LTE Interview Questions – 100% Success With Interview – LTE Questions And Answers

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Knowing lte technology in detail is not very easy especially when you are preparing for lte interview questions as technology is a long term learning procedure.
However, you can start preparing yourself slowly but with important points so that you understand technology and know the basic answers,

Following article has 2 sessions. First one talks about LTE technology related lte interview questions whereas the second one talks about optimization and planning of LTE.

LTE TECHNOLOGY RELATED LTE INTERVIEW QUESTIONS

What is LTE Frame Structure?

	Configuration	(FDD)Frame Type 1	(TDD) Frame Type 2
	Frame Length	10 ms	10 ms
	Subframes per Frame	10	10
	Subframe Length (ms)	1	1
	Slots per Subframe	2	2
	Symbols/Slot, normal CP	7	7
	Symbols/Slot, extended CP	6	6

What is Difference between MIB and SIB?

MIB and SIM are two types of System Information (SI) that is broadcasted in the serving are of particular cell. SI is carried by the logical channel BCCH, which in turn is carried by either of the transport channels BCH or DL-SCH.
Master information Block (MIB): is a static part of SI and contain information like number of antennas, system bandwidth,PHICH configuration, transmitted power and scheduling information on how the SIBs are scheduled together with other data on DL-SCH. MIB is transmitted on the BBCH–> PBCH with periodicity of every 40 ms.
System Information Block (SIB): is a dynamic part of SI. It carry relevant information for the UE, which helps UE to access a cell, perform cell re-selection, information related to INTRA-frequency, INTER-frequency and INTER-RAT cell selections. It is mapped on DL-SCH –>PDSCH with periodicity of every 80 ms, 160ms or 320ms for SIB1,SIB2 and SIB3 respectively.

How many types of SIBs are available in LTE?

There are 13 types of SIBs for LTE.
 What does SIB1/SIB2/ … /SIB13 do?
Each SIB carry information related to specific tasks.

SIB-1	Carries Cell access related parameters like cell ID, MCC, MNC, TAC, scheduling of other SIBs
SIB-2	Carries Common and shared channel configuration, RACH related configuration are present; RRC, uplink power control, preamble power ramping, uplink Cyclic Prefix Length, sub-frame hopping, uplink EARFCN
SIB-3	Parameters required for intra-frequency, inter-frequency and I-RAT cell re-selections
SIB-4	Information regarding INTRA-frequency neighboring cells (E-UTRA)  carries serving cell and neighbor cell frequencies required for cell reselection as well handover
SIB-5	Information regarding INTER-frequency neighboring cells (E-UTRA); carries E-UTRA LTE frequencies, other neighbor cell frequencies from other RATs.
SIB-6	Information for re-selection to INTER-RAT (UTRAN cells)
SIB-7	Information for re-selection to INTER-RAT (GERAN cells)
SIB-8	Information for re-selection to INTER-RAT (CDMA2000)
SIB-9	Information related to Home eNodeB  (FEMTOCELL)
SIB-10	ETWS (Earthquake and Tsunami Warning System) information (Primary notification)
SIB-11	ETWS (Earthquake and Tsunami Warning System) information (Secondary notification)
SIB-12	Commercial Mobile Alert Service (CMAS) information.
SIB-13	Contains the information required to acquire the MBMS control information associated with one or more MBSFN areas.

On which channels SIBs are transmitted?

BCCH–> DL-SCH–> PDSCH.

Which SIBs are essential?

In LTE, for a UE to access the eNB, at the most minimum 2 SIBs are required (SIB1 and SIB2). Information regarding SIB2-SIB13 are carried in SI messages and are included in schedulingInfoList which is part of SIB1.

Why we need SIB19?

SIB 19 is needed when UE is coming back from 3G to 4G. LTE priority should be set high in 3G. SIB19 carries the absolute priority of the serving UMTS cell, the absolute priorities of the LTE frequencies, and the cell reselection thresholds.

How can we calculate LTE DL/UL throughput?

Note: Please see tables in Q.1 and Q.3 for relevant info provided in below answer.

• Lets’ assume we have 20 MHz channel bandwidth.
• we need to calculate the resource elements in a subframe for this band i.e.

12subcarriers x 7 OFDMA symbols x 100 resource blocks x 2 slots= 16800 REs per subframe.

• • Assume we have 64 QAM modulation and no coding, one modulation symbol will carry 6 bits.

16800 modulation symbols x 6 bits / modulation symbol = 100800 bits.
So, the data rate is 100800 bits / 1 ms = 100.8 Mbps.

• With 4×4 MIMO, the peak data rate goes up to 100.8 Mbps x 4 = 403 Mbps.
• Estimate about 25% overhead e.g. PDCCH, reference signal, sync signals, PBCH, and some We get 403 Mbps x 0.75 = 302 Mbps.

 

What is SON & how does it work in LTE? 

Self-configuring, self-optimizing wireless networks is not a new concept but as the mobilenetworks are evolving towards 4G LTE networks, introduction of self configuring and self optimizing mechanisms is needed to minimize operational efforts. A self optimizing functionwould increase network performance and quality reacting to dynamic processes in the network.This would minimize the life cycle cost of running a network by eliminating manualconfiguration of equipment at the time of deployment, right through to dynamically optimizingradio network performance during operation. Ultimately it will reduce the unit cost and retailprice of wireless data services.See Self-configuring and self-optimizing Networksin LTE for details.

 

How does Timing Advance (TA) works in LTE? 

In LTE, when UE wish to establish RRC connection with eNB, it transmits a Random AccessPreamble, eNB estimates the transmission timing of the terminal based on this. Now eNBtransmits a Random Access Response which consists of timing advance command, based onthat UE adjusts the terminal transmit timing.The timing advance is initiated from E-UTRAN with MAC message that implies and adjustmentof the timing advance.See Timing Advance (TA) in LTE for further details.

 

How does LTE UE positioning works in E-UTRAN? 

UE Positioning function is required to provide the mechanisms to support or assist thecalculation of the geographical position of a UE. UE position knowledge can be used, forexample, in support of Radio Resource Management functions, as well as location-basedservices for operators, subscribers, and third-party service providers.See LTE UE positioning in E-UTRAN for more details.

 

How does Location Service (LCS) work in LTE network? 

In the LCS architecture, an Evolved SMLC is directly attached to the MME. The objectives of thisevolution is to support location of an IMS emergency call, avoid impacts to a location sessiondue to an inter-eNodeB handover, make use of an Evolved and support Mobile originatedlocation request (MO-LR) and mobile terminated location request MT-LR services.Release 9 LCS solution introduces new interfaces in the EPC:

 

SLg between the GMLC and the MME

 

SLs between the E-SMLC and the MME

 

Diameter-based SLh between the HSS and the HGMLC

 

How does Lawful Interception works in LTE Evolved Packet System? 

3GPP Evolved Packet System (EPS) provides IP based services. Hence, EPS is responsible only forIP layer interception of Content of Communication (CC) data. In addition to CC data, the LawfulInterception (LI) solution for EPS offers generation of Intercept Related Information (IRI) records from respective control plane (signalling) messages as well.See Lawful Interception Architecture for LTE Evolved Packet System for more details.

 

 

What is carrier aggregation in LTE-Advanced?

To meet LTE-Advanced requirements, support of wider transmission bandwidths is requiredthan the 20 MHz bandwidth specified in 3GPP Release 8/9. The preferred solution to this iscarrier aggregation.It is of the most distinct features of 4G LTE-Advanced. Carrier aggregation allows expansion of effective bandwidth delivered to a user terminal through concurrent utilization of radioresources across multiple carriers. Multiple component carriers are aggregated to form a largeroverall transmission bandwidth.

What is LTE Intra E-UTRAN Handover?

Intra E-UTRAN Handover is used to hand over a UE from a source eNodeB to a target eNodeBusing X2 when the MME is unchanged. In the scenario described here Serving GW is also unchanged. The presence of IP connectivity between the Serving GW and the source eNodeB, aswell as between the Serving GW and the target eNodeB is assumed.The intra E-UTRAN HO in RRC_CONNECTED state is UE assisted NW controlled HO, with HOpreparation signalling in E-UTRAN.To prepare the HO, the source eNB passes all necessary information to the target eNB (e.g. E-RAB attributes and RRC context) and UE accesses the target cell via RACH following acontention-free procedure using a dedicated RACH preamble.The HO procedure is performed without EPC involvement, i.e. preparation messages are directlyexchanged between the eNBs. The figure below shows the basic handover scenario whereneither MME nor Serving Gateway changes:

What RBS Hardware does Ericsson use for LTE Technology?

RBS 6000 series

What is considered a good RSRP and RSRQ threshold, good for LTE radio conditions?

RSRP = >-95 dBm (Planning with -113 dBm)     RSRQ=<-7db span="">

What latency (RTT) have you experienced while pinging with 32 bytes?

40-200ms

What technology is used in the uplink and in the downlink?

Uplink: SCFDMA
Downlink: OFDMA

How many Transmission mode we have? What are they? How they are configured in moshell?

Transmission mode:

1. Single Input Multiple Output (SIMO)
2. Transmit Diversity
3. Open Loop Spatial Multiplexing (OLSM)

What other DT tool or any LTE tool have you ever used?

TEMS Discovery & Actix

What are the Radio Frame Structures Supported by LTE?

LTE Radio Frame:                                       

• Air Interface For 3G LTE.
• Manage the different types of information that needs to be carried between the eNodeB and the User Equipment.
• The frame structures for LTE differ between the Time Division Duplex, TDD and the Frequency Division Duplex, FDD
• Two adjacent slots constitute a sub-frame of length 1 ms
• There are two types of LTE frame structure:
  • Type 1:   used for the LTE FDD mode systems.
  • Type 2:   used for the LTE TDD systems

What is eNodeB Capacity?

eNodeB Capacity
Peak Bit Rate(Mbps)=bit per Hz x N subcarriers x N symbol per subframe in 1ms

Bandwidth (MHz)	Modulation
	QPSK	16 QAM	64 QAM
1.4	2.016 Mbps	4.032 Mbps	6.048 Mbps
3	5.04 Mbps	10.08 Mbps	15.12 Mbps
5	8.4 Mbps	16.8 Mbps	25.2 Mbps
10	16.8 Mbps	33.6 Mbps	50.4 Mbps
15	25.2 Mbps	50.4 Mbps	75.6 Mbps
20	33.6 Mbps	67.2 Mbps	100.8 Mbps

Whats difference b/w video download and video streaming?

Streaming is playing audio/video content in real time through the Internet. This does not eat up any space on your computer’s hard drive.
A fast Internet connection is required to view the videos at its clearest because the video quality is dependent on the speed of your connection. If you experience frequent pauses or buffering on your viewing or if you’re not satisfied with the quality, consider downloading the clip (if possible).
Downloading is transferring data from a server into your own computer. You need to have sufficient hard drive space to be able to save the content.
Although downloading may take some time, the advantages are that you can watch the content anytime since it’s already saved in your computer and you don’t need to be connected to the Internet to watch the video. The video will also be of higher quality with no interruptions upon playback

IMPORTANT LTE OPTIMIZATION STEPS & TECHNIQUES 

ACCESSIBILITY

• IDLE
  • Reference signal is used to measure quality
• Cell Selection
  • QRxLevMin -128 to -110 to discourage camping QRxLevMinOffset 0 to 2 will discourage camping,
  • Qqualmin -22 to 18 to discourage camping
  • Pcompensation max(PEMAX –PPowerClass, 0), pMaxServingCell, pMaxGeran
    • PMAX (max UE power)
    • Criteria for camping of Less power UEs is hard, pMaxServingCell 1000
  • Reselection
    • Start Reselection
      • SIntraSearch 29*2=-58dBm to 31 will encourage reselection
      • sNonIntraSearch 2 to 5 will discourage IRAT reselection, -114+5*2=-104dBm
      • TcrMaxConnMode (mobility calc) T_CRMAX_30S to T_CRMAX_60S will discourage reselection but increase precision, celResTiF, sIntrasearch, sNonIntrsearch
      • High mobility scaling QHystSfHigh DB0_Q_HYST_SF_HIGH(0dB) to DB_2_Q_HYST_SF_HIGH will discourage reselection, qRxlevminoffset 0 to 2
      • TreselectionRAT increase to decrease reselection, treSelection 7s
    • Reselection Decision
      • IdleQhyst1s (current cell) 4 to 2 will discourage sticking to current cell qHyst, qHyst 4
      • Cell offset qOffsetCellEUtran, qOffsetCell, qOffCell, interTResEut, qRxLevMinInterF, offsetFreq 2 to 0
      • CellReselPriority 0 to 2 for high priority, cellReselectionPriority 5 to 3 èdiscourage reselection, threshXHighHrpd, tReselectionEutra 2 to 4, tReselectionEutraSfHigh 3 to 2
      • NcellReselectionHigh 16 to 10 è UE enters high mobility state earlier
      • threshXHigh, threshXLow, tReselectionEutraSfHigh, threshServingLow 62, sPrioritySearch1,
      • interFrqThrH, tResEutSF, eutResTiFHM, celResTiFHM, cellReSelPrio 3 to 0 will discourage, mobStateParamNCelChgHgh, mobStateParamTEval, qRxLevMinOffset 0 to 2dB, q-RxLevMin, spStResPars, qHystSfHigh, tReselEutr, timeToTriggerSfMedium, tResUtra, tResUtraSF, utrResTiFHM
      • Qrxlevmeas
    • Tevaluation 30 to 60s, tEvaluation 240
    • T320
      • ATTACH T3410 (UE), T3450 (eNodeB)
      • System Information Messages SIB1(Access/Message scheduling, reselection),SIB2(UE timers,common/shared channel, UL RBs),SIB3(intra-freq reselect) systemInformationBlock3,SIB4(Intra neigh),SIB5 (inter-freq neigh), SIB6(Reselect to WCDMA),SIB-7(Reslect to GSM),SIB8(Reselect to CDMA)
    • Sib3Period RF16 to RF32 èless resources used but delay in access, maxCrSibDl, si4Periodicity
      • CellRadius
    • RRC setup success rate (service)
      • pZeroNominalPucch -117
    • RB=SRB+DRB
      • SRB0 is for RRC messages transmitted over the Common Control Channel CCCH
      • SRB1 is transmitted over the Dedicated Control Channel DCCH. RRC connection establishment is Signaling Radio Bearer-1. Theis is for NSN and RRC
      • SRB2: bearing NAS signaling and transmitted over the DCCH, This is for NAS and RRC of high priority
      • DRB bears data maximum of eight DRBs per UE with eNodeB
      • T302 4 to 6 s, timer b/w retries for RRC connection establishment
      • tlnactivityTimer
    • Causes emergency highPriorityAccess Mobile terminating Mobile Originating Signaling and mo-Data.
    • RRC failures RRC.ReEst.ReconfFail.Rej L.RRC.ReEst.HoFail.Rej, RA measurement(Random Access failures), PDCP discards, s1RetryTimer 30 to 40,
    • T300-5, T301, 200 to 300 ms, N310, N311
    • T310 indicates physical failure 200 to 300
    • T311 10000 to 150000 ms, RRC reestablishment
    • T3446
    • T3460 supervises authentication request.NAS timer
    • T3470 sueprvises identity request. NAS timer
    • T3410 UE timer supervises attach request
    • T3417, T3421 or T3430 retransmission timers
    • T3421 UE timer supervises detach procedure
    • RRC Setup Success Rate (Signaling)
    • PRACH (SIB2)
      • prach-ConfigurationIndex, Max Preambles, contention/non contention (specified RACH), Power ramping step DB0 to DB2, Preamble initial received target power DBM_104 to DBM_100, RA retries, PreambInitRcvTargetPwr DBM_120(-120dBm) to DBM_92(-92dBm) è performace of cell at the cost of interference on others, RachAlgoSwitch, maxCrRa4Dl, PRACH cyclic shift, prachFreqOff, prachPwrRamp, preambTxMax, raContResoT, raMsgPoffGrB, raNondedPreamb, raPowRampSetup, raRespWinSize, rootSeqIndex, ulpcIniPrePwr, ulpcRarespTpc, RACH density
        • Early contention resolution can improve the Access success rate
        • accessBarringTime s32 è T303
        • numberOfPRBsForDynamicallyScheduledPUSCHForRACHRegion, maxHARQmsg3Tx, maxRACHTransmitPower, pRACHPreambleDetectorThreshold, pRACHpowerSetting, prachFrequencyOffset, preambleInitialReceivedTargetPower, preambleTransMax, preambleTransmitPowerStepSize, adaptiveMsg3PowerControlEnable, sctpAccessAssociationMaxRetrans, sctpAccessEstablishmentMaxRetries
      • RA (Random Access) update for service request, location update, and paging. RACH is provided to UE.
        • Contention (preamble collision) initial RRC connection establishment, RRC connection reestablishment, uplink data arrival
        • Non Contention (preambles allocated) handover, downlink data arrival
        • BackOffSwitch adjust the back off time dynamically to relieve load on RACH
        • RACH process influences the call setup delay, handover delay, data resuming delay, call setup success rate and handover success rate.
        • AcBarringFactorForCall P95(95%) to 80 will discourage access
      • ATTACH
        • Incorrect LAC at MSC, TAC at MME
      • T3412 TAC update
      • T3414 UE attach with NAS
      • S1_implicitDetachTimer
      • S1_MobileReachableTimer
        • SON
          • RACH load (call arrival rate, HO rate, tracking area update, traffic pattern)
          • Interference on PUSCH channel
          • Paramaters that can be controlled are PRACH configuration index, RACH preamble split, RACH backoff parameter value, PRACH transmission power control parameters
        • 
          
      • FACH
      • PAGING
      • Discarded Paging Messages over the Uu Interface, pagingDiscardTimer 3 to 5s, T3413, , DefaultPagingCycle or DRX cycle rf128 to fr64 è shorter paging cycle. AS (UE & eNodeB) RRC service request, location update, and paging, maxCrPgDl, maxNumRrc, pagingNb, raCrntiReuseT, modificationPeriodCoeff 2, rrcConnReestActive 0 to 1 è RRC success, cellRange 15 to 10Km è success, coverageIndicator, nrOfRrcConnectedReserved, dlGbrAdmThresh,
      • T=defaultpagingcycle 1T to 1/2T è less paging time, high paging traffic, fewer groups, more UEs in a group,
      • nB T to 1/4Tè fewer and larger groups, less paging capacity
      • T=defaultpagingcycle 1T to 2T è more paging time, low paging traffic, more groups, less UEs in a group,
      • Nb è ONET (1T) to TWOT(2T) more paging capacity
      • maxNoOfPagingRecords3 to 5 èmore UEs in a paging message
      • Single paging message can accommodate a maximum of 16 paging records. Small TA è more LAC updates and chances of missing paging message increase
      • pagingForceMCSmin -1 to 2 èmin MCS scheme
      • NAS (UE & MME) procedure consists of attach, detach, tracking area (TA) update, service request, and extended service request.
      • RRC connection reestablishment caused by handover failure, RRC reconfiguration failure, or radio link failure downlink data arrival. uplink data arrival.
      • initial coding is set by parameter
      • CCCH
        • SRB-0
        • RRC(SRB-1) over DCCH Connection Request (Over CCCH from UE to eNodeB) èUE context/SRB1 allocation è RRC Connection Setup (eNodeB to UE) è RRC Connection Setup Complete (UE to eNodeB) è Initial UE Message (eNodeB to MME) è Initial Context Setup message (MME to eNodeB) è Security Mode command (eNodeB to UE)èRRC Connection Reconfiguration message(eNodeB to UE)è RRC Connection Reconfiguration Complete message (UE to eNodeB)
        • RRC(SRB-2) for ERABover DCCH,
      • Signaling Link Release RRC Release UeInactiveTimer 1800 to 2000s, load rebalancing
      • ERAB Setup Success Rate (VoIP)
      • ERAB Setup Success Rate (All)
        • E-RAB establishment = Signaling Radio Bearer-2 (SRB2) establishment and Data Radio Bearer (DRB) establishment. ERAB=RB(Um)-S1(S1)
        • 
          
      • Radio Network Unavailability Rate
      • 9 Radio Bearers RadioBeare rs _QCI _ 1 (highest) to 9
        • RRC reconfiguration establishment, modification and Release of RBs
        • SRB2 Inititial Context Setup Request (MME to eNodeB) è RRC connection reconfiguration (enodeB to UE)è RRC connection reconfiguration complete (UE to eNodeB) èIntial context setup (eNodeB to MME) èERAB setup request (MME to eNodeB) è RRC reconfiguration (enodeB to UE) è RRC reconfiguration complete (UE to eNodeB) è ERAB setup response (eNodeB to MME)
        • DRB ERAB modify request (MME to eNodeB) è RRC connection Reconfiguration (eNodeB to UE) è RRC Reconfiguration complete(UE to eNodeB) èERAB modify response(eNodeB to MME). 8 DRB max.
      • csFallbackPrio, s1RetryTimer, CS Fall-Back feature, GoldServiceArpThd 5 to 8 è access, Qci1HoThd 90 to 95 è access, NewGoldServiceOffset 10 to 5 è access to gold at the cost of silver/copper, a2TimeToTriggerRedirect, ocAcProbFac, acBarSig, sigAcProbFac, addAUeRrHo, qRxLevMinUtra
      • RAC is based on No. of RRCs and active users, maxNumActDrb
      • RRM, Dynamic Resource Allocation = Scheduling, resources modified are PRBs, Power, PDCCH/PUCCH Resources, TX rank, baseband power, UlBasebandCapacity DlBasebandCapacity
      • isRrcReEstablishmentAllowed
      • Channels
        • Downlink Control Channels
          • PCFICH (no of symbols in PDCCH depending upon signaling), maxNrSymPdcch,
          • PDCCH (scheduling, Downlink control info-DCI, MIMO mode, precoding, modulation, SIB, paging, broadcast, RACH response)
            • DCI-0 uplink scheduling, RB group assignment, UL grant
            • DCI-1 modulation, TPC, coding, RB assignment
            • Resource allocation type-0
            • Resource allocation type-1
            • Resource allocation type-2 Resource indication Value-RIV (like pointer)
            • DCI-2 downlink shared channel assignments in case of closed loop spatial Mux
            • DCI-2A downlink shared channel assignments in case of open loop spatial Mux
            • DCI-3 TPC
            • CQI request
            • cFI 1 to 2 è increase in no. of PDCCH symbols, dynamicCFIEnabled
            • initial coding is based on control data volume
          • PHICH ack/nack
          • PBCH MIB 40 ms, pBCHPowerOffset, initial coding is set by parameter
          • PSS & SSS symbol and frame timing as well as cell identities
          • RS reference signals for cell recognition, channel estimation, path loss estimation, and handover measurement. srsBandwidth, srsHoppingBw, srsPwrOffset, nbrSRSperTTI
          • PCI 504 = 168 (secondary x 3 (primary group)
          • PDSCH for downlink data, deliver RA-RNTI,TA, uplink grant, contention response by eNB, Pb 0 to 3 & ReferenceSignalPwr 182 to 200 (20dBm) è high coverage/capacity but interference on others, PDSCH power boosting, initial coding is set by parameter
          • Paging initial coding is set by parameter
        • Uplink channels
      • PUCCH ack/nack, channel quality indication (CQI) reports, precoding matrix information (PMI) and rank indication (RI) for MIMO, and scheduling requests (SR). Control info is ent on this channel if PUSCH is not assigned to UE, pucchSize, pZeroNominalPucch, noOfPucchSrUsers, dynamicPUCCHEnabled
      • PUSCH data, freq hopping can be used, Intra-frame or Inter frame hopping, type 1 or 2 hopping demodulation reference signal is used for channel estimation sounding reference signal provides uplink channel quality CQI 16 values representing modulation scheme and coding format, pZeroNominalPusch -103 (power), HoppingMode HoppingOffset, cqiReportingModeAperiodic
      • PRACH Preambles, initial access, handover, UL sync and UL SCH resource requests. initial coding is set by parameter, NCS(prachCs)
      • DRS Demodulation reference signals for channel estimation
      • Sounding reference signals (SRS) are used to control frequency-dependent scheduling by the eNodeB and PSrsOffsetDeltaMcsDisable -30 to -15 increase power of SRS. Estimate channel quality, transmitted where there is no user data
      • Measurement messages are sent
      • POWER CONTROL
        • FPC Fractional Power Control, applicable on Cell-specific reference signal, PBCH. estimation, and handover measurement.
        • Commands are sent through DCI
        • Reference signal power -57, PCFICH power -3175, PBCH power -3174, Synchronization signals power, -3173, DBCH power -3172, Paging power -3171, Rach respond power
        • -3170, Prs Power -3169
        • SINR target and CQI, Downlik ICIC, scheduling affect power control
        • ICIC SON can change parameters HII, OI and DL TX Power indicator. ICIC changes scheduling strategies on serving and neighbor cells
        • CellDlpcPdschPa (enable PC or even power distribution)
        • partOfRadioPower 100, confOutputPower 20 to 40, confOutputPower, maximumTransmissionPower, rlfailureT, noutsyncInd, MinpwrRL, MinpwrMa, qRxLevMinInterF, dFpucchF1, dlPathlossChg, dlpcMimoComp, enablePcPdcch, p0NomPucch, p0NomPusch, pMax, pMaxIntraF, pMaxOwnCell, rxPowerScaling, tpcStepSize, ulpcAccuEnable, ulpcAlpha, ulpcEnable, ulpcIniPrePwr, ulpcLowlevCch, ulpcPucchEn, ulpcReadPeriod, ulpcUplevCch, ulpcUpqualCch, pMaxUtra, networkSignallingValue NS_01 (UE power attenuation)
        • Power Control of Signals
        • ReferenceSignalPwr 182(18dBm), offset of Sync signal SchPwr 0, PbchPwr -600(-3dB), PcfichPwr -600(-3dB), They affect the coverage. The cell-specific reference signal is used for cell recognition, channel estimation, path loss, Scaling factor Pb 1 to 3 (01,2,3)è High Power of Reference signal but at the cost of PDSCH, CellUlpcDedic, referenceSignalPower
        • PRACH PreambInitRcvTargetPwr DBM_104(-104dBm) to -102 , PwrRampingStep DB2 to DB4, retries, Increase in Power è more interference but good accessibility, FilterRsrp
        • PDCCH Carrying RACH Response, Paging Messages, SIBs. RaRespPwr, PagingPwr -3171, DbchPwr, They affect accessibility. Increase in Power è more interference but good accessibility.
        • PDCCH (RRC or SD)PC is dynamic w.r.t SIR targets and Static based on PdcchPwrDedi larger value è less drops but less UEs accommodated, throughput and accessibility is affected, PdcchBndPcSw is the switch for dynamic PC. maxNrSymPdcch,
        • PHICH carries HARQ and affects throughput. PC is dynamic w.r.t SIR targets and Static based on PhichPcOff, PhichResource 1 to 2 è more control resources. SINRRS(based on CQI) ≤SINRTarget then increased power
        • PDSCH Increase Pb and Pa to increase power of PDSCH. PaCenterUe PA_0, PPDSCH_A, PO_PDSCH, pDCCHPowerOffsetSymbol1, paOffsetPdsch, pDCCHPowerControlMaxPowerDecrease
          • In Dynamic scheduling: CQI, transmission block, GBR, AMBR are considered to arrive at Pa value
          • In Semi-persistent scheduling: BLER target is considered
          • ICIC informs if user is at the centre or edge
        • PUSCH (UE) affects throughput ,PCMAX, Alpha (0.4 to 0.8) ègood for cell edge users but not of system performance, P0NominalPUSCH -67 to -58 large value è throughput of the cell increases but network decreases, DeltaMcsEnabled 0 to 1 è MCS value affects power control and throughput increases
          • Dynamic
            • SINR based
            • PH, RBs,
            • RBs and OI of neighbor
          • Semi persistent
            • BLER
          • PUCCH (UE) affects throughput. The PUCCH carries the ACK/NACK information, CQIs, and schedule request (SR) information related to downlink data. DeltaFPUCCHFormat1, PucchAlgoSwitch, P0NominalPUCCH -105 to -100 increases throughput but decreases network throughput
          • primarySyncSignalPowerOffset
          • SRS for uplink channel estimation and uplink timing, PSRS OFFSET, low power è low performance
          • maximumTransmissionPower, confOutputPower, sectorPower, pMaxInterF,
          • RaRspPwr PchPwr DbchPwr SchPwr PbchPwr PcfichPwr PrsPwr
          • PaPcOff
          • Open loop PC is based on path loss, broadcasted/RRC parameters
          • Closed Loop PC is based on UL level and quality measurements, CELL_PWR_RED
          • 
            
        • LOAD CONTROL
          • T320
          • RacAlgoSwitch enable admission and load control algo, MlbAlgoSwitch load balancing algo
          • ulAccGbrAdmThresh
          • loadTargetForOCNS RB based
          • loadTargetForOCNSonPDCCH Power based
          • Load Monitoring
            • Resource Limitation Indications
              • Downlink power limitation indication
              • PUCCH resource limitation indication
              • Sounding resource limitation indication PUSCH
              • Transport resource limitation indication
              • Cell Congestion AqmAlgoSwitch (queueing at the cost of integrity)
            • PRB usage, QoS satisfaction rate of GBR services, and resource limitation, DlRbHighThd 95 to 90 to encourage load control
              • UlRbHighThd 95 to 90 è Load control
            • QOS Satisfaction Rate, based on QCI, admission based on QOS
          • Admission Control
            • Check UE capability
            • Resource prediction or QoS satisfaction rate of Admitted services or check no. of PRBs
              • Resource: Allocation and Retention Priority (ARP), SRB for location updates and detach, GoldUserArpThd 5 to 4 will increase priority, MaxNonGbrBearerNum 3000 to 4000 will enhance admission. By limiting the number of PRBs used by GBR services, admission control increases the admission success rate
              • QoS: admission threshold for new gold services is QcixHoThd plus NewGoldUserOffset.
            • Service preemption and Redirection, PreemptionArpThd 5(ARP value) to 3 to encourage preemption
            • MaxNonGBRBearerNum 3000 to 4000 è admission
            • GbrRbUseHighProportion, dlAccGbrAdmThresh
          • Load Balancing
            • Intra-Frequency CIO(for connected mode), Qoffset in idle mode, Increase CIO and decrease Qoffset
            • IntraFreqMlbThd 60 to 50 for traffic shifting, LoadOffset 8 to 5,Neighbor with the lowest load is considered or in A category
              • Auto adjust CIO(for connected mode), Qoffset in idle mode
              • CIO decrease to discourage HO to neighbor
            • InterFreqMlbThd 60 to 55
            • InterRatMlbThd 75 to 70 unidirectional only, based on UE attributes, service attributes, load factors, and system performance.
            • LoadExchangePrd 10s to 8 èload control, imLoadBalancingActive, threshServingLowHystMin, threshXHighHystMin
          • Congestion Control
            • Preemption of GBR services with low energy efficiency rate (EER)
              • PreemptionArpThd 5 to 3 è congestion relief
            • GBR service rate downsizing
              • CopperGbrCongProportion 90% to reduction 80 reduction è congestion relief
            • Qci1CongThd 65 + CongRelOffset 20 < Qci1HoThd 90 to 85 è congestion relief? QcixHoThd is small èoverall QoS satisfaction rate of the admitted services is low but the admission of incoming handovers is easy and drop rate may increase.
            • Energy efficiency rate (EER) depend upon data amount, PRB used, Downlink Power. More data with less power è efficiency
              • if ARP is >= LdcMeaArpThd 10 to 5 è EER is calculated
              • LdcMeaArpThd 10 to 13 è congestion relief but drops increase

RETAINBILITY-CDR

• Call Drop Rate (VoIP)
• Service Drop Rate (All)
• Radio Network Unavailability Rate
• pZeroNominalPusch
• RAB Failures ERAB relase causes (normal,abnormal,HO, congestion, unavailability), ERAB modification causes, CQI measurement, MAC traffic retransmissions, no of users/edge users,PDCP discards/packet loss, UE context releases, Check RACH and power parameters
• Raw counters, Traces, Layer3, DT, PM events for diagnosis,
• CSFallBackBlindHoCfg
• CQI 0 to 15, MCS 0 to 31, QC1 to QC9, RANK 1 to 4
• T310 indicates physical failure 200 to 300
• UeInactiveTimer 1800 to 2000s
• T321
• Interference
  • IRC works at physical layer è MIMO
  • ICIC works at MAC layer, adjust center CCU and edge CEU UE loading
  • dlInterferenceManagementActive switch, noOfRxAntennas, tHODataFwdReordering 50 to 100 ms
  • tInactivityTimer, a5B2MobilityTimer, s1RetryTimer, tHODataFwdReordering, cellRange 15 to 10Km è low drops, coverageIndicator, ulInterferenceManagementActive, pMaxServingCell
• MIMO
  • Fading=Variance in SINR, 6dB gain with 4 antennas, adjust antenna weights to either minimize interference gain (MRC) – white Noise or maximize signal gain (IRC) – colored interference, Closed loop for slow moving and open loop for fast moving
• E-RAB Release Service, handover, actRedirect, taTimerMargin, addAUeRrHo, dlTargetBler, p0NomPusch, riEnable, riPerOffset, taMaxOffset, taTimer, ulamcSwitchPer, qQualMinUtra, qRxLevMinUtra
• DeltaPreambleMsg3 4 to 6, DeltaFPUCCHFormat2a DELTAF2(2dB), P0NominalPUCCH
• The definition of an abnormal release is that there shall be buffered data to be transmitted at the time of release èrelease of the E-RAB had a negative impact on the end-user.
  • Voice release, normalized to releases
  • PS releases, normalized to session time
    • tlnactivityTimer
    • T301
    • tTimeAlignmentTimer (Timer for TA UL sync)
    • T3411 failure in NAS signaling
    • T3410 failure in NAS signaling
    • T3430 failure in NAS signaling
    • T3417 failure in NAS signaling
    • T3440
  • groupHoppingEnabled, isRrcReEstablishmentAllowed, isS1EnhancementsAllowed, isTrafficBasedContextReleaseAllowed, vswrUrgentThreshold 20 to 15 è early trigger of alarm, minimumCQIForFSS, connTimer, hARQMaxTimer, initialMCSIndexForBearerSetup, mIMOMode, sctpAccessPathMaxRetrans
  • Closed Loop PC is based on UL level and quality measurements, CELL_PWR_RED, upper and lower thresholds

MOBILITY

• General Causes
  • Path imbalance, connectors, hardware, antenna tilt, serving/neighbor config, discontinuous coverage, parameter settings, interference, cell degraded, PCI collisions,unavailabilities, check equipment health,
• T304 supervises the Intra-LTE HO
• Events
  • A1(stop Inter-freq/Inter-RAT meas due to good quality), A2(start Inter-fre/Inter-RAT meas due to good quality) RRC Connection Release with Redirect, A3(start intra-freq HO due to good neighbor) better cell HO, A4(start inter-freq HO due to good neighbor, B1 (start inter-RAT HO due to good neighbor), A5 coverage HO
    • a3offset (serving) 30 to 40 è discourage HO, timeToTriggerA3 40 to 64, hysteresisA2Sec (neighbor) 10 to 20, hysteresisPm, reportAmountA2Prim 1 to 2 è discourage A2, reportAmountA3, reportIntervalA2Prim MS120 to MS240, reportQuantityA2Prim, timeAndPhaseSynchCritical, x2BlackList, x2retryTimerStart, reportIntervalPm MS_480 to MS_640, removeNcellTime 1 to 2 min, b1ThresholdEcNoUtra, hysteresisA3 3dB, timeToTriggerA3 320 ms, filterCoefficientEUtraRsrp 4, tHODataFwdReordering 300 to 400 ms
  • UE Level Oscillating Handover Minimization feature
• SON
  • AnrSwitch, MroSwitch, TpeSwitch
  • Power Control
  • Reference signal power -57, PCFICH power -3175, PBCH power -3174, Synchronization signals power, -3173, DBCH power -3172, Paging power -3171, Rach respond power, -3170, Prs Power -3169
  • Neighbor-ANR
    • maxReportCellsPm, measurementPriority, cellAddRankLimitEutran, isRemoveAllowed, cellAddRsrpOffsetEutran, cellAddRsrpThresholdEutran, removeNrelTime, ctrlMode, maxMeasInterFreqEUtra, filterCoefficientEUtraRsrq, dlInterferenceManagementActive, anrUesThreshInterFMax, minBestCellHoAttempts 1, x2BlackList, anrIntraFreqState, ANR add cell threshold(%),Fast ANR PCI report amount, FastAnrRsrpThd, Fast ANR checking period, covTriggerdBlindHoAllowed
    • ANR is suggested for early phases
    • anrEnable, isBlindPsHoToUtraFddAllowed
    • Event triggered, Detection of missing neighboring, PCI collisions and abnormal neighboring cell coverage
      • NRTCellHOStatNum no of HOs with N and ANR DelCellThd 60 to 50% è discourage deletion, HOSR with N, FastAnrRprtAmount,
    • Drawbacks, HO delayed, data delay
    • Periodic or Fast, detects only missing neighbor, FastAnrRprtInterval 2048 ms to 1024 ms will speed up the ANR èhigh speed, FastAnrIntraRatMeasUeNum 5 to 7 will improve HOSR. Periodic measurements èincrease power and decrease throughput. FastAnrRsrpThd -102 to -90 è make ANR tough èURBAN
    • Manual configure black and white list, intrFrBCList, intraEnbPrio, statusRepReq, A3 offsets, a3ReportInterval, a3TimeToTrigger, addAUeRrHo, addAUeTcHo, cqiPerNp, dlsUsePartPrb, maxNumAUeHo, p0NomPusch, p0UePusch, pMax, taMaxOffset, threshold1
    • CsfbHoUtranTimeToTrig,
  • HO Parameter-MRO minimizes HO failures, service drops, Early/Drag/Ping-pong by adjusting CIO. Enable during initial phase, MRO (Mobility Robust Optimization) feature optimizes the handover parameters automatically. Deals premature handover, delayed handover, and ping-pong handover. It changes the CIO, NcellOptThd, PingpongTimeThd, PingpongRatioThd 10 to 5 % (to encourage MRO), MRO optimization period(min), Ncell optimization threshold(%)
    • CIO, PingpongTimeThd 5 to 3, PingpongRatioThd 5 to 3 è SON or MRO
    • OptPeriod 1440 to 1300, OptParaThd 70 to 80% HOSRè SON
      • Ealry Hos>Delayed Hos è decrease CIO of neighbor

2. Detect early or late HO

• IRAT HO a2ThresholdRsrpPrim, a2ThresholdRsrpSec, b2Threshold1Rsrp, Uemeasurementsactive, triggerQuantityA2Sec, hysteresisA2Prim, timeToTriggerA2Prim, isForcedDrxForCsFallbackAllowed no to yes, isX2LoadIndicationAllowed, threshold2EutraRsrq 8 (-7,-6.5) to 9 (-10,-9.5) è discourage A5, tReselectionEUTRAN, maxTimeAllowedForCsfbMobilityAttempt
• a3offset 30 to 35 è discourage A3 or adding Intra freq neighbor, a1ThresholdRsrqPm
• pMaxGer, qRxLevMinGer

• KPIs handover success rate, call drop rate, and ping-pong handover rate are set per QCI.
• RACH-PDCCH
• CIO decrease to discourage HO to neighbor. Intra-Frequency CIO(for connected mode), Qoffset in idle mode
• LTE system uses hard handovers
• RRC = connected mode, HO Types, Coverage, Load, service based,
• Measurements gaps=compressed mode, frequency-specific offset 0 to 2 encourages HO
• PBGT HO minBestCellHoAttempts, qOffsetFreq
• Event-Triggered Periodical Reporting Hysteresis, time-to-trigger, filtering coefficient for L3- EutranFilterCoeffRSRP FC0 to FC2 will delay HO, reporting configuration.
• Intra-frequency Handover Out Success Rate
  • Cell group ID is critical
  • In load based, CIO is changed automatically
  • A3 Mn + Ofn + Ocn – Hys > Ms + Ofs + Ocs + Off (IntraFreqHoA3Offset)
    • MeaBandwidth MBW-50 MBW-60, QoffsetFreq, IntraFreqHoA3Offset 2 to 4 will discourage HO, IntraFreqHoA3Hyst 2 to 4(2dB), IntraFreqHoA3TimeToTrig 40 to 60 ms, IntraFreqHoA3TrigQuan, IntraRATHoMaxRprtCell 4 to 6, IntraFreqHoRprtInterval 240 to 480ms, EutranFilterCoeffRSRP FC6 to FC8, IntraRATHoRprtAmount r2 to r4
    • High values for cells with large signal fading variance
  • CellIndividualOffset (Auto) dB-0 to dB-2 will encourage HO
    • Ocs less value will discourage HO
    • Ocn (connected mode) high will encourage HO
  • Retry and Penalty
  • Handover failure è cell selection procedure è RRC connection re-establishment
• Measurement Gaps
  • GapPatternType
    • GAP measurement pattern1 Tperiod 40ms, TGAP 6ms
    • GAP measurement pattern2 Tperiod 80ms, TGAP 6ms
  • RRC connection re-establishment towards the selected cell only
  • Blind HO In the case of a load-based or service-based handover, the eNodeB may select a target cell in the absence of the measurement information, in order to reduce the delay
  • Inter-frequency Handover Out Success Rate
    • A2 Ms + Hys < Thresh
      • InterFreqHoA1A2Hyst 4 to 6(3dB), InterFreqHoA2ThdRSRQ -24(-12dB) to -28(-14dB),
    • A4 Mn + Ofn (QoffsetFreq) + Ocn – Hys > Thresh
      • QoffsetFreq 0 to 3 , InterFreqHoA4Hyst 4 to 6
      • InterFreqHoA1ThdRSRQ -20 to -22, InterFreqLoadBasedHoA4ThdRSRP -103 to -105
      • Timer304 GEAN IRAT timer
    • Load Based
      • Based on frequency capability of UEs, ARPs, and resource usage
    • Handover In Success Rate
    • Inter-RAT Handover Out Success Rate (LTE to CDMA)
    • Inter-RAT Handover Out Success Rate (LTE to WCDMA)
      • InterRatHoA2ThdRSRQ -20 to -22, InterRatHoA1ThdRSRQ -20 to -18, InterRATHoUtranB1ThdEcN0 -20 to -16, LdSvBasedHoGeranB1Thd -98 to -94, UtranFilterCoeffRSCP FC0 to FC2, InterRatHoRprtAmount, InterRatHoGeranRprtInterval
    • T311 10000 to 150000 ms
    • Inter-RAT Handover Out Success Rate (LTE to GSM)
      • GeranFilterCoeff FC0 to FC2
      • T304 ms4000 to ms8000
      • redirectionInfoRefPrio1, OffsetFreq, ThreshXHigh, ThreshXLow, PciConflictAlmSwitch
      • tMobilityFromEutraCCO

INTEGRITY

• ulChBw, redBwMaxRbDl 10 to 15 PRBs Maximum number of PRBs assigned in downlink, tPeriodicBsr 20 to 60s.
• Throughput depends upon
  • Channel environment (e.g. stationary or mobile, speed) and fading conditions.
  • Reception conditions impaired by traffic load levels, and by interference between the cells, in short by the user’s SINR.
  • Network layout, type of antenna.
  • Position of users in the cell (implies e.g. path loss and fading).
  • Restriction of user data rates (e.g. by terminal category)
  • Link sharing weights (Quality of Service (QoS) configuration)
  • Backhaul capacity
  • Troubleshoot Throughput
    • Check alarms
    • Check UE capability
    • Check AMBR of user service
    • Check parameters like dlChannelBandwidth/ redBwMaxRbDl noOfUsedTxAntennas, pZeroNominalPucch, noOfUsedTxAntennas
    • Check Licenses 64-QAM
    • Check Radio IE CQI, MCS, PRBs, Transmission mode,RI, HARQ, RLC retransmisssions, CFI, buffer status, PHR, rxPowerReport, TTI scheduling, RLC discards, tStatusProhibit
    • Check reports from L1 to MAC
    • Check UE variables, ARP,buffer status, PHR report of UE, interference, pZeroNominalPusch of neighbours/serving, Max PRBs allowed
    • Check PDCCH, if CCE are occupied by donwlink grants than UL grants cannot be scheduled
    • QoS profile QCI, priority bit, AMBR, ARP
    • Transport Network
      1. GE link counters (packet delays, errors, re-trans),SCTP, synch, IpInterface
      2. Use wireshark (throughput result and signalling analysis)

• Service Downlink Average Throughput
• Service Uplink Average Throughput
• AQM (automated queue management)-discard large data volume, relieves queue congestion, reduce transmission delay
• ROHC (Robust Header Compression)
• Traffic Volume, no of RBs, MCS coding, usage of PRB (Physical resource blocks), MAC retransmission, no of users/edge users
• CQI 0 to 15, MCS 0 to 31, QC1 (highest) to QC9, RANK 1 to 4, modulation scheme
• RRM, Dynamic Resource Allocation = Scheduling, resources modified are PRBs, Power, PDCCH/PUCCH Resources, TX rank, baseband power, UlBasebandCapacity DlBasebandCapacity
• Common Low Data Rate Issues: TCP/UPD/IP Config, transport network, cable swaps, pmIfInOctetsLink1Hi, CRC errors, RxPower at eNB, GINR on DL, TA, sync
• isLargePdcpSduAllowed, maxNbOfCallCapacityLicensing, sRPeriodicity 10 to 5ms, numberOfPRBsForDynamicallyScheduledPUSCHForCentralRegion 16 to 20, srsBandwidthConfiguration, dlBasicSchedulingMode, dlResourceAllocationType, dlSchedulerMode, expectedNumberOfUEPerTTIForDLRR, maxNumberOfRBsPerUE, nbrUserThrFDS, maximumFSSUsers, operationalMode, pmcMaxResultStringBlockSize, mIMOMode

• Reducing Low CINR impact
  • Resource Block Group Assignments
  • Frequency Selective Scheduling
  • Inter-Cell Interference Coordination (ICIC)
• KPITYPE (alarm)
• Power is distributed along subcarriers, high bandwidth è less power è less coverage
• NAS authentication, service request, connection setup
• MimoAdaptiveParaCfg (Transmission mode fixed 3/adaptive), ECGI, PCI, scheduling recources, LBBP (baseband resources), Qam64Enabled, RachAlgoSwitch, AqmAlgoSwitch (queueing at the cost of integrity), BfAlgoSwitch beamforming algo, DlSchSwitch, DlschStrategy (DLSCH_PRI_TYPE_RR(RR) to DLSCH_PRI_TYPE_MAX_CI(MAX C/I)), UlSchSwitch, BtServiceWeight, PdcchSymNumSwitch, MaxReportCellNum, measBdw, dlTrmBw, ulTrmBw, drbPrioDl, packLoss, resType, ulsBSD, ulsPrio, prio, resType, raLargeMcsUl, PucchRS, dSrTransMax, deltaPreMsg3, deltaTfEnabled, dl64QamEnable, dlCellPwrRed, dlChBw, dlMimoMode, dlRBM, harqMaxTrDl, hopBwPusch, hopModePusch, iniMcsDl, iniPrbsUl, maxBitrateDl, maxNumAUeHo, maxNumUeDl, mbrSelector, mimoOlCqiThD, minBitrateDl, pMax, redBwEnDl, redBwMaxRbDl, redBwRpaEnUl, riEnable, ulChBw, ulTargetBler, ulamcEdgFugEn, ulamcSwitchPer, ulatbEnable, trafficType, rtoMax, qQualMinUtra, qRxLevMinUtra, proportional fair scheduler, Preamble format affects UL throughput, Traffic Marking (transport), PRB, PDSCH power boosting
• More users èservice fair è bit rate,
• Less users è resource fair
• spatial multiplexing and transmit diversity
• Adaptive Transmission bandwidth ulatbEventPer
• preamble sequence subset è uplink resources
• MIMO featureStateDualAntDlPerfPkg, noOfTxAntennas
• The resources managed by the downlink scheduler are downlink Physical Resource Blocks, downlink power, PDCCH capacity and base-band processing capability. The resources managed by the uplink scheduler are block resources for PUSCH, PDCCH, PHICH and base-band processing capacity.
• 100 simultaneous UEs, 8 DRBs max per User, licenseCapacityConnectedUsers, licenseCapacityDlBbCapacity,, number of OFDM symbols for PDCCH
• PUCCH Overdimensioning feature for Rural sites
• DRX introduces extra delay to scheduling EnterDrxSwitch, DrxInactivityTimer, DrxReTxTimer, ShortDrxCycle, FddEnterDrxThd, TrmSwitch, DiscardTimer, UeMaxRetxThreshold, ENodeBMaxRetxThreshold, UlschPriorityFactor, DlMinGbr, PreAllocationWeight, PrioritisedBitRate, LogicalChannelPriority, SriPeriod, UlschPriorityFactor, defPagCyc
• noOfPucchSrUsers 50, nrOfSymbolsPdcch 1, allowedMeasBandwidth, channelBandwidth, noOfPucchSrUsers, noOfRxAntennas, priority, pucchOverdimensioning 0, schedulingStrategy (round robin to strict priority), ulChannelBandwidth, ulMinBitRate, pdb, dscp, dlMinBitRate, resourceAllocationStrategy, dlChannelBandwidth, dlTransNwBandwidth, dlFrequencyAllocationProportion, ulTransNwBandwidth, dlMaxRetxThreshold, mtu, tPollRetransmitDl, rlcMode, dlPollPDU, tReorderingDl, ulMaxRetxThreshold, ulPollPDU, dlMaxHARQTx, priority bit
  • Poor Uplink P0NominalPUSCH -67 to -58 uplink thorughput at the cost of network performance
  • Increase PreambInitRcvTargetPwr, PwrRampingStep èimproved accessibility and throughput

PLANNING

• LINK BUDGET TX Diversity of MIMO, Adaptive array gain, occupied sub-carrier bandwidth, RX diversity Gain, Maximal Ratio Combining (MRC Gain)-requires two antennas and software in UE, HARQ Gains
• Propagation Models Hata upto 1Ghz, Cost-Hata 2Ghz, Greenstien 2 Ghz, Ray Tracing (Dense Urban). Propagation related parameters mean frequency dependent parameters, LTE is interference limited, System gain, also known as the maximum allowable pathloss, use fixed interference/load margin or Monte Carlo simulation
• LTE network poses also similar effects such as network breathing due to UL interference and cell range dependency upon user data rate. PRACH planning is done in LTE. COST model is used by Nokia. Low Tx power for small bandwidth, high Tx power for large bandwidth.
• Ray Trace model for URBAN with vectors provided
• LTE network poses also similar effects such as network breathing due to UL interference and cell range dependency upon user data rate
• DL load as % of total capacity, UL load in terms of interference margin
• MAPL è Signal Strength threshold of Coverage based planning
• Best server areas should be contiguous and should not be fragmented.
• F 5 to 20Mhz è RSRP reduce and RSRQ increases with RSSI being constant

SON

• Self Healing, Optimization, configuration
• Coverage and capacity optimization
• MimoAdaptiveSwitch
• DefDopplerLevel affects all KPIs
• Energy Savings
• Load generator ailgActive, dlPrbLoadLevel, trafficModelPrb
• Interference Reduction, Interference Rejection Combining (IRC)
• Beamforming
• Automated Configuration of Physical Cell Identity
• Mobility robustness optimisation
• Mobility Load balancing optimisation
• Random Access Channel Optimisation
• Automatic Neighbour Relation Function
• ROHC compression feature
• CounterCheckTimer, CounterCheckTimer
• Inter-cell Interference Coordination over X2 interface, ReportInterval, MaxReportCellNum, ReportAmount, TriggerQuantity, Hysteresis, TimeToTrigger, A3Offset
• neighbour cell list optimization
• interference control
• handover parameter optimization
• Quality of Service related parameter optimization
• load balancing
• RACH load optimization
• optimization of home base stations
• Adaptive Transmission bandwidth
• FTP and HTTP are sensitive to end-to-end delay
• Access Stratum b/w UE and eNodeB via RRC
  • RRC idle
  • RRC connected
• Non Access Stratum procedure consists of attach, detach, tracking area update, service request, and extended service request.
  • EMM-DEREGISTERED:
  • EMM-REGISTERED: MME establishes and stores the UE context
  • ECM-IDLE:
  • ECM-CONNECTED: S1 connection is established,
• 3GPP causes ref 24.301
• Random Access Radio Network Temporary Identifier (RA-RNTI)
• Subscriber/Cell/Interface/Cell traffic/terminal/traces
• ROHC (Robust header compression)
• PORTS and TRACE rbsUeTraceEventStreamingPort streamPortPmUeTrace streamStatusPmCellTrace streamStatusPmUeTrace

Internet Protocol

• A class Subnet mask 255.0.0.0/8, less networks (inter) but more Host (intra)
• B class Subnet mask 255.255.0.0/16
• C class Subnet mask 255.255.255.0/24, 255=network address, 0=host address, more networks (inter) but less Hosts (intra)
• Default gateway (eNodeB IP address): 169.254.1.10
• Ping command, tracert, sniffer capture, show route
• SCTP is use for signaling e.g NBAP
• X2 and S1 are using GPRS Tunneling Protocol for User data (GTP-U) to transfer the user plane traffic.
• ICMP reports erros of IP e.g ping, arp
• The process of finding the new next hop after the network changes is called convergence
• 254.x.x IP addresses are self-assigned when your computer can’t get an address any other way. It’s an almost sure sign of a problem
• The Domain Name System (DNS) is used by RBSs to translate host names of other nodes (for example RBSs, MMEs, synchronization servers) to IP addresses
• Registered State
  • PDN,TAU update
• IDLE state
  • No NAS signaling b/w UE and network
• CONNECTED state:
  • RRC b/w UE and eNodeB
  • S1 b/w UE and MME

Ericsson tools

CCR, Nexplorer, Auto-integration, TRUC, LTE troubleshooting WIKI, Moshell/BB/RU commands,

• Moshell, ITK,FlowFox,LTEDecoder,TeRouter/TeViewer,Multimon,uetrace,Japy,scheduling_parser,CDA Web,Hammerhead Web,LTELogTool,TET.pl,decode,LTE Trace Tools, UE Trace Recording (UETR)
• Cell Trace Recording (CTR), mtd-signal trace
• COMMAND LINE MP, RU, Moshell, RRU, BB, AMOS, BCM
• TRACES CPP, baseband LPP, MTD, RDR, RRT, RBS, UE, T&E, HiCap, UE, Cell, CEX, NSD
• LTE torubleshooting wiki
• DUMP configuration report, Dumpcap (network traffic)
• SYSTEM CRASH DUMPS baseband core, Post Mortem.
• LOGS alarm, availability, HW, audit, trace&error, autointegration, board error, event, system, upgrade trace, security, exceptions, trace-error, dump network traffic
• EVENTS RB&UE Trace, EHB, exceptions
• Ericsson Network IQ Reports
• COLI, NCLI,OSS-RC, MicroCPP, ANR, equinox
• PM-initiated UE Measurements
• Layer 3 and S1/X2 (Flowfox, LTEDecoder, scripts), LTELogtool
• LLDM for data rate diagnosis
• Cell Traces are streamed using TCP while UE Traces are streamed using UDP, Iperf, TCP Optimizer, Filezilla (FTP), VLC (Streaming/media), Neoload (Web browsing), wireshark, Element Manager, AMOS,Netpersec(realtime thorughput), Iperf(inject TCP/UDP packets)
• Iperf generates TCP/UDP traffic
• Netpersec monitor thorughput
• MMR = Channel Feedback Report (CFR)
• Nethawk, wireshark (open source), TCP dump, Agilent
• Cell Trace files .ROP
  • te e all Ft_RRC_ASN
  • te e all Ft_S1AP_ASN
  • te e all Ft_X2AP_ASN
  • te e all Ft_LTE_EXCEPTION
  • te e all LTE_EXCEPTION
  • te e all CELL_CONFIG
  • te e all Ft_RRC_CONN_SETUP
  • te e all Ft_ANR_COMMON
• ENIQ ericssons’ tool like Optima
• Moshell commands
  • Teviewer                         to view trace commands
  • Te enable trace
  • Pset UETR trace
  • Diff                         for parameter audit of RNC.zip
  • Moshell rnc7
  • momd . power|pwr //list power control parameters
  • set primarycpichpower
  • pmr get specific KPI
  • pmom                                     get counter
  • lgx, lgo alarm
  • inv check licenses
  • KO UE capability
  • Te e get QCI, AMBR, ARP values
• COLI commands are for trouble shooting
• L12 features, RoHC, 4-way receive diversity, service based HO, System info-9 tunneling, preempt low priority users, oscillating HO minimization

NSN tools

• TTI Trace, Emil, LTE browser, BTS-Log, RF Unit console, Memory Dumper

KPIs

• Delay
• Delay Variation
• Latency, throughput, packet drop, Packet Loss
• Availability
• Service Access time is a Latency KPI

• Event A1: Serving becomes better than absolute threshold;
• Event A2: Serving becomes worse than absolute threshold;
• Event A3: Neighbor becomes amount of offset better than serving;
• Event A4: Neighbor becomes better than absolute threshold; Inter-Freq
• Event A5: Serving becomes worse than absolute threshold1 AND Neighbor becomes better than another absolute threshold2.
• Event B1 Inter-RAT neighbor becomes better than threshold
• Event B2 Inter-RAT neighbor becomes better than threshold and serving becomes worse than threshold

• The RRCConnectionReconfiguration message is the command to modify an RRC connection. It may convey information for measurement configuration, mobility control, radio resource configuration (including RBs, MAC main configuration and physical channel configuration) including any associated dedicated NAS information and security configuration.
• PDCP: integrity protection and ciphering;
• RLC: reliable and in-sequence transfer of information
• RSSI = wideband power= noise + serving cell power + interference power
• RSRP (dBm)= RSSI (dBm) -10*log (12*N), high BW è less RSRP
  • Value 00 (-140) to 97 (-44), step 1
  • Independent of load
• RSRQ = N x RSRP / RSSI, high BW
  • Value 00 (-19.5) to Value 34 (-3), step .5
  • Dependent on load
• RSRQ -3 to -19, RSRP -140 to -44
  • RSRQ=RSRP/(RSSI/N) = RSRP*N/(IN_n + ρ*12*N*Psc) and
  • SINR=S/(IN_m)
• SNR -15 to 40
• CINR=RSRQ
• UE estimates SINR based on the Power Spectral Density of the downlink RS and PSD offset between PDSCH and RS. The SINR is Channel Quality Indicator (CQI).
• UE will report lower CQI values when using MIMO as opposed to SIMO in same RF environment (SINR), UE will typically use lower Modulation/MCS
• CQI 0 to 15, MCS 0 to 28
• CINR -25 to 40dB
• RSRP -150 to -30
• RSSI -120 to 0
• UE PRACH TX Power -10 to 23 dBm
• RSRQ 0 to -40
• BLER 0 to 100% tolerable till 10%
• FER 0 to 100%
• UE categories 1(low) to highest(5)
• Transmission modes Mode 1 to 9 (highest), open/closed loop, antenna ports, MIMO (tm3) vs. TxD (tm2) vs. SIMO (tm1)
• GINR Gain to interference and Noise Ratio
• A UE is said to be ‘in session’ if any data on a DRB (UL or DL) has been transferred during the last 100 ms
• PHR (power headroom report).
• PSD è SINR èCQI Channel Feedback Report (CFR) ètransport format. RI i suded with MIMO
• link quality (SINR, BLER, HARQ OPP)è MCS and coding rate èTBS

eNodeB Hardware

• D2U V2 (1 uCCM + 3 eCEM)
• TRDU (remote-radio-heads comprising of amplifiers and filters), 40W Tx power

DT Performance Metrics

• Air Interface
  • UE Tx power
  • RSSI
  • SINR
  • BLER
  • Retransmission statistics (HARQ and RLC)
  • Transport Format
  • Number of resource blocks (DL/UL)
  • Channel rank statistics
  • MIMO mode (Tx diversity or Spatial Multiplexing)
  • Serving sector
  • Location (GPS)
  • UE Velocity
• Throughput
  • Individual user throughput and aggregated sector throughput
  • UDP individual user throughput and aggregated sector throughput
  • TCP individual user throughput and aggregated sector throughput
  • User statistics (peak rates, average rates, standard deviations)
  • 
    
• Latency
  • U-plane latency
  • Connection set up times
  • Handover interruption time within the same site and across different sites
• Open loop PC is based on path loss, broadcasted/RRC parameters
• Closed Loop PC is based on UL level and quality measurements
• The power per subcarrier will be higher in smaller bandwidths è downlink coverage will be higher for smaller bandwidths than for larger ones
• Downlink AMC/fast AMC, SINRè CQI è modulation and coding scheme, per TTI, scheduling, Uplink AMC/ slow AMC, SRS, BLER è modulation and coding scheme, scheduling, Emergency Downgrade, Fast Upgrade’
• Current BLER and Target BLERè CQI offset
• PESQ 4 (best) to 1(worst)
• SFN=system frame numer, 10ms, 0 to 1024
• Sub-frame number, 1ms, 0 to 9
• Paging Occasion = System and sub frame number
• SFNmode 4 è 40 ms
• THE UE reads P-SS and S-SS every 5ms to stay in synch. If UE successfully detected Cell ID/PCI, it means UE successfully completed the time-sync.
• Network not detected but signal bars are there èRACH error
• There are 64 PRACH sequences. Same PRACH preamble from multiple UE reaches the NW at the same time. This kind of PRACH collision is called “Contention”
• Preamble format 0-4
• Precoding matrix 0-3. Related to MIMO
• PDCCH format 0-3
• Failure to decode SIB2 by the UE, will affect PRACH process
• PMI precoding matrix indication, (codebook index,no.of layers) Table 6.3.4.2.3-2, 36.211, reported in case of TM=4
• Transmission mode 1-7
• PDCCH format 0(1)-3(8 CCEs)
• T is the DRX cycle or defaultPagingCycle
• QCI 1(Highest) to 9(Lowest)
• RRC Connection Reconfiguration for measurement configuration, handover/mobility control, radio resource configuration (RBs, MAC, physical channel), dedicated NAS information and security configuration
• RACH procedure initial access, handover, RRC recon estb, Sync loss in RRC connected mode
• RBs/BW 25/5Mhz, 50/10, 75/15, 100/20
• RRS Re-estb after UE tirggered RF failure, HO failure, RRC re-config failure
• For RSRP: RSRP based threshold for event evaluation. The actual value is IE value – 140 dBm.
• For RSRQ: RSRQ based threshold for event evaluation. The actual value is (IE value – 40)/2 dB.
• RSRQ_00 = RSRQ < -19.5, RSRQ_34= -3 £ RSRQ 36.133
• PH Power headroom , is defined as the difference between the nominal UE maximum transmit power and the estimated power for PUSCH transmission PH_0= -23 £ PH < -22 & PH_62 = 39 £ PH < Low value index means UE has limited power. To transmit more PRBs, more power is required
• EMM = EPS mobility management, timers ref: 10.2, 24.301
• ESM = EPS session management, bearer assignment, timers ref: 10.3, 24.301
• TA 0,1(156m) ,………1282 (200km)
• RRC function SIB, RRC, connection, handover, paging, security message, NAS messages, selection/reselection
• CFI no. of scheduling bits, (number of OFDM symbols for PDCCH) vs. MCS vs. % scheduling HARQ
• TM Transmission mode 1-7, 7.2.3-0 36.213
• CQI 0 to 15, MCS 0 to 31, QC1 to QC9, RANK 1 to 4
  • WCQI, wide-band CQI reported periodically
  • SCQI, sub-band CQI, reported aperiodically on request from enodeb, 1(worst) to 7(best)
• RI Rank indicator, UE reports that info has been decoded from how many antennas, 2/4 layer spatial multiplexing 7.2.3-1 36.213,
• Assignable bits means the amount of data in the downlink buffer available for the scheduler to schedule for this UE.
• RLC DISCARDs will trigger TCP congestion control and lower throughput
• BSR buffer status report 0(0KB) to 64 (15KB), power headroom report
• Interference power > -104dBm
• Link adaptation considers PHR, recived power of UE and UL interference power
• QoS profile QCI, priority bit, AMBR, ARP
• DSCP differentiated servise code point. QCI is mapped to DSCP
• GTPU, GPRS tunneling protocol
• DCI Downlink scheduling control indicator, channel coding formats, which resource block carries your data, power control, transport format,HARQ, L1 signaling, DCI format 1, 1A, 1B, 1C, 1D, 2 or 2A
• UCI Uplink scheduling control indicator, it contains, SR, Ack/Nack, CQI. Transmistted in PUSCH is there is data and on PUCCH otherwise.
• Resource Indication Value (RIV),that informs the device which RB to use and which start offset to apply.
• Hopping bits are
  • Type1 00,01,10, follows one pattern only
  • Type2 11 random based on subband, offset and mirror function. Unique to the cell
• PDCCH format 0(low capacity) to 3(high signaling capacity)
• DL Scheduling of RBs is determined TYPE & DCI format
  • TYPE 0 to 2
  • DCI format 0,1A,1B,1C,2,3,3A
• RB assignment is carried in RIV (resource indication value)
• RB= 1 slot x 12 carriers, resource block
• RGB = 4 RBs or 48 carriers
• If 20Mhz, 100 RBs and 25 RGBs
• RGB subset 0,1,2,3
• 1 RE = 1 carrier x symbol
• I REG=4 RE
• g. 1CCE = 9 REGs or 36 REs, 72 bits if REG-8bits
• 1, 2, 4 or 8 CCE(s) (1 CCE = 9 REGs = 9*4 REs = 72 bits
• Aggregation Level – a group of ‘L’ CCEs. (L can be 1,2,4,8)
• In order to get the assigned RB resources (and the location) in PDSCH, DCI bits and format TYPE has to be decoded
• 29 MSC schemes sector capacity is approximated by the harmonic mean of the MPR distribution
• LTE smart antenna arrays focuses the beam towards the user
• ARP allocation and retention priority. This determines if bearer can be dropped if congestions occurs, or it cause other bearers to be dropped
• C-RNTI, P-RNTI (Paging UE identifier), RA-RNTI(RACH), SI-RNTI(System information)
• TPC 0(-6dB) to 7(8dB) è DCI format0/3
• PUSCH channel TPC 0(-4dB) to 3(4dB) è DCI format0/3 + TPC-PUSCH-C-RNTI
• PUCCH channel TPC 0(-1dB) to 3(3dB) è DCI format0/3 + TPC-PUSCH-C-RNTI
• PDSCH Power is determined in the following manner
  • If RS is not present in the RB of PDSCH, offset from RS power is defined by Pa, which is UE specific offset. Pa is signaled by higher layers and is changes every 1ms, values are -6 to 3 dB.
  • If RS is present then Pb and antennaPortsCount together will determine the offset. It is cell specific and changes only when there is change in system message e.g if antennaPortsCount=1 and Pb=2 then Offset = -2.218
• Tranmist diversity same stream sent on diff antennas
• Spatial diversity means diff stream on diff antennas
• Cyclic Delay Diversity (CDD) Addition of antenna specific cyclic shifts
• Fast Power control is per slot
• Pcmax = min(p-Max,Pumax), Pcmax is max UE power
  • p-Max 23 dBm
  • PuMax
    • MPR (max power reduction) table 6.2.4-1 36.101
      • additionalSpectrumEmission =1 them MPR =0dB
    • RIV resource indication values indicates the starting position and number of RBs assigned. It is given in DCI-0
    • Assigned PRBs in layer3
      • In order to save signaling bits on the downlink control channel (physical downlink control channel, PDCCH), these two parameters are not explicitly signaled. Instead, a resource indication value (RIV)is derived which is signaled in the downlink control information on the PDCCH.
    • Alpha range 0,0.4,0.5,0.6,0.7,0.8,0.9,1.0. It is used as path loss compensation factor as a trade-off between total uplink capacity and cell edge-data rate. Higher value will be good for cell edge user but not for the overall capacity due to high uplink power
    • Short and Long DRX cycles are configured to trade off battery saving and latency
    • PBR prioritized bit rate
    • timeAlignmentTimer
    • RBG a group of radio bearer with similar QoS requirements
    • SRS uplink scheduling, BSR, PHR. SRS is uplink counterpart of CQI report for downlink scheduling
    • Cylic shifts and sub-carrier offsets and used to define transmission combs for UEs or in other words schedule reference signals of UE, cell edge user cannot use
    • srs-BandwidthConfig range 0(high bw) to 7 (Low bw)
    • srs-Bandwidth range 0 (whole band) to 3 narrowest band
    • Scheduling techniques
      • In dynamic scheduling, the resources are distributed in 1 ms intervals. Quick link adaptation
      • In persistent scheduling, longer transmission period is allocated for user with the one grant. Poor link adaptation, fixed resources TB
    • RB Power is the power of 1 RB
    • TX Power is the power of all assigned RBs
    • TTI is subframe=1msec
    • A cyclic shift in the time domain (post IFFT in the OFDM modulation) is equivalent to a phase rotation in the frequency domain (pre-IFFT in the OFDM modulation).
    • Common SRS is also called Cell Specific SRS and Dedicated SRS is also called UE Specific SRS.
    • MAC CE, MAC control info
    • 1 PDCCH = 8 DCIs
    • PDCCH
      • Carries common control info RACH response, Broadcast, SIB, paging, UL TPC
      • Dedicated control info
        • Uplink scheduling information (DCI format 0)
        • Downlink scheduling information (DCI format 1/1A/1B/2/2A)
        • PUSCH/PUCCH TPC commands (DCI format 3/3A)