Handover Configurations in Operational 5G Networks: Diversity, Evolution, and Impact on Performance

TL;DR

The paper tackles the problem of understanding how handover configurations in 5G operational networks shape performance under diverse bands and architectures. It adopts a large-scale, cross-country measurement approach, collecting tens of thousands of HO events across the three major US operators over 27 months. Key findings include the emergence of new 5G HO types, aggressive UE-side reporting that inflates signaling overhead, substantial diversity in HO parameter values (particularly for LTE, with 5G showing convergence over time), and complex, sometimes non-intuitive effects of HO configurations on RSRP and throughput. The work offers practical implications for operators to tune HO policies, balance responsiveness and overhead, and reduce unfavorable effects like ping-pong and downgrades, while providing an open dataset for broader research and validation.

Abstract

Mobility management in cellular networks, especially the handover (HO) process, plays a key role in providing seamless and ubiquitous Internet access. The wide-scale deployment of 5G and the resulting co-existence of 4G/5G in the past six years have significantly changed the landscape of all mobile network operators and made the HO process much more complex than before. While several recent works have studied the impact of HOs on user experience, why and how HOs occur and how HO configurations affect performance in 5G operational networks remains largely unknown. Through four cross-country driving trips across the US spread out over a 27-month period, we conduct an in-depth measurement study of HO configurations across all three major US operators. Our study reveals (a) new types of HOs and new HO events used by operators to handle these new types of HOs, (b) overly aggressive HO configurations that result in unnecessarily high signaling overhead, (c) large diversity in HO configuration parameter values, which also differ across operators, but significantly lower diversity in 5G compared to LTE, and (d) sub-optimal HO configurations/decisions leading to poor pre- or post-HO performance. Our findings have many implications for mobile operators, as they keep fine-tuning their 5G HO configurations.

Figures (26)

• Figure 1: Basic HO procedure.
• Figure 2: Example showing B1 report triggering an LTE-LTE HO.
• Figure 3: Example showing A1 report triggering an LTE-LTE HO.
• Figure 4: Example showing A2 report triggering an 5G-5G HO.
• Figure 5: 5G and LTE coverage.