RRC Iu and Radio Failures

AIRCOM International to Orange RRC Active Active IU Failures And RRC Access Access Radio Rad io Failures

RRC Active IU Failures Failu res

Summary According to network statistics a large percentage of fa ilures 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 HH O 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 i s 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 Flow A large percentage of Failures occurring in the RRC Active phase was being associated with problems with the Iu Interface. 

KPI:

_ CONN _ ACT _ FAIL _ IU § RRC _ CONN _ ACT _ FAIL _ xxxx RRC

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 -

§ CON _ DRPS _ IS _ HHO _ xxxx _ NRT

Analysis Work Flow 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.

Statistics Statistics during a 20 day period as shown below for RNC Enfield Comparison between RRC Active IU Failures and RAB Active IU Failures with I SHO PS Drops 400 350 300 250

s e c n a r u c c O

200 150 100 50 0 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 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

Statistics (Test Candidate) Statistics during a 20 day period as shown below for GLN0177C1 C

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Test Setup From Orange London Drivetest Methodology Document S

1.1.1

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Methodology ll be dependant upon hich tests are bei ng conducted. he follo ing test are %

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Example

Trace (Network View)

NodeB informs RNC of Loss of Sync with MS

PS-CN asks RNC to r elease resources

RNC does not respond in in 3 secs

PS-CN re-asks RNC to r elease resources RNC Releases the IU connection RNC sends Connection Release But MS not on channel any more

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


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

CLASSMAR K _CHANGE

13:17:44.004

SDCCH

GPRS_SUSPENSION_REQUEST

13:17:44.475

SDCCH

UTRAN_CLASSMAR K _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


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

PAC KET_DOWNLINK _ACK/NACK

13:18:09.300

PACCH

PAC KET_UPLINK _ASSIGNMENT

13:18:09.400

PACCH


13:18:09.501

PACCH


13:18:09.581

PACCH


13:18:09.621

PACCH

PAC KET_UPLINK _AC K/NACK

13:18:09.621

PACCH

PAC KET_CONTROL_ACKNOWLEDGEMENT

13:18:09.701

PACCH


13:18:09.821

PACCH


13:18:09.881

PTCCH

TIMING_ADVANCE_BLOC K

«««..

Time 13:17:39.337 Cellular System UMTS 2100 FDD Service Info Status Service received RRC State Cell DCH Packet State PDP Active Spreading Factor DL 8 Application Throughput Downlink 101173 Application Throughput Uplink n/a Data Transferred Bytes Downlink 202848 Data Transfer Host Address ftp.aircom.co.uk

Cell Reselection to 2g cell

Time Cellular System Service Info Status Packet State Application Throughput Downlink Application Throughput Uplink Data Transferred Bytes Downlink Data Transfer Host Address

13:18:09.300 GSM 1800 Service received PDP Active 21928 n/a 223428 ftp.aircom.co.uk

View rom statistics rom test period Statistics during the testing period as shown below for GLN0177C1 Comparison between RRC Active IU Failures and RAB Active IU Failures with I SHO PS Drops 7

6

5

s e c n a r u c c O

4

3

2

1

0

11:30

11:45

12:00

12:15

12:30

12:45

13:00

13:15

13:30

13:45

14:00

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_BAC KG_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

Time

14:15

14:30

14:45

15:00

15:15

15:30

Conclusions 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 i nforms 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

Summary From results of investigations in other networks: 

Most Active Radio Access failures were caused during the regi stration and inter-rat cell reselection procedures

Registration is used for either IMSI attach or GPRS attach, while Interrat 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 ³Registration´ 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.

Analysis Work Flow 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 Fa

re for Sy c 9

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1% 1% 0% 11% % 1% 2% 3% 5%

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Analysis Work Flow Tests were performed to verify which procedures cause an RRC Connection Request to be sent to the RNC with establishment cause ³Registration´ 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 ne twork.





Foreign roaming subscriber attempting to attach to network. (This i s 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 or GPRS Attach rom Orange Subscriber Messages from test data: 12:08:39.301

BCCH

12:08:39.301

BCCH

SYSTEM_INFORMATION_BLOC K _TYPE_7 SYSTEM_INFORMATION_BLOC K _TYPE_18

12:08:39.421

CCCH

RRC_CONNECTION_REQUEST

12:08:39.922

CCCH

RRC_CONNECTION_SETUP

12:08:40.002

CCCH


12:08:40.382

DCCH

DCCH_RRC_CONNECTION_SETUP_COMPLETE

Time: 12:08:39.421

12:08:40.382

DCCH

INITIAL_DIRECT_TRANSFER


12:08:40.382

DCCH

ATTACH_REQUEST

establishmentCause: registration

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

DOWNLIN K _DIRECT_TRANSFER

12:08:41.894

DCCH

ATTACH_ACCEPT

12:08:42.015

DCCH


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


12:08:42.165

DCCH


12:08:42.325

DCCH


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

Registration event or IMSI Attach rom other UK network subscriber Messages from test data: 13:02:30.202

BCCH

"SYSTEM_INFORMATION_BLOC K _TYPE_18"

13:02:30.202

BCCH_BCH

"SYSTEM_INFORMATION_BCH"

Time: 13:02:30.372

13:02:30.222

BCCH_BCH



13:02:30.222

BCCH



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

"DOWNLIN K _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"


13:02:31.824

DCCH


releaseCause: normalEvent

13:02:31.984

DCCH


13:02:32.255

BCCH_BCH


13:02:32.255

BCCH


13:02:32.255

BCCH


13:02:32.255

BCCH


Time: 13:02:31.494 LOCATION UPDATING REJECT Reject cause value (11): PCN/PLMN not allowed

Time: 13:02:31.654

Registration event or IMSI Attach rom roaming subscriber Messages from test data: Time: 16:34:38.552 16:34:38.552

CCCH



16:34:38.822

CCCH



16:34:39.092

DCCH


16:34:39.092

DCCH


16:34:39.092

DCCH

"LOCATION_UPDATING_REQUEST"

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

16:34:39.483

DCCH


does an IMSI Attach procedure with the VLR and the

16:34:39.483

DCCH

"IDENTITY_REQUEST"

16:34:39.493

DCCH

"UPLIN K _DIRECT_TRANSFER"

16:34:39.493

DCCH

"IDENTITY_RESPONSE"

16:34:40.645

DCCH


16:34:40.645

DCCH

"AUTHENTICATION_REQUEST"

16:34:40.835

DCCH


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


16:34:41.466

DCCH

"IDENTITY_REQUEST"

16:34:41.466

DCCH


16:34:41.466

DCCH

"IDENTITY_RESPONSE"

16:34:44.941

DCCH


16:34:44.941

DCCH

"LOCATION_UPDATING_ACCEPT"

16:34:44.951

DCCH


16:34:44.951

DCCH

"TMSI_REALLOCATION_COMPLETE"

16:34:45.331

DCCH


16:34:45.331

DCCH


16:34:45.492

DCCH


16:34:45.652

DCCH


Subscriber¶s HLR. MS sent TMSI in message

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

CS-CN Requests UE to Authenticate and start encryption

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

Registration event or GPRS Attach rom roaming subscriber Messages from test data: Time: 16:48:44.270 RRC_CONNECTION_REQUEST 16:48:44.100

BCCH


16:48:44.270

CCCH


16:48:44.671

CCCH


16:48:44.921

DCCH


16:48:44.921

DCCH


16:48:44.921

DCCH

"ATTACH_REQUEST"

16:48:45.352

DCCH


16:48:45.352

DCCH

"GPRS_IDENTITY_REQUEST"

16:48:45.352

DCCH


16:48:45.352

DCCH

"GPRS_IDENTITY_RESPONSE"

16:48:45.632

DCCH


16:48:45.632

DCCH

"ATTACH_REJECT"

16:48:45.762

DCCH


16:48:45.762

DCCH


16:48:45.912

DCCH


16:48:46.073

DCCH


16:48:46.353

BCCH_BCH



Time: 16:48:44.921 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

PS-CN requests MS for IMSI since ATTACH REQUEST has unknown TMSI Time: 16:48:45.632 ATTACH REJECT M Protocol Discriminator (hex data: 8) (0x8) Mobility Management message for GPRS services M GMM Cause (hex data: 0e) Cause value (0x0e): GPRS services not allowed in this PLMN

Inter RAT Cell Reselection (2g to 3g) Messages from test data: 13:07:36.180

PACCH

PAC KET_CONTROL_ACKNOWLEDGEMENT

13:07:36.360

PACCH


13:07:36.390

PACCH


13:07:36.460

PACCH

PAC KET_UPLINK _ASSIGNMENT

13:07:36.500

PACCH


13:07:36.621

PACCH


13:07:36.741

PACCH


13:07:36.951

BCCH

MASTER_INFORMATION_BLOC K

13:07:37.011

BCCH_BCH

SYSTEM_INFORMATION_BCH

13:07:37.011

BCCH

SYSTEM_INFORMATION_BLOC K _TYPE_1

13:07:37.011

BCCH


13:07:37.011

BCCH


13:07:37.011

BCCH


13:07:37.101

CCCH


13:07:37.592

CCCH


13:07:37.932

DCCH

DCCH_RRC_CONNECTION_SETUP_COMPLETE

13:07:37.932

DCCH


13:07:37.932

DCCH

LOCATION_UPDATING_REQUEST

13:07:37.932

DCCH


13:07:37.932

DCCH

ROUTING_AREA_UPDATE_REQUEST

13:07:38.603

DCCH


13:07:38.603

DCCH

AUTHENTICATION_AND_CIPHERING_REQUEST

13:07:38.924

DCCH


13:07:38.924

DCCH

AUTHENTICATION_REQUEST

continued on next page

GSM

Time: 13:07:37.101 RRC_CONNECTION_REQUEST establishmentCause: interRAT-CellReselection

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) Messages from test data (continued): 13:07:39.304

DCCH

UPLIN K _DIRECT_TRANSFER

13:07:39.304

DCCH

AUTHENTICATION_RESPONSE

13:07:39.615

DCCH


13:07:39.615

DCCH

AUTHENTICATION_AND_CIPHERING_RESPONSE

13:07:39.615

DCCH


13:07:39.615

DCCH


13:07:39.965

DCCH


13:07:39.965

DCCH


13:07:40.316

DCCH


13:07:40.316

DCCH

IDENTITY_REQUEST

13:07:40.316

DCCH


13:07:40.316

DCCH

IDENTITY_RESPONSE

13:07:40.887

DCCH


13:07:40.887

DCCH

ROUTING_AREA_UPDATE_ACCEPT

13:07:40.887

DCCH


13:07:40.887

DCCH

ROUTING_AREA_UPDATE_COMPLETE

13:07:41.207

DCCH


13:07:41.207

DCCH

GMM_INFO

13:07:41.928

DCCH


13:07:41.928

DCCH

LOCATION_UPDATING_ACCEPT

13:07:41.928

DCCH


13:07:41.928

DCCH

TMSI_REALLOCATION_COMPLETE

13:07:42.399

DCCH

SIGNALLING_CONNECTION_RELEASE

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

CS-CN releases signalling link but PS session continues

Statistics during drive test period STARTTIME REGISTRATI N_ATTS R

INTR_RAT_CELL_RE_SEL_ATTS

REGISTRATI N_FAILS R

INTR_RAT_CELL_RE_SEL_FAILS

RRC_C NN_ACC_FAIL_RADI R

R

W

S

S

T

U

V

S

W

X

V

V

V

W

Y

S

S

T

U

V

V

S

`

T

V

V

`

S

S

V

V

V

V

S

`

T

S

Y

S

Y

S

Y

V

V

V

S

`

T

U

V

`

S

S

`

T

S

U

T

V

V

S

U

T

S

Y

S

U

T

U

V

U

T

a

V

V

V

V

V

W

Y

S

S

X

Y

S

V

S

Y

V

`

S

V

V

Y

V

V

V

S

W

b

S

V

V

V

W

S

Y

c

S

`

V

V

V

V

V

V

W

S

T

V

V

a

Y

T

S

Y

`

b

S

S

V

V

V

T

U

V

`

V

S

S

V

V

S

W

S

W

S

W

W

S

W

T

Y

`

a

S

V

V

V

S

Y

T

V

V

`

V

S

X

V

S

S

S

Y

T

S

Y

S

X

S

Y

V

V

V

S

Y

T

U

V

Y

S

U

V

V

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.

V

gln0170b1

8 7 0 2 6 4 7 7 1 1

gln0484a1

9 9 5 5 5 5

gln0649b1

0 9 8 8 3 3

ess0015c1

3 3 3 1 3 4

gln0881b1

7 2 5 8 2 1

gln0779a1

4 1 0 0 2 4

gln0788a1

8 6 9 0 1 2

gln0677a1

3 0 6 7 1 1

gln3192c1

7 2 5 6 1 1

sur0003c1

4 2 4 5 1 1

gln0537a1

3 6 5 5 3 3

gln0826c1

5 6 6 7 2 2

1 0 4 4 esx0047a1 2 2

gln0462c1

3 0 3 3 2 2

hrt0120b1

4 5 0 0 2 2

gln0494b1

3 1 1 1 2 2

gln3095c1

1 8 9 9 1 1

gln0730b1

5 9 0 0 2 2

gln0434b1

2 5 5 5 1 1

oxf0023c1 hrt0244c1

) 5 k e e W ( s l l e C g n i m r o r e P t s r o W

hrt0283c1 gln0140b1 gln0055a1 gln0390b1 gln0140c1 gln0322b1 s e r l i a

gln0455b1

q

gln0289a1

p

n o i t a r t s i g e R + T h

R

r e t n r

n a s e r l i a i

q

p

o i a i

gln3109a1 O I D A R _ L I A F _ C C A _ N N O C _ C R R

R

s s e c c

h

C R R

o t t c e e

esx0047a1 hrt0120b1 gln3095c1 gln0434b1 gln0525a1 gln0271b1 esx0156c1 gln0580c1 esx0033c1

L I A F _ G E R _ D N A

gln0170b1

s l l e C

gln0484a1 gln0649b1 ess0015c1

oxf0023c1

3 4 7 4 4 4

hrt0244c1

9 8 4 4 4 4

hrt0283c1

9 9 6 6 3 3

gln0140b1

9 7 4 5 3 3

gln0055a1

6 2 4 5 3 3

gln0390b1

1 2 8 3 2 1

gln0140c1

6 3 7 1 2 3

gln0322b1

0 0 1 1 2 2

gln0455b1

6 5 7 7 1 1

gln0289a1

4 4 5 5 1 1

gln3109a1

2 1 7 7 9 9 1 1

Statistics o Network RNCs (Week 5) Corre atio

er RNC wit res ect to RRC ccess Ra io Fai res a R +Re istratio Fai res

ter

50000 40000 s e r

30000

t

i a s

F

20000 10000 0

RRC_CONN_ ACC_F A _R A INTERR A T_ AND_RE _F AIL

O

GLN500 GLN500 BRK400 GLN200 GLN200 GLN300 GLN300 GLN107 GLN107 0RNC1 0RNC2 0RNC1 0RNC1 0RNC2 0RNC1 0RNC2 0RNC1 0RNC2 8375

104

2323

23117

668

6065

1557

6166

1771

10385

148

39160

24541

807

9794

2820

27001

4990

RNC

Conclusions 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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