• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.5A
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• pp.417-425
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• 2005

KOINONIA is high-rate Wireless Personal Area Network (WPAN) technology, and is developed for multimedia traffic transmission in personal area. A KOINONIA piconet is a collection of one or more associated slaves under a single master. Efficient scheduling of a master for the traffic of slaves is essential to use channel effectively and to guarantee QoS of multimedia traffic. We propose a new scheduling algorithm to allocate channel time at desired intervals regardless of superframe length, and a Connection Admission Control(CAC) algorithm to regulate the number of traffics in a piconet. Our proposed algorithms have been shown to save channel time and to meet QoS requirements compared to the conventional weighted round-robin algorithm.

• Journal of the Korea Institute of Military Science and Technology
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• v.16 no.2
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• pp.160-168
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• 2013

In tactical environment, tactical wireless networks are generally comprised of Tactical MANETs(T-MANETs) or Tactical WMNs(T-WMNs). The most important services in tactical network are voice and low rate data such as command control and situation awareness. These data should be forwarded via multi-hop in tactical wireless networks. Urgent and mission-critical data should be protected in this environment, so QoS(Quality of Service) must be guaranteed for specific type of traffic for satisfying the requirement of a user. In IEEE 802.11s, TDMA-based MAC protocol, MCCA(MCF Controlled Channel Access), has a function of resource reservation. But 802.11s protocol can not guarantee the end-to-end QoS, because it only supports reservation with neighbors. In this paper, we propose the routing protocol, R-HWMP(Reservation-based HWMP) which has the resource reservation to support the end-to-end QoS. The proposed protocol can reserve the channel slots and find optimal path in T-WMNs. We analyzed the performance of the proposed protocol and showed that end-to-end QoS is guaranteed using NS-2 simulation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.8A
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• pp.656-663
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• 2005

This paper presents a multi-channel enhancement scheme for the MAC protocol of IEEE 802.15.3 High-rate WPAN (Wireless Personal Area Network). The current MAC protocol of the IEEE 802.15.3 High-rate WPAN is designed for sharing a single channel among DEVs of a piconet; that is, within a single piconet, PNC prevents interference through MAC layer assignment of time slots to other DEVs using time-division multiple access. When the number of DEVs that communicate with each other frequently, is increased in a single WPAN, the size of the superframe becomes inevitably large, and this may result in a significant throughput drop or a failure to provide QoS guarantee. A multi-channel enhancement scheme for the MAC protocol of IEEE 802.15.3 High-rate WPAN is proposed to significantly increase the aguegate throughput and more reliably provide the QoS guarantees in a piconet

• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.6
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• pp.749-756
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• 2015

In this paper, we propose a unique systolic structure and communication algorithm that maintains a solid link between nodes using synchronous digital communication and enables low power communication. This system was designed by using CC2500 RF transceiver, CC2590 RF front end and C8051F330 low power microcontroller. The measurement of power consumption in the network link shows below $400{\mu}W$ in data transfer rate 320bps. The system constitutes the base unit of low power wireless network that was composed of each seven link nodes having eight sensor nodes. Results of the experiments show that link nodes using a 4Ah battery could operate over 3 years without replacement.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.6B
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• pp.508-516
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• 2006

The explosive growth of wireless network users and the existence of various wireless services have demanded high rate throughput as well as user's QoS guarantees. Towards this, this paper proposes QoS-oriented subcarrier allocation scheme considering the QoS provisioning of multiple users, which is major requirement for wireless network design point of view. This paper introduces joint RR/K&H combined with M-LWDF(Modified Largest Weighted Delay First) scheme throughout observing statistical channel behavior and real time queuing analysis for appropriate resource allocation tightly connected to multiuser scheduling. Accordingly, the system throughput can be enhanced, and the QoS demanded for delay sensitive services can be satisfied. Furthermore, the proposed scheme is applied for OFDMA(Orthogonal Frequency Division Multiple Access) systems to allocate sub-carriers in optimal way. The simulation results verify plausible performances of proposed resource allocation scheme via showing superior effective capacity under time-varying physical-layer channel behaviors.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.2
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• pp.393-402
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• 2017

Just like terrestrial cellular networks, underwater cellular communication networks, which can manage the overall network resource by adaptively allocating backhaul resource for each base station according to its ingress traffic, are necessary. In this paper, a new resource allocation protocol is proposed for the underwater cellular communication network, allocating backhaul resource of a base station proportional to its ingress traffic to the base station. This protocol is classified into two types dependent upon allocation period: the resource allocation protocol with adaptive period and that with fixed period. In order to determine a proper resource allocation protocol, the performance of the two protocols, in terms of reception rate, message overhead, and latency is compared and investigated via simulation. As a result, the resource protocol with adaptive period outperforms that with fixed period; the resource allocation protocol with fixed period results in a maximum of $10^2$ order longer queueing delay as well as $10^2$ order greater message overhead than that with adaptive period.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.1
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• pp.99-108
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• 1999

In this paper, we propose $\pi$/4 QPSK scheme with block modulation algorithm, which can reduce preamble in order to transmit ATM cell efficiently in the uplink channel of LMDS, and also designed a new carrier recovery circuit which can improve carrier synchronization performance of block demodulation algorithm. The $\pi$/4 QPSK scheme employing the proposed block modulation algorithm achieved efficient frame transmission by making use of a few preamble when carrier synchronization, symbol timing synchronization and slot timing synchronization were performed by burst data of ATM cell in LMDS environment. For performance evaluation of the proposed method, a simulation analyzing the variation of carrier synchronization, symbol timing synchronization and slot timing synchronization using LMDS environment and burst mode condition was executed. In the simulation, the proposed method showed a good performance even though the reduced preamble as a few aspossible when carrier synchronization, symbol timing synchronization and slot timing synchronization is performed.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.7
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• pp.273-281
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• 2003

This paper proposes a new time synchronization scheme for the Automatic Identification System(AIS). The proposed scheme utilizes a Temperature Compensated Crystal Oscillator(TCXO) as a local reference clock, and consists of a Digitally Controlled Oscillator(DCO), a divider, a phase comparator, and register blocks. Primary time reference is IPPS from GPS receiver that is synchronized to Universal Time Coordinated(UTC). And if GPS is unavailable, other station's signal is utilized as secondary time reference. The phase comparator measures time difference between the 1PPS and the generated transmit clock. The measured time difference is compensated by controlling the DCO and the transmit clock is synchronized to the Universal Time Coordinated(UTC). The synchronized transmit clock(9600Hz) is divided into the transmitting time slot(37.5Hz). The proposed scheme is tested in an experimental AIS transponder set. The experimental result shows that the proposed module satisfies the timing specification of the AIS technical standard, ITU-R M.1371-1.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.7
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• pp.55-60
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• 2017

This paper is proposed on the transmit Method Finger-Printer Scanning of Mutual Capacitance Touch Screen Panel Using Differential Pulse for improving the security of computer information. This system is composed of differential pulse generator and Ring-Counter, also Supply voltage is 5V. this system generates the Pulse wave which is composed of In-Phase and Out of Phase at 1MHz while period of 2m/s. it is designed and be able to operate four channels. overall power consumption is approximately 78.08nW. This prototype is implemented in 0.25um CMOS Process and Chip area is $870um{\times}880um$.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.6
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• pp.1529-1540
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• 1993

The quenching of steels by water is one of the imprtant problems in the applications of heat treatment, but the fundamental researches by way of theoretical approaches have not been satisfactorily improbed yet. This study aimed at measuring the exact subcooled transient boiling curve for cylindrical specimens and at conducting the analytical researches into the prediction of cooling curves, including the latent heat of phase transformation of steel. Experiments of quenching were made with cylindrical specimens of carbon steel S45C of diameters from 12 to 30 mm and with Cu specimens of 12 mm diameter respectively. The internal temperature of specimens during the quenching process was measured by C-A sheathed thermocouple. The heat fluxes were numerically calculated by the numerical method of inverse heat conduction problem, using the measured inner temperature of specimen as a boundary condition. In case of ${\Delta}T_{sub}=80K$, $q_{s}$ is as follows $q_{s}=2.02{\times}10^{5}{\Delta}T_{set}^{0.05}:{\Delta}T_{set}\le500K.$ And the numerical analysis of unsteady heat conduction during the quenching process was made and the cooling curves were calculated by TDMA method.