819 LTE Optimization
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INTRODUCTION
Purpose
This manual describes LTE Optimization process flow, practices and call release cause.
Document Content and Organization
This manual contains the following:
CHAPTER 1. LTE Optimization Process Flow
This chapter describes the site, cluster and market level optimizations.
CHAPTER 2. LTE Optimization Practices
This chapter describes the coverage improvement, interference control, LTE handover
optimization, EUTRAN/CDMA2000 Handover, RAN parameters, eNodeB control
parameters and parameter reference guide.
CHAPTER 3. Call Release Cause
This chapter describes the call release cause.
CHAPTER 4. References
Revision History
Version DATE OF ISSUE REMARKS Author
1.0 11. 2012. First Edition Abhishek Warhadkar 1.1 12.2012 Added section 2.8, Updated
Chapter 4 References
TABLE OF CONTENTS
Revision History ... ii
CHAPTER 1. LTE Optimization Process Flow
2-1
1.1 Site Level Optimization ... 2-1 1.2 Cluster Level Optimization+... 2-2 1.3 Market level Optimization ... 2-5
CHAPTER 2. LTE Optimization Practices
2-1
2.1 Coverage Improvement ... 2-1
2.1.1 Techniques to improve coverage ... 2-1
2.2 Interference Control... 2-4 2.3 LTE Handover Optimization ... 2-9
2.3.1 Active mode handover ... 2-9 2.3.2 Idle Mode Handover ... 2-14
2.4 EUTRAN and CDMA2000 Handover ... 2-16 2.5 RAN Parameters ... 2-21
2.5.1 Physical Cell Identity ... 2-21 2.5.2 Root Sequence Index (RSI) ... 2-22
2.6 e-NodeB - Control Parameters ... 2-23 2.7 Parameter Reference Guide ... 2-23 2.8 Relevant Documents and Processes ... 2-23
CHAPTER 3. Call Release Cause
3-24
CHAPTER 4. References
4-1
LIST OF FIGURES
Figure 1: Site level testing process flow ... 2-2 Figure 2: Cluster Drive testing scenario ... 2-3 Figure 3: LTE Cluster Optimization Process Flow ... 2-3 Figure 4: LTE Optimization Practices... 2-4 Figure 5: Indicators of DL Interference ... 2-5 Figure 6: Example of an overshooting sector ... 2-6 Figure 7: Improvement in SINR as a result of down-tilt ... 2-7 Figure 8: X2 based Active handover call flow ... 2-10 Figure 9: A3 Event description ... 2-11 Figure 10: Example of Handover optimization ... 2-15 Figure 11: Operational procedure for Neighbor Relation Optimization ... 2-15 Figure 12: Example of optimum PSS planning ... 2-21
CHAPTER 1.
LTE Optimization
Process Flow
LTE performance optimization activities can be divided into three different levels:
1. Site level
2. Cluster level
3. Market level
1.1 Site Level Optimization
Single sites are the basic building blocks of wireless networks. Contiguous sites form clusters and
clusters constitute markets. Therefore optimization of a network begins with individual sites. Site
level testing is a critical step in the process to ensure each site is meeting all the key performance
indicator (KPI) targets. This type of testing can also be referred to as site level drive testing, site
level shakedown or site level acceptance testing. It can begin as soon as a site is on-air and
functional. Scope for site level testing can vary from basic to a detailed. Most operators and OEMs
perform the following basic tests as a part of site level testing:
A. Peak uplink and downlink throughput test
B. Intra-eNB handovers
C. Inter-eNB handover to immediate first tier neighbors
D. Radio latency test
E. Call success test
Additionally, sector level parameters and data fill are also verified during the course of this activity.
Examples are listed below:
1. Commissioning tests: These tests certify there are no discrepancies in configured
parameters such as Transmit power, Diversity paths etc.
2. Sweep tests: VSWR and uplink noise tests guarantee that sites do not have any anomalies
in coax, fiber and antenna installation. Uplink noise test also eliminate possibility of
external interference.
3. RF parameters: Site and sector level parameters such as PCID, RACH, sector orientation
or azimuth are also verified.
4. Alarm testing
Figure 1: Site level testing process flow
1.2 Cluster Level Optimization+
Cluster level performance testing or optimization activity is the next key factor in network
optimization. A cluster is a group of several on-air contiguous sites. Contiguous coverage between
sites of a cluster is a critical factor in ensuring seamless mobility. Site level testing as described in
the previous section is usually considered a prerequisite for cluster level testing. Once a cluster is
formed, a baseline drive test is conducted to capture the pre-optimization performance of the cluster.
A cluster drive route must be carefully designed to cover each sector of all sites so that major roads,
thruways, points of interest and demographics important to operators are covered. The drive data is
then analyzed and studied for potential optimization changes to improve user experience.
Suggested changes are implemented and a re-drive is conducted to recapture the performance
improvement. All changes made during the optimization phase must be documented for future
reference. Cluster optimization becomes challenging when there are common elements such as a
shared antenna between two technologies. A balance or trade-off must be considered while
optimizing such networks as improving one network may negatively impact the other underlay or
overlay network.
Iperf/ftp clients Test UEs eNB EPC Iperf/FTP servers eNB monitoring tool Test equipment in vehicle eNB Pre-determined route Intra eNB HO point ` ` Intra eNB HO point ` Inter eNB HO point ` Intra eNB HO point
Figure 2: Cluster Drive testing scenario
Examples of major KPIs included in cluster level optimization testing are as follows:
1. Connection/call success rate
2. Connection/call drop rate
3. Average uplink throughput
4. Average downlink throughput
5. Average Radio latency
6. Handover success rate and Handover latency
The objective of cluster level testing is to meet or exceed all KPI targets. In situations where one or
more KPIs are not met, possible recommendations should be evaluated: addition of new sites or
sector, antenna replacement, addition of capacity carriers etc. are put forth to achieve required
performance. Figure 1D explains basic LTE optimization practices.
Figure 4: LTE Optimization Practices
LTE standard has a large number of configurable parameters which can affect the performance
aspect of the network. To maintain consistency, several of these parameters must be set to a global
default value. Global default value also referred to as „Golden Parameters‟ must be discussed and
consulted between the OEM and Operator so that an optimized value can be determined based on
laboratory testing, simulating techniques and real world subscriber scenarios.
RF design simulations can also assist in finalizing the physical changes intended coverage
changes which can be useful in evaluating the impact before implementation. Costly measures such
as physical changes, antenna azimuth or radiation center changes must be carefully assessed to
minimize customer impact and service degradation below set target. Overlapping coverage between
sites is crucial to accomplish optimal handover performance.
Neighbor list implementation ensures successful handover between contiguous sites and sectors.
An initial neighbor list plan can be generated using RF design tools or any other similar tool
capable of designing neighbor plans. Maintaining updated neighbor lists for every site is
recommended to facilitate successful handovers in an evolving network. Neighbor lists from
underlying technology, if available, can be useful first-hand information.
LTE parameters like Physical cell identity (PCI), Root sequence index, Traffic area codes, Traffic
area lists etc. must be planned prior to the commencement of optimization activity. These
parameters can be tweaked during the optimization phase.
The addition of new sites or sectors to the network is considered when existing sites cannot provide
sufficient coverage in terms of reliability and sustainability. Optimization engineers should propose
such ideas to the RF design group to consider during cell planning exercise and network expansion.
1.3 Market level Optimization
For an evolving network, optimization can be a routine activity. Deployment of new macro sites,
small cells, in-building solutions are always considered to meet the high demand of capacity and
bandwidth. Regular network tweaks and optimization efforts are always needed when new network
elements are integrated to serve increased demands and improvement of user experience.
Market level optimization can be considered a final step in accomplishing a high performing LTE
network. This activity is similar to cluster level activity where multiple optimized clusters are
evaluated and analyzed to ensure proper networking and mobility between them.
CHAPTER 2.
LTE Optimization
Practices
2.1 Coverage Improvement
Cell site planning is an important factor in network design process. Antenna selection, antenna
radiation center, antenna tilt (mechanical or electrical) and antenna azimuth governs the coverage
of any given cell site. Lack of coverage also referred to as lack of dominant server or coverage hole
happens when any given geographic region does not have enough RF coverage to serve both fixed
and mobile subscribers. Strength of Reference signal is used in determining the coverage holes.
In LTE terms (as defined in TS 36.214), Reference signal received power is defined as:
Reference signal received power (RSRP), is defined 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.
For RSRP determination the cell-specific reference signals R
0according TS 36.211 [3] shall be
used. If the UE can reliably detect that R
1is available it may use R
1in addition to R
0to determine
RSRP.
The reference point for the RSRP 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 RSRP of any of the individual diversity branches
2.1.1 Techniques to improve coverage
1. Antenna orientation and tilt – Pointing the antenna in direction of interest and adjusting the
tilt (mechanical or electrical) is the most common practice to control coverage. Availability
of the remote electrical tilt (RET) feature has made this task more convenient by not
requiring tower climb or visits to the cell site location. Electrical tilt change should also be
evaluated using proper design tools to estimate the effect before implementation. Minimum
to no harm should be maintained while implementing change in tilt or azimuth. In other
words, while adjusting tilt and azimuth, one must make sure that the suggested change will
not adversely affect existing coverage and served subscribers.
2. Antenna diversity – Adding diversity in uplink is another practice to improve uplink cell
coverage. Uplink diversity improves the „receive sensitivity‟ of eNB resulting in better
uplink coverage.
3. Cell selection threshold QRxLevMin – This parameter specifies the minimum required Rx
level in the cell in dBm. Cell selection process and cell selection criteria as per 3GPP
standard 36.304 are:
Cell Selection process
Description
The UE shall use one of the following two cell selection procedures:
a) 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.
b) 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.
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 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 the cell (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]
Cell reselection parameters in system information broadcasts
Cell reselection parameters are broadcast in system information and are read from the serving cell
as follows:
Qoffsets,n
This specifies the offset between the two cells.
Qoffsetfrequency
Frequency specific offset for equal priority E-UTRAN frequencies.
Qhyst
This specifies the hysteresis value for ranking criteria.
Qrxlevmin
This specifies the minimum required Rx level in the cell in dBm.
TreselectionRAT
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 reselection rules by the UE for each
RAT.
TreselectionEUTRAN
This specifies the cell reselection timer value TreselectionRAT for
E-UTRAN
TreselectionUTRAN
This specifies the cell reselection timer value TreselectionRAT for
UTRAN
TreselectionGERAN
This specifies the cell reselection timer value TreselectionRAT for
GERAN
TreselectionCDMA_HRPD This specifies the cell reselection timer value TreselectionRAT for
CDMA HRPD
TreselectionCDMA_1xRTT This specifies the cell reselection timer value TreselectionRAT for
CDMA 1xRTT
Threshx, high
This specifies the threshold used by the UE when reselecting towards
the higher priority frequency X than currentlyserving frequency. Each
frequency of E-UTRAN and UTRAN, each band of GERAN, each
band class of CDMA2000HRPD and CDMA2000 1xRTT will have a
specific threshold.
Threshx, low
This specifies the threshold used in reselection towards frequency X
priority from a higher priority frequency. Eachfrequency of E-UTRAN
and UTRAN, each band of GERAN, each band class of CDMA2000
HRPD and CDMA20001xRTT will have a specific threshold.
Threshserving, low
This specifies the threshold for serving frequency used in reselection
evaluation towards lower priority E-UTRANfrequency or RAT.
Sintrasearch
This specifies the threshold (in dB) for intra frequency measurements.
Snonintrasearch
This specifies the threshold (in dB) for EUTRAN inter-frequency and
inter-RAT measurements.
TCRmax
This specifies the duration for evaluating allowed amount of cell
reselection(s).
NCR_M
This specifies the maximum number of cell reselections to enter
medium mobility state.
NCR_H
This specifies the maximum number of cell reselections to enter high
mobility state.
TCRmaxHyst
This specifies the additional time period before the UE can enter
normal-mobility.
4. Cell selection threshold Qqualmin - Minimum required quality level in the cell (dB). This
is applicable only for FDD cells.
5. Uplink Power control – Uplink power control determines the average power over a
SC-FDMA symbol in which the physical channel is transmitted. PUCCH supports transmission
of ACK/NACK, CQI report and scheduling requests. Coverage can be controlled by UEs
Physical Uplink Control Channel (PUCCH) and Physical Uplink Shared Channel (PUSCH).
Parameters p0_nominal_pusch and p0_nominal_pucch are two critical parameters which
define PUSCH and PUCCH transmit power.
2.2 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 N×RSRP/(E-UTRA carrier
RSSI), where N is the number of RB’s 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.
DL interference is usually controlled by maintaining equal power boundaries for cells within a
contiguous cluster. Containing the coverage of a cell only to its intended service region ensures that
the cell is not overshooting and adding to DL interference elsewhere. For boomer sites, use of
mechanical tilt is common practice to contain the coverage and direct the energy in intended
service areas. In reference to mechanical tilt, the gain reduction occurs in the direction or azimuth
of antenna whereas with electrical tilt, there is identical gain reduction in all directions. Antenna
selection during design process is also crucial in planning a good quality network. Knowledge of
antenna characteristics such as horizontal and vertical beam width and side lobes should be utilized
in selecting optimized tilts and azimuth. Transmit attenuation can be used to control excessive DL
interference.
A proper drive test must be conducted to identify the root cause of DL interference. The use of
scanners is recommended; scanner log analysis is useful in pin-pointing overshooting sectors.
Introduction of a new channel or carrier is another approach to tackle interference. However, many
operators do not have this option due to limited licensed spectrum. The idea of new macro or small
cell additions and capacity carriers are considered in cases where DL interference cannot be
controlled due to several network constraints.
Figure 7: Improvement in SINR as a result of down-tilt
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 UE‟s CQI reports.
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 UE‟s
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 UE‟s quality
The ratio of PDSCH EPRE to cell-specific RS EPRE among PDSCH REs (not applicable to
PDSCH REs with zero EPRE) for each OFDM symbol is denoted by either
Aor
Baccording
Uplink ICIC (UL-ICIC) feature is used to control uplink interference. Below flow explains how
uplink power control is implemented using indicators such as Interference over thermal (IOT),
Interference overload indicator (IOI).
eNBs exchange IOI over X2 Interface
o IOI Information is set as (High/Medium/Low) on per PRB basis
eNB estimates the IOT (Interference Over Thermal) on per PRB basis
IOT is an estimation of interference from neighboring cells
IOT is estimated as:
o RSSI - Serving_signal_power - Thermal Noise
o Serving Signal Power = Based on UE Channel Estimation (using SRS/DMRS)
o Thermal Noise = Based on minimum RSSI over a collection period
Following parameters are then used to determine the IOI indication based on IOT
Parameter
Range
Default
Description
UL TARGET IOT
1 to 128
(step size :
0.25dB)
32
(8dB)
The desired IOT (interference over thermal) from neighboring
cells used for the ICIC Procedure as explained below
UL IOI
THRESHOLD
STEP
1 to 128
(step size:
0.25dB)
2
(0.5dB)
Interference overload indicator(IOI) is a signaling to the
neighboring cells to indicate the interference status
(high/medium/low) for ICIC operation
IOI is set as:
If current IOT < (ulTargetIot – ulIoiThresholdStep ), IOI =
low status
If current IOT > (ulTargetIot + ulIoiThresholdStep ), IOI =
high status
Else, IOI = medium status.
eNB calculates ICIC metric of each UE at every ICIC period
ICIC metric= (IOI_factor) + (delta_interference) + (Fairness Factor)
o IOI_factor is cell-specific
Reflects the estimated neighboring eNBs‟ interference level experienced.
IOI_factor is calculated from IOI information from all neighboring eNBs
by averaging the IOI information of all PRBs and all eNBs.
o Delta_interference is UE-specific
Contributed IOT is estimated interference to neighboring eNBs created by
UE
Amount of contributed IOT can be determined by path loss between UE
and neighboring eNBs and by using the UE Transmit Power information
from PHR (Power Headroom Report)
Path loss can be obtained using the measurement report from UE
or
Estimation based on UE‟s channel condition (CQI, RSRP etc.)
o Fairness Factor is UE-specific
Results in fairness among UEs, without which, cell center UEs could have
very low ICIC metric causing them to use high power
Power control
o For UEs with high ICIC metric, TPC (Transmit Power Command) of -1dB is used.
o For UEs with low ICIC metric, TPC of +1dB is used.
2.3 LTE Handover 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 a
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.
2.3.1 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
UE can be configured in connected state to report several different types of measurements based on
event types as explained below.
o Event A1
Serving becomes better than a threshold
Used to deactivate Gap Measurements
o Event A2
Serving becomes worse than a threshold
Used to activate Gap Measurements
o Event A3
Neighbor becomes offset better than the Serving
Used to trigger Intra-FA Handoff
o Event A4
Neighbor becomes better than a threshold
Used for ANR
Figure 8: X2 based Active handover call flow
Next section discusses the configuration related to Event A3 which is used to facilitate Intra-FA
LTE handover.
Figure 9: A3 Event description
• 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 a3offset defines 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).
• 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)
LSM Command LSM Parameter Unit
Range
Default
RTRV-EUTRA-A3-CNF
A3_Offset
0.5db -30db to +30db
4
Time_To_Trigger ms
0,40,64,80,100,128,
160,256,320,480,512,640,1024,1280,2560
,5120
480ms
Trigger_Quantity
RSRP or RSRQ
RSRQ
Report_Quantity
Same as Trigger Quantity
Or
Both
Both (RSRQ &
RSRP)
Report_Interval
ms
120ms, 240ms, 480ms, 640ms, 1024ms,
2048ms, 5120ms, 10240ms, 1min,
6min, 12min, 30min, 60min
240ms
Report_Amount
1,2,4,8,16,32,64, infinity
8
CHG-MEAS-FUNC
S_Measure
*RSRP
Range
0 ~ 97
60
LSM
Command
LSM Parameter
Range/Size
Default
Details
CHG-QUANT-EUTRA
Rsrp_Filter_Coefficient
fc0, fc1, fc2, fc3,
fc4, fc5,
fc6, fc7, fc8, fc9,
fc11, fc13,
fc15, fc17, fc19
4
The RSRP measurement is
filtered by the UE before
sending the measurement report
using the following formula. M
is the latest measured result, F
is the filtered result and the
factor “a” is based on the filter
coefficient. More the
co-efficient the new filtered result
is influenced more by the
previous filtered value than the
current measured value.
a = 1/2(k/4)
rsrqFilterCoefficient
fc0, fc1, fc2, fc3,
fc4, fc5,
fc6, fc7, fc8, fc9,
fc11, fc13,
fc15, fc17, fc19
4
The RSRQ measurement is
filtered by the UE before
sending the measurement report
using the following formula. M
is the latest measured result, F
is the filtered result and a is
based on the filter coefficient.
More the co-efficient the new
filtered result is influenced
more by the previous filtered
value than the current measured
value.
A3 offset and Smeasure are two critical parameters which can be tweaked to improve handover
performance. Additionally, „cell individual offset‟ and „Hysteresis‟ parameters can be applied to
improve handover performance.
A3 event description as per 3GPP TS 36.331:
The UE shall:
1> consider the entering condition for this event to be satisfied when condition A3-1, as
specified below, is fulfilled;
1> consider the leaving condition for this event to be satisfied when condition A3-2, as specified
below, is fulfilled;
Inequality A3-1 (Entering condition)
Off Ocs Ofs Ms Hys Ocn Ofn Mn
Inequality A3-2 (Leaving condition)
Off Ocs Ofs Ms Hys Ocn Ofn Mn
The variables in the formula are defined as follows:
Mn is the measurement result of the neighbouring cell, not taking into account any offsets.
Ofn is the frequency specific offset of the frequency of the neighbour cell (i.e. offsetFreq as
defined within measObjectEUTRA corresponding to the frequency of the neighbour cell).
Ocn is the cell specific offset of the neighbour cell (i.e. cellIndividualOffset as defined within
measObjectEUTRA corresponding to the frequency of the neighbour cell), and set to zero if
not configured for the neighbour cell.
Ms is the measurement result of the serving cell, not taking into account any offsets.
Ofs is the frequency specific offset of the serving frequency (i.e. offsetFreq as defined within
measObjectEUTRA corresponding to the serving frequency).
Ocs is the cell specific offset of the serving cell (i.e. cellIndividualOffset as defined within
measObjectEUTRA corresponding to the serving frequency), and is set to zero if not
configured for the serving cell.
Hys is the hysteresis parameter for this event (i.e. hysteresis as defined within
reportConfigEUTRA for this event).
Off is the offset parameter for this event (i.e. a3-Offset as defined within reportConfigEUTRA
for this event).
Mn, Ms are expressed in dBm in case of RSRP, or in dB in case of RSRQ.
Ofn, Ocn, Ofs, Ocs, Hys, Off are expressed in dB.
2.3.2 Idle Mode Handover
Idle mode handover or cell reselection is the process used by UE and network to monitor UE‟s
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 eg. 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. Fig 1I shows an
example of Ping-Pong condition
Figure 10: Example of Handover optimization
Samsung eNB's neighbor optimization function calculates the neighbor priority and optimally
manages the neighbor information based on calculated priority. In addition, it prevents handover
execution for a specific cell using handover blacklist feature. The priority is calculated using
handover statistics. It maintains the optimum and most current neighbor information by
periodically calculating the priorities.
LSM Serving Cell UE (1) HO Statistics Measurement Report Target Cell HO preparation HO Command HO execution
(2) Ranking Calculation Period
Change from NRT to HO Black List Restore from HO Black
List to NRT (3) CLI command (NO HO = ON or OFF) NR Ranking Calculation Lower HO Quality Calculation HO-to-Black-Cell Ratio Calculation
The automatic neighbor relation function through UE measurement is used for adding
neighbors via the LSM or the UE measurement in the following cases:
During UE handover
When source cell lacks the target cell neighbor information
This function can be turned on/off using the CHG-SONFN-CELL command.
The CHG-SONFN-CELL command has the following ANR_ENABLE field parameter values:
sonFuncOff: The ANR function is not performed.
sonManualApply: NR deletion (X2 based), handover blacklist addition according to
NR priority level and NRT recovery are performed automatically. Note that NR
deletion or blacklist addition requires user confirmation.
sonAutoApply: NR deletion (X2 based), handover blacklist addition according to NR
priority level and NRT recovery are performed automatically.
2.4 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
IE
Parameter
Description
RRC
Connection
Reconfiguration
B2 Event
b2Threshold1Rsrp
RSRP threshold1 used for
triggering the EUTRA
measurement report for
CDMA2000 HRPD Event B2.
b2Threshold1Rsrq
RSRQ threshold1 used for
triggering the EUTRA
measurement report for
CDMA2000 HRPD Event
B2.
b2Threshold2Cdma2000
CDMA2000 threshold 2 used
for triggering the inter-RAT
CDMA2000 measurement
report for CDMA2000
HRPD Event B2.
qOffsetFreq
hysteresisB2
Hysteresis applied to entry
and leave condition of
CDMA2000 HRPD Event B2.
timeToTriggerB2
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.
reportIntervalB2
The reporting interval of a
measurement report for
CDMA2000 HRPD Event
B2.
reportAmountB2
The number of measurement
reports for CDMA2000
HRPD Event B2.
maxReportCellsB2
The maximum number of
cells included in a
measurement report for
CDMA2000 HRPD Event B2.
triggerQuantityB2
Quantity that triggers the
Event B2 measurement The
trigger can be set for either
RSRP or RSRQ and is only
applicable on threshold 1.
RRC
Connection
Reconfiguration
A2 Event
a2ThresholdRsrp
A2 event is triggered when
source becomes worse than
the configured RSRP
threshold (Refer to standard
36.133 for RSRP Report
mapping)
a2ThresholdRsrq
Primary RSRQ threshold
value for eventA2. Used only
when triggerQuantityA2Prim
is set to RSRQ.
reportIntervalA2
Determines the reporting
interval of a measurement
report for Event A2
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
timeToTriggerA2
The timeToTrigger value is
the period of time that must
be met for the UE to trigger a
measurement report for Event
A2
reportAmountA2
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.
maxReportCellsA2
The maximum number of
cells included in a
measurement report for Event
A2.
reportQuantityA2
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.
filterCoefficientEUtraRsrp
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.
filterCoefficientEUtraRsrq
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.
RRC
Connection
Reconfiguration
A1 Event
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)
triggerQuantityA1
Determines whether Event A1
is triggered based on RSRP or
RSRQ criteria.
reportQuantityA1
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.
maxReportCellsA1
The maximum number of
cells included in a
measurement report for Event
A1.
hysteresisA1
Hysteresis applied to entry
and leave conditions of Event
A1.
timeToTriggerA1
The timeToTrigger value is
the period of time that must
be met for the UE to trigger a
measurement report for Event
A1
reportIntervalA1
Determines the reporting
interval of a measurement
report for Event A1
reportAmountA1
Determines the number of
measurement reports UE
needs to send when Event A1
criteria is met
SIB8
systemTimeInfo timeAndPhaseSynchCritical
CellReselection
Parameters
CDMA 2000
bandClass
Identifies the CDMA-eHRPD
frequency band class in which
the carrier frequency can be
found
cellReselectionPriority
Reselection priority of the cell
in the eNB. The range is 0-7,
where 0 indicates low, and 7
high in priority.
threshXHigh
ThreshXHigh of CDMA2000
HRPD band class DB.
threshXLow
ThreshXLow of CDMA2000
tReselectionSfUsageHRPD
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.
tReselectionHRPD
TReselctionHRPD included in
the HRPD Reselection
information sent to SIB8. The
default is 0, and can be
changed by the operator.
tReselectionSfHighHRPD
Value by which parameter
tReselectionCdmaHrpd is
multiplied if the UE is in a
high mobility state as defined
in 3GPP TS 36.304
tReselectionSfMediumHRPD TReselectionSfMediumHRPD
included in the HRPD
Reselection information sent
to SIB8.
searchWindowSize
The size of the search window
2.5 RAN Parameters
This section talks about two eNB sector level parameters called, Physical Cell Identity (PCI) and
Root Sequence Index (RSI).
2.5.1 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 cell-identity 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
N
IDcell
3
N
ID(1)
N
ID(2)is thus
uniquely defined by a number
N
ID(1)in the range of 0 to 167, representing the physical-layer
cell-identity group, and a number
N
ID(2)in the range of 0 to 2, representing the physical-layer identity
within the physical-layer cell-identity group.
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.
2.5.2 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. Below two
tables describes Ncs to Zero Correlation zone config mapping and LSM parameter for configuring
RSI and Zero correlation zone config parameter.
CS
N
configurationN
CS valueUnrestricted set Restricted set
0 0 15 1 13 18 2 15 22 3 18 26 4 22 32 5 26 38 6 32 46 7 38 55 8 46 68 9 59 82 10 76 100 11 93 128 12 119 158 13 167 202 14 279 237 15 419 -
LSM Parameter
type
Parameter
Range Default
CHG-PRACH-CONF
Root_sequence_Index
0 ~ 837 Planned
Zero_correl_zone_config 0 ~ 15
12
Prach_Config_Index
0 ~ 63
3 (Alpha)
4 (Beta)
5 (Gamma)
2.6 e-NodeB - Control Parameters
This section describes some parameters which can help improve call sustainability and reliability
resulting in better network performance.
HARQ Control
CQI Control
AMC Control
2.7 Parameter Reference Guide
Following mapping table provides a quick reference guide for optimization and troubleshooting
each of the LTE KPIs:
KPI
Parameters/Drive test log analyses
Soft Parameters eNB/LSMR
Connection
success rate
RSRP, SINR
QRxlevMin, QqualMin, Backoff
Parameter, MSG4HARQ, eHRPD
redirection parmeters
Connection
drop rate
RSRP, SINR, UL BLER, DL BLER
Check call release cause
Handover
Success Rate
RSRP, SINR
X2 link status, Neighbor list, A3 offset,
Smeasure, Cell Individual offset, ANR,
PCI collision
Handover
Latency
HO Interruption time
Backhaul delay, X2 interface
DL Throughput
RSRP, SINR, DL MCS, DL RB,
PDSCH TP, RI, CQI, DL BLER
DL ICIC
UL Throughput
RSRP, SINR, UL MCS, UL RB,
PUSCH TP, CQI, UL BLER, PDCCH
BLER
UL ICIC
2.8 Relevant Documents and Processes
Please contact Sprint or STA National RF team for latest releases of following documents:
1. Site Modification Process Flow
2. Golden Parameters for LTE and eHRPD
3. Released feature request documentation (FRD)
4. 510 LTE eNB Maintenance Manual
CHAPTER 3.
Call Release Cause
The Call Release Cause is explained below:
Value Call Release
Cause Description Collection Time
DEC HEX 256 0X0100 S1AP_CauseRadio Network_ unspecified A failure occurs in GW during the handover, or the handover preparation fails if the MME cannot process the handover.
When the target eNB receives the Handover Cancel message from the source eNB.
283 0x011B S1AP_invalid_qos_ combination
The action fails due to invalid QoS combination.
- When gbrType of QCI received within
E_RABLevelQoSParameters IE of the Initial Context Setup Request message is GBR but
gbrQosInformation received is not present.
- When gbrType of QCI received within
E_RABLevelQoSParameters IE of the E_RAB Setup Request message is GBR but
gbrQosInformation received is not present.
- When gbrType of QCI received within
E_RABLevelQoSParameters IE of the E_RAB Modify Request message is GBR but
gbrQosInformation received is not present.
307 0x0133 S1AP_authenticatio n_failure
The action occurs due to the authentication failure.
Used in the UE context release when the call fails due to the authentication failure.
566 0X0236 X2AP_CauseMisc_ unspecified
Default X2 cause in the eNB.
When the target eNB receives the Handover Cancel message from the source eNB.
768 0X0300 RRC_TMOUT_ rrcConnectionSetu p The RRC Connection Setup Complete message is not received after the RRC
Connection Setup message is sent to the UE.
When timRrcConnectionSetup message is received because the timer is ended that waits until the RRC Connection Setup Complete message is received after sending the RRC Connection Setup message to the UE
Value Call Release
Cause Description Collection Time
DEC HEX 769 0X0301 RRC_TMOUT_ rrcConnectionReco nfig The RRC Connection Reconfiguration
Complete message is not received after the RRC Connection
Reconfiguration message is sent to the UE.
When timRrcConnectionReconfig message is received due to the timer termination while waiting to receive the RRC Connection Reconfiguration Complete message after the RRC Connection Reconfiguration message is sent to the UE - SB2DB State: sending
Initial Context Setup Failure
- SB2DB state: Initial Context Setup Failure
- Other State: sending UE Context Release Request
- INCELLue state: UE Context Release Request
- REESTue2 state: UE Context Release Request
- GAPprepare state: UE Context Release Request
- ANRprepare state: UE Context Release Request 770 0X0302 RRC_TMOUT_ rrcConnectionReEs tablish The RRC Connection Reestablishment
Complete message is not received after the RRC Connection
Reestablishment message is sent to the UE.
When
timRrcConnectionReEstablish message is received due to the timer termination while waiting to receive the RRC Connection Reestablishment Complete message after the RRC Connection Reestablishment message is sent to the UE
771 0X0303
RRC_TMOUT_ rrcSecurityModeCo mmand
The Security Mode Complete message is not received after the Security Mode Command message is sent to the UE.
When the
timRrcSecurityModeCommand message is received due to the timer termination while waiting to receive Security Mode Complete message after the Security Mode Command message is sent to the UE 772 0X0304 RRC_TMOUT_ rrcUeCapabilityEnq uiry The UE Capability Information message is not received after the UE Capability Enquiry message is sent to the UE.
When the
timRrcUeCapabilityEnquiry message is received due to the timer termination while waiting to receive the UE Capability Information message after the UE Capability Enquiry message is sent to the UE 775 0X0307 RRC_TMOUT_intra _ HandoverCmdCom plete The RRC Connection Reconfiguration
Complete message is not received after the RRC Connection
Reconfiguration message is sent to the UE during the Intra handover.
When the timer ends while waiting to receive the RRC Connection Reconfiguration Complete message after the RRC Connection Reconfiguration message is sent to the UE during the intra eNB handover
Value Call Release
Cause Description Collection Time
DEC HEX 776 0X0308 RRC_TMOUT_inter _ X2HandoverCmdC omplete The RRC Connection Reconfiguration
Complete message is not received after the RRC Connection
Reconfiguration message is sent to the UE during the X2 handover.
When the timer ends while waiting to receive the RRC Connection Reconfiguration Complete message after the RRC Connection Reconfiguration message is sent to the UE during the intra X2 handover
777 0X0309 RRC_TMOUT_inter _ S1HandoverCmdC omplete The RRC Connection Reconfiguration
Complete message is not received after the RRC Connection
Reconfiguration message is sent to the UE during the S1 handover.
When the timer ends while waiting to receive the RRC Connection Reconfiguration Complete message after the RRC Connection Reconfiguration message is sent to the UE during the intra S1 handover
787 0X0313
S1AP_TMOUT_ s1InitialContextSet up
The Initial Context Setup Request message is not received after the Initial UE message is sent to the MME.
When the
timS1InitialContextSetup message is received due to the timer termination while waiting to receive the Initial Context Setup Request message after the Initial UE message is sent to the MME
790 0X0316
S1AP_TMOUT_ The Path Switch Request Acknowledge message is not received after the Path Switch Request message is sent to the MME.
When the timS1PathSwitch message is received due to the timer termination while waiting to receive the Path Switch Request Acknowledge message after the Path Switch Request message is sent to the MME
s1PathSwitch
792 0X0318
S1AP_TMOUT_ The UE Context Release Command message from the MME is not received because the handover is complete after the Handover Command message is received from the MME.
When the timS1RelocOverall message is received due to the timer termination while waiting to receive the UE Context Release Command message from the MME after the Handover Command message is received from the MME
s1RelocOverall
794 0x031A
S1AP_TMOUT_ s1MMEStatusTrans fer
The MME Status Transfer message is not received after the eNB Status Transfer message is sent to the MME.
When the timer ends while waiting for the MME Status Transfer message after the eNB Status Transfer message is sent to the MME
804 0x0324
X2AP_TMOUT_ The UE Context Release message is not received from the Target eNB because the handover is complete after the Handover Acknowledge message is received from the Target eNB.
When the timX2RelocOverall message is received due to the timer termination while waiting to receive the UE Context Release message after the Handover Acknowledge message is received from the target eNB x2RelocOverall
805 0x0325
X2AP_TMOUT_ x2SNStatusTransfe r
The MME Status Transfer message is not received after the eNB Status Transfer message is sent to the MME.
When the timer ends while waiting for the MME Status Transfer message after the eNB Status Transfer message is sent to the MME
Value Call Release
Cause Description Collection Time
DEC HEX
816 0X0330
RRC_TMOUT_ internalResourceSe tup
The response message is not received after the SetupReqe message is sent for setting the resource for the internal protocol blocks of the eNB.
When the
timInternalResourceSetup message is received due to the timer termination while waiting to receive the response after the SetupReq message is sent to assign resources to the protocol blocks within the eNB
- SB2DB state: Initial Context Setup Failure
- DB2DBScomplete state: UE Context Release Request, E_RAB Setup Response
- DB2DBMcomplete state: UE Context Release Request, E_RAB Modify Response
- DB2DBRfail state: E_RAB Release Response
- PHYREcomplete state: UE Context Release Request - INTERprepare_T state: Handover Failure 818 0X0332 RRC_TMOUT_ internalSecurityCon trol
After sending the msgCpdcpSecurityContr ol message to the PDCB, cannot receive the msgCpdcpSecurityContr olSuccess message
When receiving the timInternalSecurityControl message because the timer is ended that waits until the msgCpdcpSecurityControlSucces s message is received after sending the
msgCpdcpSecurityControl message to the PDCB
- SB2DBint state-SB2DBciph state
820 0X0334
RRC_TMOUT_ internalForwarding PathSetup
During Handover, after sending the
msgCgtpSetupReq message to the GTPB for setting uplink and downlink path, cannot receive the
msgCgtpSetupCnf message
During Handover, when the timInternalForwardingPathSetup message is received because the timer is ended that waits until the msgCgtpSetupCnf message is received after sending the msgCgtpSetupReq message to GTPB for setting the uplink, downlink path 821 0X0335 RRC_TMOUT_ internalReestablish Control The msgCrlcControlSuccess or msgCpdcpControlSucces s is not received after the msgCrlcControl,
msgCpdcpControl message is sent for RLC, PDCP reestablishment during inter eNB HO.
When the
timInternalReestablishControl message is received due to the timer termination while waiting to receive the
msgCrlcControlSuccess or msgCpdcpControlSuccess message after the msgCrlcControl or msgCpdcpControl message is sent for RLC, PDCP
reestablishment during inter eNB HO
Value Call Release
Cause Description Collection Time
DEC HEX 822 0X0336 RRC_TMOUT_ internalBufferFlush The msgCpdcpBufferFlushCn f message is not received after the msgCpdcpBufferFlush message is sent to the PDCB during handover.
When the timInternalBufferFlush message is received due to the timer termination while waiting to receive the
msgCpdcpBufferFlushCnf message after the
msgCpdcpBufferFlush message is sent to the PDCB during handover
823 0X0337 RRC_TMOUT_ internalDataTransfe rStart The msgCpdcpControlSucces s message is not received after the msgCpdcpControl message is sent.
When the
timInternalDataTransferStart message is received due to the timer termination while waiting to receive the
msgCpdcpControlSuccess message after the
msgCpdcpControl message is sent
- INCELLresume state: key refreshing
- INTRAresume state: Intra Cell handover
- INTERstart_T state: Inter eNB handover
- REESTresume1 state: Reestablish
833 0X0341 RRC_USER_INAC
TIVITY UE is in inactive status.
When the
msgCmacPhyUserInactivityInd message is received from the MACB.
834 0X0342
RRC_ARQ_MAX_ RE_
TRANSMISSION
After sending only as much as the RLC Max retransmission count, the UE status does not become active for a certain period of time.
When the timer ends while running the
timInternaReestablshTimeToWait timer after the
msgCrlcMaxRetransInd message is received from the RLCB 835 0X0343 RRC_RADIO_LINK
_ FAILURE
The radio link with the UE failed.
The MAC notifies the ECCB of the possible release of the uplink
Value Call Release
Cause Description Collection Time
DEC HEX
The MAC notifies the ECCB of the possible release of the uplink radio link with the UE if it fails to receive the HARQ-ACK/NACK 200 times or more
consecutively for the downlink data. If the ECCB is notified by the MAC of being InSync again (HARQ-ACK/NACK received 20 times), or if it fails to receive the RRC Connection Re-establishment Request from the UE, the call is released after a time-out (default: 5 seconds).
radio link with the UE if it fails to receive the HARQ-ACK/NACK 200 times or more consecutively for the downlink data
(msgCmacPhyOutOfSynchInd). If the ECCB is notified by the MAC of being InSync again (HARQ-ACK/NACK received 20 times), or if it fails to receive the RRC Connection Re-establishment Request from the UE, the call is released after a time-out (default: 5 seconds, timInternaReestablshTimeToWait) . 838 0X0346 RRC_REEST_FAIL _ INVALID_ STATE The RRC Connection Reestablishment Request message is received in the invalid state.
When the RRC Connection Reestablishment Request message is received by the incorrect state (SB2DB state), then the RRC Connection Reestablishment Reject message is sent 840 0X0348 S1AP_RCV_S1_ UECTXTRELEASE CMD_ ABNORMAL_STAT E
The UE Context Release Command is received in the unexpected abnormal state (the cause in the message: normal release, detach, successful handover). The eNB triggers the cause when it receives the UE Context Release Command message including ‘normal release’ in a state that does not involve the Initial Context Setup procedure.
When the cause of the UE Context Release Command received from the MME is: normal_release, detach or successful_handover while the procedure with the MME is not complete 841 0X0349 RRC_RCV_RESET _ REQUEST_FROM _ECMB
The call is released after the Reset Request message is received from the ECMB block.
When the Reset Request message is received from the ECMB block.
842 0X034A
S1AP_RCV_S1_R ESET_
FROM_MME
The call is released by receiving the Reset message from the MME.
When the Reset message is received from the MME
844 0X034C
S1AP_S1_SCTP_ OUT_OF_SERVIC E
The call is released after the S1 Association changes to ‘out of service.’
When the S1 status in the msgCsctpStatusInd message received from the SCTP is ‘out_of_service’
845 0X034D
RRC_RCV_CELL_ RELEASE_IND_FR OM_ ECMB
The call is released after the Cell Release Ind message is received
- When the Cell Release Ind is received from the ECMB block due to the CPRI failure
Value Call Release
Cause Description Collection Time
DEC HEX
from the ECMB block. - When the Cell Release Ind is received from the ECMB block due to the DSP failure
846 0x34E
RRC_DSP_AUDIT _RLC_
CALL_RELEASE
The call remains in the ECCB and MAC, but not in the RLC. This creates a resource mismatch and the call is released.
When the call remains in the ECCB and MAC, but not in the RLC when the msgCdspResourceNotification message is received 847 0x34F RRC_DSP_AUDIT _MAC_ CALL_RELEASE
The call remains in the ECCB and RLC, but not in the MAC. This creates a resource mismatch and the call is released.
When the call remains in the ECCB and RLC, but not in the MAC when the
msgCdspResourceNotification message is received 848 0x350 RRC_DSP_AUDIT _RLC_ MAC_CALL_RELE ASE
The call is cancelled due to the resource
mismatch, because the ECCB has remaining calls but the RLC and the MAC have no call remaining.
When the call remains in the ECCB, but not in the RLC and MAC when the
msgCdspResourceNotification message is received 849 0x351 RRC_SEC_ALGO RITHMS_COMBIN ATION_INVALID
The security algorithm value is received in the Initial Context Setup Request, S1 Handover Request, X2 Handover Request, and S1 UE Context Modification message. The ciphering algorithm should have the null algorithm value if the integrity algorithm supports the null
algorithm. Otherwise, the call is released.
When the ciphering algorithm does not have the null algorithm value even if the integrity algorithm supports the null algorithm 851 0x353 ECCB_RELEASE_ DUE_ TO_ENB_GENERA TED_ REASON
The call is released due to the internal cause of the eNB.
When the relcallall command is executed
875 0X036B RRM_MAX_DRB_ COUNT_ OVER
If calls are generated more than the number of DRB that can be accommodated by cell, they are rejected by CAC.
When DRB ID and LOCH ID are assigned after the Initial Context Setup Request or E-RAB Setup Request message is received
876 0X036C RRM_QOSCAC_F AIL
If calls with the QoS that cannot be
accommodated by cell, they are rejected by CAC.
When the permission is checked to allow new calls after the Rrc Connection Request or Handover Request message is received.
880 0X0370 RRM_RBID_FULL
If DRB is generated exceeding the MAX_DRB or MAX_LOGH per call, DRB ID and LOCH ID cannot be assigned.
When DRB ID and LOCH ID are assigned after the Initial Context Setup Request or E-RAB Setup Request message is received
