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Computers, Volume 4, Issue 2 (June 2015) – 5 articles , Pages 61-175

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Open AccessArticle
A Reference Point Construction Method Using Mobile Terminals and the Indoor Localization Evaluation in the Centroid Method
Computers 2015, 4(2), 155-175; https://doi.org/10.3390/computers4020155 - 22 May 2015
Cited by 1 | Viewed by 4185
Abstract
As smartphones become widespread, a variety of smartphone applications are being developed. This paper proposes a method for indoor localization (i.e., positioning) that uses only smartphones, which are general-purpose mobile terminals, as reference point devices. This method has the following features: [...] Read more.
As smartphones become widespread, a variety of smartphone applications are being developed. This paper proposes a method for indoor localization (i.e., positioning) that uses only smartphones, which are general-purpose mobile terminals, as reference point devices. This method has the following features: (a) the localization system is built with smartphones whose movements are confined to respective limited areas. No fixed reference point devices are used; (b) the method does not depend on the wireless performance of smartphones and does not require information about the propagation characteristics of the radio waves sent from reference point devices, and (c) the method determines the location at the application layer, at which location information can be easily incorporated into high-level services. We have evaluated the level of localization accuracy of the proposed method by building a software emulator that modeled an underground shopping mall. We have confirmed that the determined location is within a small area in which the user can find target objects visually. Full article
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Open AccessArticle
Semi-Automatic Image Labelling Using Depth Information
Computers 2015, 4(2), 142-154; https://doi.org/10.3390/computers4020142 - 06 May 2015
Cited by 5 | Viewed by 4158
Abstract
Image labeling tools help to extract objects within images to be used as ground truth for learning and testing in object detection processes. The inputs for such tools are usually RGB images. However with new widely available low-cost sensors like Microsoft Kinect it [...] Read more.
Image labeling tools help to extract objects within images to be used as ground truth for learning and testing in object detection processes. The inputs for such tools are usually RGB images. However with new widely available low-cost sensors like Microsoft Kinect it is possible to use depth images in addition to RGB images. Despite many existing powerful tools for image labeling, there is a need for RGB-depth adapted tools. We present a new interactive labeling tool that partially automates image labeling, with two major contributions. First, the method extends the concept of image segmentation from RGB to RGB-depth using Fuzzy C-Means clustering, connected component labeling and superpixels, and generates bounding pixels to extract the desired objects. Second, it minimizes the interaction time needed for object extraction by doing an efficient segmentation in RGB-depth space. Very few clicks are needed for the entire procedure compared to existing, tools. When the desired object is the closest object to the camera, which is often the case in robotics applications, no clicks at all are required to accurately extract the object. Full article
Open AccessArticle
Error and Congestion Resilient Video Streaming over Broadband Wireless
Computers 2015, 4(2), 113-141; https://doi.org/10.3390/computers4020113 - 21 Apr 2015
Cited by 1 | Viewed by 4158
Abstract
In this paper, error resilience is achieved by adaptive, application-layer rateless channel coding, which is used to protect H.264/Advanced Video Coding (AVC) codec data-partitioned videos. A packetization strategy is an effective tool to control error rates and, in the paper, source-coded data partitioning [...] Read more.
In this paper, error resilience is achieved by adaptive, application-layer rateless channel coding, which is used to protect H.264/Advanced Video Coding (AVC) codec data-partitioned videos. A packetization strategy is an effective tool to control error rates and, in the paper, source-coded data partitioning serves to allocate smaller packets to more important compressed video data. The scheme for doing this is applied to real-time streaming across a broadband wireless link. The advantages of rateless code rate adaptivity are then demonstrated in the paper. Because the data partitions of a video slice are each assigned to different network packets, in congestion-prone wireless networks the increased number of packets per slice and their size disparity may increase the packet loss rate from buffer overflows. As a form of congestion resilience, this paper recommends packet-size dependent scheduling as a relatively simple way of alleviating the buffer-overflow problem arising from data-partitioned packets. The paper also contributes an analysis of data partitioning and packet sizes as a prelude to considering scheduling regimes. The combination of adaptive channel coding and prioritized packetization for error resilience with packet-size dependent packet scheduling results in a robust streaming scheme specialized for broadband wireless and real-time streaming applications such as video conferencing, video telephony, and telemedicine. Full article
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Open AccessArticle
A Dynamic Reputation Management System for Mobile Ad Hoc Networks
Computers 2015, 4(2), 87-112; https://doi.org/10.3390/computers4020087 - 17 Apr 2015
Cited by 6 | Viewed by 4459
Abstract
Nodes in mobile ad hoc networks (MANETs) are mandated to utilize their limited energy resources in forwarding routing control and data packets for other nodes. Since a MANET lacks a centralized administration and control, a node may decide to act selfishly, either by [...] Read more.
Nodes in mobile ad hoc networks (MANETs) are mandated to utilize their limited energy resources in forwarding routing control and data packets for other nodes. Since a MANET lacks a centralized administration and control, a node may decide to act selfishly, either by refusing to respond to route requests from other nodes or deceitfully by responding to some route requests, but dropping the corresponding data packets that are presented for forwarding. A significant increase in the presence of these misbehaving nodes in a MANET can subsequently degrade network performance. In this paper, we propose a dynamic reputation management system for detecting and isolating misbehaving nodes in MANETs. Our model employs a novel direct monitoring technique to evaluate the reputation of a node in the network, which ensures that nodes that expend their energy in transmitting data and routing control packets for others are allowed to carry out their network activities while the misbehaving nodes are detected and isolated from the network. Simulation results show that our model is effective at curbing and mitigating the effects of misbehaving nodes in the network. Full article
Open AccessArticle
A Secure System Architecture for Measuring Instruments in Legal Metrology
Computers 2015, 4(2), 61-86; https://doi.org/10.3390/computers4020061 - 24 Mar 2015
Cited by 8 | Viewed by 5036
Abstract
Embedded systems show the tendency of becoming more and more connected. This fact combined with the trend towards the Internet of Things, from which measuring instruments are not immune (e.g., smart meters), lets one assume that security in measuring instruments will inevitably play [...] Read more.
Embedded systems show the tendency of becoming more and more connected. This fact combined with the trend towards the Internet of Things, from which measuring instruments are not immune (e.g., smart meters), lets one assume that security in measuring instruments will inevitably play an important role soon. Additionally, measuring instruments have adopted general-purpose operating systems to offer the user a broader functionality that is not necessarily restricted towards measurement alone. In this paper, a flexible software system architecture is presented that addresses these challenges within the framework of essential requirements laid down in the Measuring Instruments Directive of the European Union. This system architecture tries to eliminate the risks general-purpose operating systems have by wrapping them, together with dedicated applications, in secure sandboxes, while supervising the communication between the essential parts and the outside world. Full article
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