Showing papers by "Vimal Bhatia published in 2018"

Impact of Imperfect CSI on ASER of Hexagonal and Rectangular QAM for AF Relaying Network

Abstract: In this letter, we derive the closed-form expression of outage probability for a dual-hop variable-gain amplify-and-forward relay network. The maximal ratio combining receiver over independent and non-identically distributed frequency flat Nakagami-m fading channels with integer-valued fading parameter and imperfect channel state information (CSI) is considered. Asymptotic analysis on outage probability is also performed. Average symbol error rate (ASER) expressions are derived for general-order hexagonal and rectangular QAM schemes using the cumulative distribution function-based approach. The impact of the fading parameter and imperfect CSI are highlighted on the system performance. Comparative analysis of ASER performance for different QAM constellations is also illustrated. Monte Carlo simulations are performed to validate the derived analytical results for both perfect and imperfect CSI.

Adaptive Precoding-Based Detection Algorithm for Massive MIMO Visible Light Communication

Abstract: Visible light communication (VLC) has emerged as a promising, green, and interference-free supplement to existing radio frequency-based communication systems. To enhance the capacity of existing VLC-based systems, using massive arrays of light emitting diodes (LEDs) at the transmitter and photodiodes at the receiver has been proposed recently, resulting in a massive multiple-input multiple-output (m-MIMO) VLC system. However, by increasing LED array pitch in m-MIMO, the VLC channel matrices are generally ill conditioned which makes them sensitive to small perturbations and degrades the overall bit error rate (BER) performance. To reduce the condition number of the overall channel matrix, a novel precoder using an exponent-based singular value decomposition is proposed for m-MIMO VLC system. Furthermore, a joint optimization problem is formulated to optimize the exponent and to detect symbols iteratively using the minimum symbol error rate criterion. Simulations show that the proposed adaptive precoding technique exhibits superior BER performance over existing techniques. Analytical upper bounds for BER are also derived and validated by simulations.

A Cooperation Scheme for User Fairness and Performance Enhancement in NOMA-HCN

Abstract: Rapid increase in number of cellular users and high demand for data has lead to the formation of multi-tier networks. Non-orthogonal multiple access (NOMA) has proved to be an efficient method to cater to the paradigm shift from 4G to 5G. This paper employs NOMA in an heterogeneous cellular network consisting of a macro base station (MBS) tier underlaid with femto base station (FBS) tier and device-to-device (D2D) tier, where NOMA is employed in FBS and D2D tier only. The congestion at the MBS tier is relieved by offloading macro users (MU) to the FBS tier. The offloaded MU are further supported by the D2D tier when the FBS tier fails to find a corresponding pairing user for the incoming offloaded MU. Since, absence of pairing user means outage for offloaded MU, D2D cooperation is employed, which decreases the rate outage probability by $86.87\%$ for the MU offloaded as cell edge user (CEU) in comparison to no cooperation. Also, a three times increase in ergodic rate and four times increase in sum ergodic rate for MU offloaded as CEU is achieved using cooperation from D2D tier. Verification of the results is done using Monte Carlo simulations.

LogDet Covariance Based Spectrum Sensing Under Colored Noise

Abstract: Cognitive radio is proposed for efficient utilization of radio spectrum using dynamic spectrum allocation. Most of the spectrum sensing algorithms for cognitive radio are based on some operations on eigenvalue of the covariance matrix of received symbols. However, the performance of existing algorithms degrade in the presence of colored noise due to swelling effect of the covariance matrix. To circumvent this limitation, we propose to use LogDet of covariance matrix of the received samples for spectrum sensing in cognitive radio. The proposed algorithms work extremely well at low signal-to-noise ratio in the presence of both white and colored noise. We also derive the detection threshold of the proposed algorithms. Simulation results show robustness of the proposed algorithms over existing algorithms on the captured digital television signal.

SCMA Codebook Based on Optimization of Mutual Information and Shaping Gain

Abstract: Sparse code multiple access (SCMA) is a promising non-orthogonal multiple access (NOMA) technique for the fifth generation (5G) and beyond wireless networks. The performance of the SCMA-based NOMA system is sensitive to the codebook design. Since there is no optimum method of codebook design, these are designed, in general, using sub-optimal methods. The high values of the mutual information and the shaping gain of the multidimensional constellation points improve the SCMA codebook's performance. Hence, in this paper, we design an SCMA codebook by optimizing the mutual information and the shaping gain of constellation points with the constraints of fixed minimum Euclidean distance and average power. Simulation results show that the SCMA system with the proposed codebook outperforms those with the existing codebooks. Further, it is observed that the message passing algorithm converges faster to successful detection with the proposed codebook.

Precoding Technique for Ill-Conditioned Massive MIMO-VLC System

Abstract: Visible light communications (VLC) has lately emerged as a viable supplement to existing radio frequency (RF) based communication systems, and is an integral component of future communication systems. The possibility of deploying massive arrays of light emitting diodes (LED) and photo-detectors (PD), which translates to a massive array of multiple input multiple output (MIMO) system for VLC, have been recently proposed. However, massive-MIMO in VLC has the following drawbacks which limit its practical deployment: a) high condition number of the channel matrix, which negatively affects the robustness of traditional channel-inversion based detection, and b) high interference in a multi-user setting due to correlated columns of the overall MIMO channel matrix. In this paper, the multi-user (MU) massive-MIMO in VLC is considered, and a precoding technique is proposed that induces diverse effective channel matrices for different users, and hence facilitates MU detection using ordered successive interference cancellation. Further, it is shown that the proposed precoding technique maximizes an upper bound of the overall sum-rate of the MU massive-MIMO system. Lastly, simulations have been performed for MU massive LED and PD arrays demonstrating that the proposed precoding technique outperforms existing precoding techniques, and hence is a viable solution for massive-MIMO in VLC.

IR-UWB Sensor Network Using Massive MIMO Decision Fusion: Design and Performance Analysis

Abstract: This paper proposes and analyzes impulse radio ultra-wideband (IR-UWB) system for wireless sensor networks (WSNs) using massive antenna arrays (MAAs) at fusion center (FC) for distributed detection. The coherent- and energy-based fusion rules are analyzed for the proposed WSN over multiple access channels. The tradeoff between the performance and the implementation complexity of the coherent- and energy-based fusion is studied. Furthermore, we show that MAAs at FC with various levels of channel knowledge can enhance the performance of energy-based detector in a UWB sensor network with simple system implementation and signal processing. Performance of the proposed UWB sensor network with reference to probability of detection, false alarm, and error are analyzed over the standard IEEE 802.15.4a multipath channels and results are validated using simulations. We have also analyzed the impact of various design parameters, such as the number of sensors, receiver antennas, sensor quality, and integration interval, on the system performance.

Grassmann Manifold-Based Spectrum Sensing for TV White Spaces

Abstract: In this paper, a new method of sensing primary user’s signal for cognitive radios in Grassmann manifold is proposed. The Grassmann covariance matrix (GCM) is formed with the help of covariance matrix of the transmitted and the received symbols. By using GCM, a new test statistic is defined, which is the modification of Binet–Cauchy metric. On the basis of this new test statistic, primary user’s signal is detected. We also show that the new test statistic is a valid detector since it follows the concentration phenomena. We derive the distribution of new test statistic under null hypothesis and alternative hypothesis. Lower bound for the probability of detection of signal is also derived using separating function and distribution of new test statistic. Simulations using the real-world measurements of digital television (DTV) signal show performance gain of the proposed method in terms of signal detection over existing methods and their agreement with the derived distribution. Additionally, we extend the proposed method for the cooperative spectrum sensing and derive the distribution under both hypotheses. Experimental verification on the software defined radio is also performed and it is found that the proposed method fulfills the requirement of maximum protection of the DTV signal.

Kernel Adaptive Filtering Based on Maximum Versoria Criterion

Abstract: Information theoretic learning based approaches have been combined with the framework of reproducing kernel Hilbert space (RKHS) based techniques for nonlinear and non-Gaussian signal processing applications. In particular, generalized kernel maximum correntropy (GKMC) algorithm has been proposed in the literature which adopts generalized Gaussian probability density function (GPDF) as the cost function in order to train the filter weights. Recently, a more flexible and computationally efficient algorithm called maximum Versoria criterion (MVC) which adopts the generalized Versoria function as the adaptation cost has been proposed in the literature which delivers better performance as compared to the maximum correntropy criterion. In this paper, we propose a novel generalized kernel maximum Versoria criterion (GKMVC) algorithm which combines the advantages of RKHS based approaches and MVC algorithm. Further, a novelty criterion based dictionary sparsification technique as suggested for kernel least mean square (KLMS) algorithm is proposed for GKMVC algorithm for reducing its computational complexity. Furthermore, an analytical upper bound on step-size is also derived in order to ensure the convergence of the proposed algorithm. Simulations are performed over various non-Gaussian noise distributions which indicate that the proposed GKMVC algorithm exhibits superior performance in terms of lower steady-state error floor as compared to the existing algorithms, namely the KLMS and the GKMC algorithms.

Performance analysis of OFDM based 3-hop AF relaying network over mixed Rician/Rayleigh fading channels

Abstract: In this paper, performance of an orthogonal frequency division multiplexing (OFDM) based 3-hop variable-gain amplify and forward (AF) relaying network is analyzed over independent and non-identically distributed (i.n.i.d.) mixed Rician/Rayleigh fading environment. Analytical expression of outage probability is derived and diversity order of the considered system is found. Further, average symbol error rate (ASER) expressions of general order hexagonal quadrature amplitude modulation (HQAM), general order rectangular QAM (RQAM) and 32-XQAM are derived. A comparative analysis of ASER for different QAM schemes with different constellations is also presented. Ergodic capacity with optimum rate adaptation is also derived for the considered system model. Further, the impact of Rician K-factor on the performance of the considered system is highlighted. Finally, the derived analytical results are verified through Monte-Carlo simulations for different signal-to-noise ratio (SNR) levels.

Performance analysis of AF OFDM system using multiple relay in presence of nonlinear-PA over inid Nakagami-m fading

Abstract: Summary In this paper, performance of an orthogonal frequency division multiplexing–based variable-gain amplify and forward cooperative system using multiple relay with relay selection is analyzed over independent but not necessarily identically distributed frequency selective Nakagami-m fading channels. For the analysis, nonlinear power amplifier is considered at the relay, and selection combining is adopted at destination node. Closed-form expressions of the outage probability for various threshold signal-to-noise ratio (SNR) values and average symbol error rate for M-ary quadrature amplitude modulation techniques are derived for the considered system. Further, the outage probability analysis is performed in high SNR regime to obtain the diversity order. Furthermore, impact of different fading parameters, multiple relay, and nonlinear power amplifier is highlighted on the outage probability and asymptotic outage probability for various threshold SNRs and on the average symbol error rate for various quadrature amplitude modulation constellations. The derived analytical expressions are generalized for various fading environments while considering the integer-valued fading parameters. Finally, all the analytical results are verified through the Monte Carlo simulations for various SNR levels and system configurations.

A Low-Cost Optical Sensor for Secured Antispoof Touchless Palm Print Biometry

Abstract: Conventional biometric spoof detection sensors suffer from several problems, including complex expensive sensor assembly and design. They are susceptible to environmental perturbation and are not robust against all types of spoof attacks. Further, for a secured biometric sensor, the hierarchy of spoofing attempts (i.e., curious attempts, low-level attack, and high-level attack) needs to be precisely distinguished to perform different actions (e.g., a high-level attack should be handled carefully). In this article, we propose a novel three-level antispoof palm print biometric sensor using low-cost components and simple optical techniques (photography, fringe projection, and biospeckle analysis). At the first level, to eliminate the curious futile users, a 2-D image of the palm print is captured, and feature matching is performed. Next, the most prevalent low-level attacks (photo and layered attacks) are detected using fringe projection profilometry. At the final level, a novel biospeckle index based on a subtraction average technique is introduced to quantify the liveliness map for eliminating the high-level attacks, including fake prints and cadavers. The robustness of the biospeckle analysis against different possibilities to generate false activity (tremor, air flow, and heat flow) has also been verified.

Impulse Noise Mitigation in IR-UWB Communication Using Signal Cluster Sparsity

Abstract: In this letter, we propose a novel robust impulse radio-ultra-wide band (IR-UWB) receiver design that utilizes the received UWB signal cluster sparsity characteristics to mitigate impulse noise (IN). The IN samples are easily detected and removed in the proposed receiver. Furthermore, multiple UWB signal clusters (due to multipath channel), in the proposed receiver design, reduce UWB signal blanking loss as compared with the single cluster (single path channel). The proposed receiver’s bit error rate (BER) performance is theoretically analyzed and compared with six popular existing non-linear receivers in the presence of IN over standardized IEEE 802.15.4a channel models. Unlike the existing receivers, the proposed receiver does not require a priori knowledge of the amplitude, the probability of occurrence of IN, or channel estimation.

Receiver for IEEE 802.11ah in Interference Limited Environments

Abstract: Recently, IEEE 802.11ah standard has been proposed to extend the range of wireless local area network operating in the sub-1-GHz frequency band. This standard along with other protocols can provide communication services to the Internet of Things applications. However, in future, this band is also expected to be crowded like 2.45 GHz ISM band and cause interference to other devices operating in the same band. For a communication channel affected by additive white Gaussian noise, the least square (LS)-based estimator and Euclidean distance-based Viterbi decoder give optimal performance. However, the receiver’s performance with LS estimator followed by the Viterbi decoder degrades for high interference affected communication channels. In this paper, a new orthogonal frequency division multiplexing-based receiver structure operating in high interference environment is proposed. The proposed receiver is based on nonparametric maximum likelihood channel estimation followed by Viterbi decoder. The Viterbi decoder’s branch metric is updated based on the distribution of residual error. The proposed receiver structure is tested on IEEE 802.11ah-based receiver in two different type of additive interference: 1) IEEE 802.15.4 device and 2) impulsive noise. Both simulations and real-world experimental results on standard compliant platform show that the proposed algorithm performs better in terms of bit error rate than other receivers in all the considered interference models. Additionally, we also derive analytical expression for the probability of symbol error.

Performance Analysis of Flow Assisted Diffusion Based Molecular Communication for D-MoSK

Abstract: Molecular communication is used to form a network of nano devices where bio-molecules are used as information carriers. Information can be encoded as number, type and release time of molecules. In molecule shift keying (MoSK), an encoding scheme, transmitter sends variety of molecule for each bit, which results in increased complexity at the transmitter and the receiver, especially for higher modulation scheme. In this work, we consider depleted molecule shift keying (D-MoSK), an efficient modulation scheme, where different molecules are transmitted for each bit, only when bit value is '1'. This reduces the overall requirement to log_2M for M-ary symbols. In this work, performance analysis of the flow assisted diffusion channel molecular communication is investigated. The effect of flow velocity, interference of time slotted transmission and diffusion coefficient on average symbol error rate and achievable mutual information rate of the channel is derived. Delay introduced by the medium in time slotted transmission is also investigated. Numerical results show lower average symbol error rate and higher achievable information rate for the considered system as compared to no drift MoSK scheme.

Noncoherent IR-UWB Receiver Using Massive Antenna Arrays for Wireless Sensor Networks

Abstract: Noncoherent impulse radio ultrawideband (UWB) receivers do not require channel state information and are also robust against pulse shape distortions. However, their performance is suboptimal, especially at low signal-to-noise ratios. In this article, we propose simple noncoherent UWB receivers for wireless sensor network applications using massive antenna arrays. Two receivers are proposed: based on instantaneous received UWB signal energy and based on weighted instantaneous received UWB signal energy. The proposed receivers use the law of large numbers resulting from the massive receiver arrays and utilize the large degrees of freedom available in a UWB multipath channel. Furthermore, the proposed receivers do not require training symbols for the estimation of decision threshold. Both these receivers outperform the existing noncoherent receivers as verified using simulation results on the standardized IEEE 802.15.4a UWB multipath channel.

Performance Analysis of AF Relayed NLOS UV Communication Over Turbulent Channel

Abstract: Ultraviolet (UV) communication experiences strong aerosol and molecular scattering which leads to non-line-of-sight (NLOS) connectivity. As the UV signal propagates through the atmosphere, the change in the refractive index of the atmosphere causes random fluctuations in the transmitted signal, this phenomenon is referred to as turbulence. The effect of atmospheric turbulence in NLOS UV communication link is usually ignored under the assumption of short distance communication. In this paper, we consider a NLOS UV communication system experiencing fading due to atmospheric turbulence and use relay-assisted transmission for improved connectivity. We present performance analysis of dual-hop amplify-and-forward (AF) relayed outdoor NLOS UV communication and derive closed-form expressions for the outage probability, average symbol error rate, ergodic capacity and relative diversity order. Analytical expressions using two different approximations are compared and validated with simulations.

Performance Analysis of Opportunistic Two-Way 3P-ANC Multi-Relay System with Imperfect CSI and NLPA

Abstract: In this work, a two-way multi-relay system using three phase analog network coding (3P-ANC) with opportunistic relay selection scheme is considered, and performance is analyzed over independent and non-identically distributed (i.n.i.d.) Nakagami-m fading channels with imperfect channel state information (CSI) and non-linear power amplifier (NLPA) at the relays. For this, closed-form expression of outage probability is derived and diversity order of the system is obtained with the help of asymptotic outage probability. Further, the impact of number of relays, fading parameter, channel estimation error and non-linear distortion are highlighted on the system's performance. Finally, theoretical expressions are validated through simulations.

Defragmentation Based Load Balancing Routing & Spectrum Assignment (DLBRSA) strategy for elastic optical networks

Abstract: In this paper, we propose a defragmentation based load balancing technique for efficiently undertaking routing and spectrum assignment (RSA), and minimizing the fragmentation problem in elastic optical network (EON). In EON, after connections terminate, they leave behind spectrum gaps which con not be re-assigned. To counter this condition, in Defragmentation based Load Balancing Routing and Spectrum Assignment (DLBRSA), the existing connections are reconfigured. At the time of defragmentation, for route selection, among the available shortest routes, the route with the largest chunk of contiguous frequency slots (FSs) is chosen. DLBRSA has three advantages over the conventional Shortest Path RSA (SPRSA) technique: (1) defragmentation increases the network resource utilization, (2) load balancing on the basis of the largest available FS chunk along the route ensures uniform spectrum allocation, and (3) defragmentation ensures that the route length of the request is minimum. The performance of the DLBRSA is analyzed in reference to a benchmark, SPRSA strategy. The comparison is done on the metrics of bandwidth rejected, and the percentage of total network capacity allocated for the EON and NSFNET network topologies. These two parameters are evaluated under the two scenarios of increase in: network load (in Erlang) and number of FSs demand. Simulation results show lower bandwidth blocking probability of DLBRSA from 6.53% to 8.96% under the different load conditions. In addition, decrease of network resource utilization is observed, when we compare the proposed DLBRSA with SPRSA the existing strategy.

Automated collimation testing by determining the statistical correlation coefficient of Talbot self-images

Abstract: In this paper, we propose a simple, fast, and accurate technique for detection of collimation position of an optical beam using the self-imaging phenomenon and correlation analysis. Herrera-Fernandez et al. [J. Opt.18, 075608 (2016)JOOPDB0150-536X10.1088/2040-8978/18/7/075608] proposed an experimental arrangement for collimation testing by comparing the period of two different self-images produced by a single diffraction grating. Following their approach, we propose a testing procedure based on correlation coefficient (CC) for efficient detection of variation in the size and fringe width of the Talbot self-images and thereby the collimation position. When the beam is collimated, the physical properties of the self-images of the grating, such as its size and fringe width, do not vary from one Talbot plane to the other and are identical; the CC is maximum in such a situation. For the de-collimated position, the size and fringe width of the self-images vary, and correspondingly the CC decreases. Hence, the magnitude of CC is a measure of degree of collimation. Using the method, we could set the collimation position to a resolution of 1 μm, which relates to ±0.25 μ radians in terms of collimation angle (for testing a collimating lens of diameter 46 mm and focal length 300 mm). In contrast to most collimation techniques reported to date, the proposed technique does not require a translation/rotation of the grating, use of complicated phase evaluation algorithms, or an intricate method for determination of period of the grating or its self-images. The technique is fully automated and provides high resolution and precision.

Joint Optimization of Power Allocation and Channel Ratio for Offloading in NOMA-HetNets

Abstract: Surge in number of cellular users and data-intensive applications require the traditional cellular networks to evolve towards a more promising heterogeneous cellular networks (HetNets). Offloading in HetNets alleviates congestion on the overloaded cellular network where the femto base stations (FBS) acts as offloading spots. The offloaded user (OU) is paired with the user available at the FBS (called as pairing user (PU)) and served using non-orthogonal multiple access. Two parameters namely, power allocation factor (PAF), i.e., the power to be allocated to the OU, and channel ratio (CHR), i.e., the ratio of channel gain between the OU and the PU play a crucial role in determining the ergodic rate achieved by the OU. If the PAF and the CHR are not optimally selected, it results in degradation in overall rate performance. This work jointly optimizes the PAF and the CHR to maximize the ergodic rate performance of the OU. The impact of optimized and non-optimized parameters on the performance of OU is studied to prove the advantage of using optimized scenario for the OU. An increase of upto 3 times is observed in the ergodic rate and sum ergodic rate by using the optimized parameters.

A simple low cost latent fingerprint sensor based on deflectometry and WFT analysis

Abstract: In criminal investigations, latent fingerprints are one of the most significant forms of evidence and most commonly used forensic investigation tool worldwide. The existing non-contact latent fingerprint detection systems are bulky, expensive and require environment which is shock and vibration resistant, thereby limiting their usability outside the laboratory. In this article, a compact, full field, low cost technique for profiling of fingerprints using deflectometry is proposed. Using inexpensive mobile phone screen based structured illumination, and windowed Fourier transform (WFT) based phase retrieval mechanism, the 2D and 3D phase plots reconstruct the profile information of the fingerprint. The phase information is also used to confirm a match between two fingerprints in real time. Since the proposed technique is non-interferometric, the measurements are least affected by environmental perturbations. Using the proposed technique, a portable sensor capable of field deployment has been realized.

Traffic Grooming in PCE-based Architecture Combined with RWA Utilizing Dynamic Fiber State Information

Abstract: Wavelength routing in the backbone of pure optical networks is the future. Wavelength division multiplexing and generalized multi-protocol label switching are the control plane technologies imbibed in futuristic pure optical networks. To improve the overall connection blocking probability of pure optical networks, efficient information scheduling algorithm is required to be imbibed with the in-use dynamic routing and wavelength assignment techniques. The traffic scheduling algorithm which has been introduced in this research work decreases the blocking probability of the connections in pure optical networks by assigning weights to every connection request according to certain connection parameters. The above results in noticeable improvements in the resource utilization of pure optical networks and can be practically implemented in present day and future pure optical telecommunication networks.

Performance Analysis of Offloading in NOMA-HetNets using Imperfect CSI

Abstract: The increase in number of cellular users had lead to the evolution from the traditional cellular networks to the more efficient heterogeneous cellular networks (HetNet) to handle the traffic. Offloading plays a vital role in handling the traffic from the congested macro base station by handing users to the less congested femto base stations (FBS). Further, non-orthogonal multiple access (NOMA) has proved to be efficient for the future generation networks. In this work, we study the offloading in HetNets, where the FBS tier serves the users using NOMA. Imperfect channel state information (CSI) is considered to analyze the outage probability of offloaded user, since, in practice CSI estimation requires significant system overhead, especially when the number of users are large. Hence, for practical systems, the analyses with imperfect CSI is more relevant. Some important observations regarding offloading to FBS tier with NOMA based on imperfect CSI are drawn. The analytical results are validated using Monte Carlo simulations.

Packet Scheduling Algorithm in LTE/LTE-Advanced-based Cellular Networks

Abstract: Cellular networks are ever evolving and have incorporated state-of-the-art technologies. These networks have been primarily operating on second generation, and thereafter migrating to third generat...

An Iterative Transmitted Reference UWB Receiver for Joint ToA and Data Symbols Estimation

Abstract: In impulse radio ultra-wideband (IR-UWB) literature, simple transmitted reference (TR) autocorrelation receiver has been analyzed for data symbol detection. However, TR receiver is neither energy efficient nor data transmission rate efficient due to transmission of two pulses per data symbol. In this paper, we propose an iterative TR (ITR) UWB receiver for the joint time of arrival (ToA) and data symbol estimation. The proposed ITR receiver uses only single reference pulse for a burst of data symbols. The ITR receiver estimates a new reference pulse from the burst of data symbols' pulses to further enhance the signal-to-noise ratio (SNR) of UWB system. Hence, the proposed ITR receiver has high energy efficiency and data rate transmission efficiency with improved SNR as compared to a TR receiver. Further, the proposed ITR receiver is implemented at sub-Nyquist rate to overcome the high sampling rate analog-to- digital converter. The ITR receiver's ToA and data symbol estimation performance is analyzed for the binary phase shift keying modulated UWB system in standard IEEE 802.15.4a channels in the presence of additive white Gaussian noise.

Virtual optical encryption using phase shifted digital holography and RSA algorithm

Abstract: Optical image encryption is one of the most promising technologies being investigated in the field of data communication, information technology and cloud computing. In this paper, a novel image encryption system based on virtual optical technique, phase shifted digital holography and RSA public key exchange is proposed. In the system, the encryption keys include the wavelength of the laser beam, focal length of the test lens, defocusing distance and scaling factor. The plain text image is encrypted to a cipher by using a phase shifted hologram function. The decryption process involves the phase calculation using phase shifting and sequential line scan algorithms. The keys are exchanged between sender and receiver by using RSA key exchange algorithm. To determine accuracy of the information retrieved by the proposed technique; the mean square error is calculated between the original image and retrieved image.

An IEEE 802.22 transceiver framework and its performance analysis on software defined radio for TV white space

Abstract: With rapid increase in new applications and services, there is huge demand for internet bandwidth. Several researchers around the world have found that, majority of licensed bands (mostly terrestrial TV band) are either unused or underused. These underutilized bands allocated for TV transmission are known as TV white space (TVWS). For effective utilization of TVWS, the IEEE 802.22 is proposed. The IEEE 802.22 wireless regional area network (WRAN) is the latest standard for effective utilization of TV bands. This standard is based on orthogonal frequency division multiplexing with various modulation techniques to provide different data rates. In this paper, an implementation framework for physical layer of IEEE 802.22 WRAN standard for normal mode is demonstrated and analyzed. This transceiver is implemented using the National Instruments Laboratory Virtual Instrument Engineering Workbench programming software on the National Instruments universal software radio peripheral 2952R. We have also analyzed different blocks of IEEE 802.22 based on their execution time, and identify the critical blocks of IEEE 802.22 that should be optimized for real-time applications for commercial product development and field deployments. We have also highlighted the difference between theoretical and practical performance of the considered error control codes for IEEE 802.22 specified block size. Additionally, various covariance based spectrum sensing methods are also analyzed for real-world environment.

Comparison of 3D sensing algorithms for single shot fringe projection profilometry

Abstract: Phase demodulation algorithms from single fringe pattern have been used widely due to their capability of sensing and measuring dynamic objects. In this paper, the comparison of single shot fringe demodulation algorithms for smooth and complex objects having discontinuities have been demonstrated. Fourier transform (FT) and windowed Fourier transform (WFT) algorithms have been used to extract the 3D phase from the modulated fringe pattern. Since, WFT uses Gaussian filter window at each pixel position to retrieve phase information, hence, it is suitable to extract phase for classifying objects having discontinuities, however due to spectrum leakage at discontinuities, FT causes error and are unable to detect correct phase information for such objects. The merits and demerits of both techniques have been discussed.