• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.10
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• pp.2150-2162
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• 2012

In accordance with evolution of next-generation mobile Internet, 2G, 3G, 4G, and B4G mobile communication wireless access networks will be co-existed and service providers will be merged as an integrated service provider. In addition, multiple virtual service operators will appear. In order to provide complicated unified-services, in the future Internet, wireless network virtualization where network resource is shared by various service operators is necessary. Therefore, in this paper, we investigate network architectures and virtualization scenarios for wireless access network virtualization where various wireless access technologies are flexibly operated by multiple service providers over next-generation wireless access networks. We expect that the virtualization scenario and network architecture yielded from this study can play a role as a basis for development of wireless access network virtualization algorithms.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.10
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• pp.2085-2094
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• 2012

In this paper, we propose a wireless access network virtualization algorithm based on a digital unit (DU)-radio unit (RU) separated network structure in a cellular network with multiple radio access technologies (RATs). The proposed wireless access network virtualization algorithm consists of a baseline access network virtualization, RAT virtualization, and access path migration algorithms. Final wireless access network virtualization is performed by sequentially performing these procedures. Through system-level simulations which assume 3GPP LTE and WiMAX systems, the performance of the proposed wireless access network virtualization is evaluated in terms of system throughput for two scenarios according to asymmetry of network traffic load. Numerical results show that our proposed wireless access network virtualization algorithm achieves significant system throughput gain even in asymmetric traffic load and user distribution situations.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.6
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• pp.1453-1459
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• 2010

Recently, the aim of cold storage warehouse is not only to provide preservation of the quality of perishable foods but also to use state-of-the-art information systems to rapidly move products across the cold chain. An RFID (Radio Frequency Identification) is an automatic identification method that detects signals from mobile objects, and tracks and traces movement of the objects. RFID can be used to turn a cold storage warehouses into a real-time system. In this paper, we develop an cold storage management system to support the optimized business processes with RFID system. First of all, business processes in the cold storage warehouse are analyzed. Then design factors which should be considered for incorporating RFID are defined. Design values which set to the design factors can be extracted from using RFID deployment simulator. as a result, the design values make RFID to be efficiently integrated to existing business processes.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.1
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• pp.29-34
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• 2017

This paper considers hybrid beamforming for millimeter wave system in uplink transmission where multiple users send their data streams simultaneously. Hybrid beamforming has low-cost and low power consumption features compared to conventional digital beamforming schemes. We assume that each user uses one transmit antenna and sends one data stream, while the base station has multiple receive antennas and multiple radio frequency chains. Therefore, hybrid beamforming is performed only at the base station. We also assume that each user does not know instantaneous channel side information (CSI), while the base station is able to estimate the CSI from all users accurately. Under this channel assumption, the outage probability is not zero. We evaluate the outage probability of the considered hybrid beamforming as a performance metric through computer simulations. We show that the outage probability of hybrid beamforming approaches that of digital beamforming in some cases.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.4
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• pp.77-85
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• 2009

This paper proposes an efficient system level simulation method for MIMO-OFDM based system in the multi-cell environment. The proposed method analyzes effects of the cell structure, radio channel characteristics and user mobility. The user mobility effect on the system level performance is considered in both channel gain and distance. The receiver SINR calculation procedure is presented in the system which adopts MIMO-OFDM scheme under various system environments. This method can be flexibly extensible to various system environments and provides computationally efficient system level simulation technique which utilizes link level performance analysis. Extensive computer simulations results are presented to obtain the system performance in the various mobile cellular channels using the proposed method. Also this results are analyzed based on the packet error rate for different distances between the base station located in the center of the cell and the mobile user.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.47 no.5
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• pp.81-88
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• 2010

In this paper, we proposed an automatic music/non-music signal discrimination system from broadcasting audio signal as a preliminary study of building a sound source monitoring system in real broadcasting environment. By reflecting human speech articulation characteristics, we used three simple time-domain features such as energy standard deviation, log energy standard deviation and log energy mean. Based on the experimental threshold values of each feature, we developed a rule-based algorithm to classify music portion of the input audio signal. For the verification of the proposed algorithm, actual FM broadcasting signal was recorded for 24 hours and used as source input audio signal. From the experimental results, the proposed system can effectively recognize music section with the accuracy of 96% and non-music section with that of 87%, where the performance is good enough to be used as a pre-process module for the a sound source monitoring system.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.5
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• pp.438-444
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• 2016

In this paper, A real-time channel module which can apply the wireless propagation channel was developed using USRP and Lab-VIEW. When the proposed channel module is used in conjunction with the implemented HW(hardware) simulators for cognitive radio and frequency interference analysis and so on, it can increase the reliability about wireless propagation environments. In addition, the proposed module overcomes the limit of existing HW simulator that data transfer rate is limitative in communication system through the design of the inner parts. Along with this, it is possible to apply channel parameters necessary to estimate the easier communication performance. Also, this has the advantage that it can be flexibly applied in implementing the communication channel with the upcoming new scenarios. The proposed module can estimate the communication performance via constellation and BER using the implemented module.

• Journal of Broadcast Engineering
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• v.16 no.5
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• pp.693-704
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• 2011

As mobile devices become multi-functional, and converge into a single platform, there is a strong need for a codec that is able to provide consistent quality for speech and music contents. MPEG-D USAC standardization activities started at the 82nd MPEG meeting with a CfP and approved Study on DIS at the 96th MPEG meeting. MPEG-D USAC is converged technology of AMR-WB+ and HE-AAC V2. Specifically, USAC utilizes three core codecs (AAC, ACELP, and TCX) for low frequency regions, SBR for high frequency regions, the MPEG Surround for stereo information, and window transition technology for smoothing transition between various core coder. USAC can provide consistent sound quality for both speech and music contents and can be applied to various applications such as multi-media download to mobile devices, digital radio, mobile TV and audio books.

• Journal of the Korean Society of Radiology
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• v.8 no.7
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• pp.377-382
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• 2014

Because of using computer system in the field of medical radiology, many artifacts which can not be seen in film/screen system are being created, especially ghosting artifacts. This artifacts could be yielded by taking advantage of a flat panel Thin-Film Transistor array detector. Ghosting artifacts can be rarely seen in clinical practice when an image that has a high-contrast object within a region of high exposure is quickly followed by another image that puts the high-contrast ghosting image in an area of lower radiation exposure. In this experiment, the ghosting artifacts were minimized for approximately 3 minutes with the unaided eye and almost disappeared for 6 minutes quantitatively between exposures. Moreover, the artifacts were influenced by more tube voltage than current and those depended not upon the number of readout cycles, but upon time.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.5
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• pp.61-66
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• 2012

We propose a traffic information service system for which traffic data are transmitted over vehicle ad-hoc network from neighbor vehicles, and eventually provided to the traffic information center through a few gateway vehicles which are capable of inter-working with the infrastructure network like 3G. The center broadcasts the traffic information through the FM radio. The proposed scheme allows collecting and analyzing traffic status of large areas without incorporating separated monitoring systems, e.g., probe cars and enables to provide accurate traffic information to drivers in timely manner. We also evaluate its performance by ns-3 simulation.