• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.9B
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• pp.591-595
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• 2005

In this paper, we propose the fairness improvement leaky bucket (PILB) algorithm as a traffic policing mechanism. In the proposed algorithm, there is a cell buffer for every ATM connection in order to store date cells. Network decides whether an ATM connection obeys the contracted traffic parameter, and stores data cells in the cell buffer if the connection obeys but is considered as violated the contract due to temporary lack of network resource. By using the proposed algorithm, we can obtain the statistical multiplexing gain that is the superiority of packet switching network. Moreover, when a connection tries to transmit more data cells by violating the contracted traffic parameters, the connection is prevented from using excess network resource, which incurs all connections sharing network resource fairly. The performance of the proposed FILB algorithm is investigated by using the simulation. The result shows that the proposed algorithm provides superior performance and all connections within a group share network resource fairly. The proposed algorithm can be applied not only the ATM network but also IP network.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.4B
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• pp.397-402
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• 2004

In this paper, we have designed and simulated a new file transmission method. This method restricts memory copy and context switching happened in traditional file transmission. This method shows an improved performance than traditional method in network environment. When the UNIX/LINUX system that uses the existing file transfer technique transmits a packet to the remote system, a memory copy between the user and kernel space occurs over twice at least. Memory copy between the user and kernel space increase a file transmission time and the number of context switching. As a result, the existing file transfer technique has a problem of deteriorating the performance of file transmission. We propose a new algorithm for solving these problems. It doesn't perform memory copy between the user and kernel space. Hence, the number of memory copy and context switching is limited to the minimum. We have modified the network related source code of LINUX kernel 2.6.0 to analyzing the performance of proposed algorithm and implement new network system calls.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.3B
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• pp.161-167
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• 2007

In this paper, we evaluate the capacity of voice over internet protocol (VoIP) services over high-speed downlink packet access (HSDPA), in which frame-bundling (FB) is incorporated to reduce the effect of relatively large headers in the IP/UDP/RTP layers. Also, a modified proportional pair (PF) packet scheduler design supporting for VoIP service is provided. The main focus of this work is the effect of FB on system outage based on delay budget in radio access networks. Simulation results show that VoIP system performance with FB scheme is highly sensitive to delay budget. We also conclude that HSDPA is attractive for transmission of VoIP if compared to the circuit switched (CS) voice that is used in WCDMA (Release'99).

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.3
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• pp.86-94
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• 1990

This paper suggests a unified packet telecommunication network, which is designed by applying network design algorithm and distribution network design algorithm, Proposed local network design algorithm is based on MST topology, and it can satisfy the limited capacity and get a distribution effect of communication flow, With the result of the comparison with Kruskal and Esau-Willams algorithm, an increase of 2.7% in cost and a decrease of 44.8% in average delay time are shown. Starting with MST topology, proposed distribution network design algorithm gradually increases its reliability, and proposes a conclusive algorithm to determine a topology with minimum cost. In compared with Cut-Saturation algorithm in the aspect of end-to-end delay time and communication flow restricted condition, this proposed algorithm results in 1/7 cost down and about 2.5 times increases in Throughput.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.3
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• pp.46-52
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• 2008

BGP is an exterior routing protocol which exchanges routing information between ASs in ISP or large networks. It is necessary for the BGP to provide traffic enforcement among ASs, for an End-to-End traffic engineering capability in the Internet. However, traditional BGP-4 is lack of end-to-end traffic engineering capability because the policy-based routing affects the traffic only between directly-connected neighbor ASs. This paper proposes an extended BGP routing algorithm to achieve an End-to-End traffic engineering capability. This new method does not require an additional BGP message type, nor change a structure of existing routing table. It only extended the operation of UPDATE message with AS_PATH attribute, which is well-known mandatory. Simulation shows that the new BGP algorithm improves the packet delay and packet loss without the problem of backward compatibility.

• Journal of the Korea Society of Computer and Information
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• v.16 no.4
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• pp.101-110
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• 2011

A smart grid networks delivers electricity from suppliers to consumers using digital technology with two-way communications to control appliances at consumers' homes to save energy, reduce cost and increase reliability and transparency. Security is critically important for smart grid networks that are usually used for the electric power network and IT environments that are opened to attacks, such as, eavesdroping, replay attacks of abnormal messages, forgery of the messages to name a few. ZigBee has emerged as a strong contender for smart grid networks. ZigBee is used for low data rate and low power wireless network applications. To deploy smart grid networks, the collected information requires protection from an adversary over the network in many cases. The security mechanism should be provided for collecting the information over the network. However, the ZigBee protocol has some security weaknesses. In this paper, these weaknesses are discussed and a method to improve security aspect of the ZigBee protocol is presented along with a comparison of the message complexity of the proposed security protocol with that of the current ZigBee protocol.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39B no.2
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• pp.114-122
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• 2014

Beacon transmission is one of the fundamental mechanisms in vehicular ad hoc networks. Variety services including context awareness can be embodied by exchanging beacons in each vehicle. In this paper, we propose dual beacon transmission instead of traditional single beacon transmission for beaconing mechanism. dual beacon transmission divides beacon into two functions and operates two beaconing process independently. We verified the superiority of dual beacon transmission by comparing beacon packet delivery ratio with single beacon transmission. In conclusion, dual beacon transmission can reduce channel load and have both wider communication range and effective context awareness. In addition, implementing dual beacon transmission has less complexity and appliable with conventional adaptive beaconing schemes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37C no.11
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• pp.1112-1128
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• 2012

In cognitive radio networks, secondary users are allowed to utilize the channels currently not occupied by primary users opportunistically. Secondary users can communicate with each other using the commonly available channels (common channels) which may change dynamically based on the activity of the primary users. Even though many studies have dealt with cognitive radio behaviors, the detailed procedures for common channel configuration have not been paid much attention. In this paper, the fast and reliable dynamic common channel setup and reconstruction method for the point-to-point communications in military cognitive radio networks is proposed. The detailed time parameters are considered for common channel setup and reconstruction, such as the packet exchange time, channel request waiting time, and rendezvous time. Through numerical analyses, the delay and throughput performance of the proposed method is derived and evaluated.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37B no.12
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• pp.1174-1185
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• 2012

This paper proposes a call admission control scheme for delay guarantee in the wireless mesh networks. The admission of a new call is determined based on the expected delay inferred from the class level available bandwidth at nodes on the path. All nodes under the effects of the new call are considered in designing the call admission control scheme to maintain the delay guarantee of the pre-existing traffic. An effective technique for estimating the available bandwidth of the neighbor nodes is proposed with no addition of message interchanges. The class-level delay control is mainly performed by the queueing discipline while keeping the MAC operation simple. Simulations are performed to show the validity of the proposals. We observe acceptable performances in delay expectation with the addition of new calls. We also show that the proposed call admission control is helpful in guaranteeing the delay performances.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.1
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• pp.159-169
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• 1994

A multichannel optical slotted ring network is designed using a wavelength division multiplexing(WDM) technique and photonic packet switching devices. The electronics speed bottleneck is removed out of the ring, which allows utilization of the full bandwidth for the optical fiber transmission medium. The ring channel adopts a slotted ring concept with a destination cell remove strategy for the eing access mechanism. The slot size in the ring is selected as the same as that of ATM based cell in order to be used as B-ISDN Access Networks. In this paper, we devised a mathematical method to measure the average transfer delay characteristics of the network. The analytical method turned out to yield accurate results over a broad range of parameters in comparison to simulation results. From the study, we observed the average transfer delay of the network as the network parameters vary.