• Korea Multimedia Society
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• v.12 no.4
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• pp.28-40
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• 2008

Vehicular ad hoc networks (VANETs) are a practical application class of wireless ad hoc networks, which consist of moving vehicles equipped with radio communication capabilities that collaborate to form a temporary network. This paper addresses issues and protocols of multihop routing in such emerging networks in the context of safety and infotainment applications. Due to the highly dynamic mobility of vehicles, frequent link breakage and short connection time are inevitable and, thus, the routing is a challenging task and interest for many researchers and industrial community. The frequent and dynamic change of topology makes the topology-based routing unreliable but the position-based routing more effective. The position-based routing consists of the location service which maps a node id to a geo-graphical position and the forwarding scheme which selects the next hop based on geo-graphical information of the node, its neighbors and the destination. The routing techniques are further categorized into geographical forwarding, trajectory forwarding and opportunistic forwarding based on the forwarding scheme. In this paper, we first present the distinguished properties of VANETs and the challenges and intractable issues posed in designing the routing protocols, followed by the comprehensive survey of existing routing protocols. Then, the different routing protocols designed for VANETs are compared in terms of characteristics, performance and application domains.

• Journal of Internet Computing and Services
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• v.15 no.3
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• pp.53-62
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• 2014

DTN is the next generation network that is used in not guaranteed end-to-end connection such as communication between planet and satellite, frequent connection severance, and not enough for qualified network infrastructure. In this paper, we propose the hybrid Spray-and-Wait algorithm to predict the node contact time by monitoring the periodic contacts information between the nodes. Based on this method, we select one node on the basis of prediction time and copy a message for spray and wait algorithm. In order to verify the the hybrid Spray and Wait algorithm, we use the ONE(Opportunistic Network Environment) Simulator of Helsinki University. The delivery probability of the proposed algorithm is compared to the Binary Spray and Wait algorithm, it is showed that it has 10% less overhead than Binary Spray and Wait routing. It has also shown that it reduces unnecessary copying of this message.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.7B
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• pp.536-549
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• 2012

An ad hoc network consists of nodes with limited energy. Therefore, the data transmission can fail abruptly due to lack of energy of transmitting node. A previous work PAMP proposed to build multiple low-energy paths to support stable packet delivery exploiting the nodes with low energy. It has energy-reservation scheme and multi-path selection scheme for stationary wireless ad hoc networks. In this paper, we propose an extended version of PAMP by incorporating network coding opportunity in path selection process. The simulation results show that our proposed scheme shows better packet delivery ratio and lower energy consumption compared with PAMP and a legacy energy-aware multipath routing protocol REAR.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.10 no.5
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• pp.424-434
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• 2017

In industrial wireless sensor networks, many applications require integrated QoS supporting. This paper proposes a reliable protocol for real-time monitoring in industrial wireless sensor networks. Retransmission is well-known to recover the transmission failure, however, this might cause the time delay to violate the real-time requirement. The proposed protocol exploits broadcasting feature of wireless networks and the temporal opportunity concept. The opportunities to relay the data packets are shared by the broadcasting feature and the temporal opportunity concept maximize the number of candidates in communication. Simulation results show that the proposed protocol is superior to the existing real-time protocols in term of real-time service and reliability.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.8
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• pp.1770-1785
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• 2013

In this paper, a multi-hop transmission protocol based on parallel communication of secondary users (SUs) is proposed. The primary multi-hop network coexists with a set of SUs by cooperative spectrum sharing. The main optimization target of our protocol is the overall performance of the secondary system with the guarantee of the primary outage performance. The energy consumption of the primary system is reduced by the cooperation of SUs. The aim of the primary source is to communicate with the primary destination via a number of primary relays. SUs may serve as extra decode-and-forward relays for the primary network. When an SU acts as a relay for a primary user (PU), some other SUs that satisfy the condition for parallel communication are selected to simultaneously access the primary spectrum for secondary transmissions. For the proposed protocol, two opportunistic routing strategies are proposed, and a search algorithm to select the SUs for parallel communication is described. The throughput of the SUs and the PU is illustrated. Numerical results demonstrate that the average throughput of the SUs is greatly improved, and the end-to-end throughput of the PU is slightly increased in the proposed protocol when there are more than seven SUs.

• Journal of the Korean Institute of Intelligent Systems
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• v.27 no.1
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• pp.1-6
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• 2017

Recent researches on radio frequency energy harvesting networks(RF-EHNs) with limited energy resource like battery have been focusing on the development of a new scheme that can effectively extend the whole lifetime of a network to semipermanent. In order for considerable increase both in the amount of energy obtained from radio frequency energy harvesting and its charging effectiveness, it is very important to design a network that supports energy harvesting and data transfer simultaneously with the full consideration of various characteristics affecting the performance of a RF-EHN. In this paper, we proposes an interference-based charging aware routing protocol(ICARP) that utilizes interference information and charging time to maximize the amount of energy harvesting and to minimize the end-to-end delay from a source to the given destination node. To accomplish the research objectives, this paper gives a design of ICARP adopting new network metrics such as interference information and charging time to minimize end-to-end delay in energy harvesting wireless networks. The proposed method enables a RF-EHN to reduce the number of packet losses and retransmissions significantly for better energy consumption. Finally, simulation results show that the network performance in the aspects of packet transmission rate and end-to-end delay has enhanced with the comparison of existing routing protocols.

• Proceedings of the Korean Information Science Society Conference
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• 2012.06d
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• pp.251-253
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• 2012

본 논문은 무선 센서 망의 실시간 데이터의 전달 확률 향상을 위한 기회적 실시간 데이터 전달 프로토콜을 제안한다. 기존에 재전송 기법은 데이터 전달 확률 향상을 위한 방법으로 잘 알려져 있으나, 이 기법은 딜레이를 발생시키기 때문에 실시간 데이터 전달에 적용하기는 적절치 않다. 이 문제를 해결하기 위해서 본 논문은 무선 망의 브로드캐스팅 방법과 순차적 기회 제공 방법을 동시에 사용한다. 하나의 센서 노드의 1-홉 내에는 실시간 요구사항을 만족하는 다수의 노드가 존재한다. 제안 방안에서는 실시간 요구사항을 만족하는 노드들에게 브로드캐스팅으로 데이터를 전달하고, 이 그룹에 속한 노드들에게 순차적으로 데이터를 중계할 기회를 제공한다. 제안 방안은 데이터를 빨리 처리할 수 있는 노드에게 먼저 기회를 제공하여 좀 더 많은 노드들이 데이터를 전송할 수 있는 기회를 갖게 함으로써 데이터 전달 확률을 높인다.

• Journal of Communications and Networks
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• v.10 no.2
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• pp.213-220
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• 2008

This paper analyzes a broadcasting technique for wireless multi-hop sensor networks that uses a form of cooperative diversity called opportunistic large arrays (OLAs). We propose a method for autonomous scheduling of the nodes, which limits the nodes that relay and saves as much as 32% of the transmit energy compared to other broadcast approaches, without requiring global positioning system (GPS), individual node addressing, or inter-node interaction. This energy-saving is a result of cross-layer interaction, in the sense that the medium access control (MAC) and routing functions are partially executed in the physical (PHY) layer. Our proposed method is called OLA with a transmission threshold (OLA-T), where a node compares its received power to a threshold to decide if it should forward. We also investigate OLA with variable threshold (OLA-VT), which optimizes the thresholds as a function of level. OLA-T and OLA-VT are compared with OLA broadcasting without a transmission threshold, each in their minimum energy configuration, using an analytical method under the orthogonal and continuum assumptions. The trade-off between the number of OLA levels (or hops) required to achieve successful network broadcast and transmission energy saved is investigated. The results based on the analytical assumptions are confirmed with Monte Carlo simulations.