## 3 Preliminaries  
### Data Description  
In this study, we chose relevant data for the operation and maintenance of the Shuo Huang Railway LTE-R network to construct a dataset for detecting cells with degraded communication performance. There are two main sources of Shuo Huang Railway operation and maintenance data: drive test data and abnormal release data from the E-RAB for each wireless communication service exported from the LTE-R Operation and Maintenance Center (OMC). Drive tests are the most commonly used methods for measuring the wireless network communication status along the Shuo Huang Railway. They are usually carried out by operation and maintenance personnel, who use measurement equipment to collect wireless communication performance indicator data from the user equipment (UE) side along the Shuo Huang Railway. At present, the OMC used in the Shuo Huang Railway LTE-R system is the Huawei u2000 (Huawei, Shenzhen, China),which can record historical key performance indicator data from the LTE-R system, thereby achieving unified management and maintenance of the network element layer and the network layer of the LTE-R network [32]. Figure 1 shows the source of Shuo Huang Railway operation and maintenance data. Drive test data contain a lot of information, including the reference signal receiving power (RSRP), reference signal receiving quality (RSRQ), signal-to-interference-plus-noise ratio (SINR), geographic location information, physical-layer cell identity (PCI), etc. Among these metrics, RSRP and SINR measure the communication status of LTE-R cells from the perspectives of signal strength and noise, respectively, while RSRQ is an important indicator for cell handover and reselection. Therefore, we selected RSRP, RSRQ, and SINR as the metrics for judging whether communication performance deterioration occurs in LTE-R cells. Furthermore, PCI was selected to categorize drive test data according to the LTE-R cells they belong to. Using data exported from the OMC system, many statistical values related to LTE-R communication performance can be obtained, such as throughput, latency, dropout rate, etc. In this paper, we focused on the E-RAB abnormal release rate. The successful establishment of an E-RAB shows that eNodeB has allocated wireless resources and radio bearers to the UE. Therefore, the E-RAB abnormal release rate represents the ability of eNodeB or a cell to carry services and can be used to evaluate the operational status of eNodeB or cells [2]. In the Shuo Huang Railway LTE-R system, the E-RAB abnormal release rate is calculated separately, according to the different wireless communication service types. The different types of wireless communication services on the Shuo Huang Railway are assigned a quality-of-service (QoS) class identifier (QCI) value, ranging from 1 to 7. The different QCI values and their corresponding communication services for the Shuo Huang Railway LTE-R system are shown in Table 1.  
From Table 1, it can be seen that communication services with a QCI of 1 have the highest QoS priority. The higher the QoS priority, the more important the communication service and the more resources it can obtain from wireless communication resource allocation. Therefore, we chose to use the E-RAB abnormal release rate (EARR) of communication services with a QCI of 1 as the only indicator to evaluate whether cells had experienced communication performance degradation. If the E-RAB abnormal release rate was greater than a certain threshold, the corresponding cell was considered to have degraded communication performance. Figure 1: The source of Shuo Huang Railway operation and maintenance data. In this paper, the drive test data of each LTE-R cell are taken as feature values and the linear interpolation method is used to interpolate the drive test data into sequences of the same length.