Interference Management for Relay-Aided Cellular Network

Abstract

In this dissertation, three main contributions are given as i) relay-aided interference<br/> alignment (IA), ii) coded caching for cache-aided multiple-input multiple-output<br/> (MIMO) cellular network, and iii) inter-cell interference coordination (ICIC) based on<br/> cell zooming are considered.<br/> First, we propose an interference alignment scheme for the MIMO uplink cellular<br/> network with the help of a relay which operates in half-duplex mode. The proposed<br/> scheme only requires global channel state information (CSI) knowledge at the<br/> relay, with no transmitter beamforming and time extension at the user equipment (UE),<br/> which differ from conventional IA schemes for cellular networks. We derive the feasibility<br/> condition of the proposed scheme for the general cellular network configuration<br/> and analyze the degrees-of-freedom (DoF) performance of the proposed IA scheme<br/> while providing a closed-form beamformer design at the relay. Extensions of the proposed<br/> scheme to downlink and full-duplex cellular networks are also proposed. The<br/> DoF performance of the proposed schemes is compared to those of linear IA scheme<br/> and relay-aided interference management schemes for a cellular network with no time<br/> extension. It is also shown that advantages similar to those in the uplink case can be obtained<br/> for the downlink case through the duality of a relay-aided interfering multipleaccess<br/> channel (IMAC) and an interfering broadcast channel (IBC). Furthermore, the<br/> proposed scheme for a full-duplex cellular network is shown to have advantages identical<br/> to those of a number of proposed half-duplex cellular cases.<br/> Second, coded caching for cache-aided MIMO cellular network where each UE<br/> has cache with the help of full-duplex relay is proposed. The proposed scheme consists<br/> of inter-cell IA based on relay and coded multicasting based on base station (BS)<br/> beamforming. The normalized delivery time (NDT) performance analysis is given,<br/> where the achievable NDT of proposed scheme exploits multi-antenna gain on BSs and<br/> i<br/> UEs. Also, it has advantage of no decorrelator design at the UE side to receive multicast<br/> message. Closed-form of BS beamformer for coded caching is also described.<br/> Further, the description of proposed scheme when the relay is aware of demands of the<br/> cells is presented.<br/> Last, ICIC for self organizing cellular network is proposed, where each BS is not<br/> able to share information through backhaul to perform conventional ICIC schemes.<br/> Proposed ICIC scheme is based on distributed cell zooming, where non-cooperative<br/> game theory is used. Further, we show that proposed scheme can efficiently handle<br/> inter-cell interference and coverage hole problem in self organizing network by simulation<br/> result.