• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.2
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• pp.161-168
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• 2019

This paper proposes a variable data transfer asymmetric TDD(Time Division Duplex) system for small UAV(Unmanned Aerial Vehicle) data link system. In the proposed method, a turbo decoder with a double buffer controller is proposed to apply turbo decoder with long decoding time to asymmetric TDD system. The proposed method achieves variable data transfer rate and maximum data transfer rate. The advantage of the proposed method is demonstrated by its data transfer rate. The measured data transfer rate is more than 1.8 times than that of symmetric TDD system. In addition, PER(Packet Error Rate) performance is the same and data transfer rate is variable.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.54 no.11
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• pp.673-679
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• 2005

This Paper presents the 3D wavelet transformation based video compression system, which possesses the capability of progressive transmission by increasing resolution and increasing rate for multimedia applications. The 3D wavelet packet based video compression system removes the temporal correlation of the input sequences using the motion compensation filter and decomposes the spatio-temporal subband using the spatial wavelet packet transformation. The proposed system allocates the higher bit rate to the low frequency image of the 3D wavelet sequences and improves the 0.49dB PSNR performance of the reconstructed image in comparison with that of H.263. In addition to the limitation on the propagation of the motion compensation error by the 3D wavelet transformation, the proposed system progressively transmits the input sequence according to the resolution and rate scalability.

• Journal of Internet Computing and Services
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• v.8 no.5
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• pp.125-132
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• 2007

Transmission mechanisms that include an available bandwidth estimation algorithm and a packet loss differentiation scheme, in general, exhibit higher TCP performance in wireless networks. TCP New Jersey, known as the best existing scheme in terms of goodput, improves wireless TCP performance using the available bandwidth estimation at the sender and the congestion warning at intermediate routers. Although TCP New Jersey achieves 17% and 85% improvements in goodput over TCP Westwood and TCP Reno, respectively, we further improve TCP New Jersey by exploring improved available bandwidth estimation, retransmission timeout, and recovery mechanisms. Hence, we propose TCP New Jersey PLUS (shortly TCP NJ+), showing that under 1% packet loss rate, it outperforms 3% by TCP New Jersey and 5% by TCP Wes1wood. In 5% packet loss rate, a characteristic of high bit-error-rate wireless network, it outperforms other TCP variants by 19% to 104% in terms of goodput even when the network is in bi-directional congestion.

• Journal of Advanced Navigation Technology
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• v.18 no.1
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• pp.67-73
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• 2014

Due to the development of the communication technology and the high-performance mobile device, the number of video streaming service user has been increasing. Video streaming services in the restricted network environments need error control to support users for the Ultra High Definition(UHD) video delivery. Packet-level FEC method was used to control the error for delay-sensitive video service, but it has a defect in huge occupation of network resources by redundant packets. In this paper, we proposed a packet-level FEC algorithm which maintains the video quality by previous FEC methods and also reduces the occupation of network resource in the restricted network environments. The proposed algorithm controls the redundant rate with using the delivery characteristic of the video coding technology, and improves the efficiency of network resources by reducing the traffic by around 33% in comparison with the previous FEC methods.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.4 no.5
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• pp.819-835
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• 2010

In this paper, two selection relaying schemes are proposed and compared with each other in terms of packet error rate (PER) and diversity order. Moreover, the comparison is performed over two different fading environments including fast and slow fading environments in which the diversity order is considered as the important factor to reach the decision which scheme is suitable for each fading environment. Numerical results validate the analytical results and indicate significant differences on the PER performance of two schemes over two fading environments.

• Journal of electromagnetic engineering and science
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• v.12 no.3
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• pp.189-195
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• 2012

In this paper, we propose a novel protocol called a Multi-hop Diversity Transmission protocol in which the retransmission is realized by a relay that is Nearest to a current Source (MDTNS). We derive the mathematical expressions of the packet error rate (PER) and the average number of transmissions over Nakagami-m fading channels, and verify them by Monte Carlo simulations. The simulation results show that the MDTNS protocol improves the performance of the network in terms of PER when compared to the Multi-hop Diversity Transmission protocol in which the retransmission is done by a relay that is Nearest to Destination (MDTND) and to the conventional multi-hop transmission (CMT) protocol.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.5C
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• pp.490-496
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• 2006

H.264 is the most recent video coding standard, containing improved error resilience tools than previous video compression schemes. This paper shows an analysis of the dependency of error concealment (EC) performance on the expected number of correctly received neighboring macroblock(MB)s for a lost MB, applying error concealment schemes to the raster scan mode that is used in the previous video coding standard and the flexible macroblock ordering (FMO) which is one of error-resilience tools in H.264. We also present simulation results and performance evaluation with various packet loss rates. Simulation results show that the FMO mode provides better EC performances of $1{\sim}9dB$ PSNR improvements compared to the raster scan mode because of larger expected number of correctly received neighboring MBs. The PSNR improvement by FMO mode becomes higher as the intra-frame period is larger and the packet loss rate is higher.

• Journal of information and communication convergence engineering
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• v.7 no.1
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• pp.7-12
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• 2009

The advanced computer network and Internet technology enables connectivity of computers through an open network environment. Despite the growing numbers of security threats to networks, most intrusion detection identifies security attacks mainly by detecting misuse using a set of rules based on past hacking patterns. This pattern matching has a high rate of false positives and can not detect new hacking patterns, making it vulnerable to previously unidentified attack patterns and variations in attack and increasing false negatives. Intrusion detection and prevention technologies are thus required. We proposed a network based hybrid Probe Intrusion Detection model using Fuzzy cognitive maps (PIDuF) that detects intrusion by DoS (DDoS and PDoS) attack detection using packet analysis. A DoS attack typically appears as a probe and SYN flooding attack. SYN flooding using FCM model captures and analyzes packet information to detect SYN flooding attacks. Using the result of decision module analysis, which used FCM, the decision module measures the degree of danger of the DoS and trains the response module to deal with attacks. For the performance evaluation, the "IDS Evaluation Data Set" created by MIT was used. From the simulation we obtained the max-average true positive rate of 97.064% and the max-average false negative rate of 2.936%. The true positive error rate of the PIDuF is similar to that of Bernhard's true positive error rate.

• Journal of the Institute of Convergence Signal Processing
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• v.23 no.2
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• pp.50-61
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• 2022

This work demonstrates the design and evaluation of Aqua-Aware, a lightweight miniaturized light emitting diode (LED) based underwater compact sensor node which is used to obtain different characteristics of the underwater environment. Two optical sensor nodes have been designed, developed, and evaluated for a short and medium link range called as Aqua-Aware short range (AASR) and Aqua-Aware medium range (AAMR), respectively. The hardware and software implementation of proposed sensor node, algorithms, and trade-offs have been discussed in this paper. The underwater environment is emulated by introducing different turbulence effects such as air bubbles, waves and turbidity in a 4-m water tank. In clear water, the Aqua-Aware achieved a data rate of 0.2 Mbps at communication link up to 2-m. The Aqua-Aware was able to achieve 0.2 Mbps in a turbid water of 64 NTU in the presence of moderate water waves and air bubbles within the communication link range of 1.7-m. We have evaluated the luminous intensity, packet success rate and bit error rate performance of the proposed system obtained by varying the various medium characteristics.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.7C
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• pp.691-699
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• 2006

Despite of the in-depth effort to cantrol the variability in IP networks, quality of service (QoS) is still not guaranteed in the IP networks. Thus, it is necessary to deal with the audible artifacts caused by packet lasses. To overcame the packet loss problem, most speech coding standard have their own embedded packet loss concealment (PLC) algorithms which adapt extrapolation methods utilizing the dependency on adjacent frames. Since many low bit rate CELP coders use predictive schemes for increasing coding efficiency, however, error propagation occurs even if single packet is lost. In this paper, we propose an efficient PLC algorithm with consideration about the speech characteristics of lost frames. To design an efficient PLC algorithm, we perform several experiments on investigating the error propagation effect of lost frames of a predictive coder. And then, we summarize the impact of packet loss to the speech characteristics and analyze the importance of the encoded parameters depending on each speech classes. From the result of the experiments, we propose a new PLC algorithm that mainly focuses on reducing the error propagation time. Experimental results show that the performance is much higher than conventional extrapolation methods over various frame erasure rate (FER) conditions. Especially the difference is remarkable in high FER condition.