In this paper, we introduce a multiresolution watermarking method for copyright protection of digital images. The method is based on the discrete wavelet transform. A noise type Gaussian sequence is used as watermark. To embed the watermark robustly and imperceptibly, w More
In this paper, we introduce a multiresolution watermarking method for copyright protection of digital images. The method is based on the discrete wavelet transform. A noise type Gaussian sequence is used as watermark. To embed the watermark robustly and imperceptibly, watermark components are added to the significant coefficients of each selected subband by considering the human visual system (HVS) characteristics. Some small modifications are performed to improve HVS model. The host image is needed in watermark extraction procedure and Normalized Correlation Function (NCF) is used to measure similarities of extracted watermarks. It is shown that this method is robust against wide variety of attacks such as: additive noise, low pass filtering, compression, chopping, histogram equalization, rotation. Comparison with other methods shows the better performance of this suggested method.
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In the design of mobile cellular networks, the option of methods for location management of mobile users and updating this location is very important. In general, numerous methods of location management could be classified in two different categories named static and dy More
In the design of mobile cellular networks, the option of methods for location management of mobile users and updating this location is very important. In general, numerous methods of location management could be classified in two different categories named static and dynamic. Analysis and studies show that the second category imposes less computational load onto network. One of the algorithms in dynamic case is based on distance which has better performance compared to other algorithms which are based on time or movement. The important point in this technique is the calculation of cellular distance by mobile unit (MS). Because MSs could receive only cell codes or cell identification (cell ID) by BTSs, in this technique the mobile unit should be able to calculate the cellular distance from these codes (ID). In this paper the authors propose a method for cell ID assignment based on real geographic location of BTS in GPS system. The achieved IDs are then used for applying the distance based method for location management. We have also tested the performance of this method by simulation of a real cellular network in city of Yasuj, province of Kohkiluyeh in Iran.
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