LTE切换优化专题参数功能和优化思路.docx
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1、LTE切换优化专题参数功能和优化思路内容: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,A5事件 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,A5事件 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,A5事件 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eNo
2、deB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,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1。 LTE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
3、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: l UE上报B2测量报告:Measurement Report l UE在LTE小区收到往3G切换命令:MobilityFromEutranCommand l 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 UE 切换准备信令流程 Source eNodeB Target RNC Source MME Target Target SGSN Serving GW Serving GW
4、 PDN GW HSS Uplink and Downlink User Plane PDUs 1. Handover Initiation 2. H andover Required 3. Forward Relocation Request 4. Create Session Request 4a. Create Session Response 5. Relocation Request 5a. Relocation Request Acknowledge 6. Create Indirect Data Forwarding Tunnel Request 6a. Create Indir
5、ect Data Forwarding Tunnel Response 7. Forward Relocation Response reate Indirect Data Forwarding Tunnel Request 8. C reate Indirect Data Forwarding Tunnel Response 8a . C2 切换执行信令流程 UE Source eNodeB Target RNC Source MME Target Target SGSN Serving GW Serving GW PDN GW HSS Uplink and Downlink User Pl
6、ane PDUs 1. Handover Command 2. HO from E-UTRAN Command - 4. UTRAN Iu Access Procedures4a. Handover to UTRAN Complete Sending of uplink data possible Downlink User Plane PDUs If Direct Forwarding applies Via Target SGSN in case Direct Tunnel is not used 5. Relocation Complete 6. Forward Relocation C
7、omplete 6a. Forward Relocation Complete Acknowledge 7. Modify Bearer Request If Indirect Forwarding applies. For Serving GW relocation Steps 7, 8 and 9, and the following User Plane path, will be handled by Target Serving GW (A) 8. Modify Bearer Request 8a. Modify Bearer Response 9. Modify Bearer Re
8、sponse Uplink and Downlink User Plane PDUs (Via Target SGSN if Direct Tunnel is not used) 10. Routeing Area Update procedure 11. Delete Session Request 11b. Release Resources 11a. Delete Session Response (B) 12. Delete Indirect Data Forwarding Tunnel 1.1.2 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 UE S
9、ource eNodeB Target BSS Source MME Target SGSN Target Serving GW Serving GW PDN GW HSS Uplink and Downlink User Plane PDUs 1. Handover Initiation 2. Handover Required 3. Forward Relocation Request 4. Create Session Request 4a. Create Session Response 5. PS Handover Request 5a. PS Handover Request Ac
10、knowledge 6. Create Indirect Data Forwarding Tunnel Request 6a. Create Indirect Data Forwarding Tunnel Response 7. Forward Relocation Response 8. Create Indirect Data Forwarding Tunnel Request 8a. Create Indirect Data Forwarding Tunnel Response 2. 切换执行信令流程 UE Source eNodeB Target BSS Source MME Targ
11、et Target SGSN Serving GW Serving GW Uplink and Downlink User Plane PDUs 1. Handover Command 2. HO from E-UTRAN Command PDN GW HSS 4. GERAN A/Gb Access Procedures 5. XID Response Downlink User Plane PDUs Sending of uplink data possible Only if ”Direct Forwarding” applies Only if ”Indirect Forwarding
12、” applies 6. PS Handover Complete 7. XID Response 8. Forward Relocation Complete Notification 8a. Forward Relocation Complete Acknowledge 9. Modify Bearer Request For Serving GW relocation Steps 9, 10 and 11, and the following User Plane path, will be handled by Target Serving GW 12. XID Negotiation
13、 for LLC ADM 12a. SABM UA exchange re-establishment and XID negotiation for LLC ABM) Uplink and Downlink User Plane PDUs 13. Routeing Area Update procedure 14. Delete Session Request 14b. Release Resource (B) 14a. Delete Session Response (A) 10. Modify Bearer Request 10a. Modify Bearer Response 11.
14、Modify Bearer Response 1.1.3 3G到LTE的切换 3G到LTE的具体切换信令流程: 1. 切换准备信令流程 UE Source RNC Target eNodeB Source SGSN Target MME Serving GW Target Serving GW PDN GW HSS Uplink and Downlink User Plane PDUs (via Source SGSN in case Direct Tunnel is not used) 1. Handover Initiation 2. Relocation Required 3. Forw
15、ard Relocation Request 4. Create Session Request 4a. Create Session Response 5. Handover Request 5a. Handover Request Acknowledge 6 . Create Indirect Data Forwarding Tunnel Request 6 a . Create Indirect Data Forwarding Tunnel Response 7 . Forward Relocation Response . Create Indirect Data Forwarding
16、 Tunnel Request8 8a. Create Indirect Data Forwarding Tunnel Response 2. 切换执行信令流程 UE Source RNC Target eNodeB Source SGSN Target MME Target Serving GW Serving GW PDN GW HSS Uplink and Downlink User Plane PDUs (via Source SGSN if Direct Tunnel is not used) 1. Relocation Command 2. HO from UTRAN Comman
17、d 4. E-UTRAN Access Procedures 5. HO to E-UTRAN Complete Sending of uplink data possible Downlink Payload User Plane PDUs (via Source SGSN if Direct Tunnel is not used) If Direct Forwarding applies Via Source SGSN in case Direct Tunnel is not used If Indirect Forwarding applies 6. Handover Notify 7.
18、 Forward Relocation Complete Notification 7a. Forward Relocation Complete Acknowledge 8. Modify Bearer Request For Serving GW relocation Steps 8, 9 and 10, and the following User Plane path, will be handled by Target Serving GW (A) 10. Modify Bearer Response 9. Modify Bearer Request 9a. Modify Beare
19、r Response Uplink and Downlink User Plane PDUs 11. Tracking Area Update procedure 12. Delete Session Request 12b. Iu Release Procedure (B) 12a. Delete Session Response 13. Delete Bearer 1.1.4 2G到LTE的切换 2G到LTE的具体切换信令流程: 1. 切换准备信令流程 UE Source BSS Target eNodeB Source SGSN Target MME Target Serving GW
20、Serving GW PDN GW HSS Uplink and Downlink User Plane PDUs 1. Handover Initiation 2. PS Handover Required 3. Forward Relocation Request 4. Create Session Request 4a. Create Session Response 5. Handover Request 5a. handover Request Acknowledge 6. Create Indirect Data Forwarding Tunnel Request 6a. Crea
21、te Indirect Data Forwarding Tunnel Response 7. Forward Relocation Response 8. Create Indirect Data Forwarding Tunnel Request 8a. Create Indirect Data Forwarding Tunnel Response 2. 切换执行信令流程 UE Source BSS Target eNodeB Source SGSN Target MME Target Serving GW Serving GW PDN GW HSS Uplink and Downlink
22、User Plane PDUs Only if Direct Forwarding applies Only if Indirect Forwarding applies 1. PS HO Required Acknowledge 2. PS Handover Command 4. E-UTRAN Access Procedures 5. HO to E-UTRAN Complete 6. Handover Notify Sending of uplink data 7. Forward Relocation Complete Notification possible 7a. Forward
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