在LTE网络产生切换时首先需要激活UE端丈量进程，UE端用户可采取以下方法实现：
1 直接通过eNB的RRC实体实现（也是本文介绍）
2 通过已有切换算法配置丈量
3 开发新的切换算法并对其配置
首先需要研究丈量的内容是甚么，NS3通过LteRrcSap::ReportConfigEutra说明：
struct ThresholdEutra
{
enum
{
THRESHOLD_RSRP, ///< RSRP is used for the threshold.
THRESHOLD_RSRQ ///< RSRQ is used for the threshold.
} choice;
uint8_t range; ///< Value range used in RSRP/RSRQ threshold.
};
struct ReportConfigEutra
{
enum
{
EVENT,
PERIODICAL
} triggerType;
enum
{
EVENT_A1, ///< Event A1: Serving becomes better than absolute threshold.
EVENT_A2, ///< Event A2: Serving becomes worse than absolute threshold.
EVENT_A3, ///< Event A3: Neighbour becomes amount of offset better than PCell.
EVENT_A4, ///< Event A4: Neighbour becomes better than absolute threshold.
EVENT_A5 ///< Event A5: PCell becomes worse than absolute `threshold1` AND Neighbour becomes better than another absolute `threshold2`.
} eventId; ///< Choice of E-UTRA event triggered reporting criteria.
ThresholdEutra threshold1; ///< Threshold for event A1, A2, A4, and A5.
ThresholdEutra threshold2; ///< Threshold for event A5.
/// Indicates whether or not the UE shall initiate the measurement reporting procedure when the leaving condition is met for a cell in `cellsTriggeredList`, as specified in 5.5.4.1 of 3GPP TS 36.331.
bool reportOnLeave;
/// Offset value for Event A3. An integer between ⑶0 and 30. The actual value is (value * 0.5) dB.
int8_t a3Offset;
/// Parameter used within the entry and leave condition of an event triggered reporting condition. The actual value is (value * 0.5) dB.
uint8_t hysteresis;
/// Time during which specific criteria for the event needs to be met in order to trigger a measurement report.
uint16_t timeToTrigger;
enum
{
REPORT_STRONGEST_CELLS,
REPORT_CGI
} purpose;
enum
{
RSRP, ///< Reference Signal Received Power
RSRQ ///< Reference Signal Received Quality
} triggerQuantity; ///< The quantities used to evaluate the triggering condition for the event, see 3GPP TS 36.214.
enum
{
SAME_AS_TRIGGER_QUANTITY,
BOTH ///< Both the RSRP and RSRQ quantities are to be included in the measurement report.
} reportQuantity; ///< The quantities to be included in the measurement report, always assumed to be BOTH.
/// Maximum number of cells, excluding the serving cell, to be included in the measurement report.
uint8_t maxReportCells;
enum
{
MS120,
MS240,
MS480,
MS640,
MS1024,
MS2048,
MS5120,
MS10240,
MIN1,
MIN6,
MIN12,
MIN30,
MIN60,
SPARE3,
SPARE2,
SPARE1
} reportInterval; ///< Indicates the interval between periodical reports.
/// Number of measurement reports applicable, always assumed to be infinite.
uint8_t reportAmount;
ReportConfigEutra ();
}; // end of struct ReportConfigEutra
其中结构体ThresholdEutra根据3GPP标准文件定义了基于RSRP和RSRQ下的阈值及对应阈值的范围。
ReportConfigEutra结构体定义了：
1 触发丈量报告的类型 2 事件等级 3 不同等级事件下阈值 4是不是初始化丈量报告进程 5 A3事件偏移值 6 进入或离开事件触发状态时所用参数
7 触发时间 8 目的 9 用于评价触发状态的触发量 10 报告量 11 最大报告的小区数目 12 周期报告的报告间隔 13 丈量报告数目
将ReportConfigEutra结构体作为函数LteEnbRrc::AddUeMeasReportConfig的参数，见src/lte/model/lte-enb-rrc.cc便可。
举例：
LteRrcSap::ReportConfigEutra config;
config.eventid=LteRrcSap::ReportConfigEutra::EVENT_A1;
config.threshold1.choice=LteRrcSap::ReportConfigEutra::THRESHOLD_RARP;
config.threshold1.range=41;
config.triggerQuantity=LteRrcSap::ReportConfigEutra::RSRP;
config.reportInterval=LteRrcSap::ReportConfigEutra::MS480;
//配置对象初始化
std::vector<uint8_t> measIdList;
NetDeviceContainer::Iterator it;
for(it=devs.Begin();it!=devs.End();it++)
{Ptr<NetDevice> dev=*it;
Ptr<LteEnbNetDevice>endDev=dev->GetObject<LteEnbNetDevice>();
Ptr<LteEnbRrc>enbRrc=enbDev->GetRrc();
uint8_t measId=enbRrc->AddUeMeasReportConfig(config);//调用
measIdList.push_back(measId);//存储已有的measId
rnbRrc->TraceConnect("RecvMeasurementReport",
"context",
MakeCallback("&RecvMeasurementReportCallback"));//
}