LTE切换优化专题-参数功能和优化思路.docx

内容：参数功能及设置、切换原理、信令流程、优化案例等1 LTE切换原理1.1 Intra-eNodeB 切换触发事件：A3事件（同频切换），A5事件（异频切换）当UE从当前所处的服务小区切换到同一 eNodeB下的另一小区时，会发生 Intra-eNodeB 切换基于X2接口的切换触发事件：A3事件（同频切换），A5事件（异频切换）当两个eNodeB之间存在X2接口时，UE从当前所驻留的服务小区切换到另一 eNodeB时，可采用基于X2接口的切换基于S1接口的切换触发事件：A3事件（同频切换），A5事件（异频切换）当两个eNodeB之间不存在X2接口，或X2接口不可用时，UE从当前所驻留 的服务小区切换到另一 eNodeB时，可采用基于S1接口的切换1.1.1 LTE到3G的切换实现LTE到3G的切换首先需要满足几个前提：1. 网络侧，LTE系统和3G系统均支持LTE到3G的PS切换2. UE 侧h UE 需要支持 LTE 到 3G 的 PS 切换，UE 的 Feature Group Indicator bit 位8和bit位22数值必须为1LTE到3G切换的流程概述：1. LTE基站如果收到UE上报的A2测量报告，发现LTE的覆盖较差。

2. LTE基站通过RRC重配置消息对UE配置B2事件的测量的相关参数3. LTE基站收到B2事件的测量报告后，通过MobilityFromEutranCommand通 知UE发起到3G的切换4. LTE基站收到UE上发的MobilityToUtranComplete，切换成功主要的LTE RRC空口信令：• UE 上报 B2 测量报告：Measurement Report• UE 在 LTE 小区收到往 3G 切换命令：MobilityFromEutranCommand• UE 向 LTE 小区反馈到 3G 切换成功：MobilityToUtranComplete具体的切换信令流程如下：1. 切换准备信令流程(3GPP 23.401)UESourceeNodeBTarget RNC Source MME 一 一 Target 一 一 一Target SGSN Serving GK PDN GW HSSn n serving gw—-Uplink and-DownlinkUser IPlaneptUs1. Handover Initiation II ■2. HandovorRoquirod3. Forward Relgcation Request4. Create Session Request^4a*_Cipate_SessiPnR£sooi ise.5 RelocationReq5a Relocatiouestn Request Ack^fwledge6. Create Indrect Data Forwarding Tunnel Reque< 7. Forward Re_8.Create_Indir^a. Create _Incirect_DataFo;warding Tunnel Respo ocation Responsestmsect-Data Forwarding Tunnel Request<-8a. Create-I^ikect. Data Forwarding TunnelResponse2. 切换执行信令流程(3GPP 23.401)〔Serving GWTargetServing GWPDN GWHSSUplink and Downlink User Plane PDUs_2. HO fromV .1 Handover.E-UTRAN CoCommandmmandl.4. UT.BAN IuAccess Procedures!4a. Handover to UTRAN £ompleteending of : plink data ! 二-possible,—'Downlink. User PJane_P.DU2.4-If Direct Forwarding applies_ 一 ViaJarget_SGSN in case DirecLTunne Lis_noi used 一If Indirect Forwarding applies.5. Relocation Complete ”』6. Forward Re6a. Forward Rocation Comple elocation Complete AcknowledgeFor anc hanServing GW relocation Steps 7, the following User Plane path, will be dled by Target Serving GW8 and 9,7. Modify Bearer Request *(A)8. Modify Bearer Recuest8a Modify Bearer Reponse.9. Modify Bearer Response_^^plink_and Downlink_Us£r_PlaDeJ'DUs. (Vja-Jargei |SGSN_if_Direct.Jinn£Lis noLu^ed)10.Routeing Area Update procedure11. Delete Session Request11b Release Resources■ ■- ■=c L . c 匾#丑 Delete Se；as^_RespDose12. Delete Indirect Data F：orwarding Tunnel1.1.2 LTE到2G的切换LTE到2G的具体切换信令流程：1.切换准备信令流程(3GPP 23.401)UESource eNodeBTarget BSSSource MMETarget SGSNServing GWTarget Serving GWPDN GWHSSUplnk-and-Dawnlink. Jser^lanjPDU2. Handover Required1. Handover Initiation I^ Forward Relocation Request.^_Greate-Ses£iQn^equesL>5. PS Handover Request5a. PS Handover Request Ac：.gAreatfi Indir^ Data Forwg^ing Tunnel Requestowledge.*6a.-Greate Jnd rect Data Forwarding TunnelResponse薄 7 Forward Relo,cation ResponseQeateJndirect -Data Forwarding Tunnel Reqiest<_8a. Greate-lndirjict-Daia -Forwarding Tunnel Response2.切换执行信令流程(3GPP 23.401)13. R(>uteing Area Update procedure Uplink and_8wn邮 HserElane.RDUs 麟14_DeleieSecsicn_R£q^esi>1.1.3 3G到LTE的切换3G到LTE的具体切换信令流程：UETarget BSSSource MMETarget SGSNServing GWSource eNodeBTarget Serviipg GWPDN GWHSS〜.HO fromA 4 1. HandoverE-UTRAN CommandCommandb Access Procedures5. XID Response GERAN A/Gending of plink data ossible :Only if "Direct Forwarding"6. PS Handoving GW relocUplink_and .Dowolink U** PlanePDUs ^Downlink Use; ElaoePDUsappliesOnly if "Indirrect Forwarding" appliesver Complete *7. XID Resp，ation Steps 9,')nse.8. Forward Relocation Complete Notification8a. ForwardRelocation Comp—9 Modify Belete Acknowle arer RequestdgeFor Seand 州 following Use] Plane path, w handle^d by Target Se ving GW12. XID Neg12a. SABM re-estalotiation for LLC0 and 11, ll beADMJA exchangeHishment and XID n(A)10. Modify fearer Rec 10a. ModifyuestBearer Response.11. Modify Bearer Responseegctiaticn for LLC ABM)14b ReleaseResourcedelete Session _Response1.切换准备信令流程(3GPP 23.401)UESourceRNCTargeteNodeBSource SGSNTarget MME Serving GWTargetServing GWPDNGWHSS一 一 * — Uplin^and I lownlinJUseuFlane £DUs -(via-Sojrce-SGSN -in ■声e-DirectTwne^i&-not-u£ed)1. Handover Initiation2. Relocation Required3 Forward Relocation Request*4d Greate-Se^ >siDQ-RespQnse5 Handover5a一 HandoveRequest AcknowledgeGreatjIndiiecUData^Fowarding TunneRequestJ Forward Reloc^6a^Create4nd rect-Data Forwarding Tunnel Response ation Response一 S^GreateJndire ct-Data -Forwarding Tunnel Request^-ga^Greaie-Indirect-Data -Forwardng Tunnel Response2.切换执行信令流程(3GPP 23.401)。