• Title, Summary, Keyword: Recovery Algorithm

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A new dual-mode blind equalization algorithm combining carrier phase recovery (반송파 위상 복원을 결합한 새로운 이중모드 블라인드 등화 알고리즘)

  • 오길남;진용옥
    • Journal of the Korean Institute of Telematics and Electronics A
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    • v.32A no.5
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    • pp.14-23
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    • 1995
  • A new dual-mode algorithm for blind equalization of quadrature amplitude modulation (QAM) signals is proposed. To solve the problem that the constant modulus algorithm (CMA) converges to the constellation with the arbitrary phase rotation, with the modification of the CMA, the proposed algorithm accomplishes blind equalization and carrier phase recovery simultaneously. In addition, the dual-mode algorithm combining the modified constant modulus algorithm (MCMA) with decision-directed (DD) algorithm achieves the performance enhancement of blind convergence speed and steady-state residual ISI. So we can refer the proposed algorithm to as a scheme for joint blind equalization and carrier phase recovery. Simulation results for i.i.d. input signals confirm that the dual-mode algorithm results in faster convergence speed, samller residual ISI, and better carrier phase recovery than those of the CMA and DD algorithm without any significant increase in computational complexity.

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A New Carrier Recovery Algorithm Usign $\theta$-matching method for QAM Demodulator ($\theta$-정합을 이용한 QAM 복조용 Carrier Recovery)

  • 박휘원;장일순정차근조경록
    • Proceedings of the IEEK Conference
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    • pp.179-182
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    • 1998
  • Carrier recovery, the process of recoverying the carrier in receiver, removes the phase difference between VCO and the received signal. However, the conventional structure of carrier recovery cannot be applied to multi-level QAM demodulator because of the increasing decision interval and the complexity of control as the number of symbol increases. In this paper, we suggest a new carrier recovery algorithm using $\theta-matching$ algorithm for multi-level QAM demodulation to overcome this problem and analysis the performance and implement it.

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Light Source Target Detection Algorithm for Vision-based UAV Recovery

  • Won, Dae-Yeon;Tahk, Min-Jea;Roh, Eun-Jung;Shin, Sung-Sik
    • International Journal of Aeronautical and Space Sciences
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    • v.9 no.2
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    • pp.114-120
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    • 2008
  • In the vision-based recovery phase, a terminal guidance for the blended-wing UAV requires visual information of high accuracy. This paper presents the light source target design and detection algorithm for vision-based UAV recovery. We propose a recovery target design with red and green LEDs. This frame provides the relative position between the target and the UAV. The target detection algorithm includes HSV-based segmentation, morphology, and blob processing. These techniques are employed to give efficient detection results in day and night net recovery operations. The performance of the proposed target design and detection algorithm are evaluated through ground-based experiments.

Improving Performance behavior of TCP over ATM Network in multiple losses of packets (다중 패킷 손실에서 TCP-ATM 네트워크의 성능개선 방안)

  • Park, U-Chul;Park, Sang-Jun;Lee, Byeong-Ho
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.37 no.10
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    • pp.18-25
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    • 2000
  • In this paper, we analyze TCP congestion control algorithm over ATM-UBR network. TCP congestion control algorithm consists of slow start, congestion avoidance, fast recovery, fast retransmit. We analyze the ATM-UBR network service using the BSD 4.3 TCP Reno, Vanilla. However we found the fact that the characteristic of fast retransmit, recovery algorithm makes a serious degradation of Performance in multiple losses of packets. We propose new fast retransmit, recovery algorithm to improve the problem. The results of performance analysis improve the multiple losses of packets using a proposed fast retransmit, recovery algorithm.

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Low-Cost Causal Message Logging based Recovery Algorithm Considering Asynchronous Checkpointing (비동기적 검사점 기록을 고려한 저 비용 인과적 메시지 로깅 기반 회복 알고리즘)

  • Ahn, Jin-Ho;Bang, Seong-Jun
    • The KIPS Transactions:PartA
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    • v.13A no.6
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    • pp.525-532
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    • 2006
  • Compared with the previous recovery algorithms for causal message logging, Elnozahy's recovery algerian considerably reduces the number of stable storage accesses and enables live processes to execute their computations continuously while performing its recovery procedure. However, if causal message logging is used with asynchronous checkpointing, the state of the system may be inconsistent after having executed this algorithm in case of concurrent failures. In this paper, we show these inconsistent cases and propose a low-cost recovery algorithm for causal message logging to solve the problem. To ensure the system consistency, this algorithm allows the recovery leader to obtain recovery information from not only the live processes, but also the other recovering processes. Also, the proposed algorithm requires no extra message compared with Elnozahy's one and its additional overhead incurred by message piggybacking is significantly low. To demonstrate this, simulation results show that the first only increases about 1.0%$\sim$2.1% of the recovery information collection time compared with the latter.

A New Carrier Phase-Independent Discrete STR Algorithm for Sampled Receiver (샘플수신기를 위한 반송파위상에 독립적인 이산 STR 알고리듬)

  • 김의묵;조병록;최형진
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.18 no.4
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    • pp.561-571
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    • 1993
  • In this paper, a new discrete Symbol Timing Recovery (STR) algorithm, is proposed. This algorithm is derived from the optimum estimation theory. The algorithm combines the advantages of Mueller and $M\"{u}ller$ algorithm and Gardner algorithm, and avoids some of their shortcomings. The implementation of the new timing detector is simple and the combined operations of Carrier Recovery (CR) -STR is possible because the operation of the new STR is independent of the carrier phase. On the other hand, the behavior of nonlinear characteristics in the new algorithm is analyzed and explained. The performance evaluation is accomplished in detail by numerical calculations and Monte-Carlo simulations. In these respects, this algorithm is similar to Gardner's algorithm, but in tracking performance due to pattern jitter at small rolloff, the proposed algorithm is superior to Gardner's algorithm.

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A Fast Timing Recovery Algorithm for Turbo-coded System

  • Long Nguyen Duc;Park Hyuncheol
    • Proceedings of the IEEK Conference
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    • pp.1-4
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    • 2004
  • We proposed a new type of timing recovery scheme to work with a system that uses BCJR (Bahl-Cocke-Jelinek-Raviv) decoding algorithm and BPSK modulation. The unknown timing offset is estimated by the modified Mueller and $M\ddot{u}ller$ estimator with the aid of the decoder. Timing offset can be acquired as soon as the symbols are received and be updated symbol by symbol. The simulation results for turbo codes whose decoder uses BCJR algorithm show a satisfactory performance even in case of severe timing jitter.

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Majorization-Minimization-Based Sparse Signal Recovery Method Using Prior Support and Amplitude Information for the Estimation of Time-varying Sparse Channels

  • Wang, Chen;Fang, Yong
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.12 no.10
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    • pp.4835-4855
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    • 2018
  • In this paper, we study the sparse signal recovery that uses information of both support and amplitude of the sparse signal. A convergent iterative algorithm for sparse signal recovery is developed using Majorization-Minimization-based Non-convex Optimization (MM-NcO). Furthermore, it is shown that, typically, the sparse signals that are recovered using the proposed iterative algorithm are not globally optimal and the performance of the iterative algorithm depends on the initial point. Therefore, a modified MM-NcO-based iterative algorithm is developed that uses prior information of both support and amplitude of the sparse signal to enhance recovery performance. Finally, the modified MM-NcO-based iterative algorithm is used to estimate the time-varying sparse wireless channels with temporal correlation. The numerical results show that the new algorithm performs better than related algorithms.

Implementation of Global Localization and Kidnap Recovery for Mobile Robot on Feature Map (표식 지도를 이용한 이동로봇의 광역 위치인식 및 kidnap recovery)

  • Lee, Jung-Suk;Lee, Kyoung-Min;Ahn, Sungh-Wan;Choi, Jin-Woo;Chung, Wan-Kyun
    • The Journal of Korea Robotics Society
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    • v.2 no.1
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    • pp.29-39
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    • 2007
  • We present an implementation of particle filter algorithm for global localization and kidnap recovery of mobile robot. Firstly, we propose an algorithm for efficient particle initialization using sonar line features. And then, the average likelihood and entropy of normalized weights are used as a quality measure of pose estimation. Finally, we propose an active kidnap recovery by adding new particle set. New and independent particle set can be initialized by monitoring two quality measures. Added particle set can re-estimate the pose of kidnapped robot. Experimental results demonstrate the capability of our global localization and kidnap recovery algorithm.

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A Multi-objective Optimization Approach to Workflow Scheduling in Clouds Considering Fault Recovery

  • Xu, Heyang;Yang, Bo;Qi, Weiwei;Ahene, Emmanuel
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.10 no.3
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    • pp.976-995
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    • 2016
  • Workflow scheduling is one of the challenging problems in cloud computing, especially when service reliability is considered. To improve cloud service reliability, fault tolerance techniques such as fault recovery can be employed. Practically, fault recovery has impact on the performance of workflow scheduling. Such impact deserves detailed research. Only few research works on workflow scheduling consider fault recovery and its impact. In this paper, we investigate the problem of workflow scheduling in clouds, considering the probability that cloud resources may fail during execution. We formulate this problem as a multi-objective optimization model. The first optimization objective is to minimize the overall completion time and the second one is to minimize the overall execution cost. Based on the proposed optimization model, we develop a heuristic-based algorithm called Min-min based time and cost tradeoff (MTCT). We perform extensive simulations with four different real world scientific workflows to verify the validity of the proposed model and evaluate the performance of our algorithm. The results show that, as expected, fault recovery has significant impact on the two performance criteria, and the proposed MTCT algorithm is useful for real life workflow scheduling when both of the two optimization objectives are considered.