ESRVCC准备阶段优化提升
一、eSRVCC信令流程1) UE发测量报告给eNb;2) 基于测量报告，源eNb触发到GERAN的SRVCC切换流程；3) 源eNb发送Handover Required 消息给源MME，消息中携带Target ID, generic Source to Target Transparent Container, SRVCC HO Indication等信息；4) 基于话音承载的QCI及SRVCC切换标识，源MME分离话音承载与非话音承载，并初始化PS-CS切换流程；5) MME发送SRVCC PS to CS Request消息给eMSC，消息中携带IMSI, Target ID, STN-SR, CMSISDN, generic Source to Target Transparent Container, MM Context, Emergency Indication等信息；6) eMSC发送Prepare Handover Request消息给目标MSC准备切换；7) 目标MSC发送Handover Request/ Acknowledge消息通知目标BSS分配资源；8) 目标MSC发送Prepare Handover Response消息给eMSC，告知切换资源准备情况；9) 目标MSC与MGW之间建立连接；10) eMSC发送SIP-INVITE消息给IMS侧触发会话切换；11) 远端更新会话SDP；12) 释放原有的IMS接入链路；13) eMSC发送SRVCC PS to CS Response消息给MME，确认SRVCC切换装备完成；14) MME发送Handover Command消息给源eNb，其中包含目标小区的切换相关信息；15) 源eNb发Handover指令给UE进行切换；16) UE切换到GERAN;17) UE切换完成，发送Handover Complete消息给Target BSS；18) 目标BSS发Handover Complete消息给eMSC;19) eMSC发送SRVCC PS to CS Complete Notification消息给MME，通知其UE已经转到目标网络侧；20) MME回SRVCC PS to CS Complete Acknowledge消息确认SRVCC切换成功。21) MME触发释放该UE话音专用承载及ERAB资源；二、ESRVCC错误代码在对eSRVCC切换失败所处网元初步定界的基础上，进一步关联Sv错误码-GTPv2原因-S1错误码，定位出失败原因，归纳如下表：SV错误码、网管统计错误码子码、统计结果定界定位SV为0MME统计没能发出切换请求数据定义错误MME漏定SV数据，需补定LACSv-Cancelled by source systemCancelled by UE4G无线环境变化或挂机根据是否有BYE发出，定位是无线环境好转导致UE发handover cancel；还是一方挂机释放Cancelled due to Service request4G无线问题RRC释放后手机发出Service request，定位为LTE无线环境恶化，Cancelled due to TAU4G无线问题TAC边界的TAU请求Cancelled due to Ts1relocoverall-expiry2G无线问题根据2G小区的KPI，定位2G弱覆盖，高干扰，拥塞等造成UE切换过程过久导致超时Sv-UnspecifiedGTPv2-No resources available2G小区问题根据2G小区的KPI，定位小区拥塞还是载频退服导致资源不足GTPv2- Request rejected(reason not specified)终端问题定位手机能力不能执行eSRVCC切换，UE连续发送SRVCC请求导致Sv-Session leg establish errorIMS Session Transfer errorIMS问题从IMS侧定位SIP信令问题BYE or REL流程问题VOLTE通话已经完成 ，不算失败；BSRVCC不支持Sv-Unknown target ID数据定义错误根据各节点的切换完成率等统计来定位：a)eMSC上缺失外部小区数据；b)Target MSC缺少小区数据；c)eNodeb上报的小区属无效小区Sv-Failure with target system数据定义错误根据各节点的切换完成率等统计来定位：a)eMSC漏定外部LAI；b）目标MSC漏定内部CGI；c）或eNB邻区配置无效目标小区，需删除三、ESRVCC准备阶段成功率优化问题描述：由于现网阶段的ESRVCC准备阶段切换成功率低，采取部分小区调整参数提升。实施方案：1、【参数定义和修改目的】reportAmountB2 （B2上报次数），由0（无限次)->1次，减少准备阶段失败后重发次数，提升ESRVCC准备阶段成功率。调整小区：1、小区汇总：4236个小区调整后网管KPI指标及走势：（12日修改）1、全网后台KPI指标：Date_IDpmHoPrepAttpmHoPrepSuccpmHoExeAttpmHoExeSucceSrvccHo_preeSrvccHo_exeeSrvccHoSR2017/7/57573373798737986985697.44%94.66%92.24%2017/7/67647873536735356989796.15%95.05%91.40%2017/7/78174176108761107190193.11%94.47%87.96%2017/7/87379771978719786809597.54%94.61%92.27%2017/7/97330671495714946769097.53%94.68%92.34%2017/7/107950276804768037297596.61%95.02%91.79%2017/7/118093878660786607478497.19%95.07%92.40%调整前平均7735674626746257074396.51%94.79%91.49%2017/7/129870396423964209075197.69%94.12%91.95%2017/7/139768695820958199037798.09%94.32%92.52%2017/7/149971397795977949198098.08%94.05%92.25%2017/7/159191790137901338546698.06%94.82%92.99%2017/7/168911287123871218196497.77%94.08%91.98%2017/7/179760795774957749038898.12%94.38%92.60%2017/7/189827596524965249073198.22%94.00%92.32%2017/7/1910035698320983199273197.97%94.32%92.40%调整后平均9638194499944988909198.04%94.28%92.44%变化190241987319872183481.54%-0.51%0.95%2、调整小区后台KPI指标：Date_IDpmHoPrepAttpmHoPrepSuccpmHoExeAttpmHoExeSucceSrvccHo_preeSrvccHo_exeeSrvccHoSR2017/7/51746416835168351586596.40%94.24%90.84%2017/7/61869917091170911600891.40%93.66%85.61%2017/7/72181417441174411597979.95%91.62%73.25%2017/7/81689216338163381520396.72%93.05%90.00%2017/7/91695216353163531514796.47%92.63%89.35%2017/7/101871917412174121638393.02%94.09%87.52%2017/7/111899618065180651696495.10%93.91%89.30%调整前平均1850517076170761593692.72%93.31%86.55%2017/7/121836017949179471677997.76%93.49%91.40%2017/7/131839718139181401698198.60%93.61%92.30%2017/7/141885718578185781725998.52%92.90%91.53%2017/7/151715016889168881606498.48%95.12%93.67%2017/7/161664916369163691542498.32%94.23%92.64%2017/7/171868818380183801721198.35%93.64%92.10%2017/7/181825217973179731693098.47%94.20%92.76%2017/7/191646216226162261520698.57%93.71%92.37%调整后平均1785217563175631648298.38%93.86%92.35%变化-6534864865465.66%0.55%5.79%3、全网准备阶段申请数走势：4、全网准备阶段成功率走势：5、调整小区申请数走势：6、调整小区准备阶段成功率走势：结论：1、通过对ESRVCC准备阶段成功率低采取对B2上报次数后，修改小区的准备阶段切换成功率由92.72%提升到98.38%，提升了5.66%；总体ESRVCC切换成功率由86.55%提升到92.35%，提升了5.79%；2、全网准备成功率由96.51%提升到98.04%，提升了1.54%，全网总体ESRVCC成功率由91.49%提升到92.44%，提升了0.95%。
