To enhance the handover performance in fifth generation (5G) cellular systems, conditional handover (CHO) has been evolved as a promising solution. Unlike A3 based handover where handover execution is certain after receiving handover command from the serving access network, in CHO, handover execution is conditional on the RSRP measurements from both current and target access networks, as well as on mobility parameters such as preparation and execution offsets. Analytic evaluation of conditional handover performance is unprecedented in literature. In this work, handover performance of CHO has been carried out in terms of handover latency, handover packet loss and handover failure probability. A Markov model accounting the effect of different mobility parameters (e.g., execution offset, preparation offset, time-to-preparation and time-to-execution), UE velocity and channel fading characteristics; has been proposed to characterize handover failure. Results obtained from the analytic model has been validated against extensive simulation results. Our study reveal that optimal configuration of $O_{exec}$, $O_{prep}$, $T_{exec}$ and $T_{prep}$ is actually conditional on underlying UE velocity and fading characteristics. This study will be helpful for the mobile operators to choose appropriate thresholds of the mobility parameters under different channel condition and UE velocities.

翻译：为提升第五代(5G)蜂窝系统的切换性能，条件切换(CHO)已成为一种有前景的解决方案。与基于A3的切换（即从服务接入网收到切换命令后立即执行切换）不同，CHO的切换执行取决于当前和目标接入网的RSRP测量值，以及准备偏移量、执行偏移量等移动性参数。文献中尚未出现对条件切换性能的分析评估。本研究从切换时延、切换丢包率和切换失败概率三个方面对CHO的切换性能进行了评估。考虑不同移动性参数（如执行偏移量、准备偏移量、准备时间与执行时间）、用户终端速度和信道衰落特性的影响，提出了用于表征切换失败的马尔可夫模型。通过大量仿真结果验证了分析模型的正确性。研究表明，$O_{exec}$、$O_{prep}$、$T_{exec}$和$T_{prep}$的最优配置实际上取决于底层用户终端速度和衰落特性。本研究将有助于移动运营商在不同信道条件和用户终端速度下选择适当的移动性参数阈值。