T. Rama Rao

Regression-based trust model for mobile ad hoc networks

The focus of this study is to propose a generalised trust-model over routing protocols in mobile ad hoc networks (MANETs). It is observed that the presence of malicious nodes is a critical factor affecting the network performance in an ad hoc network. The novelty in the approach is that the notion of trust can be easily incorporated into any routing protocol in MANETs. The vector auto regression based trust model is introduced to identify malicious nodes that launch multiple attacks in the network. The proposed trust model is incorporated over ad hoc on-demand distance vector (AODV) routing protocol and optimised link state routing (OLSR) protocol in MANETs. The performance evaluations show that by carefully setting the trust parameters, substantial benefit in terms of throughput can be obtained with minimal overheads. The computed trust and confidence values are introduced into the path computation process of the ad hoc routing protocols. It was observed that the nodes in the network were able to learn the malicious activities of their neighbours and hence, alternate trustworthy paths are taken to avoid data loss in the network, with trade-offs in end-to-end packet delay and routing traffic.

FPGA Implementation of FFT Algorithm for IEEE 802.16e (Mobile WiMAX)

algorithm has the same multiplicative complexity as the radix-4 algorithm, but retains the butterfly structure of radix-2 algorithm.

Performance Investigations with Antipodal Linear Tapered Slot Antenna on 60 GHz Radio Link in a Narrow Hallway Environment

The performance of wireless communication systems is predominantly dependent on propagation environment and respective radiating antennas. Due to the shorter wavelength at Millimeter Wave (MmW) frequencies, the propagation loss through surroundings in indoor environments is typically very high. To improve the channel capacity and to reduce inter-user interference, a high gain directional antenna is desired at MmW frequencies. Traditional antennas used in MmW devices are not suitable for low-cost commercial devices due to their heavy, bulky and expensive configurations. This paper focuses on design and development of a very compact (44.61 mm × 9.93 mm × 0.381 mm) high gain Antipodal Linear Tapered Slot Antenna (ALTSA) utilizing Substrate Integrated Waveguide (SIW) technology at 60 GHz. Received signal strength (RSS), path loss (PL) and capacity are studied for MmW based wireless applications utilizing electromagnetic (EM) computations and Radio Frequency (RF) experiments in narrow hallway environment.

Prevention of flooding attacks in mobile ad hoc networks

The lack of any centralized infrastructure in mobile ad hoc networks (MANET) is one of the greatest security concerns in the deployment of wireless networks. Thus communication in MANET functions properly only if the participating nodes cooperate in routing without any malicious intention. However, some of the nodes may be malicious in their behavior, by indulging in flooding attacks on their neighbors. Some others may act malicious by launching active security attacks like denial of service. This paper addresses few related works done on trust evaluation and establishment in ad hoc networks. Related works on flooding attack prevention are reviewed. A new trust approach based on the extent of friendship between the nodes is proposed which makes the nodes to co-operate and prevent flooding attacks in an ad hoc environment. The performance of the trust algorithm is tested in an ad hoc network implementing the Dynamic Source Routing (DSR) protocol.

A switched beam antenna array with butler matrix network using substrate integrated waveguide technology for 60 GHz communications

A switched beam antenna array based on substrate integrated waveguide (SIW) technology is designed and simulated for 60 GHz communications. The antenna array is fed by 4×4 planar butler matrix network in order to achieve the switched beam characteristic. The use of SIW technology offers a low cost and a planar design. Each of the components is designed and verified through simulations in electromagnetic field simulation tool, CST MWS. The components are integrated later to form the switched beam antenna array. The return losses and isolations are lower than -10 dB from 57 GHz to 64 GHz for all of the input ports. The peak gain for the switched beam antenna array is 16 dBi at 60 GHz.

Trust-based backpressure routing in wireless sensor networks

In this paper, we apply a vector autoregression VAR based trust model over the backpressure collection protocol BCP, a collection mechanism based on dynamic backpressure routing in wireless sensor networks WSNs. The backpressure scheduling is known for being throughput optimal. In the presence of malicious nodes, the throughput optimality no longer holds. This affects the network performance in collection tree applications of sensor networks. We apply an autoregression based scheme to embed trust into the link weights, so that the trusted links are scheduled. We have evaluated our work in a real sensor network testbed and shown that by carefully setting the trust parameters, substantial benefit in terms of throughput can be obtained with minimal overheads. Our results show that even when 50% of network nodes are malicious, VAR trust offers approximately 73% throughput and ensures reliable routing, with a small trade-off in the end-to-end packet delay and energy consumptions.

Design of a Quad Band Microstrip Antenna for Wearable Wireless Devices and investigations on substrate types and performance at various body sites

This work proposes a novel Quad Band Microstrip Antenna for Body Wearable Wireless Devices (BWWD). The designed antenna finds immense applications in general health monitoring utilizing wearable devices, sports health monitoring and observing military personnel in war field where monitoring bio-signals is the prime objective. Ultra high frequency (UHF) and Ultra wide band (UWB) technology adequately meet power, size and distance considerations for WBANs. The antenna designed operates at quad bands, resonating at 1.8 GHz, 2.4 GHz, 5.0 GHz and 8.9 GHz when placed on human body. They are the de-licensed, GSM, Wi-Fi and UWB. The antenna design considers the interaction of body tissues with the electromagnetic (EM) fields, which is different when compared to free space. The performance of the antenna is investigated at different places on the body and for different type of substrates. Most common and comfortable sites on body are chosen as anatomical sites for placement of WWD. A simplified, human body tissue layer model that is frequency dependent in its properties is used for simulations. Simulations are carried out using EM analysis tools.

Radio channel characteristics in an indoor corridor environment at 60 GHz for wireless networks

For the next generation wireless local area networks (WLANs) and wireless personal area networks (WPANs), 60 GHz radio channel propagation characteristics in typical indoor corridor environments are addressed in this paper using Matlab simulations of Ray-tracing, ITU-R model and full-3D Ray-tracing model of Wireless Insite. Values of the path gain (PG), rms delay spread (DS) and power delay profile (PDP) for omnidirectional and horn antennas are presented.

Design and Performance Analysis of a Penta-band Spiral Antenna for Vehicular Communications

Developments in automotive industries are increasing to deliver secured and pleasant journey by exchange of information among the vehicles, inside vehicles, between vehicle and with infrastructure utilizing wireless communication networks (WCN). To meet the requirements for various wireless applications, a new printed planar based circularly polarized penta-band spiral antenna with tapered feed is designed to cover the navigational frequencies viz., 1.2, 1.5 GHz and WCN frequencies viz., 2.4, 3.3 GHz and Dedicated Short Range Communication frequency 5.8 GHz for vehicular mobile communications. A 3D Electromagnetic (EM) tool is used for design and is validated via field measurements with Radio Frequency (RF) equipment. In order to validate the performance of the designed antenna, Received Signal Strength (RSS) experiments were conducted between two vehicles at 2.4 and 5.8 GHz in an open area and on road with a vehicle moving speed of 15 km/h. Further, path loss analysis is done for vehicular environments with line of sight condition are simulated using EM propagation tool and simulated results are compared with empirical model viz., ITU, Two-ray reflection, dual-slope model and COST 231 Walfisch Ikegami model.

A Novel Smiley Fractal Antenna (SFA) Design and Development for UWB Wireless Applications

Ultra Wideband (UWB) has been deliberated as a promising technology for short-range wireless communication with large unlicensed frequency band for commercial, enterprise private and public uses. Designing an antenna of compact size for portable wireless devices is one of the challenges especially for UWB based wireless communication technologies. In this paper, a novel Smiley Fractal Antenna (SFA), employed with N-notch feed and modified ground plane, is designed and developed to achieve the desired characteristics. The proposed antenna is of compact size with dimensions of 34× 32× 1. 6m m 3 ,f abricated on an FR-4 substrate wither =4 .4. The radiation pattern of the proposed antenna is omnidirectional with a maximum gain of 4.83 dB and efficiency of 93.55% obtained through 3D electromagnetic simulation software tools. The simulated results are compared with measured ones using RF equipment. The results obtained show that the proposed SFA is a suitable candidate for variety of UWB wireless communication applications.