Research On Dynamic Cell Selection Scheme For Terminals Moving In Heterogeneous Networks

There are many problems such as imbalance between uplink and downlink coverage as well as uplink interference from macrocell terminals to a small cell base station in the traditional cell selection scheme.Cell Range Expansion(CRE)and Almost Blank Subframe(ABS)are considered as effective techniques for solving related issues,but their performance has not been extensively verified.This dissertation focuses on uplink CRE scheme and downlink ABS-based CRE scheme,and we find that the CRE technique could distinctly improve uplink performance.Nevetheless,downlink performance may be severely impacted if the downlink of a picocell is identically expanded as its uplink.To solve this problem,this dissertation studies the ABS-based CRE scheme for downlink and finds that the joint optimization of CRE and ABS could effectively improve the downlink performance,and also finds that Max-Min fairness can be obtained by appropriate settings on CRE bias and ABS ratio.In a heterogeneous cell selection game,all the terminals want to maximize their own benefits,leading to a Nash equilibrium(NE)of the entire system with a relatively high performance.However,in a dynamic network scenario,terminals continuously move,making traditional methods unable to quickly reapproach the new NE when the previous NE does not hold due to the movements of terminals.Therefore,a dynamic cell selection method quickly reapproaching the new NE is proposed.With designed empirical formulas,terminals' cell selection strategies can be quickly adjusted so that the entire system always approaches NE.In addition,there is a problem that some terminals adopt strategies causing interference to the surrounding terminals severely for a slight increase in their own performance in a heterogeneous cellular network.Therefore,this dissertation tries to change terminals' cell selection strategies by adjusting prices.The simulation results show that the scheme can make more terminals get access to the picocell base station,thus alleviating uplink interference from macrocell terminals to picocell base station and reducing load pressure of the macrocell base station,and improve the performance of the entire system by designing a appropriate weight value of price utility function.