Informatics Publishing Limited

K. V. N. Kavitha ¹, Sibaram Khara ¹, J. V. Rama Krishna Reddy ²

Affiliations
1 School of Electronics Engineering, VIT University, Vellore, Tamil Nadu, IN
2 School of Electronics Engineering, VIT University, Vellore, Tamil Nadu, IN

Abstract

We consider Channel estimation for multiple-input multiple-output/orthogonal frequency-division multiplexing (MIMO/ OFDM) systems in time-varying wireless channels using superimposed training (ST). By using a discrete prolate spheroidal basis expansion model (DPSS) and truncated discrete fourier bases expansion models (Fourier-BEM) for representing the time varying channel. Based on these models, a weighted average approach is adopted for estimating linear time varying (LTV) channels for OFDM symbols. The performance analysis between two BEM models based on Mean square error (MSE) is present in this paper. Simulation results show that the DPSS-BEM model outperforms the Fourier Bases expansion model.

Keywords

Basis Expansion Models (BEMS), MIMO/OFDM, Slepian Sequences, Superimposed Training.

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Sibaram Khara ¹

Affiliations
1 VIT University, Vellore, Tamil Nadu, 632014, IN

Abstract

Recent trends indicate that many current generation wireless technologies will converge to form next generation heterogeneous wireless networks (such as fourth generation (4G) network) to provide multimedia services through multi-mode mobile devices. Third generation (3G) cellular data networks (such as Universal Mobile Telecommunication System (UMTS)) and wireless local area network (WLAN) are two potential constituents to form 4G wireless heterogeneous networks. However, UMTS and WLAN systems are technologically different and are not designed to work together. UMTS/WLAN integration needs seamless interworking strategies between the two technologies not only at access level but also at both core and service levels. The design complexity and implementation implications, cost effectiveness and efficiency of the integrated network need to be considered for optimal solutions. In this article, we present the feasible UMTS/WLAN integration techniques. We compare among various solution techniques and observe that at lower protocol layer of UMTS, WLAN can be managed with UMTS-like access network but it increases implementation complexity.  On the other hand, at IP and upper layer convergence help simple integration but it provides larger handoff delay. Our   ns-2 based simulation results show that vertical handoff delay in loose coupling, is 19% more than that in tight coupling architecture. But end-to-end  packet delay in loose coupling is 6% less.

Keywords

UMTS/WLAN Integration, Handoff, Loose Coupling, Tight Coupling.

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T. Velmurugan ¹, Shasi Shekar Singh ², S. Nandakumar ³, Sibaram Khara ³

Affiliations
1 School of Electronics Engineering, VIT University, IN
2 VIT University, IN
3 School of Electronics Engineering, VIT University, and Tamilnadu, IN

Abstract

TCP is designed to perform in traditional wired networks where packet losses occur mainly due to network congestion. Wireless link losses result in poor TCP throughput since losses are perceived as congestion and TCP responds to all such losses by invoking congestion control and avoidance algorithms. Wireless link loss also incurs source throttling and hence degraded end-to-end performance. Wireless link designers have augmented mobile TCP a modified version of TCP to suit wireless conditions. But this mechanism has reduced the impact of losses on TCP throughput for smaller file transfer. In this paper, we propose an enhanced mobile TCP scheme for performance improvement for both smaller and larger file transfer over wireless link. OPNET based simulation results shows that proposed scheme improves TCP throughput by 60% over existing solutions.

Keywords

HTTP, M-TCP, SMSS INTRODUCTION.

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Kishore V. Krishnan ¹, Sibaram Khara ², A. Bagubali ¹, Varun Chawla ¹, Krishna Ashok ¹

Affiliations
1 VIT University, Vellore - 632014, Tamil Nadu, IN
2 Galgotias University, Noida - 201310, Uttar Pradesh, IN

Abstract

Objectives: Underground mine communication is the most vital factor today to monitor different parameters continuously and to take necessary actions accordingly to mitigate all hazards that happen inside mines. Accidents in coal mines occur due to inadequacy of information from the mine environment due to inefficiency of existing phone systems. Methods/ Statistical Analysis: In this paper, cognitive radio technology is used in underground coal mines to wirelessly transmit crucial parameters such as temperature, humidity and methane gas levels to enhance the safety and security of coal mine workers. To depict cognitive radio, two communication channels, Bluetooth and RF have been used. These wireless channels are used to transmit data from the hardware circuit fitted on the miner’s gear to the ground control center. Findings: To test the working of proposed technique it is subjected to several test cases. Experiments have proved feasibility and good stability of the system. Using the proposed technology the network sensor scalability has been improved. Application/ Improvements: The deployment of a module of cognitive radio sensors is made on the miner’s gear to monitor the aforementioned parameters. Various traffic issues like routing algorithm, handoff problems are identified as the extension of the proposed cognitive radio networks.

Keywords

Cognitive Radio (CR), Coal Mine, Monitoring System, Personal Protective Equipment (PPE), Tracking and Positioning, Wireless Sensor Networks (WSNs).

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