LTE切换事件

LTE切换时需要UE上报测量的结果（包括RSRP，RSRQ等），而上报又分为周期性上报和事件触发的上报。

周期性上报由基站配置，UE直接上报测量的结果。

事件触发的上报又分为同频系统的事件和不同系统间的事件： 同频切换报告事件包括：

1. 事件A1，服务小区好于绝对门限；这个事件可以用来关闭某些小区间的测量。

2. 事件A2，服务小区差于绝对门限；这个事件可以用来开启某些小区间的测量，因为这个 事件发生后可能发生切换等操作。 3. 事件A3，邻居小区好于服务小区；这个事件发生可以用来决定UE是否切换到邻居小区。 4. 事件A4，邻居小区好于绝对门限；

5. 事件A5，服务小区差于一个绝对门限并且邻居小区好于一个绝对门限；这个事件也可以用来支持切换

Intra-Frequency-HO切换都是基于A3/A5事件进行的切换

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A3事件：邻区的服务质量（RSRP/RSRQ）比服务小区高一个绝对门限，触发A3事件切换。 A5事件：服务小区的服务质量低于一个绝对门限1，邻区的服务质量高于一个绝对门限2，触发A5事件切换。

1.A3或A5事件触发。

2.Source eNB 向UE发送mearsurement control MSG

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3.Source eNB 向UE发送UL allocation（配给） MSG 4.UE向Source eNB发送Measurement report MSG 5.Source eNB内部进行HO decision（决策）

6.Source eNB向Target eNB发送Handover request（需求） MSG 7.Target eNB内部进行Admission（允许进去，承认） control9.Source eNB向UE回复DL allocation MSG

10.Source eNB向UE发送RRC Connection reconfiguration（重新配置） MSG11.UE与Source eNB进行Detach（分离），并开始同步到Target eNB

12.Source eNB进行缓存控制并向Target eNB传送数据包以及进行SN status transfer（序列数转移） 13.Source eNB向Target eNB进行数据转移传送14.UE与Target eNB同步完成

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8.Target eNB向Source eNB回复Handover request ack（承认） MSG

15.Target eNB向UE发送UL Allocation+TA UE MSG

16.UE向Target eNB发送RRC connection complete（完成） MSG 17.UE与Target eNB，Target eNB与S-GW之间进行数据交互

;Q:u5O&m)F1h18.Target eNB向MME发起Path switch request（路径切换请求） 19.MME向S-GW发起（用户面更新请求）user plane update request20.S-GW与Source eNB进行Switch DL Path（开关DL路径

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），并发起End marker（标示） MSG

21.Source eNB收到End marker MSG后向Target eNB发送End marker MSG 22.S-GW向MME发起Path switch request response（回复） MSG

23.MME收到来之S-GW的响应消息后向Target eNB发送Path switch request Ack MSG24.Target eNB向Source eNB发送UE context Release（上下文释放） MSG 25.Source eNB释放资源。

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从上面25个步骤，可以看到在发生切换时源eNB发送了哪些具体哪些参数和相关信息到目标eNB，

而我们在测试时在layer3看到的消息就只有三条：就是4,10,16

3gpp 36.331 5.5.4.2

A1: Serving becomes better than threshold

Inequality A1-1 (Entering condition)

Ms?Hys?Thresh

Inequality A1-2 (Leaving condition)

Ms?Hys?Thresh

A2: Serving becomes worse than threshold

Inequality A2-1 (Entering condition)

Ms?Hys?Thresh

Inequality A2-2 (Leaving condition)

Ms?Hys?Thresh

Ms is the measurement result of the serving cell, not taking into account any offsets.

Hys is the hysteresis parameter for this event (i.e. hysteresis as defined within reportConfigEUTRA for this event).

Thresh is the threshold parameter for this event (i.e. a1-Threshold as defined within reportConfigEUTRA for this event).

Ms is expressed in dBm in case of RSRP, or in dB in case of RSRQ. Hys is expressed in dB.

Thresh is expressed in the same unit as Ms.

A3: Neighbour becomes offset better than PCell

Inequality A3-1 (Entering condition)

Mn?Ofn?Ocn?Hys?Mp?Ofp?Ocp?Off

Inequality A3-2 (Leaving condition)

Mn?Ofn?Ocn?Hys?Mp?Ofp?Ocp?Off

The variables in the formula are defined as follows:

Mn is the measurement result of the neighbouring cell, not taking into account any offsets.

Ofn is the frequency specific offset of the frequency of the neighbour cell (i.e. offsetFreq as defined within measObjectEUTRA corresponding to the frequency of the neighbour cell). Ocn is the cell specific offset of the neighbour cell (i.e. cellIndividualOffset as defined within measObjectEUTRA corresponding to the frequency of the neighbour cell), and set to zero if not configured for the neighbour cell.

Mp is the measurement result of the PCell, not taking into account any offsets.

Ofp is the frequency specific offset of the primary frequency (i.e. offsetFreq as defined within measObjectEUTRA corresponding to the primary frequency).

Ocp is the cell specific offset of the PCell (i.e. cellIndividualOffset as defined within

measObjectEUTRA corresponding to the primary frequency), and is set to zero if not configured for the PCell.

Hys is the hysteresis parameter for this event (i.e. hysteresis as defined within reportConfigEUTRA for this event).

Off is the offset parameter for this event (i.e. a3-Offset as defined within reportConfigEUTRA for this event).

Mn, Mp are expressed in dBm in case of RSRP, or in dB in case of RSRQ. Ofn, Ocn, Ofp, Ocp, Hys, Off are expressed in dB.

A4: Neighbour becomes better than threshold

Inequality A4-1 (Entering condition)

Mn?Ofn?Ocn?Hys?Thresh

Inequality A4-2 (Leaving condition)

Mn?Ofn?Ocn?Hys?Thresh

A5: PCell becomes worse than threshold1 and neighbour becomes better than threshold2

Inequality A5-1 (Entering condition 1)

Mp?Hys?Thresh1

Inequality A5-2 (Entering condition 2)

Mn?Ofn?Ocn?Hys?Thresh2

Inequality A5-3 (Leaving condition 1)

Mp?Hys?Thresh1

Inequality A5-4 (Leaving condition 2)

Mn?Ofn?Ocn?Hys?Thresh2

A6: Neighbour becomes offset better than SCell

1> for this measurement, consider the (secondary) cell that is configured on the frequency indicated in the associated measObjectEUTRA to be the serving cell;

Inequality A6-1 (Entering condition)

Mn?Ocn?Hys?Ms?Ocs?Off

Inequality A6-2 (Leaving condition)

Mn?Ocn?Hys?Ms?Ocs?Off

B1: Inter RAT neighbour becomes better than threshold

1> for UTRA and CDMA2000, only trigger the event for cells included in the corresponding measurement object;

Inequality B1-1 (Entering condition)

Mn?Ofn?Hys?Thresh

Inequality B1-2 (Leaving condition)

Mn?Ofn?Hys?Thresh

The variables in the formula are defined as follows:

Mn is the measurement result of the inter-RAT neighbour cell, not taking into account any offsets. For CDMA 2000 measurement result, pilotStrength is divided by -2.

Ofn is the frequency specific offset of the frequency of the inter-RAT neighbour cell (i.e. offsetFreq as defined within the measObject corresponding to the frequency of the neighbour inter-RAT cell).

Hys is the hysteresis parameter for this event (i.e. hysteresis as defined within reportConfigInterRAT for this event).

Thresh is the threshold parameter for this event (i.e. b1-Threshold as defined within reportConfigInterRAT for this event). For CDMA2000, b1-Threshold is divided by -2. Mn is expressed in dBm or in dB, depending on the measurement quantity of the inter-RAT neighbour cell.

Ofn, Hys are expressed in dB.

Thresh is expressed in the same unit as Mn.

B2: PCell becomes worse than threshold1 and inter RAT neighbour becomes better than threshold2

Inequality B2-1 (Entering condition 1)

Mp?Hys?Thresh1

Inequality B2-2 (Entering condition 2)

Mn?Ofn?Hys?Thresh2

Inequality B2-3 (Leaving condition 1)

Mp?Hys?Thresh1

Inequality B2-4 (Leaving condition 2)

Mn?Ofn?Hys?Thresh2

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