Improvement of Bi-directional Communications using Solar Powered Reconfigurable Intelligent Surfaces

Recently, there has been a flurry of research on the use of Reconfigurable Intelligent Surfaces (RIS) in wireless networks to create dynamic radio environments. In this paper, we investigate the use of an RIS panel to improve bi-directional communications. Assuming that the RIS will be located on the facade of a building, we propose to connect it to a solar panel that harvests energy to be used to power the RIS panel’s smart controller and reflecting elements. Therefore, we present a novel framework to optimally decide the transmit power of each user and the number of elements that will be used to reflect the signal of any two communicating pair in the system (user-user or base station-user). An optimization problem is formulated to jointly minimize a scalarized function of the energy of the communicating pair and the RIS panel and to find the optimal number of reflecting elements used by each user. Although the formulated problem is a mixed-integer nonlinear problem, the optimal solution is found by linearizing the non-linear constraints. Besides, a more efficient close to the optimal solution is found using Bender decomposition. Simulation results show that the proposed model is capable of delivering the minimum rate of each user even if line-of-sight communication is not achievable

Architecture and Protocols for Inter-cell Device-to-Device Communication in 5G Networks

The massive admiration of cellular devices has stimulated a flourishing growth of high data rate wireless services, which has sparked an insisting need for more efficient spectrum usage as well as reduced power consumption. This has given rise to Device-to-Device (D2D) communication, which offloads the relaying burden of the base station to direct links between the users. Recent studies have shown that D2D communication results in higher data rates, lower energy consumption and time delay. In this paper, the architecture and a set of protocols for enabling inter-cell D2D communication in 5G networks have been proposed. More specifically, device discovery and session setup protocols for different applications have been presented