A. S. Gandhi

Small size planar monopole antenna for high speed UWB applications

In modern wireless communication, UWB applications are becoming very popular because of reliable, secure and high speed data transmission over smaller distances. In these applications, it is very much essential to have small size printed antennas for transmitting and receiving of UWB signals. However, designing small size printed antennas with good performance is quite a challenging task. In this paper, we discuss performance characteristics of a simple and small size planar monopole antenna for UWB applications. Proposed UWB antenna is covering 10dB return loss frequencies ranging from 2.72GHz to 12.68GHz. This design is achieving a maximum gain of 5.24dBi at 9.25GHz and a maximum efficiency of 96.45% at 3.1GHz. This paper also discusses a reason of enhancement in gain and efficiency reduction at higher frequencies along with UWB antennas requirements. Proposed design dimensions are 30mm×30mm×1.6mm with FR-4 as a dielectric substrate. Because of small size and good performance, proposed UWB antenna can be used in many applications like 4G, wireless body area networks, spectrum sensing in cognitive radio, wireless telemetry, telemedicine and RF energy harvesting. Experimental result shows that, there is a good agreement between the simulated and measured antenna results.

A new timing metric for timing error estimation in OFDM

Orthogonal frequency division multiplexing (OFDM) is a bandwidth efficient modulation scheme used widely for high speed data communication. In OFDM system, intersymbol interference (ISI) and intercarrier interference (ICI) occur due to synchronization errors. Fast, simple and robust synchronization algorithms are necessary for OFDM systems. In this paper, a simple and robust algorithm for timing synchronization is proposed. In OFDM downlink transmission, every terminal perform synchronization by exploiting reference symbols called training symbols of received frame. Proposed timing synchronization algorithm is based on use of reference symbol. Performance analysis shows that the proposed timing offset estimator have better performance despite being simple. Performance is studied over AWGN and time-dispersive multipath Rayleigh fading channel with the conclusion that the proposed synchronization technique result in better performance with respect to all the parameters.

A simple and efficient approach for medical image security using chaos on EZW

In this digital era medical image security is important as they carry highly personal data, which should be kept away from the hackers and unauthorized persons, as these images are transmitted/stored among hospitals and also by health insurance companies. Chaos based cryptography/security has been increased in recent years. In this paper we proposed an algorithm, in which security can be given along with effective compression of image. Our process of providing image security starts with compressing the image using EZW. The output sequence of EZW is converted to 2D and on the 2D data we are going to apply row wise and column wise scrambling algorithm based on chaos. In this paper we are also going to discuss about part of EZW in providing additional security to image along with its main function of compression.

Image security using chaos and EZW compression

This paper deals with the image security along with compression. Here we have proposed an algorithm using chaos on EZW compression technique to provide security along with image compression. We had chosen chaos for image security due to its robustness to initial condition and mixing property. Our process of providing image security starts with compressing the image using EZW. The output sequence of EZW is converted to 2-D data and on this 2-D data we apply row and column scrambling algorithm based on chaos. In this paper we also discuss about part of EZW in providing additional security to image along with its main function of compression.

Energy-Aware Network-on-Chip Architecture Using Perfect Difference Network

Network-on-Chip (NoCs) are currently viewed as a revolutionary approach to provide a scalable, high performance and robust infrastructure for on-chip communication. Network-on-Chip (NoCs) interconnection architecture to be used in System-on-Chip (SoCs) meet the communication requirements of these systems, offering at the same time, reusability, scalability and parallelism in communication. Furthermore, they cope with other issues like energy constraint and clock distribution. Energy consumption of Network-on-Chip architecture becomes one of the most vital parameter to optimize in the most of the system design. Therefore it is essential to develop energy-aware techniques for Network-on-Chip architecture. In this paper, we discuss the energy-aware Network-on-Chip architecture based on the mathematical notion of Perfect Difference Sets (PDS). In this paper, we propose the energy model for Network-on-Chip architecture using Perfect Difference Network (PDN). In this paper, we are proposing energy-aware model for PDN Circular geometry and PDN Inter-link geometry of Network-on-Chip architecture. The proposed energy model is then validated against simulation results obtained with PDN Inter-link geometry and PDN circular geometry for Network-on-Chip (NoC) architecture. The simulation results shows that significant energy saving is achieved for PDN Inter-link geometry in comparison with PDN circular geometry on the basis of our proposed energy model.

A Compact Novel Three-Port Integrated Wide and Narrow Band Antennas System for Cognitive Radio Applications

The design of a three-port radiating structure, integrating wide and narrow band antennas for cognitive radio applications, is presented. It consists of a UWB antenna for spectrum sensing and two narrow band antennas for wireless communication integrated on the same substrate. The UWB antenna covers the complete UWB spectrum (3.1 GHz to 10.6 GHz) approved by FCC. In the two narrow band antennas, each antenna presents dual bands. In particular, the first narrowband antenna resonates at 6.5 GHz, covering the frequency band between 6.36 GHz and 6.63 GHz, and at 9 GHz, covering the frequency band between 8.78 GHz and 9.23 GHz, presenting minimum return loss values of 28.3 dB at 6.5 GHz and 20.5 dB at 9 GHz, respectively. Similarly, the second one resonates at 7.5 GHz, covering the frequency band between 7.33 GHz and 7.7 GHz, and at 9.5 GHz, covering the frequency band between 9.23 GHz and 9.82 GHz, presenting minimum return loss values of 19.6 dB at 7.5 GHz and 28.8 dB at 9.5 GHz, respectively. Isolation among the three antennas is less than −20 dB over the UWB frequency spectrum. These antennas are realized on a FR4 substrate of dimensions 30 mm × 30 mm × 1.6 mm. Experimental results show a good agreement between the simulated and measured results.

New Time Error Estimation Technique for OFDM System

OFDM based systems are extremely sensitive to time and frequency synchronization errors. This paper addresses the issue of time synchronization. In this paper we are presenting a simple and novel technique for time synchronization. The time synchronization error causes Inter Symbol Interference and hence must be corrected at receiver. In many wireless communication systems, the data packets or frame start with the preamble called training symbol followed by data symbols. The training symbol consists of some specific pattern. The similar frame structure is used for this new algorithm which consists of training symbol followed by OFDM data symbols. This novel technique uses new pattern for training symbol which consists of all identical samples. After applying our new algorithm, a peak is obtained at the end of training symbol. This is used to mark beginning of frame and estimation of timing error. Estimation error graph and BER graph are presented for 4QAM and 16 QAM in this paper. The results are shown for AWGN channel. The technique used is simple and results are encouraging and can be used in any of the OFDM based system.

Algorithms for analog to multi-valued digital conversion

Generalised successive approximation algorithms for analog to multi-valued digital conversion are developed. In all, twelve variations are described. They are determined by the type of quantization (mid-tread or mid-rise), arrangement of the thresholds for comparison (symmetric or asymmetric), nature of thresholds (fixed or variable). In the case of fixed thresholds, one or more sets of thresholds may be used. Simulation results of the algorithms are reported. The ADC configurations based on these algorithms are identified. The type of many existing implementations is also determined. New possibilities of implementation are proposed.

A Survey on Planar Antenna Designs for Cognitive Radio Applications

In recent years, the demand for spectrum continues to increase with the advent of various wireless communication applications. However, it is a limited resource and cannot be made available beyond a certain extent. Many of the times, licensed spectrum is free due to its inefficient utilization. So, it can be utilized for other applications to mitigate the problem of limited spectrum availability to some extent. Among the many ways of performing this task, one approach is to use the frequencies in statically licensed spectrum through continuous sensing, which is popularly known as cognitive radio technology. In this model, UWB antennas are employed to monitor the radio environment and narrow band (NB) antennas are adopted for communication. This paper discusses various kinds of planar monopole antennas for cognitive radio applications. They are divided into three categories on the basis of different antennas used in cognitive radio environment. In the first category two separate antennas, which include one UWB antenna and one frequency reconfigurable NB antenna are employed for spectrum sensing and communication, respectively. In the second category, a single port frequency reconfigurable UWB/NB antenna is used. However, it requires an appropriate switching mechanism to switch between the UWB and NB modes. The third category includes dual-port integrated antennas systems, in which one UWB antenna and one frequency reconfigurable NB antenna are integrated on a single substrate. Finally, this paper discuss an opinion of designing multi-port integrated UWB and NB antennas systems to overcome the drawbacks of reconfigurable antennas and to further enhance the spectrum utilization efficiency.

SDR Based Energy Detection Spectrum Sensing in Cognitive Radio for Real Time Video Transmission

Cognitive radio is a budding approach which helps to address the imminent spectrum crisis by dynamic spectrum allocation and support the increased data traffic with an intelligent mechanism of Software Defined Radio (SDR). SDR avoid the frequent modifications in the hardware structure with the use of software defined protocols. The main novelty of the paper is an effective implementation of CR using energy based spectrum sensing method which is done on GNU radio for real time transmission of video as a primary user. From evaluation results, one can see that the proposed system can indicate the frequency band occupancy by setting the detection output. Detection output changes to one with start of video transmission. Motivation behind this work is design of a spectrum sensing method which is best suited for detection of white spaces during the transmission of video as a primary user on SDR platform.