Decision-making Methods Based On Uncertain Linguistic Expressions And Their Applications In Communication System Evaluation

In today's era of big data,the complexity and uncertainty of information are increasing day by day.Faced with these challenges,decision-making methods are constantly changing and developing.When decision makers(DMs)solving decision-making problems,obtaining real and comprehensive evaluation information is of great significance to the final evaluation results.As a form of qualitative decision-making information,uncertain linguistic expressions can express the real opinions flexibly and appropriately in real decision-making problems.Studying decision-making methods based on uncertain linguistic expressions can not only improve the accuracy of information description,enrich the values of linguistic variables,but also enhance the reliability and interpretability of decision-making results.The research work of this thesis will conduct in-depth research on decision-making methods based on uncertain linguistic expressions from the theoretical and application perspectives.The details are as follows:(1)This thesis proposes the concept of uncertain probabilistic linguistic term set(UPLTS),studies its basic theory and group decision-making methods.During the decision-making process,DMs may not be able to give the complete assessments due to lack of knowledge or experience.In the probabilistic linguistic term set(PLTS),the lack of evaluation information may cause the sum of the probabilities of all linguistic terms to be less than 1,which is called ignorance.To solve the ignorance problem that affects the accuracy of results,this thesis firstly proposes the concept of UPLTS to serve as an extension of the existing tools.This linguistic representation model expresses the uncertainty of information in the form of interval,and extends the PLTS into a more generalized model.Then,some basic operational laws,comparison rules and aggregation operators are presented for UPLTSs.According to the properties of UPLTSs,this thesis proposes two kinds of group decision-making methods,one based on the aggregation function and the other based on the improved TOPSIS method.Aiming at the former,this thesis defines several new aggregation operators.For the latter,the optimal solution is selected by calculating the distance between the solution to be evaluated and the positive and negative ideal solutions.The closer the distance to the positive ideal solution and the farther the distance to the negative ideal solution,the better the solution.Finally,the decision-making method based on UPLTSs is applied to communication device evaluation.(2)This thesis proposes a new method called uncertain probabilistic linguistic analytic hierarchy process(UPL-AHP),which combines traditional analytic hierarchy process(AHP)with UPLTSs to process decision information in complex problems.Firstly,we propose the concept of uncertain probabilistic linguistic comparison matrices(UPLCM).Then,a new approach is given to check and improve the consistency of UPLCMs.When improving the consistency of UPLCMs,our method maintains the original linguistic terms given by the experts and improves the consistency of UPLCMs by modifying their probabilities.In addition,this thesis also proposes a new aggregation method of UPLCMs,and determines the priority of them according to the probability degrees of uncertain linguistic term sets.Finally,the UPLAHP is used to analyze the performance of the UV-light communication systems in haze weather.(3)This thesis proposes a new linguistic expression model called uncertain linguistic term with weakened hedge(ULTWH),which expresses decision information better and closer to the original terms of DMs.An ULTWH is consisted of a linguistic term interval where the real value of a linguistic variable is most likely to appear,and a weakened hedge which is used to express the degree of uncertainty.The order relations,operation rules and the aggregation operators for ULTWHs are formulated and presented in the paper.Linguistic hedges,which serve as a tool for multi-granular decision making express uncertainty in a qualitatively way.A ULTWH can be regarded as a term in a relatively coarse granularity domain,so it has a natural advantage in representing multi-granular linguistic information.In the unification phase of most traditional methods,it is necessary to define a basic linguistic term set(BLTS)which is uniformly distributed in the domain,and all linguistic assessments can be unified based on this BLTS.But in the proposed method,when processing multi-granularity information,there is no need to additionally introduce a virtual uniformly distributed linguistic term set with sufficiently fine granularity.In the process of unification,the result of conversion is always maintained as a natural linguistic expression.The result of each stage can be interpreted as an uncertain linguistic expression close to experts' expression habits.Finally,a case evaluating the applicability of communication technologies in the urban village is made.(4)In terms of application,the above theories are used to evaluate the comprehensive performance of the wireless communication systems.Firstly,a general performance evaluation index system is established according to the attributes of wireless communication systems,and then the index weights are calculated using the UPLTS and the UPL-AHP.Then,ULTWHs are used to express the evaluation values of experts,and finally the solution ranking is obtained.This method of combining quantitative analysis and qualitative analysis provides a theoretical basis for the selection and research of communication systems.In general,this thesis proposes two types of uncertain linguistic expressions based on decision-making problems in uncertain environments,which expands the value of linguistic variables and provides more possibilities for DMs to express assessments.At the same time,different group decision-making methods are proposed according to the characteristics of different computing models,which enriches the existing decision-making theory system.In terms of application,the performance evaluation of wireless communication systems is studied,and the feasibility and effectiveness of the proposed method are verified by means of simulation experiments.In theory,the research results of this thesis provides an effective way for solving decision-making problems with complex linguistic information;in application,the linguistic decision-making method combining qualitative and quantitative is used for communication system evaluation,which is innovative and has broad application prospects.