فهرست مطالب

Information and Communication Technology Research - Volume:3 Issue: 4, Autumn 2011

International Journal Information and Communication Technology Research
Volume:3 Issue: 4, Autumn 2011

  • تاریخ انتشار: 1390/11/26
  • تعداد عناوین: 7
|
  • Payam Hanafizadeh Page 1
    To benefit from the advantages of information society on one hand, and afraid of being left further behind of Global Society and increasing in the digital divide on the other hand, stimulating countries to become inclusive Global Information Society. These issues have led policy makers to move towards such society by identifying the objectives, goals and targets. Planning for achieving these objectives needs a real understanding of current situation that can be obtained by information society measures. There has been a proliferation of information society measures in recent years that each of them follows a certain objective. This paper elaborates and categorizes these measures that help scholars and policy makers to 1) select the measures that fitted with their objectives, 2) prevent the repetitive researches, 3) identify the defects and flaws of previous measures and correct them in their own measures, 4) use the experiences of previous measures for constructing their own ones. In this paper, e-measures are classified in three categories: Digital Divide, E-Readiness, and Core ICT Indicators. The categorization of e-readiness measures are based on definitions of e-readiness, objectives, methods and results. Also, digital divide measures are categorized based on potential factors that include cross-sector and cross-construct validation studies.
    Keywords: core ICT indicators, digital divide, e, readiness, information society measures
  • Mehran Javani, Amir Masoud Eftekhari Page 13
    Today, with the advent of digital imagery, the volume of digital images has been growing rapidly in different fields. So, there is an increasing need for providing an effective image retrieval system. In this paper, a semi-supervised k-means clustering method was introduced for image database clustering and image annotation. One of the most important parts of image clustering algorithms is to determine similarity of the images. To compute exact similarity measures, a new CM similarity measure was proposed here to make normalized and weighted features simultaneously so that similarity measure exploits normalized or weighted features in its formula to reach better performance. However, due to semantic gap, some images may be false clustered. A hybrid of three relevance feedback (RF) schemes was used to improve the accuracy of image clustering. (1) The images with the user who knows their irrelevance to a cluster were conducted to correct cluster by a long-term RF. (2) With regard to the images with the user who knows they are relevant to a cluster, feature weight of the clusters was estimated in order to provide a multiple similarity measure using a re-weighting RF. (3) To discover the exact place of the cluster centers, a cluster center movement (CCM) RF was used. Experimental results based on the Corel database including 1000 images and a satellite image database of Tehran city including 2400 images demonstrated the superiority of the proposed method in image database clustering.
    Keywords: Image retrieval, Relevance feedback, Image annotation, Image database clustering, Similarity measure
  • Navid Tafaghodi Khajavi, Siavash Sadeghi, Seyed Mohammad-Sajad Sadough Page 27
    Cognitive radio technology has been proposed as a key solution for the problem of inefficient usage of spectrum bands. Spectrum sensing is one of the most important issues in each cognitive radio system. Classically-used spectrum sensing techniques require that the cognitive transmitter is not in operation while detecting the presence/absence of the primary signal during the sensing period. In this paper, we propose to use blind source separation algorithms such as Kurtosis metric, STFD and TALS with the aim of improving the accuracy of conventional spectrum sensing techniques based on blind source separation. Using blind source separation algorithms, cognitive radio can sense a specific spectrum band while sending its own data in this band. We also introduce a new spectrum sensing framework that combines blind source separation with conventional spectrum sensing techniques. In this way, spectrum sensing can continue to work even when the cognitive transmitter is in operation. Simulation results provided in terms of receiver operating characteristic (ROC) curves indicate that the proposed method also improves the sensing performance achieved with conventional spectrum sensing techniques.
    Keywords: Spectrum Sensing, Cognitive Radio, Blind Source Separation, Random Matrix Theory
  • Vahideh Vakil, Mehdi Rahmati Page 37
    In this paper, adaptive modulation is implemented for a selection combining Demodulate and Forward Relay system. In this method, the source and relay select the modulation type based on the channel quality measurement, which is the output SNR, to improve the total throughput of the system. The adaptation thresholds are computed by solving an optimization problem. The model is generalized for the N-relay system and the optimization problem is modified for this case. Adaptive modulation is then employed for the N-relay DMF system. Adaptive relaying method is also proposed for adaptive modulated DMF system to achieve BER constraint, attain maximum possible throughput and reduce the complexity of hardware. Another optimization problem and several novel algorithms are generated in this paper, to perform adaptive relaying adaptive modulated DMF system. The results demonstrate that employing the proposed methods improves the total throughput of the system by keeping the BER performance at the target level.
    Keywords: Adaptive modulation, Adaptive relaying, Cooperative communication, Demodulate, Forward Relay, Selection combining
  • Mohammad Hossein Yaghmaee Moghaddam Page 45
    Congestion is an essential problem in Wireless Sensor Networks (WSNs). It not only wastes the scarce energy due to a large number of retransmissions and packet drops, but also hampers the event detection reliability. Thus, to meet the Quality of Service (QoS) requirements for network applications, a reliable and fair transport protocol is mandatory. For some applications however, such as in wireless multimedia sensor networks, having a 100% packet delivery ratio is not necessary. In this paper, we present PCC-PRG, a Priority Based Congestion Control and Partial Reliability Guaranty protocol for wireless multimedia sensor networks. The proposed PCC-PRG protocol can be used for partial order services in WMSNs. PCC-PRG uses the maximum queue length of intermediate nodes to detect and notify congestion in the network. PCC-PRG protocol uses a rate control mechanism to adjust the transmission rate of each traffic flow based on the congestion degree in the network and also the flow priority. All transmitted packets are classified into two different priority groups: high and low. Only lost high priority packets are retransmitted. To use a node’s energy efficiently, we use a hop-by-hop NACK-based reliability guaranty model. Simulation results confirm the superiority of the proposed model.
    Keywords: Wireless Multimedia Sensor Networks, Congestion Control, Reliability, Transport Protocols, Rate based control
  • Mohammad Moghaddam, Nasser Masoumi Page 59
    In this paper the sensitivity of on-chip interconnects to Si CMOS process parameters in two different test structures are reported; two coupled lines with shielding, and without shielding. Simulations are performed using HSpiceRF to emulate the state-of-the-art and the future technologies for the test structures. Some important parameters characterizing the coupled interconnects have been examined. Shielding effectiveness on crosstalk reduction is computed using HSpiceRF simulation results in order to compare the efficiency of shielding structures with different process parameters. Additionally we investigate the influence of the process parameters in deep sub-micron technologies on the transmission, reflection, near-end, and far-end crosstalk characteristics of the coupled interconnect with and without the presence of shielding lines.
    Keywords: Interconnects, Shielding, Sensitiviy Analysis
  • Nasim Nourafza Page 65
    Sugarscape model is a multi-agent environment used for modeling and organizing processes such as social, political and economic processes. The purpose of this study is to assess the learning ability of a learner system in sugarscape and for that reason the Boltzmann machine learning algorithm is evaluated. During the first experience, model number 1 which is a learned multi-agent model and is based on Boltzmann machine algorithm was considered. In this model each agent, was assigned with a parameter which indicates the agent’s knowledge. Once the knowledge of agents reached the maximum, the model is converged. The criterion was time of convergence. After that, the second model which is a multi-agent, cellular, and learner based on Boltzmann machine learning algorithm was considered, in which the Boltzmann machine’s learning algorithm is implemented in a multi-agent cellular environment. And finally the third model which is a multi-agent, cellular, Boltzmann machine learner model was assessed in sugarscape. And measure the time needed to reach convergence over specific number of agents for each model. After investigating the resulting diagrams it was concluded that the convergence speed of third model is more than the convergence speed of second model. Also, the convergence speed of second model is more than convergence speed of first model. Utilization of cellular automata results in a more speedy convergence for the model and this is due to rules and local interactions and transformation of generalized convergence to localized convergences. Application of sugarscape accelerates convergence speed relative to the case when it is not used. Additionally the maximum number of executable agents in third model is more than second model and also the maximum number of executable agents in second model is much greater than the first model. At last, it was deduced that the learning process of a learned multi-agent system and in sugarscape speeds up this process and does not have the limitations in the number of agents during execution.
    Keywords: multi, agent system, learning, Boltzmann Machine learning algorithm, cellular automata, sugarscape, convergence