Διαδικασίες και αλγόριθμοι handover για συστήματα κινητής επικοινωνίας
In the current study the mechanism of switching between cells (handover) in mobile communication systems is presented and analyzed in detail. The handover methods are mainly applied in cellular systems and categorized according to various characteristics in hard or soft handovers, horizontal or vertical handovers, and handovers controlled by the network or the mobile device, or assisted by the mobile device. Handover decision algorithms play important role in the described processes. Main categories of handover decision algorithms are those based on the received signal strength, fuzzy logic and priority. In this study, a priority algorithm known as SJ-scheme is simulated, using Matlab software and, in particular subsystems Simulink and Stateflow. The proposed model consists of six major subsystems: Input Subsystem, Channels Size Subsystem, Memory Subsystem, Call Completion Subsystem, Scope Subsystem and Handover Subsystem which is the heart of the model and includes two main blocks, one that implements the new call management process and one that implements the procedure for managing handovers. Besides creating a simulation model, in this work results of running the simulation and measured data are presented and discussed. Matlab plots and graphical representations produced are examined to make clear the way that the proposed model works.