• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.10
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• pp.29-34
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• 2011

We present a network coding scheme which is designed for improving throughput in multi-hop wireless network with multi-radio multi-channel. The co-channel interference and unreliability of wireless transmissions cause the wireless network to reduce throughput. In wireless network, multi-radio multi-channel technology shows benefit to cut down channel interferences and contentions. And network coding can reduce the complexity of scheduling and improve throughput by increasing usage of links in wireless network. In this paper, we propose a method of channel assignment and transmission scheduling in intra-session network coding that efficiently improve throughput for multi-hop wireless network by using mathematical modeling and linear programming. Moreover, we evaluate the performance of the intra-session network coding scheme by using AMPL with CPLEX. The simulation results show that intra-session network coding can achieve better throughput than traditional routing.

• Journal of Korea Society of Industrial Information Systems
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• v.25 no.1
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• pp.1-11
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• 2020

Wireless sensor networks consist of a large number of tiny sensor nodes which have limited battery life. In order to maximize the network life span, we propose an optimal transmission radius, R, for control messages. We analyze the transmission radius as a function of the energy consumption of cluster head nodes and the energy consumption of member nodes to find the optimal value of R. In simulations we apply our proposed optimization of transmission range to LEACH-based single-hop and multi-hop networks to show that our proposed scheme outperforms other existing routing algorithms in terms of network life span.

• Journal of Information Technology Services
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• v.11 no.4
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• pp.195-213
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• 2012

In ubiquitous environments, the Intelligent Transportation System (ITS) protocol is a typical service used to improve the quality of life for humans. The Vehicular Ad-hoc Network (VANET) protocol, a part of ITS, needs further study with regards to its support for high reliability, high speed mobility, data transmission efficiency, and so on. The IEEE 802.11 standard provides a high data rate channel, but it was designed for peer-to-peer network protocols. IEEE 802.11p also provides a high data rate channel, however, it only facilitates communication between roadside and on-board equipment. A VANET has characteristics that enable its topology to change rapidly; it can also be expanded to a multi-hop range network during communication. Therefore, the VANET protocol needs a way to infer the current topology information relating to VANET equipped vehicles. In this paper, we present the Multi-Beacon MAC Protocol, and propose a method to resolve the problem of beacon collisions in VANET through the use of this Multi-Beacon MAC protocol. Evaluation of the performance of Multi-Beacon MAC protocol by means of both mathematical analyses and simulation experiments indicate that the proposed method can effectively reduce beacon collisions and improve the throughput and the delay between vehicles in VANET systems.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.8
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• pp.1098-1104
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• 2011

Data communications networks at sea can be modelled by multi-layered networks with traditional carriers (RF, satellites), and BWA (wireless LAN, WiBro, LTE), which partially makes it possible the high speed communication services (WWW, VoIP) at sea. In this paper, a novel routing scheme (CPR) is proposed which selects an optimal carrier for each hop in routes based on carrier preferences (CP). The carrier preferences are measured proactively depending on the feasibility of transmission characteristics (transmission rate, cost, and latency time) of the carriers for each application. Performance was compared with that of the OMH-MW (Optimal Medium per Hop based on Max-Win) routing scheme.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37B no.9
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• pp.723-733
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• 2012

In wireless ad hoc networks, packet loss and latency are frequently occurred by movement of node. As the number of transmission hops increases in these networks, the throughput is increasingly deteriorated. In this paper, we design the wireless ad hoc network system based on IEEE 802.16j MMR (Mobile Multi-hop Relay), which improves the network performance. Our wireless ad hoc network system used adaptively the nearest BS and Farthest BS scheduling algorithms for efficient data transmission and chose the optimal path that minimize data loss and latency. In order to evaluate performance of the wireless ad hoc network system based on IEEE 802.16j MMR, we used the LWX (Light Wimax) model of NS-2 simulator. Through the simulation, we analyzed the network performance for various scenarios.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.11
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• pp.3218-3226
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• 2009

A number of on-demand routing protocols for sensor networks have been proposed yet. However, the majority of proposed on-demand routing protocols for sensor networks are not suitable for a relatively poor wireless environment and sensor applications requiring reliable data transmission due to using a hop-count metric for their protocols. In this paper, we proposed a minimum LQI(Link Quality Indicator) based on-demand sensor network routing protocol that is suitable for a relatively poor wireless environment and implemented the proposed routing protocol on a TinyOS. We also compared the implemented protocol with typical hop count based routing protocol by carrying out performance experiments on a multi-hop testbed. The results from these experiments showed that the successful transmission rate of the proposed routing protocol is higher than that of typical hop count based routing protocol over a poor wireless link.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.5
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• pp.21-26
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• 2012

Intra-session network coding has been proposed to improve throughput by simplifying scheduling of multi-hop wireless network and efficiency of packet transmission. Multi-rate transmission has been used in multihop wireless networks. An opportunistic routing with multirate shows throughput improvement compared with single rate. In this paper, we propose a method of throughput improvement in multi-hop wireless network by using multi-rate and intra-session network coding. We suggest a method to select an local optimal transmission rate at each node. The maximum throughput is evaluated by using linear programming (LP). To solve the LP, we use MATLAB and lp_solve IDE program. The performance evaluation results show that end-to-end throughput is improved by using multirate and intra-session network coding can achieve better throughput than opportunistic routing.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.8A
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• pp.813-819
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• 2007

In this paper, the effect of a propagation delay resulting from the use of an OFDM-based cellular system with a transparent mobile multi-hop relay(MMR) is initially analyzed. Then, channel estimation techniques, a least square(LS) method and a minimum mean square error(MMSE) method, for the OFDM systems with throughput enhancement(TE) MMR or cooperative MMR are proposed. The proposed channel estimation techniques can overcome the performance degradation caused by the propagation delay in TE MMR or cooperative MMR systems. It is demonstrated by computer simulation that the proposed channel estimation techniques for OFDM systems with transparent MMR are superior to the conventional techniques in terms of mean square error(MSE) and bit error rate(BER).

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.5B
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• pp.455-462
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• 2009

In this paper, we propose a buffer management scheme for decreasing the packet loss due to buffer overflow and improving the packet fairness between nodes in IEEE 802.11 based multi-hop mesh networks. In the proposed scheme, each mesh router that is an intermediate node receives fairly packet sent from neighboring mesh routers and mobile nodes, and it improves the reception ratio of multi-hop traffic of neighboring mesh routers. Therefore, the proposed scheme can reduce transmission delay and energy consumption. In order to improving the packet loss and the packet fairness, the proposed scheme uses the modified RTS/CTS under the IEEE 802.11 MAC protocol and reduces the packet loss by recognizing the packet size to send to the destination in advance. By using the simulation, we evaluated the proposed scheme in terms of the packet loss ratio and the number of received packet in each mesh router, and compare it to a traditional scheme.

• 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.