Random_Access_Process.ppt

Company Confidential Copyright 2008 TietoEnator Corporation Company Confidential Copyright 2008 TietoEnator Corporation Company Confidential Copyright 2008 TietoEnator Corporation Company Confidential Copyright 2008 TietoEnator Corporation Copyright 2008 TietoEnator Corporation Copyright 2008 TietoEnator Corporation Random Access Process Contention based Chen zhaoying TDLTE_FastTrack 2012.05.23 History Date Version Author Changes 2012-05-20 0.1 Chen zhaoying First draft ,Prepare for sharing 2012-05-23 0.2 Chen zhaoying Add pre RA ‘s 2012-05-24 0.3 Chen zhaoying Add example msg Content Company Confidential * Part-1 Part-3 Random Access in LTE TDD QA Part-2 Pre Random Access Process Pre-Random Access * System InfoPRACH-Configuration in SIB2 The IE PRACH-ConfigurationSIB and IE PRACH-Configuration are used to specify the PRACH configuration in the system information and in the mobility control information, respectively. PRACH-Configuration information elements -- ASN1START PRACH-ConfigurationSIB ::= SEQUENCE { rootSequenceIndex INTEGER (0..837), prach-ConfigInfo PRACH-ConfigInfo } PRACH-ConfigInfo ::= SEQUENCE { prach-ConfigurationIndex INTEGER (0..63), highSpeedFlag BOOLEAN, zeroCorrelationZoneConfig INTEGER (0..15), prach-FrequencyOffset INTEGER (0..104) } -- ASN1STOP Random Access Process Preamble Transmission 在发送上行接入前导序列之前，终端应该已经和系统下行同步好了，下行同步意味着UE获得了帧同步以及系统广播消息，但是上行并没有同步。通过前导序列，让eNB知道存在一个终端试图跟基站建立连接； LTE中, 每个小区有64个随机接入的前导序列, 分别被用于基于竞争的随机接入 (如初始接入)和非竞争的随机接入(如切换时的接入).其中, 用于竞争的随机接入的前导序列的数目个数为numberofRA-Preambles,在SIB2系统消息中广播. ? 用于竞争的随机前导序列, 又被分为GroupA和GroupB两组.??其中GroupA的数目由参数preamblesGroupA来决定, 如果GroupA的数目和用于竞争的随机前导序列的总数的数目相等, 就意味着GroupB不存在. GroupA 和GroupB的主要区别在于将要在MSG3中传输的信息的大小, 由参数messageSizeGroupA 表示。在GroupB存在的情况下, 如果所要传输的信息的长度(加上MAC头部, MAC控制单元等)大于 messageSizeGroupA,并且UE能够满足发射功率的条件下, UE就会选择GroupB中的前导序列. Random Access Response 当eNB检测到UE发送的前导序列，就会在DL-SCH上发送一个响应，包含：检测到的前导序列的索引号、用于上行同步的时间调整信息、初始的上行资源分配(用于发送随后的MSG3), 以及一个临时C-RNTI