Showing papers by "Sabah M. Ahmed published in 2018"

Wideband Cognitive Radio Networks Based Compressed Spectrum Sensing: A Survey

Abstract: Spectrum sensing is a core function at cognitive radio systems to have spectrum awareness. This could be achieved by collecting samples from the frequency band under observation to make a conclusion whether the band is occupied, or it is a spectrum hole. The task of sensing is becoming more challenging especially at wideband spectrum scenario. The difficulty is due to conventional sampling rate theory which makes it infeasible to sample such very wide range of frequencies and the technical requirements are very costly. Recently, compressive sensing introduced itself as a pioneer solution that relaxed the wideband sampling rate requirements. It showed the ability to sample a signal below the Nyquist sampling rate and reconstructed it using very few measurements. In this paper, we discuss the approaches used for solving compressed spectrum sensing problem for wideband cognitive radio networks and how the problem is formulated and rendered to improve the detection performance.

Bio-inspired jumping maneuver for launching flapping wing micro air vehicles

Abstract: This paper presents the design and simulation of a jumping mechanism as a means of flight initiation in Flapping Wing Micro Air Vehicles (FWMAV) inspired by birds. Most flying birds take off for flight from standing or perching position at low air speed. A lightweight 4-bar leg mechanism has been designed using dimensional synthesis by motion generation. Graphical and analytical methods are established to determine the kinematic dimensions that fulfill some prescribed take-off maneuvers. Link cross sections have been optimized to reduce weight. The jumping leg has been tested with an efficient aerodynamic model that accurately predicts unsteady flapping wing aerodynamic characteristics just after launching. Transition of forces from leg to wings has been analyzed. For a jumping angle of about 50 degrees at 10m/s the 33.3 g ornithopter model gains momentum and reaches steady state flight at a velocity close to the initial value.

Vision-Based Control of a Quad-rotor Manipulation System

Abstract: Using teleoperation process to drive the quadrotor Manipulation System to pick and place the object in a critical application is very difficult and slow process because of human capabilities so that one of the possible solutions to overcome this problem is to use vision-based control to automatically pick and place the object. In this paper we presented the vision-based control of a quadrotor manipulation system (QMS) that consists of 2-serial link robotic arm attached to the bottom of a quadrotor and a camera attached to end-effector which acts as a vision sensor to form eye-in-hand architecture. Image-Based Visual Servoing (IBVS) is used to produce a desired task space trajectory to the inverse kinematics model that generates a desired quadrotor/joint space trajectory for PD-controller to automatically pick and place the object. The proposed system uses 6 actuators only to perform the required 6-DOF trajectory. This minimum number of actuators is useful to facilitate carrying high payload. The vision-based control of a quadrotor manipulation system of the proposed system was designed and tested using MATLAB/SIMULINK program. The simulation results indicate that this system is able to perform automatic pick and place task for 3D objects.

Convex lenses horn antenna microwave hyperthermia scheme

Abstract: This paper presents a new preclinical microwave hyperthermia system based on the combination among horn antenna and convex lenses. The horn antenna is designed to resonate at 3 GHz which is reported for hyperthermia therapy. Two convex lenses are designed and incorporated with the designed horn antenna and the reported breast phantom. The proposed system aims to heat up the tumor region above 42 ° C while keeping the surrounding area temperature unchanged as possible to protect them from damage. Specific Absorption Rate (SAR) and breast phantom thermal distribution are studied with and without using lenses at different inclination angles. The proposed system has the advantage of heating up different zones separately while keeping other regions temperature unchanged. Simulation results show that, the breast temperature can be elevated by 10 ° C above the normal body temperature.

Primary User Detection in Cognitive Radio Networks Over Fading Channel Using Compressed Sensing

Abstract: Compressed spectrum sensing has gained considerable importance among researchers in the field of concern as a solution for wideband cognitive radio networks. Recently, published works on detecting primary users' signals presented sustainable results by using small compression ratios over the AWGN channel. To the best of our knowledge, since the performance of compressed measurements based detection has not been investigated yet over fading channels, the current study, therefore, presents the performance of compressed measurements based energy detection over Rayleigh fading channel. The proposed work has been implemented by means of MATLAB software. In comparison with the traditional compressed energy detection over the Rayleigh fading channel, the results show that our proposed technique is better in detection performance.