• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.8 no.1
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• pp.102-109
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• 2009

This paper proposes the efficient method of CSMA during an idle duration in the time slot. The hybrid TDMA/CSMA protocol is the method that shares the medium efficiently. This improves the channel efficiency and throughput by using CSMA method during the idle TDMA time slot. In CSMA duration, many devices start to compete with each other. This causes a low throughput because of a long delay and a frequent collision. In order to improve this problem, the proposed method reduces the number of devices that compete in the CSMA duration. Because the number of competed device is reduced, this proposed algorithm reduces the delay and collision probability. This decrements of delay and collision probability improve the networks. The simulation results show that the proposed limitive CSMA methods outperform any methods of hybrid TDMA/CSMA protocol.

• Journal of Digital Convergence
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• v.10 no.8
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• pp.179-184
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• 2012

A car accident on a highway occurs a chain-reaction collision because of a vehicle's fast velocity. In order to prevent it, the accident vehicle should broadcast a safe message to its neighbors. If there are many neighbor nodes, a frame collision probability is high. To solve this, it was proposed for a system as a previous study to send a safe message without frame-collision using separating channels. However, the separation of multiple channels make feasibility low because of increasing hardware's development cost and complexity. In this paper, we proposes a TDMA-based MAC protocol using a single channel. As a result, we show the frame reception success rate of our protocol was almost the same as the previous protocol.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37B no.10
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• pp.859-876
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• 2012

Since the existing protocols separated mobility management part and routing protocol part in their design and used a flooding, they suffer from the high control overhead, thereby limiting performance. In this paper, we use a tree-based mobility management method and present a simple and efficient routing protocol that exploits the topology information which is built additionally through mobility management. Thus, the mobility management and the routing protocol closely cooperate to optimize control overhead. Furthermore, we use a progressive path discovery method to alleviate traffic congestion around IG and a unicast-based broadcast method to increase the reliability of message delivery and to judge link validity promptly. The proposed protocol reduces control overhead greatly and works in a stable manner even with the large number of nodes and high mobility. This was proven by comparing with the AODV protocol that employs the hybrid mobility management protocol.

• Proceedings of the Korean Information Science Society Conference
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• 2002.04a
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• pp.193-195
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• 2002

본 논문에서는 최근에 제안된 Hybrid 방식의 모바일 멀티캐스트 프로토콜 중 MOM, MMA, RBMOM, 그리고 TBMOM 프로토콜에 대해서 여러 가지 관점에서 성능을 비교하여 각 프로토콜의 장단점을 분석함과 동시에, 이들 방식이 공통적으로 가지는 DMSP(Designated Multicast Service Provider) 핸드오프 문제에 대해서 Smooth DMSP 핸드오프방식을 제안한다.

• Journal of Advanced Navigation Technology
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• v.15 no.2
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• pp.204-212
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• 2011

Mobile P2P(Peer-to-Peer) protocols in MANET(mobile ad-hoc networks) have gained much attention recently. Existing P2P protocols can be categorized into structured and unstructured ones. In MANET, structured P2P protocols show large control traffic because they does not consider the locality of P2P data and unstructured P2P protocols have a scalability problem with respect to the number of nodes. Hybrid P2P protocols combine advantages of the structured and unstructured P2P protocols. Cluster-based P2P protocol is one of the hybrid P2P protocols. Our study makes an analysis of the cluster-based P2P protocol and derives the optimal cluster formation in MANET. In the derived optimal cluster formation, the cluster-based P2P protocol shows better performance than Gnutella protocol with respect to control traffic.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.10
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• pp.1862-1872
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• 2017

To overcome the limitations of the current Central Mobility Management (CMM) protocols, IETF has been discussing about the Distributed Mobility Management (DMM) protocols that the centralized mobility functions of Home Agents (HA) are distributed to network edges closer to mobile users. The DMM protocol has some advantages of low-cost traffic delivery and high scalability. However, it faces several problems such as a high signaling cost and a complex address management. Especially, users moving at a high speed and with long-live sessions can make these problems worse. To reduce the high signaling cost for long-live sessions, we propose a novel hybrid DMM protocol allocating different mobility anchors according to the session durations. In this paper, we analyze the performance of the proposed hybrid DMM protocol and show superior performance with respect to the signaling cost.

• Journal of Broadcast Engineering
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• v.24 no.2
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• pp.299-305
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• 2019

In ISO MPEG, MPEG-H has been standardized to smoothly deliver huge volume of ultra-high resolution videos over heterogeneous network environments for the consumers. In the MPEG-H standard, MMT(MPEG Media Transport) protocol is the next generation MPEG media transport technology to provide hybrid media delivery over heterogeneous environments. It is important to sustain accurate media synchronization to provide ultra-high resolution video services over heterogeneous network environments. In this paper, we propose and verify an in-band media synchronization scheme to circumvent the problem of additional session setup and excessive traffic problems of the conventional out-of-band media synchronization supported by the MMT technology.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.34S no.5
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• pp.25-34
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• 1997

Relatively slow tuning speed of optical device causes the unwanted delay in high speed single-hop multiwavelength networks. To lessen the overhead, we present a channel access protocol with dynamjic message scheduling. Th eframe structure of proposed protocol adopts hybrid multiaccess scheme in which WDMA is used as a basic multiaccess technique and TDMA is used to provide subchannels within a wavelength band. This architecture has two merits : the network extention is not limited by available number of wavelengths, and the transmission delay caused by optical device tuning time can to minimize the number of tunings. It schedules messages that require same wavelength channels sequencely, so the total transmission delay is reduced by decreasement of wavelength changes. The performance of proposed protocol is evaluated through numerical analysis based on probability and queueing theory. The peformance of proposed protocol is evaluated through numerical analysis based on probability and queueing theory. The numeric results show that the peformance of proposed protocol is better than that of previous one.

• IEMEK Journal of Embedded Systems and Applications
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• v.6 no.6
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• pp.335-344
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• 2011

The Tire Pressure Monitoring System(TPMS) is often used recently. However, the standards and functions are very different. Even though the regulation requires all vehicles install the TPMS, there is no a standard of a Physical and Media access control protocol which provides compatibility with other systems. In this paper, we propose a MAC protocol based on the international standard and an energy efficient hybrid RF system platform. The MAC protocol provides compatibility of the TPMS with other systems and the RF system platform reduces energy consumption significantly.

• Journal of Communications and Networks
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• v.18 no.4
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• pp.559-566
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• 2016

Software defined network (SDN) can effectively improve the performance of traffic engineering and will be widely used in backbone networks. Therefore, new energy-saving schemes must take SDN into consideration; this action is extremely important owing to the rapidly increasing energy consumption in telecom and Internet service provider (ISP) networks. Meanwhile, the introduction of SDN in current networks must be incremental in most cases, for technical and economic reasons. During this period, operators must manage hybrid networks in which SDN and traditional protocols coexist. In this study, we investigate the energy-efficient traffic engineering problem in hybrid SDN/Internet protocol (IP) networks. First, we formulate the mathematical optimization model considering the SDN/IP hybrid routing mode. The problem is NP-hard; therefore, we propose a fast heuristic algorithm named hybrid energy-aware traffic engineering (HEATE) as a solution. In our proposed HEATE algorithm, the IP routers perform shortest-path routing by using distributed open shortest path first (OSPF) link weight optimization. The SDNs perform multipath routing with traffic-flow splitting managed by the global SDN controller. The HEATE algorithm determines the optimal setting for the OSPF link weight and the splitting ratio of SDNs. Thus, the traffic flow is aggregated onto partial links, and the underutilized links can be turned off to save energy. Based on computer simulation results, we demonstrate that our algorithm achieves a significant improvement in energy efficiency in hybrid SDN/IP networks.