A Markov-based Framework For Handover Process in Heterogenous Networks

Abstract

Due to the increase in demand of high data tra c, mobile networks are evolving from single overlay network to a complex mixture of network technologies referred as Heterogeneous networks (HetNets). Such networks require smooth transition of communication link when user moves from one cell to another cell region of HetNets, called handover (HO). There are several issues in handover process. Our aim is to analyze handover scenarios, key parameters of HO, success and failure of HO rate (HOR) which a ects the performance. HO occurs when signal to noise ratio is less than prede ned threshold. In this thesis we analyze the performance of handover under di erent parameters, such as received signal strength (RSS), hysteresis mar- gin (HM) and Cell Range Expansion (CRE). A Markov based framework is used to model the handover process for the user equipment (UE) by de ning di erent positions of the UE at a possible trajectory as the Markov states. With the change in UE, its SINR changes accordingly. This behavior is modelled in Markov chain by using transfer probabilities, where at a particular state the UE can stay in the same state or is in motion. A few transitions of the Markov chain from a given initial state can specify the HOR of the network. To analyze the e ect of the above param- eters on HOR, we consider a single macro cell and femto cell with a UE following a speci c trajectory towards the femto cell. Distances of UE along the trajectory from both macro and femto cell are computed that are used to nd distance depen- dent path losses. This allows us to compute received signal strength which in turn identi es the transfer probabilities of each state. Finally the performance of HOR is analyzed through transitions of the Markov chain. It is observed that there is a decrease in HOR as the values of CRE, HM and number of states increases. The main purpose of this work is to observe e cient handover criteria in heterogeneous cellular networks so that the overall quality of communication service improves.