Handover Techniques In Heterogeneous Mobile Networks

Abstract

Handover means transferring an ongoing call or data sessions one cell to another. Handovers occur due to the movement of the mobile user from one area to another area. Handovers are used to prevent an ongoing call to be disconnected. If we don’t use handovers then whenever a user leaves the area of a particular cell then its ongoing call is immediately disconnected. The process of handovers requires a number of parameters e.g. what is the handover scheme we are using, how many channels are free. In the handover process we should also keep into consideration the required handover parameters as QoS, subscriber velocity, subscriber applications, target cell load, etc. There exists around hundred handover parameters that affect handover process; we can’t say certain combinations of parameters are the best choice. We have to choose the suitable parameters to our network model and operator requirements. Vertical handover refers to automatic switching the communication/data session from one technology to the other. So, it’s different from a horizontal handover among various wireless access points using the same technology. A suitably equipped device may be able to use both technologies at a time, the high speed Wireless LAN and cellular technology. In this thesis, a fuzzy based vertical handover is between LTE and WLAN is proposed. The technique uses the subscriber velocity, the target cell load, and the target cell RSS level as input parameters to the fuzzy logic system. The output is the handover decision, this is used to allow certain subscriber to make handover to certain cell or prevent him. MATLAB simulation is used to compare the performance of the proposed one with LTE hard handover technique. Another hysteresis based vertical handover is introduced. This algorithm uses the subscriber velocity, the subscriber balance, and the subscriber application to differentiate different subscribers. This algorithm gives the highest priority to the subscriber with high speed applications and high balance to make handover to the high speed resources hot spot.