Research on sojourn-time-based dynamic load balancing algorithm in heterogeneous hierarchical wireless networks

In order to serve much more mobile stations in heterogeneous hierarchical wireless networks, a dynamic load balancing algorithm based on sojourn time was proposed. Firstly, based on user mobile model, the sojourn time of each mobile station in cells was calculated, then the number of transferred ongoing calls per load balancing period was counted according to the new calls arrival rate of overloaded cell and the workload states of overlapping cells. Finally, those ongoing calls with longer sojourn time than the threshold were switched from overloaded cells to overlapping heterogeneous under-loaded cells, which could balance the system workload. In addition, in order to decrease the handoff call dropping probability, the vertical handoff schemes between different wireless networks were improved. Simulation results show that the proposed dynamic load balancing algorithm performs much better than existing algorithms with respect to the blocking probability, dropping probability and etc.