| 2 | A survey of next generation mobile communications researchin China显示文摘With the rapid development of wireless communication networks, the fourth generation (4G) has emerged to move beyond the limitations of the third generation (3G), with increased bandwidth, enhanced quality of services, and reduced costs of resources. In this paper, we discuss the key technologies of 4G and focus on surveying the ongoing research in 4G communications in China. The 4G technologies under investigation include multicarrier transmission, multiple antenna techniques, carrier aggregation, relays, cognitive radio, distributed antenna systems, network convergence, and network self-optimization. These technologies are the building blocks of 4G and contribute largely to the requirements of International Mobile Telecommunications Advanced (IMT-Advanced). For each technology, its benefits, research topics, and some existing approaches are examined. Finally, we briefly discuss the challenges and future research issues in 4G systems. | TIAN JinFeng 1,2 , ZHENG XiaoYing 2,3 , HU HongLin 1,2 YOU XiaoHu 1,3 1 Shanghai Research Center for Wireless Communications (WiCO), Shanghai 200335, China 2 Shanghai Institute of Microsystem and Information Technology (SIMIT), Chinese Academy of Sciences (CAS), Shanghai 200050, China 3 National Mobile Communications Research Laboratory, Southeast University (SEU), Nanjing 210096, China | 2011 | Chinese Science Bulletin2011，56，27： | 6 |
| 3 | Energy-efficient resource allocation for OFDMA relay systems with imperfect CSIT显示文摘In this paper, we propose an energy-efficient resource allocation scheme for the downlink of decodeand-forward relay-assisted orthogonal frequency division multiple access systems. The resource allocation is designed based on imperfect channel state information at the transmitter. We jointly optimize the power allocation, data rate allocation, and subcarrier allocation to maximize the system energy efficiency(EE). We formulate the EE problem as a probabilistic mixed non-convex optimization problem, in which the individual power constraints and the outage probability requirements are considered. An iterative algorithm based on bisection method is given to transform the optimization problem into a standard concave form. Also, we consider a proportional fairness design for the EE maximization problem. Simulation results illustrate the effectiveness of the proposed algorithm. | WANG XiaoMing ZHENG FuChun ZHU PengCheng MENG Chao YOU XiaoHu | 2015 | Science China(Information Sciences)2015，58，8： | 2 |
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