• ETRI Journal
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• v.24 no.1
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• pp.43-55
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• 2002

This paper proposes a flow-based admission control algorithm through an Asynchronous Transfer Mode (ATM) based Multi-Protocol Label Switching (MPLS) network for multiple service class environments of Integrated Service (IntServ) and Differentiated Service (DiffServ). We propose the Integrated Packet Scheduler to accommodate IntServ and Best Effort traffic through the DiffServ-aware MPLS core network. The numerical results of the proposed algorithm achieve reliable delay-bounded Quality of Service (QoS) performance and reduce the blocking probability of high priority service in the DiffServ model. We show the performance behaviors of IntServ traffic negotiated by end users when their packets are delivered through the DiffServ-aware MPLS core network. We also show that ATM shortcut connections are well tuned with guaranteed QoS service. We validate the proposed method by numerical analysis of its performance in such areas as throughput, end-to-end delay and path utilization.

• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.445-450
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• 2018

Reliable detection and parameter estimation of a radar cross section(RCS) fluctuating target have been known as a difficult task. To reduce the effect of RCS fluctuation, various diversity techniques have been considered. This paper presents a new method for synthesizing a covariance matrix applicable to a coherent multi-input multi-output(MIMO) radar with frequency diversity. It is achieved by efficiently combining covariance matrices corresponding to different carrier frequencies such that the signal-to-noise ratio(SNR) in the combined covariance matrix is maximized. The value of a synthesized covariance matrix is assessed by examining the phase curves of its entries and the improvement on direction of arrival(DOA) estimation.

• Journal of information and communication convergence engineering
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• v.10 no.2
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• pp.129-134
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• 2012

As application-specific requirements for wireless sensor networks emerge, both real-time and reliable communications become major research challenges in wireless sensor networks due to the many constraints on nodes and wireless links. To support these services, several protocols have been proposed. However, since most of them were designed as well as developed for general purpose applications, it is not recommended that they be directly adapted to applications with special requirements. In this paper, we propose a way to extend the current reliable transport protocol to cover a special real-time service, the (m,k)-firm deadline stream, in wireless sensor networks. While the proposed scheme is basically built on the PSFQ protocol for reliability, some features have been newly developed to support the (m,k)-firm stream efficiently. Finally, simulation results are given to demonstrate the feasibility of the proposed scheme in high traffic and with failed links.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.8 no.4
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• pp.201-206
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• 2009

The third generation mobile communications system requiring the reliable multimedia data transmission has provided with the reliable voice, data and video services over the variable propagation environment. However the broadband wireless multiple access technologies cause Inter Symbol Interference (ISI) or Multiple Access Interference (MAI) to degrade the performance of W-CDMA (Code Division Multiple Access) system. Constant Modulus Algorithm (CMA) which is frequently used as the adaptive blind equalizers to remove the interfering signal has ill-convergence phenomenon without proper initialization. In this paper, new blind equalization method based on conventional CMA is proposed to improve the channel efficiency, and through computer simulation this is tested over the time varying fading environment of mobile communication system. Consequently, new blind equalization method into concatenated Kalman filter with CMA is verified better than conventional CMA through adopting minimum mean square errors and eye-pattern obtained from algorithm are compared.

• Journal of Communications and Networks
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• v.18 no.2
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• pp.246-260
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• 2016

A major challenge achieving scalable access control for a large number of subscribers in a public broadcast is to distribute key update messages reliably to all stateless receivers. However, in a public broadcast, the rekeying messages can be dropped or compromised during transmission over an insecure broadcast channel, or transmitted to receivers while they were off-line. In this study, we propose a novel group key management scheme. It features a mechanism to allow legitimate receivers to recover the current group key, even if they lose key update messages for long-term sessions. The scheme uses short hint messages and member computation. Performance analysis shows that the proposed scheme has the advantages of scalability and efficient rekeying compared to previous reliable group key distribution schemes. The proposed key management scheme targets a conditional access system in a media broadcast in which there is no feedback channel from receivers to the broadcasting station.

• Journal of Communications and Networks
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• v.11 no.3
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• pp.306-317
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• 2009

We consider the problem of architecting a reliable content delivery system across an overlay network using TCP connections as the transport primitive. We first argue that natural designs based on store-and-forward principles that tightly couple TCP connections at intermediate end-systems impose fundamental performance limitations, such as dragging down all transfer rates in the system to the rate of the slowest receiver. In contrast, the ROMA architecture we propose incorporates the use of loosely coupled TCP connections together with fast forward error correction techniques to deliver a scalable solution that better accommodates a set of heterogeneous receivers. The methods we develop establish chains of TCP connections, whose expected performance we analyze through equation-based methods. We validate our analytical findings and evaluate the performance of our ROMA architecture using a prototype implementation via extensive Internet experimentation across the PlanetLab distributed testbed.

• Electronics and Telecommunications Trends
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• v.34 no.3
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• pp.93-105
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• 2019

This study emphasizes the importance of the newly added Ultra-Reliable and Low-Latency Communications (URLLC) service as an important evolutionary step for 5G mobile communication, and proposes a remedial application. We analyze the requirements for the application of 5G mobile communication technology in high-precision vertical industries and applications, introduce the 5G URLLC design principles and standards of 3GPP, and summarize the current state of applied artificial intelligence technology in wireless communication. Additionally, we summarize the current state of research on ultra-reliable and low-latency machine learning-based wireless communication technology for application in ultra-high-precision vertical industries and applications. Furthermore, we discuss the technological direction of artificial intelligence technology for URLLC wireless communication.

• 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.

• KIPS Transactions on Computer and Communication Systems
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• v.2 no.6
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• pp.253-256
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• 2013

For the reliable delivery of safety-related information to vehicles in the VANET, a reliable VANET routing protocol is required. In this paper, we propose a routing protocol that works based on the road vehicle density information for fast and reliable communications among vehicles within the city environment VANET. In the proposed mechanism, each vehicle computes the road vehicle density by using beacon messages and the road information. Based on the road vehicle density information, each vehicle establishes a reliable route for packet delivery. Through the NS-2 based simulations, we compare our proposed mechanism with GPSR and show that our mechanism outperforms GPSR in terms of packet delivery success rate.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.12C
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• pp.1123-1130
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• 2009

The advances in networking technology and importance of multimedia communication require real time transaction. In many applications, high reliable real-time communications are required more frequently. In this paper, we propose a reliable communication in cube-based multi -computer using the safety vector. Each node in a cube-based n dimensional multi-computer is associated with a safety vector of n bits, which is an approximated measure of the number and distribution of faults in the neighborhood. We propose an algorithm that can establish detour paths using the safety vector. The established detour paths are disjoint with the primary real-time channel. Therefore, our algorithm is more efficient than earlier proposed algorithms.