Zarko Cucej

Using RSSI value for distance estimation in wireless sensor networks based on ZigBee

In todaypsilas modern wireless ZigBee-based modules, there are two well-known values for link quality estimation: RSSI (received signal strength indicator) and LQI (link quality indicator). In respect to wireless channel models, received power should be a function of distance. From this aspect, we believed that RSSI can be used for evaluating distances between nodes. The experiment described in this paper indicates that RSSI is, in fact, a poor distance estimator when using wireless sensor networks in buildings. Reflection, scattering and other physical properties have an extreme impact on RSSI measurement and so we can conclude: RSSI is a bad distance estimator.

Autobinomial Model for SAR Image Despeckling and Information Extraction

This paper presents a model-based despeckling (MBD) of synthetic aperture radar (SAR) images using Bayesian analysis. The SAR image is despeckled using first-order Bayesian inference. The novelty in this paper is an autobinomial model (ABM), which models a prior probability density function (pdf); meanwhile, the likelihood pdf is modeled as a gamma distribution. Analytically, a solution for a maximum a posteriori estimate using an autobinomial prior cannot be computed; therefore, an approximation is introduced using differential. The best ABM for approximating the texture parameters in SAR images is found by using second-order Bayesian inference. The edges in the SAR images are detected using region borders, which have statistically different properties. Coefficient of variation is used to distinguish between homogeneous and heterogeneous areas. The experimental results show that the proposed method preserves the textural features and removes noise significantly in the homogeneous and heterogeneous regions. The proposed despeckling method is good regarding objective measures for synthetic images and better despeckles the real SAR images, when compared with the state-of-the-art MBD methods.

The Accuracy of Propagation Models for Distance Measurement between WSN Nodes

The accuracy of RF propagation models for distance measurement between WSN nodes using received signal strength indicator (RSSI) was studied. We implemented two simple propagation models, the free space log-normal model and 2-ray ground reflection model. The results show, that first model is not very precise in closed space (rooms). The second model gives quite well agreement with experimental RSSI measurements for greater distances between transmitting and receiving nodes.

Soil Moisture Estimation Using High-Resolution Spotlight TerraSAR-X Data

High-resolution and dual polarized Spotlight TerraSAR-X images are assessed for soil moisture parameter retrieval. This letter presents bare soil moisture estimation and estimation of moisture of vegetated areas. The bare soil moisture estimation is based on the Shi model. The Minimum Mean Square Error approach is used to determine the unknown parameters of the Shi model using ground measurements of volumetric moisture and SAR data. The soil moisture of vegetated areas is estimated using the vegetation and soil backscattering coefficients. The unknown parameters of vegetation and soil backscattering models were estimated using Tikhonov optimization. The experimental results showed that the used models provide good results for estimating bare soil moisture and moisture of vegetated areas.

Progressive space frequency quantization for SAR data compression

The authors propose a new wavelet image coding technique for synthetic aperture radar (SAR) data compression called a progressive space-frequency quantization (PSFQ). PSFQ performs spatial quantization via rate distortion-optimized zerotree pruning of wavelet coefficients that are coded using a progressive subband coding technique. They compared the performances of zerotree-based methods: EZW, SPIHT, SFQ, and PSFQ with the classical wavelet-based method (CWM), which uses uniform scalar quantization of subbands followed by recency rank coding. The performances of the methods based on zerotree quantization were better than the CWM in the rate distortion sense. The embedded coding techniques perform better SNR results than the methods using scalar quantization. However, the probability density function (PDF) of the reconstructed amplitude SAR data compressed using CWM, better corresponded to the PDF of the original data than the PDF of the reconstructed data compressed using the zerotree based methods. The amplitude PDF of the reconstructed data obtained using PSFQ compression algorithm better corresponded to the original PDF than the amplitude PDF of the data obtained using the multilook method.

A new goodness of fit test for histograms regarding network traffic packet size process

Contemporary communication is becoming more and more complex and extensive. Network planners very often use simulations tools for reducing the costs of planning, constructions, and maintenances. Modeling network traffic is also a very important challenge regarding simulation tools, especially the modeling of measured traffic as to which would be the best approximation of measured traffic in real network. This is possible to ensure using the accurate descriptions of two random processes, both of which define network traffic. These two random processes are packet size process and inter-arrival time. In stochastic modeling both of these processes are modeled using probability distributions. The parameters of these distributions are estimated in an empirical manner with the help of histograms regarding measured traffic processes. Any accuracy regarding suitable distribution between distribution and histogram can be evaluated using different tests, such as Kolmogorov-Smirnov or Chi-square. However, during the measurements and modeling of measured network traffic these tests show one weakness in the case of trying to model network traffic, in regard to the best approximation of measured traffic in bit and packet-rates at the same time. So we have developed a new and better goodness of fit test of network traffic, which considers the number of packets and also the packetpsilas size. Using simulations we show, that the use of this new more suitable test leads to better choice regarding distribution when describing a packet size process, which than consequently, also lead to smaller discrepancies between measured and simulated traffic in bit and packet-rates.

Modeling methods in OPNET simulations of Tactical Command and Control Information Systems

Slovenia is a member of MIP (multilateral interoperability programme), the task of which is to provide interpretations of national C2IS systems for successfully harmonizing joint action by international military peacekeeping forces. Interpretability within MIP is carried-out by a unified model based on controlled data replication between the databases of C2IS systems. Systematics IRIS replication mechanism software (IRM) is used for data replication. This paper presents methods of measuring and analyzing traffic that causes IRM. We designed an OPNET model on the basis of the analyzed results that would be suitable for the purposes of tactical radio network simulation.

Packet size process modeling of measured self-similar network traffic with defragmentation method

Analysis and modeling of telecommunication networks by simulations has become one of the main tools in the process of telecommunication-networkspsila planning and upgrading. Knowledge regarding the statistical modeling of network traffic is very important. Here we tend towards modeled network traffic which would be the best possible approximation of the measured traffic. Throughout our research in the field of self-similar network traffic we have faced problem of statistically describing the packet-size process. We have noticed that small discrepancies between measured histograms and estimated probability density functions, as used in traffic generator models, lead to large discrepancy between measured and modeled network traffics. In this research we tried to estimate the probability density function of a measured histogram for process-packet size, in such way that would decrease these discrepancies. For this purpose, we have developed a novel method of modeling network traffic, which is based on the defragmentation of measured traffic. Using this defragmentation method, we can estimate parameters of filespsila size process, from captured packets and use these statistical parameters for traffic generation, via the OPNET simulation tool. From these simulations, we can show that this newly-developed method decreases discrepancy between packet size process histograms of measured and simulated network traffics. This consequently leads to a decrease in discrepancy between measured and simulated network traffics.

Wavelet Based Multiscale Edge Preserving Segmentation Algorithm for Object Recognition and Object Tracking

Although edge detection is basic task in computer vision, its results are very important for further procedures. In order to make task of finding edges of objects more efficient, a novel approach is proposed. It uses wavelet transform of the image to detect edges and in the same time also to segment edge points. Partial segmentation of the image is performed only around edge points, which in return enables us to preserve found edges, group edges of the same object into clusters and defines shapes of objects, where edges are missing. Because we do not perform segmentation of the whole image, but use only information from segmentation of point around edges, the procedure of finding object shapes is faster and in turn the whole step of object recognition, defined by the shape, is faster.

Real time “system-in-the-loop” simulation of tactical networks

Military mission success probability is closely related to careful planning of communication infrastructures for Command and Control Information Systems (C2IS). Over recent years, the designers of tactical networks have realized more and more need for using simulation tools in the process of designing networks with optimal performances, in regard to terrain conditions. One of the most demanding simulation problems is the modeling of protocols and devices; especially on the application layer, because the credibility of simulation results mainly depends on the quality of modeling. A new branch of communications network simulations has appeared for resolving these kinds of problems the - simulations with real communication devices in the simulation loop. Such simulations initiate real-time into the simulation process. The results of our research are aimed at simulation methodology. Using this system, military command personnel, can perform realistic training on the real C2IS equipment connected to the simulation tool, by modeled wireless links over a virtual terrain. In our research work, we used the OPNET Modeler simulation tool, with additional modules.