Relay Assisted Device to Device Communication Underlaying Cellular Networks

Abstract

Device-to-Device (D2D) communication underlaying cellular networks is a latest technology of advanced wireless communication which allows two nearby devices to communicate without assistance of Base Station (BS) in cellular network. Device-to-Device (D2D) communication improves Spectral Eciency , Energy Eciency ,link reliability and overall system throughput by permitting nearby devices to communicate directly in licensed spectrum.In this thesis , two device discovery protocols are presented ,one reactive protocol and other proactive protocol which helps in discovering the D2D pairs which intend to communicate with each other.In addition, we propose a mode selection algorithm that decides the mode in which the devices can communicate either through traditional cellular mode or D2D mode. This optimum mode selection maximizes the overall throughput. The benets of D2D communication are limited practically when the distance between D2D users is long and poor channel environment between the D2D users. To overcome these drawbacks, a relay-assisted D2D communication is introduced where additional relay mode is proposed along with existing modes (i.e) cellular mode and D2D mode. A joint mode and relay selection scheme based on Hungarian algorithm is proposed to improve the overall system throughput. The Hungarian algorithm proposed, selects a suitable communication mode for each transmission and also select the relay device that acts as a relay between transmitting user and receiving user for relay mode communication.D2D devices sharing the same spectrum with cellular users results in interference, which requires to be managed in the resource allocation algorithm. A graph theory based resource allocation method for D2D users is proposed to improve the overall system capacity and extend the network coverage area.