k s Dasgupta

Dhirubhai Ambani Institute of Information and Communication Technology (DA-IICT), ICT, Faculty Member

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Performance Analysis of Proactive and Reactive Routing Protocols for Mobile Ad-hoc Grid in e-health Applications

2009 International Conference on Communication Software and Networks, 2009

ABSTRACT The integration of mobile wireless devices into grids has recently drawn the attention o... more ABSTRACT The integration of mobile wireless devices into grids has recently drawn the attention of research community as this integration has resulted in new challenges. Mobile grid enables the mobility of a requesting user to share unused available resources on a network required in different applications in science, health and education. These handheld devices are not capable to cope with the existing demands of networks and applications. Heterogeneous interfaces, computational power, storage and display differences among these devices demands more research. In this paper we present analysis of different routing protocol’s behavior in a mobile ad-hoc grid environment, where best routing is the requirement of a grid application. These analyses were made based on a test scenario of e-health application in a mobile ad-hoc grid environment.

An Adaptive Multi State Proactive Transport Protocol consisting

Abstract—This paper attempts to establish the fact that Multi State Network Classification is ess... more Abstract—This paper attempts to establish the fact that Multi State Network Classification is essential for performance enhancement of Transport protocols over Satellite based Networks. A model to classify Multi State network condition taking into consideration both congestion and channel error is evolved. In order to arrive at such a model an analysis of the impact of congestion and channel error on RTT values has been carried out using ns2. The analysis results are also reported in the paper. The inference drawn from this analysis is used to develop a novel statistical RTT based model for multi state network classification.

Space Protocols

NASA proposes to develop a common infrastructure for all its forthcoming space exploration missio... more NASA proposes to develop a common infrastructure for all its forthcoming space exploration missions. This infrastructure called the Interplanetary Internet (IPN) will take the Internet of the Earth to outside planets and facilitate in the efficient transfer of the huge amount of scientific data collected by the space probes back to Earth. The development of an efficient transport protocol for the Interplanetary Internet is a major challenge to the research community. In this paper, a survey has been done for all the major transport protocols developed for deep space communication. The paper discusses the infrastructure of the IPN along with the major challenges for deep space communication. Emphasis has been made on the issues of transport protocol design for LEO-GEO based satellite networks and deep space communication networks. The genesis of the work on Interplanetary Internet and the evolution of the concept of Delay Tolerant Networks have been explained. An attempt has been mad...

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A new propagation campaign in tropical areas: The Ka-band propagation experiment over India with the GSAT-4 satellite

An opportunity has been proposed recently by the Space Applications Center (SAC) of the Indian Sp... more An opportunity has been proposed recently by the Space Applications Center (SAC) of the Indian Space Research Organization (ISRO) to carry out a propagation experiment at Ka-band over India. To this purpose, the GSAT-4 satellite will board two propagation beacons at 20.2 GHz and 30.5 GHz in linear polarization. The objective of this paper is to present the GSAT-4 propagation experiment. In a first part, the main objectives of the campaign are described. Afterwards, a presentation of the specifications of the propagation beacons to be boarded on GSAT-4 are given. Finally, the ground segment with all instruments planned to be distributed over India during the campaign are detailed and illustrated with an example of link budget.

Performance improvement of short-length regular low-density parity-check codes with low-complexity post-processing

IET Communications, 2012

It is well known that extremely long low-density parity-check (LDPC) codes perform exceptionally ... more It is well known that extremely long low-density parity-check (LDPC) codes perform exceptionally well for error correction applications, short-length codes are preferable in practical applications. However, short-length LDPC codes suffer from performance degradation owing to graph-based impairments such as short cycles, trapping sets and stopping sets and so on in the bipartite graph of the LDPC matrix. In particular, performance degradation at moderate to high E b /N 0 is caused by the oscillations in bit node a posteriori probabilities induced by short cycles and trapping sets in bipartite graphs. In this study, a computationally efficient algorithm is proposed to improve the performance of short-length LDPC codes at moderate to high E b /N 0. This algorithm makes use of the information generated by the belief propagation (BP) algorithm in previous iterations before a decoding failure occurs. Using this information, a reliability-based estimation is performed on each bit node to supplement the BP algorithm. The proposed algorithm gives an appreciable coding gain as compared with BP decoding for LDPC codes of a code rate equal to or less than 1/2 rate coding. The coding gains are modest to significant in the case of optimised (for bipartite graph conditioning) regular LDPC codes, whereas the coding gains are huge in the case of unoptimised codes. Hence, this algorithm is useful for relaxing some stringent constraints on the graphical structure of the LDPC code and for developing hardware-friendly designs.

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Multirate Systems in Cognitive Radio

Recent developments in wireless communication services have led to an increase in demand for spec... more Recent developments in wireless communication services have led to an increase in demand for spectrum resources. Moreover, most of the existing wireless networks follow a fixed spectrum assignment policy. A recent report by Federal Communications Commission (FCC) reveals that most of the spectrum is underutilized. Cognitive radios (CR) have proven to be a solution to alleviate the problem of spectrum scarcity by utilizing different spectrum sensing techniques. The detection of spectral holes (unused spectrum) and allocating the available spectrum to secondary users are the challenges in CR. Spectrum sensing can be broadly classified into narrowband and wideband spectrum sensing. In wideband the available bandwidth has to be subdivided into multiple frequency bands. In such scenarios the multirate signal processing using filter banks becomes a possible solution for efficient and reliable spectrum detection. Filter bank-based physical layer design for CR systems was introduced to perf...

Via S Atellite ( DVB-RCS ) H Ub for S Atellite Based E-L Earning

This paper discusses in-house designed and developed scale-down DVB-RCS hub along with the perfor... more This paper discusses in-house designed and developed scale-down DVB-RCS hub along with the performance of the realized hub. This development is intended to support the Satellite Based e-Learning initiative in India. The scale-down DVB-RCS HUB is implemented around a single PC with other subsystems making it very cost effective and unique of its kind. This realization will drastically reduce the total cost of Satellite based Education Networks as very low cost commercially available Satellite Interactive Terminals (SITs) complying to open standard could be used at remote locations. The system is successfully tested to work with a commercial SIT using a GEO satellite EDUSAT which is especially dedicated for satellite based e-Learning. The internal detail of the DVB-RCS Forward and Return Link Organization and how it manages the Satellite Interactive Terminals access to the satellite channel using MF-TDMA approach has been described.

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Design, implementation and realization of 64Kbps  QPSK based burst demodulator for onboard application

2009 International Conference on Emerging Trends in Electronic and Photonic Devices & Systems, 2009

ABSTRACT The Ka band regenerative payload is a transponder of GSAT-4 satellite. It provides Narro... more ABSTRACT The Ka band regenerative payload is a transponder of GSAT-4 satellite. It provides Narrow Spot Beams, Wide Bandwidth and small size of antenna for both transmission and reception. The Signaling Demodulator is a one of the important subsystem of regenerative Payload. This Signaling Demodulator was developed in-house for providing signaling information to provide communication between one spot beam to other. The demodulator software was developed for functionality of getting the signaling request from the user terminal &amp; the processing of the request onboard.

A Proactive Transport Protocol for Performance Enhancement of Satellite based Networks

International Journal of Computer Applications, 2010

Current TCP Protocols have lower throughput performance in satellite networks mainly due to the e... more Current TCP Protocols have lower throughput performance in satellite networks mainly due to the effect of long propagation delays and high link error rates. In this paper a new congestion control protocol for satellite networks is proposed. The protocol uses a proactive approach and is composed of novel ideas like Proactive Slow Start, Proactive Congestion Avoidance and Decision based Error handling policies that are combined with traditional TCP algorithms like Fast Retransmit. The mainstay of our protocol is that the nature of the RTT pattern can give us probable indication of an incipient congestion in the network. This changing pattern of RTT is incidentally used to differentiate between congestion or link error, thus avoiding unnecessary rate throttle. In the initial phase necessary augmentation of ns2 simulator pertaining to the proposed protocol is carried out. This was essential to create a necessary test bed for exhaustive simulation of the protocol considering a GEO network with different congestion level and packet error rate. Simulation results show that the protocol always outperforms other TCP schemes in terms of goodput and in cases an improvement of 80% to 120% is observed especially when the packet error rate is very high. Evaluation of the protocol shows a high fairness property and excellent adaptability to high levels of congestion and errors.

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Concatenated Convolutional Codes for Deep Space Mission

In satellite communication deep space mission are the most challenging mission, where system has ... more In satellite communication deep space mission are the most challenging mission, where system has to work at very low Eb/No. Concatenated codes are the ideal choice for such deep space mission. ISRO is planning to send unmanned mission for Mars and several deep space missions in future to study and detailed understanding of our own universe. This paper basically reviews the concatenated convolutional code structure and selects the suitable candidate for our future deep space mission. The complete simulation using Simulink is done and results are presented in this paper.

Simulation based analysis of RTT with PER, Buffer Size and Congestion Levels for Satellite based Networks

International Journal of Computer Applications, 2012

Round Trip Time values constitute one of the significant parameter available to a TCP sender for ... more Round Trip Time values constitute one of the significant parameter available to a TCP sender for estimating the network conditions. The RTT has a significant effect on the throughput of a connection and creates the performance bottleneck for traditional AIMD TCP Protocol variants mainly when used for GEO satellite networks and other long fat networks. Many Transport Protocols like Vegas, Proactive TCP, and Westwood uses the RTT measurement for adjusting the congestion window and refining the Loss Detection Algorithms, which eventually determines the performance of the Protocol. RTT also appears in the empirical formulation of TCP throughput and protocols based on these empirical estimates. RTT is generally considered an independent parameter mainly dependent on the access delay, queuing delay, and the propagation delay of the concerned channel. In this paper, we have analyzed the dynamics of RTT behavior and shown how the congestion levels in the network, packet error rates and available buffer capacity affects the RTT measurements. The Mean RTT and the rate of change of RTT Mean values have been analyzed in different network conditions. These analysis have been carried out by simulation using ns2 considering a GEO Satellite network.

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Alterable Magnetic Gratings for Fiber Optic Switching

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A MEMS-Based Polarimetric Infrared Imaging Sensor

Self Healing System to mitigate Single Event Upset in SRAM based FPGA for Space Application

Mission-critical digital systems are often implemented on Field Programmable Gate Arrays (FPGAs),... more Mission-critical digital systems are often implemented on Field Programmable Gate Arrays (FPGAs), which allow for easy Configuration of the hardware. FPGAs are especially desirable in these applications due to their cost-effectiveness for relatively small quantity productions and the ease with which they can be reused. The configurable nature of FPGAs presents one of its strongest advantages as well as one of its most significant limitations as compared to an Application Specific Integrated Circuit (ASIC), which is a fixed logic integrated circuit that is customized for a particular use. Non-permanent characteristic of FPGAs also causes problems with errors in the system, especially in environment subject to high radiation. Particles may cause portions of the configured circuitry to change states. FPGAs are therefore more prone to errors in its logic values and in its actual circuitry than a custom hardware solution such as an ASIC. Thus, here proof-ofconcept for the system that is capable of detecting such errors and partially self-reconfiguring these corrupted areas is illustrated. This "self-healing (Self Correcting)" system is capable of gracefully recovering from soft errors while maintaining valid system outputs. The SEU controller macro and reference design can emulate an SEU by deliberately injecting an error into the FPGA configuration so that its subsequent detection and correction can be confirmed and SEU Injection of errors can also be used to assess SEU mitigation circuits implemented in a design. We describe the operation and architecture of the proposed logic design as well as its implementation in Xilinx virtex-5 FPGA.

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A study of acute and chronic anti-nociceptive and anti-inflammatory effects of thiamine in mice

Iranian biomedical journal, Jul 1, 2008

Thiamine (VitB1) is a vitamin with various important physiological functions and postulated thera... more Thiamine (VitB1) is a vitamin with various important physiological functions and postulated therapeutic effects. Its use as an analgesic in neuropathic pain has been undergoing in clinical settings. However, there has been little experimental investigation on this effect. In this study, anti-nociceptive and anti-inflammatory effects of thiamine were investigated in mice. Three doses of thiamine (50, 100 and 125 mg/kg) were used by intraperitoneal injection in this study. Acute and chronic anti-nociceptive effects were examined using hot plate test alone and after sciatic nerve ligation, respectively. Imipramine (40 mg/kg) was used as positive control. Anti-inflammatory effects of thiamine on acute and chronic inflammation were assessed using xylene-induced edema in ears and granuloma caused by compressed cotton implantation, respectively. Sodium diclofenac (15 mg/kg) was used as positive control. Open field test was performed to differentiate the mice responses in the acute anti-noc...

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Improving TCP Performance Over Wireless Network With Frequent Disconnections

International journal of Computer Networks & Communications, 2011

Presented in this paper is the solution to the problem that arises when the TCP/IP protocol suite... more Presented in this paper is the solution to the problem that arises when the TCP/IP protocol suite is used to provide Internet connectivity through mobile terminals over emerging 802.11 wireless links. Taking into consideration the strong drive towards wireless Internet access through mobile terminals, the problem of frequent disconnections causing serial timeouts is examined and analyzed, with the help of extensive simulations. After a detailed review of wireless link loss recovery mechanism and identification of related problems, a new scheme with modifications at link layer and transport layer is proposed. The proposed modifications which depend on interaction between two layers (i) reduce the idle time before transmission at TCP by preventing timeout occurrences and (ii) decouple the congestion control from recovery of the losses due to link failure. Results of simulation based experiments demonstrate considerable performance improvement with the proposed modifications over the conventional TCP, when a wireless sender is experiencing frequent link failures.

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Demonstration of Design Verification Model of Rubidium Frequency Standard

In this paper we report the development of the design verification model (DVM) of Rb atomic frequ... more In this paper we report the development of the design verification model (DVM) of Rb atomic frequency standard. The Rb atomic frequency standard or clock has two distinct parts. One is the Physics Package where the hyperfine transitions produce the clock signal in the integrated filter cell configuration and the other is the electronic circuits which generate the resonant microwave hyperfine frequency, phase modulator and phase sensitive detector. In this paper the details of the Rb Physics package and the electronic circuits are given. The effect of putting the photo detector inside the microwave cavity is studied and reported with its effect on the resonance signal profile. The Rb clock frequency stability measurements have also been discussed.

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Network State Classification Based on the Statistical Properties of RTT for an Adaptive Multi-State Proactive Transport Protocol for Satellite Based Networks

K.K.Shukla and K.S.Dasgupta, “A Proactive Transport Protocol for Performance Enhancement of Satellite based Network

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Receiver based Rate Adaptation Approach through Blind SNR Estimation of Satellite Channel

— A joint source and channel coding approach for image transmission over a satellite based broadc... more — A joint source and channel coding approach for image transmission over a satellite based broadcast channel is proposed. A resolution scalable source is matched to a hierarchical constellation in order to achieve an adaptive decoding capability. An estimate of signal to noise ratio (SNR) is derived blindly at the receiver and is used to facilitate reception at lower information rate. The rate is reduced by switching to a lower level constellation from hierarchical QAM. This ensures graceful degradation in performance and guarantees service with lower resolution for channel under-going high AWGN noise. The simulation results suggest that, for very noisy channels, the end to end distortion so obtained is much lesser compared to decoding at full resolution. Keywords- Hierarchical (HR) mapping, Joint source and channel coding( JSCC) , resolution scalability, , moment based signal to noise ratio estimation. , I. stream with stringent error sensitivities i.e. the coarser I NTRODUCTION

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