3GPP NRU-Plane Introductionstd-share.itri.org.tw/Content/Files/Event/Files/3.3GPP NR U-plane... · 工研院版權所有Copyright©2017 ITRI. All rights reserved. LCP Enhancement

工研院版權所有 Copyright©2017 ITRI. All rights reserved.

3GPP NR U-Plane Introduction

邱俊淵

工研院資通所

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Agenda• Work Plan of NR• Radio Protocol Architecture• SDAP (Service Data Adaptation Protocol)• PDCP• RLC• MAC

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Work Plan of NR

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2016 2017 2018

Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4

NSA = Non StandAloneSA = StandAlone

5G study5G NR Work Item 5G NR NSA

Completion

Stage 3 completion for Non-Standalone 5G-NR

RAN #74

RAN #75

RAN #78

RAN #80(Rel-15 completion)

Further evolution 5G NR SA Completion

Stage 3 completion for Standalone 5G-NR

NSA Option 3 family ASN.1

Rel-15 ASN.1 for SA & NSA


Non Standalone 5G-NR

• LTE eNB as a master node• Data transport through LTE eNB and/or NR gNB via EPC

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LTE eNB

PDCP

RLC NR RLCRLC

MAC

PDCP

gNB

NR PDCP

NR RLC

NR MAC

S1S1

MCG bearer Split bearer SCG bearer

Xx

Refer to TR 38.801 & TR 38.804


Other Scenarios of 5G-NR

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CN-RAN deployment scenarios where eNB connected to NextGen Core is a master node

CN-RAN deployment scenarios where NR gNB is a master node

Refer to TR 38.804


Radio Protocol Architecture

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gNB

PHY

UE

PHY

MAC

RLC

MAC

AMF

RLC

NAS NAS

RRC RRC

PDCP PDCP

User Plane Protocol Stack Control Plane Protocol Stack

Refer to TS 38.300


SDAP (Service Data Adaptation Protocol)

• The main services and functions of SDAP include:• Mapping between a QoS flow and a data radio bearer

• Due to new QoS framework• Marking QoS flow ID in both DL and UL packets

• For DL: due to reflective QoS• For UL: due to new QoS framework

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New QoS Framework

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CN_UP AN UE

Data packets from applications

“NAS” filters (mapping packets

to QoS flows and apply marking)

Mapping flows to DRBs

Packets marked with “QoS Flow ID” PDU session

Packet filters classify packets to SDFs

Application /Service Layer

AN Resources

Refer to TS 23.501


EPS Bearer Service Architecture

9Refer to TS 36.300


Reflective QoS

• In the uplink, the NG-RAN may control the mapping of QoS Flows to DRB in two different ways:

• Reflective mapping: • for each DRB, the UE monitors the QoS flow ID(s) of the downlink packets

and applies the same mapping in the uplink; that is, for a DRB, the UE maps the uplink packets belonging to the QoS flows(s) corresponding to the QoS flow ID(s) and PDU Session observed in the downlink packets for that DRB. To enable this reflective mapping, the NG-RAN marks downlink packets over Uu with QoS flow ID.

• Explicit Configuration: • besides the reflective mapping, the NG-RAN may configure by RRC an

uplink “QoS Flow to DRB mapping”.

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PDCP• The main services and functions of the PDCP sublayer for the user plane include:

• Sequence Numbering• Header compression and decompression: ROHC only• Transfer of user data• Reordering and duplicate detection (if in order delivery to layers above PDCP is required)• PDCP PDU routing (in case of split bearers)• Retransmission of PDCP SDUs• Ciphering and deciphering• PDCP SDU discard• PDCP re-establishment and data recovery for RLC AM• Duplication of PDCP PDUs

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Out-of-Order Deciphering

• Drawback in LTE• In-sequence delivery from RLC layer (i.e. reordering in RLC) might incur high

latency due to deciphering

• Enhancement in NR• Complete PDCP PDUs can be delivered out-of-order from RLC to PDCP. RLC

delivers PDCP PDUs to PDCP after the PDU is reassembled• PDCP reordering is always enabled if in sequence delivery to layers above

PDCP is needed (i.e. even in non-DC case)

• How does RLC Rx window operation work in NR?• RLC Rx entity needs to keep track of each packet in the window to determine

if any of them has been completed and delivered to PDCP

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Duplication of PDCP PDUs

• Motivation• RLC retransmission (ARQ) is not assumed to be used for meeting the strict

user plane latency requirements of URLLC

• How to do?• Duplication applies in case of multi-connectivity and carrier aggregation (CA).• In case of CA, duplication to more than one logical channel is used for Carrier

Aggregation so that the duplicated PDCP PDUs are sent over different carriers.• PDCP duplication solution for CA requires only one MAC entity.• Logical channel mapping restrictions need to be introduced to handle

duplicates in within one MAC entity (CA).

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CA case

14Refer to R2-1702032


RLC• The main services and functions of the RLC sublayer depend on the

transmission mode and include:• Transfer of upper layer PDUs• Sequence numbering independent of the one in PDCP• Error Correction through ARQ• Segmentation and re-segmentation• Reassembly of SDU• RLC SDU discard• RLC re-establishment(note: no concatenation and no reordering)

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No Concatenation

• Motivation• Extreme latency requirement in 5G

• For URLLC the target for user plane latency should be 0.5ms for UL, and 0.5ms for DL.• For eMBB, the target for user plane latency should be 4ms for UL, and 4ms for DL.• RAN1 intends to reduce the delay from the end of the reception of the DCI (UL grant) to

the beginning of the transmission of the corresponding UL transport block to 1-2 OFDM symbol durations

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e.g. 1 ms

TDLUL TULDL

DL ULULULULUL ULULULUL ULULUL


• Drawback in LTE• In order to perform TB filling, RLC and MAC PDUs are generated after reception of UL grant

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• Removing RLC concatenation enables the pre-processing procedure of both RLC and MAC layer

18Refer to TS 38.300


MAC• The main services and functions of the MAC sublayer include:

• Mapping between logical channels and transport channels• Multiplexing/demultiplexing of MAC SDUs belonging to one or different

logical channels into/from transport blocks (TB) delivered to/from the physical layer on transport channels

• Scheduling information reporting• Error correction through HARQ• Priority handling between UEs by means of dynamic scheduling• Priority handling between logical channels of one UE by means of logical

channel prioritisation• Padding

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New MAC PDU Format

• Drawback in LTE• The LTE MAC PDU format does not facilitate MAC/PHY parallel processing

20Refer to TS 36.321


• Enhancement in NR• MAC subheaders are placed immediately in front of the corresponding MAC

SDUs, MAC CEs, or padding. The possibility to parse the MAC PDU from the back is not precluded.

• UL MAC CE(s) is placed after all the MAC SDUs. For DL the placement will be deterministic (i.e. it should not be up to the network to decide). FFS if we have the same behaviour for both or for DL the MAC CE is placed at the front

21Refer to R2-1703511


LCP Enhancement

• Motivation • Multiple numerologies/TTI durations are supported and different numerologies/TTI durations

may be suitable for different kind of traffic

• Enhancement in NR• A single logical channel can be mapped to one or more numerology/TTI duration. • For the purpose of LCP, the MAC entity learns the TTI duration/numerology from the PHY

layer. FFS on the details of how it is signalled• This can be done explicitly (i.e. some field in the DCI) or • implicitly (e.g. the TTI duration of the UL transmission is the same as the DL transmission of the UL

grant)• LCP takes into account the mapping of logical channel to one or more numerology/TTI

duration. Details of LCP will be discussed in the WI phase• Priority, PBR concept is used in NR as a baseline. • Logical channel priority is configured per UE as a baseline. FFS is anything needs to be done to

treat logical channels differently

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SR/BSR Enhancement

• Motivation • The SR should at least distinguish the “numerology/TTI type” of the logical channel that

triggered the SR • Like the SR, also the design of the BSR is impacted by the multi-numerology/TTI duration

configuration supported in NR

• Enhancement in NR• How SR enhancement is done is FFS

• Multiple-bit SR or• Single-bit SR with multiple SR configurations

• The existing LTE BSR framework is used as baseline for NR BSR framework. Further enhancements at least related to numerologies and granularity and can be further discussed

• Numerologies: Extend the number of LCGs to link a LCG to a specific numerology • Granularity: increasing the number of bits in the BS field, increasing the number of LCGs, reporting

BSR per logical channel

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HARQ Enhancement

• Motivation • Performance degradation of HARQ due to large transport block size

• Enhancement in NR• Code Block Group (CBG)-based transmission with single/multi-bit HARQ-ACK feedback is

supported (FFS: two alternatives to form CBG)• The UE is semi-statically configured by RRC signaling to enable CBG-based retransmission.• The above semi-static configuration to enable CBG-based retransmission is separate for DL

and UL.

24Refer to R1-1705401


• Enhancement in NR• Asynchronous and adaptive UL HARQ is supported at least for eMBB• Flexible timing

• Timing between DL assignment and corresponding DL data transmission is indicated by a field inthe DCI from a set of values

• Timing between UL assignment and corresponding UL data transmission is indicated by a field inthe DCI from a set of values

• Timing between DL data reception and corresponding acknowledgement is indicated by a field inthe DCI from a set of values• The set of values is configured by higher layer

• NR UE supports a set of minimum HARQ processing time• Delay between DL data reception timing to the corresponding HARQ-ACK transmission

timing• Delay between UL grant reception timing to the corresponding UL data transmission timing• NR UE is required to indicate its capability of minimum HARQ processing time to gNB

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Thanks

[email protected]

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Documents

3GPP NRU-Plane Introductionstd-share.itri.org.tw/Content/Files/Event/Files/3.3GPP NR U-plane... · 工研院版權所有Copyright©2017 ITRI. All rights reserved. LCP Enhancement