Security Level:
Introduction to LTE
Feature 2.0
ISSMS 4.0
www.huawei.com
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1. LTE Random Access Algorithm
2. LTE Handover Algorithm
3. LTE Power Control Algorithm
4. LTE ICIC Algorithm
5. LTE Scheduling Algorithm
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Access in LTE

Definition

In LTE system, access refers to the process of establishing a connection from UE
to eNodeB and MME.

Access Procedure Overview
When a UE needs to establish a connection with the network for any purpose (for
example, service request, location update, or paging), the access procedure is
performed. The generic procedure is as follows:
1.
The UE performs random access.
2.
Signaling connections between the UE and the MME are established. The connections are an
RRC connection and a dedicated S1 connection.
3.
If the connection is for the purpose of a service request, the MME will then instruct the eNodeB
to establish an E-RAB. The MME establishes, modifies and releases the bearer through radio
bearer management.
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Access Procedure (Paging)

Major Functions
 The UE requests to access：the system allocates
a random access channel. The result is uplink
synchronization and dedicated resources allocated.
 Signaling connections contains RRC connection
and dedicated S1 connection. RRC connection is
established upon the request from the UE. Then,
the eNodeB establishes dedicated S1 connection
between eNodeB and MME. Once the dedicated
S1 connection is established, there is a complete
signaling pathway from the UE to the MME.
 The E-RAB establishment creates radio bearers.
Key connections are SRB2 (NAS signaling) and
DRBs (user plane data).
 Releasing signaling connections involves
releasing both the RRC connection and the
dedicated S1 connection. RRC connection release
indicates release of the RRC connection and all
radio bearers. Release may be triggered by either
the eNodeB or the MME.
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Access – Radio Bearers

Radio bearers are classified
into SRBs and DRBs.

Three SRBs

SRB0 carries RRC messages before RRC
connections established. It is transmitted
on CCCH and uses TM at the RLC layer.

SRB1 carries RRC messages and also
carries NAS messages before SRB2 is
established. It is transmitted on DCCH and
uses AM at the RLC layer.

SRB2 carries NAS messages, is
transmitted on DCCH and uses AM on the
RLC layer.
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Complete Access Procedure
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Random Access Scenarios
Random access is performed in the following 5 scenarios:
Initial access
from RRC_IDLE
Initial access1.from
RRC_IDLE
2. Initial access after RLF (Radio Link Failure)
Initial access3.after
radio link failure
Handover (HO)
Handover (HO)
4. Arrival of DL data during
but UL nonArrival of DLRRC_CONNECTED
data during RRC_CONNECTED
but UL nonsynchronization
synchronization
5. Arrival of UL data during
5. Arrival of ULRRC_CONNECTED
data during RRC_CONNECTED
but UL nonbut UL nonsynchronization
synchronization
1.
2.
3.
4.
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Random Access Types
Depending on whether contention is introduced, the random access procedure
can be categorized into contention based random access and non-contentionbased random access:
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Random Access Procedure
contention-based and non-contention-based.
1) Non-contention
UE
2) Contention
UE
eNB
1
0
eNB
Random Access Preamble
RA Preamble assignment
Random Access Response
Random Access Preamble
1
3
2
2
Scheduled Transmission
Random Access Response
Contention Resolution
4
Major differences between contention and non-contention RA procedures:

In contention-based RA, preambles are generated by UEs. Preambles from different UEs may
conflict, and the eNodeB performs contention resolution for UE access. Initial connection uses
the contention-based RA procedure.

In non-contention-based RA, the eNodeB allocates preambles to UEs, so there is no conflict
between UEs.
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Concepts-RA Preamble
An RA preamble is a pulse. In the time domain, it includes TCP (duration of a CP) and TSEQ (duration
of a preamble sequence). In the frequency domain, it has six Resource Blocks (RBs).
CP
TCP
Sequence
TSEQ
 In the frequency domain, a preamble uses the bandwidth for six RBs, that is, 6 x 12 x 15 = 1.08 MHz.
Frequencies to be used are configured by the upper layer.
 In the time domain, the time duration is determined by the preamble format. Different starting
subframes are set for PRACHs according to the 3GPP protocol.
 The RA preamble has five formats, which are applicable to cells in various radius specifications. The
UE can automatically select preamble formats according to the cell radius.
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Cyclic Prefix
•The long CP in preamble formats 1 & 3
assists with large cell range in terms of
increasing timing uncertainty tolerance.
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RA Preamble Generation
 The requirements on the sequence comprising the preamble are two-fold: good correlation
properties to allow precise arrival time estimation and low correlation with other preambles to
suppress interference from other mobiles. A sequence that has ideal such properties is the
Zadoff-Chu sequence (root sequence).
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RA Preamble Sequence Generation

The preamble sequence is defined by a cyclic shift of the Zadoff-Chu (ZC) sequence. The ZC
sequence logical index is determined by RootSequenceIdx, with a value ranging from 0 to 837. The
number of digits for cyclic shifts is determined

These 64 RA preamble sequences are classified into two categories: contention-based RA preamble
sequences and dedicated preamble sequences for non-contention-based RA. The RA preamble
sequences are classified into Group A and Group B, to reduce the average collision probability of
UEs.

According to statistics, the eNodeB adjusts the classification of dedicated preamble sequence group
and the RA sequence group. The RA preamble group A and RA preamble group B are allocated in
the proportion of 1:1.

When the Msg3 to be transmitted by the UE is in small size, RA-Preamble Group A is selected,
implicitly indicating that the quality of radio channels is poor

When the Msg3 to be transmitted by the UE is in large size, RA-Preamble Group B is selected,
implicitly indicating that the quality of radio channels is good.
Dedicated Preamble
Sequence
Random Access
Preamble
Sequence
Group B: Large Msg3, indicating
good radio channel quality
No.
Group A: Small Msg3, indicating
poor radio channel quality.
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Key Parameters
ID
Name
Description
Range
Default Value
MML
RootSequ
enceIdx
Root
sequence
index
Indicates the logical root sequence index, which is
used to derive the preamble sequence. Each
logical root sequence corresponds to a physical
root sequence. For the mapping between logical
root sequences and physical root sequences, see
3GPP TS 36.211.
0~837
None
ADD CELL
MOD CELL
LST CELL
DSP CELL
HighSpee
dFlag
High speed
flag
Indicates whether the cell supports UE with high
mobility.
LOW_SPEED,
HIGH_SPEED,
ULTRA_HIGH
_SPEED
LOW_SPEED
The same as
above
Preamble
Fmt
Preamble
format
Indicates the preamble format used in the cell. For
details, see 3GPP TS 36.211.
0, 1, 2, 3, 4
0
The same as
above
CellRadius
Cell Radius
Indicates the radius of the cell.
1~100000
10000m
The same as
above
Depend on the network
planning
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1. LTE Random Access Algorithm
2. LTE Handover Algorithm
3. LTE Power Control Algorithm
4. LTE ICIC Algorithm
5. LTE Scheduling Algorithm
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Handover in LTE

Objectives

The eNodeB sends the measurement configuration to a UE, and the UE
performs measurements and completes the handover procedure under the
control of the eNodeB to maintain seamless service.

Triggers for Handover in LTE

Coverage: Coverage-based handover connects a moving UE to the cell with
the best signal quality at any given moment, to guarantee that calls are not
dropped during mobility. (Huawei eRAN2.0 currently supports coverage-
based handover only.)

Load: Load-based handover transfers UEs from a heavily loaded or
congested cell to a less loaded cell, to maximize use of system resources.
(Not supported at present)

Type of service: Cells which support high speed data services transfer UEs
with only voice services to other RATs. (Not supported at present)
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Types of Handover in LTE

Intra-frequency Handover

Handover between two LTE cells on the same frequency.

Intra-frequency handovers are triggered by UE measurements. As a UE moves from its serving
cell to a neighboring cell on the same frequency, it detects that signal quality is higher in the
neighboring cell, and this triggers a coverage-based handover.

Inter-frequency Handover

Handover between two LTE cells on different frequencies.

Inter-frequency measurements are triggered by UE measurements. As a UE moves from its
serving cell to a neighboring cell on a different frequency, when signal quality in the serving cell
drops below a certain threshold, this triggers coverage-based inter-frequency measurements.

Inter-RAT Handover

Handover from LTE cells to GSM/WCDMA/TD-SCDMA/CDMA2000 cells.

Inter-RAT measurements are triggered by UE measurements. As a UE moves out of the area
covered by the LTE system, when signal quality in the serving cell drops below a certain
threshold, this triggers coverage-based inter-RAT measurements.
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Event-Triggered Reporting in LTE

Events

Event A1: Signal quality in the serving cell is above a threshold. When a UE reports that
the serving cell meets the triggering condition, the eNodeB stops inter-frequency or interRAT measurements.

Event A2: Signal quality in the serving cell is below a threshold. When a UE reports that
the serving cell meets the triggering condition, the eNodeB starts inter-frequency or interRAT measurements.

Event A3: Signal quality in intra-frequency neighboring cells is higher than that in the
serving cell. When a UE reports this event, the eNodeB sends an intra-frequency
handover request.

Event A4: Signal quality in inter-frequency neighboring cells is above a threshold. When a
UE reports this event, the eNodeB sends an inter-frequency handover request.

Event B1: Signal quality in inter-RAT neighboring cells is above a threshold. When a UE
reports this event, the eNodeB sends an inter-RAT handover request.

Reporting

Event-triggered periodic reporting
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Complete LTE Handover Process

Three Phases of Handover




Handover measurement: UEs perform
measurements, which are triggered as
described in the previous slide.
Handover decision: Based on
measurement reports from UEs, the
eNodeB decides whether to initiate
handovers.
Handover execution: The handover
procedure is executed under the control
of the eNodeB.
Note
 This presentation uses the common type intrafrequency handover for example.
 Inter-frequency and inter-RAT handover
procedures are similar.
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Coverage-Based Intra-Frequency Handover: IntraFrequency Measurement


Entering/Leaving Conditions for Event A3

Entering condition:

Leaving condition:
Parameters





Mn and Ms are the measurement results of the
neighboring and serving cells, respectively.
Ofn and Ofs are the frequency specific offsets for
the neighboring and serving cells, respectively.
Ocn and Ocs are the cell specific offsets for the

neighboring and serving cells, respectively.
Hys is the hysteresis for event A3.
Off is the offset for event A3.

Measurement Quantity
 RSRP, RSRQ, or both
Measurement Reporting
 Event-triggered periodic reporting
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Coverage-Based Intra-Frequency Handover:
Decision and Execution

Decision
1.
The eNodeB generates a list of candidate cells that meet the condition for event A3
based on UE measurement reports.
2.
It then screens the list of candidate cells. Where measurement results are identical,
intra-eNodeB cells are prioritized over inter-eNodeB cells.

Execution
The eNodeB triggers a handover to the target cell with the best signal quality.
There are four possible scenarios:




Inter-eNodeB intra-MME handover in the presence of X2. Signaling messages and
packet data are transmitted over the X2 interface between the eNodeBs.
Inter-eNodeB intra-MME handover in the absence of X2. Signaling messages and
packet data are transmitted over the S1 interface.
Inter-eNodeB inter-MME handover in the presence of X2. Signaling messages are
transmitted over the S1 interface and EPC, and packet data is forwarded over the X2
interface.
Inter-eNodeB inter-MME handover in the absence of X2. Signaling messages and
packet data are transmitted over the S1 interface and EPC.
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Handover Procedure over X2 Interface
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Handover Procedure over S1 Interface
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Handover Procedure over S1 Interface (Cont’d)
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Inter-Cell Intra-eNodeB Handover Procedure
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Coverage based Handover - Key Parameters (1)
ID
Name
Description
Recomm
Range
MML
ended
Value
HoAlgSwitch
HoAlgSwitch
This parameter is Bit field type, indicate what kind
of coverage based handover algorithms are
enabled.
INTRAFRE
QHOA3TRI
GQUAN
A3
measurement
trigger
quantity
Indicates the quantity used to evaluate the
triggering condition for the intra-frequency
handover event. The quantity can be RSRP or
RSRQ.
QoffsetFreq
Intra
Frequency
offset
Indicates the specific frequency offset of the
serving cell. This parameter is contained in the
intra-frequency measurement control information
and is related to the handover difficulty between the
serving cell and the neighboring cell. For details,
see 3GPP TS 36.331.
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IntraFreqHoSwitch,
InterFreqHoSwitch,
CDMA1XRTTHoSwitch,
CDMAHRPDHoSwitch,
GERANHoSwitch,
UTRANHoSwitch,
GERANNotNACCSwitch,
GERANNACCSwitch,
CDMAOMTSwitch
IntraFreq
HoSwitch
MOD
ENODEBALG
OSWITCH
LST
ENODEBALG
OSWITCH
RSRP, RSRQ
RSRP
MOD
INTRARATHO
LST
INTRARATHO
-24, -22, -20, -18, -16, -14, 12, -10, -8, -6, -5, -4, -3, -2,
-1, 0, 1, 2, 3, 4, 5, 6, 8, 10,
12, 14, 16, 18, 20, 22, 24
(dB)
0 (dB)
ADD CELL
MOD CELL
LST CELL
DSP CELL
Page 26
Coverage based Handover - Key Parameters (2)
ID
Name
Description
Recommen
Range
MML
ded Value
IntraFreqHoA
3TimeToTrig
Intrafreq
handover time
to trigger
Indicates the time-to-trigger for intra-frequency
handover event A3.
When detecting that the signal quality in the serving
cell and that in at least one neighboring cell meet the
entering condition, the UE does not send a
measurement report to the eNodeB immediately.
Instead, the UE sends a report only when the signal
quality continuously meets the entering condition
during the time-to-trigger.
0ms, 40ms,
64ms, 80ms,
100ms, 128ms,
160ms, 256ms,
320ms, 512ms,
480ms, 640ms,
1024ms,
1280ms,
2560ms,
5120ms
640ms
EutranFilterC
oeffRSRP
EUTRAN
RSRP filter
coefficient
Indicates the L3 filtering coefficient used for RSRP in
E-UTRAN measurements.
A great value of this parameter indicates a strong
smoothing effect and a high anti-fast-fading capability,
but a low signal change tracing capability. For details,
see 3GPP TS 36.331.
FC0, FC1, FC2,
FC3, FC4, FC5,
FC6, FC7, FC8,
FC9, FC11,
FC13, FC15,
FC17, FC19
FC6
IntraFreqHoA
3Hyst
Intrafreq
handover
hysteresis
Indicates the hysteresis to be used in the triggering
condition for the intra-frequency handover event. This
parameter helps reduce the number of times the
event is triggered because of radio signal fluctuation.
For details, see 3GPP TS 36.331. Actual value = GUI
value x 0.5
0~30 (* 0.5dB)
4 (* 0.5dB)
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MOD
INTRARATHOQCI
LST
INTRARATHOQCI
MOD
HOMEASCOMM
LST
HOMEASCOMM
MOD
INTRARATHOQCI
LST
INTRARATHOQCI
Coverage based Handover - Key Parameters (3)
ID
Name
Description
Range
Recommen
MML
ded Value
IntraFreqHoA3O
ffset
Intrafreq
handover
offset
Indicates the quality offset of the
neighboring cell over the serving cell to
be used in the triggering condition of the
intra-frequency handover event. The
larger the value of this parameter is, the
better quality the neighboring cell should
have before the handover is triggered.
For details, see 3GPP TS 36.331.
Actual value = GUI value x 0.5
-30~30 (* 0.5dB)
4 (* 0.5dB)
CellIndividualOff
set
Cell individual
offset
Indicates the offset of the intrafrequency neighboring cell. This
parameter is used to control the
reporting of intra-frequency
measurement events. The larger the
value of this parameter, the more easily
the intra-frequency measurement events
are reported. For details, see 3GPP TS
36.331.
-24, -22, -20, -18,
-16, -14, -12, -10,
-8, -6, -5, -4, -3, 2, -1, 0, 1, 2, 3, 4,
5, 6, 8, 10, 12,
14, 16, 18, 20,
22, 24 (dB)
0 (dB)
MOD INTRARATHOQCI
LST INTRARATHOQCI
ADD
EUTRANINTRAFREQNCELL
MOD
EUTRANINTRAFREQNCELL
LST
EUTRANINTRAFREQNCELL
Some handover parameters may
need to be optimized based on radio
environment
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1. LTE Random Access Algorithm
2. LTE Handover Algorithm
3. LTE Power Control Algorithm
4. LTE ICIC Algorithm
5. LTE Scheduling Algorithm
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Power Control: Function and Purpose

Function

LTE power control is used to compensate for path loss on channels and shadow
fading, and reduces inter-cell interference.

Power control is implemented on both the eNodeB and the UE. There are uplink
and downlink power control.


Purposes
Ensuring the service quality

Power control is performed to adjust the transmit power so that the service quality just meets
the requirement for the BLER, thereby avoiding wastes of power

Reducing the interference

The interference with a cell mainly comes from its neighboring cells. Power control reduce the
interference from the neighboring cells.

Lowering power consumption

Uplink power control lowers the power consumption of UEs, and downlink power control lowers
the power consumption of eNodeBs. Expanding coverage and capacity
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Downlink Power Control


Signals and Channels

Cell-specific reference signal

Synchronization signal

Physical Broadcast Channel (PBCH)

Physical Control Format Indicator Channel (PCFICH)

Physical Downlink Control Channel (PDCCH)

Physical Downlink Shared Channel (PDSCH)

Physical HARQ Indication Channel (PHICH)
Downlink Power Control Policies


Fixed power assignment: Users set a fixed power level for reference signal (RS),
synchronization signal, PBCH, and PCFICH, as well as PDCCH and PDSCH,
which carry common cell information.
Dynamic power control: Dynamic power control helps meet QoS requirements,
reduce interference, improve cell coverage, and increase cell capacity. It is
applicable to PHICH, as well as PDCCH and PDSCH, which carry UE dedicated
information.
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Calculating the PDSCH power


The PDSCH uses AMC and HARQ, so there is no strict requirement about PDSCH power control in
protocol.
PDSCH power control is classified into power control for dynamic scheduling and for semi-persistent
scheduling. For non-VoIP and hybrid services, with dynamic scheduling, there is (uniform/nonuniform) power control, or two power levels can be set (with ICIC). VoIP services, with semipersistent scheduling, use closed-loop power control.
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Calculating the PDSCH power
 Sample of calculating for 2*20W, 10MHz, RS power = 18dBm, PA=-3dB, PB=1
Then:
EA = PA + ERS = -3dB + 18dBm =
15dBm
EB = PB (in dB)+ PA + ERS = 0dB -3dB +
18dBm = 15dBm
For the symbol 1,2,3,5,6, There are 600 EA in 50 RBs (Resource Block), and the
total power can be : 15dBm * 600 = 31.6228 (mw) *600 = 18.9737 (W)
For the symbol 0,4, There are 100 ERS and 400 EB in 50 RBs (Resource Block), and
the total power can be : 18dBm * 100 + 15dBm * 400 = 63.0957 (mw)*100 +
31.6228 (mw) *400 = 18.9587 (W)
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Downlink Power Control - Key Parameters (1)
ID
Name
Description
Range
Recommen
MML
ded Value
ReferenceSignalPwr
Reference
Signal Power
Indicates the reference signal power of
the cell. For details, see 3GPP TS
36.213.
[-60, 50]
18.2
MOD PDSCHCFG
LST PDSCHCFG
Pb
PB
Indicates the power factor ratio
demonstration of the EPRE on the
PDSCH. This parameter, together with
the antenna port, determines the value
of the power factor ratio. For details,
see 3GPP TS 36.213.
0~3
1
LST PDSCHCFG
MOD PDSCHCFG
PaPcOff
PaPcOff
Indicates the PA when the power
control for the PDSCH is disabled, the
downlink ICIC is disabled, and the even
power distribution is used for the
PDSCH.
-6,-4.77,-3,
-1.77,0,1,2,3
-3
LST
CELLDLPCPDSCHPA
MOD
CELLDLPCPDSCHPA
PaCenterUe
PaCenterUe
Indicates the PA value of the cell center
UEs , when the DL ICIC is enabled.
-6,-4.77,-3,
-1.77,0,1,2,3
-6
LST CELLDLPCPDSCH
MOD
CELLDLPCPDSCH
PaEdgeUe
PaEdgeUe
Indicates the PA value of the cell edge
UEs , when the DL ICIC is enabled.
-6,-4.77,-3,
-1.77,0,1,2,3
-1.77
LST CELLDLPCPDSCH
MOD
CELLDLPCPDSCH
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Downlink Power Control - Key Parameters (2)
ID
Name
Description
Range
Recommended
MML
Value
PbchPwr
PBCH Power
Indicates the power offset of the cell
PBCH channel compared with the
reference signals.
PcfichPwr
Pcfich Power
Indicates the power offset of the cell
PCFICH channel in relation to the
reference signals.
-15.875~15.875
PhichPcOff
PhichPcOff
Indicates the power offset of the
PHICH TX power compared with the
reference signals when the power
control for the PHICH is disabled.
SchPwr
SCH Power
The RSRP/RSRQ threshold of
Event A2. If RSRP is lower than it,
Event A2 start.
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-15.875~15.875
-3dB in normal
scenarios and
peak-rate tests,
or 0 in the tests
on the maximum
cell radius
MOD CELLCHPWRCFG
LST CELLCHPWRCFG
-3dB in normal
scenarios and
peak-rate tests,
or 0 in the tests
on the maximum
cell radius
MOD CELLCHPWRCFG
LST CELLCHPWRCFG
-15~15
0
MOD CELLDLPCPHICH
-15.875~15.875
0
MOD CELLCHPWRCFG
LST CELLCHPWRCFG
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Downlink Power Control - Key Parameters (3)
ID
Name
Description
Range
Recommende
MML
d Value
RaRespPwr
RaResp Power
Indicates the power offset of the
PDSCH between transmitting the
random access response and the
reference signals.
-15.875~15.875
0
MOD CELLCHPWRCFG
LST CELLCHPWRCFG
PagingPwr
Paging Power
Indicates the power offset of the
PDSCH between transmitting the
paging messages and the reference
signals.
-15.875~15.875
0
MOD CELLCHPWRCFG
LST CELLCHPWRCFG
DbchPwr
Dbch Power
Indicates the power offset of
transmitting broadcast signals on the
PDSCH channel compared with that of
the reference signals.
-15.875~15.875
-3 dB in normal
scenarios and
peak-rate tests,
or 0 in the tests
on the
maximum cell
radius
MOD CELLCHPWRCFG
LST CELLCHPWRCFG
PdcchBndPcSw
PdcchBndPcSw
Indicates the switch that is used to
enable and disable power control
applied to the PDCCH carrying
dedicated control information. If this
parameter is set to ON, the PDCCH
power is adjusted dynamically when
the channel quality is extremely good
or bad.
OFF, ON
OFF
MOD CELLDLPCPDCCH
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Downlink Power Control - Key Parameters (4)
ID
Name
Description
Range
Recommende
MML
d Value
DlPcAlgoSwitch
Downlink
Power Control
Algorithm
Switch
Indicates the switch of the DL power
control algorithm.
PdschPcSwitch is the PDSCH power
control switch.
PdschSpsPcSwitch is the switch
corresponding to PDSCH power
control in semi-persistent scheduling
mode.
PhichPcSwitch is the PHICH power
control switch.
PhichInnerLoopPcSwitch is the PHICH
inner-loop power control switch.
PdschNmaxAdjustSwitch is the switch
corresponding to Nmax adjustment for
PDSCH
PdschPcSwitch,
PdschSpsPcSw
itch,
PhichPcSwitch,
PhichInnerLoop
PcSwitch,
PdschNmaxAdj
ustSwitch
PdschPcSwitch
:Off,
PdschSpsPcSw
itch:Off,
PhichPcSwitch:
Off,
PhichInnerLoop
PcSwitch:Off,
PdschNmaxAdj
ustSwitch:Off
MOD CELLALGOSWITCH
Huawei recommends to use the
default values for DL power
allocation
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Uplink Power Control

Power Control of Uplink Signals and Channels

Sounding reference signal

Physical Random Access Channel (PRACH)

Physical Uplink Shared Channel (PUSCH)

Physical Uplink Control Channel (PUCCH)
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Uplink PUSCH Power Control
PPUSCH (i )  min{ PCMAX ,10 log 10 ( M PUSCH (i ))  PO_PUSCH ( j )   ( j )  PL   TF (i )  f (i )}
i
: the ith uplink subframe
PCMAX : maximum transmit power of the UE
M PUSCH (i) : number of resource blocks (RBs) allocated to PUSCH, namely PUSCH bandwidth on the ith subframe
PO_PUSCH ( j )
 ( j)
PL
: target signal power expected by the eNodeB in the reference transport format (TF) of PUSCH
: power compensation factor
: downlink path loss estimated by the UE, calculated using the measured RSRP and cell-specific RS
 TF (i) : power offset between each MCS and the reference MCS
f (i )
: adjustment to the PUSCH power at the UE, calculated based on the TPC information in PDCCH
PO_NOMINAL_PUSCH ( j ) is the PUSCH transmit power expected by the eNodeB during normal PUSCH demodulation.
PO_UE_PUSCH( j )
is the power offset of the UE relative to PO_NOMINAL_PUSCH ( j ), reflecting the impact of UE category,
service type and channel quality on the PUSCH transmit power at the UE.
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PUSCH Power Control

eNB updates Po_nominal according to the IN_own( interference level of current
cell ) and OI(overload information) in open loop power control.
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Uplink PUCCH Power Control
PPUCCH i   min PCMAX , P0_PUCCH  PL  hnCQI , nHARQ   F_PUCCH F   g i 
i
: the ith uplink subframe
PCMAX : maximum transmit power of the UE
PO_PUCCH : signal power expected by the eNodeB
: downlink path loss estimated by the UE, calculated using the measured RSRP and cell-
PL
specific RS
hnCQI , nHARQ  : determined by the PUCCH format. n
CQI is the number of information bits in CQI; n HARQ the
number in HARQ. It reflects the effect of CQI and HARQ bit counts on power.
F_PUCCH ( F ) : effect of the PUCCH transport format on the transmit power.
g (i )
PO_NOMINAL_PUCCH
PO_UE_PUCCH
: adjustment to the PUCCH power at the UE, calculated based on TPC information on PDCCH
is the target signal power expected by the eNodeB for the reference transport format.
is the power offset of the UE relative to the cell-level PO_NOMINAL_PUCCH , reflecting the impact of
UE category, service type and channel quality on the PUCCH transmit power at the UE.
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Uplink PRACH Power Control
PPRACH  min PCMAX , P0_pre  PL   preamble  ( N pre  1)   step 
PCMAX : maximum transmit power of the UE
PO_pre : target power expected by the eNodeB when the PRACH preamble format is 0 and the requirements for
the preamble detection performance are met.
PL
: downlink path loss estimated by the UE, calculated using the measured RSRP and cell-specific RS
 preamble : power offset for the current preamble format relative to preamble format 0
N pre
: total number of preambles sent by UE during RA process. It cannot exceed the maximum number.
 step
: preamble power ramping step
PL
Process Outline

P
O_pre
step
The eNodeB sets the expected receive power for
the initial
preamble. The UE calculates path loss
based on RS power. The eNodeB sends
and
to the UE through system information.
The UE calculates the correct RA preamble power. If an RA attempt receives no response, the UE
increases PRACH power by one step for the next attempt.
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Uplink Power Control - Key Parameters (1)
ID
Name
Desciption
Recommend
Range
MML
ed Value
UlPcAlgo
Switch
Uplink Power
Control
Algorithm
Switch
Indicates the switch of the UL power control
algorithm.
CloseLoopSpsSwitch is the switch
corresponding to closed-loop power control in
semi-persistent scheduling mode.
InnerLoopPuschSwitch is the switch
corresponding to inner-loop power control in
dynamic scheduling mode.
PhSinrTarUpdateSwitch is the switch
corresponding to PH-based SINR target update
in dynamic scheduling mode.
InnerLoopPucchSwitch is the PUCCH inner-loop
power control switch.
OiSinrTarUpdateSwitch is the switch
corresponding to OI-based SINR target update in
dynamic scheduling mode.
PuschNmaxAdjustSwitch is the switch
corresponding to Nmax adjustment for PUSCH.
CloseLoopS
psSwitch,
InnerLoopPu
schSwitch,
PhSinrTarUp
dateSwitch,
InnerLoopPu
cchSwitch,
OiSinrTarUp
dateSwitch,
PuschNmax
AdjustSwitch
CloseLoopSp
sSwitch: OFF
InnerLoopPus
chSwitch:
OFF
PhSinrTarUpd
ateSwitch:
OFF
InnerLoopPuc
chSwitch: ON
OiSinrTarUpd
ateSwitch:
OFF
PuschNmaxA
djustSwitch:
OFF
MOD
CELLALGOSWI
TCH
Alpha
Alpha
Indicates compensation factor of the path loss. It
is used in the UL power control procedure. For
details, see 3GPP TS 36.213.
0, 0.4, 0.5,
0.6, 0.7, 0.8,
0.9, 1
0.7
MOD
CELLULPCCOM
M
P0Nomina
lPUCCH
P0 Nominal
PUCCH
Indicates the nominal PUCCH P0, which is used
in the UL power control procedure. For details,
see 3GPP TS 36.213-860.
-127~-96
(dBm)
-105 (dBm)
MOD
CELLULPCCOM
M
OFF
CELLALG
OSWITCH
ULPCALGOS
Indicates the switch for updating the inner loop
power
control
based
on the OI in
HUAWEIWITCH(OiSinr
TECHNOLOGIES
CO.,
LTD. for the PUSCH
Huawei
Confidential
TarUpdateSwit
dynamic
OFF ON
Page 43
MOD
CELLALGOSWI
TCH
Uplink Power Control - Key Parameters (2)
ID
Name
Desciption
Recom
Range
MML
mended
Value
P0NominalPUSCH
P0 Nominal PUSCH
Indicates the nominal
PUSCH P0, which is used
in the UL power control
procedure. For details, see
3GPP TS 36.213-860.
-126~24
(dBm)
-67
(dBm)
MOD CELLULPCCOMM
DeltaMcsEnabled
DELTAMCSENABLED
Indicates whether the
transmit power of the UE is
adjusted according to the
difference between MCSs.
Disable
Enable
Disable
MOD CELLULPCDEDIC
LST CELLULPCDEDIC
PSRSOFFSETDEL
TAMCSDISABLE
PSrsOffsetDeltaMcsDis
able
Power boost between
sounding and PUSCH when
DELTAMCSENABLED is
set to disable
-10.5,-9,-7.5,
-6,-4.5,-3,
-1.5,0,1.5,
3,4.5,6,
7.5,9,
10.5,12 (dB)
-3(dB)
MOD CELLULPCDEDIC
LST CELLULPCDEDIC
PSrsOffsetDeltaMc
sEnable
PSRSOFFSETDELTA
MCSENABLE
Power boost between
sounding and PUSCH when
DELTAMCSENABLED is
set to enable
-3,-2,-1, 0,1,2,3, 4,5,6,7,
8,9,10, 11,12
-3(dB)
MOD CELLULPCDEDIC
LST CELLULPCDEDIC
Huawei recommends to use
the default values
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1. LTE Random Access Algorithm
2. LTE Handover Algorithm
3. LTE Power Control Algorithm
4. LTE ICIC Algorithm
5. LTE Scheduling Algorithm
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Inter-Cell Interference Coordination (ICIC)

Interference in LTE

Within a single cell, the RBs used by all UEs are orthogonal, so intra-cell interference is negligible.

All cells can use the entire system bandwidth, so inter-cell interference is obvious. In particular, cell
edge users (CEUs) are affected by severe interference from neighboring cells.

Two Solutions to Reduce Inter-Cell Interference

IRC: combines receiving antennas to combat strong colored inter-cell interference. It operates at
the physical layer. For details, see the MIMO Feature Parameter Description.

ICIC: reduces inter-cell interference by collaborating with scheduling and power control. It operates
at the MAC layer. The principle is that the eNodeB limits the time-frequency and power resources it
can allocate to cell center users (CCUs) and CEUs. CEUs experiencing significant interference
from a neighboring cell are allocated resources orthogonal to that cell, or CEUs are scheduled at
staggered times. In this way, inter-cell interference is minimized, throughput is increased for CEUs,
and coverage is improved.

Types of ICIC

Dynamic ICIC and static ICIC: The classification depends on the need for dynamic adjustments of
resources on edge bands.

Uplink ICIC and downlink ICIC: are both implemented by the eNodeB.
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Downlink Initial Band Division and Adjustment

Initial Band Division in Downlink Static ICIC

A hexagon represents one cell. White is central area.

One of three possible ICIC band division schemes is set by
the parameter CELLBANDDIV. Three neighboring cells will
each use a different scheme.
 When the cell edge load is high, more edge bandwidth is assigned.
 When increasing edge bandwidth, the eNodeB evaluates interference from neighboring
cells and performs interference coordination on the neighboring cells causing greatest
interference.
 When the cell edge load is low, the edge bandwidth is reduced.
 When reducing edge bandwidth, the eNodeB removes most recently added bandwidth first.
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UE Type Determination

When UEs access a cell initially, they are CCUs as default. When UEs
access a cell by handover, they are CEUs.

When entering A3 event, that is, the eNodeB receives a measurement
report of RSRP contains both the serving and neighboring cells from this UE,
the UE is treated as a CEU.

When leaving A3 event , that is, the eNodeB receives a measurement report
of RSRP only with the serving cell from this UE, the UE is treated as a CCU .
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ICIC Concept
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Static Downlink ICIC Procedure

During network planning, the operating band in each cell is divided into an edge
band and a center band. Edge bands in neighboring cells are orthogonal.

Downlink ICIC evaluates cell load and determines whether to block RBs. If some
RBs on the center band are blocked, interference on neighboring cells is reduced.

Based on cell load and RSRP reported by UEs, the eNodeB adjusts UE types.
When UEs access a cell initially , they are CCUs as default. When UEs access a
cell by handover, they are CEUs.
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Dynamic Downlink ICIC Procedure

The serving cell adjusts its edge band based on the
following information and informs the scheduler of
the band information:

Band division scheme, as in the network plan

Private ICIC messages from neighboring cells

Target cells for ICIC, determined based on cell information
and interference evaluation. The neighboring cell list is
managed based on private messages and RSRP reported
by UEs.



Results of load evaluations
Based on load evaluations, DL ICIC determines
whether or not to block RBs. If some RBs on the
center band are blocked, interference effects on
neighboring cells are reduced.
Based on the RSRP and evaluated cell load reported
by UEs, the eNodeB adjusts UE types, and
scheduling changes in turn.
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Static Uplink ICIC Procedure



During network planning, the uplink operating band in each cell is divided into an edge
band and a center band. Edge bands in neighboring cells are orthogonal.
Based on RSRP measurement reports from UEs, the eNodeB divides UEs into CEUs
and CCUs, and informs the scheduler.
Neighboring cells continually check themselves for interference. When interference
exceeds the OI threshold, a cell sends an OI message to all neighboring cells. When a
serving cell receives an OI message, it checks its validity and executes the necessary
adjustments.
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Dynamic Uplink ICIC Procedure



Based on RSRP measurement reports from UEs, the eNodeB divides UEs into CEUs and
CCUs, and informs the scheduler.
The eNodeB maps band division information into HII messages and sends them to
neighboring cells (HII target cells). The eNodeB of the serving cell (HII source cell) then
continually adjusts its edge-band bandwidth according to edge-band load and its
neighboring cell list. Then, the eNodeB informs the scheduler.
Neighboring cells continually check themselves for interference. When interference exceeds
the OI threshold, a cell sends an OI message to all neighboring cells. When a serving cell
receives an OI message, it checks its validity and executes the necessary adjustments.
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Intra-eNodeB Time-Domain Uplink ICIC
Procedure



For interference coordination between
different cells on a single eNodeB
When frequency coordination fails to
resolve high interference
Not for TDD mode or handover users
Procedure:

Based on RSRP measurement reports from UEs, the eNodeB divides UEs into CEUs and CCUs, and
informs the scheduler.

Neighboring cell list is managed based on RSRP and HII messages. Intra-eNodeB coordination
covers intra-eNodeB cells on the cell-level neighboring cell list.

Neighboring cells continually check themselves for interference. When interference exceeds the OI
threshold, a cell sends an OI message to all neighboring cells. When a serving cell receives an OI
message, it checks its validity and executes the necessary adjustments.

UE types and neighboring cell information are inputs to the scheduler. The scheduler determines
which neighboring cell is causing the interference, and then decides for each CEU to use either odd
or even sub-frames only.
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ICIC - OI Handling

Overload Indication (OI) – Broadcasted message to all neighboring cells

OI message indicates the interference level caused to an RB

OI message contains: ID of the Source Cell & Interference Indication
(high/medium/low)

Adjust CEUs transmission power
exchange message between
send cell and a group
neighbor cells by
X2 interface
cell 2
cell 3
OI
cell 1
X2
cell 5
Value for the threshold mention in the comments below
cell 4
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ICIC - HII Handling

High Interference Indication (HII) – provides info for the band division

Dynamic adjustment CEUs frequency band

Non-overlapping CEUs frequency band

HII message contains: ID of the Source Cell , ID of the Target Cell &
Interference Indication (high level – edge band; low level – center band)

HII messages – event trigger and periodic modes
HII
cell 2
HII
cell 3
HII
cell 1
exchange message between
two cells by X2 interface
X2
HII
cell 5
HII
cell 4
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ICIC - Key Parameters
ID
Name
Description
Recomm
Range
MML
ended
Value
DlIcicAlgoSwitch
DlIcicAlgoSwitch
Indicates the DL ICIC algorithm switch. There are
four states.
DlIcicSwitch_OFF:Indicates that the DL ICIC
algorithm is disabled.
DlIcicDynamicSwitch_ON:Indicates that the
dynamic DL ICIC algorithm is enabled.
DlIcicStaticSwitch_ON:Indicates that the static DL
ICIC algorithm is enabled.
DlIcicReuse3Switch_ON:Indicates that the DL
ICIC Reuse3 algorithm is enabled. In this case, all
UEs are scheduled on the edge frequency band
defined by the statistic ICIC scheme. That is, all
UEs in one cell use one third of the total frequency
band.
DlIcicSwitch_OF
F_ENUM(),
DlIcicDynamicS
witch_ON_ENU
M(),
DlIcicStaticSwitc
h_ON_ENUM(),
DlIcicReuse3Swi
tch_ON_ENUM()
DlIcicSwit
ch_OFF_
ENUM()
MOD
ENODEBALGOSWI
TCH
LST
ENODEBALGOSWI
TCH
UlicicFreqSwitch
UlIcicFreqSwitch
Indicates the switch that is used to enable and
disable UL ICIC in the frequency domain. When
this switch is set to OFF, UL ICIC in the frequency
domain is disabled in the cells under the eNodeB.
When this switch is set to STATIC, static UL ICIC
in the frequency domain is enabled in the cells
under the eNodeB. When this switch is set to
DYNAMIC, dynamic UL ICIC in the frequency
domain is enabled in the cells under the eNodeB.
{OFF, STATIC,
DYNAMIC}
OFF
MOD
ENODEBALGOSWI
TCH
LST
ENODEBALGOSWI
TCH
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1. LTE Random Access Algorithm
2. LTE Handover Algorithm
3. LTE Power Control Algorithm
4. LTE ICIC Algorithm
5. LTE Scheduling Algorithm
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What Is Scheduling?

Overview

When LTE is using shared channels, time-frequency resources are
dynamically shared. How does the eNodeB allocate resources? Through
scheduling. Scheduling is the process of allocating time-frequency
resources to UEs based on service type, data volume, and channel
quality.


Scheduling for both uplink and downlink is completed at the MAC layer.
Objectives

The objectives of scheduling are to transmit as much data as possible
over good quality connections and maximize capacity, while also meeting
QoS requirements.
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Concepts about Scheduling

Channel Quality

Channel Quality Indicator (CQI). CQI is a downlink quality indicator. CQI is reported by the UEs under
control the of eNodeB. Reports can be periodic, event-triggered, or both.

Signal to Interference plus Noise Ratio (SINR). In downlink scheduling, uplink SINR is the channel quality
indicator. SINR is measured at the physical layer. To make the IBLER for each UE approach the target
IBLER, the eNodeB adjusts SINR based on uplink data ACK/NACK.

QoS
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Scheduling Modes and Policies

Scheduling Modes

Dynamic scheduling. The eNodeB makes a scheduling decision every TTI and informs all UEs
to be scheduled. One TTI is 1 ms.

Semi-persistent scheduling. Within a preset semi-persistent scheduling period (20 ms for the
Huawei eNodeB), a single user will use the same time-frequency resources until they are
released. Semi-persistent scheduling is usually used for services with fixed bit rates, periodic
data arrival and small delays, such as VoIP. This type of scheduling can reduces signaling
overhead.

Scheduling Policies

Huawei eNodeB supports three basic scheduling policies: Max C/I, Round Robin (RR), and
Proportional Fair (PF). It also supports one enhanced policy: Enhanced PF (EPF).

In the basic policies, all services use dynamic scheduling. In EPF, only VoIP uses semipersistent scheduling.

In actual network deployment, EPF is generally used.
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Scheduling types

Frequency-selective scheduling. In DL scheduling, frequency-selective
scheduling allocates continuous subcarriers or RBs to UEs. This technology
requires that the eNodeB have detailed channel quality information. Using subband CQIs, the eNodeB finds good quality resources increasing system utilization
and peak speed of UEs.

Non-frequency-selective scheduling. In DL scheduling, non-frequency-
selective scheduling allocates discrete subcarriers or RBs to UEs. For this mode,
the eNodeB only needs full band CQIs, so signaling overhead is lower. In UL
scheduling, non-frequency-selective scheduling searches within a band from high
to low for continuous usable RBs. When few UEs need to be scheduled in a cell,
frequency-selective scheduling generates many data fragments. Non-frequencyselective scheduling is therefore prioritized.
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Scheduling _Resource Allocation


Resource Allocation Type:

Localized: is propitious to frequency-selective scheduling

Distributed: can bring frequency diversity gain.
PDSCH Resource Allocation Type

Resource allocation type 0:
Based on RBG, bitmap indicates resource allocation.

Resource allocation type 1:
Based on RBG subset, bitmap in subset indicates resource allocation
Couldn’t allocate resource from different RBG subset.

Resource allocation type 2:
Virtual RB map to Physical RB;
Including localized VRB and Distributed VRB.
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Scheduling _Resource Allocation

TYPE 0 : RBG
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Scheduling _Resource Allocation

TYPE 2 based on RB.
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Downlink Scheduling

Overview

Downlink scheduling allocates time-frequency resources in PDSCH to system information or
data transmission.

The scheduler measures the remaining power and calculates resources that can be scheduled.
It then decides scheduling priorities and MCS based on the volume of data waiting in the RLC
layer, the QoS requirements for each bearer, and UE channel quality (CQIs reported by UEs).

Procedure

Scheduling priorities in descending order: VoIP services, control plane data/IMS signaling
messages, data to be retransmitted, and other initially transmitted data services.

The scheduler uses semi-persistent scheduling for VoIP services and dynamic scheduling for
other data.

Control plane data is second in priority only to VoIP. It is dynamically scheduled. Control plane
data includes common control messages and UE level control messages. The scheduling of
IMS signaling messages is consistent with UE level control message processing (SRB1, SRB2).
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Uplink Scheduling

Overview

Uplink scheduling is the allocation of suitable PUSCH resources to the right UE at the right time. EPF
scheduling is the default.

Uplink scheduling begins after a request by the UE. MCS is selected and a specific number of RBs
are allocated based on the current UE channel quality, volume of data to be scheduled, and power
headroom.

During uplink scheduling, UE channel quality is indicated by SINR measured at the physical layer by
the eNodeB; data volume is reported by the UE in its BSR; power headroom is reported by the UE in
its PHR.

Procedure

Scheduling priorities in descending order: VoIP services, control plane data/IMS signaling messages,
data to be retransmitted, and other initially transmitted data services.

The scheduler uses semi-persistent scheduling for VoIP services and dynamic scheduling for other
data.

Control plane data is second in priority only to VoIP. It is dynamically scheduled. Control plane data
includes common control messages and UE level control messages. The scheduling of IMS signaling
messages is consistent with UE level control message processing (SRB1, SRB2).
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Thank you
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