Performance enhancement of TCP in high-speed networks

GridFTP is a secure and reliable high-performance parallel data transfer protocol used for transferring massive amounts of widely distributed data. Currently it allows users to configure the number of parallel streams and socket buffer size. However, its tuning procedure for optimal combination is a time consuming task. The socket handlers and buffers are important system resources and must therefore be carefully managed. In this paper, we propose a scheme to achieve high throughput even with a smaller buffer size, and also derive a regression equation to predict the optimal combination of resources for a connection. To improve the performance, the TCP based on our scheme obtains higher throughput and spends less memory for the same throughput than the original TCP scheme. In addition, the regression equation is verified by comparing measured and predicted values, and we apply the equation to an actual experiment on the KOrea advanced REsearch Network (KOREN). The result demonstrates that the equation provides excellent predictions with only an 8% error boundary.     

A critical review of selective attention: an interdisciplinary perspective

During the last half century, significant efforts have been made to explore the underlying mechanisms of visual selective attention using a variety of approaches—psychology, neuroscience, and computational models. Among them, the computational approach emerged on the stage with the development of computer science and computer vision focusing researchers interests in this area. However, computer scientists often face the difficulty of how to construct a computational model of selective attention working on their own purpose. Here, we critically review studies of selective attention from a multidisciplinary perspective to take lessons from psychological and biological studies of attention. We consider how constraints from those studies can be imposed on computational models of selective attention.     

An Efficient Data Dissemination Scheme for Spatial Query Processing

Due to the personal portable devices and advances in wireless communication technologies, Location Dependent Information Services （LDISs） have received a lot of attention from both the industrial and academic communities. In LDISs, it is important to reduce the query response time, since a late query response may contain out-of-date information. In this paper, we study the issue of LDISs using a Voronoi Diagram. We introduce a new NN search method, called the Exponential Sequence Scheme （ESS）, to support NN query processing in periodic broadcast environment. This paper aims to provide research directions towards minimizing both the access latency and energy consumption for the NN-query processing.     

On bandwidth adjusted multicast communications in pipeline router architecture

We have developed a novel algorithm to adjust link-bandwidths of a given multicast tree, which sends a message with sizer from a source to a multiple destinations taking into consideration pipelined router. The algorithm that we have developed tries to minimize the end-to-end delay time and resources such as bandwidths of a multicast tree, and performs admirably well in any given multicast tree. Our evaluation shows that the proposed algorithm dramatically reduces the end-to-end delay time and resources reserved to satisfy the time-constraints. This work was supported in parts by BK21 and the Ministry of Information and Communication, Korea. Corresponding author: H. Choo.     

Process Simulation Using Randomized Markov Chain and Truncated Marginal Distribution

Generating pseudo random objects is one of the key issues in computer simulation of complex systems. Most earlier simulation systems include procedures for the generation of independent and identically distributed random variables or some classical random processes, such as white noise. In this paper we propose a new approach to the generation of wide ranges of processes that are characterized by marginal distribution and autocorrelation function that are significant in many cases. The proposed algorithm is based on the use of truncated distribution that gives more simplicity and efficiency in comparison with the previous one. The effectiveness of the proposed algorithm is verified using computer simulation of various real examples.     

Processor scheduling and allocation for 3D torus multicomputersystems

Multicomputer systems achieve high performance by utilizing a number of computing nodes. Recently, by achieving significant reductions in communication delay, the three-dimensional (3D) torus has emerged as a new candidate interconnection topology for message-passing multicomputer systems. In this paper, we propose an efficient processor allocation scheme-scan search scheme-for the 3D torus based on a first-fit approach. The scan search scheme minimizes the average allocation time for an incoming task by effectively manipulating the 3D information on a torus as 2D information using a data structure called the CST (Coverage Status Table). Comprehensive computer simulation reveals that the allocation time of the scan search scheme is always smaller than that of the earlier scheme based on a best-fit approach. The difference gets larger as the input load increases, and it is as much a factor of 3 for high load. To investigate the performance of the proposed scheme in different scheduling environments, we also consider a non-FCFS scheduling policy along with the typical FCFS policy. The allocation time complexity of the scan search scheme is O(LW²H²). This is significantly smaller than that of the existing scheme which is O(L⁴W⁴H⁴). Here, L, W, and H represent the length, width, and height of 3D torus, respectively     

Image-Based Lifelogging: User Emotion Perspective

Lifelog is a digital record of an individual’s daily life. It collects, records, and archives a large amount of unstructured data; therefore, techniques are required to organize and summarize those data for easy retrieval. Lifelogging has been utilized for diverse applications including healthcare, self-tracking, and entertainment, among others. With regard to the image-based lifelogging, even though most users prefer to present photos with facial expressions that allow us to infer their emotions, there have been few studies on lifelogging techniques that focus upon users’ emotions. In this paper, we develop a system that extracts users’ own photos from their smartphones and configures their lifelogs with a focus on their emotions. We design an emotion classifier based on convolutional neural networks (CNN) to predict the users’ emotions. To train the model, we create a new dataset by collecting facial images from the CelebFaces Attributes (CelebA) dataset and labeling their facial emotion expressions, and by integrating parts of the Radboud Faces Database (RaFD). Our dataset consists of 4,715 high-resolution images. We propose Representative Emotional Data Extraction Scheme (REDES) to select representative photos based on inferring users’ emotions from their facial expressions. In addition, we develop a system that allows users to easily configure diaries for a special day and summaize their lifelogs. Our experimental results show that our method is able to effectively incorporate emotions into lifelog, allowing an enriched experience.     

Resource Allocation with Partitioning Criterion for Macro-Femto Overlay Cellular Networks with Fractional Frequency Reuse

The interference mitigation technique based on fractional frequency reuse (FFR) provides improved cell-edge performance with similar overall cell capacity as that of systems with the frequency reuse factor of one. Furthermore, frequency sub-band allocation by FFR has the benefit of allowing flexibility for the deployment of femto-cells through frequency partitioning. Determination of a proper frequency partitioning criterion between the cell-center and the cell-edge, and between the cells with femto-cells is an important issue. In addition, time resource partitioning introduces another degree of freedom to the design of time-frequency resource allocation. In this paper, we propose a novel time-frequency resource allocation mechanism using FFR for a macro-femto overlay cellular network. Feasible frequency sub-band and time resource is allocated to the cell-center and the cell-edge region in a cell by the proposed partitioning criterion and the time partitioning ratio. We provide a guideline for how to determine the partitioning criterion for the regions and how to design the amount of time resource. We derive the average capacity of macro-cells and femto-cells, and introduce a new harmonic mean metric to maximize the average capacity of the regions while achieving the fairness among users in a cell.     

Design and experimental evaluation of OnDemand inter-domain mobility in SDN supported PMIPv6

Wireless Networks - The soaring number of mobile devices and their demands for enhanced services have forced operators to adopt locally software defined and globally distributed multi-domain...