S. Nandakumar

Bio: S. Nandakumar is an academic researcher from VIT University. The author has contributed to research in topics: Handover & Cognitive radio. The author has an hindex of 6, co-authored 22 publications receiving 92 citations.

Modeling and Performance Analysis of an Improved Data Channel Assignment (DCA) Scheme for 3G/WLAN Mixed Cells

Abstract: In this paper, we present an efficient data channel assignment (DCA) scheme for a mixed cell (i.e., a 3G cell with embedded WLANs). Our effort is essential to increase the data request (i.e., a call) handling capacity in 3G systems, with a ‘low request dropping probability’. In UMTS-first DCA scheme prefers 3G channel in dual coverage and reduces vertical handoffs from 3G to WLAN. But it deprives some users of high speed service of WLAN even when WLAN facility is available. On the contrary, a WLAN-first DCA scheme overcomes this problem by preferring WLAN system. But the overall call request dropping probability increases with increasing WLAN traffic and at some point, the benefit of WLAN cannot be achieved in a mixed cell. Further, most of the existing models do not consider the reality of non-identical WLAN-hotspots and bidirectional vertical handoffs, restricting the free mobility of the users across 3G and WLAN systems. We propose an improved DCA scheme based on WLAN-first access technique to maximize the usage of WLAN. The proposed model considers the reality of non-identical WLAN-hotspots and allows free mobility between 3G and WLAN. A proposed DCA scheme improves the dropping probability as blocked call request of WLAN are transferred to 3G. Our DCA scheme drops a request only when all the channels of both 3G and WLAN systems are busy. We derive an analytical model for proposed scheme and validate the same with a set of simulation results. We provide an extensive number of numerical results to show that our scheme performs far better than the existing models. The DCA modeling approach can be quite conveniently used for better planning of WLAN hotspots in the mixed cell.

QoS provisioning for mobile and fixed wireless real time multimedia services

Abstract: In this paper, a new admission control policy and bandwidth reservation scheme for IEEE 802.16e networks has been proposed. Admission control policy and bandwidth reservation scheme are designed in such a way that desired quality of service is achieved. IEEE 802.16e standard did not specify any bandwidth reservation scheme that provides quality of service (QoS) support for real-time services, especially for handover real-time ones. The bandwidth reservation schemes, which were not designed for 802.16e system dedicatedly, could also be applied to it. But their performance is our main concern. Bandwidth reservation scheme is done based on probability of handover at mobile station and probability of call arrival at mobile station. And also admission control policy is designed for the same. Algorithm is designed to evaluate the performance of bandwidth reservation scheme. The simulation results show that not only minimizes the new service flow (SF) blocking rate and the handover SF dropping rate, but also reduces the access delay of new real-time SF.

Dual Processor Based Centralized Device for Spectrum Handoff in Cognitive Radio Networks

Abstract: Wireless communication has been evidently proven to be the best source of communication technology. This has led to a rapid growth in this technology. This growth in the wireless communication technology has been done on the cost of the valuable resource spectrum which is depleting slowly. The time has shifted from Fixed to Dynamic allocation of spectrum. Cognitive Radio Networks (CRN) has been the emerging Dynamic scheme lately. CRNs allow the unlicensed user also termed as secondary user (SU) to utilize the licensed channel in the absence of the licensed users which are termed as primary users (PU). When a PU visits a channel that is currently being utilized by a SU, the channel needs to be vacated to switch to some other vacant channel in the spectrum. This switch of the channel is termed as spectrum handoff. It helps the system as a whole for better usage of the spectrum on the cost of the performance of the SU transmission increasing its data delivery time. This paper uses a centralized cognitive device in order to decrease the handoff latency of the SU. The centralized device used in this paper is dual processor based which helps in increasing the accuracy of the target channel selection process. The central cognitive device chooses the right channel for transmitting the data using the current channel status flag register in the memory of the device along with a probabilistic approach as presented in this paper. This novel technique improves the parameters such as accuracy, handoff latency, processor speed and processor memory.

IEEE Standard for Local and Metropolitan Area Networks Part 16: Air Interface for Fixed Broadband Wireless Access Systems Draft Amendment: Management Information Base Extensions

Abstract: This document provides updates to IEEE Std 802.16's MIB for the MAC, PHY and asso- ciated management procedures in order to accommodate recent extensions to the standard.

Adversarial Attacks in Modulation Recognition With Convolutional Neural Networks

Abstract: Deep learning (DL) models are vulnerable to adversarial attacks, by adding a subtle perturbation which is imperceptible to the human eye, a convolutional neural network (CNN) can lead to erroneous results, which greatly reduces the reliability and security of the DL tasks. Considering the wide application of modulation recognition in the communication field and the rapid development of DL, by adding a well-designed adversarial perturbation to the input signal, this article explores the performance of attack methods on modulation recognition, measures the effectiveness of adversarial attacks on signals, and provides the empirical evaluation of the reliabilities of CNNs. The results indicate that the accuracy of the target model reduce significantly by adversarial attacks, when the perturbation factor is 0.001, the accuracy of the model could drop by about 50 ${\%}$ on average. Among them, iterative methods show greater attack performances than that of one-step method. In addition, the consistency of the waveform before and after the perturbation is examined, to consider whether the added adversarial examples are small enough (i.e., hard to distinguish by human eyes). This article also aims at inspiring researchers to further promote the CNNs reliabilities against adversarial attacks.

Structural health monitoring of civil engineering structures by using the internet of things: A review

Abstract: Structural health monitoring (SHM) and damage assessment of civil engineering infrastructure are complex tasks. Structural health and strength of structures are influenced by various factors, such as the material production stage, transportation, placement, workmanship, formwork removal, and concrete curing. Technological advancements and the widespread availability of Wi-Fi networks has resulted in SHM shifting from traditional wire-based methods to Internet of Things (IoT)-based real-time wireless sensors. Comprehensive structural health assessment can be performed through the efficient use of real-time test data on structures obtained from various types of IoT sensors, which monitor several health parameters of structures, available on cloud-based data storage systems. The sensor data may be subsequently used for various applications, such as forecasting masonry construction deterioration, predicting the early-stage compressive strength of concrete, forecasting the optimum time for the removal of formwork, vibration and curing quality control, crack detection in buildings, pothole detection on roads, determination of the construction quality, corrosion diagnosis, identification of various damage typologies and seismic vulnerability assessment. This review paper summarizes the applications of the wireless IoT technology in the monitoring of civil engineering infrastructure. In addition, several case studies on real structures and laboratory investigations for monitoring the structural health of civil engineering constructions are discussed.