• Journal of the Korea Institute of Military Science and Technology
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• v.11 no.1
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• pp.15-24
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• 2008

The data delivery confirmation method of MIL-STD-188-220C, which is a tactical wireless mobile Ad-Hoc communication protocol, is that a source node requires the end-to-end ack from all destination nodes and the data-link ack from 1-hop neighboring destination nodes and relaying nodes, regardless of the hop distance from a source node to destination nodes. This method has the problem to degrade the whole communication network performance because of excessive data traffic due to the duplicate use of end-to-end ack and data-link ack, and the collision among end-to-end acks on the wireless network in the case of confirming a data delivery within an 1-hop distance. In order to solve this problem, this paper has proposed the method to perform the data delivery confirmation with the improvement of communication network performance through the data traffic reduction by achieving the reliable data delivery confirmation requiring the only data-link ack within an 1-hop distance. The effects of the proposed method are analyzed in the two aspects of the data delivery confirmation delay time and the data delivery confirmation success ratio.

• Journal of Communications and Networks
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• v.16 no.4
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• pp.465-474
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• 2014

Wireless sensor network (WSN) is considered to be one of the most important research fields for ubiquitous healthcare (u-healthcare) applications. Healthcare systems combined with WSNs have only been introduced by several pioneering researchers. However, most researchers collect physiological data from medical nodes located at static locations and transmit them within a limited communication range between a base station and the medical nodes. In these healthcare systems, the network link can be easily broken owing to the movement of the object nodes. To overcome this issue, in this study, the fast link exchange minimum cost forwarding (FLE-MCF) routing protocol is proposed. This protocol allows real-time multi-hop communication in a healthcare system based on WSN. The protocol is designed for a multi-hop sensor network to rapidly restore the network link when it is broken. The performance of the proposed FLE-MCF protocol is compared with that of a modified minimum cost forwarding (MMCF) protocol. The FLE-MCF protocol shows a good packet delivery rate from/to a fast moving object in a WSN. The designed wearable platform utilizes an adaptive linear prediction filter to reduce the motion artifacts in the original electrocardiogram (ECG) signal. Two filter algorithms used for baseline drift removal are evaluated to check whether real-time execution is possible on our wearable platform. The experiment results shows that the ECG signal filtered by adaptive linear prediction filter recovers from the distorted ECG signal efficiently.

• Journal of Electrical Engineering and Technology
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• v.2 no.1
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• pp.123-128
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• 2007

SPWPM traditional software development is surveyed and essential problems are investigated on the basis of system wireless link considerations. This paper presents the current state software planning tools for wireless LAN link optimization. The software directory is based on combination of MatLab and MapInfo software and measurement which gives the best grouping parameters to build up the software development. Among the requirements assumed, the WLAN site selections must be Line-of-sight (LOS) or near line of sight (NLOS) field strength prediction for either point to point or point to multi points. The results obtainable the out put of the program include two-dimensional (2D) and three dimensional (3D) plots for creating the link; design parameters through GUI representing the height and location for each antenna is depending on K-factor of the area and transmit antenna location.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.10a
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• pp.578-580
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• 2009

Wireless Sensor Networks(WSNs) has been used for various applications. It is optimized to low power operation than various function and transmission reliability because of limited power by batteries. but it is necessary to guarantee of reliability for using exact data for more diversity purpose. In WSNs environment composed by multi-hop, it is guarantee to end-to-end transmission reliability based hop-by-hop reliability. however, IEEE 802.15.4 standard is not consider link-layer reliability. in this paper, we propose energy efficient Reliable Link-layer Protocol for Wireless Sensor Networks.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.1B
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• pp.16-23
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• 2009

This paper investigates how many optimal routes can be established in terms of a given wireless mesh routing metric. Although many of routing metrics have been devised to precisely derive the wireless link quality in mesh, most (if not all) metrics have not been evaluated their optimality along with routing protocols. We consider stateof-the-art routing metrics and a widely accepted routing protocol in order to observe the optimality of established routes varying the number of source nodes. Also, we propose a unidirectional routing to deal with possible link asymmetry feature in wireless links. Through comparative simulation evaluations, we show that the portion of optimally established routes becomes less as the network traffic load increases, regardless of employed metrics, network topologies, and routing protocols.

• Journal of Digital Contents Society
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• v.10 no.2
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• pp.279-289
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• 2009

As the TCP is the protocol designed for the wired network that packet loss probability is very low, because TCP transmitter takes it for granted that the packet loss by the wireless network characteristics is occurred by the network congestion and lowers the transmitter's transmission rate, the performance is degraded. In this article, we suggest the newly improved algorithm using two parameters, the local retransmission time value and the local retransmission critical value to the BS based on the Snoop. This technique adjusts the base stations local retransmission timer effectively according to the wireless link status to recover the wireless packet loss rapidly. We checked that as a result of the suggested algorithm through various simulations, A-Snoop protocol improve more the wireless TCP transmission rate by recovering the packet loss effectively in the wireless link that the continuous packet loss occur than the Snoop protocol.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.25 no.6
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• pp.1515-1523
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• 2015

It has been prevalent to be serviced through WLAN(Wireless Local Area Network) as a variety of mobile devices have been introduced. If the number of mobile devices increases rapidly for the network access in a limited range of ESS(Extended Service Set), a lengthy connection delays are induced due to the initial link setup process of the IEEE 802.11i which is WLAN security standard. In this paper, we propose a new initial link setup protocol which can be executed in the ESS area of WLAN.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.11
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• pp.123-129
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• 2011

In terrestrial wireless optical communication links, atmospheric effects including turbulence, absorption and scattering have significant impact on the system performance. Based on the analysis of transmission in atmospheric channel concerning 830[nm] wavelength diode laser beam, performance of free space optical (FSO) link utilizing Galilean optics as a laser beam transmitting and receving optics, PIN photodiode as a detecting device. In this paper we designed optical link equation for received optical power and we analyze the atmospheric effects on the signal to noise ratio (SNR) and bit error rate (BER) of an terrestrial FSO system. We show that the possible communication distance for BER=$10^{-9}$ in proposed adverse atmospheric conditions.

• Journal of Information Processing Systems
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• v.8 no.1
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• pp.1-20
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• 2012

The most important criterion for achieving the maximum performance in a wireless mesh network (WMN) is to limit the interference within the network. For this purpose, especially in a multi-radio network, the best option is to use non-overlapping channels among different radios within the same interference range. Previous works that have considered non-overlapping channels in IEEE 802.11a as the basis for performance optimization, have considered the link quality across all channels to be uniform. In this paper, we present a measurement-based study of link quality across all channels in an IEEE 802.11a-based indoor WMN test bed. Our results show that the generalized assumption of uniform performance across all channels does not hold good in practice for an indoor environment and signal quality depends on the geometry around the mesh routers.

• Ocean Systems Engineering
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• v.8 no.1
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• pp.33-39
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• 2018

The paper presents a numerical underwater channel model developed in MATLAB for estimating the optical link budget between a light emitting diode (LED) based optical transmitter and a photo diode (PD) receiver when operated in the harbor, coastal and deep waters locations in the Bay of Bengal. The water samples are collected at different locations in the Bay of Bengal using a water sampler during an offshore research cruise. The optical attenuation, the main inherent parameter determining the range of the optical communication link is identified for the different waters using an underwater irradiance measurement system in the laboratory. The identified parameters are applied to the numerical model and found that a 10 W LED and a photo diode based system can provide the optical budget required for a horizontal underwater communication range of about 0.5, 14 and 35 m in the harbor, coastal and deep waters locations respectively. By increasing the transmitter power to 50 W, the operating range of the communication link could be increased up to 53 m in deep water locations in the Bay of Bengal.