• Journal of Internet Computing and Services
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• v.3 no.3
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• pp.67-74
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• 2002

Asynchronous transfer mode (ATM) can be efficiently used to transport packet data services. The switching system will support voice and packet data services simultaneously from end to end applications. To guarantee quality of service (QoS) of the offered services, source rate to send packet data is needed to control the network overload condition. Most existing control algorithms are shown to provide the threshold-based feedback control technique. However, real-time voice calls can be dynamically connected and released during data services in the network. If the feedback control information delays, quality of the serviced voice can be degraded due to a time delay between source and destination in the high speed link, An adaptive algorithm based on the optimal least mean square error technique is presented for the predictive feedback control technique. The algorithm attempts to predict a future buffer size from weight (slope) adaptation of unknown functions, which are used for feedback control. Simulation results are presented, which show the effectiveness of the algorithm.

• Journal of Internet Computing and Services
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• v.10 no.4
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• pp.199-211
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• 2009

Recent advancements in wireless networks have enabled support for mobile applications to transfer data over heterogeneous wireless paths in parallel using data striping technique [2]. Traditionally, high performance data transfer requires tuning of multiple TCP sockets, at sender's end, based on bandwidth delay product (BDP). Moreover, traditional techniques like Automatic TCP Buffer Tuning (ATBT), which balance memory and fulfill network demand, is designed for wired infrastructure assuming single flow on a single socket. Hence, in this paper we propose a buffer tuning technique at senders end designed to ensure high performance data transfer by striping data at transport layer across heterogeneous wireless paths. Our mechanism has the capability to become a resource management system for transport layer connections running on multi-homed mobile host supporting features for wireless link i.e. mobility, bandwidth fluctuations, link level losses. We show that our proposed mechanism performs better than ATBT, in efficiently utilizing memory and achieving aggregate throughput.

• Journal of Microbiology
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• v.44 no.4
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• pp.396-402
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• 2006

[ ${\beta}-Galactosidase$ ] is extensively employed in the manufacture of dairy products, including lactose-reduced milk. Here, we have isolated two gram-negative and rod-shaped coldadapted bacteria, BS 1 and HS 39. These strains were able to break down lactose at low temperatures. Although two isolates were found to grow well at $10^{\circ}C$, the BS 1 strain was unable to grow at $37^{\circ}C$. Another strain, HS-39, evidenced retarded growth at $37^{\circ}C$. The biochemical characteristics and the results of 16S rDNA sequencing identified the BS 1 isolate as Rahnella aquatilis, and showed that the HS 39 strain belonged to genus Buttiauxella. Whereas the R. aquatilis BS 1 strain generated maximal quantities of ${\beta}-galactosidase$ when incubated for 60h at $10^{\circ}C$, Buttiauxella sp. HS-39 generated ${\beta}-galactosidase$ earlier, and at slightly lower levels, than R. aquatilis BS 1. The optimum temperature for ${\beta}-galactosidase$ was $30^{\circ}C$ for R. aquatilis BS-1, and was $45^{\circ}C$ for Buttiauxella sp. HS-39, thereby indicating that R. aquatilis BS-1 was able to generate a cold-adaptive enzyme. These two cold-adapted strains, and most notably the ${\beta}-galactosidase$ from each isolate, might prove useful in some biotechnological applications.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.2
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• pp.709-730
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• 2017

To address the challenge of unprecedented growth in mobile data traffic, ultra-dense network deployment is a cost efficient solution to offload the traffic over some small cells. The overlapped coverage areas of small cells create more than one candidate access points for one mobile user. Signal strength based user association in IEEE 802.11 results in a significantly unbalanced load distribution among access points. However, the effective bandwidth demand of each user actually differs vastly due to their different preferences for mobile applications. In this paper, we formulate a set of non-linear integer programming models for joint user association control and user demand guarantee problem. In this model, we are trying to maximize the system capacity and guarantee the effective bandwidth demand for each user by soft-association control with a software defined network controller. With the fact of NP-hard complexity of non-linear integer programming solver, we propose a Kernighan Lin Algorithm based graph-partitioning method for a large-scale network. Finally, we evaluated the performance of the proposed algorithm for the edge users with heterogeneous bandwidth demands and mobility scenarios. Simulation results show that the proposed adaptive soft-association control can achieve a better performance than the other two and improves the individual quality of user experience with a little price on system throughput.

• Journal of KIISE:Software and Applications
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• v.33 no.10
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• pp.823-835
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• 2006

Multimedia is a very popular service in the Internet. But, we cannot provide multimedia service at a uniform content, because networks and devices are various. Thus, an adaptive service is needed for multimedia transmission. Video Transcoding is the good solution that can service multimedia adaptively. This paper proposes the streaming system that is composed of encoder, transcoder, decoder The encoder enhanced time complexity and PSNR in case of transcoding using PP(Prediction Period). The decoder is almost same as the traditional media player. Transcoder reduced time complexity through combination of prediction period in encoder and skipping period to control frame rate in transcoder. In simulation results, the performances of proposed scheme outperform the system with traditional transcoder in time complexity and PSNR.

• Journal of KIISE:Software and Applications
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• v.34 no.1
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• pp.59-69
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• 2007

In the video with a various environment, background modeling is important for extraction and recognition the moving object. For this object recognition, many methods of the background modeling are proposed in a process of preprocess. Among these there is a Kumar method which represents the Queue-based background modeling. Because this has a fixed period of updating examination of the frame, there is a limit for various system. This paper use a background modeling based on the queue. We propose the method that major parameters are decided as adaptive by background model. They are the queue size of the sliding window, the sire of grouping by the brightness of the visual and the period of updating examination of the frame. In order to determine the factors, in every process, RCO (Ratio of Correct Object), REO (Ratio of Error Object) and UR (Update Ratio) are considered to be the standard of evaluation. The proposed method can improve the existing techniques of the background modeling which is unfit for the real-time processing and recognize the object more efficient.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.1
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• pp.1-10
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• 2005

An aerodynamic shape optimization technique has been developed for helicopter rotor blades in hover based on a continuous adjoint method on unstructured meshes. The Euler flow solver and the continuous adjoint sensitivity analysis were formulated on the rotating frame of reference for hovering rotor blades. In order to handle the repeated evaluation of the design cycle efficiently, the flow and adjoint solvers were parallelized using a domain decomposition strategy. A solution-adaptive mesh refinement technique was adopted for the accurate capturing of the tip vortex. Applications were made for the aerodynamic shape optimization of Caradonna-Tung rotor blades and UH60 rotor blades in hover. The results showed that the present method is an effective tool to determine optimum aerodynamic shapes of rotor blades requiring less torque while maintaining the desired thrust level.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.10A
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• pp.1501-1506
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• 1999

DSRC(Dedicated Short Range Communications), which is a radio mobile communication protocol in ITS, is suited for traffic related information services. But in WAC(Wide-Area wireless communications), we could consider a conventional communication infrastructure in the case of supporting other applications besides ITS. Especially considering the current the trends to introduce wireless internet service into the mobile communication network, wireless internet service in ITS system is valuable. Although ITS LLC(Logical Link Control) protocols recommended by Europe and Japan are effective for traffic related services, it is not suitable for services related with geographical information, image or internet. That is because the data traffic characteristics is changed according to service types. Therefore we suggest a logical link control algorithm effective for traffic information related services as well as internet web service, and analyze its performance. As a result of numerical analysis and simulation, proposed algorithm shows larger performance improvements. For traffic information related services, the performance of DSRC LLC recommended by Europe and Japan is the same as that of proposed LLC protocol. However, for wireless internet web service, the performance of proposed protocol is much better than that of LLC protocol used in Europe and Japan.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.2C
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• pp.291-297
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• 2004

In this paper, a new structure for the AEC(Acoustic Echo Canceller) is proposed in which echo signal components that can be created in mobile communications is effectively eliminated. Block Data Flow Architecture is a parallel architecture that achieves high performance, high efficiency, high throughput, and almost linear speed up. The proposed architecture employs AEC and is implemented using the TMS320C6711 for real-time applications. The proposed AEC shows improved performance by eliminating echoes at 55ms delay path. Since the proposed AEC can also be implemented in Firmware, it is believed to effectively work on various types of echoes if it is applied on CDMA mobile devices. The TMS320C6711 shows much better performance comparing to previous DSPs. For experimental verifications, filtering operation using adaptive algorithm is performed on TMS320C6711 board and error signals resulted from computations are monitored on PC, and then the performance of the implemented AEC is verified through ERLE computation. According the results of simulation, good characteristic of 100dB are shown after 500 sampling data.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.7C
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• pp.544-553
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• 2012

A vehicle localization technology is an essential component to support many smart-vehicle applications, e.g. collision warning, adaptive cruise control, and so on. In this paper, we present a new vehicle localization algorithm based on the fusion of the sensing estimates from the local sensors and the GPS estimates from the inter-vehicle communications. The proposed algorithm consists of the greedy location data mapping algorithm and the position refinement algorithm. The former maps a sensing estimate with a GPS estimate based on the distance between themselves, and then the latter refines the GPS estimate of the subject vehicle based on the law of large numbers. From the numerical results, we demonstrate that the accuracy of the proposed algorithm outperforms that of the existing GPS estimates by at least 30 % in the longitudinal direction and by at least 60% in the lateral direction.