• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.3
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• pp.1333-1343
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• 2016

Spectrum sharing in centrally controlled cognitive radio (CR) networks has been widely studied, however, research on channel access for distributively controlled individual cognitive users has not been fully characterized. This paper conducts an analysis of random channel access of cognitive users controlled in a distributed manner in a CR network. Based on the proposed estimation method, each cognitive user can estimate the current channel condition by using its own Markov-chain model and can compute its own blocking probability, collision probability, and forced termination probability. Using the proposed scheme, CR with distributed control (CR-DC), CR devices can make self-controlled decisions based on the status estimations to adaptively control its system parameters to communicate better.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.4
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• pp.17-24
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• 2004

Call blocking probabilities of streaming data service in CDMA system with access point(AP) of WLAN are analyzed for different cell geometry of base station and AP and queuing is modeled. The considered system leads to successful handoffs between the APs of WLAN. Blocking probabilities are enumerated as a function for ratio of base station and AP sizes, their locations and the number of buffer in the queue. Results show that blocking probability is not influenced by base station and AP locations but mainly by ratio of their sizes. For CDMA system of radius 100m, 5 buffers in the queue and 7㏈ noise rise(NR), in order to obtain 1% call blocking probability, a cell with hot spot of radius 20m has more 0.6Erlang than that of radius 60m.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.10
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• pp.6310-6316
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• 2014

The increase in the Internet and smart device users requires high-level network security. Network security consists of Web Firewall, Network Firewall, IPS, DDoS system, UTM (Unified Treat Management), VPN, NAC (Network Access Control), Wireless security, Mobile security, and Virtualization. Most network security solutions running on IPv4, and IPv6 network services are not sufficiently ready. Therefore, in this paper, this study designed and implemented important functions of Network Access Control (NAC), which include IPv6 host detection, isolation, blocking and domain assignment for the IPv6 network. In particular, domain assignment function makes 128 bits IPv6 address management easy. This system was implemented on a KISA IPv6 test-bed using well known devices. Finally, the test result showed that all IPv6 based wired and wireless devices were well-controlled (detection, blocking, isolation and domain assignment).

• Journal of applied mathematics & informatics
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• v.33 no.1_2
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• pp.211-217
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• 2015

A dynamic spectrum access scheme with channel partitioning for secondary handover calls in cognitive radio networks is proposed to reduce forced termination probability due to spectrum handover failure. A continuous-time Markov chain method for evaluating its performance such as blocking probability, forced termination probability, and throughput is presented. Numerical and simulation results are provided to demonstrate the effectiveness of the proposed scheme with channel partitioning.

• The Transactions of the Korea Information Processing Society
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• v.6 no.11
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• pp.3131-3139
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• 1999

Satisfying the rigid timing requirements of various real-time activities in real-time systems often requires some special methods to tune the systems run-time behaviors. Unbounded blocking can be caused when a high priority activity cannot preempt a low priority activity. In such situation, it is said that a priority inversion has occurred. The priority inversion is one of the problems which may prevent threads from meeting the deadlines in the real-time systems. It is difficult to remove such priority inversion problems in the kernel at the same time to bound the worst case blocking time for the threads. A thread is a piece of executable code which has access to data and stack. In this paper, a new real-time systems. It is difficult to remove such priority inversion problems in the kernel at the same time to bound the worst case blocking time for the threads. A threads is a piece of executable code which has access to data and stack. In this paper, a new real-time server model, which minimizes the duration of priority inversion, is proposed to reduce the priority inversion problem. The proposed server model provides a framework for building a better server structure, which can not only minimize the duration of the priority inversion, but also reduce the deadline miss ratio of higher priority threads.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.8B
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• pp.730-738
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• 2004

In this paper, System performance parameters such as throughput, blocking probability and delay have been analyzed and expressed as a function of demanding traffic and service termination, probability, and we centers our discussion at particular downlink port of satellite switch which is capable of switching the individual spot beam and processing the information signals in the packet satellite communications with demand assigned multiple access technique. Delay versus throughput as a function of traffic parameters with several service termination probability can be derived via mathematical formulation and the relative differences of transmission delay is also compared.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.7
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• pp.1250-1256
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• 2001

A resource management scheme for ad hoc wireless local area networks (AWLAN's) is presented. This scheme combines distributed resource management scheme and orthogonal frequency division multiplexing-code division multiple access(OFDM-CDMA) technique to support multimedia services with QoS guarantees. The performance evaluation has done in terms of blocking rates and QoS loss probability.

• The KIPS Transactions:PartA
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• v.8A no.4
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• pp.385-390
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• 2001

In this paper, we describe a blocking method of buffer overflow attack for secure operating system. Our team developed secure operating system using MAC and ACL access control added on Linux kernel. We describe secure operating system (SecuROS) and standardized Secure utility and library. A working prototype able to detect and block buffer overflow attack is available.

• Journal of the Institute of Convergence Signal Processing
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• v.2 no.2
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• pp.83-88
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• 2001

In this paper, System performance parameters such as throughput, blocking probability and delay have been analyzed and expressed as a function of demanding traffic and service terminating probability, and we centers our discussion at particular downlink port of satellite switch which is capable of switching the individual spot beam and processing the information signals in the packet satellite communications with demand assigned multiple access technique. Delay versa throughput as a function of traffic parameters with several service terminating probability can be derived via mathematical formulation and simulation and the relative change of transmission delay was compared.

• Journal of Korea Society of Digital Industry and Information Management
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• v.15 no.1
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• pp.53-59
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• 2019

As the number of harmful sites increases, many social problems are occurring. Therefore, in order to solve this problem, the government is carrying out activities to block access to web sites to harmful sites based on the law. However, due to the change from HTTP to HTTPS protocol, it has become difficult to block the harmful sites in the existing method. In the existing HTTP protocol, a method of blocking the site corresponding to the harmful site domain list by utilizing the DNS information was used. However, due to the generalization of HTTPS, it is difficult to block the harmful sites in the existing method. Therefore, the ISP uses the method of blocking the website using the SNI field in the TLS (Transport Layer Security) Handshake protocol used for HTTPS. However, since the method using SNI field raises the concern of monitoring Internet users or exposing information about connected sites, in this paper, we proposed method which can support anonymity to Internet users while blocking harmful sites. The suggested method also can support integrity and source authentication to the transmitted data.