• 한국통신학회논문지
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• 제32권4A호
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• pp.330-335
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• 2007

본 논문에서는 멀티 홉 셀룰라 망에서 안정적인 멀티채널 랜덤 액세스 수율 보장을 위한 기지국 및 릴레이 노드 간의 랜덤 액세스 채널 할당 방안을 제안한다. 제안하는 방안에서는 채널 부하에 따라 기지국 및 릴레이 노드 간 랜덤 액세스 채널 할당 비율을 동적으로 조절할 수 있는 수학적 기준을 제시한다. 또한 랜덤 액세스 채널 할당 비율 조절만으로는 안정적 수율을 보장할 수 없는 높은 부하 상황에서는 랜덤 액세스 패킷 재전송 확률 조절 방식을 통해 안정적인 랜덤 액세스 수율을 보장하고자 한다. 시뮬레이션 결과는 제안하는 방안이 랜덤 액세스 패킷 생성률이 0.1 이상이 되는 고 부하 상황에서도 안정적인 채널 효율 및 패킷 전송 지연을 보장함을 보인다.

• 인터넷정보학회논문지
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• 제9권5호
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• pp.141-151
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• 2008

본 논문에서는 다중 서비스 다중 사용자 OFDMA 시스템에서의 임의 접근채널의 성능 분석을 수행하였다. OFDMA 시스템의 임의 접근 채널 자원은 가용한 부채널의 수와 PN-코드의 수이다. 이러한 임의 접근 채널의 자원이 주어진 경우, 임의 접근 채널의 성능을 각 서비스 클래스의 접속 성공 확률, 블로킹 확률, 접속 지연 그리고 처리율 관점에서 분석하였다. 또한 요구되는 각 서비스 클래스의 허용 가능한 최소 접속 성공 확률, 최대 접속 지연, 최대 블록킹 확률이 주어진 경우, 이를 만족할 수 있는 각 서비스 클래스의 접속 확률 값을 구하였다. 이 결과들은 각 서비스 클래스 사용자들에게 차등한 서비스 품질을 제공하고 적절한 시스템 운용점을 찾는데 유용하게 사용될 수 있다.

• Journal of Communications and Networks
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• 제6권4호
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• pp.352-361
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• 2004

In this paper, we study how to achieve the maximum capacity under delay constraints for large mobile wireless networks. We develop a systematic methodology for studying this problem in the asymptotic region when the number of nodes n in the network is large. We first identify a number of key parameters for a large class of scheduling schemes, and investigate the inherent tradeoffs among the capacity, the delay, and these scheduling parameters. Based on these inherent tradeoffs, we are able to compute the upper bound on the maximum per-node capacity of a large mobile wireless network under given delay constraints. Further, in the process of proving the upper bound, we are able to identify the optimal values of the key scheduling parameters. Knowing these optimal values, we can then develop scheduling schemes that achieve the upper bound up to some logarithmic factor, which suggests that our upper bound is fairly tight. We have applied this methodology to both the i.i.d. mobility model and the random way-point mobility model. In both cases, our methodology allows us to develop new scheduling schemes that can achieve larger capacity than previous proposals under the same delay constraints. In particular, for the i.i.d. mobility model, our scheme can achieve (n-1/3/log3/2 n) per-node capacity with constant delay. This demonstrates that, under the i.i.d. mobility model, mobility increases the capacity even with constant delays. Our methodology can also be extended to incorporate additional scheduling constraints.

• 음성과학
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• 제1권
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• pp.285-293
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• 1997

This paper was constructed to investigate strange attractor in considering speech which is regarded as chaos in that the random signal appears in the deterministic raising system. This paper searches for the delay time from AR model power spectrum for constructing fit attractor for speech signal. As a result of applying Taken's embedding theory to the delay time, an exact correlation dimension solution is obtained. As a result of this consideration of speech, it is found that it has more speaker recognition characteristic parameter, and gains a large speaker discrimination recognition rate.

• 한국정보통신학회논문지
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• 제12권2호
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• pp.360-368
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• 2008

본 논문에서는 다중 서비스 다중 사용자 OFDMA 시스템의 임의 접근채널에서 차별화된 서 비스 품질을 제공하기 위하여 backoff기반 임의 접근 알고리즘을 제안하고, 임의 접근 채널의 주 자원인 부채널의 수와 PN-코드의 수가 주어진 경우, 제안된 알고리즘의 성능을 각 서비스 클래스 접속 확률의 함수로서, 각 서비스 클래스의 접속 성공 확률, 처리율, 블로킹 확률, 접속 지연관점에서 분석한다. 수치적 분석을 통하여 제안된 backoff 기반 임의 접근 알고리즘이 서로 다른 서비스 클래스의 임의접근 시도들에게 차등한 서비스 품질을 제공할 수 있음을 보였다.

• Journal of the Korean Data and Information Science Society
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• 제17권3호
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• pp.687-705
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• 2006

In this paper we consider GPH distribution that is defined as a distribution for sum of random number of random variables following exponential distribution. We establish approximation process of general distributions to GPH distributions and offer numerical results for various cases to show the accuracy of the approximation. We also propose analysis method of delay distribution of queueing systems using approximation to GPH distributions and offer numerical results for various queueing systems to show applicability of GPH approximation.

• 대한전기학회논문지:시스템및제어부문D
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• 제53권11호
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• pp.786-792
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• 2004

A wavelet based ECG data compression has become an attractive and efficient method in many mobile tele-cardiology applications. But large data size required for high compression performance leads a serious delay. In this paper, new wavelet compression method with minimum delay is proposed. It is based on deciding the type and compression ratio(CR) of block organically according to the standard deviation of input ECG data with minimum block size. Compression performances of the proposed algorithm for different MIT ECG Records were analyzed comparing other ECG compression algorithm. In addition to the processing delay measurement, compression efficiency and reconstruction sensitivity to error were also evaluated via random noise simulation models. The results show that the proposed algorithm has both lower PRD than other algorithm on same CR and minimum time in the data acquisition, processing and transmission.

• 대한산업공학회지
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• 제34권3호
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• pp.289-295
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• 2008

The shared-route decision algorithms in multicasting communications networks to provide the internet-based services such as IPTV, remote education/health, and internet broadcasting are presented. The three main measures of maximum delay, average delay and estimated delay between each node and member are adopted. Under the Mesh network with the uniform random cost between each node, the algorithm's performance is compared to the optimal solution with the minimum cost by all enumeration. The simulation results show that the algorithm using the estimated delay outperforms the other two methods.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 합동 추계학술대회 논문집 정보 및 제어부문
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• pp.150-153
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• 2002

When a system is teleoperated in the indoor environment through the wireless LAN, we must consider the communication time delay. The time delay is random and unbounded due to the inherent characteristic and surrounding environment. As result of this, the stability and performance of the teleoperated system is degraded. In this paper, we present the adaptive control algorithm to overcome this problem by measuring time delay and allocating task corresponding to time delay dynamically. And the simple experiment is conducted to demonstrate the feasibility.

• 제어로봇시스템학회논문지
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• 제15권9호
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• pp.929-938
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• 2009

This paper presents a novel control methodology for communication network based nonlinear systems with time delay nature. We construct a nominal nonlinear control law for representing a linear model and a reset control system which is aimed for corrective control strategy to compensate system error due to uncertain time delay through wireless communication network. Next, online neural control approach is proposed for overcoming nonstationary statistical nature in the network topology. Additionally, DBN (Dynamic Bayesian Network) technique is accomplished for modeling of its dynamics in terms of casuality, which is then utilized for estimating prediction of system output. We evaluate superiority and reliability of the proposed control approach through numerical simulation example in which a nonlinear inverted pendulum model is employed as a networked control system.