1. Hemanth Kumar S., Murali Bharadwaj N., and Sambasiva Rao V. “A SimpleConfiguration for Replacing Signal Harness in Satellite,” High Frequency Electronics, Vol. 12, No. 6, June 2013, PP 28-35.
A wired signal harness accounts up to 10% of the total dry mass of a satellite and traditionally has been a key design criterion. However, they can lead to the formation of ground loops and often pose a problem by generating Electromagnetic Interference (EMI) if not taken care of. This paper proposes a solution to reduce the wired signal harness in the satellite by adapting the RF LAN concept with Code Division Multiple Access (CDMA). The proposed concept completely eliminates the wired network between subsystems by creating a wireless intranet within the satellite. Latency is reduced since all subsystems can communicate simultaneously.
2. S. Venugopalan1, Dayanand B. M., Shanmugham C. N., Divya Rao, and V. Sambasiva Rao, V. K. Agrawal, “POWER SYSTEM DESIGN OF STUDENT IMAGING SATELLITE,” 63rd International Astronautical Congress, Naples, Italy. Copyright ©2012 by the International Astronautical Federation, IAC-12-C3.4.7, pp 1-8.
A robust and highly reliable power system has been designed with ATJ solar cells, COTS technology Lithium ion batteries, battery management & protection unit, advanced technology electronic parts and components. DC-DC buck – boost converters are used to provide regulated power to different onboard subsystems from the solar array/battery. The unique feature of the system is protection and management of power system elements (enable/disable of on-board devices, over current protection, health monitoring) and the distribution through OBC interface. This paper describes the architecture and design details of the Student Imaging Satellite (SISAT) Electrical Power System (EPS).
3. Divya Rao A., P. Natarajan, Rahil Ahmed S., and V. K. Agrawal, “Onboard Attitude Estimation using MEMS based Tri Axial Vector Magnetometers for Magnetically controlled Nano-Satellites,” ICIUS-2013-283.
For magnetically controlled satellites tri axial magnetometer data is used to derive the three axis attitude onboard. MEMS based tri axial Inertial Measurement Unit (IMU) is normally used in nano/pico satellites for attitude determination and control. The main aim of this paper is to estimate the attitude in terms of quaternions using tri axial magnetometer measurements. The paper deals with the construction of attitude profile matrix using the equally spaced normalized measurement and reference magnetic field vectors. The estimation of optimal quaternion in terms of Gibbs vectors and implementation of attitude estimation by computation of maximum Eigen value solution. This paper demonstrates the onboard implementation of the attitude estimation for the nano satellite PISAT.
5. Shashank Nagesh Bhat, Arjun Haritsa Krishnamurthy, Rao A. Divya, Nayak M Mahendra, and Vinod Kumar Agrawal, “Implementation of three axis magnetic control mode for PISAT,” 4thUK, 26-27 May 2015, 2014.B.3.3.
Orientation of a satellite is important so as to carry out payload operation. To maintain the satellite’s orientation Attitude Determination and Control System (ADCS) is the essential subsystem of the satellite. PISAT, a nano class satellite of 5.3Kg is equipped with an imaging payload to capture the images of Earth. The images are captured during normal mode of operation of ADCS, i.e., three axis magnetic control mode. This paper explains a simple and effective implementation of three axis magnetic control mode. The PISAT software cycle is designed for 64 msec major cycle and divided by 4 minor cycles (each 16 msec) in which all the said functionalities are executed. The three axis magnetic control mode is divided into different software modules so as to fit into time slices in software cycle designed for 64 msec. The software modules are implemented on an AVR32-AT32UC3A0512 microcontroller. This Paper details implementation of three axis magnetic control mode modules, the optimization performed to ensure faster results and proper placement of individual modules in software cycle The aim of the paper is to provide information quantifying the execution time of three axis magnetic control mode of ADCS. The paper is intended to deliver the onboard software requirements and implementation of three axis magnetic control mode on OBC of PISAT. The execution time of the three axis magnetic control mode modules were measured with a core system clock of 12 MHz using test system. Also, the difference of execution times for single precision, and double precision, floating point operations were measured. Finally, to verify the estimated times, all the modules were executed using single and double precision variables in hardware for which the real execution time was measured. Knowing the execution time, the three axis magnetic control mode modules were placed in appropriate minor cycles of the OBC software cycle.
6. Ketan Kulkarni, Rohith, Pramath H., Karunakar Praveen, Divya Rao, and Dr. V.K Agrawal, “Sustainable Passive Solar Daylighting with Open Loop Dual Axis Sun Tracking System,” Indian sustainability congress – 2014, 4-5 march 2014, The Atria hotel, Palace Road, Bangalore – 560001.
The idea here is to provide illumination inside spaces which are beyond the reach of natural sunlight – like basements, garages, hallways – by channeling sunlight through end glowing optical fiber cables. Solar rays are concentrated over an area where a bundle of end glowing optical fibers are placed to receive the focused light from the optical collector system. The collected visible spectrum of sunlight is then channeled through the fibers till the targeted location where a diverging device such as a concave lens is placed to spread out the light. Because of the sun’s daily and seasonal motion, a sun-tracking mechanism is incorporated to make sure that the sunlight is focused onto the optical collector system throughout the day. An open loop system will determine the position of the sun using algorithms that have been developed based on solar geometry. This algorithm uses the astronomical data to determine the position of sun for any given time and date by using the microcontroller. A dual axis tracker has been developed for tracking the sun throughout the day, over a long period of time. This tracking mechanism considers both daily and seasonal changes by variation in hour angle and declination angle respectively. Daily changes are taken into account by moving the collector system Interplanetary CubeSat Workshop, South Kensington, London
4. Divya Rao A., P. Natarajan, Rahil Ahmed S. and V. K. Agrawal, “Onboard estimation and correction of magnetometer bias in MEMS based Tri axial Inertial Measurement Unit,” ICIUS-2013-274.
MEMS based tri axial Inertial Measurement Unit (IMU) are used in nano/pico satellites for attitude determination and control. For magnetically controlled satellites triaxial magnetometer data of Inertial Measurement Unit (IMU), is used to derive the three axis attitude onboard. But the accuracy of the magnetometer may be compromised by large systematic magnetic disturbances on the satellite. Even the magnetic fields due to onboard electronics leads to residual magnetic fields which adds as bias in the measured magnetic field data. This paper describes the onboard estimation and correction of magnetometer bias using state estimator. The attitude independent state estimator is derived to ensure bias estimation even at high attitude errors. The algorithm has been implemented onboard for a nano satellite with active magnetic control system named PISAT. at a rate of 0.24 degree per minute which enhances the performance. We have designed a system to light up an area of around 78m 2 with an illumination of 500 Lux. The paper describes in detail about the selection procedure of components, design, development and implementation of Sustainable Passive Solar Daylighting System with Open Loop Dual Axis Sun Tracking System.
8. Divya Rao A., Divya Jyothi K., Vignesh S., and Dr. V. K. Agrawal, “Random Noise Coefficient Estimation for a Commercial Vibratory MEMS Gyroscope,” Proceedings of ‘Second International Conference on Emerging Research in Computing, Information, Communication and Applications’ (ERCICA-14).
Gyroscopes are the inertial sensors used to measure the angular rate. They have wide applications in automotive, aerospace and consumer electronic sectors. Commercial vibratory MEMS gyroscopes offer revolutionary improvements in size, cost, and ruggedness relative to spinning mass and fiber-optic gyroscopes. The performance of MEMS based gyroscopes is still not comparable to conventional high grade sensors in view of significant deterministic and random errors. Precisely, modeling and compensation for these errors is therefore very important. The aim of this paper is to characterize the most significant random errors of commercial MEMS gyroscopes using Allan Variance analysis. Allan Variance method is a simple stochastic model for estimating the random noise coefficients in the gyroscope data. This paper demonstrates the detailed process for the estimation of random noise coefficients using Allan Variance method. This method has been developed and implemented in MATLAB environment and verified using ALAVAR 5.2 tool. Experiments are performed on the static 1 hour data collected from a commercial MEMS Inertial Measurement Unit (IMU) ADIS-16405 which embed tri axial magnetometer, tri axial gyroscope and tri axial accelerometers.
9. Akhil S., Suthikshn Kumar, and Sambasiva Rao, “Study of multiple parameter algorithm for wrong decisions in vertical handovers in wireless heterogeneous networks,” Elixir Network Engg., ISSN: 2229 – 712X, April 2012, pp 7844-7849.
One of the most important and challenging problems for seamless access of wireless and mobile services is mobility management, which will be regardless of the services and networks. Mobility management enables the Mobile (MT) to switch between networks for better resource management and is still a hot research topic. With so many handover algorithms available, how to evaluate and select the best algorithm becomes critical, thus making handover algorithms one of the essential components for the successful implementation of mobility. These algorithms need to be designed to provide the required Quality of Service (QoS) over a wide range of applications. This work is based on new criterion called Wrong Decision Probability (WDP) which is used to evaluate the performance of vertical handover algorithms and is based on signal strength (SS) and the available bandwidth (BW), which are combined together to obtain a better decision for handover. This paper proposes a new user centric algorithm for vertical handovers, which minimizes the wrong decisions during a handover process and maximize the user throughput by taking into account Bandwidth and Signal Strength of the network.
10. Arathi R Shankar, Adarsh Pattar,and V. Sambasiva Rao, “Qualitative Analysis of QoS parameters at the Layer 1 and Layer 2 of MOBILE WiMAX 802.16e,” International Journal of Wireless & Mobile Networks (IJWMN), Vol. 4, No. 2, April 2012, pp 69-82.
IEEE 802.16/WiMAX is the network which is designed with quality of service in mind. In this paper the authors have made an attempt to qualitatively analyse the performance factors at the physical layer of mobile WiMAX for Rayleigh and Rician channels using different modulation techniques. The comparison of quality of service parameters like BER and power spectral density between different channels in WiMAX physical layer is made. Orthogonal frequency division multiple access technique is adapted by WiMAX on its physical layer.. Scalable OFDM has been implemented for subcarriers ranging from 256 to 2048 and the performance factors have not changed. Quality of Service provisioning at the MAC layer is done by using Packet scheduling technique using RR & Fairness queue algorithms for rtPS & nrtPS service flows. Comparison of different scheduling schemes are made that ensure QoS with respect to delay, under the context of different service flows as defined in the WiMAX standard.
11. Akhila S., and Sambasiva Rao V., “Mobility Algorithm Based on the Prediction of Wrong Decisions for Vertical Handover,” International Journal of Engineering Research and Technology, July 2012.
Continuous connectivity guaranteeing Quality of Service (QoS) is a common demand of the users due to the ubiquity of wireless technologies. The demand to be “always best connected” among heterogeneous wired and wireless networks is achieved through a technique called Vertical Handover (VHO), for which development of mobility models is one of the important key-point. Mobility models help in issues related to location management, the load and resources sharing aspects and also the radio propagation aspects. In this paper, the mobility pattern of the vehicle-borne Mobile Terminal has been considered to study wrong decisions that are encountered due to user movement at particular time period of the day. An algorithm for reducing the wrong decisions encountered at the junction points near the boundary of the network which are location independent, time period of the day dependent, and velocity of the Mobile Terminal and / or distance of the Mobile Terminal from the Base Station dependent has been proposed.
12. Jayanthi K. Murthy, Thimmappa P., and V. Sambasiva Rao, “Investigations on the Routing Protocols for Wireless Body Area Networks,” International Conference on Advances in Computing (ICAdC-2012), MSRIT,July4-6,2012, Bangalore, Proceedings of International Conference on Advances in Computing (ICAdC-2012), Advances in Intelligent and Soft Computing, Vol. 174, pp. 483–490, Springer India 2012.
In the last few years, wearable health monitoring systems have gained the attention of various researchers in order to cope with the rising cost of the health care systems. This paper addresses the use of standard protocols, particularly IEEE 802.15.4 and ZigBee, which are capable of supporting the Quality of Service (QoS) requirements in Wireless Body Area Networks. Simulation study on the routing protocols was done to investigate the protocol suitable for Body Area Networks and AODV was found to meet the requirements of energy and QoS.
13. Arathi R. Shankar, Adarsh Pattar, and V. Sambasiva Rao. “Mobile WiMAX Performance improvement using MRRC scheme for Real time applications,” International Conference on Emerging Research in Electronics Computer Science and Technology(ICERECT at PES College of Engineering Mandya on 21-22 Dec 2012.
IEEE 802.16e (or) Mobile WiMAX is the network which is designed with quality of service in mind. In this paper an attempt has been made to qualitatively analyze the performance factors of Mobile WiMAX under flat fading Rayleigh channel using MRRC techniques. The physical layer of Mobile WiMAX is simulated by using Maximal ratio combining diversity techniques. The physical layer performance parameters have been measured and compared by increasing number of diversity branches and by employing different modulation techniques. Proposed diversity scheme is compared with respect to throughput and Bit error rate by employing different modulation schemes for a real time application.
14. Arathi R Shankar, Adarsh Pattar, and V. Sambasiva Rao, “Mobile WiMAX Performance improvement using MRRC scheme for Real time applications,” International Conference on Emerging Research in Electronics Computer Science and Technology(ICERECT 12) at PES College of Engineering Mandya on 21-22, Dec 2012.
15. Arathi R. Shankar, Adarsh Pattar, and V. Sambasiva Rao, “Performance Improvement of Mobile WiMAX Physical Layer using Receiver Diversity Techniques,” International Journal on Electrical, Electronics and Telecommunication (IJEE), ISSN:2051-3240, Vol.44, Issue.1, January 2013, pp 1103 – 1106.
IEEE 802.16e (or) Mobile WiMAX is the network which is designed with quality of service in mind. In this work an attempt has been made to qualitatively analyze the performance factors at the physical layer of Mobile WiMAX under flat fading Rayleigh channel using receiver diversity techniques. For each scheme the physical layer performance parameters have been measured and compared by increasing number of diversity branches and by employing different modulation techniques. Finally all proposed diversity schemes are compared with respect throughput and Bit error rate by employing different modulation schemes by taking a real time application
16. Jayanthi K. Murthy, and V. Sambasiva Rao ,“Energy Efficient Relay Based Multi-hop Clustering Protocol for Wireless Sensor Networks”, International Journal of Application or Innovation in Engineering & Management, Volume 2, Issue 3, March 2013.
The quest for better protocol design that can minimize communication cost and energy usage in WSN has fuelled various researches into employing different kinds of communication modes that promise a better utilization of network resources. When sensor nodes are organized in a hierarchy or multi-level cluster structure using multi-hop communication mode, it is obvious that the nodes closer to the BS dies out first as a result of being over-burdened from relaying packets of other far away nodes. In this work an energy efficient protocol that balances the energy consumption in clusters which are placed at various distances from the base station is designed (EEMRC- Energy Efficient Multi Hop Relay Clustering). The selection of the relay nodes for Multiple Input Single Output technique with relay nodes has been implemented to increase the lifetime. Comparison of the proposed protocol with the standard LEACH protocol for life time yielded results which showed a large improvement.
17. Jayanthi K. Murthy, and V. Sambasiva Rao, “Relay Based Clustering Protocol for WSN”, International Journal of Computer Applications, vol. 68, April 2013 Edition.
Energy minimization and increase in lifetime have become the key factors for data transmission in a wireless sensor network. An energy efficient protocol called Energy Efficient Relay Based Multi-hop Clustering (EEMRC) that balances the energy consumption in clusters is implemented with the help of relay nodes. Comparison of the proposed protocol with the standard LEACH protocol yielded results which showed a large improvement in network lifetime.
18. Arathi R. Shankar, Prabhu Raddy and V. Sambasiva Rao, “Efficient Routing Protocol for Hand over Delay Minimization in Mobile WiMAX using Concurrent Scanning,” International Journal of Computer Applications (0975 – 8887), Volume 68, No.22, April 2013, pp 16-21.
In this article an efficient routing protocol has been identified for real time and non – real time applications.The MS movement direction prediction (MMDP) based MS scanning is implemented to overcome the mobile WiMAX handover issues. Here the authors have used the MMDP method to reduce the number of scanning’s required for the handover instead of scanning for all neighboring BSs and suggested that on using the concurrent scanning procedure for the best two TBS high quality hand over support in Mobile WiMAX can be achieved. On performing concurrent scanning of two best target base stations, issues like ideal sectors, network congestion and fast change in RSS are proposed to be minimized.The proposed algorithm targets to meet the quality of service requirements. Performance results for simulation scenarios are presented and discussed.
19. Jayanthi K. Murthy, and V. Sambasiva Rao, “Improved Routing Protocol for HealthCare Communications,” Open Journal on Applied Biosensors, vol. 2, Issue 2, pp 51-56, Pub. Date: May 13, 2013.
Wireless Body Area Network (WBAN) technology has significantly increased the potential of remote healthcare monitoring systems. The devices used for WBAN have limited energy resources. For most devices it is impossible to recharge or change the batteries. Since the data mostly consists of medical information, high reliability and low delay is required. The main objective of this simulation study is to evaluate the performance of routing protocol on static IEEE 802.15.4 to determine the most suitable routing protocol for Wireless Body Area Networks. Here, investigations on the various routing protocol suggest cluster topology and AODV as the probable candidate. About 16% improvement in the energy consumption was observed when modifications were made considering the energy and mobility, thus achieving high residual battery capacity and eliminating the need for recharging the batteries.
20. Arathi R. Shankar, Raghavendra G.,and V. Sambasiva Rao, “Analysis of Mac to Mac Video Streaming over Mobile WiMAX 802.16e,” International Journal of Advances in Engineering & Technology (IJAET), Volume 6, Issue 2, May 2013, pp 668-677.
In this research article efficient transmission of video streaming across PHY(Physical) and MAC(Medium Access Control) layer of Mobile WiMAX (Worldwide Interoperability for Microwave Access) IEEE 802.16e using HARQ (Hybrid Automatic Repeat Request) technique is proposed. HARQ utilizes both FEC (Forward Error Correction) and ARQ (Automatic Repeat Request) technique which reduces the delay, packet loss rate and increases the throughput efficiently under the prescribed quality of service constraint. In this research work, the authors have made a comparative analysis of the throughput, delay and jitter on a video traffic application with and without ARQ implementation. Adaptation of Modulation and coding scheme at PHY layer along with MAC layer HARQ are considered in this work .Both QoS parameters and service classes of PHY layer and MAC layer are analysed and the parameters of PHY layer are to be mapped with the QoS parameters of MAC layer ,so that video streaming can be easily and efficiently transferred with proper mapping of QoS service classes and by using Hybrid ARQ technique. For the proposed design the performance measures like the end to end delay, average throughput, and average jitter are numerically analysed. Numerical results indicate that performance factors and throughput are expected to further increase with this proposed method.
21. Arathi R. Shankar, Raghavendra G., and V. Sambasiva Rao, “HARQ Implementation for Efficient MAC to MAC Video Streaming over Mobile WiMAX,” International Journal of Management & Information Technology, Vol. 5, No. 1, ISSN 2278-5612, Aug 2013.
IEEE 802.16e is the standard for Mobile WiMAX which was introduced by the IEEE committee to provide broadband access in rural and urban areas over fixed wireless channels. Mobile WiMAX is an enhanced version of IEEE 802.16 standard with mobility support. There are lots of challenges involved in the service provided by the Mobile WiMAX. Efficient data transfer between different layers of mobile WiMAX is one of the major research issues. In this work HARQ (Hybrid Automatic Repeat Request) technique is implemented in Qualnet environment for an efficient transmission of video streaming across PHY(Physical) and MAC(Medium Access Control) layer of mobile WiMAX (Worldwide Interoperability for Microwave Access). HARQ utilizes both FEC (Forward Error Correction) and ARQ (Automatic Repeat Request) techniques to reduce the delay, jitter and to increase throughput efficiently under prescribed quality of service constraint. Different Scheduling schemes and cross layer approaches that support mobile WiMAX are analysed. mmSIR scheduler is used in this work since it allocates resources priority wise. Diffferent network quality parameters like end to end delay,average jitter,and average throughput have been analysed by using existing ARQ and implemented HARQ techniques.Both ARQ and HARQ techniques are compared for a video application.
22. Arathi R. Shankar, Prabhu Raddy, and V. Sambasiva Rao, “Concurrent Scanning for High Quality Hand Over Support in Mobile WiMAX Networks,” International Journal of Computers & Technology (IJCT), Volume 10, No 2, ISSN 22773061, August 2013.
Mobile WiMAX is IEEE 802.16e standard established for mobile broadband wireless access (BWA). Mobility in WiMAX system is an important issue when the mobile station (MS) moves and be handover between base stations (BSs). This issue causes an unnecessary neighboring BS scanning and association, handover delay, and MAC overhead which may affect real-time applications. The MS movement direction prediction (MMDP) based MS scanning is used to reduce the number of scanning’s required in mobile WiMAX handover process. In this paper with reduction in number of scanning’s we propose to reduce the scanning delay required for evaluated two best target BSs by using concurrent scanning process. Network issues like ideal sectors in WiMAX 2 (IEEE 802.16m), network congestion and fast change in RSS are important parameters which can affect the QoS. With this proposed model we are able to provide the high quality hand over support in mobile WiMAX wherein we are able to solve the above stated network problems. Here on using the concurrent scanning process the authors are able to reduce the scanning delay by 40%. As a part of this paper, network layer parameters called routing protocols are analyzed for hand over support. This analysis shows an efficient routing protocol for real time application and the best effort service. This reviles that fisheye protocol is better to use for smaller network and LANMAR for the larger networks in real time application and IERP protocol is good for best effort services.
23. Sridhara R., Arathi R. Shankar, and V. Sambasiva Rao, “A Novel Decision Algorithm for Vertical Handoff between UMTS and WiMAX,” Scholars Journal of Engineering and Technology (SJET), ISSN 2321-435X, 2013; 1(4), pp251-256.
The benefits brought about by 3G networks such as UMTS, it is increasingly desirable to integrate 3G networks with WiMAX.. WiMAX is used to extend 3G networks at certain locations in order to provide improved services and address QoS issues. To achieve a beneficial vertical handover in a network, an algorithm that departs from the conventional RF based algorithm is necessary. An attempt is made in this study to provide an algorithm which aims to utilize location information stored in a WiMAX coverage database, and the location service entities of UTRAN as defined by 3GPP to determine a valuable/beneficial vertical handover between UMTS and WiMAX. RF based conventional downward vertical handovers can be inefficient and waste of resources. This study aims to correct the lapses associated with conventional RF based vertical handover across heterogeneous network.
24. Arathi R. Shankar, Adarsh Pattar and V. Sambasiva Rao, “Mobile WiMAX Performance Improvement Using MRRC Scheme for Real-Time Application,” Emerging Research in Electronics, Computer Science and Technology, Lecture Notes in Electrical Engineering 248, 2014, pp 563-570.
IEEE 802.16e (or) Mobile WiMAX is the network which is designed with the quality of service in mind. In this paper, an attempt has been made to qualitatively analyze the performance factors of Mobile WiMAX under flat-fading Rayleigh channel using MRRC techniques. The physical layer of Mobile WiMAX is simulated by using maximal ratio combining diversity techniques. The physical layer performance parameters have been measured and compared by increasing the number of diversity branches and by employing different modulation techniques. Proposed diversity scheme is compared with respect to throughput and Bit error rate by employing different modulation schemes for a real-time application.