LTE考题知识点复习

LTE

专题

大纲随机接入知识点寻呼时机知识点路测知识点RE分布切换相关知识点复习一些计算题的讲解切换--事件介绍LTE系统是根据UE上报的事件来决定是否执行切换的。不同的事件代表着不同的含义。其事件如下:EventA1EventA2EventA3EventA4EventA5EventB1EventB2事件介绍_A1EventA1EventA1：UE检测到主小区的能量值高于某一个门限进入EventA1的条件：离开EventA1的条件：UE在判断满足A1事件后会向网络侧发送A1报告Ms：主小区的测量结果，根据网络侧的配置可以为RSRP或者RSRQHys：网络侧配置的迟滞参数Thresh：A1的门限值事件介绍_A2EventA2EventA2：UE检测到主小区的能量值低于某一个门限进入EventA2的条件：离开EventA2的条件：UE在判断满足A2事件后会向网络侧发送A2报告Ms：主小区的测量结果，根据网络侧的配置可以为RSRP或者RSRQHys：网络侧配置的迟滞参数Thresh：A2的门限值事件介绍_A3EventA3EventA3：UE检测到邻区比主小区的能量值好进入EventA3的条件：离开EventA3的条件：UE在判断满足A3事件后会向网络侧发送A3报告Ms：主小区的测量结果，根据网络侧的配置可以为RSRP或者RSRQOfs：主小区频点的偏移量Ocs：主小区的小区偏移量Off：A3事件的偏移量Mn：邻区的测量结果Ofn：邻区的频点偏移量Ocn：邻区的小区偏移量Hys：网络侧配置的迟滞参数事件介绍_A4EventA4EventA4：UE检测到邻区信号质量比某一个门限值高进入EventA4的条件：离开EventA4的条件：UE在判断满足A4事件后会向网络侧发送A4报告Mn：邻区的测量结果Ofn：邻区的频点偏移量Ocn：邻区的小区偏移量Hys：网络侧配置的迟滞参数Thresh：A4事件的门限值事件介绍_A5EventA5EventA5：UE检测到主小区信号质量比某一个门限值低&邻区信号

质量高于某一个门限值进入EventA5的条件：离开EventA5的条件：UE在判断满足A5事件后会向网络侧发送A4报告Ms：小区的测量结果Thresh1：A5事件的主小区门限值Mn：邻区的测量结果Ofn：邻区的频点偏移量Ocn：邻区的小区偏移量Hys：网络侧配置的迟滞参数Thresh2：A5事件的邻区的门限值事件介绍_B1EventB1EventB1：UE检测到异系统邻区信号质量比某一个门限值高进入EventB1的条件：离开EventB1的条件：UE在判断满足B1事件后会向网络侧发送B1报告Mn：邻区的测量结果Ofn：邻区的频点偏移量Hys：网络侧配置的迟滞参数Thresh：B1事件的邻区的门限值事件介绍_B2EventB2EventB2：UE检测到主小区低于某个门限值&异系统邻区信号质量比某

一个门限值高进入EventB2的条件：离开EventB2的条件：UE在判断满足B2事件后会向网络侧发送B2报告Ms：主小区的测量结果Thresh1：B2事件主小区的门限值Mn：邻区的测量结果Ofn：邻区的频点偏移量Hys：网络侧配置的迟滞参数Thresh2：B2事件的邻区的门限值事件介绍_小结同频之间的切换，一般是根据A3事件来触发切换的异频之间的切换，不同的厂家有不同的算法，可以根据A3，也可以根据A4异系统之间的切换，主要是根据B1和B2事件触发的切换分类切换分类按照随机接入类型竞争型的随机接入非竞争的随机接入按照切换的区域eNB内的切换eNB间的切换按照切换时候接口X2接口类型的切换S1接口类型的切换按照切换小区间频点分类同频切换异频切换按照切换小区间是否属于同一个系统LTE内的切换LTE和其他系统间的切换eNB间通过X2口切换的流程_1HO-command,X2dataforwardingtunnel,…X2AP:HandoverRequesttargetcell,servingMME&SAEGW,…RRC:MeasurementControlMMEECM_ConnectedServingGateway(SGW)PacketDatasourceeNBtargeteNBRRC:MeasurementReportHODecisionAdmissionControl:allocatesresourcesforincomingUEX2AP:HandoverRequestAckRRC:HandoverCommandtargetcelldescription,C-RNTI,…detachsourcecellsync.targetcellforwardbufferedDLpacketsbufferingofDLpacketsfromoldeNBDLPacketDataeNB间通过X2口切换的流程_2UpdateBearerResponseUpdateBearerRequestS1AP:HandoverCompletePathSwitchRequestMMEServingGateway(SGW)targeteNBIP/TEID,…sourceeNBtargeteNBSynchronizationULAllocation+timingadvanceRRC:HandoverConfirmtargeteNBIP/TEID,…switchDLPathnewSGW-S1IP/TEID,…S1AP:HandoverCompleteAckPathSwitchReq.Ack.newSGW-S1IP/TEID,…X2AP:ReleaseResourcesflushDLbuffersDLPacketDatareleaseresourcesPacketDataPacketDataforwardsDLpacketsandacceptsULpackets切换小结LTE没有软切换，只有硬切换切换整个过程是由网络侧控制的，源eNB是在切换成功后，才释放掉UE的上下文切换过程中，平安算法不会发生变化Paging一个用户的IMSI为448835805669362，现网配置如下，请计算该用户接收寻呼的时刻寻呼——根本概念寻呼发起场景IDLE状态下当终端作为被叫时，发起寻呼以完成呼叫建立MME发起通知终端〔RRC_IDLE&RRCConnected〕系统消息改变通知具有ETWS能力的UE地震及海啸告警信息eNodeB发起将告警信息告知有CMAS能力的UE。

寻呼——根本概念TA〔TrackingArea，跟踪区域〕在LTE网络中，空闲态下的UE位置能用TrackingArea表述，一个eNB中的不同小区能属于不同TA，但一个小区只能属于一个TADRX：〔非连续接收方式〕即非连续的监听PDCCH信道，包括IDLEDRX与ACTIVEDRX，paging过程中所使用的为IDLEDRX。终端在特定的子帧里面监听PDCCH信道以接收寻呼消息，目的是为了尽可能的降低IDLE模式下UE的电力消耗。

寻呼——寻呼过程寻呼消息的承载

寻呼消息的

寻呼——寻呼过程网络侧〔发送〕MME在UE相应的寻呼时机〔PO〕通过S1接口向包含UE所注册TA中小区的eNB发送Paging消息。eNB中的不同小区可以属于不同的TA相关的eNB在收到Paging消息后在消息中所含有TA内的所有小区经过无线空口寻呼。Paging消息中主要包含：UE的S-TMSI/IMSI、寻呼的TAI区域、系统消息变更通知、ETWS与CMAS消息。一条寻呼消息网络侧可能会标识出多个UE(前提是多个UE的寻呼时机是一样的〕，其中每个UE均有唯一个PagingRecord与其对应。

寻呼——寻呼过程UE侧〔接收〕UE根据UE-ID及其它配置参数计算出自己的寻呼时间，并在寻呼时间内监听PDCCH信道。如果在此寻呼时间内PDCCH信道携带P-RNTI那么表示此为寻呼信息。P-RNTI〔pagingRNTI〕，在PDCCH上用于指示存在寻呼讯息。在检测到P-RNTI后，UE将解读在PDSCH信道上的详细的寻呼消息pagingmessage包含具体的被寻呼的UE-id，UE将自己的标识与其比照，如果不匹配，那么UE会丢弃这个信息并依照DRX周期进入休眠

寻呼——寻呼过程UE侧〔接收〕如果UE-id相互匹配，那么UE按照Paging消息中内容完成后续步骤。当Paging消息中包含systemInfoModification，UE那么重新获取必须的系统消息。当Paging消息中包含ETWSIndication,UE将立即重新获取SystemInformation11寻呼——根本概念PO〔pagingoccasion〕由于UE采用DRX〔非连续接受〕方式接受寻呼消息，在特定的子帧监听PDCCH，此特定子帧即为POPF〔pagingframe〕PO所在的无线帧称为PF，一个PF能包含一个或者多个PO

寻呼——寻呼时机寻呼时机的计算PO与PF根据DRX参数〔由系统消息提供〕通过以下公式确定：PF确实定：SFNmodT=(TdivN)*(UE_IDmodN)PO确实定：i_s=floor(UE_ID/N)modNs

其中T：UE的DRX周期，其取值范围[320ms,640ms,1280ms,2560ms]nB:4T,2T,T,T/2,T/4,T/8,T/16,T/32.其代表寻呼的密度，T的系数代表每个无线帧有多少子帧用于寻呼，4T代表一个无线帧有4个子帧用于寻呼。N:min(T,nB)Ns:max(1,nB/T)UE_ID:IMSImod1024

寻呼——寻呼时机子帧映射关系NsPOwheni_s=0POwheni_s=1POwheni_s=2POwheni_s=319N/AN/AN/A249N/AN/A40459NsPOwheni_s=0POwheni_s=1POwheni_s=2POwheni_s=310N/AN/AN/A205N/AN/A40156FDDTDD〔allUL/DLconfigurations〕Paging一个用户的IMSI为448835805669362，现网配置如下，请计算该用户接收寻呼的时刻UE-ID=448835805669362MOD1024=1010N=min(T,nB)=min(128,128)=128Ns=max(1,nB/T)=max(1,1)=1SFNMODT=〔T/N〕*(UE-IDMODN)=128/128*(1010mod128)=1*114=114Is=floor(UE_ID/N)modNs=floor(1010/128)modNs=floor(7.89)mod1=0随机接入专题请根据给出的参数设置，指出不合理的地方，会造成怎样的后果，并给出修改建议〔不考虑具体应用场景〕

随机接入随机接入作用

取得与eNodeB之间的上行同步

申请上行资源随机接入应用场景随机接入类型应用场景触发竞争随机接入RRC-IDLE状态下初始接入，即RRC连接建立UE自主触发无线链路失败后初始接入，即RRC连接重建上行数据到达，且UE空口上行失步切换UE根据eNodeB指示发起接入（优先选择非竞争随机接入）下行数据到达，且UE空口上行失步非竞争随机接入下行数据到达，且UE空口上行失步辅助定位，网络利用随机接入获得时间提前量TA切换

随机接入发起随机接入过程所需信息information说明prach-ConfigIndex指示发送随机接入前导的PRACH资源已经准备好groupsofRandomAccessPreambles可用的随机接入前导ra-ResponseWindowSize接收随机接入响应的窗口大小参数powerRampingStep功率提升步长preambleTransMaxUE最大发送Preamble的个数preambleInitialReceivedTargetPowereNB期待的前导序列功率，这个值太高了，会造成干扰，太低了可能无法收到前导序列

DELTA_PREAMBLE5种前导序列，每一种格式都对应一个基准选择发射功率maxHARQ-Msg3TxMSG3HARQ重传最大次数mac-ContentionResolutionTimer竞争消除定时器

随机接入发起随机接入过程所需信息

竞争随机接入竞争随机接入根本过程步骤一，随机接入资源的选择和前导信号的发送步骤二，随机接入响应的接收步骤三，MSG3的发送步骤四，竞争解决随机接入前导选择每个小区可用的Preamble码字总数为64个〔一般预留24个用于切换〕eNodeB可将其局部或者全部用于竞争随机接入随机接入Preamble码分为GroupA与GroupB

1：PCMAX–preambleInitialReceivedTargetPower–deltaPreambleMsg3–messagePowerOffsetGroupB>pathloss2：messageSizeGroupA<MACPDU的长度

当满足以上两个公式，那么选用GroupB否那么选GroupA

竞争随机接入——随机接入前导发送集合场景GroupA

Msg3较小或者路损较大GroupBMsg3较大或者路损较小竞争随机接入——随机接入前导发送Preamble的格式根据系统消息选择前导格式竞争随机接入——随机接入前导发送PRACH信道

竞争随机接入——随机接入前导发送初始发送功率

preambleInitialReceivedTargetPower初始发送功率

下行路径损耗(平均RSRP得到)

前导重传ra-ResponseWindowSizepowerRampingSteppreambleTransMax

竞争随机接入——随机响应的接收监听时刻发送前导序列后三个子帧开始，持续ra-ResponseWindowSize个子帧数窗口大小由SIB2获得监听信道eNB在PDSCH上发送RAR，UE使用一个预留给随机接入响应使用的ID(RA-RNTI)来监听PDCCH，用于解码DL-SCHRAR包含内容前导序列索引号时间调整信息、资源调度信息〔也就是分配给该用户的上行资源〕临时RNTI

竞争随机接入——Msg3发送Msg3包含主要信息

此外还包含TMSI或者UEidentity

场景内容初始随机接入RRC连接建立请求无线链路失败触发的随机接入发送RRC连接重建请求切换触发的随机接入RRC连接重配置完成消息和C-RNTIMAC控制单元，用于向网络确认切换完成上行失步出发的随机接入上行传输数据和C-RNTIMAC控制单元

竞争随机接入——竞争解决Msg3发送后开启，UE竞争解决定时器，并监视PDCCH信道，进行竞争解决，直到竞争解决成功或竞争解决定时器超时eNodeB回复Msg4，其中包含Msg3带上来的TMSI或者UEidentityUE根据比较Msg4中的TMSI或者UEidentity，判定自己是否随机接入是否成功临时C-RNTI设置为C-RNTI，同时丢弃临时C-RNTI，然后确认随机接入成功

非竞争随机接入非竞争随机接入主要过程UE从网络获得随机接入资源UE根据网络分配的随机接入资源向网络发起随机接入请求UE通过自己的RA-RNTI在PDCCH上接收随机接入响应〔RAR〕随机接入专题如何选择preamble？Preamble如何生成？Preamble发送的时、频位置，需要的资源？ZC根序列有837个，为什么需要这么多？邻区之间的Prach参数怎么配置，才不会碰撞？随机接入专题—涉及的参数numberOfRA-PreamblesgroupsofRandomAccessPreamblesra-ResponseWindowSizepowerRampingSteppreambleTransMaxpreambleInitialReceivedTargetPower

DELTA_PREAMBLEmaxHARQ-Msg3Txmac-ContentionResolutionTimerprach-ConfigIndexrootSequenceIndexhighSpeedFlagzeroCorrelationZoneConfigprach-FreqOffsetPrach格式选择Prach格式选择随机接入专题—prach-ConfigIndexPRACH

configurationIndexPreamble

FormatDensityPer10msVersion

PRACH

configurationIndexPreamble

FormatDensityPer10msVersion

000.503220.52100.5133210200.523421130103522040113623050123724060203825070213926080224030.5090304130.51100314230.5211032433101204044311130414532014042463301505047340160514840.50170524940.51180605040.5219061514102010.50524112110.51534202210.52544302311055440241115645025120574602613058N/AN/AN/A2714059N/AN/AN/A2815060N/AN/AN/A2916061N/AN/AN/A3020.5062N/AN/AN/A3120.5163N/AN/AN/A随机接入专题—prach-ConfigIndexPRACHconfigurationIndex(SeeTable5.7.1-3)UL/DLconfiguration(SeeTable4.2-2)01234560(0,1,0,2)(0,1,0,1)(0,1,0,0)(0,1,0,2)(0,1,0,1)(0,1,0,0)(0,1,0,2)1(0,2,0,2)(0,2,0,1)(0,2,0,0)(0,2,0,2)(0,2,0,1)(0,2,0,0)(0,2,0,2)2(0,1,1,2)(0,1,1,1)(0,1,1,0)(0,1,0,1)(0,1,0,0)N/A(0,1,1,1)3(0,0,0,2)(0,0,0,1)(0,0,0,0)(0,0,0,2)(0,0,0,1)(0,0,0,0)(0,0,0,2)4(0,0,1,2)(0,0,1,1)(0,0,1,0)(0,0,0,1)(0,0,0,0)N/A(0,0,1,1)5(0,0,0,1)(0,0,0,0)N/A(0,0,0,0)N/AN/A(0,0,0,1)6(0,0,0,2)(0,0,1,2)(0,0,0,1)(0,0,1,1)(0,0,0,0)(0,0,1,0)(0,0,0,1)(0,0,0,2)(0,0,0,0)(0,0,0,1)(0,0,0,0)(1,0,0,0)(0,0,0,2)(0,0,1,1)7(0,0,0,1)(0,0,1,1)(0,0,0,0)(0,0,1,0)N/A(0,0,0,0)(0,0,0,2)N/AN/A(0,0,0,1)(0,0,1,0)8(0,0,0,0)(0,0,1,0)N/AN/A(0,0,0,0)(0,0,0,1)N/AN/A(0,0,0,0)(0,0,1,1)9(0,0,0,1)(0,0,0,2)(0,0,1,2)(0,0,0,0)(0,0,0,1)(0,0,1,1)(0,0,0,0)(0,0,1,0)(1,0,0,0)(0,0,0,0)(0,0,0,1)(0,0,0,2)(0,0,0,0)(0,0,0,1)(1,0,0,1)(0,0,0,0)(1,0,0,0)(2,0,0,0)(0,0,0,1)(0,0,0,2)(0,0,1,1)10(0,0,0,0)(0,0,1,0)(0,0,1,1)(0,0,0,1)(0,0,1,0)(0,0,1,1)(0,0,0,0)(0,0,1,0)(1,0,1,0)N/A(0,0,0,0)(0,0,0,1)(1,0,0,0)N/A(0,0,0,0)(0,0,0,2)(0,0,1,0)11N/A(0,0,0,0)(0,0,0,1)(0,0,1,0)N/AN/AN/AN/A(0,0,0,1)(0,0,1,0)(0,0,1,1)12(0,0,0,1)(0,0,0,2)(0,0,1,1)(0,0,1,2)(0,0,0,0)(0,0,0,1)(0,0,1,0)(0,0,1,1)(0,0,0,0)(0,0,1,0)(1,0,0,0)(1,0,1,0)(0,0,0,0)(0,0,0,1)(0,0,0,2)(1,0,0,2)(0,0,0,0)(0,0,0,1)(1,0,0,0)(1,0,0,1)(0,0,0,0)(1,0,0,0)(2,0,0,0)(3,0,0,0)(0,0,0,1)(0,0,0,2)(0,0,1,0)(0,0,1,1)prach-FreqOffset和fu一起决定了频率起始位置随机接入专题—prach-ConfigIndex〔小结〕prach-ConfigIndexFormat格式发送的时机频率位置(部分确定)随机接入的密度(每10ms次数)随机接入专题—preamble产生根序列Format0~3Nzc为839，根序列分32组Formart4Nzc为139，根序列分7组rootSequenceIndex确定了起始的逻辑根序列号循环位移Format0~3，分为Unrestricted/Restricted，Ncs值取决于zeroCorrelationZoneConfig和highSpeedFlagFormat4支持7种Ncspreamble64种preamble对于不同的Ncs,需要的根序列个数不同Format0~3Nzc839，format4Nzc139随机接入专题—preamble产生configurationvalueUnrestrictedsetRestrictedset00151131821522318264223252638632467385584668959821076100119312812119158131672021427923715419-configurationvalue021426384105126157N/A8N/A9N/A10N/A11N/A12N/A13N/A14N/A15N/AFormat0~3Format4Ncs确定，根据参数zeroCorrelationZoneConfig查表得到随机接入专题—preamble产生LogicalrootsequencenumberPhysicalrootsequencenumber(inincreasingorderofthecorrespondinglogicalsequencenumber)0–23129,710,140,699,120,719,210,629,168,671,84,755,105,734,93,746,70,769,60,7792,837,1,83824–2956,783,112,727,148,69130–3580,759,42,797,40,79936–4135,804,73,766,146,69342–5131,808,28,811,30,809,27,812,29,81052–6324,815,48,791,68,771,74,765,178,661,136,70364–7586,753,78,761,43,796,39,800,20,819,21,81876–8995,744,202,637,190,649,181,658,137,702,125,714,151,68890–115217,622,128,711,142,697,122,717,203,636,118,721,110,729,89,750,103,736,61,778,55,784,15,824,14,825116–13512,827,23,816,34,805,37,802,46,793,207,632,179,660,145,694,130,709,223,616136–167228,611,227,612,132,707,133,706,143,696,135,704,161,678,201,638,173,666,106,733,83,756,91,748,66,773,53,786,10,829,9,830168–2037,832,8,831,16,823,47,792,64,775,57,782,104,735,101,738,108,731,208,631,184,655,197,642,191,648,121,718,141,698,149,690,216,623,218,621204–263152,687,144,695,134,705,138,701,199,640,162,677,176,663,119,720,158,681,164,675,174,665,171,668,170,669,87,752,169,670,88,751,107,732,81,758,82,757,100,739,98,741,71,768,59,780,65,774,50,789,49,790,26,813,17,822,13,826,6,833264–3275,834,33,806,51,788,75,764,99,740,96,743,97,742,166,673,172,667,175,664,187,652,163,676,185,654,200,639,114,725,189,650,115,724,194,645,195,644,192,647,182,657,157,682,156,683,211,628,154,685,123,716,139,700,212,627,153,686,213,626,215,624,150,689328–383225,614,224,615,221,618,220,619,127,712,147,692,124,715,193,646,205,634,206,633,116,723,160,679,186,653,167,672,79,760,85,754,77,762,92,747,58,781,62,777,69,770,54,785,36,803,32,807,25,814,18,821,11,828,4,835384–4553,836,19,820,22,817,41,798,38,801,44,795,52,787,45,794,63,776,67,772,72767,76,763,94,745,102,737,90,749,109,730,165,674,111,728,209,630,204,635,117,722,188,651,159,680,198,641,113,726,183,656,180,659,177,662,196,643,155,684,214,625,126,713,131,708,219,620,222,617,226,613456–513230,609,232,607,262,577,252,587,418,421,416,423,413,426,411,428,376,463,395,444,283,556,285,554,379,460,390,449,363,476,384,455,388,451,386,453,361,478,387,452,360,479,310,529,354,485,328,511,315,524,337,502,349,490,335,504,324,515514–561323,516,320,519,334,505,359,480,295,544,385,454,292,547,291,548,381,458,399,440,380,459,397,442,369,470,377,462,410,429,407,432,281,558,414,425,247,592,277,562,271,568,272,567,264,575,259,580562–629237,602,239,600,244,595,243,596,275,564,278,561,250,589,246,593,417,422,248,591,394,445,393,446,370,469,365,474,300,539,299,540,364,475,362,477,298,541,312,527,313,526,314,525,353,486,352,487,343,496,327,512,350,489,326,513,319,520,332,507,333,506,348,491,347,492,322,517630–659330,509,338,501,341,498,340,499,342,497,301,538,366,473,401,438,371,468,408,431,375,464,249,590,269,570,238,601,234,605660–707257,582,273,566,255,584,254,585,245,594,251,588,412,427,372,467,282,557,403,436,396,443,392,447,391,448,382,457,389,450,294,545,297,542,311,528,344,495,345,494,318,521,331,508,325,514,321,518708–729346,493,339,500,351,488,306,533,289,550,400,439,378,461,374,465,415,424,270,569,241,598730–751231,608,260,579,268,571,276,563,409,430,398,441,290,549,304,535,308,531,358,481,316,523752–765293,546,288,551,284,555,368,471,253,586,256,583,263,576766–777242,597,274,565,402,437,383,456,357,482,329,510778–789317,522,307,532,286,553,287,552,266,573,261,578790–795236,603,303,536,356,483796