 15:30

ConclusionsConclusions

From the analysis of drive test data, the problem does not seem to be visible to the subscriber.

At the application level, FTP session was not terminated. Hence the user would have only experienced a temporary pause in the transfer and then a slowdown of the throughput rate.

So the possible scenarios that may lead this counter to increment even though no abnormal condition is present:

The old Radio Link times out and the Nobe B sends a radio link failure message to the RNC before the Iu Release Command is received from the CN. With the receipt of the Iu Release Command, the RNC misinterprets the failure.

A timer in the CN expires before the GSM/GPRS network informs the CN that the mobile has successfully connected to the GSM/GPRS network. The CN then sends the Iu Release Command to the RNC with a failure cause that the RNC misinterprets.

Most likely this is a bug with the RNC but if not then the timers involved in the Inter-System HHO to GSM procedure should be checked to see if they should allow more time for the procedure to complete.

RRC Access Radio Failures

SummarySummary

From results of investigations in other networks: Most Active Radio Access failures were caused during the registration and

inter-rat cell reselection procedures

Registration is used for either IMSI attach or GPRS attach, while Inter-rat Cell Reselection is used for 2g to 3g cell reselection.

In Orange network, there is a high correlation between RRC Access Radio (Synchro) Failures and the counters for Registration Failures and Inter-RAT Reselection failures for those cells with high numbers of failures.

The “Registration” and Inter-RAT Reselection procedures were tested in a normal cell to check if the issue was a problem with the counter or the system. Result was that under normal conditions these procedures do not increment the counters.

Evaluation of cells suffering from high failures for high interference or availability problems found no relationship between the failures.

So far results are inconclusive as to where the fault lies – with poor radio conditions or system fault. Iub Trace has been requested on a candidate site with high numbers of failures to further investigate problem.


From the results of investigations in other networks: Most Active Radio Access failures were caused during the

registration and inter-rat cell reselection procedures

Registration is used for either IMSI attach or GPRS attach

Inter-rat Cell Reselection used for 2g to 3g cell reselection

RRC Access Failure for Synch

47%

24%

7%

7%

5%3%2%1%1%1%1%1%0%

registration

inter-rat cell reselection

orig conv.

orig inter

orig. High priority sign.

term low priority sign

term conv

deatch

orig low priority sign.

call re-establishment

orig. Backg

term inter

term backg


Tests were performed to verify which procedures cause an RRC Connection Request to be sent to the RNC with establishment cause “Registration” and if the procedures are inherently causing the RRC Access Radio failure counter to increment. The following procedures were tested:

Home Subscriber attaching to GPRS services. Other national network subscriber attempting to attach to network. Foreign roaming subscriber attempting to attach to network. (This is the

same procedure – Location Update - for a home subscriber at the Uu interface)

Foreign roaming subscriber attempting to attach to GPRS service.

The tests were conducted in a static environment where signal level and quality was good. The objective was to test the actual procedures and not the type of radio environment in which the procedures may usually occur.

While undergoing the tests to identify causes of the Iu failures, many Registrations and Inter-RAT cell reselections were made. The data collected from that test was also analysed to check for RRC access radio failures.

Registration event for GPRS Attach from Orange Registration event for GPRS Attach from Orange SubscriberSubscriber

Messages from test data:

Time: 12:08:39.421

RRC_CONNECTION_REQUEST

establishmentCause: registration

Time: 12:08:40.382

ATTACH REQUEST

M Protocol Discriminator (hex data: 8)

(0x8) Mobility Management message

for GPRS services

M Attach Type (hex data: 1)

Type of attach: GPRS attach

12:08:39.301 BCCH SYSTEM_INFORMATION_BLOCK_TYPE_7


12:08:39.421 CCCH RRC_CONNECTION_REQUEST

12:08:39.922 CCCH RRC_CONNECTION_SETUP


12:08:40.382 DCCH DCCH_RRC_CONNECTION_SETUP_COMPLETE

12:08:40.382 DCCH INITIAL_DIRECT_TRANSFER

12:08:40.382 DCCH ATTACH_REQUEST

12:08:40.482 DCCH MEASUREMENT_REPORT

12:08:40.983 DCCH MEASUREMENT_REPORT

12:08:41.003 DCCH ACTIVE_SET_UPDATE

12:08:41.013 DCCH ACTIVE_SET_UPDATE_COMPLETE

12:08:41.404 DCCH SECURITY_MODE_COMMAND

12:08:41.404 DCCH SECURITY_MODE_COMPLETE

12:08:41.724 DCCH MEASUREMENT_CONTROL

12:08:41.804 DCCH MEASUREMENT_CONTROL

12:08:41.894 DCCH DOWNLINK_DIRECT_TRANSFER

12:08:41.894 DCCH ATTACH_ACCEPT


12:08:42.015 DCCH GMM_INFO

12:08:42.085 DCCH RRC_CONNECTION_RELEASE

12:08:42.085 DCCH RRC_CONNECTION_RELEASE_COMPLETE

12:08:42.085 DCCH RRC_CONNECTION_RELEASE



Registration event for IMSI Attach from other UK Registration event for IMSI Attach from other UK network subscribernetwork subscriber


Time: 13:02:30.372



Time: 13:02:31.494

LOCATION UPDATING REJECT

Reject cause value (11): PCN/PLMN not allowed

13:02:30.202 BCCH "SYSTEM_INFORMATION_BLOCK_TYPE_18"

13:02:30.202 BCCH_BCH "SYSTEM_INFORMATION_BCH"



13:02:30.372 CCCH "RRC_CONNECTION_REQUEST"

13:02:30.783 CCCH "RRC_CONNECTION_SETUP"

13:02:31.063 DCCH "DCCH_RRC_CONNECTION_SETUP_COMPLETE"

13:02:31.063 DCCH "INITIAL_DIRECT_TRANSFER"

13:02:31.063 DCCH "LOCATION_UPDATING_REQUEST"

13:02:31.494 DCCH "DOWNLINK_DIRECT_TRANSFER"

13:02:31.494 DCCH "LOCATION_UPDATING_REJECT"

13:02:31.654 DCCH "RRC_CONNECTION_RELEASE"

13:02:31.654 DCCH "RRC_CONNECTION_RELEASE_COMPLETE"







Time: 13:02:31.654

RRC_CONNECTION_RELEASE

releaseCause: normalEvent

Registration event for IMSI Attach from roaming Registration event for IMSI Attach from roaming subscribersubscriber

Messages from test data:Time: 16:34:38.552







16:34:39.092 DCCH "LOCATION_UPDATING_REQUEST"


16:34:39.483 DCCH "IDENTITY_REQUEST"

16:34:39.493 DCCH "UPLINK_DIRECT_TRANSFER"

16:34:39.493 DCCH "IDENTITY_RESPONSE"


16:34:40.645 DCCH "AUTHENTICATION_REQUEST"


16:34:40.835 DCCH "AUTHENTICATION_RESPONSE"

16:34:41.135 DCCH "SECURITY_MODE_COMMAND"

16:34:41.135 DCCH "SECURITY_MODE_COMPLETE"


16:34:41.466 DCCH "IDENTITY_REQUEST"


16:34:41.466 DCCH "IDENTITY_RESPONSE"


16:34:44.941 DCCH "LOCATION_UPDATING_ACCEPT"


16:34:44.951 DCCH "TMSI_REALLOCATION_COMPLETE"





Location Update to inform CN of MS location. SGSN/MSC

does an IMSI Attach procedure with the VLR and the

Subscriber’s HLR. MS sent TMSI in message

MS is allowed to roam on network and is allocated a new

TMSI

CS-CN Requests UE to Authenticate and start encryption

CS-CN requests the IMSI of MS since TMSI is unknown

Registration event for GPRS Attach from roaming Registration event for GPRS Attach from roaming subscribersubscriber


Time: 16:48:44.270



Time: 16:48:44.921

ATTACH REQUEST



for GPRS services

M Attach Type (hex data: 1)

Type of attach: GPRS attach






16:48:44.921 DCCH "ATTACH_REQUEST"


16:48:45.352 DCCH "GPRS_IDENTITY_REQUEST"


16:48:45.352 DCCH "GPRS_IDENTITY_RESPONSE"


16:48:45.632 DCCH "ATTACH_REJECT"






PS-CN requests MS for IMSI since

ATTACH REQUEST has unknown TMSI

Time: 16:48:45.632

ATTACH REJECT



for GPRS services

M GMM Cause (hex data: 0e)

Cause value (0x0e): GPRS services

not allowed in this PLMN

Statistics recorded during TestsStatistics recorded during Tests

All these procedures cause the registrations counter in M1001 – Service Level – to increment.

If the attach is rejected for any of these procedures, the Registration Failures in M1001 – Service Level – does NOT increment.

No RRC Access failures due to radio was seen during the tests. This proves that under good conditions, the registration procedures are not prone to

cause the counter RRC_CON_ACC_FAIL_RADIO to increment. Some other reason must be the cause…. Bad UE? Bad coverage? System

Malfunction?

Time RegistrationsRegistration

FailsRRC Access Radio Fails Test Case

10:30:00 4 0 010:45:00 12 0 0 IMSI Attach from Home Subscriber11:00:00 11 0 011:15:00 4 0 011:30:00 4 0 011:45:00 12 0 012:00:00 21 0 0 GPRS Attach from Home Subscriber12:15:00 7 0 012:30:00 7 0 012:45:00 1 0 013:00:00 38 0 0 IMSI Attach from other UK network Subscriber13:15:00 2 0 0

…..16:15:00 2 0 016:30:00 4 0 0 IMSI Attach from Foreign Roaming Subscriber16:45:00 10 0 0 GPRS Attach from Foreign Roaming Subscriber17:00:00 0 0 017:15:00 6 0 0

Inter RAT Cell Reselection (2g to 3g)Inter RAT Cell Reselection (2g to 3g)


Time: 13:07:37.101


establishmentCause: interRAT-CellReselection

13:07:36.180 PACCH PACKET_CONTROL_ACKNOWLEDGEMENT



13:07:36.460 PACCH PACKET_UPLINK_ASSIGNMENT




13:07:36.951 BCCH MASTER_INFORMATION_BLOCK

13:07:37.011 BCCH_BCH SYSTEM_INFORMATION_BCH





13:07:37.101 CCCH RRC_CONNECTION_REQUEST


13:07:37.932 DCCH DCCH_RRC_CONNECTION_SETUP_COMPLETE


13:07:37.932 DCCH LOCATION_UPDATING_REQUEST


13:07:37.932 DCCH ROUTING_AREA_UPDATE_REQUEST


13:07:38.603 DCCH AUTHENTICATION_AND_CIPHERING_REQUEST


13:07:38.924 DCCH AUTHENTICATION_REQUEST

continued on next page

GSM

Location Update to inform CS-CN that MS is back on 3g

Routing Area Update to inform PS-CN that MS is back on 3g

PS-CN Requests UE to Authenticate and start encryption

CS-CN requests UE to Authenticate

Inter RAT Cell Reselection (2g to 3g)Inter RAT Cell Reselection (2g to 3g)

Messages from test data (continued):

13:07:39.304 DCCH UPLINK_DIRECT_TRANSFER

13:07:39.304 DCCH AUTHENTICATION_RESPONSE


13:07:39.615 DCCH AUTHENTICATION_AND_CIPHERING_RESPONSE






13:07:40.316 DCCH IDENTITY_REQUEST


13:07:40.316 DCCH IDENTITY_RESPONSE


13:07:40.887 DCCH ROUTING_AREA_UPDATE_ACCEPT


13:07:40.887 DCCH ROUTING_AREA_UPDATE_COMPLETE


13:07:41.207 DCCH GMM_INFO


13:07:41.928 DCCH LOCATION_UPDATING_ACCEPT


13:07:41.928 DCCH TMSI_REALLOCATION_COMPLETE

13:07:42.399 DCCH SIGNALLING_CONNECTION_RELEASE

CS-CN releases signalling link but PS session continues

CS-CN and PS-CN request for UE to restart ciphering

CS-CN requests UE for IMEI

PS-CN gives UE new P-TMSI at this stage

Statistics during drive test periodStatistics during drive test period

In normal conditions, Inter-RAT Cell Reselection and Registrations do not inherently fail or cause the counters to increment. Hence unlikely it is a mistriggering of the counter by the RNC.

In normal conditions, there is a low correlation between the RRC Access failure counters and the Establishment Cause failure counters. This can be seen from the RNC level statistics.

However there seems to be a very close relationship between RCC Access Failures due to Radio with the sum of Registration Failures and Inter-RAT cell reselection failures when a cell is functioning abnormally.

STARTTIME REGISTRATION_ATTS INTR_RAT_CELL_RE_SEL_ATTS REGISTRATION_FAILS INTR_RAT_CELL_RE_SEL_FAILS RRC_CONN_ACC_FAIL_RADIO11:30 4 16 0 0 011:45 4 3 0 0 012:00 21 10 0 0 012:15 15 15 0 0 012:30 21 9 0 0 012:45 11 6 0 0 013:00 5 12 0 0 013:15 15 15 0 0 113:30 8 14 0 0 013:45 7 12 0 0 014:00 9 5 0 0 014:15 28 11 0 0 014:30 20 11 0 0 114:45 29 14 0 0 015:00 20 16 0 1 115:15 16 15 0 0 015:30 5 13 0 0 0

Statistics of 10 Worst Performing Cells (Week 5)Statistics of 10 Worst Performing Cells (Week 5)

Correlation of Worst 10 cells per RNC with respect to RRC Access Radio Failures and Inter-RAT+Registration Failures

0200400600800

1000

gln3207a1

gln0367a1

gln0596c1

gln4013a1

gln0537c1

gln0730b1

gln0494b1

gln0462c1

gln0826c1

gln0537a1

sur0003c1

gln3192c1

gln0677a1

gln0788a1

gln0779a1

gln0881b1

ess0015c1

gln0649b1

gln0484a1

gln0170b1

esx0033c1

gln0580c1

esx0156c1

gln0271b1

gln0525a1

gln0434b1

gln3095c1

hrt0120b1

esx0047a1

gln3109a1

gln0289a1

gln0455b1

gln0322b1

gln0140c1

gln0390b1

gln0055a1

gln0140b1

hrt0283c1

hrt0244c1

oxf0023c1

Cells

INTERRAT_AND_REG_FAIL RRC_CONN_ACC_FAIL_RADIO

gln3

207a

1

gln0

367a

1

gln0

596c1

gln4

013a

1

gln0

537c1

gln0

730b

1

gln0

494b

1

gln0

462c1

gln0

826c1

gln0

537a

1

sur000

3c1

gln3

192c1

gln0

677a

1

gln0

788a

1

gln0

779a

1

gln0

881b

1

ess0015

c1

gln0

649b

1

gln0

484a

1

gln0

170b

1

RRC_CONN_ACC_FAIL_RADIO 143 164 170 170 186 205 213 233 265 353 144 157 163 198 204 257 333 380 559 17608INTERRAT_AND_REG_FAIL 144 172 183 182 186 209 211 230 276 356 152 162 170 206 401 182 413 389 559 17427

esx0033

c1

gln0

580c1

esx0156

c1

gln0

271b

1

gln0

525a

1

gln0

434b

1

gln3

095c1

hrt0120b1

esx0047

a1

gln3

109a

1

gln0

289a

1

gln0

455b

1

gln0

322b

1

gln0

140c1

gln0

390b

1

gln0

055a

1

gln0

140b

1

hrt0283c1

hrt0244c1

oxf0023c1

RRC_CONN_ACC_FAIL_RADIO 88 89 92 103 114 152 191 204 241 1972 154 176 210 276 281 346 349 369 449 473INTERRAT_AND_REG_FAIL 100 90 95 101 116 155 198 205 240 1971 154 175 210 313 132 352 357 369 448 444

Statistics of Network RNCs (Week 5)Statistics of Network RNCs (Week 5)

Correlation per RNC with respect to RRC Access Radio Failures and Inter-RAT+Registration Failures

0

10000

20000

30000

40000

50000

RNC

Fai

lure

s

RRC_CONN_ACC_FAIL_RADIO 8375 104 2323 23117 668 6065 1557 6166 1771

INTERRAT_AND_REG_FAIL 10385 148 39160 24541 807 9794 2820 27001 4990

GLN5000RNC1

GLN5000RNC2

BRK4000RNC1

GLN2000RNC1

GLN2000RNC2

GLN3000RNC1

GLN3000RNC2

GLN1070RNC1

GLN1070RNC2

ConclusionsConclusions

RRC Access Radio Failures were compared with the M1000 counters: Site Availability, PRXNOISE and PRXTOT of the tested cells (5 of them) and no correlation was found between any of the counters.

Not Interference related. Not related to Site Availability.

Are Registrations fails causing the RRC Access failure counter to increment or RRC Access failures causing the Registration failure counter to increment?

Iub trace to be done on candidate site GLN0730 with motivation to conclude if the problem is merely a side effect of poor coverage and/or large spillage, or if it is related with some system fault.

Also a correlation was found on cells having a low RRC Setup Success Rate: many of the Setup failures also occur while doing Inter-RAT reselections and/or registrations.

It might be possible that when an UE fails to register (attach) or complete the inter-RAT cell reselection, it may retry over and over again (all the time incremented the counters) while a user would most likely desist after a few failures.

RRC Iu and Radio Failures

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Transcript of RRC Iu and Radio Failures