• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.7
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• pp.3309-3328
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• 2017

The application of Internet of Things (IoT) in the next generation cellular networks imposes a new characteristic on the data traffic, where a massive number of small packets need to be transmitted. In addition, some emerging IoT-based emergency services require a real-time data delivery within a few milliseconds, referring to as ultra-low latency transmission. However, current techniques cannot provide such a low latency in combination with a mice-flow traffic. In this paper, we propose a dynamic resource reservation schema based on an air-interface slicing scheme in the context of a massive number of sensors with emergency flows. The proposed schema can achieve an air-interface latency of a few milliseconds by means of allowing emergency flows to be transported through a dedicated radio connection with guaranteed network resources. In order to schedule the delay-sensitive flows immediately, dynamic resource updating, silence-probability based collision avoidance, and window-based re-transmission are introduced to combine with the frame-slotted Aloha protocol. To evaluate performance of the proposed schema, a probabilistic model is provided to derive the analytical results, which are compared with the numerical results from Monte-Carlo simulations.

• Journal of Korea Society of Industrial Information Systems
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• v.25 no.2
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• pp.29-37
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• 2020

This paper proposes a multiple-relay-assisted single side band (SSB) space frequency block code (SFBC) single carrier (SC)-frequency division multiple access (FDMA) system and measures the performance of SSB SFBC SC-FDMA transmission system with the signal-to-noise power ratio SNR) between relays and a destination station. As we know, the performance of relay-assisted transmission systems can be easily improved by re-transmitting to the destination station after applying block code to the recovered transmitted signals of relays. In this paper, the performance improvement of the relay-assisted SSB SC-FDMA system can be obtained without any significant increase of system computational complexity by implementing block code with the complex conjugates symmetric characteristic of SSB system. The simulation result shows that the SNR performance of the proposed multiple-relay-assisted SSB SFBC SC-FDMA system is about 4 dB better than the performance of the single-relay-assisted SSB SC-FDMA system at the symbol error rate of 10^-2.

• Journal of KIISE:Information Networking
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• v.33 no.6
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• pp.451-460
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• 2006

In HMIPv6, the nested mobile network because of the mobility of node and router can be constituted. Many subnets exist and many mobile router(MR)s and mobile node(MN)s activate in the nested mobile network. If the nested depth is deeper, the number of mobile router that packet goes through, increases and data transmission delay owing to this might be larger. This paper proposes EPA algorithm which finds out the path from Mobility Anchor Point(MAP) to a destination mobile node using the binding cache information of MAP and processes the path information by adding it to packet header. If we apply EAP algorithm, the quantity of unnecessary packet within MAP domain can be decreased. Also, the transmission delay can be decreased in a intermediate mobile router because it supports packet re-transmission just by simple packet substitution.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.8
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• pp.1567-1576
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• 2015

This paper proposes a reliable real-time data dissemination protocol for mitigating transmission failure of real-time data in WSNs. The re-transmission is well-known for recovery of transmission failure, but this may violate the real-time requirement by transmission delay. To solve this problem, the proposed protocol exploits broadcasting nature and temporal opportunity allocation. In a radio-range of sending node, there may be neighbors satisfying the real-time requirement. The neighbors of specific node could receive data simultaneously by broadcasting, and decide their priority using temporal opportunity allocation method. The method uses time slot and tolerable time. The time slot specifies the priority and transmission deadline for each neighbors, and the tolerable time is the real-time requirement at the sending node. By giving the priority to the node with shorter tolerable time in each slot, we may get more opportunities to forward toward the destination. In other words, even if a node have the longer tolerable time, it still has a chance to forward with the real-time requirement. Simulation results show that the proposed protocol is superior to the existing protocols.

• ETRI Journal
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• v.26 no.6
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• pp.535-544
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• 2004

With video compression standards such as MPEG-4, a transmission error happens in a video-packet basis, rather than in a macroblock basis. In this context, we propose a semantic error prioritization method that determines the size of a video packet based on the importance of its contents. A video packet length is made to be short for an important area such as a facial area in order to reduce the possibility of error accumulation. To facilitate the semantic error prioritization, an efficient hardware algorithm for face tracking is proposed. The increase of hardware complexity is minimal because a motion estimation engine is efficiently re-used for face tracking. Experimental results demonstrate that the facial area is well protected with the proposed scheme.

• Bulletin of the Korean Chemical Society
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• v.31 no.2
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• pp.351-354
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• 2010

Nickel nanoparticles (Ni NPs) appeared to exhibit the catalytic activity in one-pot cyclocondensation reaction for the preparation of 3,4-dihydropyrimidine-2(1H)-ones via Biginelli reaction from aromatic/heteroaromatic/aliphatic aldehydes, urea/thiourea and ethyl acetoacetate under microwave irradiation has been described. The UV absorbance spectra showed metallic Ni characteristics and appreciate with the particle size determined by Transmission electron microscopy (TEM). After reaction course the Ni NPs can be re-covered and reused without any apparent loss of activity.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.22 no.4
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• pp.189-196
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• 2010

U-factor and solar heat gain coefficient(SHGC) usually can be used as the index to evaluate the thermal performance. U-factor is a concept for heat loss by the temperature difference between inside and outside, so it's useful to be applied in heating season. But SHGC that indicates the fraction of heat from incident solar radiation that flows through a window by means of optical transmission, as well as absorption, re-radiation and convection is for cooling season. In other words, U-factor and SHGC of windows by cities have to be reflected to select the window of the energy conservation. The purpose of this research is to analyze the energy use impacts by SHGCs of windows for detached house in Inchon and Ulsan through energy simulation by eQUEST.

• Journal of the Korean Operations Research and Management Science Society
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• v.35 no.2
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• pp.53-69
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• 2010

This paper proposes an ant-based routing algorithm, Ant System-Routing in wireless Senor Networks(AS-RSN), for wireless sensor networks. Using a transition rule in Ant System, sensors can spread data traffic over the whole network to achieve energy balance, and consequently, maximize the lifetime of sensor networks. The transition rule advances one of the original Ant System by re-defining link cost which is a metric devised to consider energy-sufficiency as well as energy-efficiency. This metric gives rise to the design of the AS-RSN algorithm devised to balance the data traffic of sensor networks in a decentralized manner and consequently prolong the lifetime of the networks. Therefore, AS-RSN is scalable in the number of sensors and also robust to the variations in the dynamics of event generation. We demonstrate the effectiveness of the proposed algorithm by comparing three existing routing algorithms: Direct Communication Approach, Minimum Transmission Energy, and Self-Organized Routing and find that energy balance should be considered to extend lifetime of sensor network and increase robustness of sensor network for diverse event generation patterns.

• Journal of Communications and Networks
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• v.5 no.2
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• pp.167-173
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• 2003

We treat the problem of channel estimation and interference cancellation in multiuser ultra-wide-band (UWB) communication systems over multipath fading channels. The UWB system under consideration employs a random time-hopping impulse radio format. We develop a channel estimation method based on linear weighted algorithm. An iterative channel estimation and interference cancellation scheme is proposed to successively improve the receiver performance. We also consider systems employing multiple transmit and/or receive antennas. For systems with multiple receive antennas, we develop a diversity receiver for the wellseparated antennas. For systems with multiple transmit antennas, we propose to make use of Alamouti’s space-time transmission scheme, and develop the corresponding channel estimation and interference cancellation receiver techniques. Simulation results are provided to demonstrate the performance of various UWB receiver techniques developed in this paper.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.12A
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• pp.1246-1252
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• 2006

In this paper, a collision probability, processing time and traffic capacity analysis algorithm for RFID system using random FHSS and synchronous FHSS is proposed. Service time, duty cycle, traffic intensity and additional delay time required for re-transmission due to collision are considered and the processing delay and frequency channel capacity are analyzed for the steady state operation of the system. The simulation results which show maximum capacity of the system and explain the accuracy of the algorithm are provided.