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Improving Handover Quality in 4G Mobile Systems
KIM, Dongwook,LEE, Hanjin,KIM, Namgi,YOON, Hyunsoo The Institute of Electronics, Information and Comm 2008 IEICE transactions on fundamentals of electronics, Vol.91 No.7
<P>In this paper, we propose a new handover algorithm to guarantee handover quality in 4G mobile systems. The proposed algorithm limits the handover interruption time by improving the HARQ retransmission latency of the first packet transmitted from new serving cell. Through the simulations, we proved that our algorithm meets the requirement of handover interruption time for TCP services with high rate.</P>
Sum-Rate Maximization Methods for Wirelessly Powered Communication Networks in Interference Channels
Kim, Hanjin,Lee, Hoon,Duan, Lingjie,Lee, Inkyu IEEE 2018 IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS Vol.17 No.10
<P>In this paper, we study a wireless powered communication network (WPCN) in a general <TEX>$N$</TEX>-user interference channel (IFC), where a hybrid access-point (H-AP) in each cell supports its corresponding user. In this multi-cell environment, the H-AP first sends the energy signal to charge users in the downlink (DL) phase, while in the subsequent uplink (UL) phase, each user transmits its information signal to the corresponding H-AP utilizing the previously harvested energy. For the WPCN in this IFC scenario, cross-link interference occurs due to asynchronous time allocation of the DL and the UL among <TEX>$N$</TEX> cells which significantly affects the overall performance. To handle the interference issue efficiently, we jointly optimize the DL and UL time allocation of each cell as well as the transmit power allocation at the H-APs and the users so that the weighted sum-rate of UL information transmission is maximized. To tackle non-convexity of the weighted sum-rate maximization problem, we propose an iterative algorithm where the time allocation and the transmit power are updated based on the weighted minimum mean square error criteria and the gradient projection method, respectively. Furthermore, we consider two simple protocols where the DL time allocation of each cell is synchronized and present resource allocation method, respectively. In simulation results, we verify that the proposed algorithm for the asynchronous protocol outperforms conventional schemes.</P>
Maximization of Minimum Rate for Wireless Powered Communication Networks in Interference Channel
Kim, Hanjin,Lee, Hoon,Jang, Seokju,Moon, Jihwan,Lee, Inkyu IEEE 2018 IEEE communications letters Vol.22 No.8
<P>We investigate wireless powered communication networks in an interference channel. In this system, due to asymmetric time allocation of the downlink and the uplink among multiple cells, cross-link interference may occur, which significantly affects overall performance. Considering this interference issue, we study a minimum rate maximization problem to overcome a severe imbalance on a rate distribution among users. The minimum rate maximization problem is non-convex; thus we propose an algorithm that updates the time allocation and the users’ transmit power based on the Lagrangian duality method and the Perron–Frobenius theorem, respectively. Simulation results verify that the proposed methods outperform conventional schemes.</P>
Kim, Sung Eun,Ko, Il Gyu,Shin, Mal Soon,Kim, Chang Ju,Ko, Young Gwan,Cho, Hanjin Medknow PublicationsMedia Pvt Ltd 2012 Neural regeneration research Vol.7 No.22
<P>Brain cell death after intracerebral hemorrhage may be mediated in part by an apoptotic mechanism. Colostrum is the first milk produced by mammals for their young. It plays an important role in protection and development by providing various antibodies, growth factors and nutrients, and has been used for various diseases in many countries. In the present study, we investigated the anti-apoptotic effects of bovine colostrum using organotypic hippocampal slice cultures and an intracerebral hemorrhage animal model. We performed densitometric measurements of propidium iodide uptake, a step-down avoidance task, Nissl staining, and caspase-3 immunohistochemistry. The present results revealed that colostrum treatment significantly suppressed N-methyl-D-aspartic acid-induced neuronal cell death in the rat hippocampus. Moreover, colostrum treatment improved short-term memory by suppressing hemorrhage-induced apoptotic neuronal cell death and decreasing the volume of the lesion induced by intracerebral hemorrhage in the rat hippocampus. These results suggest that colostrum may have a beneficial role in recovering brain function following hemorrhagic stroke by suppressing apoptotic cell death.</P>