• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.12
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• pp.149-158
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• 2005

This paper proposes a congestion avoidance algorithm which provides stable throughput and transmission rate regardless of buffer size by limiting the TCP congestion window in fixed bandwidth networks. Additive Increase, Multiplicative Decrease (AIMD) is the most commonly used congestion control algorithm. But, the AIMD-based TCP congestion control method causes unnecessary packet losses and retransmissions from the congestion window increment for available bandwidth verification when used in fixed bandwidth networks. In addition, the saw tooth variation of TCP throughput is inappropriate to be adopted for the applications that require low bandwidth variation. We present an algorithm in which congestion window can be limited under appropriate circumstances to avoid congestion losses while still addressing fairness issues. The maximum congestion window is determined from delay information to avoid queueing at the bottleneck node, hence stabilizes the throughput and the transmission rate of the connection without buffer and window control process. Simulations have performed to verify compatibility, steady state throughput, steady state packet loss count, and the variance of congestion window. The proposed algorithm can be easily adopted to the sender and is easy to deploy avoiding changes in network routers and user programs. The proposed algorithm can be applied to enhance the performance of the high-speed access network which is one of the fixed bandwidth networks.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.1
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• pp.35-40
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• 2011

In this paper, we compare and analyze data aggregation methods based on event area in wireless sensor networks. Data aggregation methods consist of two methods: the direct transmission method and the aggregation node method. The direct aggregation method has some problems that are data redundancy and increasing network traffic as all nodes transmit own data to neighbor nodes regardless of same data. On the other hand the aggregation node method which aggregate neighbor's data can prevent the data redundancy and reduce the data. This method is based on location of nodes. This means that the aggregation node can be selected the nearest node from a sink or the centered node of event area. So, we describe the benefits of data aggregation methods that make up for the weak points of direct data dissemination of sensor nodes. We measure energy consumption of the existing ways on data aggregation selection by increasing event area. To achieve this, we calculated the distance between an event node and the aggregation node and the distance between the aggregation node and a sink node. And we defined the equations for distance. Using these equations with energy model for sensor networks, we could find the energy consumption of each method.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.7 no.6
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• pp.92-100
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• 2008

Ad-hoc network is a collection of wireless mobile hosts forming a temporary network without the aid of any centralized administration or reliable support services such as wired network and base stations. Recently, Ad-hoc networks are evolving to support multimedia contents according to expansion of ad hoc multi-hop communication system. Wireless ad-hoc network is different from the conventional wired network by frequent changes in network topology, number of routers and resources, there are a number of problems in applying conventional routing protocol to ad-hoc network. The AODV routing protocol is proposed for mobile node in ad-hoc networks. AODV protocol that provides to guarantee QoS for data transmission in ad hoc networks that link break frequently occurs. In this paper, AODV routing protocol based NDIS(Network Driver Interface Specification) is implemented. We design high performance image transmission that can operate with software(AODV) for ad-hoc networks without degradation. and verify operation of AODV routing protocol on the test bed.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.6
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• pp.21-28
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• 2016

This paper presents a cooperative transmission scheme for underwater acoustic sensor networks to improve packet transmission rate and reduce energy consumption. Source node transmits duplicated information relayed by distributed antennas called a virtual antenna array. Destination node combines that information to reduce packet error rate. The suggested cooperative scheme enhances the reliability by providing high diversity gains through intermediate relay nodes to overcome the distinct characteristics of the underwater channel, such as high transmission loss, propagation delay, and ambient noises. It is suggested that the algorithm select destinations and potential relays from a set of neighboring nodes that utilize distance cost, the residual energy of each node and local measurement of the channel conditions into calculation. Simulation results show that the proposed scheme reduces average energy consumption, response time, and increases packet delivery ratio compared with the SPF(Shortest Path First) and non-cooperative scheme using OPNET Moduler.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.1
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• pp.177-182
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• 2014

In this paper, we propose an energy efficient sink node based MAC protocol for Wireless Sensor Networks (WSNs). The proposed sink node-based MAC (SB-MAC) protocol uses a RB(rapid beacon) frame to save sender's energy consumption and to reduce transmission delay. The RB frame is a modified IEEE 802.15.4 beacon frame. The RB frame contains the length of the sender nodes data. Using this information other nodes except sender and receiver nodes can be stay sleep mode long time to reduce energy consumption. Results have shown that the SB-MAC protocol outperformed other protocols like X-MAC and RI-MAC in terms of packet delivery delay and energy consumption. The SB-MAC protocol is especially energy efficient for the networks with one sink node and many senders.

• Journal of Digital Contents Society
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• v.8 no.3
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• pp.323-328
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• 2007

Communication systems beyond 3G should provide more than 100 Mbps for wireless access. In addition to smart antennas, wireless multi-hop networks are proposed to increase the cell size and throughput. For example, Zigbee technology is expected to provide low cost and low power connectivity and can be implemented in wireless mesh networks larger than is possible with Bluetooth. Also, home embedded system using wireless mesh network is one of the key market areas for Zigbee applications. If the line-of-sight path is shadowed by home obstacles, a direct connection between the access point (AP) and the node is not possible at high frequencies. Therefore, by using multi-hop relay scheme the end node can be reached to AP. In this paper, the relaying of data between the AP and the end node is investigated and the throughput and PER(Packet Error Rate) are evaluated in multi-hop wireless mesh networks by using DSSS/BPSK system.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.2
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• pp.700-713
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• 2015

It is critical to design energy-efficient routing protocols for battery-limited mobile ad hoc networks, especially in which the energy-consuming MIMO techniques are employed. However, there are several challenges in such a design: first, it is difficult to characterize the energy consumption of a MIMO-based link; second, without a careful design, the broadcasted RREP packets, which are used in most energy-efficient routing protocols, could flood over the networks, and the destination node cannot decide when to reply the communication request; third, due to node mobility and persistent channel degradation, the selected route paths would break down frequently and hence the protocol overhead is increased further. To address these issues, in this paper, a novel Greedy Energy-Efficient Routing (GEER) protocol is proposed: (a) a generalized energy consumption model for the MIMO-based link, considering the trade-off between multiplexing and diversity gains, is derived to minimize link energy consumption and obtain the optimal transmit model; (b) a simple greedy route discovery algorithm and a novel adaptive reply strategy are adopted to speed up path setup with a reduced establishment overhead; (c) a lightweight route maintenance mechanism is introduced to adaptively rebuild the broken links. Extensive simulation results show that, in comparison with the conventional solutions, the proposed GEER protocol can significantly reduce the energy consumption by up to 68.74%.

• Journal of Internet Computing and Services
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• v.8 no.5
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• pp.21-33
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• 2007

An overlay network is a virtual network which is constructed on top of a physical computer network. A node in the overlay network is connected through virtual or logical links, where each link corresponds to a path of the links in the underlying physical network. Overlay networks are suitable for sharing heterogeneous resources in distributed environments, However, overlay networks are limited for achieving reliable communication that failure detection in overlay networks is a very important issue. In this paper, we review conditions of conventional failure detection and propose a new approach to failure detection and resilience which can be applied to HRing (Hierarchical Ring) overlay networks. The proposed method consists of the failure detection and the failure resilience phases. Because it utilizes the characteristics of the HRing overlay network for failure detection, it can reduce unnecessary network traffic and provide better scalability and flexibility. We also analyzed and evaluated the performance of the proposed approach through simulations.

• The KIPS Transactions:PartC
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• v.8C no.1
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• pp.88-96
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• 2001

Future mobile communication networks, which consist of ATM-based B-ISDN backbone networks and wireless ATM networks, will provide u user with broadband connection and QoS service. These network systems need the lossless handoff methods which support user mobility, satisfy ATM features such as ATM cell ordering and no ATM cell duplication and minimize buffer requirement for ATM cell buffering. In this paper we suggest a multicast-based handoff method to supp$\alpha$t lossless connection as well as to minimize buffer overhead. It establishes a dynamic multicast connection between source terminal and wireless member AP (access point)s. When the mobile terminal receives data packet correctly, it notifies the positive acknowledgement of the packet to all member APs. And member APs then release the MT related temporary buffer space for MT's future movement. Therefore member APs can eliminate unnecessary buffer usage and manage the buffer space efficiently. Analysis result shows that our handoff method has better performance in buffer requirement for lossless and seamless connection services over VCT (virtual connection tree) method and other dynamic multicast-based handoff methods.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.3
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• pp.537-548
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• 2000

ATM is the effective information transmission method which multiply statistical and can accept effective the traffic of the various transmission rate. However, it can happen excessive cell loss probability and cell delay when it have temporarily overload. Therefore, it is required the effective traffic control and network resource management for which guarantee QoS(Quality of Service) in terms of users and bandwidth utilization maximization in terms of networks. In this paper, we proposed POBP(PushOut BP) scheme which mixed pushout scheme with BP(Back Pressure), reactive control scheme recommended at the ATM Forum, to guarantee QoS in two stages ATM switch networks. In proposed method, we have to understand exactly using bandwidth information in real-time and become traffic shaping. Thorough these processes, we can not only use effectively unused bandwidth, but also guarantee the fair bandwidth utilization and then can improve cell-loss possibility happened by congestion states in two stage ATM networks.