VoNR SIP INVITE与Precondition资源预留信令拆解

sequenceDiagram
    participant UE_A as UE-A (主叫)
    participant P_CSCF_A as P-CSCF-A
    participant PCF as PCF
    participant S_CSCF as S-CSCF
    participant P_CSCF_B as P-CSCF-B
    participant UE_B as UE-B (被叫)
    participant SMF as SMF
    participant AMF as AMF
    participant gNB as gNB

    Note over UE_A,UE_B: Phase 1: SIP INVITE + SDP Offer（初始 offer）
    UE_A->>P_CSCF_A: SIP INVITE (SDP Offer, precondition: none)
    P_CSCF_A->>PCF: Npcf_PolicyAuthorization_Create (媒体描述)
    PCF-->>P_CSCF_A: 201 Created (Policy Decision)
    P_CSCF_A->>S_CSCF: SIP INVITE (转发)
    S_CSCF->>P_CSCF_B: SIP INVITE (转发)
    P_CSCF_B->>UE_B: SIP INVITE

    Note over UE_A,UE_B: Phase 2: 183 Session Progress + SDP Answer
    UE_B->>P_CSCF_B: SIP 183 Session Progress (SDP Answer)
    P_CSCF_B->>PCF: Npcf_PolicyAuthorization_Create (被叫侧策略)
    P_CSCF_B->>S_CSCF: SIP 183 (转发)
    S_CSCF->>P_CSCF_A: SIP 183 (转发)
    P_CSCF_A->>UE_A: SIP 183 Session Progress

    Note over UE_A,UE_B: Phase 3: PRACK确认183
    UE_A->>P_CSCF_A: SIP PRACK
    P_CSCF_A->>S_CSCF: PRACK (转发)
    S_CSCF->>P_CSCF_B: PRACK (转发)
    P_CSCF_B->>UE_B: PRACK
    UE_B-->>P_CSCF_B: 200 OK (PRACK)
    P_CSCF_B-->>UE_A: 200 OK (PRACK) (逐跳转发)

    Note over UE_A,gNB: Phase 4: 主叫侧资源预留 (5GC QoS Flow建立)
    P_CSCF_A->>PCF: 通知资源授权完成
    PCF->>SMF: Npcf_SMPolicyControl_Update (PCC Rule: 5QI=1)
    SMF->>AMF: Namf_N1N2MessageTransfer (N1+N2 SM Container)
    AMF->>gNB: N2 PDU Session Resource Setup (QoS Flow: 5QI=1, QFI)
    gNB->>UE_A: RRC Reconfiguration (DRB建立)
    UE_A-->>gNB: RRC Reconfiguration Complete
    gNB-->>SMF: N2 PDU Session Resource Setup Response

    Note over UE_A,UE_B: Phase 5: SIP UPDATE (主叫侧Precondition满足)
    UE_A->>P_CSCF_A: SIP UPDATE (a=curr:qos local sendrecv)
    P_CSCF_A->>S_CSCF: UPDATE (转发)
    S_CSCF->>P_CSCF_B: UPDATE (转发)
    P_CSCF_B->>UE_B: UPDATE

    Note over UE_B,gNB: Phase 6: 被叫侧资源预留
    P_CSCF_B->>PCF: 通知资源授权
    PCF->>SMF: PCC Rule下发 (被叫侧5QI=1)
    SMF->>AMF: PDU Session Modification
    AMF->>gNB: N2 QoS Flow Setup (被叫侧)

    UE_B-->>P_CSCF_B: 200 OK (UPDATE, a=curr:qos local sendrecv)

    Note over UE_A,UE_B: Phase 7: 振铃与呼叫建立
    UE_B->>P_CSCF_B: SIP 180 Ringing
    P_CSCF_B->>S_CSCF: 180 Ringing (转发)
    S_CSCF->>P_CSCF_A: 180 Ringing (转发)
    P_CSCF_A->>UE_A: SIP 180 Ringing (回铃音)
    UE_B->>P_CSCF_B: SIP 200 OK (INVITE)
    P_CSCF_B->>S_CSCF: 200 OK (转发)
    S_CSCF->>P_CSCF_A: 200 OK (转发)
    P_CSCF_A->>UE_A: SIP 200 OK
    UE_A->>P_CSCF_A: SIP ACK
    P_CSCF_A->>S_CSCF: ACK (转发)→P_CSCF_B→UE_B

    Note over UE_A,UE_B: ========== 双向语音通话建立 ==========

v=0
o=- 32674926 32674926 IN IP4 10.1.2.3
s=-
c=IN IP4 10.1.2.3
t=0 0
m=audio 49152 RTP/AVP 96 97 98
b=AS:41
b=RS:600
b=RR:2000
a=curr:qos local none
a=curr:qos remote none
a=des:qos mandatory local sendrecv
a=des:qos mandatory remote sendrecv
a=conf:qos remote sendrecv
a=rtpmap:96 EVS/16000/1
a=fmtp:96 br=5.9-24.4; bw=nb-wb; max-red=220
a=rtpmap:97 AMR-WB/16000/1
a=fmtp:97 mode-change-capability=2; max-red=220
a=rtpmap:98 telephone-event/16000
a=fmtp:98 0-15
a=ptime:20
a=maxptime:240
a=sendrecv

m=audio 49170 RTP/AVP 96 98
b=AS:41
a=curr:qos local none
a=curr:qos remote none
a=des:qos mandatory local sendrecv
a=des:qos mandatory remote sendrecv
a=conf:qos remote sendrecv
a=rtpmap:96 EVS/16000/1
a=fmtp:96 br=5.9-24.4; bw=nb-wb
a=rtpmap:98 telephone-event/16000
a=sendrecv

stateDiagram-v2
    [*] --> INIT: INVITE发送
    INIT --> LOCAL_RESERVED: 主叫侧QoS Flow建立成功
    LOCAL_RESERVED --> BOTH_RESERVED: 被叫侧QoS Flow建立成功
    BOTH_RESERVED --> RINGING: 180 Ringing
    RINGING --> CONNECTED: 200 OK + ACK

    LOCAL_RESERVED --> UPDATE_SENT: 发送UPDATE(a=curr:qos local sendrecv)
    UPDATE_SENT --> BOTH_RESERVED: 收到200 OK(UPDATE)

    state INIT {
        [*] --> WaitLocalResource
        note right of WaitLocalResource: a=curr:qos local none
    }

    state BOTH_RESERVED {
        [*] --> PreconditionSatisfied
        note right of PreconditionSatisfied: a=curr:qos local sendrecv\na=curr:qos remote sendrecv
    }

sequenceDiagram
    participant P_CSCF as P-CSCF
    participant PCF as PCF
    participant SMF as SMF

    P_CSCF->>PCF: POST /npcf-policyauthorization/v1/app-sessions<br/>(Media-Component-Descriptor)
    Note right of P_CSCF: AF-Charging-Id<br/>Media-Type=Audio<br/>Codec=EVS<br/>BW=41kbps<br/>Flow-Status=ENABLED<br/>Reservation-Priority=1

    PCF->>PCF: 1. 查找关联的PDU Session<br/>2. 检查用户订阅的QoS权限<br/>3. 生成PCC Rule

    PCF-->>P_CSCF: 201 Created<br/>(App-Session-Id, Policies)
    PCF->>SMF: Npcf_SMPolicyControl_Update<br/>(PCC Rule: 5QI=1, GFBR=41kbps)
    SMF->>SMF: 1. 分配QFI<br/>2. 创建QoS Flow<br/>3. 生成N2 SM Info

UPDATE sip:[email protected] SIP/2.0
Via: SIP/2.0/UDP 10.1.2.3:5060;branch=z9hG4bK1234
From: <sip:[email protected]>;tag=abc123
To: <sip:[email protected]>;tag=xyz789
Call-ID: [email protected]
CSeq: 2 UPDATE
Content-Type: application/sdp

v=0
o=- 32674926 32674927 IN IP4 10.1.2.3
s=-
c=IN IP4 10.1.2.3
t=0 0
m=audio 49152 RTP/AVP 96 98
a=curr:qos local sendrecv
a=curr:qos remote none
a=des:qos mandatory local sendrecv
a=des:qos mandatory remote sendrecv
a=conf:qos remote sendrecv
a=sendrecv

SIP/2.0 200 OK
Content-Type: application/sdp

v=0
m=audio 49170 RTP/AVP 96 98
a=curr:qos local sendrecv
a=curr:qos remote sendrecv
a=des:qos mandatory local sendrecv
a=des:qos mandatory remote sendrecv
a=sendrecv

flowchart TD
    A[UE-A: INVITE SDP Offer<br/>EVS, AMR-WB, telephone-event] --> B{UE-B能力检查}
    B --> C[优先选择EVS<br/>Super-Wideband]
    B --> D[回退AMR-WB<br/>Wideband]
    B --> E[最低回退AMR-NB<br/>Narrowband]
    C --> F[SDP Answer: 选定EVS<br/>fmtp参数协商]
    D --> G[SDP Answer: 选定AMR-WB]
    E --> H[SDP Answer: 选定AMR-NB<br/>VoNR不支持, EPS Fallback]

classDiagram
    class SIP_INVITE {
        +Request-URI: sip:userB@ims...
        +From: sip:userA@ims...;tag=abc
        +To: sip:userB@ims...
        +Call-ID: [email protected]
        +CSeq: 1 INVITE
        +Contact: sip:[email protected]
        +Require: precondition
        +Supported: 100rel, precondition
        +Content-Type: application/sdp
        +SDP_Offer
    }
    class SDP_Offer {
        +Version: v=0
        +Origin: o=- session-id IN IP4
        +Connection: c=IN IP4 10.1.2.3
        +Media: m=audio 49152 RTP/AVP 96 97 98
        +Bandwidth: b=AS:41
        +Precondition_Attrs
        +Codec_Attrs
    }
    class Precondition_Attrs {
        +curr:qos local none
        +curr:qos remote none
        +des:qos mandatory local sendrecv
        +des:qos mandatory remote sendrecv
        +conf:qos remote sendrecv
    }
    class Codec_Attrs {
        +rtpmap:96 EVS/16000
        +fmtp:96 br=5.9-24.4
        +rtpmap:97 AMR-WB/16000
        +rtpmap:98 telephone-event
        +ptime:20
        +maxptime:240
    }
    SIP_INVITE --> SDP_Offer
    SDP_Offer --> Precondition_Attrs
    SDP_Offer --> Codec_Attrs