Drago Žagar

Foveated mean squared error--a novel video quality metric

Efficiency of a video coding process, as well as accuracy of an objective video quality evaluation can be significantly improved by introduction of the human visual system (HVS) characteristics. In this paper we analyze one of these characteristics; namely, visual acuity reduction due to the foveated vision and object movements in a video sequence. We propose a new video quality metric called Foveated Mean Squared Error (FMSE) that takes into account a variable resolution of the HVS across the visual field. The highest visual acuity is at the point of fixation that falls into fovea, an area at retina with the highest density of photoreceptors. Visual acuity decreases rapidly for image regions which are further with respect to the fixation point. FMSE also utilizes the effect of additional spatial acuity reduction due to motion in a video sequence. The quality measures calculated by FMSE have shown a high correlation with experimental results obtained by subjective video quality assessment.

STFTP: Secure TFTP Protocol for Embedded Multi-Agent Systems Communication

Today’s embedded systems have evolved into multipurpose devices moving towards an embedded multi-agent system (MAS) infrastructure. With the involvement of MAS in embedded systems, one remaining issues is establishing communication between agents in low computational power and low memory embedded systems without present Embedded Operating System (EOS). One solution is the extension of an outdated Trivial File Transfer Protocol (TFTP). The main advantage of using TFTP in embedded systems is the easy implementation. However, the problem at hand is the overall lack of security mechanisms in TFTP. This paper proposes an extension to the existing TFTP in a form of added security mechanisms: STFTP. The authentication is proposed using Digest Access Authentication process whereas the data encryption can be performed by various cryptographic algorithms. The proposal is experimentally tested using two embedded systems based on micro-controller architecture. Communication is analyzed for authentication, data rate and transfer time versus various data encryption ciphers and files sizes. STFTP results in an expected drop in performance, which is in the range of similar encryption algorithms. The system could be improved by using embedded systems of higher computational power or by the use of hardware encryption modules.

Broadband ecosystem elements in techno-economic modelling and analysing of broadband access solutions for rural areas

Encouraged by broadband development initiatives and strategies that aim at the reduction of the existing digital divide between rural and urban European areas by the year 2020, the current situation in the case study of Croatian rural broadband market is analysed, and the possibilities for further broadband Internet access implementation in rural areas are highlighted in the paper within the context of broadband ecosystem elements analysis. Furthermore, in order to address the exisiting digital divide problem, an extended techno- economic modelling process for rural broadband Internet access implementation analyses is proposed. The proposed additional part of model serves as an upgrade for the standard techno- economic models and allows a detailed analysis of the specificities of different rural areas, based on the available data. Finally, the efficiency of the proposed model’s application when choosing the best business strategies for different fixed and mobile, wired and wireless broadband access solutions in rural areas is presented.

Response surface methodology based power consumption and RF propagation analysis and optimization on XBee WSN module

One of the most important issues in wireless sensor networks (WSN) is reduction of power consumption, prolonging the network lifetime (for battery powered networks) or reducing the induced

Dynamic Server Selection by Using a Client Side Composite DNS-Metric

\hbox {CO}_{2}

Application of program agents for optimisation of VoIP communication

CO2 emissions (for grid powered networks). Power consumption reduction can be achieved in various ways: transmitter power control, duty cycling, data reduction and others. This paper analyses the impact of several parameters on power consumption of Digi’s XBee PRO of shelf WSN modules. To determine the conditions for transmitter power control, this paper presents measurement analysis for indoor RF propagation in order to determine the minimum received signal strength for high data transfer reliability. Measurement analysis is conducted using response surface methodology and the conclusions based on the respective measurement results are given resulting in a mathematical model of the node’s power consumption. Also, optimization of power consumption is shown for various parameters using desirability functions, where optimal parameters for minimum power consumption are presented.

Agent Based Architecture for Pricing the Services in Dynamic User/Network Environment

The multi pulse position amplitude modulation scheme for time-hopping multiple access impulse radio ultrawideband communication systems has been presented in this paper. Multi pulse position amplitude modulation is a hybrid modulation technique, which combines multi pulse position modulation and pulse amplitude modulation. It is shown that multi pulse position amplitude modulation significantly outperforms pulse position modulation with respect to bandwidth efficiency. The multi pulse position amplitude modulation error probability over IEEE 802.15.3a multipath fading channels in multiuser environment is derived. The system analysis shows that the proper selection of modulation parameters can improve the system performance at the cost of hardware complexity (and vice versa).

Reliability of Welding Parameters Monitoring System

Dynamic Server Selection (DSS) is a new DNS method for the optimal server selection of a multiple available network service. The method allows dynamic selection of a server on the client side based on the information of the server load and its network topological distance from the client. The server selection is based on the calculations of a composite DNS-metric in which servers, whose IP addresses are sent in a DNS response, are ranked from the optimal to the least suitable. Calculation parameters are server response time, which the client measures for each server independently, and the server load, which is specified by the server administrator. The DSS method has the lowest overall network service response time in comparison with the other four observed methods (Geographical, Hops, Random and RTT) which, in measurements done in a real time environment, have longer response time from 8.5% to 26.8% compared to DSS.