• Journal of Korea Multimedia Society
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• v.10 no.12
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• pp.1645-1654
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• 2007

In this paper, we study the problem of load balancing routing in clustered-based wireless mesh network in order to enhance the overall network throughput. We first address the problems of cluster allocation in wireless mesh network to achieve load-balancing state. Due to the complexity of the problem, we proposed a simplified algorithm using gradient load-balancing model. This method searches for a localized optimal solution of cluster allocation instead of solving the optimal solution for overall network. To support for load-balancing algorithm and reduce complexity of topology control, we also introduce limited broadcasting between two clusters. This mechanism maintain shortest path between two nodes in adjacent clusters while minimizing the topology broadcasting complexity. The simulation experiments demonstrate that our proposed model achieve performance improvement in terms of network throughput in comparison with other clustering methods.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.3
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• pp.1406-1424
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• 2017

Recent advancements in network infrastructures provide increased opportunities to support data delivery over multiple paths. Compared with multi-homing scenario, overlay network is regarded as an effective way to construct multiple paths between end devices without any change on the underlying network. Exploiting multipath characteristics has been explored for TCP with multi-homing device, but the corresponding exploration with overlay network has not been studied in detail yet. Motivated by improving quality of experience (QoE) for reliable data delivery, we propose a multipath message transport protocol based on application level relay (MPMTP-AR). MPMTP-AR proposes mechanisms and algorithms to support basic operations of multipath transmission. Dynamic feedback provides a foundation to distribute reasonable load to each path. Common source decrease (CSD) takes the load weight of the path with congestion into consideration to adjust congestion window. MPMTP-AR uses two-level sending buffer to ensure independence between paths and utilizes two-level receiving buffer to improve queuing performance. Finally, the MPMTP-AR is implemented on the Linux platform and evaluated by comprehensive experiments.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.9A
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• pp.1075-1082
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• 2004

Wireless LAN is a rather mature communication technology connecting mobile terminals. IEEE 802.11 is a representative protocol among Wireless LAN technologies. The basic medium access control (MAC) mechanism of IEEE 802.11 is called distnbuted coordination function (DCF). DCF shows poor throughput and high drop rate as the number of stations and offered traffic load increase. In this paper we propose an effective mechanism using dynamic mimmum contention window(CWmin) in wireless LAN~ and show that performance improves via simulations. Proposed dynamic CWmin scheme exhibits superior performance as the number of stations and offered load grow. As, our proposed scheme is expected to be more effective in highly densed wireless LAN environment.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.7
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• pp.1565-1570
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• 2014

In networking communication, nodes and base station send data to each nodes and destination nodes. In this perspective, it is very important to determine the direction in which data sent to each nodes or destination nodes. Ad-hoc routing protocol is a standard routing protocol that determines how the packets sent to destination. Ad-hoc routing protocol includes protocols such as Ad-hoc On-demand Distance Vector (AODV) and Dynamic Source Routing (DSR). In our efficient proposed protocol based on small end-to-end sequence numbers, route direction can be changed properly with the assistance of helper nodes. In this paper, we focus on the simulation analysis of proposed protocol and comparison with other routing protocol models such as AODV and DSR. We simulated using Network Simulator (NS-2) by parameters such as simulation time, number of nodes and packet size based on our metrics (packet delivery fraction, routing load, data throughput). Our proposed protocol based on small end-to-end sequence numbers shows better performance and superior to other two protocols.

• The KIPS Transactions:PartC
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• v.11C no.7 s.96
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• pp.889-894
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• 2004

Most ad-hoc routing protocols such as AODV(Ad Hoc On-Demand Distance Vector) and DSR(Dynamic Source Routing) do not try to search for new routes if the network topology does not change. Hence, with low node mobility, traffic may be concentrated on several nodes, which results in long end-to-end delay due to congestion at the nodes. Furthermore, since some specific nodes are continuously used for long duration, their battery power may be rapidly exhausted. Expiration of nodes causes connections traversing the nodes to be disrupted and makes many routing requests be generated at the same time. Therefore, we propose a load balancing approach called Simple Load-balancing Approach (SLA), which resolves the traffic concentration problem by allowing each node to drop RREQ (Route Request Packet) or to give up packet forwarding depending on its own traffic load. Meanwhile, mobile nodes nay deliberately give up forwarding packets to save their own energy. To make nodes volunteer in packet forwarding. we also suggest a payment scheme called Protocol-Independent Fairness Algorithm (PIEA) for packet forwarding. To evaluate the performance of SLA, we compare two cases where AODV employs SLA or not. Simulation results show that SLA can distribute traffic load well and improve performance of entire ad-hoc networks.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.5
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• pp.1144-1150
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• 2015

Presence information provides various informations about users such as on-line status, current location, network connection method and connection address, and there are two kinds of presence information, SIP(Session Initiation Protocol) based presence information and XMPP(Extensible Massaging and Presence Protocol) based presence information. In this paper, a multiple server architecture that can handle these two kinds of presence information has been proposed. In this architecture, severs are added dynamically according to number of users to provide system scalability, and load of each server can be effectively controlled. In this system, a new XMPP stanza architecture and presence information data format are designed for load control. Furthermore message exchanging procedures between servers and users for dynamic server control has been also suggested. The performance of the proposed system has been analysed by simulation.

• Journal of Communications and Networks
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• v.14 no.1
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• pp.15-20
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• 2012

As Internet protocol and wireless communications have developed, the number of different types of mobile services has increased gradually. Existing priority-computing schemes cannot satisfy the dynamic requirements of supporting multiple services in future wireless communication systems, because the currently used factors, mainly user priority, are relatively simple and lack relevancy. To solve this problem and provide the desired complexity, dynamic behavior, and fairness features of 3G and beyond 3G mobile communication systems, this paper proposes a novel cross-layer dynamic integrated priority-computing scheme that computes the priority based on a variety of factors, including quality of service requirements, subscriber call types, waiting time, movement mode, and traffic load from the corresponding layers. It is observed from simulation results that the proposed dynamic integrated priority scheme provides enhanced performance.

• Proceedings of the IEEK Conference
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• 2002.07c
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• pp.1839-1842
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• 2002

Ad hoc networks are characterized by multi- hop wireless connectivity, frequently changing network topology and the need for efficient dynamic routing protocols. In this paper, we proposed a new technique to adjust the zone radius by concentrating the changes of network traffic in a particular direction, which we refer to as AZRP. We demonstrate that even though ZRP and AZRP share a similar hybrid routing behavior, the differences in the protocol mechanics can lead to significant performance differentials. We discuss the algorithm and report on the performance of AZRP scheme, and compare it to the ZRP routing protocol. Our results indicate clearly that AZRP outperforms ZRP by reducing significantly the number of route query messages. And thereby increases the efficiency of the network load.

• The KIPS Transactions:PartC
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• v.14C no.5
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• pp.417-424
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• 2007

Mesh networks using WLAN technology have been paid attention as a key wireless access technology. However, many technical issues still exist for its successful deployment. One of those issues is the routing problem that addresses the path setup through a WLAN mesh network for the data exchanges between a station and a wired network. Since the characteristics of a WLAN mesh network can be very dynamic, the use of single routing protocol would not fit for all environments whether it is reactive or proactive. Therefore, it is required to develop an adaptive routing protocol that modifies itself according to the changes in the network parameters. As a logical first step for the development, an analytical model considering all the dynamic features of a WLAN mesh network is required to evaluate the performance of a reactive and a proactive routing scheme. In this paper, we propose an analytical model that makes us scrutinize the impact of the network and station parameters on the performance of each routing protocol. Our model includes the size of a mesh network, the density of stations, mobility of stations. and the duration of network topology change. We applied our model to the AODV that is a representative reactive routing protocol and DSDV that is a representative proactive routing protocol to analyze the tradeoff between AODV and DSDV in dynamic network environments. Our model is expected to help developing an adaptive routing protocol for a WLAN mesh network.

• Journal of Korea Society of Industrial Information Systems
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• v.19 no.2
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• pp.1-13
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• 2014

In IEEE 802.11p/1609-based vehicular networks, vehicles are allowed to exchange safety and control messages only within time periods, called control channel (CCH) interval, which are scheduled periodically. Currently, the length of the CCH interval is set to the fixed value (i.e. 50ms). However, the fixed-length intervals cannot be effective for dynamically changing traffic load. Hence, some protocols have been recently proposed to support variable-length CCH intervals in order to improve channel utilization. In existing protocols, the CCH interval is subdivided into safety and non-safety intervals, and the length of each interval is dynamically adjusted to accommodate the estimated traffic load. However, they do not consider the presence of hidden nodes. Consequently, messages transmitted in each interval are likely to overlap with simultaneous transmissions (i.e. interference) from hidden nodes. Particularly, life-critical safety messages which are exchanged within the safety interval can be unreliably delivered due to such interference, which deteriorates QoS of safety applications such as cooperative collision warning. In this paper, we therefore propose a new interference-aware Dynamic Safety Interval (DSI) protocol. DSI calculates the number of vehicles sharing the channel with the consideration of hidden nodes. The safety interval is derived based on the measured number of vehicles. From simulation study using the ns-2, we verified that DSI outperforms the existing protocols in terms of various metrics such as broadcast delivery ration, collision probability and safety message delay.