Energy-aware resource allocation in next generation wireless networks : application in large-scale MIMO Systems

In this thesis, we investigate the resource allocation problem for wireless networks that incorporate large-scale multiple-input multiple-output (MIMO) systems. These systems are considered as key technologies for future 5G wireless networks and are based on using few hundreds of antennas simultaneously to serve tens of users in the same time-frequency resource. The gains obtained by large-scale MIMO systems cannot be fully exploited without adequate resource allocation strategies. Hence, the aim of this thesis is to develop energy-aware resource allocation solutions for large-scale MIMO systems that take into consideration network power cost. Firstly, this thesis investigates the downlink of a base station equipped with large-scale MIMO system while taking into account a non-negligible transmit circuit power consumption. This consumption involves that activating all RF chains does not always necessarily achieve the maximum sum-rate. Thus, we derive the optimal number of activated RF chains. In addition, efficient antenna selection, user scheduling and power allocation algorithms in term of instantaneous sum-rate are proposed and compared. Also, fairness is investigated by considering equal receive power among users. Secondly, this thesis investigates a large-scale MIMO system that incorporates energy harvesting that is a promising key technology for greening future wireless networks since it reduces network operation costs and carbon footprints. Hence, we consider distributed large-scale MIMO systems made up of a set of remote radio heads (RRHs), each of which is powered by both an independent energy harvesting source and the grid. The grid energy source allows to compensate for the randomness and intermittency of the harvested energy. Optimal on-line and off-line energy management strategies are developed. In addition, on-line energy management algorithm based on energy prediction is devised. The feasibility problem is addressed by proposing an efficient link removal algorithm and for better energy efficiency, RRH on/off operation is investigated. Thirdly, wireless backhauling was proposed as an alternative solution that enable low-cost connection between the small base stations and the macro base station in heterogeneous networks (HetNets). The coexistence of massive MIMO, HetNets and wireless backhauling is a promising research direction since massive MIMO is a suitable solution to enable wireless backhauling. Thus, we propose a new transmission technique that is able to efficiently manage the interference in heterogeneous networks with massive MIMO wireless backhaul. The optimal time splitting parameter and the allocated transmit power are derived. The proposed transmission technique is shown to be more efficient in terms of transmit power consumption than the conventional reverse time division duplex with bandwidth splitting. In this thesis, we developed efficient resource allocation solutions related to system power for wireless networks that incorporate large-scale MIMO systems under different assumptions and network architectures. The results in this thesis can be expanded by investigating the research problems given at the end of the dissertation

Smart FRP Composite Sandwich Bridge Decks in Cold Regions

INE/AUTC 12.0

Improving way of Logistics Management in Korean Army

The objective of this research is to find a way to improve Korean Army Logistics. This is accomplished through interviewing field experts and adopting their ideas to improve it. An interview with the manager of a successful civilian company and relevant literature also gave ideas in improvement. This research is written based on interviews with the logistic officers on different branches and different units in the Korean Army. Through interview with them, this research identified 4 main problems in the current logistics system: 1) multilevel supply support system, 2) inaccurate demand management system, 3) inefficiency of procurement and transportation management, 4) the short of professionalism of logistics officers. The solutions about the identified problems are acquired by an investigation of the relevant literature, telephone interviews with Army logistics personnel and an interview with a leading private enterprise manager. Four applicable improvements ways are presented: 1) construction of central inventory management system for shortening the customer wait time, 2) simplifying the supply chain by direct purchase by users and units, 3) reducing inventory cost and increase supply rate through applying the Prime Vendor system, 4) establishing an education system and ensuring an education environment. In addition to the above identified problems and solutions, Korea Army Logistic still has other unidentified problems. These things can be identified and improvements of those can be found in different kinds of units through analyzing their situations