One of the major challenges in the heterogeneous networks, where different base stations with different capabilities serve users, is the access policy for establishing a communication link between the user and its serving node. To overcome this challenge in a heterogeneous network which also suffers from the backhaul constraint, a special kind of “ decoupled uplink and downlink access” policy is proposed in this paper, which let users to be served by different base stations in uplink and downlink communications. More precisely, in order to efficiently utilize the system resources, increase the users’ throughput, and guarantee the users’ fairness, a special load balancing association policy is considered in the uplink transmission and a problem which maximizes the weighted sum of users’ effective rates is solved. Simulation results show that using this association policy for the considered scenario, significantly improves the load balancing index, energy efficiency, and also users’ effective rate compared to the scenario which considers the criterion of the maximum received power of the downlink connection for both uplink and downlink transmissions. In addition we propose an algorithm which further improves the load balancing considering the backhaul constraint of the base stations and evaluate its efficiency.

In this paper, a wireless mesh backhaul using MIMO systems has been studied. In the mesh networking, information is routed from source to destination over multiple wireless links. On the other hand, using wireless MIMO systems, the channel capacity is significantly increased without additional signal power or bandwidth. We have used the linear programming to optimize the routing determination to maximize the throughput. This technique is used to calculate the throughput for a hexagonal grid of base-stations, for single-hop, multi-hop, SISO, and MIMO transmissions for various network scenarios.

In this paper an uncertain multi objective closed-loop supply chain is developed. The first objective function is maximizing the total profit. The second objective function is minimizing the use of row materials. In the other word, the second objective function is maximizing the amount of remanufacturing and recycling. Genetic algorithm is used for optimization; and for finding the pareto optimal line, Epsilon-constraint method is used. Finally a numerical example is solved with proposed approach and performance of the model is evaluated in different sizes. The results show that this approach is effective and useful for managerial decisions.

Decoupling the uplink and downlink user association improves the throughput of heterogeneous networks (HetNets) and balances the traffic load of macro-and small-base stations. Recently, fiber-wireless HetNets (FiWi-HetNets) have been considered as viable solutions for access networks. To improve the accuracy of user association and resource allocation algorithms in FiWi-HetNets, the capacity limitation of various backhaul technologies must be considered. In this paper, we investigate the backhaul-aware decoupled uplink/downlink (UL/DL) user association, subcarrier allocation, and power control optimization problem in FiWi-HetNets. In our system model, fiber and millimeter wave (mmWave) links are used as backhaul of base stations, and the backhaul capacity limitation and minimum required transmission rate (R_min) are modeled in the optimization problem. As the formulated optimization problem is non-convex, we present a heuristic algorithm to divide the main problem into two sub-problems that are solved iteratively. The proposed algorithms are evaluated through exhaustive simulations. The results indicate that decoupling UL/DL user association improves the sum rate of FiWi-HetNets. Besides, we evaluate the effect of backhaul capacity limitation and R_min on the sum rate of FiWi-HetNets. The effect of upgrading fiber backhaul technology is also investigated to evaluate the role of fiber backhaul on the sum rate of the radio access network.

Constrain is the condition of driven by necessity. The principle of constraint determines the duties of the person constrained. In jurisprudence, it includes a range of activities from cleanness to blood compensation. However, jurisprudents have discussed it mainly with regard to those that can be eaten and drunk, and presented three different interpretations: fear of losing one"s life; fear in general, including fear of losing one"s life, or one"s limb, etc.; and fear of things not related to oneself but to others. The roots of constraint are compulsion, precautionary concealment, loss and necessity. The present article deals with a kind of constraint whose source is necessiy. The Qur"an has explicitly excused the person constrained from duties provided that the oppressor shows no inclination to sin. Tradition says that "there is so unlawful act that God Almighty has not made it permissible under constraint." The intellect also knows it permissible to give up necessary duties and to do the unlawful acts under constraint. Finally, the writer presents the conditions under which the application of the principle of constrain is made permissible.

This paper considers the vehicle routing problem with backhaul (VRPB) and some applicable constraints, in which a set of costumers are divided into two subsets of linehaul and backhaul costumers. Each linehaul costumer requires its demands to be delivered from the depot. In addition, a specified quantity of products should be picked up from the backhaul nodes to the depot. The main point in this study is that the customer demands, which are over than the maximum of available vehicles, can be divided to different customers. In addition, there is limited vehicle access availability for some costumers. The central depot includes a fleet of vehicles with different capacities, in which the number of vehicles of each type is not limited and customer demands are dynamic and can change in each period. This problem is a wellknown NP-hard one; therefore, a new multi-ant colony optimization algorithm is proposed to solve the given problem. This proposed algorithm contains two phases, namely clustering and routing. Finally, the numerical results of designed test problems have been discussed and analyzed.

The concept of design is associated with the notion of constraint as a limiting factor, and the search for the constraint in the design process is essential in design research. This study applies the ontological method to define the domain and scope of constraints, their classes and subclasses, and how to apply them. We concluded that there are two types of constraints in design: inside the designer’, s mind or internal constraint and outside it or external constraint. Each of these is classified into two subclasses: internal constraints can be divided into deduced and subject constraints, and external constraints are categorised into imposed and intrinsic constraints. In the end, we proposed a model that shows that designers can identify, choose, manage, and even generate constraints in the design process to facilitate the restructuring of the design problem, which helps them solve the design problem.