Vol 50, No 3 (2016)

Problems of the development of hybrid communication systems based on laser and radio wave technologies are discussed. A novel method for assessing the reliability characteristics of such systems, operating in random environment, is presented. The method is based on the theory of Markov- modulated processes. An algorithm of stationary distribution calculation for the systems state probabilities is elaborated. Numerical examples illustrate the suggested approach.

Recently, Multimedia cloud is emerging as a promising technology to effectively process multimedia services. A key problem in multimedia cloud is how to deal with task scheduling and load balancing to satisfy the quality of service demands of users. In this paper, we propose a two levels task scheduling mechanism for multimedia cloud to addresses the problem. The first level scheduling is from the users’ multimedia application to the data centers, and the second is from the data centers to servers. The data centers and virtual machines both are modeled as M/M/1 queuing systems. The algorithm proposed formulates the task-scheduling problem as cooperative game among data centers. Then we allocate the tasks received by a data center to servers using cooperative game again among servers. Various simulations are conducted to validate the efficiency of the proposed task scheduling approaches. The results showed that the proposed solutions provided better performance as compared to the existing approaches.

Cloud computing is currently emerging as a promising next-generation architecture in the Information Technology (IT) industry and education sector. The encoding process of state information from the data and protection are governed by the organizational access control policies. An encryption technique protects the data confidentiality from the unauthorized access leads to the development of fine-grained access control policies with user attributes. The Attribute-Based Encryption (ABE) verifies the intersection of attributes to the multiple sets. The handling of adding or revoking the users is difficult with respect to changes in policies. The inclusion of multiple encrypted copies for the same key raised the computational cost. This paper proposes an efficient Key Derivation Policy (KDP) for improvement of data security and integrity in the cloud and overcomes the problems in traditional methods. The local key generation process in proposed method includes the data attributes. The secret key is generated from the combination of local keys with the user attribute by a hash function. The original text is recovered from the ciphertext by the decryption process. The key sharing between data owner and user validates the data integrity referred MAC verification process. The proposed efficient KDP with MAC verification analyze the security issues and compared with the Cipher Text–Attribute-Based Encryption (CP-ABE) schemes on the performance parameters of encryption time, computational overhead and the average lifetime of key generation. The major advantage of proposed approach is the updating of public information and easy handling of adding/revoking of users in the cloud.

Cognitive Radio Network (CRN) is an intelligent wireless communication system that adapts itself to variations in the incoming radio frequency stimuli by modifying the operating parameters. Using the spectrum sensing techniques, the idle channels are detected, and allocated to the Secondary Users (SUs). The existing cooperative spectrum sensing techniques such as centralized sensing technique, Distributed sensing technique, and External sensing technique exploit efficient prediction models for allocating the frequency spectrum to SUs. For an optimal assignment of the channel using channel parameters, the channel estimation techniques such as pilot-assisted channel estimation, blind and semi blind estimation technique, and decision directed channel estimation technique are analyzed. The flexible nature of the CRN introduces various security attacks such as Primary User Emulation Attack, Objective Function Attack, Jamming Attack, Spectrum Sensing Data Falsification (SSDF), Control Channel Saturation DoS Attack (CCSD), Selfish Channel Negotiation (SCN), Sinkhole Attacks, HELLO Flood Attacks and Lion Attack. From the surveyed results, it is observed that the existing spectrum sensing, and prediction-based techniques consume more energy, and minimal data transmission rate for detecting the idle channel. Further, the end-to-end delay, energy consumption, end-to-end delay, and bandwidth are not minimized by the existing techniques.