• Journal of Korea Multimedia Society
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• v.16 no.9
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• pp.1077-1088
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• 2013

As broadcasting is the process that a node sends a packet to all nodes in the network. it is basic process used for discovering of a routes to a node and disseminating of control information message in Mobile Ad hoc NETwork (MANET). In this paper, we propose dynamically adjusted probabilistic mechanism based on distance ratio and node density for broadcasting in MANETs. The distance ratio can be calculated as the ratio of the radio strength length to the distance from sender of a node, and node density can be get from 1-hop nodes of neighbours. A mobile node receiving broadcast packets determines the probability of rebroadcasting considering distance ratio and node density of itself. Rebroadcast probability will be set as low value to a node which is located in nearby area of sender and has high 1-hop node density, So it reduces packets transmission caused by the early die-out of rebroadcast packets. Compared with the simple flooding and fixed probabilistic flooding by simulation, our approach shows better performances results. Proposed algorithm can reduce the rebroadcast packet delivery more than 30% without scanting reachability, where as it shows up to 96% reachability compared with flooding.

• Smart Structures and Systems
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• v.6 no.5_6
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• pp.481-504
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• 2010

Wireless smart sensor networks (WSSNs) have been proposed by a number of researchers to evaluate the current condition of civil infrastructure, offering improved understanding of dynamic response through dense instrumentation. As focus moves from laboratory testing to full-scale implementation, the need for multi-hop communication to address issues associated with the large size of civil infrastructure and their limited radio power has become apparent. Multi-hop communication protocols allow sensors to cooperate to reliably deliver data between nodes outside of direct communication range. However, application specific requirements, such as high sampling rates, vast amounts of data to be collected, precise internodal synchronization, and reliable communication, are quite challenging to achieve with generic multi-hop communication protocols. This paper proposes two complementary reliable multi-hop communication solutions for monitoring of civil infrastructure. In the first approach, termed herein General Purpose Multi-hop (GPMH), the wide variety of communication patterns involved in structural health monitoring, particularly in decentralized implementations, are acknowledged to develop a flexible and adaptable any-to-any communication protocol. In the second approach, termed herein Single-Sink Multi-hop (SSMH), an efficient many-to-one protocol utilizing all available RF channels is designed to minimize the time required to collect the large amounts of data generated by dense arrays of sensor nodes. Both protocols adopt the Ad-hoc On-demand Distance Vector (AODV) routing protocol, which provides any-to-any routing and multi-cast capability, and supports a broad range of communication patterns. The proposed implementations refine the routing metric by considering the stability of links, exclude functionality unnecessary in mostly-static WSSNs, and integrate a reliable communication layer with the AODV protocol. These customizations have resulted in robust realizations of multi-hop reliable communication that meet the demands of structural health monitoring.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39B no.11
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• pp.763-770
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• 2014

In traditional routing protocols including LEACH for wireless sensor networks, nodes suffer from unbalanced energy consumption because the nodes require large transmission energy as the distance to the sink node increase. Multi-hop based routing protocols have been studied to address this problem. In existing protocols, each cluster head usually chooses the closest head as a relay node. We propose LEACH-CHT, in which cluster heads choose the path with least energy consumption to send data to the sink node. In our research, each hop, a cluster head selects the least cost path to the sink node. This method solves the looping problem efficiently as well as make it possible that a cluster head excludes other cluster heads placed farther than its location from the path, without additional energy consumption. By balancing the energy consumption among the nodes, our proposed scheme outperforms existing multi-hop schemes by up to 36% in terms of average network lifetime.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.13 no.1
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• pp.35-45
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• 2014

The driving environment of the vehicle has characteristics that the change of position, velocity and distance between vehicles is severe. The performance test of system must be carried out in the real road environments with consideration of the driving environment of vehicles to measure the performance correctly because the performance of vehicular communication systems is affected by the driving conditions of the vehicle. In this paper, we propose the test methods of V2V/V2I performance and V2V multi-hop transmission function and present the test results measured by the vehicular communication systems already developed. In the test result, we confirmed the fact that the distance of communication devices and the driving direction of vehicle are affecting the communication performance. We also confirmed the multi-hop transmission function using the driving vehicle in the limited area as the proposed test method.

• Journal of the Korean Society of Physical Medicine
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• v.15 no.1
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• pp.65-76
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• 2020

PURPOSE: The purpose of this study were to determine an intervention that involves proprioceptive exercises combined with cognitive task completion for adults with chronic ankle instability and to investigate the effects of the exercises on the static balance, dynamic balance, and ankle function of such individuals. METHODS: A total of 30 adults suffering from the aforementioned condition were randomly divided into experimental (n=15) and control (n=15) groups. The experimental group performed proprioceptive exercises in combination with cognitive tasks for 15 minutes in each session that was held three times a week for four 4 weeks, whereas the control group carried out only proprioceptive exercises. A Wii Balance Board, which enables examining the fluctuation area distance, and speed, was used to determine static balance; a Y-balance test kit was employed to measure dynamic balance; and the side hop, figure-of-8 hop, and square hop tests were conducted to ascertain ankle function. RESULTS: The results showed that the static balance, dynamic balance, and ankle function of both the experimental and control groups significantly improved. The participants were instructed to perform one-leg postural exercises with and without vision blocking for the affected leg. The experimental group showed more significant improvement than did the controls in terms of the fluctuation distance, speed, and area of static balance. CONCLUSION: In conclusion, although combined proprioceptive exercises and cognitive tasks were insufficient to enhance all types of balance among the subjects, it effectively reinforced their static balance.

• Journal of KIISE:Information Networking
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• v.34 no.6
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• pp.423-434
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• 2007

Vehicular ad-hoc network (VANET), a kind of mobile ad-hoc network (MANET), is a key technology for building intelligent transportation system (ITS). VANET is automatically and temporarily established through vehicle-to-vehicle communication without network infrastructure. It has the characteristics that frequent changes of network topology and node density are occurred and messages are disseminated through several relay nodes in the network. Due to frequent change of network topology and node density, however, VANET requires an effective relay node selection scheme to disseminate messages through the multi-hop broadcast. In this paper, we propose a contention window based multi-hop broadcast scheme for VANET. Each node has an optimized contention window and competes with each other for a relay node. The experimental results show that the proposed scheme has a better performance than the distance-based deterministic broadcast scheme in terms of message propagation delay and network traffic.

• Journal of Communications and Networks
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• v.12 no.2
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• pp.103-113
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• 2010

In this paper, a tradeoff between the total energy consumption-per-bit and the end-to-end rate under spatial reuse in wireless multi-hop network is developed and analyzed. The end-to-end rate of the network is the number of information bits transmitted (end-to-end) per channel use by any node in the network that is forwarding the data. In order to increase the bandwidth efficiency, spatial reuse is considered whereby simultaneous relay transmissions are allowed provided there is a minimum separation between such transmitters. The total energy consumption-per-bit includes the energy transmitted and the energy consumed by the receiver to process (demodulate and decoder) the received signal. The total energy consumption-per-bit is normalized by the distance between a source-destination pair in order to be consistent with a direct (single-hop) communication network. Lower bounds on this energy-bandwidth tradeoff are analyzed using convex optimization methods. For a given location of relays, it is shown that the total energy consumption-per-bit is minimized by optimally selecting the end-to-end rate. It is also demonstrated that spatial reuse can improve the bandwidth efficiency for a given total energy consumption-per-bit. However, at the rate that minimizes the total energy consumption-per-bit, spatial reuse does not provide lower energy consumption-per-bit compared to the case without spatial reuse. This is because spatial reuse requires more receiver energy consumption at a given end-to-end rate. Such degraded energy efficiency can be compensated by varying the minimum separation of hops between simultaneous transmitters. In the case of equi-spaced relays, analytical results for the energy-bandwidth tradeoff are provided and it is shown that the minimum energy consumption-per-bit decreases linearly with the end-to-end distance.

• Journal of KIISE:Information Networking
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• v.37 no.2
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• pp.157-161
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• 2010

Vehicular Ad-hoc NETworks (VANETs) suffer from frequent network disconnections due to obstacles such as buildings even in urban environments with high density of traffic. Thus, in this paper, we propose a routing algorithm that finds optimal end-to-end paths in terms of both traffic density and distance in the urban VANET and selects the next hop with the minimum distance, while maintaining the minimum hop counts over the path. The simulation results show that the proposed algorithm achieves higher throughput and smaller end-to-end delay than Greedy Perimeter Stateless Routing (GPSR) with message carrying.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.3
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• pp.491-497
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• 2012

Network coding is that the nodes can combine and mix the packets rather than merely forward them. Therefore, network coding is expected to improve throughput and channel efficiency in the wireless network. Relevant researches have been carried out to adapt network coding to wireless multi-hop network. In this paper, we designed the network coding for bidirectional traffic service in routing layer and IP layer of Ad-hoc network. From the simulation result, the traffic load and the end to end distance effect the performance of the network coding. As end to end distance and the traffic load become larger, the gain of network coding become more increased.

• Proceedings of the Korea Information Processing Society Conference
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• 2009.11a
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• pp.533-534
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• 2009

무선센서네트워크에서 많은 응용 프로그램들이 센서노드들의 위치 정보를 기반하기 때문에 센서노드에 대한 위치 측정은 매우 중요하다. 본 논문은 위치 정보를 알고 있는 소수의 앵커노드들을 사용하여 위치 측정 정확도를 높이고 주어진 위치 정보 메시지의 교환 비용을 줄이는 분산 위치 측정 기법인 Low-cost Localization using 2-hop Distance Anchors (LLTA)를 제안한다. LLTA는 높은 위치 측정 정확도를 위해 각각의 센서노드로부터 2 홉 거리 이내의 센서노드들의 위치 정보를 모으는 2-홉플러딩을 사용한다. 또한 2-홉 플러딩을 통해 얻은 위치 정보를 이용하여 센서노드가 위치할 수 있는 지역을 계산한 후 그리드 스캔 알고리즘을 사용하여 센서노드의 더 정확한 위치를 계산한다. 시뮬레이션 결과를 통해 LLTA가 기존의 위치 측정 기법들보다 위치 측정 정확도가 더 높고, 위치 정보 전달 비용이 더 낮음을 보인다.