From LTE to 5G New Radio (NR): Layer 2 Aspects 不要用演進概括 華碩電腦 陳威宇 專員

Outline Introduction of 5G NR SDAP (Service Data Adaptation Protocol) PDCP (Packet Data Convergence Protocol) RLC (Radio Link Control) MAC (Medium Access Control) Future Works in 5G NR Layer 2

Introduction of 5G NR Introduction of 5G NR SDAP PDCP RLC MAC 5G NR Requirements 5G NR Layer 2 SDAP PDCP RLC MAC Future Works in 5G NR Layer 2

5G NR Requirements DL 4 ms UL 4 ms DL 0.5 ms UL 0.5 ms 1-10-5 Battery life: 10~15 years [1]

5G NR Layer 2 LTE vs NR LTE User Plane Protocol NR User Plane Protocol PDCP子層負責的主要功能有資料封包的標頭(Header)壓縮與解壓縮、資料加密/解密、資料完整性的保護。   RLC子層後，該子層主要的功能為對資料SDU進行切割及組合，使之成為適當大小的PDU。RLC子層負責的另一項重要工作則是在封包遺失時進行自動重傳請求(Automatic Repeat Request, ARQ)。   MAC子層將接手執行排程(Scheduling)、多工(Multiplexing)等任務，以組成MAC子層PDU。此外，在MAC子層端，為防止RLC提供的PDU遺失，還具備混合式自動回覆請求重傳(HARQ)等功能。  

Service Data Adaptation Protocol Introduction of 5G NR SDAP Introduction of SDAP Reflective QoS PDCP RLC MAC Future Works in 5G NR Layer 2

Introduction of SDAP (1/2) Introduce QoS-flow NR LTE Reason NR LTE Flexibility for base station to control mapping between radio bearers(RB) and flows based on radio resource management (RRM) policy

Introduction of SDAP (2/2) SDAP layer (User plane)

To minimize the control signaling between network and UE Reflective QoS AS reflective QoS DL Application QoS rule 2 SDAP 1 SDF flow1 QoS flow1 RB1 SDF flow2 QoS flow1 3 4 動畫; 數字 箭頭 清晰化 UL To minimize the control signaling between network and UE

Packet Data Convergence Protocol Introduction of 5G NR SDAP PDCP PDCP Duplication RLC MAC Future Works in 5G NR Layer 2 簡寫 要說明

PDCP Duplication (1/2) To increase reliability of Signaling Radio Bearer (SRB) and Data Radio Bearer (DRB) for URLLC Data Data PDCP PDCP Data Data Data Data RLC RLC RLC RLC MAC MAC MAC MAC Data Data

PDCP Duplication (2/2) Carrier Aggregation Dual Connectivity CA ; DC deployment concept; LTE Cell1 Cell1 Cell1 Cell3 Cell2 Cell2 Cell2 Cell4

Radio Link Control Introduction of 5G NR SDAP PDCP RLC MAC RLC Acknowledged Mode (AM) NACK Range MAC Future Works in 5G NR Layer 2 簡寫 要說明

No concatenation in RLC RLC AM NACK Range New field in status PDU – NACK range Contiguous RLC PDUs loss will occur in MAC PDU transmission failure case No concatenation in RLC LTE 和NR 比對圖; LTE - > reason - > NR vs LTE

Medium Access Control Introduction of 5G NR SDAP PDCP RLC MAC MAC Protocol Data Unit (PDU) Format Logical Channel Prioritization (LCP) Enhancement Scheduling Request (SR) Enhancement On-demand System Information Mechanism Future Works in 5G NR Layer 2 簡寫 要說明

For reducing processing time, preprocessing is allowed. MAC PDU Format (1/2) For reducing processing time, preprocessing is allowed. UL format LTE NR

MAC PDU Format (2/2) DL format LTE NR

LCP Enhancement (1/2) Logical Channel Prioritization (LCP) is a procedure to create MAC PDU for transmission LTE LC1 LC2 LC1 LC2 Logical channel 1: - Priority 1 Logical channel 2: - Priority 2 Grant 簡介LCP的功能;LTE ; LTE vs NR LCP MAC PDU

LCP Enhancement (2/2) For achieving URLLC service requirement Latency≦0.5ms Logical channel scheduling limitation Sub-Carrier Spacing (SCS) Time information Cell NR LC1 LC2 LC1 LC2 Logical channel 1: - Priority 1 - SCS index 1 簡介LCP的功能;LTE ; LTE vs NR Logical channel 2: - Priority 2 - SCS index 2 Grant on SCS 2 LCP MAC PDU

For achieving URLLC service requirement SR Enhancement Scheduling Request (SR) is for UE to autonomously request resource on data channel Multiple SR configurations associated with different resource demands SR configuration 1 SR1 SR configuration 2 SR2 UE BS UE BS SR SR1 / SR2 Uplink grant Uplink grant1/ Uplink grant2 BSR + data BSR + data1/data2 For achieving URLLC service requirement Latency≦0.5ms

On-demand System Information (1/2) LTE system information Periodically broadcast NR System information Minimum system information (SI) Necessary system information for initial access Other system information (on-demand) LTE SI mechanism info. Reduce unnecessary broadcast transmissions

On-demand System Information (2/2) For requesting Other SI Transmit system information request (RRC_CONNECTED) RA Msg1 based (RRC_IDLE/ RRC_INACTIVE) RA Msg3 based (RRC_IDLE/ RRC_INACTIVE) Msg1 based Msg3 based UE BS UE BS Minimum SI Minimum SI Msg1 Compromise Special Msg1 for Other SI Msg2 Msg2 Msg3(SI request) Other SI Other SI

Future Works Introduction of 5G NR SDAP PDCP RLC MAC Future Works in 5G NR Layer 2 簡寫 要說明

Future Works in 5G NR Layer 2 V2X Communication/Sidelink Communication Impact of enhancements in NR Impact of any new service requirements Massive Machine Type Communication (mMTC) Power saving mechanism Small data transmission [2] [3]

References IMT Vision – Framework and overall objectives of the future development of IMT for 2020 and beyond 5G-PPP White Paper on Automotive Vertical Sector Expanding the horizon of Mobile networks for Internet of Things, Hammad Tariq, https://www.linkedin.com/pulse/expanding-horizon-mobile-networks-internet-things-hammad-tariq TS 38.300 running CR TS 38.321 running CR TS 38.322 running CR TS 36.331

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