LTE- ACCESSIBILITY 1 (15) Prepared (Subject resp) No. Deepak Gupta Approved (Document resp) Checked Date Rev Reference 2017-02-28 LTE - ACCESSIBLITY OPTIMIZATION we have only 3 phases of Accessibility. Deepak Gupta Approved (Document resp) Checked Date Rev Reference 2017-02-28 The Different Phases of Accessibility Accessibility for the EUTRAN is a measure of the ability of a user to obtain an E-RAB from the system. note that Phase 1) Random Access & 2) Paging will have effect on end user experience but are not directly reflected in Counter based KPI formula. Considering counter based Accessibility KPI. which are mentioned as below. Note: Pls. LTE. The initial E- RAB establishment process can be divided into the following phases: • Random Access • Paging • RRC Connection Establishment • S1 Signalling Connection Establishment • Initial E-RAB Establishment or E-RAB Addition.ACCESSIBILITY 2 (15) Prepared (Subject resp) No. CSSR Formula:- . These two counters can be used to identify if the noise floor of the cell is higher than it should be. Due to their nature Sleeping Cells are difficult to detect and therefore cells in these conditions can remain out of service for long time periods causing major service outages. Due to UL RSSI. RBS cannot detect/decode the request sent by UE. UL RSSI has a great impact on Accessibility performance. .Interference due to power supply sources.g. External. then the cell is considered a sleeping cell Resolution: Lock/Unlock the cell. And so. ii) Uplink Interference:- UL Interference can be either Internal . ‘pmRadioRecInterferencePwr’ is the measured Noise and Interference power on PUSCH & ‘pmRadioRecInterferencePwrPucch’ is the measured Noise and Interference Power on PUCCH. pmRaSuccCbra CFRA (Contention Free Random Access): pmRaAttCfra. Re-Start. to know the actual noise floor of the cell and perform further investigation to find the root cause for the same. Deepak Gupta Approved (Document resp) Checked Date Rev Reference 2017-02-28 1) Random Access:- The UE uses the random access process to gain access to the cell for the following reasons: Initial access to the network from the idle state – RRC Connection Establishment Re-gain access to the network after radio link failure – RRC Connection Re-establishment During handover to gain synchronization with a new cell – Handover Execution Two types of RA procedures are defined: CBRA (Contention Based Random Access): pmRaAttCbra. LTE. hardware or software alarms The Counter pmRaSuccCbra is very low or zero.Interference due to other UE’s in the cell. pmRaSuccCfra Troubleshooting: i) Sleeping Cells:- Check whether the cell is a “Sleeping Cell”. They do not report standard symptoms of failures in services e.ACCESSIBILITY 3 (15) Prepared (Subject resp) No. Ideally this counter should be measured at the lowest traffic hours (early morning hours for most). so that the RACH preamble signal can rise above the noise floor. RachRootSequence to be tuned accordingly to accommodate 64 preambles.-117)powers if the noise floor is very high during the high traffic hours(internal interference). RSI should be tuned considering the Cell Range.txt 2) RRC Connection Establishment:- • The RRC connection request message is sent to the eNodeB after the UE has performed initial cell selection and detected the best cell . we cannot increase the RACH capacity. L1 Control Description. prachconfigurationindex can be tuned to increase the capacity of cell from RACH perspective. RootSequenceIndex(RachRootSequence) Conflict: RSI hits nearby can lead to conflicts in preambles detection in the concerned cells. Deepak Gupta Approved (Document resp) Checked Date Rev Reference 2017-02-28 Resolution: Checking Alarms & HW faults in case of high RSSI in low traffic hours(external interference). MTD Signal Traces: UPC_DL_MAC_CE_FI_SCHEDULE_RA_MSG2_REQ : Used to request creation of one RA Msg2 session to be scheduled for a subframe. LTE. Preambles discarded for TA > CellRange: Counter for this is only available for CFRA. preambleInitialReceivedTargetPower can be tuned to higher values.ACCESSIBILITY 4 (15) Prepared (Subject resp) No. however it can be used to have an idea of the performance of CBRA.-103) & “pzeronominalpucch” (-120. and the respective difference should be maintained in the potential interfering cells. RAR Information) RACH_All_Traces. but in future versions. iii) Preamble Issues: High traffic on a cell can lead to conflicts between UEs and will impact the average call-setup time and user perception. In the current versions for Ericsson system. auditing “pzeronominalpusch” ( -65. Counter "pmRaFailCfraMsg1DiscOoc” can be used to find the amount of discards because of TA > Cell-Range. Activating feature “MaximumCellRange” and increasing “CellRange” parameter. if the source of high RSSI is unknown. UPC_DL_MAC_CE_FI_SCHEDULE_RA_MSG2_CFM: Confirmation of above UP_DLMACPE_CI_RA_MSG2_ALLOC_IND: Allocation information for messages on the common channel (TB description. weak coverage and the UE does not use the maximum transmit power. Deepak Gupta Approved (Document resp) Checked Date Rev Reference 2017-02-28 • The RRC connection establishment is always initiated by the UE but can be triggered by either the UE (Mobile Originated) or the network (Mobile Terminated). (Comments) Change EutranCellFDD. eNodeB is allowed to accept maximum number of UEs(limited by DUL/eNB version). Counters “pmRrcConnEstabFailHighLoad” & “pmRrcConnEstabFailOverload” will be stepped at transmission of “RRC Connection Reject” during high load or overload circumstances. iii) RF Issues:- Radio i include radio interference. ii) Access fail due to license Issue:- The number of failed-RRC-Connection-Establishments that are rejected due to lack of CUL (Connected User License) are counted with the pmRrcConnEstabFailLic. This can be found out using pmLicConnectedUsersMax and the new license limit should be adjusted accordingly. . imbalance between the uplink (UL) and downlink (DL) quality. there will be no cause value signaled to the UE with RRC Connection Rejects. The network triggers the RRC connection establishment procedure by paging the UE.ACCESSIBILITY 5 (15) Prepared (Subject resp) No. the eNodeB has not received any RRC connection setup complete messages within the related timeout duration. and during the duration when grace period is active. Resolution:- pmRrcConnEstabFailLic pegs only when the grace period(gracePeriodAvailable) has ended. RRC Setup Failure [%] = 100*(pmRrcConnEstabAtt-pmRrcConnEstabSucc) / (pmRrcConnEstabAtt) Troubleshooting i) Access fail due to overloading & High Loading :- The eNodeB may block the UE’s connection request by sending the “RRC Connection Reject”. if the coverage is not an issue. Change EutranFreqRelation. LTE. Resolution:- Change SC 556(numInitialAccessAndIncomingHo): Increase the maximum number of initial accesses and incoming handovers that are allowed during a time window without triggering the load control mechanism. During an RRC connection setup process.qRxLevMin to higher values.qOffsetCellEUtran: enable faster cell re-selection from loaded cells towards other surrounding cells that satisfy the cell selection criteria. iv) CCE Capacity:- . if the coverage is not an issue.qOffsetCellEUtran: enable faster cell re-selection towards better cells. pmRadioTxRankDistr.ACCESSIBILITY 6 (15) Prepared (Subject resp) No. To be investigated: Radio Interference: DL interference from neighboring cells. eg: PUCCH received power should be around the pZeroNorminalPucchPwr (default:-117 dBm) Cell coverage issues can be detected using “pmRadioTbsPwrRestricted” & “pmbadcovevalreport”. Resolution:- Tuning pZeroNorminalPucchPwr depending on the values from pmRadioRecInterferencePwrPucch Tuning t300 in cases where. pmRadioRecInterferencePwrPucch. LTE. Change EutranCellFDD.qRxLevMin to higher values. and UL interference need to be investigated. both the RRC connection setup success rate and the E-RAB setup Success rate are low. pmSinrPuschDistr. UEs trying to access the network in poor Downlink RF conditions can be determined by looking for high pegs in “pmRrcConnEstabAttReatt”. DL interference from external systems. pmRadioUeRepCqiDistr. Deepak Gupta Approved (Document resp) Checked Date Rev Reference 2017-02-28 At the eNodeB side. the radio conditions can be improved much and immediate results are required in the success rate. The counters that can be used to find out the same are: pmSinrPucchDistr. Change EutranFreqRelation. (pdcchLoadTarget) L3 Traces: te e all Ft_RRC_CONN_SETUP: Will printout out L3 messages related to the RRC Setup as well as internal information of the triggered procedures and detailed info on failure cases CTR Trace: INTERNAL_PROC_RRC_CONN_SETUP: Generated for the RRC Connection Setup procedure to establish an RRC Connection. LTE. 3) S1 Connection Establishment. then surely problem is due to lack of CCE resources. The RBS will send this message to the MME in the S1AP ‘INITIAL UE MESSAGE’ and increment the ‘pmS1SigConnEstabAtt’ counter as illustrated below.ACCESSIBILITY 7 (15) Prepared (Subject resp) No. Contains information about the request and result. If the last bucket has high number of samples in the degraded hours. • When setting up the E-RAB the ‘RRC CONNECTION SETUP COMPLETE’ message contains a piggybacked NAS ‘Attach Request’ message. max=3) can get best utilization of the CCE resources with required control dimensioning. . Resolution:- Tuning pdcchCfiMode to the optimum value of 5(dynamic. Deepak Gupta Approved (Document resp) Checked Date Rev Reference 2017-02-28 pmPdcchCceUtil will give idea if high CCE utilization led to degradation in RRC Success Rate. the load will be on the other MME’s in the pool. whether all are up and running. . Using “st termpointtomme” status of connected MME can be checked. as if one is inactive. LTE. Deepak Gupta Approved (Document resp) Checked Date Rev Reference 2017-02-28 Counters:- pmS1SigConnEstabAtt pmS1SigConnEstabSucc Troubleshooting MME overload can lead to s1 connection failures and this can be found using the pmS1SigConnEstabFailMmeOvlMos counter. Investigation from MME end would be required in this case.ACCESSIBILITY 8 (15) Prepared (Subject resp) No. Resolution:- Restarting the node. an incorrect PLMN id is defined (ENodeBFunction and EUtranCellFDD MOs). if yes.ACCESSIBILITY 9 (15) Prepared (Subject resp) No. Deepak Gupta Approved (Document resp) Checked Date Rev Reference 2017-02-28 Find out if the degradation is from a certain hour. This message includes information regarding the default E-RAB to set up . Locking and unlocking the termpointtomme with the problematic MME. Eg: Enabling and decoding the S1AP_ASN traces will show us the cause of an S1 Setup failure. TE Trace: te e all Ft_S1AP_ASN: Will printout out messages related to the S1AP Setup as well as internal information of the triggered procedures and detailed info on failure cases. Contains information about the request and result. CTR trace: INTERNAL_PROC_S1_SIG_CONN_SETUP: Generated for the S1 Signaling Connection Setup procedure to establish an S1 Signaling Connection. 4) E-RAB Establishment:- A. Initial E-RAB Establishment • The Initial Context Setup procedure is triggered by the MME by sending the INITIAL CONTEXT SETUP REQUEST. LTE. Locking and Unlocking the cell. In the below case. try to find out if any restarts or any alarms on the node are evident from the logs. The eNodeB configures the UE by sending message RRC CONNECTION RECONFIGURATION • The UE responds with RRC CONNECTION RECONFIGURATION COMPLETE and the procedure is completed after the eNodeB has sent INITIAL CONTEXT SETUP RESPONSE to the MME.ACCESSIBILITY 10 (15) Prepared (Subject resp) No. Counters:- pmErabEstabAttAdded pmErabEstabSuccAdded . Added E-RAB Establishment • The added bearer is established if the user requires different QoS of that offered by the initial bearer. Counters: pmErabEstabAttInit pmErabEstabSuccInit B. Deepak Gupta Approved (Document resp) Checked Date Rev Reference 2017-02-28 • The eNodeB allocates resources for the first Data Radio Bearer (DRB). or if the user requires connectivity to different PDN. Added bearers are configured to run in parallel to the existing initial bearer • The added bearer establishment procedure is initiated by the network but may be requested by the UE • The eNodeB uses the E-RAB Setup Request to configure itself for the added bearer. LTE. The RRC Connection Reconfiguration message provides the UE with information necessary to configure the added bearer. LTE. Check if they are set to default values. Deepak Gupta Approved (Document resp) Checked Date Rev Reference 2017-02-28 i) License for no. zzzTemp20 / zzzTemp21 are the parameters used to configure Uplink and Downlink admission thresholds respectively. Also an audit of various Admission Control parameters can be carried out .ACCESSIBILITY 11 (15) Prepared (Subject resp) No. ii) UL /DL GBR resources overload:- pmErabEstabFailGbrDlEnb & pmErabEstabFailGbrUlEnb gives the total number of failed initial E-RAB setup attempts due to downlink/Uplink GBR overload for transport network resources. of ERAB's per user:- pmErabEstabFailInitLic/pmErabEstabFailAddedLic Gives the total number of license rejects depending on the configuration on the eNodeB like “Multiple Radio Bearer per user”. else tuning will be required depending on the capacity and requirement. DL interference from external systems. pmRadioRecInterferencePwrPucch. and UL interference need to be investigated. replacing the RRU is the option. Deepak Gupta Approved (Document resp) Checked Date Rev Reference 2017-02-28 iii) eNodeB Issue With regards to hanging resources in eNb – a restart normally helps. pmRadioUeRepCqiDistr. To find out particular UE issue. both the RRC connection setup success rate and the E-RAB setup Success rate are low. At the eNodeB side. UEs trying to access the network in poor Downlink RF conditions can be determined by looking for high pegs in “pmRrcConnEstabAttReatt”. With regards to faulty RRU’s – if restarting the RRU doesn’t help. To be investigated: Radio Interference: DL interference from neighboring cells. During an RRC connection setup process. imbalance between the uplink (UL) and downlink (DL) quality.ACCESSIBILITY 12 (15) Prepared (Subject resp) No. pmSinrPuschDistr. LTE. eg: PUCCH received power should be around the pZeroNorminalPucchPwr (default:-117 dBm) Cell coverage issues can be detected using “pmRadioTbsPwrRestricted” & “pmbadcovevalreport”. pmRadioTxRankDistr. iv) RF Issues:- Radio issues include radio interference. the eNodeB has not received any RRC connection setup complete messages within the related timeout duration. The counters that can be used to find out the same are: pmSinrPucchDistr. weak coverage and the UE does not use the maximum transmit power. We need to analyze CTR (Cell Traces) & EBM (MME). . qOffsetCellEUtran: enable faster cell re-selection towards better cells. Deepak Gupta Approved (Document resp) Checked Date Rev Reference 2017-02-28 Resolution:- Tuning pZeroNorminalPucchPwr depending on the values from pmRadioRecInterferencePwrPucch Tuning t300 in cases where. Contains information about the request and result. max=3) can get best utilization of the CCE resources with required control dimensioning. CTR Trace: INTERNAL_PROC_ERAB_SETUP: Generated for the ERAB setup procedure to establish additional ERABs. . v) CCE Capacity:- pmPdcchCceUtil will give idea if high CCE utilization led to degradation in RRC Success Rate. the radio conditions can be improved much and immediate results are required in the success rate.Will printout out L3 messages related to the ERAB setup as well as internal information of the triggered procedures and detailed info on failure cases. then surely problem is due to lack of CCE resources. Change EutranFreqRelation. L3 Traces: te e all Ft_ERAB_SETUP . Resolution:- Tuning pdcchCfiMode to the optimum value of 5(dynamic. Change EutranCellFDD.qRxLevMin to higher values. If the last bucket has high number of samples in the degraded hours.ACCESSIBILITY 13 (15) Prepared (Subject resp) No. LTE. if the coverage is not an issue. LTE. the Paging is discarded and counter pmPagDiscarded is incremented by the number of included Paging Records in the discarded Paging message.g. S1 Paging % S1 Paging discard rate: shows the discard rate of paging messages due to max intensity of incoming S1AP Paging messages are forwarded to the eNodeB. . When the cell fails to broadcast an RRC Paging within a certain time (pagingDiscardTimer). pagingDiscardTimer(3s): The length of time a received paging is retained or queued in the RBS before it is discarded. The timer should be set to the same (or smaller) value as the paging resend timer in MME (T3413). %Cell Paging discard rate = 100 * pmPagDiscarded / pmPagReceived iii. S1 Issues with the MME(MME Codes) There can be issues where the paging attempts have reduced to Zero. An S1AP Paging message discarded as part of pmPagS1Discarded will not cause this counter to be pegged.ACCESSIBILITY 14 (15) Prepared (Subject resp) No. e. Deepak Gupta Approved (Document resp) Checked Date Rev Reference 2017-02-28 5) Paging :- i. it is routed to one cell (pmPagReceived). This setting prevents the RBS from retaining or sending an old paging after the re-sent copy is received from the MME. . Paging Discards by Cell:- After the S1AP Paging message is correctly received and not discarded by RBS. A restart can help in that case. due to congestion. % S1 Paging discard rate = 100 * pmPagS1Discarded / pmPagS1Received ii. LTE.ACCESSIBILITY 15 (15) Prepared (Subject resp) No. Deepak Gupta Approved (Document resp) Checked Date Rev Reference 2017-02-28 .