Dong-You Choi

Comparative Study of Antenna Designs for RF Energy Harvesting

In the last few years, several antenna designs of rectenna that meet various objectives have been proposed for use in RF energy harvesting. Among various antennas, microstrip patch antennas are widely used because of their low profile, light weight, and planar structure. Conventional patch antennas are rectangular or circular in shape, but variations in their basic design are made for different purposes. This paper begins with an explanation and discussion of different designs, put forward with an aim of miniaturization, harmonic rejection, and reconfigurability. Finally, microstrip patch structured rectennas are evaluated and compared with an emphasis on the various methods adopted to obtain a compact rectenna, harmonic rejection functionality, and frequency and polarization selectivity.

A Novel Cross Layer Intrusion Detection System in MANET

Intrusion detection System forms a vital component of internet security. To keep pace with the growing trends, there is a critical need to replace single layer detection technology with multi layer detection. Different types of Denial of Service (DoS) attacks thwart authorized users from gaining access to the networks and we tried to detect as well as alleviate some of those attacks. In this paper, we have proposed a novel cross layer intrusion detection architecture to discover the malicious nodes and different types of DoS attacks by exploiting the information available across different layers of protocol stack in order to improve the accuracy of detection. We have used cooperative anomaly intrusion detection with data mining technique to enhance the proposed architecture. We have implemented fixed width clustering algorithm for efficient detection of the anomalies in the MANET traffic and also generated different types of attacks in the network. The simulation of the proposed architecture is performed in OPNET simulator and we got the result as we expected.

Design and performance of an efficient rectenna incorporating a fractal structure

We present an efficient rectenna capable of harvesting ambient radio frequency energy to obtain utilizable direct current power at a frequency of 2.45GHz. The rectifying antenna incorporates a fractal structure at its antenna section. The unique space-filling property of fractals is implemented to develop an antenna with a significant size reduction. A Sierpinski carpet, which is a simple and effective fractal design, is edge-fed and iterated up to the 3rd order. The received signal from the 2nd-order fractal iterated patch antenna is rectified using a rectifier circuit that uses an HSMS 8202 Avago Technologies, California, USA diode. The realized rectenna has the capacity to exhibit a maximum efficiency of 57% at an input power level of 20dBm. Simulations for the fractal iterated patch antennas and rectifier circuit are performed in Ansoft HFSS, Ver. 10 Ansys, Canonsburg, USA and ADS Agilent Technologies, Mississauga, Canada, respectively. The simulated antenna and rectenna are experimentally tested to verify the simulation results. The simulation and experimental results for the antenna and rectenna design are found to be in good agreement with each other. Copyright

Kerberos based authentication for inter-domain roaming in wireless heterogeneous network

An increased demand in ubiquitous high speed wireless access has led integration of different wireless technologies provided by different administrative domains creating truly a heterogeneous network. Security is one of the major hurdles in such network environment. As a mobile station moves in and out of the coverage area of one wireless network to another, it needs to be authenticated. The existing protocols for authentication of a mobile station are typically centralized, where the home network participates in each authentication process. It requires home network to maintain roaming agreement with all other visiting networks. Moreover, the round trip time to home network results high latency. This paper is focused on developing authentication protocol for wireless network irrespective of the technologies or the administrative domain. We propose a secure protocol which adopts strong features of Kerberos based on tickets for rigorous mutual authentication and session key establishment along with issuance of token so that the mobile station can have access to not only the roaming partner of home network but also to the roaming partner of previous visited networks. The performance evaluation and comparative analysis of the proposed protocol is carried out with the already implemented standard protocols and most remarkable research works till date to confirm the solidity of the results presented.

A New Fractal-Based Miniaturized Dual Band Patch Antenna for RF Energy Harvesting

The growth of wireless communications in recent years has made it necessary to develop compact, lightweight multiband antennas. Compact antennas can achieve the same performance as large antennas do with low price and with greater system integration. Dual-frequency microstrip antennas for transmission and reception represent promising approach for doubling the system capacity. In this work, a miniaturized dual band antenna operable at 2.45 and 5.8 GHz is constructed by modifying the standard microstrip patch antenna geometry into a fractal structure. In addition to miniaturization and dual band nature, the proposed antenna also removes unwanted harmonics without the use of additional filter component. Using a finite-element-method-based high frequency structure simulator (HFSS), the antenna is designed and its performance in terms of return loss, impedance matching, radiation pattern, and voltage standing wave ratio (VSWR) is demonstrated. Simulation results are shown to be in close agreement with performance measurements from an actual antenna fabricated on an FR4 substrate. The proposed antenna can be integrated with a rectifier circuit to develop a compact rectenna that can harvest RF energy in both of these frequency bands at a reduction in size of 25.98% relative to a conventional rectangular patch antenna.

Multipath Routing Scheme for Wireless Multihop Network

Due to the increasing popularity and availability of portable wireless devices, which constitute of wireless mobile ad hoc network and sensor network, demand efficient routing protocols. On-demand routing protocols adapt well with dynamic topologies of the wireless ad hoc networks, due to their lower control overhead and quick response to route break. In this paper, we discuss on the design approaches for a typical multipath routing algorithm in mobile ad hoc network (MANET). And we propose a multipath routing for MANET. The proposed scheme is basically intended for highly dynamic ad hoc networks in which communication faults occur on a frequent basis. We conduct simulation for such a scheme, which shows that performance of the proposed scheme is better in term of various performance metrics.

Proposed M-Payment System Using Near-Field Communication and Based on WSN-Enabled Location-Based Services for M-Commerce

Advances in mobile communication and information technology have resulted in wireless sensor network (WSN) systems in which mobile phones (smart phones) can be used to conduct a wide variety of commercial, social, entertainment, and file-sharing transactions. In particular, mobile commerce (m-commerce) allows users to conduct payment, business, and service transactions over portable mobile devices. This trend has been enhanced by the development of near-field communication (NFC) technology and the increased market for NFC-embedded (smart phones). NFC technology is a standards-based wireless communication technology that allows data to be exchanged between devices located a few centimeters apart, such as radio-frequency identification (RFID tags and readers). To refine the m-commerce process in the NFC-based mobile environment, we study NFC and location-based services propose a WSN-hosted m-payment system based on these technologies.

Design of modified Sierpinski fractal based miniaturized patch antenna

Miniaturization of microstrip patch antenna by incorporating fractal geometry is presented in this paper. The unique space-filling property of fractals is explored to develop a novel patch antenna operating at 2.45 GHz with significant size reduction than its conventional counterpart. An inset-fed patch antenna is taken as initiator of proposed fractal design. The fractal iteration of Sierpinski Carpet in modified form is performed up to 2nd iteration. The antennas are designed using finite element method based HFSS and their performances are demonstrated in terms of Return loss, radiation pattern, gain plot, smith chart, and VSWR. Experimental results of Sierpinski Carpet iterations and their comparison with the generator shows size reduction of 31% and 32% in 1st and 2nd iteration correspondingly, without affecting antenna performances such as reflection loss, impedance matching and antenna gain.

Kerberos Based Authentication Protocol with Improved Identity Protection in 3G Network

Wireless mobile communication imposes certain security risks due its underlying medium - airwave; in spite of its popularity. Different authentication protocols have been devised to strengthen the security for wireless communication. The authentication and key agreement (AKA) adapted by 3G networks is one of the widely appreciated protocols. However, even such protocol is vulnerable to threats like false base station attack and user identity theft under certain conditions. In this paper, we propose an authentication protocol for 3G network to overcome such threats by adopting the strong features of Kerberos based on tickets for rigorous mutual authentication and deploying a secret token between Mobile Station and Home Location Register for identity protection. The results show that under almost same operational cost, the proposed protocol can provide better security in terms of mutual authentication and identity protection.

Characterization of Rain Specific Attenuation and Frequency Scaling Method for Satellite Communication in South Korea

The attenuation induced by rain is prominent in the satellite communication at Ku and Ka bands. The paper studied the empirical determination of the power law coefficients which support the calculation of specific attenuation from the knowledge of rain rate at Ku and Ka band for Koreasat 6 and COMS1 in South Korea that are based on the three years of measurement. Rain rate data was measured through OTT Parsivel which shows the rain rate of about 50 mm/hr and attenuation of 10.7, 11.6, and 11.3 dB for 12.25, 19.8, and 20.73 GHz, respectively, for 0.01% of the time for the combined values of rain rate and rain attenuation statistics. Comparing with the measured data illustrates the suitability for estimation of signal attenuation in Ku and Ka band whose validation is done through the comparison with prominent rain attenuation models, namely, ITU-R P.618-12 and ITU-R P. 838-3 with the use of empirically determined coefficient sets. The result indicates the significance of the ITU-R recommended regression coefficients of rain specific attenuation. Furthermore, the overview of predicted year-wise rain attenuation estimation for Ka band in the same link as well as different link is studied which is obtained from the ITU-R P. 618-12 frequency scaling method.