Microsoft PowerPoint - OEO106040 LTE eRAN6.0 Scheduling Feature ISSUE 1

LTE eRAN2.1 Scheduling Feature


www.huawei.com

Copyright © 2013 Huawei Technologies Technologies Co., Ltd. All rights reserved.

Contents 1. Ove Overvie rview w 2. Downlink Scheduling 3. Uplink Scheduling 4. Semi-Persistence Scheduling


Confidential Information of Huawei. No Spreading Without Permission

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1


Scheduling Overview

Scheduling Function: Ensure high spectrum high spectral efficiency while providing the required. Copyright © 2013 Huawei Technologies Technologies Co., Ltd. All rights reserved.

Page2

Scheduling Strategy Scheduling Effect Factor Strategy

Scheduling Priority

Application Scenario

Max C/I

Channel quality

The UE with better channel quality has a higher priority in scheduling.

To verify the maximum system throughput

RR

None

Each UE has equal opportunity to be scheduled.

To verify the upper limit of scheduling fairness

PF

Service rate and channel quality

The UE with a small ratio between the service rate and channel quality has a higher priority in scheduling.

To verify the system throughput and fairness

EPF

Service rate, channel quality, UE capability, and QoS requirement requirement

Intergraded Intergraded priority with service rate, UE category, category, QoS and CQI. CQI.

In operating networks



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Scheduling Scheme Dynamic scheduling • Period: 1ms (per TTI) • Service application: all service Semi-Persistent Scheduling • Period: 20ms (Huawei eNodeB) • Service application: Real time service, etc. VoIP

Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.

Page4

QoS Class Index QCI Type

Priority

Packet Delay Budget

Packet Error Rate

Service Example

1

GBR

2

100ms

10-2

Conversational Voice

2

GBR

4

150ms

10-3

Conversational Voice

3

GBR

3

50ms

10-3

Real time gaming

4

GBR

5

300ms

10-6

Real time video

5

Non GBR 1

100ms

10-6

IMS signaling

6

Non GBR 6

300ms

10-6

Video with buffer

7

Non GBR 7

100ms

10-3

Voice, Video, Interactive Gaming

8

Non GBR 8

300ms

10-6

Video, TCP (HTTP, E-mail, FTP etc)

9

Non GBR 9

300ms

10-6

Video, TCP (HTTP, E-mail, FTP etc)



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Scheduler Introduction Scheduler UE capability QoS (QCI/GBR/AMBR) SINR (uplink) CQI (downlink)

Scheduling in each TTI

QoS management Processing of measurement quantities from PHY

SR/BSR (uplink) Buffer status(downlink)

MCS Scheduling information processing

Dynamic scheduling Priority calculation

PHR (uplink) Tx power (downlink)

Antenna and resource mapping

MCS selection

ACK/NACK Virtual MIMO switch (uplink) MIMO scheme (downlink) Edge frequency band Center frequency band

RLC payload

Semi-persistent scheduling

Resource allocation

ICIC strategy

Retransmission control

The dashed line indicates the optional function.

Functions of MAC layer:

Guarantee system signaling sending

Ensure QoS requirements


Take user differentiation and fairness into account

Maximize the system throughput

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Scheduling Execution DCI info (PDCCH)



DCI info for scheduling 

Resource allocation header: indicate allocation type



Resource assignment block



MCS (Modulation Coding Scheme)



MIMO scheme



NDI( New Data Indication)



HARQ process number



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Contents 1. Overview 2. Downlink Scheduling 3. Uplink Scheduling 4. Semi-Persistence Scheduling


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Contents 2.

Downlink Scheduling 2.1 Scheduling Priority Processing 2.2 MCS Selection & Resource Allocation



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DL Scheduler DL Scheduler

Priority calculation

Channel Quality HARQ feedback

Selected UE

MCS selection

RB number

QoS parameters Resource allocation

UE Capability

MCS/MIMO Every scheduling period


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Scheduling Priority of DL Scheduling Obtain scheduling resource

Control message scheduling

Semi-persistent scheduling Retransmission scheduling

Initial transmission in dynamic scheduling

R e s o u r c e a l l o c a t i o n

End



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Control-Plane Data and IMS Signaling 

Common Control Messages 

Common control message regards to SIBs, paging and RA response message.



If the scheduling indication fails to be delivered due to insufficient PDCCH resources , common control messages are not scheduled in the current TTI.



UE-Level Control Message or IMS Signaling 

SRB0 is delivered in the Contention Resolution message during the random access process, has higher priority then SRB1/SRB2 and IMS signaling



During the DRX dormant period and measurement gap or when the UE has urgent HARQ scheduling, SRB1 and SRB2 cannot be scheduled.



The scheduling of IMS signaling is the same as that of SRB1 and SRB2


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HARQ Retransmission Scheduling

At least 8 TTI



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HARQ Retransmission Scheduling Exception 

HARQ retransmissions cannot be performed for a UE in one of the following states: 









The UE is in a measurement gap or enters a measurement gap The UE enters sleep time in DRX and the HARQ operating status is discontinuous transmission The UE is non-synchronized to the eNodeB or a radio link failure (RLF) occurs System information and IP Multimedia Subsystem (IMS) signaling are already scheduled for the UE in the current TTI Semi-persistent scheduling is performed for the UE in the current TTI.


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Other Initial Service Scheduling

Priority 2 Priority 1



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Other Initial Service Scheduling

Priority 2 Priority 1


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Priority of GBR Service Scheduling 

The priority of GBR service is determined by the following formula:

Pr iorityGBR

=

f (CQI ) × f (delay )



f(CQI): indicates the channel quality.



f(delay): indicate packet delay budget which is specified in 3GPP

.



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Priority of Non-GBR Service Scheduling 

The priority of Non-GBR service is determined by the following formula: Pr iority non 





−

GBR =

eff r

⋅ γ QCI ⋅ γ service

eff: indicates the channel quality r: indicate historical service rate for the UE γ QCI : indicates scheduling priorities corresponding to different QCIs γ service



: indicates the service type weight. The service types are

bit torrent (BT) services and non-BT services


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Contents 2.

Downlink Scheduling 2.1 Scheduling Priority Processing 2.2 MCS Selection & Resource Allocation



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MCS Selection The eNodeB obtains the I TBS according to the adjusted CQI.( eNodeB internal mapping )









If frequency diversity scheduling is used, UE will adopt full band CQI report If frequency selective scheduling is used, UE will adopt sub_band CQI report If CQI adjustment is enabled, the eNodeB adjusts the CQI reported by the UE and selects an MCS based on the adjusted CQI, otherwise eNodeB use the original UE CQI report

The eNodeB selects IMCS according to the mapping from I TBS to IMCS. ( Specified in 3GPP)




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CQI Report Procedure 

Step 1: eNodeB configure CQI report mode with

eNB

periodic or aperiodic mode 

UL Scheduler

Step 2: If it aperiodic report, eNB send UE list to

2

UL scheduler for CQI report scheduling 

CQI Mode Configuration

Step 3: The UL scheduler sends the UL grant t o UE in the aperiodic CQI user list



DL scheduler

A-CQI

P-CQI

Step 4: UE send CQI report to eNodeB 



If periodic CQI mode configuration, UE reports the CQI on PUCCH as RRC configuration

4

3

If aperiodic CQI mode configuration, UE reports the CQI on PUSCH as UL grant.



1

1

UE

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CQI Adjustment 

Why CQI adjustment 

The CQI report period is far greater than the scheduling period, which leads to deviation between the CQI at the reported time and CQI in scheduling.



The reported CQI value depends on the UE measurement, and it may not be very accurate sometimes.



In order to maximize the system capacity, IBLER target other than 10% may be more appropriate, then CQI adjustment is required.


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CQI Adjustment Switch



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RB Calculation & Allocation 

RB calculation: 

The scheduler obtains the amount of data to be scheduled and the I TBS and estimates the number of RBs to be scheduled based on the 3GPP specification



Based on estimate RB number and remaining power, eNodeB finally decide the RB number



RB allocation: 

If frequency diversity scheduling is used, eNodeB allocate all the RB from lower end to the higher end of a frequency band based on full band CQI report



If frequency selective scheduling is used, eNodeB schedules the UEs to frequency bands with the optimum channel quality. This brings frequency selective gains.


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Frequency Selective Scheduling Scheme 1 RBG

UE1

12

10

9

6

8

…

13

6

5

Sub-band1

UE2

11

12

8

10

6

…

6

5

8

Sub-band2

… UEn

10

13

10

… 9

11

…

10

7

5

Sub-band n



Required aperiod sub_band aperiod CQI report



Calculate user’s priority in each sub-band with user queue



Allocate the resource in each sub-band based on user queue



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FSS VS FDS

FSS

FDS


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UL Scheduling Overview eNodeB

UE Scheduling Request (On PUCCH) Periodic or Event triggered

BSR & PHR Scheduling among UEs

UL grant Logical Channel Prioritization & Multiplexing

UL data 

Scheduling on the uplink is more difficult than on the downlink 

Limited visibility of quantity of queued data per radio bearer



Scheduler is unable to offer per-radio bearer grants


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UL Scheduler UL Scheduler

SINR PHR/BSR/SR HARQ feedback QoS parameters

Priority calculation

Selected UE

MCS selection

Bandwidth allocation

Resource allocation

MCS/MIMO

UE Capability Every scheduling period



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UL Scheduling Procedure 

A basic function of UL scheduling is to obtain PUSCH resources. As the PUSCH, PUCCH, and PRACH share the UL bandwidth, the PUSCH occupies the available UL resources in addition to PUCCH and PRACH resources.


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TTI Bundling Scheduling



Benefit 

It increases the UL cell edge user throughput and improve UL coverage.



There is more than 3db gain for uplink coverage



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TTI Bundling Functionality



A TTI bundle permanently consists of four TTIs. The same data is transmitted during the four TTIs


Page32

Synchronized UL Retransmission



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UL Dynamic Scheduling for Initial Transmissions 

UL dynamic scheduling for initial transmission perform three operations: 

Selects UEs for UL scheduling



Determines MCSs to be used



Determines the number and positions of RBs to be allocated


Page34

UL MCS Selection Whether message 3 is transmitted on UL IBLER measurement

DRS measurement

SRS transmission

IBLER target

SINR adjustment

Adjusted SINR

Initial MCS selection

UE UCI transmission capability

MCS adjustment

Final MCS



The process of determining MCSs for UL scheduling consists of three parts: SINR adjustment, initial MCS selection, and MCS adjustment Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.


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SINR Adjustment 

Why SINR adjustment 

Due to fading effect, SINR measurement can not reflect the actual channel quality



SIRN adjustment is used to make the actual IBLER is converged to the target IBLER


Page36

Initial MCS Selection & Adjustment 

On uplink, initial MCS selection is an internal decision by eNodeB according to adjusted SINR



MCS should be adjusted due to the following scenarios : 

To ensure the initial access performance, Huawei eNodeB uses a fixed low-order MCS to transmit message 3



If uplink data is conflict with UCI and SRS transmission, it will cause higher IBLER, so the MCS should be adjusted



If UCI(CQI/PMI/RI) is transmitted on PUSCH, it will use lower MCS to ensure the performance based on a offset. In most of scenario, the default offset can be used, and when the radio environment is extreme bad, we can also adjust it manually.



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Determine Number of RB 

The following info are required to determine number of RB 

Buffer report from UE



Power headroom report from UE



QoS satisfaction rate



Maximum number of RBs supported by a single carrier


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UL QoS Management 

The scheduler use EFP to ensure the QoS for each service, show as below: 

The UL scheduler ensures the PELR and PDB as well as the service rate for GBR services



The UL scheduler uses a best effort policy for non-GBR services and ensures only the minimum GBR specified by the UlMinGbr parameter



If GBR and non-GBR services run simultaneously, GBR services take precedence over non-GBR services



eNodeB scheduler and UE scheduler are involved together on UL scheduling, eNodeB scheduler decide the total resource for each UE and UE scheduler decide the priority of each logic channel scheduling.



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Token Bucket Rate Control in eNB


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Service Priority in UE Scheduler



Logical Channel Type

PRB Configuration

Priority

QCI 1

8 kbyte/s

Not configurable

QCI 2 to QCI 4

Configurable

Not configurable

QCI 5

8kbyte/s

Not configurable

QCI 6 to QCI 9

Configurable

Configurable

The differentiation between services with different QCIs is achieved by setting the logical channel priority and prioritized bit rate



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Pre-Allocation Scheduling Pre-Allocation


Non Pre-Allocation

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VoIP Service Status



Transient state: A newly set up service is unstable



Talk spurt: User is in normal conversation



Silent period: User pauses during the conversation. In this state, a silence insertion descriptor (SID) frame is transmitted every 160 ms.


Page44

Scheduling Scheme



VoIP initial, transient and silent period: Adopt dynamic scheduling



Talk spurt: Normally use semi-persistence scheduling except the following scenarios: 

High speed scenario



UE has the other EPS bear more beside VoIP



The cell bandwidth is 1.4 MHz



UEs request emergency calls



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Semi-Persistence Scheduling 

In semi-persistent scheduling mode, the VoIP service quality can be better ensured because the transmitted DL data has a priority that is second only to that of common control information.



MCS selection: It is the very similar as dynamic scheduling, but the maximum MCS IMCS can only be 15, If the derived IMCS is greater than 15, the eNodeB takes I MCS as 15.


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Resource Limitation 

In order to avoid too much resource occupation by semipersistent scheduling, we can set a threshold to limit semipersistent service. If the total PRB used by semipersistent service is more than threshold in a TTI, then eNB stop the scheduling for the other semi-persistent service and also it stops the admission for this service



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Reference: Parameter description (1/5) 

For detail, please refer to the notes.


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Thank you www.huawei.com


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Microsoft PowerPoint - OEO106040 LTE eRAN6.0 Scheduling Feature ISSUE 1

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