A comprehensive presentation on LTE KPI optimization and detailed techniques for improvement

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2. RRC SR%
E-RAB Setup SR%
CSFB SR%
E-RAB Drop%
DL Traffic Volume(GB)
DL Cell Throughput
LTE KPIs

3. • The RRC setup procedure is trigged by different reasons as identified by the EstablishmentCause field in the RRCConnctionRequest
message: Emergency , HighPriorityAccess , Mt-Access , Mo-Signaling
RRC Setup Success Rate = { L.RRC.ConnReq.Succ / L.RRC.ConnReq.Att } * 100
RRC SR%

4. RRC SR%: Reason of failure
The symptoms of an RRC connection setup failure on the eNB are as follows:
 After delivering the RRC Connection Setup message, the eNB fails to receive the RRC Connection Setup Complete
message.
 The eNB sends the RRC Connection Reject message to indicate that the eNB is faulty.
The reasons of RRC connection failure are composed of three families:
1. Resoure Family
2. Reject Family
3. No Reply Family

5. RRC SR%: Reason of failure
1. Resource Family
The number of RRC connection failures due to resource allocation failures, they are summed up into:
 PUCCH resource failures due to the full capacity of the channel.(Physical Uplink Common Channel)
 SRS”Sounding Reference Signal” : the eNB cannot estimate the UL channel quality and cannot proceed an UL
frequency selective scheduling.(Channel that carry the reference signal)
 User Specification: each cell carries 600 RRC connected UE (limitation of UE Number).
 RRC IDLE: for all users so we have no limitation for RRC number
 RRC CONNECTED: the maximum number of users who can camp on the cell is 600, which means for example the user
number 601 cannot access to the cell.

6. RRC SR%: Reason of failure
2. Reject Family
As mentioned before, the eNB will send RRC Connection Reject message if it fails to receive the RRC Connection
Setup Complete message. The RRC connection reject message due to:
 Flow Control: UE sends data (out of standard) that the eNB cannot understand.
Theoretically, the UE must transmit the packets by respecting the same data rates adapted by the eNB.
 Forbidden Acknowledgement: The UE is located at a distance greater than the cell radius.
 MME overload.

7. RRC SR%: Reason of failure
3. No Reply Family
We are exposed to have a failure in RRC connection setup due to bad radio condition. The UE cannot hear the RRC
Connection Setup Complete message because of site overshooting or the site depends only on RSRP without taking into
consideration the quality of the site (RSRQ).
To avoid all these problems, we have to set timers that control the waiting time of RRC Connection Setup Complete and set
a threshold for the UEs trying to access the network and if they exceed this threshold they must wait a certain time before
reestablishing the connection. We can also decrease the transmitted power if the site overshoots. Moreover, we can check
the IDLE Mode parameters (Cell Selection and Cell Reselection to avoid RRC connection failures.

8. RRC SR% : Counters name and description
Counter Name Counter Description
L.RRC.SetupFail.ResFail No.of RRC Connection Failures Due to Resource Allocation Failures
L.RRC.SetupFail.ResFail.PUCCH No.of RRC Connection Failures Due to PUCCH Resource Allocation Failures
L.RRC.SetupFail.ResFail.SRS No.of RRC Connection Failures Due to sounding reference signal Resource Allocation Failures
L.RRC.SetupFail.ResFail.UserSpec No.of RRC Connection Failures Due to Limitation of UE Number Specification
L.RRC.SetupFail.ResFail.Other No.of RRC Connection Failures Due to Other Resource Allocation Failures
L.RRC.SetupFail.Rej No.of RRC Connection Reject messages Sent to UEs in a Cell
L.RRC.SetupFail.Rej.FlowCtrl No.of RRC Connection Reject Due to Flow Control
L.RRC.SetupFail.Rej.ForbidAc No.of RRC Connection Reject Due to the Distance between UEs Access the Cell Out of the Coverage Area
L.RRC.SetupFail.Rej.MMEOverload No.of RRC Connection Reject Due to MME Overload
L.RRC.SetupFail.Rej.Other No.of RRC Connection Reject Due to Other Causes
L.RRC.SetupFail.NoReply No.of RRC Connection Failures Due to No Responses from UE

9. The EnodeB is started T300 when the UE sends RRCConnectionRequest and end when UE received the RRC
RRCConnectionSetup or RRCConnectionReject . Change From 1000ms to 1500ms. LST UETIMERCONST
RRC SR%: Recommended Actions
 Check alarms.(H/W , TX)
• VSWR alarm.
• RF unit maintenance alarm.
• Cell Unavailable.
• RF out of service.
• CPRI or BBU alarms.
 Check TA.
 Check S1 availability.
 Check NBRs.
Start T300 Timer
and Stop if UE
receive
RRCConnectionSetu
p or
RRCConnectionReje
ct
Start RRC
Connection
Setup Complete
Waiting Timer

10. RRC SR% :Recommended Actions
Timer is Started from eNodeB at RRC Setup and end at RRC Connection Setup
Complete(Indicates the timer for the eNodeB to wait for a RRC Connection Setup
Complete). Change to 15s. LST ENODEBCONNSTATETIMER
If Cell is Suffering from Overshooting Problem we Should Decrease Power.
LST PDSCHCFG to get RS and PB
LST CELLDLPCPDSCHPA to get PA
LST CELLSEL and LST CELLRESEL
Timer that is started after UE finished all his trials of retrying to make RRC Request and all Fail(UE has to wait
a certain time T302 to initiate a request again).Change From 4s to 16s. LST RRCCONNSTATETIMER
Indicates the number of trials that UE can retry to make RRC Request(threshold for an RRC
connection penalty). Change From 10 to 5.
LST GLOBALPROCSWITCH

11. RRC SR%

12. RRC SR% : Idle Mode
SrxLev = QrxLevMeas – ( QrxLevMin + QrxLevMinOffset ) - Pcompensation
Squal = QqualMeas – ( QqualMin + QqualMinOffset )
 SrxLev > 0
 Squal > 0
Measurement
• SrxLev = QrxLevMin + S-IntraSearch Or S-NonIntraSearch
• Squal = QqualMin + S-IntraQ Or S-NonIntraQ
Rank
• R_n = Qmeas_n – CellQOffset
• R_s = Qmeas_s + CellQHyst
Trigger
• Same Priority Mn – CellQoffset - QoffsetFreq > Ms + Qhyst
• High Priority Mn > Qrxlevmin + ThreshXHigh
• Low Priority Ms < Qrxlevmin + ThrshServLow & Mn > Qrxlevmin + ThreshXLow
QrxLevMin , QrxLevMinOffset , QqualMin , QqualMinOffset LST CELLSEL
QrxLevMin , SIntraSearch ,
SNonIntraSearch , QqualMin , SIntraQ
, SNonIntraQ LST CELLRESEL
CellQOffset LST EUTRANINTRAFREQNCNCELL
CellQHyst LST CELLRESEL
ThreshXHigh , ThreshXLow
LST EUTRANINTERFREQ

13. • E RAB Setup Success Rate = { L.E-RAB.SuccEst / L.E-RAB.Att Est } * 100
E-RAB Setup SR%
• This KPI can be used to evaluate the ERAB setup success rate of all services in a cell or a cluster.
• The E-RAB Setup Success rate in a cell directly represents a capability of the cell to provide E-RAB Connection Setup for Users.
carried on
SRB 0
carried on
SRB 1
carried on
SRB 2 , DRB
Setup
To Transfer
First UL
NAS
Message
To Know UE
Capability , QCI ,
Max Throughput ,
Security Context

14. E RAB Setup SR%: Reason of failure
The reasons of ERAB setup failure are summed up:
 No Reply and MME : The UE is located in bad radio conditions (UE doesn’t hear the message)
 TNL: Transmission Problem(Problem over Transport layer).
 RNL: Radio Problem(Problem over Radio Network layer).
 Insufficient PUCCH resources
 SRS Problem: the eNB cannot estimate the UL channel quality and cannot proceed an UL frequency selective
scheduling
 X2 AP: ERAB request and HO request are sent at the same time so we will have HO failure.
 Security mode Failure: Failures Due to Security Mode Configuration Failures
 SRBReset: RLC PDU(Packet data unit) for an SRB has been retransmitted for the MAX No.of Times

15. E-RAB Setup SR% : Counters name and description
Counter Name Counter Description
L.E-RAB.FailEst.NoReply No.of E-RAB Setup Failures Due to no Responses from the UE
L.E-RAB.FailEst.MME No.of E-RAB Setup Failures Triggered by the MME
L.E-RAB.FailEst.TNL No.of E-RAB Setup Failures Due to Faults at the Transport Network Layer
L.E-RAB.FailEst.RNL No.of E-RAB Setup Failures Due to Faults at the Radio Network Layer
L.E-RAB.FailEst.NoRadioRes No.of E-RAB Setup Failures Due to Insufficient radio resources
L.E-RAB.FailEst.NoRadioRes.SRS No.of E-RAB Setup Failures Due to Insufficient SRS resources
L.E-RAB.FailEst.NoRadioRes.PUCCH No.of E-RAB Setup Failures Due to Insufficient PUCCH resources
L.E-RAB.FailEst.SecurModeFail No.of E-RAB Setup Failures Due to Security Mode Configuration Failures
L.E-RAB.FailEst.SRBReset No.of E-RAB Setup Failures because RLC PDU for an SRB has been retransmitted for the MAX No.of Times
L.E-RAB.FailEst.X2AP No.of E-RAB Setup Failures Due to Conflict s with X2AP Related Procedures

16. E RAB Setup SR%: Recommended Actions
 Check alarms.(H/W , TX)
• VSWR alarm.
• RF unit maintenance alarm.
• Cell Unavailable.
• RF out of service.
• CPRI or BBU alarms.
 Check TA.
 Check S1 availability.
 Check NBRs.
LST CELLRESEL
Change Threshold for non intra freq measurements(2dB) from 5 to 10
Change Threshold for intra freq measurements(2dB) from 25 to 30

17. E RAB Setup SR%: Recommended Actions
If Cell is Suffering from Overshooting Problem we Should Decrease Power.
LST PDSCHCFG to get RS and PB
LST CELLDLPCPDSCHPA to get PA
LST CELLSEL and LST CELLRESEL
If this parameter is set to a small value, excessive polling PDUs are sent. In addition, the
number of ARQ retransmissions reaches its maximum due to consecutive PDU
retransmissions, and therefore the RRC connection is reestablished. If this parameter is set to
a large value, status reports cannot be sent promptly Change From 40ms to 100ms.
LST SRBRLCPDCPCFG & LST RLCPDCPPARAGROUP

18. CSFB SR%
One of the major design choices of LTE was to focus on the development of a packet-based core and access
network infrastructure. The circuit-switched core network and dedicated telephony features of GSM and
UMTS radio access networks have not been adapted for LTE. This design reduces the overall complexity of
the network. Here, a clear trend toward IP and voice services over IP is well ongoing in Egypt. But we have
to offer traditional circuit-switched services over an IP connection (in case of not using the VoIP services)
because for a user, it should be invisible if the service is offered over the circuit-switched part of the GSM or
UMTS network or the packet-switched IP-based LTE network. Also, .should be seamlessly handed over to
GSM or UMTS if the user leaves the LTE coverage area. In other words, the IP-based voice call must be
converted to a circuit-switched voice call on the fly as otherwise the overall user experience will be
unsatisfactory. So we implement the CSFB solution to meet this criterion. The SGs interface can be used to
deliver paging messages that inform the mobile device of an incoming call. The call itself, however, is not
delivered over the LTE interface and the UE has to fall back to a GSM or UMTS network where a circuit-
switched connection is then established for the call. This method of delivering voice calls is therefore
referred to as CS (circuit-switched) fallback and is executed as follows.
Circuit Switch Fallback

19. CSFB SR%
Check UTRANNFREQ : to make sure that 3G bands (Downlink Frequency) added.
• F1: 10762
• F2:10787
• M1:3087
• M2: 3066
Check UCELL Over 3G Site.
Check UTRANNCELL: to make sure that External NBR sites added.
Check UTRANRANSHARE: to make sure that Co-site added
Check UTRANGERAN: to check 2G
Circuit Switch Fallback

20. CSFB SR% : UTRANNFREQ/UCell
Make sure that Frequency Priority for
Connected mode = 6

21. CSFB SR% : UTRANRANSHARE

22. CSFB SR% : UTRANNCELL

23. • E-RAB Drop = { L.E-RAB.AbnormRel / L.E-RAB.Rel } * 100
E-RAB Drop%
• This KPI can be used to evaluate the call drop rate of all services in a cell or a cluster.
• MME Send E-RAB Normal Or Abnormal Release based on the Causes.
• Normal Release for Detach , User Inactivity , CSFB , Om-Intervention , HO , IRAT Redirection.
Normal and
Abnormal
Release
Counters based
on the Causes

24. E RAB Drop%: Reason of failure
The reasons of Call Drop are summed up as follows:
 Radio Problems: If abnormal releases are counted into ERAB.AbnormRel.Radio counter, the call drop is caused by the radio
interface problem on the wireless network side.
 DRB: the DRB cannot carry data packets
 SRB: the SRB cannot carry signaling messages.
 UL Synchronization: there is no synchronization between eNB and UE.
 No Reply: the UE doesn’t hear the message
A call drop with the cause value being radio is caused by the reason that the RLC retransmissions reach the maximum timer,
out of synchronization occurs or signaling messages exchange fails due to weak coverage, UL interference or UE faults
 Handover Problems: a call drop with cause value being handover failure is caused by an abnormal release due to a failure in
handover out of the serving cell.
 Transport Problems: Call drops can be caused by transport layer problems, transmission problem between the eNB and the
MME (disrupted S1 Link).
 Congestion Problems: congestion of radio resources (Shortage) on the eNB for example max number of active UE is reached.
We can offload traffic from the serving cell to its neighbors.
 MME Problems: A call drop is caused by an abnormal release initiated by the EPC.

25. E-RAB Drop%:Counters name and description
Counter Name Counter Description
L.E-RAB.AbnormRel No.of Abnormal Release
L.E-RAB.AbnormRel.Cong No.of Abnormal Release Due to Congestion
L.E-RAB.AbnormRel.eNBTot No.of Abnormal Release at enodeb
L.E-RAB.AbnormRel.HOFailure No.of Abnormal Release Due to HO Failure
L.E-RAB.AbnormRel.HOOut No.of Abnormal Release Due to HOOut (UE Success to make HO but eNodeb Consider it Abnormal)
L.E-RAB.AbnormRel.MME No.of MME Triggered Abnormal Release of Activated E-RABs “ Different Mechanism “
L.E-RAB.AbnormRel.Radio No.of Abnormal Release Due to Radio
L.E-RAB.AbnormRel.Radio.DRBReset No.of Abnormal Release because RLC PDU for an DRB has been retransmitted for the MAX No.of
Times
L.E-RAB.AbnormRel.Radio.SRBReset No.of Abnormal Release because RLC PDU for an SRB has been retransmitted for the MAX No.of
Times
L.E-RAB.AbnormRel.Radio.ULSyncFail No.of Abnormal Release Due to ULSyncFail between UE and enodeB
L.E-RAB.AbnormRel.Radio.UuNoReply No.of Abnormal Release Due to No Response from UE
L.E-RAB.AbnormRel.TNL No.of Abnormal Release Due to Faults at the Transport Network Layer

26. If this parameter is set to a small value, excessive polling PDUs are sent. In addition, the
number of ARQ retransmissions reaches its maximum due to consecutive PDU
retransmissions, and therefore the RRC connection is reestablished. If this parameter is set to
a large value, status reports cannot be sent promptly Change From 40ms to 100ms.
LST SRBRLCPDCPCFG & LST RLCPDCPPARAGROUP
A smaller value of this parameter results in a higher probability that UEs enter the out-of-synchronization state
when they should not and, therefore, a larger number of random access procedures triggered for maintaining
uplink synchronization and more occupied resources for random access. A larger value of this parameter
results in fewer prompt changes of UE status from uplink-synchronized to out-of-synchronization, more power
consumption of UEs, and more occupied PUCCH and SRS resources Change From 180ms to 300ms.
LST RRCCONNSTATETIMER
E-RAB Drop%: Recommended actions
Indicates the trigger quantity of inter-RAT events A1 and A2. Change From RSRP to BOTH.
LST INTERRATHOCOMM
Change RSRQ value InterRatHoA1ThdRsrq & InterRatHoA2ThdRsrq
LST INTERRATHOCOMMGROUP
N310 : Indicates the maximum number of successive "out of sync“
N311 : Indicates the maximum number of successive "in sync“ LST UETIMERCONST

27. E-RAB Drop%
DRX Trial InterRAT Trial

28. Cell DL Average Throughput (Mbps) = [L.Thrp.bits.DL]*1000/(1000*1000*[L.Thrp.Time.Cell.DL.HighPrecision])
DL Cell Throughput
Downlink Throughput
Calculation
• 1 Radio Frame = 10 Sub-Frame
• 1 Sub-frame = 2 Time-slots
• 1 Time-slot = 0.5 ms (i.e 1 Sub-frame = 1 ms)
• 1 Time-slot = 7 Modulation Symbols (when normal CP length is used)
• 1 Modulation Symbols = 6 bits; if 64 QAM is used as modulation scheme
Radio resource is manage in LTE as resource grid
- 1 Resource Block (RB) = 12 Sub-carriers
 Assume 10 MHz channel bandwidth (50 RBs), normal CP
Therefore, number of bits in a sub-frame = 50RBs x 12 sub-carriers x 2 slots x 7
modulation symbols x 6 bits = 50400 bits
 Hence, data rate = 50400 bits / 1 ms = 50.4 Mbps
 If 2x2 MIMO is used, then the peak data rate would be 2 x 50.4 Mbps = 100.8 Mbps.
 If 3/4 coding is used to protect the data, we still get 0.75 x 100 Mbps = 75 Mbps as
data rate.

29. DL Cell Throughput
Parameter id Parameter name Setting Discription
dlbandwidth DOWNLINK BANDWIDTH
Meaning: Indicates the DL bandwidth of the cell, which is based on the number of resource blocks (RBs). The value
CELL_BW_N25 indicates a cell bandwidth of 25 RBs. The value CELL_BW_N50 indicates a cell bandwidth of 50 RBs.
LST CELL
ulbandwidth UPLINK BANDWIDTH
Meaning: Indicates the UL bandwidth of the cell, which is based on the number of resource blocks (RBs). The value
CELL_BW_N25 indicates a cell bandwidth of 25 RBs. The value CELL_BW_N50 indicates a cell bandwidth of 50 RBs.
LST CELL
txrxmode
CELL TRANSMISSION
AND RECEPTION MODE
Meaning: Indicates the transmission and reception mode of the cell i.e MIMO configuration of cell GUI Value Range:
1T1R, 1T2R, 2T2R, 2T4R, 4T4R, 8T8R
LST CELL
InitPdcchSymNum
PDCCH Initial Symbol
Number
If the parameter value is too small, the cell supports dynamic adjustment on the number of OFDM symbols occupied by
the PDCCH but may impact the downlink throughput. If the parameter value is too large, the cell does not support
dynamic adjustment of the number of OFDM symbols occupied by the PDCCH, which impacts the downlink throughput.
LST CELLPDCCHALGO
dlcyclicprefix
DOWNLINK CYCLIC
PREFIX LENGTH
Meaning: Indicates the length of the DL cyclic prefix of a cell. A DL cyclic prefix can be a common or extended cyclic
prefix. An extended cyclic prefix is generally used in a complex environment with a strong multi-path effect and long
delay. Recommended Value: Normal CP
LST CELL
P0NominalPUCCH P0 nominal PUCCH
Meaning: Indicates the target UE transmit power for the PUCCH expected by the eNodeB on condition that normal
demodulation can be performed. Impact on Radio Network Performance: If this parameter value is too large, the
interference to neighboring cells increases and the overall network throughput decreases. If this parameter value is too
small, the interference to neighboring cells decreases and the throughput of the local cell also decreases.
LST CELLULPCCOMM
P0NominalPUSCH P0 nominal PUSCH
Meaning: Indicates the nominal P0 value of the PUSCH. It is used in UL power control. Impact on Radio Network
Performance: If this parameter value is too large, the interference to neighboring cells increases and the overall network
throughput decreases. If this parameter value is too small, the interference to neighboring cells decreases and the
throughput of the local cell also decreases
LST CELLULPCCOMM

30. DL Cell Throughput
• Incorrect CPRI Interface Configuration
• CPRI Bandwidth Not enough
• RF Unit VSWR Threshold Crossed
The eNB needs knowledge of the SINR conditions of downlink transmission to a UE in order to select the
most efficient MCS/PRB combination for a selected UE at any point in time.
Channel Quality Index (CQI):
 Is a feedback mechanism from UE to eNB.
 Informs eNB of current channel conditions as seen at UE.
 CQI 1-6 map to QPSK
 CQI 7-9 map to 16QAM
 CQI 10-15 map to 64QAM
Rank Indicator (RI)
 Is a feedback mechanism from UE to eNB.
 Informs eNB whether UE can successfully decode RS from 1 or 2 (or more) antennas.
 Rank 1: Tx Diversity (transmission mode 2, tm2).
 Rank 2: MIMO (Open Loop Spatial Multiplexing (transmission mode 3, tm3).
PCI Clashes
If we have UL Interference

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