• Journal of Information Processing Systems
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• v.11 no.1
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• pp.57-75
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• 2015

In evaluating the performance of a dual-hop wireless link, the effects of large and small scale fading has to be considered. To overcome this fading effect, several schemes, such as multiple-input multiple-output (MIMO) with orthogonal space time block codes (OSTBC), different combining schemes at the relay and receiving end, and orthogonal frequency division multiplexing (OFDM) are used in both the transmitting and the relay links. In this paper, we first make compare the performance of a two-hop wireless link under a different combination of space diversity in the first and second hop of the amplify-and-forward (AF) case. Our second task in this paper is to incorporate the weak signal of a direct link and then by applying the channel model of two random variables (one for a direct link and another for a relayed link) we get very impressive result at a low signal-to-noise ratio (SNR) that is comparable with other models at a higher SNR. Our third task is to bring other three schemes under a two-hop wireless link: use of transmit antenna selection (TAS) on both link with weak direct link, distributed Alamouti scheme in two-hop link and single relay antenna with OFDM subcarrier. Finally, all of the schemes mentioned above are compared to select the best possible model. The main finding of the paper is as follows: the use of MIMO on both hops but application TAS on both links with weak direct link and the full rate OFDM with the sub-carrier for an individual link provide a better result as compared to other models.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.4
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• pp.394-401
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• 2013

Recently there have been much interest in the performance improvement of maritime communication system. In the maritime communication system, the wireless channel is likely to be time-invariant and the retransmission scheme is not proper because it does not provide time diversity. For the improvement of reliability, we consider MIMO ARQ scheme using Alamouti-type signal which can provide space and time diversity. In this paper, we also propose the criterion of optimal retransmission order and provide its performance of error probability and packet throughput. The proposed MIMO ARQ scheme with optimal retransmission order has performance gain over random ordered MIMO ARQ and conventional Chase combining method. Therefore we expect that it can be adapted to the next generation maritime communication system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.8C
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• pp.771-776
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• 2006

We present a suboptimum decoding method for space-time trellis codes, which include maximum $likelihood(ML)^{[1]}$ and principal ratio $combining(PRC)^{[2]}$, over quasi-static flat fading channels. In the proposed scheme, the receive antennas are divided into K groups and the PRC is applied to each group, showing a flexible performances between ML and PRC. When K is determined, we also propose the optimum grouping rules and performance index(PI), which simply anticipate the relative performances. Moreover the performances are also evaluated when receive antennas are correlated. Finally, Computer simulations corroborate those theoretical results.

• Korean Institute of Interior Design Journal
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• no.39
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• pp.83-91
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• 2003

The planning of circulation area and circulation path are very important elements for layout of interior space of housing. This study is, therefore, aimed at synthetical review of that area from a functional, structural and socio-cultural point of view as well as typological analysis of that area. In the interior space of housing the networking of spaces according to the circulation route imply divers aspects of independent or dependant significances. It is thus, closely related with to whether circulation area open or closed, whether circulation path concentrated or distributed, and whether it passes Individual rooms or not. With regard to relationship with public and private spaces, there are many grounds for combining each other. This study also tried to develope program for planning of circulation system, utilizing typological analysis of them. At the same time this study suggests examples for layout of housing spaces. It is expected that the results represented In the form of systematic diagram will deserve to be a tool for providing an appropriate solution to the problem of diversity of user's needs.

• Journal of The Korea Institute of Healthcare Architecture
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• v.30 no.2
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• pp.23-34
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• 2024

Purpose: The Hybrid care environment, combining interventional procedures and surgeries in one space, is crucial for managing complex diseases, responding to emergencies, and reducing recovery times and pain. This study provides foundational data for creating architectural guidelines for a Hybrid Operating Unit in a general hospital's surgical department, focusing on cardiovascular care. Methods: The study analyzed the spatial and configuration types of the Vascular Angiography Unit and the Cardiac Operating Unit, which are the basic components of the Hybrid Operating Unit, through a literature review. Based on the initial research findings, interviews with experts were conducted. Results: In the Hybrid Operating Process, the study proposed spatial configuration alternatives that consider the positioning of medical staff and the types and arrangement changes of equipment, including Angiography, Heart-lung machines, and other surgical tools and instruments. Implications: The integration of the two units leads to increased diversity and demand for medical staff, equipment, and supplies during surgical and interventional procedures. Therefore, strategic spatial configurations and equipment placement are necessary to effectively respond to these needs.

• Journal of Internet Computing and Services
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• v.17 no.5
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• pp.51-58
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• 2016

The unprecedented power of cloud computing (CC) that enables free sharing of confidential data records for further analysis and mining has prompted various security threats. Thus, supreme cyberspace security and mitigation against adversaries attack during data mining became inevitable. So, privacy preserving data mining is emerged as a precise and efficient solution, where various algorithms are developed to anonymize the data to be mined. Despite the wide use of generalized K-anonymizing approach its protection and truthfulness potency remains limited to tiny output space with unacceptable utility loss. By combining L-diversity and (${\alpha}$,k)-anonymity, we proposed a hybrid K-anonymity data relocation algorithm to surmount such limitation. The data relocation being a tradeoff between trustfulness and utility acted as a control input parameter. The performance of each K-anonymity's iteration is measured for data relocation. Data rows are changed into small groups of indistinguishable tuples to create anonymizations of finer granularity with assured privacy standard. Experimental results demonstrated considerable utility enhancement for relatively small number of group relocations.

• Journal of Satellite, Information and Communications
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• v.5 no.2
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• pp.40-44
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• 2010

A layered coding scheme is one of the adaptive receiving techniques for unidirectional services such as multimedia broadcasting and multicasting services (MBMS), where we cannot utilize feedback information. The layered coding scheme can be used with hierarchical modulations by combining suitable code rates and modulation orders of each. In addition, it has been reported that hybrid and/or integrated satellite systems can effectively achieve transmit diversity gains by appropriate utilization of space time coding combined with turbo codes. This paper proposes a layered turbo coding schemes for hybrid and/or integrated satellite systems. We first introduce the system architecture and operational principle of the proposed scheme, and discuss the applicability.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.8
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• pp.15-26
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• 2011

In this paper, we present a new beamforming scheme for a downlink of multiuser multiple-input multipleoutput (MIMO) communication systems. Recently, a block-diagonalization (BD) algorithm has been proposed for the multiuser MIMO downlink where both a base station and each user have multiple antennas. However, the BD algorithm is not efficient when the number of supported streams per user is smaller than that of receive antennas. Since the BD method utilizes the space based on the channel matrix without considering the receive combining, the degree of freedom for beamforming cannot be fully exploited at the transmitter. In this paper, we optimize the receive beamforming vector under a zero forcing (ZF) constraint, where all inter-user interference is driven to zero. We propose an efficient algorithm to find the optimum receive vector by an iterative procedure. The proposed algorithm requires two phase values feedforward information for the receive combining vector. Also, we present another algorithm which needs only one phase value by using a decomposition of the complex general unitary matrix. Simulation results show that the proposed beamforming scheme outperforms the conventional BD algorithm in terms of error probability and obtains the diversity enhancement by utilizing the degree of freedom at the base station.

• Journal of Astronomy and Space Sciences
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• v.30 no.2
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• pp.79-82
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• 2013

We present the Hilbert-Huang transform (HHT) analysis on the quasi-periodic modulation of SMC X-1. SMC X-1, consisting of a neutron star and a massive companion, exhibits superorbital modulation with a period varying between ~40 d and ~65 d. We applied the HHT on the light curve observed by the All-Sky Monitor onboard Rossi X-ray Timing Explorer (RXTE) to obtain the instantaneous frequency of the superorbital modulation of SMC X-1. The resultant Hilbert spectrum is consistent with the dynamic power spectrum while it shows more detailed information in both the time and frequency domains. According to the instantaneous frequency, we found a correlation between the superorbital period and the modulation amplitude. Combining the spectral observation made by the Proportional Counter Array onboard RXTE and the superorbital phase derived in the HHT, we performed a superorbital phase-resolved spectral analysis of SMC X-1. An analysis of the spectral parameters versus the orbital phase for different superorbital states revealed that the diversity of $n_H$ has an orbital dependence. Furthermore, we obtained the variation in the eclipse profiles by folding the All Sky Monitor light curve with orbital period for different superorbital states. A dip feature, similar to the pre-eclipse dip of Her X-1, can be observed only in the superorbital ascending and descending states, while the width is anti-correlated with the X-ray flux.

• Korean journal of communication and information
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• v.34
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• pp.275-305
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• 2006

The main research question of this paper is as follows: How can broadcasting both cause the crisis in democratic participation and yet also offer the solution? The contradiction in broadcast localism has never been adequately resolved in spite of regulation at all in practice, in that localism simply cannot account for the diversity of modern life and for the external forces that incorporate local communities into much larger economic and communications network. The concept of locality in local television, however, has been multiplied and enlarged in order to adjust to "time-space compression". Recently the local television have been "interface" combining and negotiating the globalization of media market and the decentralization of political power, the economies of scale and the activation of local democracy, consequently aiming at the horizontal-cooperative network instead of old vertical-dependent one.