The impact of mobility model on handover rate in heterogeneous multi-tier wireless networks

Heterogeneous multi-tier wireless networks deploy many small cells to overcome the scarcity of bandwidth for broadband wireless access. However, increasing the number of cells increases the rate of required handover as a mobile user passes through the boundaries of these cells leads to more signaling overhead. We address the impact of mobile users’ mobility model in the urban areas on the handover rate. We use two real data sets to model the mobility pattern of pedestrians and drivers, considering their different velocity, move length, and pause time distributions. We use Poisson Point Processes to model the spatial distribution of base stations and assume that the number of handovers is equal to the number of times the users’ trajectories cross the cell's boundaries. We derive the distribution function of the handover rate by using the distribution function of the velocity of users. Simulation results are provided to justify the deployed mobility model and the derived analytical results for the handover rate. We find that while the trend of the handover rate against the density of base stations and bias values at different tiers deploying the derived realistic mobility models and simple random waypoint model is the same, the total number of handovers in the network has different behavior. Interestingly, we found that if the number of users increases beyond a threshold, the handover rate decreases, suggesting that the hand over rate is bounded.