Multicell D2D Communications for Hierarchical Control of Microgrid System

Abstract

In microgrid, hierarchical control requires an advanced communication network. In order to meet stringent communication latency requirement, we use cellular-assisted underlay device-to-device (D2D) communications to connect control devices directly to central controller. Compared to the literature, this scenario is unique because control devices and central controller are not located within a same cell. Thus, a D2D link may span across multiple cells, and a single D2D transmission may impose interference on multiple cellular transmissions in different cells. This article aims to guarantee a minimum throughput to each control unit over D2D link to satisfy its latency requirement, while maximizing the spectral efficiency, which is measured in term of sum-rate of all cellular users. A 2-tier resource allocation scheme has been proposed. Tier-1 assigns channels to static control units. Tier-2 operates more frequently in assigning channels to mobile cellular users and control transmit power for both cellular and D2D nodes. Tier-1 optimization has been solved using the Hungarian algorithm. Tier-2 optimization is originally a complex nonconvex problem, and has been transformed into a combination of convex optimization and linear assignment problem. The proposed scheme has been evaluated through extensive simulations, and comparisons with a benchmark scheme that assigns communication channels randomly. Results have confirmed the efficiency and superiority of the proposed scheme, as well as its ability in finding the smallest D2D transmit power necessary in fulfilling a given latency requirement.