چكيده به لاتين
Task Off-Loading is a solution to compensate for resource constraints on the Internet of Things. Deciding on The place of offloading is very important. In this dissertation, a three-tier (Internet of Things-Fog-Cloud) architecture for the Internet of Things is presented and the benefits of Cloud and Fog layers, which act as complements, are used to offload. Fog is a more suitable place for offloading than Clouds in terms of energy consumption and response time, and the purpose of this work is to optimize these criteria in Fog. For this purpose, the Fog layer is modeled by queue theory and based on the predefined availability for the Fog, the minimum number of servers required for this layer is determined by a binary search algorithm. Using the iteration policy algorithm of reinforcement learning, servers selected that have the lowest possible cost in addition to meeting the system requirements. To evaluate the proposed model, a large number of different scenarios were considered to calculate the cost of Fog. The results of the analytical solution of the proposed model show that increasing factors such as task arrival rate, server setup delay rate and buffer size increase the cost of Fog, and increasing factors such as the number of servers in the Fog, service rate and availability reduce the cost of Fog; and the higher the rejection probability of tasks in the Fog layer, the greater the cost of offloading which is closer to the cost of the Cloud. The proposed policy for sending tasks to heterogeneous servers performs better than Slovest Server Firsr, Fastest Server First and Randomly Chosen Server dispatch policies and has been able to reduce costs by 31%. The simulation results show that the proposed method for Task Off-Loading performs much better than when all Fog servers are on. The similarity of the simulation results with the results of the analytical solution indicates the validity of the model and the results obtained. The proposed method is suitable for Fog systems where the needs of IoT users for offloading are variable.
