developing a new bi-objective functions model for a hierarchical location-allocation problem using the queuing theory and mathematical programming

In this research, a hierarchical location-allocation problem is modeled in a queue framework. the queue model is considered as m/m/1/k, in which system capacity is finite, equals to k. this is the main contribution of the current research. customer's enters to the system in order to find the service according to a poisson. in this problem, the hierarchical location-allocation model is considered in two levels. also, the model has two objective functions: maximizing the total number of demand coverage and minimizing the waiting time of customers in queues to receive services. after modeling and verifying the validity of the presented model, it is solved using nsga ii and mopso metaheuristics.