• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.9
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• pp.3276-3292
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• 2015

Relay-assisted D2D communication extends the communication range of the D2D pairs and helps users to form D2D pairs effectively. However, due to the introduction of the multi-hop relaying, the D2D communication has to occupy extra transmission time, which may decrease the efficiency of the communication system. In this paper, we propose a scheme to make node receive D2D signal and BS signal at overlapping time to improve the spectrum efficiency according to ZigZag decoding and successive-interference-cancellation (SIC). In this way, more data can be delivered during the same duration, thus the network throughput can be further improved. Numerical results verify the performance improvement of the proposed scheme when compared with a baseline scheme. Moreover, we expand the proposed scheme from one-hop relay scenario to multi-hop relay scenario.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.3
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• pp.477-493
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• 2011

The IEEE 802.16 mobile multi-hop relay (MMR) task group 'j' (TGj) has introduced the multi-hop relaying concept in the IEEE 802.16 Wireless MAN, wherein a relay station (RS) is employed to improve network coverage and capacity. Several RSs can be deployed between a base station and mobile stations, and configured to form a tree-like multi-hop topology. In such architecture, we consider the problem of a path selection through which the mobile station in and outside the coverage can communicate with the base station. In this paper, we propose a new path selection algorithm that ensures more efficient distribution of resources such as bandwidth among the relaying nodes for improving the overall performance of the network. Performance of our proposed scheme is compared with the path selection algorithms based on loss rate and the shortest path algorithm. Based on the simulation results using ns-2, we show our proposal significantly improves the performance on throughput, latency and bandwidth consumption.

• Korean Journal Plant Pathology
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• v.14 no.6
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• pp.618-621
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• 1998

In pseudoperonospora humuli, the cause of hop downy mildew, environmental and host factors affecting laboratory production of oospore were examined. After 7 days incubation of leaf disk inoculated with sporangia on water, additional incubations were carried out under different conditions of temperature and moisture. Oospore production was also compared between very susceptible (Nugget) and resistant (Fuggle) hop cultivars. Oospores were not produced at 18$^{\circ}C$ regardless of other incubation conditions. Leaf disks failed to produce oospore when incubated on water for up to 18 days at 8$^{\circ}C$. No oospores formed on infection sites without necrosis. However, abundant oospores were produced at necrotized infection sites when inoculated leaf disk incubated on dry filter paper for 5 days at 8$^{\circ}C$. Both susceptible and resistant hop cultivars produced abundant oospores. In the measurement of optimal temperature for oospore production, oospores were produced at 6 to 12$^{\circ}C$ Most abundant oospores were produced at 8$^{\circ}C$. We suggest that proper combination of low temperature, dryness and necrosis may be a critical environmental factors for oospore production of P. humuli.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.9A
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• pp.796-800
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• 2011

An energy-efficient multi-hop scheme based on cooperative MIMO (multiple-input multiple-output) technique is proposed for wireless sensor networks, taking into consideration the modulation constellation size, transmission distance, and extra training overhead requirement. The scheme saves energy by selecting the hop length. In order to evaluate the performance of the proposed scheme, a detailed analysis of the energy and delay efficiencies in the proposed scheme compared with the equidistance scheme is presented. Results from numerical experiments indicate that by use of the proposed scheme significant savings in terms of total energy cousumption can be achieved.

• Journal of Communications and Networks
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• v.16 no.2
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• pp.155-161
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• 2014

Mobility can lead to continual loss of data and service interruptions during communications in multi-hop cognitive radio networks. Mobility of primary users (PUs) or cognitive users (CUs) requires adjustment of multi-hop communications among CUs to avoid any interference to PUs. To provide durable and reliable data routing that ensures continuous network service, we propose mobility-aware cognitive routing (MCR) for multi-hop cognitive radio networks. MCR examines the risk level of each node against interference regions and selects the most reliable path for data delivery using a Markov predictor. Through simulation, we verify that the proposed scheme can avoid route destruction preemptively and achieve reliable data delivery.

• Journal of the military operations research society of Korea
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• v.18 no.2
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• pp.126-139
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• 1992

In this paper, the computational problems of packet transmission probability (PTP) in a computer communication network (CCN) under flooding routing are investigated. To avoid a congestion under this routing, two control methods are considerd, i. e., copy storage control and hop count control. Problems of PTP under flooding routings with these two control methods are respectively shown to be equivalent to those of source-to-terminal reliability(STR) with an exception for a case of hop count control where the hop count is less than the length of the longest path. For this exceptional case, an efficient computational algorithm for PTP is developed. This algorithm is proposed as an efficient tool for the determination of hop count which satisfies a given reliability constraint. A numerical example illustrates a proposed algorithm.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2002.05a
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• pp.402-408
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• 2002

Multicast technology allows the transmission of data from one source node to a selected group of destination nodes. Multicast routes typically use trees, called multicast routing trees, to minimize resource usage such as cost and bandwidth by sharing links. Moreover, the quality of service (QoS) is satisfied by distributing data along a path haying no more than a given number of arcs between the root node of a session and a terminal node of it in the routing tree. Thus, a multicast routing tree for a session can be represented as a hop constrained Steiner tree. In this paper, we consider the hop-constrained multicast route packing problem with bandwidth reservation. Given a set of multicast sessions, each of which has a hop limit constraint and a required bandwidth, the problem is to determine a set of multicast routing trees in an arc-capacitated network to minimize cost. We propose an integer programming formulation of the problem and an algorithm to solve it. An efficient column generation technique to solve the linear programming relaxation is proposed, and a modified cover inequality is used to strengthen the integer programming formulation.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.10a
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• pp.121-124
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• 2001

Dynamic Source Route(DSR) protocol is a simple and efficient routing protocol designed specially for use of the multi-hop Ad Hoc Network. DSR allows the network to be completely self-organized and self-configured without the need for any existing infrastructure or administration. DSR protocol consists of the two mechanisms of Router discovery and Router Maintenance, works entirely On-demand in all aspects. In this paper, we will present the performance of DSR protocol on the multi-hop wireless Ad Hoc Networks, illustrate it with simulation, and then analysis the algorism of DSR.

• Journal of Communications and Networks
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• v.16 no.4
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• pp.421-429
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• 2014

We consider the problem of scheduling communications in wireless sensor networks (WSNs) to ensure battery preservation through the use of the sleeping mode of sensors.We propose a communication protocol for 1-hop WSNs and extend it to multi-hop WSNs through the use of a 1-hop clustering algorithm.We propose to schedule communications in each cluster in a virtual communication ring so as to avoid collisions. Since clusters are cliques, only one sensor can speak or listen in a cluster at a time, and all sensors need to speak in each of their clusters at least once to realize the communication protocol. We model this situation as a mathematical program.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.9 no.1
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• pp.7-12
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• 2010

In this paper, we propose a new prioritized Optical Burst Switching (OBS) protocol based on a hop count, which can provide an efficient utilization in optical Wireless networks. Under several legacy schemes, a switch drops the burst with a shorter time among ones regardless of its traversed hop counts. As a result, the dropped burst that have been traversed more hops might cause to waste bandwidth than the one traversed a few hops. Noting that this problem, we propose the Just Enough Time (JET) with a hop count scheme which can reduce the wasted bandwidth by prioritizing the burst traversed more hops over others. From the simulation result, we show that the proposed scheme is advantageous over the legacy schemes in terms of the burst blocking probability and the link utilization.