LTE heterogeneous networks (HetNets) is becoming a popular topic since it\nwas first developed in 3GPP Release 10. HetNets has the advantage to assemble\nvarious cell networks and enhance users� Quality of Service (QoS) within\nthe system. However, its development is still constrained by two main issues:\n1) Load imbalance caused by different transmission powers for various tiers,\nand 2) The unbalanced transmission power may also increase unnecessary\nhandover rate. In order to solve the first issue, Cell range expansion (CRE)\ncan be applied in the system, which will benefit lower-tier cell during user association\nphase; CRE, Hysteresis Margin (HM) and Time-to-Trigger (TTT)\nwill be utilized to bound UE within lower tier network of HetNets and therefore\nsolve the second issue. On the other hand, the relationship of these parameters\nmay be complicated and even reduce QoS if they are chosen incorrectly.\nThis paper will evaluate the advantage and disadvantage of all three parameters\nand propose a Markov Chain Process (MCP) based method to find optimal\nHM, CRE and TTT values. And then, the simulation is taken and the\noptimal combination for our scenario is obtained to be 1 dB, 6 dB and 60 ms\nrespectively. First contribution of this paper is to map the HetNets handover\nprocess into MCP and all the phases of handover can be calculated and analysed\nin probability way, so that further prediction and simulation can be realised.\nSecond contribution is to establish a mathematical method to model the\nrelationship of HM, CRE and TTT in HetNets, therefore the coordination of\nthese three important parameters is achieved to obtain system optimization
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