rrc iu and radio failures
Post on 02-Dec-2014
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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 _____
Analysis Work FlowAnalysis 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.
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
PDP Context Activation
500 byte ping
FTP Login
500kB FTP download
FTP Log off
PDP Context Deactivation
GPRS Detach
Data 3 (LF)
GPRS Attach
PDP Context Activation
500 byte ping
FTP Login
1MB FTP download
FTP Log off
PDP Context Deactivation
GPRS Detach
Data 4 (SF)
GPRS Attach
PDP Context Activation
500 byte ping
FTP Login
100kB FTP upload
FTP Log off
PDP Context Deactivation
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
13:18:09.400 PACCH PACKET_DOWNLINK_ACK/NACK
13:18:09.501 PACCH PACKET_DOWNLINK_ACK/NACK
13:18:09.581 PACCH PACKET_DOWNLINK_ACK/NACK
13:18:09.621 PACCH PACKET_UPLINK_ACK/NACK
13:18:09.621 PACCH PACKET_CONTROL_ACKNOWLEDGEMENT
13:18:09.701 PACCH PACKET_DOWNLINK_ACK/NACK
13:18:09.821 PACCH PACKET_DOWNLINK_ACK/NACK
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.
Analysis Work FlowAnalysis 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 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
Analysis Work FlowAnalysis Work Flow
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
12:08:39.301 BCCH SYSTEM_INFORMATION_BLOCK_TYPE_18
12:08:39.421 CCCH RRC_CONNECTION_REQUEST
12:08:39.922 CCCH RRC_CONNECTION_SETUP
12:08:40.002 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 DOWNLINK_DIRECT_TRANSFER
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
12:08:42.165 DCCH RRC_CONNECTION_RELEASE_COMPLETE
12:08:42.325 DCCH RRC_CONNECTION_RELEASE_COMPLETE
Registration event for IMSI Attach from other UK Registration event for IMSI Attach from other UK network subscribernetwork subscriber
Messages from test data:
Time: 13:02:30.372
RRC_CONNECTION_REQUEST
establishmentCause: registration
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"
13:02:30.222 BCCH_BCH "SYSTEM_INFORMATION_BCH"
13:02:30.222 BCCH "SYSTEM_INFORMATION_BLOCK_TYPE_11"
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"
13:02:31.824 DCCH "RRC_CONNECTION_RELEASE_COMPLETE"
13:02:31.984 DCCH "RRC_CONNECTION_RELEASE_COMPLETE"
13:02:32.255 BCCH_BCH "SYSTEM_INFORMATION_BCH"
13:02:32.255 BCCH "SYSTEM_INFORMATION_BLOCK_TYPE_2"
13:02:32.255 BCCH "SYSTEM_INFORMATION_BLOCK_TYPE_7"
13:02:32.255 BCCH "SYSTEM_INFORMATION_BLOCK_TYPE_18"
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
RRC_CONNECTION_REQUEST
establishmentCause: registration
16:34:38.552 CCCH "RRC_CONNECTION_REQUEST"
16:34:38.822 CCCH "RRC_CONNECTION_SETUP"
16:34:39.092 DCCH "DCCH_RRC_CONNECTION_SETUP_COMPLETE"
16:34:39.092 DCCH "INITIAL_DIRECT_TRANSFER"
16:34:39.092 DCCH "LOCATION_UPDATING_REQUEST"
16:34:39.483 DCCH "DOWNLINK_DIRECT_TRANSFER"
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 "DOWNLINK_DIRECT_TRANSFER"
16:34:40.645 DCCH "AUTHENTICATION_REQUEST"
16:34:40.835 DCCH "UPLINK_DIRECT_TRANSFER"
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 "DOWNLINK_DIRECT_TRANSFER"
16:34:41.466 DCCH "IDENTITY_REQUEST"
16:34:41.466 DCCH "UPLINK_DIRECT_TRANSFER"
16:34:41.466 DCCH "IDENTITY_RESPONSE"
16:34:44.941 DCCH "DOWNLINK_DIRECT_TRANSFER"
16:34:44.941 DCCH "LOCATION_UPDATING_ACCEPT"
16:34:44.951 DCCH "UPLINK_DIRECT_TRANSFER"
16:34:44.951 DCCH "TMSI_REALLOCATION_COMPLETE"
16:34:45.331 DCCH "RRC_CONNECTION_RELEASE"
16:34:45.331 DCCH "RRC_CONNECTION_RELEASE_COMPLETE"
16:34:45.492 DCCH "RRC_CONNECTION_RELEASE_COMPLETE"
16:34:45.652 DCCH "RRC_CONNECTION_RELEASE_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
Messages from test data:
Time: 16:48:44.270
RRC_CONNECTION_REQUEST
establishmentCause: registration
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
16:48:44.100 BCCH "SYSTEM_INFORMATION_BLOCK_TYPE_18"
16:48:44.270 CCCH "RRC_CONNECTION_REQUEST"
16:48:44.671 CCCH "RRC_CONNECTION_SETUP"
16:48:44.921 DCCH "DCCH_RRC_CONNECTION_SETUP_COMPLETE"
16:48:44.921 DCCH "INITIAL_DIRECT_TRANSFER"
16:48:44.921 DCCH "ATTACH_REQUEST"
16:48:45.352 DCCH "DOWNLINK_DIRECT_TRANSFER"
16:48:45.352 DCCH "GPRS_IDENTITY_REQUEST"
16:48:45.352 DCCH "UPLINK_DIRECT_TRANSFER"
16:48:45.352 DCCH "GPRS_IDENTITY_RESPONSE"
16:48:45.632 DCCH "DOWNLINK_DIRECT_TRANSFER"
16:48:45.632 DCCH "ATTACH_REJECT"
16:48:45.762 DCCH "RRC_CONNECTION_RELEASE"
16:48:45.762 DCCH "RRC_CONNECTION_RELEASE_COMPLETE"
16:48:45.912 DCCH "RRC_CONNECTION_RELEASE_COMPLETE"
16:48:46.073 DCCH "RRC_CONNECTION_RELEASE_COMPLETE"
16:48:46.353 BCCH_BCH "SYSTEM_INFORMATION_BCH"
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
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)
Messages from test data:
Time: 13:07:37.101
RRC_CONNECTION_REQUEST
establishmentCause: interRAT-CellReselection
13:07:36.180 PACCH PACKET_CONTROL_ACKNOWLEDGEMENT
13:07:36.360 PACCH PACKET_DOWNLINK_ACK/NACK
13:07:36.390 PACCH PACKET_DOWNLINK_ACK/NACK
13:07:36.460 PACCH PACKET_UPLINK_ASSIGNMENT
13:07:36.500 PACCH PACKET_DOWNLINK_ACK/NACK
13:07:36.621 PACCH PACKET_DOWNLINK_ACK/NACK
13:07:36.741 PACCH PACKET_DOWNLINK_ACK/NACK
13:07:36.951 BCCH MASTER_INFORMATION_BLOCK
13:07:37.011 BCCH_BCH SYSTEM_INFORMATION_BCH
13:07:37.011 BCCH SYSTEM_INFORMATION_BLOCK_TYPE_1
13:07:37.011 BCCH SYSTEM_INFORMATION_BLOCK_TYPE_2
13:07:37.011 BCCH SYSTEM_INFORMATION_BLOCK_TYPE_7
13:07:37.011 BCCH SYSTEM_INFORMATION_BLOCK_TYPE_18
13:07:37.101 CCCH RRC_CONNECTION_REQUEST
13:07:37.592 CCCH RRC_CONNECTION_SETUP
13:07:37.932 DCCH DCCH_RRC_CONNECTION_SETUP_COMPLETE
13:07:37.932 DCCH INITIAL_DIRECT_TRANSFER
13:07:37.932 DCCH LOCATION_UPDATING_REQUEST
13:07:37.932 DCCH INITIAL_DIRECT_TRANSFER
13:07:37.932 DCCH ROUTING_AREA_UPDATE_REQUEST
13:07:38.603 DCCH DOWNLINK_DIRECT_TRANSFER
13:07:38.603 DCCH AUTHENTICATION_AND_CIPHERING_REQUEST
13:07:38.924 DCCH DOWNLINK_DIRECT_TRANSFER
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 UPLINK_DIRECT_TRANSFER
13:07:39.615 DCCH AUTHENTICATION_AND_CIPHERING_RESPONSE
13:07:39.615 DCCH SECURITY_MODE_COMMAND
13:07:39.615 DCCH SECURITY_MODE_COMPLETE
13:07:39.965 DCCH SECURITY_MODE_COMMAND
13:07:39.965 DCCH SECURITY_MODE_COMPLETE
13:07:40.316 DCCH DOWNLINK_DIRECT_TRANSFER
13:07:40.316 DCCH IDENTITY_REQUEST
13:07:40.316 DCCH UPLINK_DIRECT_TRANSFER
13:07:40.316 DCCH IDENTITY_RESPONSE
13:07:40.887 DCCH DOWNLINK_DIRECT_TRANSFER
13:07:40.887 DCCH ROUTING_AREA_UPDATE_ACCEPT
13:07:40.887 DCCH UPLINK_DIRECT_TRANSFER
13:07:40.887 DCCH ROUTING_AREA_UPDATE_COMPLETE
13:07:41.207 DCCH DOWNLINK_DIRECT_TRANSFER
13:07:41.207 DCCH GMM_INFO
13:07:41.928 DCCH DOWNLINK_DIRECT_TRANSFER
13:07:41.928 DCCH LOCATION_UPDATING_ACCEPT
13:07:41.928 DCCH UPLINK_DIRECT_TRANSFER
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.
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