Sharif Digital Repository

Node cooperation approaches improve physical layer security in wireless networks without applying data encryption. Selecting the appropriate nodes to cooperate as relays or friendly jammers, to degrade eavesdropper's link, is a challenging problem which has attracted a lot of attention in recent years. Various approaches, based on conventional exhaustive search, have been suggested for optimal relay-jammer selection and power allocation in the literature. The complexity of these methods is proportional to the number of intermediate nodes. As the number of intermediate nodes exceeds a specific bound, conventional exhaustive search appears infeasible due to high computational complexity. In... 

The practicality of robust model predictive control of systems with model uncertainties depends on the time consumed for solving a defined optimization problem. This paper presents a method for the computational complexity reduction in a robust model predictive control. First a scaled state vector is defined such that the objective function contours in the defined optimization problem become vertical or horizontal ellipses or circles, and then the control input is determined at each sampling time as a state feedback that minimizes the infinite horizon objective function by solving some linear matrix inequalities. The simulation results show that the number of iterations to solve the problem...