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One of the main challenges of scheduling algorithms in Grid environment is the autonomy of sites, which makes it difficult for the grid scheduler to estimate the exact cost of a task execution on different sites. In this paper, we present a solution for this problem based on data history (workload traces) and time series techniques. The main focus of this work is devoted to forecasting the task waiting time in a resource queue, which is under the control of a local scheduler with distinctive scheduling policy. The main contribution of this work is the consideration of a special property of the grid resources, the dynamic membership, i.e. a resource may exit and then come back to the grid environment repeatedly. When the resource belongs to the grid environment, its workload trace (log file) is considered as a correct log. On the other hand, when the resource leaves the grid, the log file during this period is considered as a defective part of the trace. As the defective parts contain some useful information, after repairing these defective parts, they can be used for forecasting purposes. Of this, we employ state-space model along with the associated Kalman recursions in conjunction with the Expectation-Maximization algorithm to repair the defective waiting time series such as a correct log file by which the resource seems never to have left the grid. The experimental results on a number of workload logs demonstrated that this approach can achieve an average prediction error, between 22 and 64% less than those incurred by other rival methods. Copyright and the contention incurred by resource sharing among a potentially large number of users. In traditional parallel and distributed systems, the computational resources are usually managed by a single control unit. The scheduler not only has full information about all running/pending tasks and resource utilization but also manages the task queue and the resources pool. Thus, it can easily predict the behaviors of resources and is able to assign tasks to resources according to certain performance requirements. However, in a grid environment, the resources are usually autonomous and a grid scheduler does not have full control over the participating resources. The grid scheduler makes decisions on behalf of users and offers jobs to the local resource management systems. The goodness of scheduling depends heavily on the quality of available information regarding the resources. However, the grid scheduler is not permitted to violate the local policy of resources, which makes it hard to estimate the exact cost of task execution/processing on different sites. The autonomy also imposes a kind of diversity in local resource management and access control policy such as queuing disciplines, the priority settings of different applications, and the resource reservation methods. Thus, a grid scheduler is required to be adaptive to different local policies. Current scheduling systems adopt three different approaches to alleviate this problem: scheduling based on just-in-time infor...

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With rapid growing of mobile networks and devices we can use them to send email, mobile commerce, theatre booking, etc. In such scenario, we need to Secure Communication. Secure communication is possible through encryption of data. However, most of the existent data encryption techniques are location-independent. Data encrypted with such techniques cannot restrict the location and time of data decryption. The concept of "Geoencryption" or "location-based encryption" is being developed for such a purpose. In this paper, we are going to investigate weaknesses in existing Geoencryption systems and propose some solutions for increase the safety and reliability in these systems. For this purpose we present a new geoencryption protocol that will allow mobile nodes to communicate to each other safely by restrict decoding a message in the specific location and time period. Receiver can only decrypt the ciphertext when the coordinate acquired form GPS receiver matches with the target coordinate. According to our experimental study, the approach can meet the confidentiality, authentication, simplicity, and practicability of security issues. As a result, the proposed approaches can improve the security and confidentiality in Geoencryption systems.

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