| Recently, with the rapid development of the wireless communication technology, the mobile networks make people convenient, and change people's way of life and work and all aspects of economic and social. However, with the popularization of the internet of things and internet of vehicles and the sharply increase of the demand for the high-speed data service, the requirement of the transmission rates and delay for wireless communication networks becomes more and more strict. To cope with the higher transmission rates and lower delay, the energy consumption of the mobile networks becomes more and more, and the scarcity of the spectrum becomes more and more serious.In fact, the greenhouse gas (GHG) emission caused by the information communications technology (ICT) accounts for more than 2 percent of the total industrial GHG emission.The huge energy consumption not only increase the operation cost of the mobile operator, but also cause influence on the environment. Therefore, the technologies to improve the energy and spectrum efficiency becomes the research hotspots of the wireless communication technology.This dissertation investigates the key energy and spectrum efficiency optimization technologies for the new generation wireless communication networks. To improve the energy and spectrum efficiency, and decrease the dependent on the traditional energy of the wireless communication networks, this dissertation investigates the joint resource allocation of the relaying cooperation networks, the optimal linear process scheme of the AF relay with fixed power allocation, base station DTX scheme for OFDMA cellular networks powered by the smart grid and the renewable energy cooperation and spectrum sharing among multi-systems.The main contributions of this dissertation are summarized as follows:1) Discontinuous Transmission (DTX) is an efficient technology to improve the energy efficiency of the wireless cellular networks. DTX enables the deactivation of some components of the base station in sufficient short time, which can decrease the energy consumption without affecting the normal operation of the mobile networks. Besides, this dissertation considers the wireless cellular networks powered by the smart grid which the renewable energy is integrated into. The smart grid has many different energy retailers with variant energy resource, such as solar energy, wind energy and conventional energy.Since the renewable energy is limited, each BS purchases energy from which retailers and how much energy should be purchased should be determined , which is called energy procurement. This dissertation jointly considers the DTX, resource allocation and energy procurement to maximize the profit of the network operators and minimize the greenhouse gas emissions. The joint optimization problem is formulated as a mixed integer programming problem. By exploiting the structure of the coupled constraint in the mixed integer programming problem, a distributed algorithm is proposed to significantly decrease the signaling and computational overhead. Simulation results illustrate the effectiveness of the proposed distributed algorithm to improve the revenue of the operators and decrease the GHG emissions.2) This dissertation studies the linear processing of amplify-and-forward (AF) relays for the multiple relays multiple users scenario. All relays are regarded as one "special relay", and then the subcarrier pairing, relay selection and channel assignment can be seen as a linear processing of the "special relay". Under fixed power allocation,the linear processing of AF relays can be regarded as a permutation matrix. Employing the partitioned matrix, an optimal linear processing design for AF relays is proposed to find the optimal permutation matrix based on the sorting of the received SNR over the subcarriers from BS to relays and from relays to users, respectively. Then, the optimality of the proposed linear processing scheme is proved. Through the proposed linear processing scheme, the optimal subcarrier paring, relay selection and channel assignment can be obtained under given power allocation in polynomial time. Simulation results illustrate that the proposed algorithm can achieve a perfect performance.3) This dissertation investigates the joint resource allocation for MIMO-OFDMA relaying system including subcarrier pairing, channel-user assignment, relay selection,transmission selection as well as power allocation. The joint resource allocation can be formulated as a joint optimization problem, which is a mixed-integer programming problem because of the combinatorial nature of subcarrier pairing, channel assignment,relay selection and transmission mode selection. Furthermore, there are three sum terms in the objective function. One of the sum terms indicates the cooperative transmission mode, and another two sum terms indicate the direct transmission mode in two time slots,respectively. The cooperative transmission sum term includes a fourth-order tensor which indicates a four-dimension assignment problem , which is difficult to tackle. This dissertation proposes an optimal algorithm using fourth-order tensor. In the first, relax the discrete variables in the mixed-integer programming problem into continuous, and then the Lagrange dual method is used to solve the power allocation. Next, the tensor which indicates the four-dimension assignment problem in cooperative transmission mode is decomposed into one matrix and some vectors. Then, the original optimization problem can be converted into one master problem and some simple linear programming subproblems which can be solved using general linear programming methods. Simulation results show the proposed algorithm can significantly improve the system throughput.4) Energy harvesting is one of the most important technologies of the green communication. Since the wireless systems usually have different traffic loads and available renewable energy, this dissertation considers the energy cooperation and spectrum sharing technology to decrease renewable energy waste and improve the spectrum efficiency. Specially, this dissertation proposes a flexible spectrum sharing scheme among multi-systems. Firstly, the wideband spectrum is divided into some narrow band carriers. Each system can flexibly select the narrow carriers which are not needed to be adjacent, and different systems can share the same narrow band carriers, which can improve the spectrum efficiency. Then, the carrier-aggregation technology is adopted to aggregate these narrow band carriers into wideband spectrum to support each wireless system. Moreover, this dissertation considers the energy cooperation among multi-systems to improve the renewable energy efficiency. Accordingly, the proposed model is formulated as a multi-objective mixed integer optimization problem. To solve it,this dissertation proposes a improved MOEA/D-M2M, where the simplex-dominance is presented, which can take the place of the pareto-dominance and enhance the convergence rate. Besides, the Lagrange dual method is also adopted to optimize the transmit power to eliminate the co-channel interference caused by the spectrum sharing. Extensive experimental studies prove that the proposed joint renewable energy cooperation and spectrum sharing scheme can effectively improve the renewable energy and spectrum efficiency and decrease the carbon emission. |
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