5G URLLC冗余传输三架构与N3/N9双径博弈

graph TB
    subgraph "URLLC冗余传输三架构对比"
        A["架构1: 双PDU Session<br/>端到端冗余"] --> A1["UE应用层复制"]
        A --> A2["两套SMF+UPF"]
        A --> A3["DN侧去重"]

        B["架构2: 冗余QoS Flow<br/>N3双隧道"] --> B1["UPF复制/去重"]
        B --> B2["单SMF管理"]
        B --> B3["gNB双DRB"]

        C["架构3: N3/N9 GTP-U<br/>传输层复制"] --> C1["UPF GTP-U复制"]
        C --> C2["单PDU Session"]
        C --> C3["对UE透明"]
    end

    style A fill:#e1f5fe
    style B fill:#fff3e0
    style C fill:#e8f5e9

sequenceDiagram
    participant UE
    participant RAN1 as gNB1(MN)
    participant RAN2 as gNB2(SN)
    participant AMF
    participant SMF1 as SMF1
    participant SMF2 as SMF2
    participant UPF1 as UPF/PSA1
    participant UPF2 as UPF/PSA2
    participant DN

    Note over UE,DN: 阶段1: 建立PDU Session #1
    UE->>AMF: Namf_Communication_N1N2MessageTransfer<br/>PDU Session Establishment Request<br/>DNN=industrial, S-NSSAI=URLLC
    AMF->>SMF1: Nsmf_PDUSession_CreateSMContext Request<br/>SUPI, DNN, S-NSSAI, RedundantSessionIndication
    SMF1->>SMF1: 检查URLLC订阅<br/>分配PSA1 UPF
    SMF1->>UPF1: N4 Session Establishment<br/>PDR+FAR+QER(URLLC 5QI=80/84/85)
    UPF1-->>SMF1: N4 Session Establishment Response<br/>N3 TEID1, UPF1 IP
    SMF1-->>AMF: N1N2MessageTransfer<br/>PDU Session Establishment Accept<br/>N2 SM Info: {N3 Tunnel1, QoS Profile}
    AMF->>RAN1: N2 PDU Session Resource Setup Request<br/>N3 TEID1, QFI=80, 5QI=80
    RAN1->>UE: RRC Reconfiguration<br/>DRB Config for Session #1
    UE-->>RAN1: RRC Reconfiguration Complete
    RAN1-->>AMF: N2 PDU Session Resource Setup Response<br/>AN Tunnel Info1
    AMF-->>SMF1: Nsmf_PDUSession_UpdateSMContext<br/>AN Tunnel Info1
    SMF1->>UPF1: N4 Session Modification<br/>Update FAR with AN Tunnel Info1

    Note over UE,DN: 阶段2: 建立PDU Session #2（冗余）
    UE->>AMF: PDU Session Establishment Request<br/>DNN=industrial, RedundantSessionIndication=TRUE<br/>PDU Session Pair ID
    AMF->>SMF2: Nsmf_PDUSession_CreateSMContext Request<br/>RedundantPDUSessionIndication
    SMF2->>SMF2: 选择与SMF1不同的UPF<br/>确保路径非重叠
    SMF2->>UPF2: N4 Session Establishment<br/>PDR+FAR+QER(URLLC)
    UPF2-->>SMF2: N4 Response: N3 TEID2, UPF2 IP
    SMF2-->>AMF: N2 SM Info: {N3 Tunnel2}
    AMF->>RAN2: N2 PDU Session Resource Setup Request<br/>N3 TEID2, via SN Addition
    RAN2->>UE: RRC Reconfiguration<br/>DRB Config for Session #2
    RAN2-->>AMF: AN Tunnel Info2
    AMF-->>SMF2: Update AN Tunnel Info2
    SMF2->>UPF2: N4 Modification: AN Tunnel Info2

    Note over UE,DN: 阶段3: 数据双径传输
    UE->>DN: UL Data Copy A via Session#1 → RAN1 → UPF1 → DN
    UE->>DN: UL Data Copy B via Session#2 → RAN2 → UPF2 → DN
    DN->>UPF1: DL Data Copy A
    DN->>UPF2: DL Data Copy B
    UPF1->>RAN1: DL Copy A → UE
    UPF2->>RAN2: DL Copy B → UE
    UE->>UE: 应用层去重(SN-based)

graph LR
    subgraph "SMF N4规则编排"
        direction TB
        S1["PDR#1: Match QFI=Q1<br/>UL PDU Session Container"] --> F1["FAR#1: Forward<br/>N3 Tunnel A → gNB"]
        S2["PDR#2: Match QFI=Q2<br/>UL PDU Session Container"] --> F2["FAR#2: Forward<br/>N3 Tunnel B → gNB"]
        S3["PDR#3: Match N3 Tunnel A<br/>DL"] --> F3["FAR#3: Forward<br/>QoS Flow Q1 → UE"]
        S4["PDR#4: Match N3 Tunnel B<br/>DL"] --> F4["FAR#4: Forward<br/>QoS Flow Q2 → UE"]
    end

    subgraph "冗余QoS Flow绑定"
        B1["QFI=Q1 ←→ QFI=Q2<br/>RedundantQoSFlowPair"]
        B2["两套独立N3隧道<br/>Tunnel A ←→ Tunnel B"]
        B3["两套独立DRB<br/>DRB1 ←→ DRB2"]
    end

    S1 -.-> B1
    S2 -.-> B1

sequenceDiagram
    participant UE
    participant gNB
    participant AMF
    participant SMF
    participant UPF as UPF(PSA)
    participant DN

    Note over UE,UPF: 阶段1: PDU Session建立（携带冗余指示）
    UE->>gNB: PDU Session Establishment Request
    gNB->>AMF: N2 Message + NAS PDU
    AMF->>SMF: CreateSMContext<br/>URLLC RedundantTransmission Request=TRUE
    SMF->>SMF: 决策: N3/N9传输层复制<br/>选择支持GTP-U Duplication的UPF
    SMF->>UPF: N4 Session Establishment<br/>PDR + FAR + MAR(Duplication)<br/>Duplication Detection Parameters
    Note over SMF,UPF: MAR指示UPF对DL包执行GTP-U复制<br/>携带两个N3隧道端点
    UPF-->>SMF: N4 Response<br/>N3 Tunnel A: TEID-A, IP-A<br/>N3 Tunnel B: TEID-B, IP-B
    SMF-->>AMF: N2 SM Info<br/>{Tunnel A, Tunnel B}<br/>RedundantTransmission=TRUE
    AMF->>gNB: N2 PDU Session Resource Setup<br/>两条N3隧道信息<br/>Duplication Instruction
    Note over gNB: gNB配置:<br/>1. UL: PDCP PDU → GTP-U复制<br/>   → Tunnel A + Tunnel B<br/>2. DL: 两条隧道收包 → 去重 → PDCP
    gNB-->>AMF: N2 Response<br/>AN Tunnel Info(1条)
    AMF-->>SMF: Update SMContext<br/>AN Tunnel Info
    SMF->>UPF: N4 Modification<br/>DL FAR: 复制到两个AN Tunnel

    Note over UE,DN: 阶段2: 数据传输（GTP-U层复制）
    rect rgb(230,245,255)
        Note over UE,UPF: 上行: UE → gNB → N3双隧道 → UPF
        UE->>gNB: UL Data (IP Packet)
        gNB->>gNB: GTP-U封装 + 复制<br/>SN=x, Tunnel A
        gNB->>UPF: GTP-U PDU(SN=x) → IP-A:TEID-A
        gNB->>gNB: GTP-U封装 + 复制<br/>SN=x, Tunnel B
        gNB->>UPF: GTP-U PDU(SN=x) → IP-B:TEID-B
        UPF->>UPF: SN去重: 保留第一个<br/>丢弃重复包(SN=x)
        UPF->>DN: 去重后的IP Packet
    end

    rect rgb(255,243,224)
        Note over DN,UE: 下行: DN → UPF → N3双隧道 → gNB → UE
        DN->>UPF: DL Data (IP Packet)
        UPF->>UPF: GTP-U封装 + 复制<br/>SN=y, Tunnel A
        UPF->>gNB: GTP-U PDU(SN=y) → IP-A:TEID-A
        UPF->>UPF: GTP-U封装 + 复制<br/>SN=y, Tunnel B
        UPF->>gNB: GTP-U PDU(SN=y) → IP-B:TEID-B
        gNB->>gNB: SN去重: 保留第一个<br/>丢弃重复包(SN=y)
        gNB->>UE: 去重后的IP Packet
    end

MAR (Multiplying Action Rule):
  MAR ID = 1
  Rule Trigger: Matching DL PDR
  Steer Mode: Replicate (复制模式)
  FAR List:
    - FAR#1: N3 Tunnel A (IP-A, TEID-A)
    - FAR#2: N3 Tunnel B (IP-B, TEID-B)
  CP Function Parameters:
    - Duplication Detection: Enabled
    - SN Assignment: Per-packet incremental

graph TD
    START["URLLC冗余传输需求"] --> Q1{"DN侧应用<br/>是否支持复制/去重?"}
    Q1 -->|是| Q2{"是否需要<br/>端到端冗余?"}
    Q1 -->|否| Q3{"UE协议栈<br/>是否可修改?"}
    Q2 -->|是| ARCH1["架构1: 双PDU Session<br/>最高可靠性"]
    Q2 -->|否| Q3
    Q3 -->|是| ARCH2["架构2: 冗余QoS Flow<br/>中等可靠性"]
    Q3 -->|否| ARCH4{"gNB是否支持<br/>GTP-U复制?"}
    ARCH4 -->|是| ARCH3["架构3: N3/N9 GTP-U<br/>对UE透明"]
    ARCH4 -->|否| ARCH5["仅PDCP Duplication<br/>(RAN侧冗余)"]

    style ARCH1 fill:#e1f5fe
    style ARCH2 fill:#fff3e0
    style ARCH3 fill:#e8f5e9
    style ARCH5 fill:#fce4ec