Overlapped-MIMO Radar Waveform Design for Coexistence With Communication Systems

This paper explores an overlapped-multiple-input multiple-output (MIMO) antenna architecture and a spectrum sharing algorithm via null space projection (NSP) for radar-communications coexistence. In the overlapped-MIMO architecture, the transmit array of a collocated MIMO radar is partitioned into a number of subarrays that are allowed to overlap. Each of the antenna elements in these subarrays have signals orthogonal to each other and to the elements of the other subarrays. The proposed architecture not only improves sidelobe suppression to reduce interference to communications system, but also enjoys the advantages of MIMO radar without sacrificing the main desirable characteristics. The radar-centric spectrum sharing algorithm then projects the radar signal onto the null space of the communications system's interference channel, which helps to avoid interference from the radar. Numerical results are presented which show the performance of the proposed waveform design algorithm in terms of overall beampattern and sidelobe levels of the radar waveform and finally shows a comparison of the proposed system with existing collocated MIMO radar architectures.Comment: accepted at IEEE WCN

Off-grid electrification with solar home systems: An appraisal of the quality of components

Solar home systems (SHS) are seen as an attractive option for off-grid electrification in rural areas in developing countries. The combined effect of declining photovoltaic module costs and success in micro-finance has resulted in increased SHS installations in emerging economies in Asia such as Bangladesh. Majority of the SHS components are now manufactured locally with the exception of PV cells. Considering the role of component quality in SHS performance, technical quality of four key SHS components: solar panel, battery, charge controller and lamp circuit (inverter) from market-leading manufacturers were evaluated in this study in laboratory settings, against national and international standards. All of the tested components met some evaluation criteria in their respective categories but none met all. Key performance failures were found to be related to inverter efficiency, reverse polarity protection in charge controllers and battery capacity, which are critical for optimum performance of the system. Findings in this study point towards an ineffective regulatory mechanism for quality assurance and the protection of consumer rights, which needs to be rectified for maintaining public confidence and sustaining the growth of SHS based off-grid electrification

On The Non-linear Distortion Effects in an OFDM-RoF Link

Radio over Fiber (RoF) system is a promising technique for microcell and picocell applications for deployment of future ubiquitous wireless data networks. However, the performance of RoF systems can be severely degraded due to non-linear effects in the channel. Also, Orthogonal Frequency Division Multiplexing (OFDM), as a standard for broadband wireless networks, is being proposed for deployment with RoF systems to facilitate the total performance of a system. In this research, at first, the performance of OFDM-based RoF link with Mach-Zehnder modulator distortion effects has been analyzed at 5.8 GHz. Evaluation of mean-squared error of the proposed OFDM-RoF system was carried out to compare with the conventional single carrier system based RoF link after the modulator distortion case and also for fixed Signal to Noise Ratio (SNR) of 20 dB using undistorted OFDM signal. Later, nominal and offset biasing pre-distortion techniques are applied in proposed system to linearize the OFDM-RoF link. Thus, finally a comparison between the aforementioned pre-distortion techniques applied showed important observation in terms of distortion-free dynamic range and SNR to choose offset pre-distortion technique for our proposed system

Leveraging Smartphone Sensors for Detecting Abnormal Gait for Smart Wearable Mobile Technologies

Walking is one of the most common modes of terrestrial locomotion for humans. Walking is essential for humans to perform most kinds of daily activities. When a person walks, there is a pattern in it, and it is known as gait. Gait analysis is used in sports and healthcare. We can analyze this gait in different ways, like using video captured by the surveillance cameras or depth image cameras in the lab environment. It also can be recognized by wearable sensors. e.g., accelerometer, force sensors, gyroscope, flexible goniometer, magneto resistive sensors, electromagnetic tracking system, force sensors, and electromyography (EMG). Analysis through these sensors required a lab condition, or users must wear these sensors. For detecting abnormality in gait action of a human, we need to incorporate the sensors separately. We can know about one's health condition by abnormal human gait after detecting it. Understanding a regular gait vs. abnormal gait may give insights to the health condition of the subject using the smart wearable technologies. Therefore, in this paper, we proposed a way to analyze abnormal human gait through smartphone sensors. Though smart devices like smartphones and smartwatches are used by most of the person nowadays. So, we can track down their gait using sensors of these intelligent wearable devices

Performance Analysis of 2.5 Gbps PIN and APD Photodiodes to Use in Free Space Optical Communication Link

Ever since ancient times, people had a principle need to communicate with one another. This need created interests in device based communication system for sending messages from one distant place to another. Optical communication methods were of special interest among the many systems. In this paper, investigation has been done on two different photodiodes PIN and APD for use as a receiver in free space fiber optical link. We have considered 2.5 Gbps PIN and APD photo diodes for our experiment. From the simulation, we found that APD with single mode fiber gives the better performance over PIN. However, the value of Q-factor is maximum when APD has been used as the receiving photodiode at 1550nm wavelength and minimum when PIN diode has been used as receiving photodiode at 1550nm wavelength. We used OptiSystem and MATLAB software for our investigatio

On the error vector magnitude as a performance metric and comparative analysis

In this paper, we present the error vector magnitude (EVM) as a a figure of merit for assessing the quality of digitally modulated telecommunication signals. We define EVM for a common industry standard and derive the relationships among EVM, signal to noise ratio (SNR) and bit error rate (BER). We also compare among the different performance metrics and show that EVM can be equivalently useful as signal to noise ratio and bit error rate. A few simulation results are presented to illustrate the performance of EVM based on these relationships