• Proceedings of the Korean Information Science Society Conference
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• 2011.06a
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• pp.559-561
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• 2011

멀티코어 환경에서는 공유 데이터에 대한 동기화로 인한 병목 현상이 중요한 문제점 중의 하나이다. 그리고 동적 메모리 할당자는 대량의 메모리를 할당 및 해제하는 프로그램에서 공유 데이터에 대한 동기화 문제로 성능 저하를 유발시키고 있다. 이를 해결하기 위해 다양한 lock-free 메모리 할당 기법들이 소개되었지만 false sharing과 heap blow-up과 같은 여러 가지 문제점들을 가지고 있다. 이에 본 논문에서는 새로운 연속할당 기법을 제안하고, 이를 이용하여 동일 블록 내의 오브젝트 할당/해제에 따른 동기화 문제를 해결함으로써 효과적인 lock-free 메모리 할당 기법을 제안하였다. 그리고 제안 기법을 구현하여 기존의 메모리 할당 기법들과 실험을 통하여 검증하였으며, 대량의 메모리를 사용하는 멀티 스레드 환경에서 특히 좋은 성능을 보이는 것을 확인하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.9
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• pp.1998-2016
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• 2012

Reliable spectrum sensing algorithm is a fundamental component in cognitive radio. In this paper, a non-cooperative spectrum sensing algorithm which needs only one cognitive radio node named CORDIC (Coordinate Rotation Digital Computer) Jacobi based method is proposed. The algorithm computes the eigenvalues of the sampled covariance of received signal mainly by shift and additional operations, which is suitable for hardware implementation. Based the latest random matrix theory (RMT) about the distribution of the limiting maximum and minimum eigenvalue ratio, the relationship between the probability of false alarm and the decision threshold is derived. Simulations and discussions show the method is effective. Real captured digital television (DTV) signals and Universal Software Radio Peripheral (USRP) are also employed to evaluate the performance of the algorithm, which prove the proposed algorithm can be applied in practical spectrum sensing applications.

• Journal of information and communication convergence engineering
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• v.9 no.1
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• pp.27-31
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• 2011

This paper describes the optimization of spectrum sensing in terms of the throughput of a cognitive radio (CR) system. Dealing with the optimization problem of spectrum sensing, this paper evaluates the throughput of a CR system by considering such situations as the penalty time of a channel search and incumbent user (IU) detection delay caused by a missed detection of an incumbent signal. Also, this paper suggests a serial channel search scheme as the search method for a vacant channel, and derives its mean channel search time by considering the penalty time due to the false alarm of a vacant channel search. The numerical results suggest the optimum sensing time of the channel search process using the derived mean channel search time of a serial channel search in the case of a sensing hardware structure with single radio frequency (RF) path. It also demonstrates that the average throughput is improved by two separate RF paths in spite of the hardware complexity of an RF receiver.

• Proceedings of the Korea Information Processing Society Conference
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• 2009.11a
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• pp.445-446
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• 2009

IEEE 802.11 환경은 RTS/CTS(Request To Send/Clear To Send)을 지원한다. TS/CTS의 사용하면 Hidden Node Problem을 해결할 수 있지만 같은 셀안에 다른 노드를 대기상태로 만드는 False Node Problem이 발생하여 전송률을 감소시킨다. 따라서 본 논문에서는 체크포인트 방식을 사용하여 매체점유시간을 줄이는 제어프레임을 설계하고자 한다. 설계한 제어프레임의 OPNET을 사용하여 시뮬레이션하며, 기존의 제어프레임과 제안하는 제어프레임의 Delay를 비교함으로써 무선네트워크 환경에서 전송 효율을 비교 분석한다.

• Proceedings of the Korea Contents Association Conference
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• 2004.11a
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• pp.384-388
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• 2004

In this paper, we analyses transmission performance of synchronization pattern for over the air rekeying in aerial tactical link of LINK16, when it is given by symbol error rate, in respect of pattern detection probability and false alarm probability.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2006.07a
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• pp.316-316
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• 2006

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2004.07a
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• pp.213-213
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• 2004

• Journal of the Korea Institute of Information and Communication Engineering
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• v.6 no.4
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• pp.527-534
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• 2002

In this paper, efficiency in the acquisition of the PN code of the DS/CDMA system was analyzed by using the Nakagami-m probability density function that can model diverse fading channels. The system considers the fading environment that inevitably exists in the mobile communications channel environment. To analyze the efficiency of the system, the equations related to detection probability PD and false alarm probability PFA required for the acquisition of the PN code were induced by using the Nakagami-m probability density function. They were verified through simulation. For the DS/CDMA system an adaptive serial search technique was applied to acquire the PN code. To correct phase error, the equations related to detection probability PD and false alarm probability PFA that influence the time to acquire codes were induced after adding the PLL to each branch of the Rake Receiver. By using an induced equation, detection probability PD and false alarm probability PFA were verified through simulation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.11B
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• pp.730-735
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• 2005

While the E-mail is a important way of fast communication in these days. it is real that the E-mail is often misused as a commercial advertisement method and creates many social problems. Even though various filtering techniques for blocking spam mails have been developed, reliability of mail systems is decreased by misreading normal mails as spam mails, i.e. false-positive errors. In this paper, the SMBC(Spam Mail Blocking Center) platform employing spam mail recovery method based on privacy information is proposed and designed. The SMBC is designed in frame layer based on spam blocking system of proxy sewer and can be physically implemented in various topology so that flexible development with layered module is possible. Using privacy information makes the proposed SMBC platform minimize processing load and false-positive error rates so that it can improve mail system reliabilities.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.3
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• pp.456-463
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• 2021

In this paper, Ultra Wide-Band(UWB) radar sensor is employed to detect flying drones and avoid collision in dense clutter environments. UWB signal is preferred when high resolution range measurement is required for moving targets. However, the time varying motion of flying drones may increase clutter noises in return signals and deteriorates the target detection performance, which lead to the performance degradation of anti-collision radars. We adopt a dynamic clutter suppression algorithm to estimate the time-varying distances to the moving drones with enhanced accuracy. A modified Constant False Alarm Rate(CFAR) is developed using an adaptive filter algorithm to suppress clutter while the false detection performance is well maintained. For this purpose, a velocity dependent CFAR algorithm is implemented to eliminate the clutter noise against dynamic target motions. Experiments are performed against flying drones having arbitrary trajectories to verify the performance improvement.