• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.8
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• pp.2590-2606
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• 2014

A problem related to deployment of femtocells is how to manage access of users to radio resources. On one hand, all resources of the femtocell can be reserved for users belonging to a closed subscriber group (CSG), which is a set of users defined by a femtocell subscriber. This approach, known as closed access, however, increases interference to users not included in the CSG as those users do not have a permission to access this femtocell. Contrary, resources can be shared by all users with no priority in an open access mode. In this case, the femtocell subscriber shares radio as well as backhaul resources with all other users. Thus, throughput and quality of service of the subscriber and the CSG users can be deteriorated. To satisfy both the CSG as well as non-CSG users, a hybrid access is seen as a compromise. In this paper, we propose a new approach for sharing radio resources among all users. As in common cases, the CSG users have a priority for usage of a part of resources while rest of the resources is shared by all users proportionally to their requirements. As the simulation results show, the proposed resource sharing scheme significantly improves throughput of the CSG users and their satisfaction with granted bitrates. At the same time, throughput and satisfaction of the non-CSG users is still guaranteed roughly at the same level as if conventional sharing schemes are applied.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.6
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• pp.2014-2034
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• 2015

This paper focuses on solving co-channel interference (CCI) issues arising in the open subscriber group (OSG) mode of heterogeneous networks (HetNets). Considering a general framework consisting of arbitrary number of picocells within a macro cell, where the inter-user interference (IUI) is the main CCI to macro user equipments (UEs), while the the inter-cell interference (ICI) is the major CCI to pico UEs. In this paper, three IA based transceiver design schemes are proposed. For macro cell, we uniformly use block diagonalization (BD) scheme to eliminate the IUI. And for picocells, three IA schemes are proposed to mitigate the ICI. The first scheme, named as zero forcing IA (ZF-IA) scheme, aligns the inter picocell interference onto an arbitrary sub-space of the cross-tier interference using ZF scheme. Considering the channel state information (CSI) of the desired channel of pico UEs, the second scheme, named as optimal desired sub-channel selected IA (ODC-IA) scheme, aligns the inter picocell interference onto a certain sub-space of the cross-tier interference, which guarantees the largest channel gain of the desired signal of pico UEs. The third IA scheme, named as maximum cross-tier interference selected IA (MI-IA) scheme, is designed for the system with less receive antennas. The inter picocell interference is aligned onto the space of the strongest cross-tier interference and only the interference on this space is nullified. The complexity analysis and simulations show that the proposed transceiver design schemes outperform the existing IA schemes in the OSG mode of HetNets, and the MI-IA scheme reduces the requirement of the receive antennas number with lower complexity.

• Health Policy and Management
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• v.28 no.4
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• pp.352-359
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• 2018

Background: The purpose of this study is to propose an analysis of trends and characteristics of high-cost patients who take over 40% of total national health insurance medical expenses. Methods: It has been analyzed the tendency of high-cost patients by open data based on the medical history information of 1 million people among national health insurance subscriber from 2002 to 2015. To conduct detailed study of characteristics of high-cost patients, multiple regression has been performed by sex, age, residence, main provider, and admission status based on the top 5% group. Results: The amount of medical expenses and the number of high-cost patients have gradually increased in decades. The number of high-cost patients for Korean won (KRW) 5,000,000 category has increased by 7.6 times, KRW 10,000,000 category has increased by 14.1 times in comparing of year 2002 and 2015. Top 5% medical expenses have increased by 4.6 times. In consideration of the characteristics of patients, the incidence of high medical expenses has been higher in female patients than male ones, the older patients than in the younger. Patients residence in Gyeonsang or Jeonla province have had a high incidence of medical expenses than other area. The disease including dementia, cerebral infarction, and cerebrovascular disease for high-cost patients has been also increased. Conclusion: The major increase factor for high medical expenses is the aging of population. The elderly population receiving inpatient care residing in the province that increases high medical costs have to management. There is an urgent need to develop a mechanism for predicting and managing the cost of high-cost medical expenses for patients who have a heavy financial burden.