Cellular networks rely on handovers (HOs) as a fundamental element to enable seamless connectivity for mobile users. A comprehensive analysis of HOs can be achieved through data from Mobile Network Operators (MNOs); however, the vast majority of studies employ data from measurement campaigns within confined areas and with limited end-user devices, thereby providing only a partial view of HOs. This paper presents the first countrywide analysis of HO performance, from the perspective of a top-tier MNO in a European country. We collect traffic from approximately 40M users for 4 weeks and study the impact of the radio access technologies (RATs), device types, and manufacturers on HOs across the country. We characterize the geo-temporal dynamics of horizontal (intra-RAT) and vertical (inter-RATs) HOs, at the district level and at millisecond granularity, and leverage open datasets from the country's official census office to associate our findings with the population. We further delve into the frequency, duration, and causes of HO failures, and model them using statistical tools. Our study offers unique insights into mobility management, highlighting the heterogeneity of the network and devices, and their effect on HOs.

翻译：蜂窝网络依赖切换作为保障移动用户无缝连接的基础要素。通过移动网络运营商的数据可以实现对切换的全面分析；然而，绝大多数研究采用的数据来自有限区域的测量活动且终端用户设备数量有限，因而仅能提供切换的局部视角。本文首次从欧洲某国顶级移动网络运营商的视角，提出了全国范围的切换性能分析。我们收集了约4000万用户连续四周的流量数据，研究了全国范围内无线接入技术、设备类型和制造商对切换的影响。我们以区域为粒度、毫秒级精度刻画了水平切换和垂直切换的时空动态特征，并利用该国官方人口普查机构的开放数据集将研究发现与人口分布相关联。我们进一步深入分析了切换失败的频率、持续时间和成因，并采用统计工具对其进行建模。本研究为移动性管理提供了独特见解，揭示了网络与设备的异构性及其对切换的影响。