Q#01: What are the failure reasons of SRVCC?
- We need to check strategy of SRVCC either it is PS HO or Redirection (Recommended: PS HO).
- Thresholds for SRVCC also need to be checked, in VDF we were using -108 & default is -115, Upon decreasing the value for this threshold, it means Traffic will be transferred from LTE to 3G.
- We need to check switch for SRVCC either it is enabled or not on eNB level.
- 3G frequencies on LTE side should be defined properly. MML: lstutrannfreq
Q#02: What is Group & adaptive/Frequency based CA?
1- In Group based CA, we need to define cells in the form of groups of different frequencies (bands) for which we need to define CA.
MML: ADD CAGROUPCELL (Group Cells), ADD CAGROUP (Particular Uni que CA Group), MOD CAMGTCFG (Management Configuration).
Drawback: If Inter site NBs are not defined then CA will not work So NBs should be properly defined.
2- In Frequency/adaptive based CA, we need to define frequencies of carriers (L800 & L900 two way), even if NBs are not defined CA will work because it is frequency based.
How to activate Frequency based CA:
a) Remove CA group by RMV CAGROUP.
b) MOD ENODEBALGOSWITCH & enable frequency-based CA switch.
c) ADD PCCFREQCFG (need to define priority and primary cell frequency).
d) ADD SCCFREQCFG (need to define priority & secondary cell frequency).
Q#03: What are the Reasons of CA not working?
- First, we need to check type of CA we are using either Group/Frequency based.
- If we are using group-based CA then we need to check Group & Group Cells are defined properly with accurate Cell IDs & Inter Site NBs are added or not also eNB level switch is ON/OFF.
- UE Issue (if in case UE is locked on one specific frequency).
- If we are using Frequency based CA, frequencies are properly defined or not, moreover eNodeB level switch is ON/OFF.
Q#04: How can you analyze Drop reasons through FMA tool?
- We need to collect Board logs (CHR) from U2000.
- Then through FMA tool, we can check High Drop# from Retainability.
- May be Drop Rate is high just because of only one problematic UE & we can check this type of issue through IMSI of that UE (when we find IMSI, IMEI can be obtained from EPC side).
Q#04: What are Reasons of HO Failures in LTE?
1- If Inter HO Failure Rate is higher at a particular region then failure occurs and UE will not be able to attach target eNodeB, as a result call drops.
Solution:
a) You should increase TTT value in order to make handover harder to happen. Parameters to change are;
i) InterFreqHoA1A2TimeToTrig
ii) InterFreqHoA4TimeToTrig.
b) You should increase the hysteresis value. Parameters to change are;
i) InterFreqHoA1A2Hyst
ii) InterFreqHoA4Hyst
2. HO failures occur if there are Ping Pong Handovers. Ping Pong happens when UE becomes indecisive when UE wants to handover to a particular eNodeB.
| Parameter Name | Definition | Default Value | Recommended Value |
| FilterRsrp | Indicates the alpha filtering coefficient used by the UE during RSRP measurement for path loss estimation. | FC6 | Lower value than FC6. Possible Values: FC0-5. |
| GAP measurement pattern | Indicates the measurement gap pattern | Pattern 1 | Pattern 2 |
3- PCI Confusion.
Q#04: What is ANR? How ANR is working? On which basis ANR adds/removes NB (Neighbour) relations?
It is Automatic NB Relation to maintain NRT (NB relation Table; MML: lsteutranextcell we can get following info like CIO, Forbid/Blacklist status, NB Frequencies) & NCL table (NB Cell List; MML: lsteutraninterfreqncell/lsteutranintrafreqncell we can just get NCL).
Working:
Fast ANR: it periodically measures reported PCI of UE & reads CGI of missing NBs. In case of Fast ANR, may be all UEs are involved so once it crosses the threshold of max UE# it will not add further UEs.
For InterFreq missing NBs, it affects system throughput. We can define 64 NBs/Cell
Addition: There are RSRP thresholds, default is -102 dBm for LTE, -106 dBm for 3G RSCP & -103 dBm for GSM RxLevel (RSSI based).
Removal:
a) ANR delete cell threshold: we can define SR of HOs. Default is 0 & range is 0-100
b) Least No of HOs: Default is 200 & Range is 1-10000
c) Static Cycle: Default time is 24 hours (1440 minutes).
Event ANR:
It is triggered on the basis of HO Events (Triggering). It produces Delay due to reading of CGI but advantage is that there is no periodic measurement that leads to the threshold of max UE#.
Q#05: What is MOD3, MOD6 & MOD30? MOD3 interference?
MOD3:
1- The same site should not use the same PCI again on the same frequency.
2- The NBRs of the site should not have the same PCI on the same frequency.
3- Ideally, two NBRs of the site should not have same PCI between them.
MOD6: If the system is only a single port system like most of the IBS systems, then the PCI mod3 will not impact because there will be no reference signals on the second port. Instead, the rule will change to PCI mod6.
MOD30: Just like in downlink, every 3rd or 6th PCI collides on the reference signals, every 30th PCI has the same pattern of uplink reference signals. In uplink, the reference signals are present in the central symbol of the slot and their pattern or base sequence repeats for every 30th PCI. In case, two adjacent cells have same PCI mod30, then the cell can have difficulty in decoding which can result in higher block error rate in uplink.
However, this is not acritical issue and very rarely observed in the commercial networks.
MOD3 Interference: If we have a collision on Reference Signal between the two ports. This is known as the PCI mod3 issue/interference.
Q#06: What is OMSTAR Tool and for which purpose do we use this tool?
1- Network Audit.
2- Neighbour Audit.
3- EP Audit with configuration files obtained from U2000.
4- CHR Analysis.
Q#06: What is MIMO?
1- Full Form: Multiple Input Multiple Output.
2- MIMO technique uses multiple transmit and receive antennas during transmission. Advantages of MIMO includes the following;
- Power Gains.
- Array Gains.
- Multiplexing Gains.
- Diversity Gains.
3- Downlink MIMO Techniques.
•Open-Loop MIMO: No PMI feedback from UE.
•Close-Loop MIMO: PMI feedback from UE is required.
•Transmit Diversity: Same information is transmitted from multiple antennas.
•Spatial Multiplexing: Different Information is transmitted from multiple antennas.
4- Adaptive MIMO Transmission Mode: eNodeB dynamically selects the TM mode for every connected UE (RRC_CONNECTED) in the network.
| Condition | Transmission Mode |
| High SNIR, Low Channel Correlation. | Spatial Multiplexing (SM). |
| Low SNIR. | Transmit Diversity (TX Div.) |
| Stationary or Low Speed UE. | Closed Loop Transmit Diversity (CLTD). |
| High Speed UE. | Open Loop Transmit Diversity (OLTD). |
U2000 Check:
1- Check if the MIMO setting is matched in U2000 and in the field (sometimes physically it is configured as 2T2R but in U2000 it is configured 1T1R, you can discover it if RANK1 utilization is 100%). But note it that indoor sites are 1T1R.
2- DSP LICINFO command to check whether the license control item LLT1DMIMO01 or LLT1DMIMO02 is valid. If it is invalid, load a valid license file for this item.
3- Check the UE category. If the UE category is 1, the UE does not support spatial multiplexing. Replace the UE with the one of a higher category.
4- LST CELLDLSCHALGO command to check whether the value of the maximum number of MIMO layers parameter is SW_MAX_SM_RANK_1 (Rank1). If yes, change it to SW_MAX_SM_RANK_2(Rank2) or SW_MAX_SM_RANK_4(Rank4).
5- LST CELLMIMOPARACFG command. If TM2 or TM6 is configured as a fixed transmission mode, change it to another fixed transmission mode that supports two code-words based on the network plan.
Q#07: How to Improve Throughput?
To improve throughput in an LTE network, you can focus on both the control part and the data part:
A) Control Part:
PDCCH Allocation Based on BLER Target:
- BLER Target & CQI Input: The PDCCH (Physical Downlink Control Channel) allocation is influenced by the Block Error Rate (BLER) target and the Channel Quality Indicator (CQI) reported by the UE (User Equipment). A higher CQI means better radio conditions, allowing the eNodeB to allocate fewer CCEs (Control Channel Elements), which improves throughput.
- Dynamic PDCCH Power Adjustment: Increasing PDCCH power without changing the aggregation layer can improve robustness and help increase throughput.
- Tuning BLER Target: Slightly increasing the BLER target can reduce PDCCH expansion, leading to lower CCE utilization and reduced overhead, thereby improving throughput. However, excessive BLER target increases may lead to PDCCH decoding failures and retransmissions.
- PDCCH Coding Rate Adjustment: Higher coding rates for PDCCH can reduce the robustness, so a balance must be maintained when shifting from Open Loop to Closed Loop MIMO.
B) Data Part:
From LTE’s perspective, if the number of bits transmitted in a subframe (time) over a specific number of Resource Blocks (frequency bandwidth) is high, then it will correspond to higher throughput and higher spectral efficiency. Let’s understand the various factors impacting the spectral efficiency and ways to perform LTE throughput optimization.
Improve SINR (Signal-to-Interference-plus-Noise Ratio):
- Inter-Site Distance: Adjusting site placement and using electrical down-tilt to avoid overshooting can reduce interference. Balancing Reference Signal (RS) power with appropriate Pa and Pb values can also optimize SINR. There are two parameters in LTE Pa and Pb which define the power of the Reference Signals against the other symbols e.g. PDSCH Symbols. in case of small inter-site distance, Pb and Pa values of 0 might provide a more optimized solution.
- Load & Utilization: Monitoring TA (Timing Advance) and CQI to optimize load and utilization, especially in high-traffic cells.
- PCI Planning: Avoiding PCI (Physical Cell Identity) modulo 3 conflicts and disabling time synchronization in FDD networks can reduce interference.
CQI & MCS Mapping:
- Ensuring optimal CQI and MCS (Modulation and Coding Scheme) mapping for each SINR value can significantly boost throughput.
Mobility Strategy:
- Higher CQI Layer Transition: Optimizing handovers and transitions to maintain or increase CQI levels.
- Load Balancing: Effective load balancing in both idle and connected modes ensures optimal resource utilization.
Scheduler Fairness:
- Scheduler Algorithms: Implementing or optimizing scheduling algorithms like Round Robin, Max C/I (Carrier-to-Interference), and Proportional Fair to balance fairness and throughput.
Q#08: How to resolve PCI confusion?
i) Need to check Tilts.
ii) Need to check NB relation.
Q#09: What is CSFB Strategy you are/were using?
BLINDHOREDIRECTION.
i) CSFB Lowest priority InterRat for Idle UE: Indicates the lowest-priority RAT for CSFB initiated by a UE in idle mode. It is CDMA2000 by default. If this parameter is set to UTRAN, GERAN, or CDMA2000, the lowest-priority RAT is UTRAN, GERAN, or CDMA2000, respectively. If this parameter is set to NULL, no lowest-priority RAT is specified and only the highest- or mediumpriority RAT can be selected for CSFB initiated by a UE in idle mode.
ii) CSFB to UTRAN Blind Redirection RR Switch: Indicates whether the eNodeB selects the target frequency in a round robin (RR) manner from frequencies with the same priority in blind redirections for CSFB to UTRAN. If this parameter is set to ON(On), the function of target frequency selection in an RR manner is enabled. If this parameter is set to OFF(Off), this function is disabled.
MML: LST CSFALLBACKBLINDHOCFG:
Q#10: Diff between R8 and flash CSFB?
R8 CSFB: (Two Scenarios)
i) Blind Scenario: If the eNodeB is configured to provide blind handovers (that is, if BlindHoSwitch under the HoModeSwitch parameter is turned on), it does not deliver the measurement configuration to the UE. Instead, the eNodeB performs a blind handover.
ii) Measure Scenario: In Measure Scenario, eNB sends the UE the measurement configuration, according to which the UE performs measurements on the specified system. The measurement configuration sent to the UE contains the configuration information for only the RATs and frequencies that are supported by the UE.
Flash CSFM: We use RIM (RAN Information Management) features, which gives us information of 3G PSCs & reduces delay.
Q# 11: What is MLB?
Introduction: Inter-RAT MLB coordinates load distribution among inter-RAT cells. For this purpose, MLB checks the load status of cells and transfers UEs from heavily loaded cells to lightly loaded inter RAT cells.
Benefits:
i) Relieves load imbalances among inter-RAT cells by transferring appropriate UEs to interRAT neighboring cells.
ii) Increases the access success rate, improves user experience with telecommunication services, and achieves better overall resource utilization.
Parameter Optimization: The following parameters may need to be adjusted for better performance:
i) CellMLB.InterRatMlbThd: This parameter determines the probabilities and effect of inter-RAT MLB.
ii) CellMLB.InterRatMlbUeNumOffset: A larger value of this parameter results in a lower probability of ping-pong load transfer.
iii) CellMLB.InterRATMlbUeNumThd: This parameter determines the probabilities and effect of interRAT MLB.
Q# 13: When RRC Re-Establishment messages occurs and tell about its Counters?
If the RLF (Radio Link Failure) occurs before the UE gets the SMC (Security Mode Command), then there will be no RRC Reestablishment but if the RLF (Radio Link Failure) occurs after the UE gets the SMC (Security Mode command), then the UE will send a RRC Reestablishment.
Similarly, for example if the N310 value is 2 then it means that if the UE fails to decode PDCCH for 210 ms, it will have exceeded the configured N310 threshold. Once, N310 has been exceeded, the UE starts timer T310 and if the UE is unable to retain the connection (still unable to decode PDCCH) before T310 expires, the UE will initiate RRC Reestablishment.
Optimization:
RRC Reestablishment Optimize Switch
MO: GlobalProcSwitch
MML: LST/MOD GLOBALPROCSWITCH
Recommended Value:
PCI_CONFUSION_REEST_SWITCH:On
S1_HANDOVER_REEST_SWITCH:On
NO_CONTEXT_REEST_SWITCH:On
SEC_CMD_REEST_SWITCH: On
WITH_X2_NO_NCELL_REEST_SWITCH: On.
Q# 15: Which parameters need to check during cluster optimization?
i) SINR.
ii) MOD3 Interference (PCI Confusion & collision).
iii) HO Delay need to check or Illogical HOs or HO Failures.
iv) Session/Call Drop.
v) Low Throughput patches.
Q# 17: LTE Events?
There are 5 different handover types Events:
i) Event A1 is triggered when the power value of the serving cell is better than the threshold.
ii) Event A2 is triggered when the power value of the serving cell becomes worse than the threshold.
iii) Event A3 is triggered when the power of the target cell is greater than the power of the source cell by an offset.
iv) Event A4 is triggered when the power of the target cell becomes better than a defined power threshold.
v) Event A5 is triggered when the target becomes better than a threshold and when the source becomes worse than a threshold.
Q#18: What is Root Sequence Index & PRACH Root Sequence Index Planning?
The Root Sequence Index is a key parameter in the Physical Random Access Channel (PRACH) configuration, which is crucial for the initial access procedure in LTE. It determines the sequence of PRACH preambles that the User Equipment (UE) uses to connect to the cell.
Key Points about Root Sequence Index:
- Broadcast in SIB 2:
- The Root Sequence Index is broadcast as part of the PRACH configuration in System Information Block 2 (SIB 2) of the LTE cell. This allows UEs to calculate which PRACH preambles to use when attempting to connect to the network.
- Zadoff-Chu Sequence:
- PRACH preambles are based on Zadoff-Chu (ZC) sequences, which are complex sequences known for their constant amplitude and zero autocorrelation properties. The length of the Zadoff-Chu sequence in LTE is 839.
- PRACH Preamble Generation:
- Each LTE cell requires 64 distinct PRACH preambles. These preambles are generated by applying a cyclic shift to the Root Sequence Index. The cyclic shift ensures that multiple preambles can be derived from a single ZC sequence.
- Cell Radius and Cyclic Shift:
- A larger cell radius necessitates a larger cyclic shift because the transmission delay increases with the cell size. To accommodate this, more root sequences may be needed to generate the 64 required preambles in larger cells.
- Orthogonality of Sequences:
- Orthogonal sequences are preferred as they minimize interference and allow for clearer signal detection.
- Cyclic shifts of a single root sequence are orthogonal to each other, which is ideal for generating multiple PRACH preambles.
- When the number of required preambles exceeds what can be generated from a single root sequence, additional ZC root sequences may be used. However, sequences obtained from different ZC root sequences are not orthogonal, leading to potential interference.
PRACH Root Sequence Index Planning:
Effective planning of the PRACH Root Sequence Index is crucial to ensure reliable network access and minimize interference, particularly in cells with larger radii. The planning involves:
- Selecting an appropriate cyclic shift value based on the cell size to ensure all 64 preambles can be generated without requiring too many root sequences.
- Avoiding the use of multiple root sequences where possible to maintain the orthogonality of the PRACH preambles.
- Ensuring that the Root Sequence Index is correctly configured in SIB 2 for each cell, so UEs can calculate and use the appropriate preambles for initial access.
Q# 17: Diff between Blind and Measurement based CSFB?
Blind: It can choose any 3G cell blindly & hence reduces delay but affects HO SR.
Measurement: It chooses particular PSC with good RF condition & increases delay.
Q# 18: Which Necessary KPIS need to check?
Q# 19: What are Parameter to show Root Sequence Index? (RootSequenceIdx)
Description:
Meaning: This parameter indicates the initial logical index number of the ZC root sequence used in preamble sequence generation.
Value type: interval
Value range: 0 to 837
Unit: none
Default value: 0
Impact scope: cell.
Setting:
Modifications on this parameter affect the orthogonality of the preamble sequences for the cell and its neighboring cells.
Related Commands:
LST CELL: LocalCellId=0
MOD CELL: LocalCellId=0, RootSequenceIdx=0
Q# 20: Differentiate between Redirection, PS HO & CCO?
1. Redirection:
In redirection, the eUTRAN (Evolved Universal Terrestrial Radio Access Network) releases the UE (User Equipment) from its current connection and provides information for redirecting the UE to another RAT (Radio Access Technology). The key point is that the target RAT’s RAN (Radio Access Network) is not prepared with the UE’s information.
The UE moves from a connected state in the current RAT (e.g., LTE) to an idle state in the target RAT (e.g., 2G/3G). After redirection, the UE must initiate a connection establishment in the target RAT.
Typically used when transitioning from LTE to another RAT without the need to maintain an ongoing session.
2. Cell Change Order (CCO):
CCO is only supported for GERAN (GSM EDGE Radio Access Network). It involves instructing the UE to change to a specific target cell. Unlike redirection, the eUTRAN does not prepare the target RAT with the UE’s information, but it provides the necessary parameters (like SIB info) to help the UE find and synchronize with the target cell.
The UE remains in a connected state until it completes the CCO procedure. The eUTRAN releases the connection only after the UE has successfully accessed the target GERAN cell. If the CCO to GERAN fails, the UE remains connected to the eUTRAN.
Mainly used when precise control is needed over the target cell selection in GERAN, ensuring the UE switches to a specific cell.
3. Packet-Switched Handover (PSHO):
PSHO involves pre-registration and pre-allocation of resources in the target RAT. It’s a more complex procedure where the target RAT’s RAN is prepared with the UE’s information before the handover takes place.
The UE moves directly from a connected state in the current RAT (e.g., LTE RRC_CONNECTED) to a connected state in the target RAT (e.g., UTRAN RRC_CONNECTED). This ensures a seamless transition, maintaining the ongoing session.
Used when there is a need to maintain an active connection across different RATs (e.g., when transitioning from LTE to 3G) without dropping the session.
Major Differences:
- Redirection and CCO transition the UE from a connected state to an idle state.
- PSHO transitions the UE from a connected state to a connected state.
Preparation of Target RAT:
- In Redirection and CCO, the target RAT’s RAN is not pre-prepared with the UE’s information.
- In PSHO, the target RAT’s RAN is pre-prepared with the UE’s information, enabling a seamless handover.
- Redirection can target multiple cells or frequencies, while CCO directs the UE to a specific cell.
- In the case of CCO failure, the UE returns to LTE; with Redirection, the UE can attempt to connect to any available system.
Q# 21: What is Cell Radius vs Root Sequence Index relation in planning?
It is basically a relation between preamble format configuration vs. the maximum cell radius during the random access procedure. For example, Preamble Format 0 supports a maximum cell radius of 14.5 km. Another random-access parameter that affects the cell size is the cyclic shift.
Q# 22: What is Beam Forming? In which Transmission Mode it is used?
Beamforming uses multiple antennas to control the direction of a wave front by appropriately weighting the magnitude and phase of individual antenna signals (transmit beamforming). It is used in Transmission Mode-7.
Q# 23: DL Scheduling?
DL scheduling performs three operations:
- Selects UEs to be scheduled.
- Determine MCSs to be used.
- Determines the number and positions of RBs to be allocated.
Huawei eNodeB supports four scheduling strategies:
o Max C/I.
o Round Robin (RR).
o Proportional Fair (PF).
o Enhanced Proportional Fair (EPF).
The downlink scheduling strategy is decided by the DlschStrategy parameter, and the uplink scheduling strategy is decided by the UlschStrategy parameter.
With Max C/I, RR, and PF scheduling strategies, dynamic scheduling is used for all services. With the EPF scheduling strategy, only the VoIP services use semi -persistent scheduling.
Relevant Configuration:
Q#23: When Does the RRC Connection Reconfiguration Message Occur?
The RRC Connection Reconfiguration message is a critical signaling message in LTE (and NR) that is sent from the eNodeB (evolved NodeB) or gNodeB to the User Equipment (UE). This message is used to modify the RRC (Radio Resource Control) connection, and it plays a vital role in managing various aspects of the UE’s connection to the network.
- Direction: eNodeB/gNodeB to UE (Downlink signaling).
- Signaling Radio Bearer (SRB): SRB1 is used to carry this message.
- RLC Mode: Acknowledged Mode (AM) is employed to ensure reliable delivery.
- Logical Channel: DCCH (Dedicated Control Channel) is used for transmitting the RRC message.
- Transport Channel: DL-SCH (Downlink Shared Channel) is the transport channel over which the message is sent.
The RRC Connection Reconfiguration message can occur in the following scenarios:
Establish/Modify/Release Radio Bearers:
This message is used to establish new radio bearers, modify the configuration of existing radio bearers, or release them. Radio bearers are responsible for carrying the actual data (user or signaling) between the UE and the network.
Perform Handover:
During a handover, the RRC Connection Reconfiguration message is sent to instruct the UE to switch from one cell (or frequency/RAT) to another. This ensures that the UE remains connected while moving through different cells or even switching between LTE and other technologies like 3G.
Setup/Modify/Release Measurements:
The network can command the UE to perform specific measurements (e.g., signal strength of neighboring cells) via the RRC Connection Reconfiguration message. It can also modify the existing measurement configuration or stop certain measurements.
Add/Modify/Release SCells (Secondary Cells):
In Carrier Aggregation (CA), the RRC Connection Reconfiguration message is used to add, modify, or release secondary cells (SCells) that the UE uses alongside the primary cell (PCell) to enhance throughput and capacity.
Transfer Dedicated NAS Information:
The message can also carry dedicated Non-Access Stratum (NAS) information from the eNodeB to the UE. This information is typically related to mobility or session management.
Q# 25: What is LTE event in CA?
Related Events.
i) Event A1 Indicates the RSRP threshold for inter-RAT measurement event A1. When the measured RSRP value of the serving cell exceeds this threshold, an event A1 report will be sent.
ii) Event A2 (Searching) indicates that the signal quality of the serving cell becomes lower than a specific threshold.
iii) Event A3 (Intra) indicates that the signal quality of the PCell’s neighboring cell becomes higher than that of the PCell.
iv) Event A4 (Inter) indicates that the signal quality of a neighboring cell becomes higher than a specific threshold.
v) Event A5 (A2+A4) indicates that the signal quality of PCell becomes lower than a specific thresh and signal quality of a neighboring cell becomes higher than another threshold.
vi) Event A6 indicates that the signal quality of an SCell’s intra-frequency neighboring cell becomes higher than that of the SCell. If the eNodeB receives an event A6 report, it changes the SCell while keeping the PCell unchanged.
Q# 26: What is PCC Anchoring?
In PCC anchoring, an eNodeB selects a PCell for a CA UE based on PCell or PCC priorities. To prioritize certain frequencies as PCCs, an operator can set high PCell or PCC priorities, so that the eNodeB will select the highest priority cell or carrier as the PCell or PCC for the UE.
NOTES:
i) When a CA UE initially accesses a network, the eNodeB skips PCC anchoring if a bearer for an emergency call or with a QoS class identifier (QCI) of 1 has been established. The purpose is to prevent gap-assisted measurements from affecting voice quality. (Bearers with a QCI of 1 are used to carry Volte services.)
ii) After PCC anchoring is enabled, the number of inter-frequency handovers increases.
iii) A gap-assisted measurement timer is used in PCC anchoring and SCell configuration for carrier management. The timer has a fixed length of 3s.
Q# 27: CSFB Failures Issues and reasoning and solution?
i) Parametric issue (eNB level switch BLINDHO is off, redirection OFF, 3G Frequency not defined in lstutrannfreq).
ii) RF Condition (pilot pollution, coverage gaps).
iii) UE Issue.
Q# 28: Tell briefly about some LTE Timers?
| Timers | T300 | T302 | N311 |
| MO | UeTimerConst | RrcConnStateTimer | UeTimerConst |
| MML Command | LST/MOD UETIMERCONST | LST/MOD RRCCONNSTATE TIMER | LST/MOD UETIMERCONST |
| Meaning | This timer is started when the UE sends RRCConnectionR equest. Before the timer expires, it is stopped if the UE receives RRCConnectionSe tup or RRCConnectionR eject. After the timer expires, the UE enters the RRC_IDLE state | T302 specifies the time during which a UE whose RRC connection request is rejected has to wait before the UE can initiate a request again. This timer is started when the UE receives an RRCConnectionR eject message and stopped when the UE enters the RRC_CONNECTE D mode or performs cell reselection. | Indicates the maximum number of successive “in sync” indications received from L1. |
| Default Value | MS1000_T300(10 00ms) | 16 | n1(1) |
| Recomme nded Value | MS1000_T300(1000ms) | 16 | n1, n2, n3, n4, n5, n6, n8, n10 |
| Timers | S1MessageWaiting Timer | X2MessageWaitingTi mer | UuMessageWaiting Timer |
| MO | ENode BConnSta teTimer | ENode BConnSta teTimer | ENodeBConnStateTimer |
| MML Command | LST/MOD ENODEBCONNSTAT ETIMER | LST/MOD ENODEBCONNSTATE TIMER | LST/MOD ENODEBCONNSTAT ETIMER |
| Meaning | Indicates the timer governing the period that the eNodeB waits for a response message from the MME when the eNodeB performs an S1- based handover for a UE running non- QCI1 services. If the timer expires, the eNodeB initiates a UE context release over the S1 interface. If the eNodeB performs an S1-based handover for a UE running services with a QCI of 1, the S1MsgWaitingTimer Qci1 parameter controls the period that the eNodeB waits for a response message from the MME | Indicates the timer governing the period the local eNodeB waits for a response message from the peer eNodeB when the UE is running non-QCI1 services. If the eNodeBperforms an X2-based handover for a UE running services with the QCI of 1, the X2MessageWaitingTi merQci1 parameter controls the period that the eNodeB waits for a response message from the peer eNodeB | Indicates the timer governing the period the eNodeB waits for a response message from a UE when the UE is running non-QCI1 services. If the timer expires, the eNodeB initiates a UE context release over the S1 interface |
| Default Value | 20 | 20 | 35 |
| Recomme nded Value | 20 | 20 | 35 |