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Rapid signal fluctuations due to blockage effects cause excessive handovers (HOs) and degrade mobility performance. By reconfiguring line-of-sight (LoS) Links through passive reflections, intelligent reflective surface (IRS) has the potential to address this issue. Due to the lack of introducing blocking effects, existing HO analyses cannot capture excessive HOs or exploit enhancements via IRSs. This paper proposes an LoS state transition model enabling analysis of mobility enhancement achieved by IRS-reconfigured LoS links, where LoS link blocking and reconfiguration utilizing IRS during user movement are explicitly modeled as stochastic processes. Specifically, the condition for blocking LoS links is characterized as a set of possible blockage locations, the distribution of available IRSs is thinned by the criteria for reconfiguring LoS links. In addition, BSs potentially handed over are categorized by probabilities of LoS states to enable HO decision analysis. By projecting distinct gains of LoS states onto a uniform equivalent distance criterion, mobility enhanced by IRS is quantified through the compact expression of HO probability. Results show the probability of dropping into non-LoS decreases by 70% when deploying IRSs with the density of 93/km$^2$, and HOs decrease by 67% under the optimal IRS distributed deployment parameter., Comment: 13 pages, 11 figures, submitted to IEEE

Owning to the reflection gain and double path loss featured by intelligent reflecting surface (IRS) channels, handover (HO) locations become irregular and the signal strength fluctuates sharply with variations in IRS connections during HO, the risk of HO failures (HOFs) is exacerbated and thus HO parameters require reconfiguration. However, existing HO models only assume monotonic negative exponential path loss and cannot obtain sound HO parameters. This paper proposes a discrete-time model to explicitly track the HO process with variations in IRS connections, where IRS connections and HO process are discretized as finite states by measurement intervals, and transitions between states are modeled as stochastic processes. Specifically, to capture signal fluctuations during HO, IRS connection state-dependent distributions of the user-IRS distance are modified by the correlation between measurement intervals. In addition, states of the HO process are formed with Time-to-Trigger and HO margin whose transition probabilities are integrated concerning all IRS connection states. Trigger location distributions and probabilities of HO, HOF, and ping-pong (PP) are obtained by tracing user HO states. Results show IRSs mitigate PPs by 48% but exacerbate HOFs by 90% under regular parameters. Optimal parameters are mined ensuring probabilities of HOF and PP are both less than 0.1%., Comment: 13 pages, 12 figures, submitted to IEEE