LTE Troubleshooting / Optimization Guidelines

Sprint 4G LTE Troubleshooting

and Optimization Guidelines
Document Version 2.0

4G National RF Engineering

The information contained in this document is proprietary and

confidential to Sprint and is intended solely for internal use by Sprint
employees. Any unauthorized distribution of this information without
the written consent of Sprint is strictly prohibited.

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Revisions and Contributions

Organization
Network Engineering
Network Engineering (Dir)
Network Engineering (Mgr)

Author
Geof
Lubeskie
Geof
Lubeskie

Version
1.0
2.0

Name
Greg OConnor
Hui-Lin Chang
Rashmi Kumar

Date
November
2013

E-mail Address
Geof.Lubeskie@sprint.c
om

January
2013

Geof.Lubeskie@sprint.c
om

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Table of Contents
1

General.........................................................................................................................
1.1
1.2
1.3

LTE Optimization Process Flows...........................................................................

2.1
2.2
2.3

Cell Selection Process...................................................................................................................9

Cell Selection Criteria...................................................................................................................9
Cell Reselection..........................................................................................................................10

Interference Control...............................................................................................12
LTE Handoff Optimization....................................................................................13
6.1
6.2

7
8

RSRP.............................................................................................................................................8
SINR..............................................................................................................................................8

Cell Selection..............................................................................................................
4.1
4.2
4.3

5
6

Site Level Optimization........................................................................................................5

Cluster Level Optimization..................................................................................................6
Market level Optimization...................................................................................................7

RF Conditions.............................................................................................................
3.1
3.2

Purpose.......................................................................................................................................4
Responsibility...........................................................................................................................4
Revision History......................................................................................................................4

Active mode handover................................................................................................................13

Idle mode handover.....................................................................................................................16

EUTRAN and CDMA2000 Handover..................................................................16

RAN Parameters......................................................................................................20
8.1
8.2

Physical Cell Identity..................................................................................................................20

Root Sequence Index (RSI).........................................................................................................20

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LTE Troubleshooting / Optimization Guidelines

1 General
1.1

Purpose
The purpose of this document is to provide national and local RF
guidelines to troubleshoot and optimize Sprints 4G Network. This
document will be used by Sprint RF Engineering to understand high
level network performance metrics.

1.2

Responsibility
The 4G National RF Performance Engineering team is responsible for
updating, and monitoring the application of the guidelines described in
this document. Please contact the following, if there are questions
regarding these planning guidelines.
Geoff Lubeskie, National RF Planning and Engineering (717-344-1869)
Geoff.lubeskie@sprint.com
Dusty Wyman (703-376-4463) Manager RF Planning and Engineering
dusty.wyman@sprint.com
Rashmi Kumar (703-433-4358) Manager RF Planning and Engineering
Rashimi.Kumar@sprint.com

1.3

Revision History
Date

Version

11/15/201
3

1.0

Document
Owner
Geoff Lubeskie

Comments
Original document (1st Draft)

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LTE Troubleshooting / Optimization Guidelines

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LTE Optimization Process Flows

LTE troubleshooting / optimization activities can be separated into 3 distinct
levels:

Site Level
Cluster Level
Market Level

At the very start, eNBs are the foundation of all LTE Networks. Contiguous
groups of eNBs form clusters and groups of clusters make up the markets.

Figure 1: Network Optimization Flowchart

2.1 Site Level Optimization

Single site verification, the first phase of network optimization, involves
function verification at each new site. Single site verification aims to ensure
that each site is properly installed and that parameters are correctly

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configured according to the Golden Image (GI). A link to the latest GI for all
OEMS can be found at the link below.
http://sprintcommunities.corp.sprint.com/sites/cops/4GRFPerformance/Parameter
%20Management/Forms/AllItems.aspx?RootFolder=%2Fsites%2Fcops%2F4GRFPerformance
%2FParameter%20Management%2FGolden%20Parameters%2FGolden%20Params
Key Performance Indicators (KPIs) ensure each site is performing as it should
be. At the very minimum the engineer should validate and analyze the
following metrics to ensure that the eNB is performing as it should be. It
should be mentioned that each OEM has their own specific targets for each
KPI and should be referenced when analyzing the data.

Average & Peak download Throughput

Average & Peak upload Throughput
Intra eNB handovers (between sectors)
Inter eNB handovers to first tier neighbors
Connection setup time & Connection success rate
Latency
Validate RSRP, CINR, Rx Power, and Tx Power are as expected for the test location

2.2 Cluster Level Optimization

Contiguous coverage between eNBs within a cluster ensures seamless
mobility; therefore, this optimization activity is a major factor in overall
network accessibility and retainability.
As of the writing of this documentation there is no baseline of the Sprint LTE
network. It is imperative that when the OEMs submit clusters for acceptance
that the local RF teams are involved. Local RF teams should create MapInfo
files for each cluster, which show areas for future optimization.

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Figure 2: Mapinfo file created by local RF showing areas for future optimization

A cluster drive route must be carefully designed to cover each sector of all
sites so that all major highways, roads, Sprint stores and major customer
locations are covered. Analysis of the drive data will show areas for potential
optimization changes to improve the overall user experience. All changes
made during the optimization phase should be documented for future
reference and possibly shared with other markets as a means of best
practice.
A major challenge that the engineer will face is the fact that the 4G and 3G
networks are using the same antenna. At this time, voice is still the number
one revenue source for Sprint; therefore, optimization efforts on the 4G sites
should not negatively impact the underlying 3G network.
As in Site level optimization at the very minimum the engineer should verify
the following KPIs during Cluster Optimization

Average & Peak download Throughput

Average & Peak upload Throughput
Intra eNB handovers (between sectors)
Inter eNB handovers to first tier neighbors
Connection setup time & Connection success rate
Latency
Validate RSRP, CINR, Rx Power, and Tx Power are as expected for the test location

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2.3 Market level Optimization

Similar to cluster level optimization, multiple subsets are looked at as a whole.
Here, several clusters should be evaluated and analyzed as a whole to verify
that mobility and proper networking exists. The on-going evolution of the
network due to the addition of new macro, micro, Pico and in-building sites
requires that the engineer continuously look at optimizing the network to meet
the demands of capacity, and customer expectations.

RF Conditions

3.1

RSRP

Reference signal received power (RSRP), is determined for a considered cell as

the linear average over the power contributions (in [W]) of the resource
elements that carry cell-specific reference signals within the considered
measurement frequency bandwidth.
Note: Different from GSM or TD-SCDMA systems, TD-LTE systems have
multiple subcarriers multiplexed. Therefore, the measured pilot signal
strength is the RSRP of a single subcarrier (15 kHz) not the total bandwidth
power of the frequency.
If receiver diversity is in use by the UE, the reported value shall not be lower
than the corresponding RSRP of any of the individual diversity branches
The RSRPs near a cell, in the middle of a cell, and at the edge of a cell are
determined based on the distribution of signals on the entire network.
Generally, the RSRP near a cell is -85 dBm, the RSRP in the middle of a cell is
-95 dBm, and the RSRP at the edge of a cell is -105 dBm.

3.2

SINR

The SINR is not specifically defined in 3GPP specifications. A common formula is

as follows: SINR = S/(I + N)
S: indicates the power of measured usable signals. Reference signals (RS) and
physical downlink shared channels (PDSCHs) are mainly involved.

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I: indicates the power of measured signals or channel interference signals from

other cells in the current system and from inter-RAT cells.
N: indicates background noise, which is related to measurement bandwidths
and receiver noise coefficients.

Cell Selection

The cell selection process and cell selection criteria as per 3GPP standard 36.304
are:

4.1

Cell Selection Process

The UE shall use one of the following two cell selection procedures:
1. Initial Cell Selection
This procedure requires no prior knowledge of which RF channels are E-UTRA
carriers. The UE shall scan all RF channels in the E-UTRA bands according to its
capabilities to find a suitable cell. On each carrier frequency, the UE need only
search for the strongest cell. Once a suitable cell is found this cell shall be
selected.
2. Stored Information Cell Selection
This procedure requires stored information of carrier frequencies and optionally
also information on cell parameters, from previously received measurement control
information elements or from previously detected cells. Once the UE has found a
suitable cell the UE shall select it. If no suitable cell is found the Initial Cell
Selection procedure shall be started.
NOTE: Priorities between different RAT or frequencies provided to the UE by system
information or dedicated signaling are not used in the cell selection process.

4.2

Cell Selection Criteria

The cell selection criterion S is fulfilled when:

Srxlev > 0
Where:
Srxlev = Qrxlevmeas (Qrxlevmin Qrxlevminoffset) -Pcompensation
Where:
The signaled value QrxlevminOffset is only applied when a cell is evaluated for cell
selection as a result of a periodic search for a higher priority PLMN while camped
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LTE Troubleshooting / Optimization Guidelines

normally in a VPLMN [5]. During this periodic search for higher priority PLMN the
UE may check the S criteria of a cell using parameter values stored from a different
cell of this higher priority PLMN.
Srxlev Cell Selection RX level value (dB)
Qrxlevmeas Measured cell RX level value (RSRP).
Qrxlevmin Minimum required RX level in thecell (dBm)
Qrxlevminoffset Offset to the signalled Qrxlevmin taken into account in the Srxlev
evaluation as a result of a periodic search for a higher priority PLMN
while camped normally in a VPLMN [5]
Pcompensation [FFS]

4.3

Cell Reselection

Cell reselection parameters are broadcast in system information and are read from
the serving cell as follows:
Qoffsets,n
Qoffsetfrequency
Qhyst
Qrxlevmin
TreselectionRAT

This specifies the offset between

the two cells.
Frequency specific offset for equal
priority E-UTRAN frequencies.
This specifies the hysteresis value
for
ranking criteria.
This specifies the minimum
required Rx level in the cell in
dBm.
This specifies the cell reselection
timer value. For each target RAT a
specific value for the cell
reselection timer isdefined, which
is applicable when evaluating
reselection within E-UTRAN or
towards other RAT (i.e.
TreselectionRATfor E-UTRAN is
TreselectionEUTRAN, for UTRAN
TreselectionUTRAN for GERAN
TreselectionGERAN,
forTreselectionCDMA_HRPD, and
for TreselectionCDMA_1xRTT).Note:
TreselectionRAT is not sent on
system information, but used in

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reselection rules by the UE for

each RAT.
TreselectionEUTRAN
TreselectionUTRAN
TreselectionGERAN
TreselectionCDMA_HRPD
TreselectionCDMA_1xRTT
Threshx, high

Threshx, low

Threshserving, low

This specifies the cell reselection

timer value TreselectionRAT forEUTRAN
This specifies the cell reselection
timer value TreselectionRAT for
UTRAN
This specifies the cell reselection
timer value TreselectionRAT for
GERAN
This specifies the cell reselection
timer value TreselectionRAT for
CDMA HRPD
This specifies the cell reselection
timer value TreselectionRAT for
CDMA 1xRTT
This specifies the threshold used
by the UE when reselecting
towards the higher priority
frequencyX than currentlyserving
frequency. Each frequency of EUTRAN and UTRAN, each band of
GERAN, each band class of
CDMA2000HRPD and CDMA2000
1xRTT will have a specific
threshold.
This specifies the threshold used in
reselection towards frequencyX
priority from a higher priority
frequency. Eachfrequency of EUTRAN and UTRAN, each band of
GERAN, each band class of
CDMA2000 HRPD and
CDMA20001xRTT will have a
specific threshold.
This specifies the threshold for
serving frequency used in
reselection evaluation towards
lower priority E-UTRANfrequency or

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LTE Troubleshooting / Optimization Guidelines

RAT.
Sintrasearch
Snonintrasearch
TCRmax
NCR_M
NCR_H
TCRmaxHyst

This specifies the threshold (in dB)

for intra frequency measurements.
This specifies the threshold (in dB)
for EUTRAN inter-frequency and
inter-RAT measurements.
This specifies the duration for
evaluating allowed amount of cell
reselection(s).
This specifies the maximum
number of cell reselections to
enter medium mobility state.
This specifies the maximum
number of cell reselections to
enter high mobility state.
This specifies the additional time
period before the UE can enter
normal-mobility.

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Interference Control

Downlink (DL) inter cell interference which reduces the signal quality is a major
factor contributing to degraded service. It usually impacts cell-edge users which
lack good quality RF signal due to the presence of multiple serving sectors of
similar signal strength. DL inter-cell interference scenario can also be observed in
dense urban areas where multipath factor can results in strong signals from
various sectors in one geographic region. DL interference if not corrected can lead
to poor throughput performance on both downlink and uplink. Therefore an
improved DL coverage in terms of both signal strength and quality provides better
user experience.
Indicators such as low Signal to noise ratio (SINR), low scale Channel quality
indicator (CQI), Transmission mode (transmit diversity), low Reference Signal
Received Quality (RSRQ) and high Block error rate (BLER) are common indicators of
DL interference. Low SINR and low CQI reports result in lower and more robust
modulation scheme for data transmission. The first step in optimization efforts is to
improve the coverage and quality of existing serving cells resulting in good quality
of service (QoS).
RSRQ is defined in TS 36.214 as:
Reference Signal Received Quality (RSRQ) is defined as the ratio NRSRP/(E-UTRA
carrier RSSI), where N is the number of RBs of the E-UTRA carrier RSSI
measurement bandwidth. The measurements in the numerator and denominator
shall be made over the same set of resource blocks.
E-UTRA Carrier Received Signal Strength Indicator (RSSI), comprises the linear
average of the total received power (in [W]) observed only in OFDM symbols
containing reference symbols for antenna port 0, in the measurement bandwidth,
over N number of resource blocks by the UE from all sources, including co-channel
serving and non-serving cells, adjacent channel interference, thermal noise etc.
The reference point for the RSRQ shall be the antenna connector of the UE.
If receiver diversity is in use by the UE, the reported value shall not be lower than
the corresponding RSRQ of any of the individual diversity branches.
Other than general optimization practices to control interference, LTE also offers
features such as Inter cell Interference Coordination (ICIC) technique which
dynamically controls interference based on UEs CQI reports.
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Downlink ICIC (DL-ICIC) enhances cell-edge UE performance by adjusting the power

for UE based on reported channel condition. Cell center users get different power
allocation based on UEs feedback.
Average CQI Threshold metric is used to differentiate cell edge and cell center
users. DL power control mechanism uses the channel estimation to adjust the Pa
parameter which leads to:
If the user is estimated to be in cell center condition, UE specific DL power
related parameter Pa is lowered, which results in power reduction of data
subcarriers for that UE and further decreases interference to neighboring
cells

If UE is estimated to be in cell center condition, Pa is increased and hence

data subcarriers power is increased to maintain edge UEs quality

LTE Handof Optimization

Handover success rate is another important KPI focused on in optimization process.

Having a good success rate indicates that sites in network connect to each and
user can enjoy uninterrupted access to network in mobility scenarios. The impact
of LTE handover performance depends on what type of applications users are
running at their end. For example, poor handover performance or high handover
latency have low impact on applications such as file transfer where a small
interruption can be tolerable whereas bad handover performance may have severe
impact on VOIP applications where a handover drop results in voice call drop.

6.1

Active mode handover

Active mode handover can be of three different types:

1. Intra/Inter Frequency Handover between cells using sane or different center

frequencies
2. Intra/Inter eNB Handover between cells of the same or different site
3. S1/X2 based Handover involving MME interaction or directly between two eNBs
using X2 links
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UE can be configured in connected state to report several different types of

measurements based on event types as explained below.

Event A1

Serving becomes better than a threshold

Used to deactivate Gap Measurements

Event A2

Serving becomes worse than a threshold

Used to activate Gap Measurements

Event A3

Neighbor becomes offset better than the Serving

Used to trigger Intra-FA Handoff

Event A4

Neighbor becomes better than a threshold

Used for ANR

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LTE Troubleshooting / Optimization Guidelines

Next section discusses the configuration related to Event A3 which is used to

facilitate Intra-FA LTE handover.

In active mode measurements are performed only when Serving Cell RSRP falls
below a configurable threshold (Smeasure)
The A3 event parameters for Active mode measurement are transmitted via RRC
Connection Reconfiguration Message
The parameter a3offsetdefines the (neighbor + offset > serving) criteria.
Additionally, there is a cell individual offset that can be configured per neighbor
(Ind_offset).
This criterion must be satisfied over a configurable period of time for the
measurement report to be done (TimeToTrigger).
The measurement criteria can be based on RSRP or RSRQ and is configurable
(TriggerQuantity).
The measurement report can be configured to report RSRP/RSRQ or both
(ReportQuantity).

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Periodic reports can be generated after the Event criteria are met based on a
configurable parameter (reportInterval).
Number of reports generated based on the event is controlled using a
configurable parameter (reportAmount)

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6.2

Idle mode handover

Idle mode handover or cell reselection is the process used by UE and network to
monitor UEs location without it requiring radio resources. In Idle mode, UE remains
attached at MME level but remains RRC idle unless it requires RRC resources (for
e.g. To perform TAU or Paging procedures)
Maintaining most current and updated neighbor list on the eNBs is critical to
facilitate successful handover. Neighbor list must be updated frequently to
accommodate addition of new sites and sectors in the network.
Condition where multiple handovers are recorded within a very short period
between same two cells in stationary or mobile scenario is known as Ping-Pong.
Ping-Pong condition affects the end user as more processing time results in poor
user experience. This situation arises when both source and target sectors meet
the handover thresholds and are equivalent in signal strength. Ping-Pong can occur
in both strong and weak conditions. A3 offset, S-measure, Hysteresis and Cell
individual offset are some parameters which can be tweaked to reduce Ping-Pong
rate.

EUTRAN and CDMA2000 Handover

EUTRAN and CDMA2000 handover can be useful when both networks are overlaid on same
geographical region. A user traveling out of LTE coverage area can hand down to HRPD
while maintaining the same data session and uninterrupted data transfer. This feature is
helpful in cases where a new LTE network is deployed on a matured CDMA2000 network
and UE can rely on underlying network whenever it goes out of coverage on LTE
Implementation of Neighbor list for underlying CDMA network is needed to facilitate
EUTRAN to CDMA2000 handover. On LTE side, appropriate neighboring sectors with PN and
channel information are populated. Right HRPD neighbors can be selected based statistics
such as Handover matrix (HOM) data of CDMA network. Optimization drive test can also
give useful information in defining missing or appropriate neighbors for EUTRAN to
CDMA2000 interworking.
Below table explains Parameters and Events used on EUTRAN to CDMA2000 interworking:
Message
RRC Connection
Reconfiguration

IE
B2 Event

Parameter
b2Threshold1Rsrp

Description
RSRP threshold1 used for
triggering the EUTRA
measurement report for
CDMA2000 HRPD Event B2.

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b2Threshold1Rsrq

RRC Connection
Reconfiguration

b2Threshold2Cdma200
0

RSRQ threshold1 used for

triggering the EUTRA
measurement report for
CDMA2000 HRPD Event B2.
CDMA2000 threshold 2 used
for triggering the inter-RAT
CDMA2000 measurement
report for CDMA2000 HRPD
Event B2.

qOffsetFreq
hysteresisB2
timeToTriggerB2

reportIntervalB2
reportAmountB2
maxReportCellsB2

triggerQuantityB2

RRC Connection
Reconfiguration

A2 Event

a2ThresholdRsrp

a2ThresholdRsrq

reportIntervalA2

Hysteresis applied to entry

and leave condition of
CDMA2000 HRPD Event B2.
timeToTrigger value for
CDMA2000 HRPD Event B2.
The timeToTrigger value is the
period of time that must be
met for the UE to trigger a
measurement report.
The reporting interval of a
measurement report for
CDMA2000 HRPD Event B2.
The number of measurement
reports for CDMA2000 HRPD
Event B2.
The maximum number of cells
included in a measurement
report for CDMA2000 HRPD
Event B2.
Quantity that triggers the
Event B2 measurement The
trigger can be set for either
RSRP or RSRQ and is only
applicable on threshold 1.
A2 event is triggered when
source becomes worse than
the configured RSRP threshold
(Refer to standard 36.133 for
RSRP Report mapping)
Primary RSRQ threshold value
for eventA2. Used only when
triggerQuantityA2Prim is set
to RSRQ.
Determines the reporting
interval of a measurement

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LTE Troubleshooting / Optimization Guidelines

report for Event

triggerQuantityA2

A1 event is triggered when

source becomes worse than
the configured RSRQ threshold
(Refer to standard 36.133 for
RSRQ Report Mapping.

hysteresisA2

Hysteresis applied to entry

and leave conditions of Event
A2
The timeToTrigger value is the
period of time that must be
met for the UE to trigger a
measurement report for Event
A2
The number of reports for
periodical reporting for the
primary eventA2
measurement .Value 0 means
that reports are sent as long
as the event is fulfilled.
Primary and secondary
measurement parameters
refer to the option to use
different settings for two
simultaneous measurements
for eventA2.
The maximum number of cells
included in a measurement
report for Event A2.
Determines whether the
Measurement report for A2
event includes both RSRP and
RSRQ information or the only
RSRP or RSRQ as configured
by the Trigger event above.
Filtering coefficient used by
the UE to filter RSRP
measurements before event
evaluation The measurement
filter averages a number of
measurement report values to
filter out the impact of large
scale fast fading.

timeToTriggerA2

reportAmountA2

maxReportCellsA2
reportQuantityA2

filterCoefficientEUtraRs
rp

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RRC Connection
Reconfiguration

A1 Event

filterCoefficientEUtraRs
rq

Filtering coefficient used by

the UE to filter RSRQ
measurements before event
evaluation The measurement
filter averages a number of
measurement report values to
filter out the impact of large
scale fast fading.

a1ThresholdRsrp

A1 event is triggered when

source becomes better than
the configured RSRP threshold
( Actual Threshold= Parameter
-140, 36.133 standards) dBm

a1ThresholdRsrq

A1 event is triggered when

source becomes better than
the configured RSRQ threshold
(Refer to 36.133 standard for
RSRP Report mapping)
Determines whether Event A1
is triggered based on RSRP or
RSRQ criteria.
Determines whether the
Measurement report for A1
event includes both RSRP and
RSRQ information or the only
RSRP or RSRQ as configured
by the Trigger event above.
The maximum number of cells
included in a measurement
report for Event A1.
Hysteresis applied to entry
and leave conditions of Event
A1.
The timeToTrigger value is the
period of time that must be
met for the UE to trigger a
measurement report for Event
A1
Determines the reporting
interval of a measurement
report for Event A1
Determines the number of
measurement reports UE

triggerQuantityA1
reportQuantityA1

maxReportCellsA1
hysteresisA1
timeToTriggerA1

reportIntervalA1
reportAmountA1

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LTE Troubleshooting / Optimization Guidelines

needs to send when Event A1

criteria is met
SIB8

systemTim
eInfo
CellReselec
tion
Parameters
CDMA 2000

timieAndPahseSynchCri
tical

bandClass

cellReselectionPriority

threshXHigh
threshXLow
tReselectionSfUsageHR
PD

tReselectionHRPD

tReselectionSfHighHRP
D

tReselectionSfMediumH
RPD
searchWindowSize

Identifies the CDMA-eHRPD

frequency band class in which
the carrier frequency can be
found
Reselection priority of the cell
in the eNB. The range is 0-7,
where 0 indicates low, and 7
high in priority.
ThreshXHigh of CDMA2000
HRPD band class DB.
ThreshXLow of CDMA2000
HRPD band class DB.
Whether to use
tReselectionSfUsageHRPD of
HRPD reselection information
that is sent down to SIB8.
tReselectionSfUsageHRPD
determines whether to apply a
scaling factor for HRPD cell
reselection.
TReselctionHRPD included in
the HRPD Reselection
information sent to SIB8. The
default is 0, and can be
changed by the operator.
Value by which parameter
tReselectionCdmaHrpd is
multiplied if the UE is in a high
mobility state as defined in
3GPP TS 36.304
TReselectionSfMediumHRPD
included in the HRPD
Reselection information sent
to SIB8.
The size of the search window
in the eNB.

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24

LTE Troubleshooting / Optimization Guidelines

RAN Parameters

8.1 Physical Cell Identity

PCI is derived from two physical layer signals Primary Synchronization Signal
(PSS) and Secondary synchronization signal (SSS). There are 504 unique PCIs. The
physical-layer cell identities are grouped into 168 unique physical-layer cellidentity groups, each group containing three unique identities. The grouping is
such that each physical-layer cell identity is part of one and only one physical-layer
cell-identity group. A physical-layer cell identity is thus uniquely defined by a
number in the range of 0 to 167, representing the physical-layer cell-identity
group, and a number in the range of 0 to 2, representing the physical-layer identity
within the physical-layer cell-identity group.(2) ID (1) ID cell ID 3N N N (1) ID
N (2) ID N
Each cells Reference signal transmits a pseudo random sequence corresponding to
assigned PCI. And channel quality measurements are also made on reference
signals. Thus, an optimized allocation of PCIs is needed to avoid problems in cell
recognition or cell search. During PCI planning, one needs to avoid same PCI and
PSS on neighboring cell. This eliminates confusion in cell search and also reduces
interference which can occur due to PSS or reference signal collision.

8.2 Root Sequence Index (RSI)

The Preambles used in RACH procedure are derived from Root Sequence.
Preambles are obtained by cyclic shifts of root sequence which are based on
Zadoff-Chu sequence. There are 838 Root Sequences available. There are 64
preambles available per cell and UE randomly selects one preamble to perform
random access procedure. If number of preambles per root sequence is less than
64 Preambles, continue deriving Preambles with next Root Sequence unit 64
preambles are obtained.
Thus, unique assignment of Root sequence is recommended between neighboring
cells. The Below tables describes Ncs to Zero Correlation zone configuration
mapping and LSM parameter for configuring RSI and Zero correlation zone
configuration parameter.

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or privileged materials intended for the sole use of the intended recipient. Any review, use, distribution or disclosure is prohibited without authorization

25

LTE Troubleshooting / Optimization Guidelines

Privileged & Confidential Information

This information is subject to Sprint policies regarding use and is the property of Sprint and/or its relevant affiliates and may contain restricted, confidential
or privileged materials intended for the sole use of the intended recipient. Any review, use, distribution or disclosure is prohibited without authorization

26

LTE Troubleshooting / Optimization Guidelines

References

https://Systems.samsungwireless.com
Network Vision > Publications > Sprint > 4G RAN > Manuals

430 LTE eNB Maintenance Troubleshooting Manual

410 MMBS Operational Manual
819 LTE Optimization Guidelines
LTE standard documents: 3GPP TS 36 series
LTE optimization guidelines Huawei Technologies
LTE Optimization Guidelines Anritsu

Privileged & Confidential Information

This information is subject to Sprint policies regarding use and is the property of Sprint and/or its relevant affiliates and may contain restricted, confidential
or privileged materials intended for the sole use of the intended recipient. Any review, use, distribution or disclosure is prohibited without authorization

27