Drago Zagar

Objective video quality metrics

This paper discusses methods used in different objective video quality metrics. An experimental comparison of different objective methods is also conducted. This experiment shows the importance of video content for a subjective quality evaluation not comprised well by the objective metrics used.

Influence of temporal pooling method on the objective video quality evaluation

Objective video quality evaluation incorporates spatial and temporal degradation effects to calculate quality grade for each video frame alone, as well as the overall quality grade for the whole sequence. Distortion visibility depends not only on the level of degradation but also on video content and viewers preferences. Temporal pooling is a method that collapses series of frame quality scores to one quality score for whole video sequence and it should be aware of an influence of the video quality variation to the human overall judgments of quality. In this paper six pooling methods applied to five objective video quality metrics are compared. The best prediction capability has been obtained by those pooling methods that reflect two phenomena: a recency effect and the worst quality section influence. Moreover, the statistics of individual frames scores tends to be of high importance and strongly influences pooling method capabilities.

Subjective and objective quality evaluation of the H.264/AVC coded video

The H.264/AVC codec provides a superior coding efficiency and an improved network adaptation if compared to older video standards. In this paper we present experimental results obtained by the subjective and objective quality evaluation of the H.264/AVC coded video. Four objective metrics are used: peak signal-to-noise ratio (PSNR), minimum of locally averaged PSNR (local_PSNR), video quality metric (VQM) and structural similarity index (SSIM). We have analyzed results of objective and subjective metrics for several CIF sequences and bit rates. Also, we have compared results obtained for H.264/AVC coded sequences with those coded with MPEG-4 Part 2 codec. Results of the subjective quality evaluation show that on the bit rates below 640 kb/s the H.264/AVC codec has achieved an obviously higher video quality, ensured by the objective metrics as well. On the bit rates higher than 640 kb/s the subjective quality of sequences coded by MPEG-4 Part 2 is close to the quality of H.264/AVC coded video, confirmed only by the SSIM and local_PSNR results.

IPv6 Security Threats and Possible Solutions

In comparison to IPv4, IPv6 provides many improvements considering simplicity, routing speed, quality of service and security. IPv6 brings significant improvements in mechanisms for assuring a higher level of security and confidentiality of the transmitted information. Nevertheless, it is still necessary to take care of network security. This paper analyzes how actual security threats and different types of attacks affect IPv6 networks. IPv6 specific security issues and issues due to different transition mechanisms are also analyzed. Certain security tests have been done and their comments have been given. Finally, some possible solutions for a number of security threats in IPv6 networks have been given.

IPv6 security: improvements and implementation aspects

IPv6 provides many new possibilities and features and also enables significant improvements in confidentiality of information transmitted through the network. Many modifications implemented in IPv6 are expected to directly or indirectly improve security environment for devices connected to both public and private networks. Security features developed for IPv6 are known as IP Security (IPsec). This protocol assures a certain level of security, but does not solve all existing security issues. In this paper methods for network security improvement by implementation of firewalls and intrusion detection systems were analyzed. Furthermore, the methods for ensuring privacy in IPv6 were evaluated and available tools were analyzed. Security tests were done and comments of their results were given. Finally, suggestions about network security improvement and implementation of security mechanisms in IPv6 networks were given.

User authorization system using ZigBee WSN and AVR architecture

This paper shows a development of an RFID (Radio Frequency IDentification) user authorization (access control system) using wireless ZigBee communication network. The system is designed with the topology of one Master and multiple Slave nodes. Idea is to manage a data base on the Master node which is connected to the Slave nodes through a wireless link. Slave node consists of an RFID reader, LCD touch screen and XBee wireless module. Master node communicates with the LabView application through an Ethernet interface. A program development is shown for both nodes, including all the peripheral modules. The proposed systems major advantage over the existing systems is wireless communications. Wireless network uses XBee wireless modules and can be formed as a mesh network, where an end node server as a router, thus extending the range of the network.

Towards an energy efficient SoC computing cluster

High performance computing (HPC) systems are omnipresent in processing huge amounts of data. However, power consumption of these systems is becoming far from negligible, forcing software developers and hardware providers to deviate from usual performance plans, and to address power consumption and costs. As a result, small-scale applications are becoming infeasible to run on those systems, making room for the power-efficient HW newcomers, such as SoC (System on Chip), to take that role. The idea of composing a large number of small SoCs in a computing cluster can result in a powerful, green, and a simple platform capable of delivering enough performance for the small applications while maintaining low energy consumption and costs. In this paper we present a system composed of four LAN-interconnected dual-core ARM based SoC devices, powered by a single power supply. We investigate applicability of such a system by monitoring its performance and energy efficiency and stability while using common HPC paradigms: message passing and thread programming.

Quality of Service in Wireless Sensor Networks: A Survey and Related Patents

Rapid advances in Wireless Sensor Networks (WSNs) indicate that they are becoming increasingly complex. Consequently users and applications are becoming more demanding. Due to unique characteristics of WSNs, like small dimensions and limited resources and capabilities, Quality of Service (QoS) is imposed as one of the key factors of WSNs. In this paper, we surveyed two main approaches for QoS provisioning in WSNs: layered and cross-layer approach. QoS provisioning with layered approach is surveyed in three WSN layers: MAC, network and transport layer. Current developments show that they can be efficiently used for QoS provisioning. However, they consider QoS only as layer specific isolated set of problems and they are highly dependent on the performance of other layers. Cross-layer approach does not have the restrictions as layered approach and hence can dispose with information from all layers of the communication protocol stack. Although it has huge potential to become the most efficient solution for QoS provisioning in WSNs, current development indicate that there are still many issues and challenges that need to be overcome. Since the concept of the QoS is relatively new in WSNs, there are not a large number of patents currently dealing with this issue, however but in coming years a large increase in the number of such patents is expected. Available patents in this domain are described in the paper.

Applications classification and QoS requirements

The applications and network services are key points that could provide the user the necessary quality of service. It is very hard to definitely divide the applications and the underlying services to uniquely describe the application and the service classes. This paper tries to comprise different classes of applications into a unique classification. Different standpoints and criteria are included and evaluated The QoS requirements for every defined application class are defined and described. Finally, on the basis of the introduced classification the required service classes for serving such classes are defined.

Influence of Node Deployment Parameters on QoS in Large-Scale WSN

Quality of Service (QoS) support in large-scale Wireless Sensor Networks (WSNs) is becoming a hot topic in WSN area of research, primarily due to the fact that very complex problems need to be solved using resource constrained WSN nodes. On the other hand, with the large number of nodes in a network, a collective intelligence approach comes into focus for solving various issues. However, as node density and number increases various related problems comes into focus, such as increased RF interference on physical layer, large number of hops in data routing and the overall coverage area issue. All of these parameters are the result of WSN node deployment strategy and their influence on QoS cannot be neglected. To analyze this problem the paper simulated the behavior of large-scale WSN (up to 1000 nodes using OMNeT++) randomly deployed over an area of interest, based on deployment parameters (coverage area, number of nodes and TX power) and in respect to QoS metrics. From simulation results it can be concluded that deployment parameters substantially affects the QoS that a network can support. By choosing optimal deployment parameters it is possible to maximize QoS in a network.