Informatics Publishing Limited

P. Sai Kiran ¹, L. S. S. Reddy ²

Affiliations
1 Department of Computer Science and Engineering at Lakireddy Bali Reddy College of Engineering, Mylavaram, IN
2 Lakireddy Bali Reddy College of Engineering, Mylavaram, IN

Abstract

Head of Line blocking phenomenon is common in First in First Out (FIFO) nature queues. Head of line blocking problem becomes significant in wireless ad hoc networks using directional antennas as it uses FIFO queue which consists of packets intended for different directions. A packet on the top of the queue may block the remaining packets if it finds the medium busy in its intended direction, where as the packets in the queue intended for other directions may find the medium to be idle. In this paper we propose a method to address the Head of Line blocking problem that can be used for Medium Access Control protocol for wireless Ad Hoc networks using Directional Antennas. The present proposal is about processing the data packets in the queue ready for transmission in other directions when the data packet on top of the queue finds the channel busy in its intended direction. This method is independent of mechanisms used for sensing and transmission by a MAC protocol for directional antennas thus can be part of any MAC protocol using directional antennas with out much change to the protocol. We propose Individual queues for each beam direction and also propose to transmit all the packets waiting at a time once the medium is idle in the intended direction. Our results indicate that the method outperforms other methods proposed for avoiding head of line blocking while increasing throughput and reducing the end-to-end delay.

Keywords

Directional Antennas, Head of Line Blocking, Medium Access Control, Ad Hoc Networks.

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P. Sai Kiran ¹, L. S. S. Reddy ²

Affiliations
1 Department of Computer Science and Engineering at Lakireddy Bali Reddy College of Engineering, Mylavaram, IN
2 Lakireddy Bali Reddy College of Engineering, Mylavaram, IN

Abstract

Directional antennas usage for Medium Access Control (MAC) in Wireless Ad hoc networks has received much attention from researchers as it provides advantages like reduces signal interferences, increase in throughput and better channel reuse. Directional Antennas poses many challenges to be addressed while providing advantages in wireless ad hoc networks like Hidden terminal problems, Deafness, Deaf zone and head of line blocking problem. We observed the existing protocols does not address all the issues and found no protocol that had addressed all the issues. In this paper we propose S-MAC protocol for medium access control in wireless ad hoc networks using directional antennas. S-MAC uses dual channel approach and maintain separate queue for each beam direction. In S-MAC, we address all the challenges imposed by directional antennas and provide a solution to overcome or eliminate the issues. We observed S-MAC outperforms other protocols in terms of throughput while addressing all the issues.

Keywords

Wireless Ad Hoc Networks, Directional Antennas, Medium Access Control, Deafness, Deaf Zone, Head of Line Blocking.

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N. Venkatram ¹, L. S. S. Reddy ², P. V. V. Kishore ³

Affiliations
1 KL University, ECM Dept., Green Fields, Vaddeswaram, Guntur DT, IN
2 KL University, CSE Department, IN
3 ECE Department, KL University, IN

Abstract

Medical image watermarking (MIW) has challenged researchers for over a decade now. Medical images are difficult to watermark as they contain sensitive information of a patient’s disease. During transportation through internet the medical images are subjected to various attacks. For telemedicine applications it becomes vital to prevent the authenticity regarding patient’s records. A two dimensional discrete wavelet transform based approach is designed and tested to embed a patient passport photograph into his or her medical image. This method computes 2D DWT at various levels and mixes the approximate coefficients using a wave coupling coefficient. The proposed watermarking algorithm is tested for available mother wavelets and around five levels of decomposition with multiple coupling coefficients. Peak Signal-to-Noise ratio, Minimum Mean Square Error and Normalized cross correlation coefficient are computed to identify the best wavelet and the level of decomposition that can significantly be applied to medical image watermarking. The results demonstrate that db2 at level 4 is the top performing wavelet.

Keywords

Medical Image Watermarking, 2D Discrete Wavelet Transform, Wave Coupling Coefficient, Peak Signal-To-Noise Ratio, and Minimum Mean Square Error.

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M. Sreedevi ¹, L. S. S. Reddy ²

Affiliations
1 Department of Computer Science and Engineering, K. L. University, Guntur, Andhra Pradesh, IN
2 Department of Computer Science and Engineering, LBR College of Engineering, Mylavaram, Andhra Pradesh, IN

Abstract

Mining regular patterns in data streams is an emerging research area and also a challenging problem in present days because in Data streams new data comes continuously with varying rates. Closed item set mining gained lot of implication in data mining research from conventional mining methods. So in this paper we propose a narrative approach called CRPDS (Closed Regular Patterns in Data Streams) with vertical data format using sliding window model. To our knowledge no method has been proposed to mine closed regular patterns in data streams. As the stream flows our CRPDS-method mines closed regular itemsets based on regularity threshold and user given support count. The experimental results show that the proposed method is efficient and scalable in terms of memory and time.

Keywords

Data Streams, Regular Patterns, Closed Regular Patterns, Transaction Sliding Window.

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