5G载波聚合SCell添加与MAC CE激活信令全链拆解

stateDiagram-v2
    [*] --> NotConfigured: UE初始状态

    NotConfigured --> ConfiguredDeactivated: RRCReconfiguration\n(sCellToAddModList)
    NotConfigured --> ConfiguredActivated: RRCReconfiguration\n(sCellState=activated)

    ConfiguredDeactivated --> ConfiguredActivated: MAC CE激活\n(LCID=53/54)
    ConfiguredDeactivated --> NotConfigured: RRCReconfiguration\n(sCellToReleaseList)

    ConfiguredActivated --> ConfiguredDeactivated: MAC CE去激活\n或sCellDeactivationTimer超时
    ConfiguredActivated --> NotConfigured: RRCReconfiguration\n(sCellToReleaseList)

    note right of ConfiguredDeactivated
        UE行为受限：
        - 不监听PDCCH
        - 不发送SRS
        - 不上报CSI
        - 不传UL-SCH
    end note

    note right of ConfiguredActivated
        UE正常操作：
        - 监听PDCCH
        - 发送SRS/CSI
        - 收发数据
        - 重启deactivationTimer
    end note

sequenceDiagram
    participant UE as UE
    participant gNB as gNB

    Note over gNB: gNB决策添加SCell<br/>(基于测量报告/负载/CA能力)

    gNB->>UE: RRCReconfiguration<br/>(含masterCellGroup > sCellToAddModList)
    Note right of gNB: 关键IE:<br/>- sCellIndex<br/>- sCellConfigCommon<br/>- sCellConfigDedicated<br/>- firstActiveDownlinkBWP-Id

    UE->>UE: 解析ASN.1配置<br/>存储SCell参数<br/>SCell状态=Deactivated

    UE->>gNB: RRCReconfigurationComplete<br/>(rrc-TransactionIdentifier匹配)

    Note over UE,gNB: RRC配置完成<br/>SCell处于"已配置去激活"状态

    rect rgb(230, 245, 255)
    Note over gNB: gNB决定激活SCell

    gNB->>UE: DCI 1_1 (PCell)<br/>(调度承载MAC CE的PDSCH)
    gNB->>UE: PDSCH (PCell)<br/>(含SCell Activation MAC CE)
    Note right of gNB: MAC CE格式:<br/>Ci=1 表示激活SCellIndex=i

    UE->>UE: 收到MAC CE后<br/>启动SCell激活过程

    UE->>gNB: PUCCH (HARQ ACK)<br/>(确认收到MAC CE)

    Note over UE: 激活时序:<br/>n + N_Activate_DEACT_SCell<br/>(TS 38.213 Table 11-6)

    rect rgb(255, 245, 230)
    Note over UE: SCell已激活<br/>开始以下操作:<br/>1. SRS传输<br/>2. CSI上报<br/>3. PDCCH监听<br/>4. 启动sCellDeactivationTimer
    end

    gNB->>UE: DCI 1_1 (PCell)<br/>(调度SCell上的PDSCH)
    gNB->>UE: PDSCH (SCell)<br/>(SCell首份数据)
    UE->>gNB: PUCCH/PUSCH (PCell/SCell)<br/>(HARQ ACK)
    end

RRCReconfiguration (TS 38.331 Section 6.2.2)
├── rrc-TransactionIdentifier (0..3)     ← 事务标识，UE在Complete中原样返回
├── criticalExtensions
│   └── rrcReconfiguration
│       ├── masterCellGroup (OCTET STRING) ← 编码后的CellGroupConfig
│       │   └── CellGroupConfig (Section 6.3.2)
│       │       ├── cellGroupId (0..3)    ← MCG=0, SCG=1
│       │       ├── mac-CellGroupConfig   ← MAC层参数(PHR/BSR/SR/DRX)
│       │       ├── spCellConfig          ← 特殊小区(PCell)配置
│       │       └── sCellToAddModList     ← ★ SCell添加列表
│       │           └── SCellToAddMod (Section 6.3.2)
│       │               ├── sCellIndex (1..31)        ← SCell唯一索引
│       │               ├── sCellConfigCommon          ← 公共配置
│       │               │   ├── physCellId (0..1007)  ← 物理小区ID
│       │               │   ├── downlinkConfigCommon
│       │               │   │   ├── frequencyInfoDL
│       │               │   │   │   ├── absoluteFrequencySSB  ← SSB绝对频点
│       │               │   │   │   ├── frequencyBandList     ← 频段列表
│       │               │   │   │   ├── absoluteFrequencyPointA ← Point A
│       │               │   │   │   └── scs-SpecificCarrierList ← SCS/带宽
│       │               │   │   └── initialDownlinkBWP
│       │               │   │       └── pdcch-ConfigCommon/pdsch-ConfigCommon
│       │               │   ├── ssb-PositionsInBurst    ← SSB时域位置
│       │               │   ├── ssb-periodicityServingCell
│       │               │   └── tdd-UL-DL-ConfigurationCommon ← TDD配置
│       │               └── sCellConfigDedicated        ← 专用配置
│       │                   ├── initialDownlinkBWP
│       │                   │   ├── pdcch-Config        ← SCell的PDCCH搜索空间
│       │                   │   └── pdsch-Config        ← SCell的PDSCH参数
│       │                   ├── firstActiveDownlinkBWP-Id ← ★ 首次激活BWP
│       │                   ├── pdsch-ServingCellConfig  ← HARQ进程数等
│       │                   ├── csi-MeasConfig           ← CSI测量配置
│       │                   └── tag-Id                   ← Timing Advance Group
│       ├── radioBearerConfig              ← DRB/SRB配置(可能同时修改)
│       ├── dedicatedNAS-MessageList       ← NAS消息透传
│       └── nonCriticalExtension           ← Rel-15+扩展链

flowchart LR
    A[RRCReconfiguration<br/>L3消息] --> B[masterCellGroup<br/>OCTET STRING]
    B --> C[ASN.1 UPER解码]
    C --> D[CellGroupConfig]
    D --> E[sCellToAddModList]
    E --> F[SCellToAddMod[0]<br/>sCellIndex=1]
    E --> G[SCellToAddMod[1]<br/>sCellIndex=2]

    style B fill:#fff3cd
    style C fill:#d1ecf1

字节结构:
  比特位:  | C7 | C6 | C5 | C4 | C3 | C2 | C1 | R  |
           |    |    |    |    |    |    |    |    |
含义:      |S7 |S6 |S5 |S4 |S3 |S2 |S1 |保留|

  Ci = 1: 激活SCellIndex = i
  Ci = 0: 去激活SCellIndex = i
  R = 保留位，设为0

字节1: | C7 | C6 | C5 | C4 | C3 | C2 | C1 | R  |
字节2: | C15| C14| C13| C12| C11| C10| C9 | C8 |
字节3: | C23| C22| C21| C20| C19| C18| C17| C16|
字节4: | R  | R  | R  | R  | R  | R  | R  | C24|

[1] RRCReconfiguration for SCell Addition
  sCellIndex = 1
  physCellId = 501
  absoluteFrequencySSB = 627264
  frequencyBandList = { n78 }
  absoluteFrequencyPointA = 626688
  scs-SpecificCarrierList = { offsetToCarrier=0, kHz30, carrierBandwidth=51 }
  tdd-UL-DL-ConfigurationCommon:
    dl-UL-TransmissionPeriodicity = ms5
    nrofDownlinkSlots = 7, nrofDownlinkSymbols = 6
    nrofUplinkSlots = 2, nrofUplinkSymbols = 4
  firstActiveDownlinkBWP-Id = 0
  nrofHARQ-ProcessesForPDSCH = n16

[2] RRCReconfigurationComplete
  rrc-TransactionIdentifier = 0 (匹配)

[3] MAC CE Activation
  Scell AD:02  ← 0x02 = 二进制 00000010, 即C1=1, 激活SCellIndex=1
  LCID = 53 (SCell Activation/Deactivation MAC CE, 1 octet)

flowchart TD
    A[收到Activation MAC CE] --> B{SCell之前是否Deactivated?}
    B -->|是| C{firstActiveDownlinkBWP-Id<br/>是否为dormant BWP?}
    B -->|"否(sCellState直接激活)"| C
    C -->|否: 正常BWP| D[激活SCell<br/>时序: n + N_Activate]
    C -->|是: dormant BWP| E[停止bwp-InactivityTimer<br/>激活dormant BWP]
    D --> F[启动/重启<br/>sCellDeactivationTimer]
    E --> F
    F --> G{active DL BWP<br/>≠ dormant BWP?}
    G -->|是| H[重新初始化Configured Grant Type 1]
    G -->|否| I[等待后续BWP切换]
    H --> J[触发PHR<br/>Power Headroom Report]
    I --> K[正常SCell操作]
    J --> K

    K --> L[SRS传输 ✓]
    K --> M[CSI上报 ✓]
    K --> N[PDCCH监听 ✓]
    K --> O[PUCCH传输 ✓]
    K --> P[数据收发 ✓]

    style D fill:#d4edda
    style F fill:#fff3cd

flowchart LR
    A[SCell Deactivated] -->|MAC CE激活| B[SCell Activated<br/>dormant BWP]
    B -->|DCI BWP切换| C[SCell Activated<br/>normal BWP]
    C -->|DCI BWP切换| B
    C -->|MAC CE去激活<br/>或Timer超时| A
    B -->|MAC CE去激活| A

    style B fill:#fff3cd
    style C fill:#d4edda

# 过滤5G NR RRC Reconfiguration消息
tshark -r capture.pcap -Y "nr-rrc.rrcReconfiguration"

# 过滤SCell添加相关的RRC消息（包含sCellToAddModList）
tshark -r capture.pcap -Y "nr-rrc.sCellToAddModList"

# 过滤MAC CE SCell Activation/Deactivation
tshark -r capture.pcap -Y "mac-nr.ce_lcid == 53 || mac-nr.ce_lcid == 54"

# 导出SCell配置详情
tshark -r capture.pcap -V -Y "nr-rrc.sCellIndex" 2>/dev/null | grep -A5 "sCellIndex\|physCellId\|absoluteFrequency"

# 统计SCell激活/去激活事件
tshark -r capture.pcap -Y "mac-nr.ce_lcid == 53" -T fields -e frame.number -e mac-nr.ce_lcid