Informatics Publishing Limited

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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M. Lakshmanan ¹, V. Noor Mohammed ¹, S. Nandakumar ¹

Affiliations
1 School of Electrical Sciences of VIT University, Vellore–632014, TamilNadu, IN

Abstract

Computational complexity and error propagation phenomenon are important drawbacks of existing Decision Feedback Equalizers (DFE) for dispersive channels. A new Iterative Block DFE (IBDFE) is considered where the equalization is performed iteratively on blocks of received signal in the frequency domain i.e. both signal processing and filter design are in frequency domain. Thus computational complexity is reduced and error propagation is limited to one block. The feed forward and feedback filters of DFE are designed with the minimization of Mean Square Error (MSE) at detector input as the parameter for effective detection. Two design methods have been solved and simulated for a Rayleigh fading channel. Channel is assumed to be time in-variant during one block of data (128 symbols) transmission. In the first method, the hard detected data are used as the input to the feedback, and filters are designed according to the correlation between detected and transmitted data. In the second method, the feedback signal is directly designed from soft detection of the equalized signal at the previous iteration. Estimates of the parameters involved in the FF and FB filters are also solved and used to evaluate the filter coefficients. From simulation, it was found that the IBDFE as claimed in the research literature performs better than the time domain DFE.

Keywords

DFE, IBDFE, OFDM and Raleigh Fading Channel.

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D. Sumathi ¹, T. Velmurugan ², S. Nandakumar ², S. Renugadevi ²

Affiliations
1 School of Information Technology & Engineering, VIT University, Vellore, TamilNadu, IN
2 School of Electronics Engineering, VIT University, Vellore, TamilNadu, IN

Abstract

Objectives: Consolidating any two dissimilar networks leads to a formation of a heterogeneous wireless network. Vision to achieve distinct networks to get converged such that characterizing of the upcoming wireless networks becomes a reality. This in turn ushers in vertical handoff such that handoff among different technologies is efficient. And at the same time it is so smooth that naming it as seamless is justifiable. Pragmatic consideration of the network characteristics and the dynamics are very essential to choose one of the best available network handoff decisions. Methods: Stating conventionally, when a mobile client is roaming, a single criterion- for example, received signal strength is employed to realize the vertical handoff. But, single criterion consideration is not sufficient and taking into account of other parameters is needed for a proper handoff decision. The present paper puts forth a strong load balancing algorithm M-OPTF that is based on dynamic weight assignment technique for allocation of fresh calls and handoff calls. Findings: In the present scheme assignment of weight factor is done to attachment points basing on the distribution of load on them. In addition it contains a process for handoff decision that takes into account the velocity of mobile node to do triggering of handoff. The put forth M-OPTF algorithm is compared along with Remote Sensing Systems (RSS) and OPT-F algorithm in this paper. Application/Improvements: The simulation results confirm the fact that M-OPTF algorithm apart from balancing the network load it can effectively decrease congestion in network, reduce the number of handoffs that are unnecessary, and increases the battery life time, thus improve the overall performance of the system.

Keywords

Dynamic Weight Assignment, Load Balancing, Unnecessary Handoffs, Velocity; Vertical Handoff, Weight Factor.

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S. Nandakumar ¹, T. Velmurugan ¹, K. S. Preetha ¹, T. R. Suresh Kumar ¹

Affiliations
1 School of Electronics Engineering, VIT University, Vellore, TamilNadu, IN

Abstract

Background/Objectives: Next generation heterogeneous network will comprise multi access systems with multiple service support. Call management scheme is necessary to provide low call dropping probability for high priority services. Call management scheme for mixed cells (i.e., a 4G cell with embedded WLANs) increase cellular system capacity and reduce dropping probability of cellular-to-WLAN vertical handoff calls. Methods: We propose an efficient call management scheme which considers all possible vertical handoff scenarios and provides the maximum usage of WLAN. A blocked request in WLAN is taken back by the overlaying cellular system, if channels are available. Several existing models do not reflect the effect of configuration of neighbor cells which is important for cell planning for a cellular operator. Findings: Call management scheme is executed by diverting every request of WLAN that was blocked, to cellular system. Improvements/ Applications: The proposed call management scheme shows that new call and handoff call dropping probability is decreased when compare with Complementary-WLAN scheme (C-WLAN) and also increases in system throughput.

Keywords

Blocking and Dropping Probability, C-WLAN, Call Management Scheme, WLAN.

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C. P. Ravindran , S. Nandakumar

Abstract

Distribution of metabolites in the developing fruits of Solanum mammosum was investigated by analysing and estimating the dry matter, primary metabolites such as sugars, starch, protein, amino acids and secondary metabolite solasodine. Fruits of different growth phases sampled at 5 comparable stages- starting from post anthesis to ripened stages were analysed by separating the fruit parts such as outer/ inner flesh and seeds. During fruit development III stage showed colour change of fruit wall, mucilaginous and chlorophyllous inner flesh and significant qualitative changes of metabolites. The role of primary metabolites in general and free amino acids and sugars in particular in the synthesis of solasodine in the developing fruits is discussed. 

Keywords

Solanum mammosum, fruit, metabolites, solasodine

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