CBRA Optimization Guideline July 2019 Introduction CBRA CBRA(Contention Based Random Access) Initiate access, handover and ue initiated ul resync CFRA CFRA(Contention Free Random Access) The CFRA can be used for incoming handover and for PDCCH ordered UL re-synchronization in case of DL data arrival for a UE that is out-of-sync in UL, i.e. a UE whose time alignment timer has expired. RA Senario CBRA CFRA Initial network access Yes Access following a radio link failure Yes Incoming Handover between cells (High Yes Yes Downlink data transfer requiring uplink synchronization Yes Yes Uplink data transfer requiring uplink synchronization Yes Uplink data transfer without dedicated scheduling request resource Yes speed ue: PDCCH order for requesting UE access attempts due to RA failures at their previous access attempts by using CFRA) LTE_CBRA_Success_Rate = 100*(EUtranCellFDD.pmRaSuccCbra/EUtranCellFDD.pmRaAttCbra) LTE_CFRA_Success_Rate = 100*(EUtranCellFDD.pmRaSuccCfra/EUtranCellFDD.pmRaAttCfra) 2019-07-03 | Counter pmRaAttCbra pmRaSuccCbra pmRaAttCfra pmRaSuccCfra pmRaAllocCfra pmRaUnassignedCfraFalse pmRaUnassignedCfraSum pmRaFailCbraMsg2Disc pmRaFailCfraMsg2Disc Description The number of detected CBRA preambles in the cell. The number of successfully detected RA Message 3 for CBRA. The number of detected CFRA preambles in the cell. The number of successfully detected RA Message 3 for CFRA. The number of allocated CFRA preambles in the cell. The number of detected CFRA preambles that are not allocated to any UE. The total number of unassigned CFRA preambles at each PRACH activity. The number of CBRA preambles for which no random access response (RA Msg2) was sent due to expiry of the random access response window. The number of CFRA preambles for which no random access response (RA Msg2) was sent due to expiry of the random access response window. Random Access – Cell Range vs RachRootSequence The value of cellRange decides the preamble format to be used in the random access procedure; — cellRange 15 preamble format 0 — cellRange > 15 preamble format 1 › Cell Range = 15km # of RSI = 10 › Default RSI =384 — By Default, cellRange parameter is fixed to 15 km. — — Other cell ranges than 15 km can be set if the Maximum Cell Range feature is enabled rachRootSequence The first root (Zadoff-Chu) sequence number for Random Access Channel (RACH) preamble generation. It is broadcasted as a part of system information distribution and used for preamble detection The parameter takes the value in the range of 0 to 837 and the default value is 386. It is recommended to set the parameter rachRootSequence to different values in neighboring cells to reduce the probability for false RACH detections – For the particular cell 384,385, …….,394 will be used. › Therefore, neighboring cells RSI should differ by at least 10, resulting a reuse of 838 (0 to 837) / 10 80 “groups” Based on 3GPP 36.211 cellRange Defines the maximum distance from the RBS where a connection to a UE can be setup or maintained, or both For a cellrange of 15 km size, the values of rachRootSequence in adjacent cells must differ by at least 10 between any two neighbors (and at most 827 since there is a wrap-around between the first and last value in the value range) in order to eliminate overlap or collision 2019-07-03 | Random Access - Optimization — Possible reasons for RACH failure: — — — — — — — — Hygiene issue Improper Radio optimization parameter Improper RA preamble planning; Poor RF condition; Sleeping cell; SW Bugs Other reason (e.g. intermittent transport problem) CBRA = NULL — — — — — — Network hygiene is the most important factor for all services, including Random Access. Need to follow up any issue related to Active alarm, VSWR, ASM, TxRank2, UL RSSI etc to TS team. For improper Radio optimization parameter, initial tuning team need to follow standard Layering parameter guideline; For current cell range setting (15km), the parameter rachRootSequence should differ at least 10 between any two neighbors to avoid collision; Check for poor RF conditions. Increase the coverage area by adjusting Tilt/Azimuths of self/neighbor sites and avoid overlapped or overshooting coverage; Upgrade to the newest software patch that available in the network; Sleeping cell is hard to detect. When there are many RA attempt, but none successes (high pmRaFailCbraMsg2Disc), the cell is considered a sleeping one. Try to lock/unlock the cell, or cold restart; Clear issue transport problem for both source/target cells handover that experience bad Random Access 2019-07-03 | Solution CBRA < 20% • • • Availability issue; No contact; Counter not yet activated Sleeping Cells Synchronization issue Sudden degradation of CBRA/CFRA Hygiene issue Improper Radio parameter Improper RA preamble planning Poor RF Condition SW Bugs Other reason • • • Hygiene check Solved No contact issue Counter activation check • • • Lock unlock cells Cold restart Clear synchronization issue. • Hygiene Check and troubleshooting on site if necessary, regarding • ASM • TxRank2 • Active Alarm • VSWR Parameter baseline concheck • Basic parameter concheck • Layering concheck • Eutranrelation concheck Rach Optimization • RachRootSequence • cellRange • preambleInitialReceivedTargetP ower Physical Tuning Upgrade to new SW patch Clear transport problem issue Possible Reason Solutions: — CBRA = 0% “ M Loss of Sync over CPRI Connections Synchronization=1,NodeGrou pSyncMember=1 (clock_synchronisation_problem)” • • • • • Optimization Sample Cases 2019-07-03 | CellRange and RachRootSequence Relation on CBRA Case Background: Sharp raising of pmRaAttCbra was observed in a sudden in cell EJD961B, started from 2018-05-26 21:45:00 But counter pmRaSuccCbra did not show obvious degradation before and after sharp raising of pmRaAttCbra; Analysis prachConfiguration collision was observed, so there might be high risk of false CBRA Msg1 detection among cells, and which might lead to pmRaAttCbra Abnormal Stepping Issue. Way Forward: — — — 2019-07-03 | If pmRaAttCbra Abnormal Stepping Issue was observed with — No obvious abnormal behavior was observed for counter ” pmRaSuccCbra”, ”pmRaAttCfra”, and ”pmRaSuccCfra” — No obvious abnormal behavior was observed for UL interfernce counters — No obvious abnormal behavior was observed for other KPI/PI measurements Please collect cell information with template in previous table within at least 15 km cell range of current cell with issue observed. If PRACH configuration collision was observed, please contact Planning team first for more suggestions CBRA_SR = NULL due to counter not yet activated In XL OSS, CBRA counters are include in USERDEF counter, need to activate below pmJobs/Scanner to measure CBRA : — For BB Site PmJob=USERDEF-L_RADIO_COUNTERS_L17.Cont.Y.STATS — For DUS Site USERDEF-L_RADIO_COUNTERS_L17.Cont.Y.STATS Counter Description pmRaAttCbra The number of detected CBRA preambles in the cell. pmRaSuccCbra The number of successfully detected RA Message 3 for CBRA. CBRA Success Rate 100 90 80 70 60 50 40 30 20 10 0 Counter activation NULL Before – USERDEF scanner not yet defined X3472391G_CO After – USERDEF scanner defined on 27 June 2019 2019-07-03 | time object 6/23/2019 X3472391G_CO 6/24/2019 X3472391G_CO 6/25/2019 X3472391G_CO 6/26/2019 X3472391G_CO 6/27/2019 X3472391G_CO 6/28/2019 X3472391G_CO 6/29/2019 X3472391G_CO 6/30/2019 X3472391G_CO 7/1/2019 X3472391G_CO 7/2/2019 X3472391G_CO 7/3/2019 X3472391G_CO 7/4/2019 X3472391G_CO 7/5/2019 X3472391G_CO 7/6/2019 X3472391G_CO LTE_UL_RSSI_Pwr_dBm NaN NaN NaN NaN -111.15 -111.95 -111.72 -110.71 -111.28 -107.62 -105.78 -105.86 -105.46 -104.81 LTE_pmRaSuccCbra_SR !NULL! !NULL! !NULL! !NULL! 77.40 73.96 76.17 86.07 83.10 73.22 66.11 75.59 73.11 69.95 CBRA SR = 0 – Clock Sync alarm solved after clear NGS issue and cold restart Background: • Found some new L21 sites with Sync Alarm • Impact to CBRA degradation ERBS Layer Alarm (Cause) Alarm Clearance Cold Restart Alarm clearance “ M Loss of Sync over CPRI Connections Synchronization=1,N Sync OK, Cold 4435131E 2100 odeGroupSyncMember=1 restart after TS (clock_synchronisation_problem)” Solution: • Clock Sync Alarm clearance, NGS alarm at 3G node • Cold restart after execution Result: • CBRA Success Rate cells tend to improved 2019-07-03 | CBRA and Antenna System Monitoring (ASM) — — Refer to counter pmBranchDeltaSinrDistr (LTE) Detection Bad ASM indicated from this counter calculation std dev and Avg delta SINR Antenna System Monitoring (ASM) indicates the following problems related to the antenna system: • Mismatched antenna pair Rx diagrams • Swapped or disconnected feeders • Loss in RF path • Missing feeder • SIR/SINR difference indicates potential problem • It is recommended if any ASM issue persist , need to check and troubleshooting on site 1. disconnected 2. RF loss X 3. Mismatched antennas 4. Swapped antennas 2019-07-03 | Low CBRA SR due to ASM with remark “Partial Swap Feeder” Background: • Found ASM Issue “Partial swap feeder” at LTE_DIPONEGORO_JATIMULYA, Impact to CBRA degradation ASM BEFORE ASM AFTER Solution: • Clear ASM and TxRank2 issue by • On site Tshoot • RU-Antenna connection correction Connection Before Connection After Correction 120 100 80 Locked RRU 60 40 20 Result: • CBRA Success Rate cells tend to improved; thus TxRank2 is tend to improved also 2019-07-03 | 0 0 5 10 15 20 1 6 11 16 21 2 7 12 17 22 3 8 13 18 23 4 9 14 19 0 5 10 15 20 1 6 11 16 21 2 7 12 17 22 3 8 13 18 23 4 8/27/2018 8/28/2018 8/29/2018 8/30/2018 8/31/2018 9/1/2018 4451812E - Average of CB Random Access Success Rate 9/2/2018 9/3/2018 9/4/20189/5/2018 4451812E - Average of Txrank2 2019-07-03 | ERBS MC4451487E MC4451487E MC4451487E MC4451487E MC4451487E MC4451487E MC4451487E MC4451487E MC4451487E MC4451487E MC4451487E MC4451487E ASM Before ASM After CBRA Improvement Solution: • Clear ASM issue by • On site Tshoot • RU-Antenna connection correction • Physical or Remote Tilting changes Result: • CBRA Success Rate cells tend to improved date_id 6/9/2019 6/9/2019 6/9/2019 6/9/2019 6/9/2019 6/9/2019 6/16/2019 6/16/2019 6/16/2019 6/16/2019 6/16/2019 6/16/2019 SectorCarrier 1 2 3 4 5 6 1 2 3 4 5 6 Mean0 0.803429 1.248112 0.114598 1.004739 1.475389 4.284947 0.963841 1.672386 1.089405 1.036284 1.250208 0.647968 StD0 7.374661 7.213307 7.517325 6.830422 7.056444 8.450536 6.978253 7.203958 7.83548 6.978314 7.083157 7.209906 Tilting Background: • Found ASM Issue “Mismatch Antenna” Impact to CBRA degradation (2T2R) ASM Low CBRA SR due to ASM “Mismatch Antenna” – 2T2R — CBRA cell_9 improved Remark0 Normal Normal Normal Normal Normal Antenna diagram mismatch Normal Normal Normal Normal Normal Normal CBRA Improvement Solution: • Clear ASM issue by • On site Tshoot • RU-Antenna connection correction • Physical or Remote Tilting changes Result: • CBRA Success Rate cells tend to improved 2019-07-03 | ASM Before ASM After Tilting Background: • Found ASM Issue “Mismatch Antenna” Impact to CBRA degradation (4T4R) ASM Low CBRA SR due to ASM “Mismatch Antenna” – 4T4R — CBRA L2100 improved Low CBRA SR due to RET not calibrate – Overshooting TA Before Background: • Found Overshooting issue and RET not working-well • Thus impact to Overshooting and Low CBRA — — TA After RET need calibration Low TxRank2 CBRA Improvement CBRA SR vs TxRank2 Solution: • Suspect due to mismatch RET configuration/need calibration • On site Tshoot • RET calibration and correction set to Y4 Result: • CBRA Success Rate cells tend to improved 100 90 80 70 60 50 40 30 20 10 0 0 3 6 9 12 15 18 21 0 3 6 9 12 15 18 21 0 3 6 9 12 15 18 21 0 3 6 9 12 15 18 21 0 3 6 9 12 15 18 21 0 3 6 9 3/4/2019 3/5/2019 3/6/2019 JK4G18_441PC371E_24 - Average of CB Random Access Success Rate 2019-07-03 | 3/7/2019 3/8/2019 3/9/2019 JK4G18_441PC371E_24 - Average of tx_rank2 Low CBRA due to Impoper Layering parameter (Network Roll-Out PY2018) Background: • Found new site, on air with low CBRA, while hygiene check already PASS CBRA Success Rate Site On Air concheck L2100 After Inject License 120 100 80 60 Solution: • Layering concheck L2100 • Lock unlock after execution 40 20 0 0 4 8 12 16 20 0 4 8 12 16 20 0 4 8 12 16 20 0 4 8 12 16 20 0 4 8 12 16 20 0 4 Result: • CBRA Success Rate and Accessibility cells tend to improved 9/1/2018 9/2/2018 9/3/2018 JK4G18_441PC175E_14 9/4/2018 9/5/2018 9/6/2018 JK4G18_441PC175E_24 Accessibility Site On Air concheck L2100 After Inject License 105 100 95 90 85 80 0 3 7 1013161922 1 5 8 1114172023 2 6 9 12151821 0 3 7 1013161922 1 5 8 1114172023 2 6 9/1/2018 9/2/2018 9/3/2018 JK4G18_441PC175E_14 2019-07-03 | 9/4/2018 JK4G18_441PC175E_24 9/5/2018 9/6/2018 Low CBRA due to Improper eARFCN (Network Roll-Out PY2018) Background: • Found some new sites ON Air with old eARFCN • Impact to CBRA degradation Solution: • NCCR221_XL_Discrepancy earfcn JABO_Dec2018. Result: • CBRA Success Rate cells tend to improved 2019-07-03 | New sites with old earfcn on air NCCR211 Low CBRA due to Improper Rach Root Sequence (386) (Network Roll-Out PY2018) Background: • Found L21 cell Rach Root Sequence setting = 386 (Default value) • Rach Root Sequence cleanup based on CDR Planning team, to avoid RSN collision. Parameter Description rachRootSequence First root sequence number for RACH preamble generation. RACH root sequence is broadcast as a part of system information distribution and is used for preamble detection. For information on the definition of logical root sequence number, see 3GPP TS 36.211. Taking effect depends on the feature state. Exists for MO classes: EUtranCellFDD.rachRootSequence EUtranCellTDD.rachRootSequence Solution: • NCCR143_XL_Lte_Concheck_rachRootSequence_20190405. Result: • CBRA Success Rate L2100 cells tend to improved 2019-07-03 | CBRA Improvement after RachRootSequence Optimization (XL NQI Project 2017) Background: • The purpose of RACH Root sequence number clean up is as one of consistency check for RSN disc parameter (Part of optimization) • Rach Root Sequence cleanup based on CDR Planning team, to avoid RSN collision. CBRA Success Rate 85 84 83 82 Solution: • NCCR NW_Wide_Rach_Seq_Disc_PARA_20170607 Result: • CBRA Success Rate tend to improved 2019-07-03 | 81 80 79 6/16/2017 6/15/2017 6/14/2017 6/13/2017 6/12/2017 6/11/2017 6/10/2017 6/9/2017 6/8/2017 6/7/2017 6/6/2017 78 6/5/2017 First root sequence number for RACH preamble generation. RACH root sequence is broadcast as a part of system information distribution and is used for preamble detection. For information on the definition of logical root sequence number, see 3GPP TS 36.211. Taking effect depends on the feature state. Exists for MO classes: EUtranCellFDD.rachRootSequence EUtranCellTDD.rachRootSequence 6/4/2017 rachRootSequence 6/3/2017 Description 6/2/2017 Parameter Low CBRA on Radio4443 Connected to DUS/DUW – SW Bugs (XL Orion H2 Program) CBRA Success Rate vs RSSI Background: • Found SW Bugs L18.Q2 and W18.Q2 in site with Radio 4443 that connected to DUS/DUW 120 100 -100 L2100 Mixedmode with Radio4443 SW Upgrade from L18.Q2 to L18.Q4 -102 -104 -106 -108 60 -110 40 -112 -114 20 -116 Solution: • Overall performance (include ASM) improved after SW Update to W18Q4.5-1 (3G) and L18.Q4 (LTE) • Cold Restart after Software upgrade Result: • CBRA Success Rate tend to improved 2019-07-03 | -118 6/19/2019 6/19/2019 18:00 6/20/2019 12:00 6/21/2019 6:00 6/22/2019 6/22/2019 18:00 6/23/2019 12:00 6/24/2019 6:00 6/25/2019 6/25/2019 18:00 6/26/2019 12:00 6/27/2019 6:00 6/28/2019 6/28/2019 18:00 6/29/2019 12:00 6/30/2019 6:00 7/1/2019 7/1/2019 18:00 7/2/2019 12:00 7/3/2019 6:00 7/4/2019 7/4/2019 18:00 7/5/2019 13:00 7/6/2019 7:00 7/7/2019 1:00 7/7/2019 19:00 7/8/2019 13:00 7/9/2019 7:00 7/10/2019 1:00 7/10/2019 19:00 7/13/2019 7/13/2019 18:00 7/14/2019 12:00 7/15/2019 6:00 7/16/2019 7/16/2019 18:00 7/17/2019 12:00 7/18/2019 6:00 7/19/2019 0 Average of LTE_pmRaSuccCbra_SR Average of LTE_UL_RSSI_Pwr_dBm RSSI (dBm) CBRA SR (%) 80 TS - U2100 Config RBB11_1A with UL Attenuation Ext 17 dB and L2100 MIMO Impact to CBRA the following connection is RBB22_1A, if we have to configure it as RBB11_1A on W side , then we should consider 2nd RUS as part of antenna Sample at 3G_CIKUPA TS taken on Thursday, 26 and 31 July 2018 Result : UL RSSI improved with config U2100 RBB11_1A and L2100 MIMO Payload and traffic still under monitoring 2019-07-03 | Set ulAttenuation to -170 for EXT ULRSSI improved ericsson.com
