ANR IN LTE

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ANR 即自动邻区关系是LTE里面的一个非常重要的功能。这个功能使得RBS能够自动的更新和维护邻区关系列表。它能够实现自动添加外部邻区并自动建立X2接口使得UE能够正常切换。

我们都知道在现代蜂窝通信系统优化工作中最费时间的事情就是优化切换相关的问题，这个自动邻区关系的功能能够很大程度的降低人工配置邻区关系的工作量。并且能够减少邻区关系漏配而造成的掉话。

自动邻区关系实现的简要过程:如果我们现在有两个小区，cellA 和cellB .一个UE 在两个小区的切换点上向 cellA 报告了cellB 的 PCI值。但是cellA的邻区关系列表里面没有这个PCI的小区则此时它就会要求UE去读取cellB的CGI的值，cellA就会记住这个CGI和PCI值。如果在一定的时间范围内，有足够多的UE报告此cellB的PCI和CGI的值，那么cellA就会自动添加cellB为邻区，如果是在不同的enodeB上则会自动建立X2接口。
ANR is Automated Neighbor Relation which is a important feature in LTE system.This feature enables RBS to update and maintain the neighbor relation list automatically. And it also manage to let RBS to add external neighbor and set up x2 interface automatically which is useful to optimize the handover.
As you know the most consuming time work in morden cellular networks is the optimization of handover and other mobility functions.The Automated Neighbor relation feature manage to minimize the needs for mannual configuration of neighbor cell relations.And what’s more,it also helpful to reduce the drop rate caused by missing neighbor.
This is the work flow of automated neighbor relation: here are two cells:cellA and cellB.One UE in cell A report the cellB’s PCI to cellA for handover.But the cellB’s PCI is unknown to cellA, alternatively,cellB’s PCI not exsit in the neighbor list of CellA.In this situation,cellA will order UE to read cellB’s GCI .In a certain time of range,if there are sufficient number of UEs reporting cellB’s PCI and CGI,cellA will add cellB in its neighbor list.