Department Publications

Application of depth-selective filtering to modulated-sparse light fields towards reducing the DSP and memory complexities in real-time light field processing is investigated. A modulated-sparse light field is obtained by spatially windowing an original 4-D light-field signal, which is subsequently processed by 4-D depth-selective filters to achieve planar focus and occlusion suppression. Multidimensional spectral properties of modulated-sparse light fields are explored and demonstrative examples with real light fields are provided to show that almost similar depth filtering and occlusion suppression performance can be achieved by processing such modulated-sparse light fields, leading to significant reduction in DSP hardware and memory complexities.

This paper presents a method for localizing an Unmanned Aerial Vehicle (UAV) using geo-referenced aerial images, in case of GPS failure. When flying in urban environments in low altitudes the inaccurate GPS localization has become a major problem. The proposed method fuses measurements from inertial sensors and visual odometer and perform image registration process using the images captured by the onboard down looking camera. A pre-built local orthomosaic map with geotagged aerial images is used for the registration. The problem of unreliable matches caused by the dynamic objects is addressed in our approach. The experiment results show that it is possible to localize the UAV in urban environments with a low margin of error by using our method.

This paper describes a hardware and software codesign approach for object detection and tracking algorithm which is based on modified ViBe background subtraction method and scale adaptable particle filtering algorithm. The modified ViBe performs with a close accuracy to the original work of ViBe but with less complexity and it outperforms the Mixture of Gaussian(MoG) method. Since the modified algorithm has a low off chip memory access requirement, the real time object detection in embedded level with the help of hardware acceleration techniques could be achieved. The implemented particle filtering algorithm is capable of adapting to the scale variation of the tracking objects. After careful investigation of the time consumption profile of each function in our algorithm, the complete algorithm was implemented in IoT edge devices targeted Avnet Ultra 96 development board which is based on Xilinx Zynq …

Indoor positioning by wireless means is of significant interest in a wide range of applications; Wi-Fi and Bluetooth Low Energy (BLE) are popular candidate wireless technologies for this. We present a novel BLE beacon placement algorithm that complements existing Wi-Fi infrastructure in a hybrid Wi-Fi/BLE positioning system. Composite signal strength measurements thus obtained, are used to derive machine learning models for location estimation. Our results show that positioning estimates at table-level granularity (0.9 m × 1.8 m) in a computer laboratory can be achieved with 97% accuracy. This is an improvement of 20% and 30% compared to Wi-Fi and BLE only techniques respectively.

Telecommunication sector is one of the technologically advanced sectors, globally. The mobile device market is always growing and it is very competitive. Counterfeit and substandard devices are collectively known as black market devices. Availability of black market and stolen mobile devices is a global issue. When buying a mobile device, most of the people focus on cost, brand and model. The important factors that represent the standard of mobile devices such as validity of International Mobile Equipment Identity (IMEI) and the Specific Absorption Rate (SAR) value are neglected. It is important to adhere to a proper policy framework and introduce systems such as Equipment Identity Registers (EIRs) to minimize the usage of black market and stolen mobile communication devices. Mobile device blocking and regulation have become difficult tasks due to the unavailability of proper systems and policies. This has …

A real-time directional sensing system is proposed for 2.4 GHz ISM band by exploiting the concept of spatiotemporal spectral white spaces. The proposed system consists of a 16-element patch antenna array, an FFT-based multi-beam beamformer and an energy detector. Our system operates at the baseband with quadrature sampling. Furthermore, digital architectures for two energy detectors that employ integrate-and-dump circuits are presented. With the multi-beam beamformer, the first energy detector can be employed to directional sensing and the second can be employed for both directional and spectral sensing of radio frequency sources. The multi-beam beamformer having 16 beams and the energy detectors are implemented on a ROACH-2 based FPGA system with a 160 MHz clock. With an 8-point temporal FFT, the second energy detector provides approximately 20 MHz bandwidth per temporal FFTbin …

In this letter an intuitive measurement based approximation for packet switched network traffic in backbone links is presented. It consists of a sum of independent non-identical Bernoulli sources. The resulting sum has a Poisson binomial distribution which can be approximated to a skewed Gaussian distribution at the asymptote. It can be further approximated to a binomial distribution for predicting congestion by estimating the number of users of the network. The results are verified using samples of traffic data from 42 academic and research institutions.

Most of the electronic devices do not perform well in high temperature. In wafer fabrication, data propagation through thick metallic chamber walls need more transmitting power for successful data transmission. Measuring and transmitting temperature in closed metallic high temperature environment is a challenging issue. In this paper, a scheme to sense, process and transmit the data through fully closed and thick Aluminum chamber is proposed. The system is capable of sensing high temperature while handling for power fluctuations. Temperature is measured using tiny RTD resistors placed in different 7 locations up to 350 degree Celsius. The data is transmitted as radio-waves using ASK and FSK modulation techniques at the rate of 1 kbps. Processed demodulated data at the receiver-end provides the power supply voltage level, RTD locations ID, and the temperature in different locations of the IC inside the …

This paper proposes a spectrum selection scheme and a transmit power minimization scheme for a device-to-device (D2D) network cross-laid with a cloud radio access network (CRAN). The D2D communications are allowed as an overlay to the CRAN as well as in the unlicensed industrial, scientific and medical radio (ISM) band. A link distance based scheme is proposed and closed-form approximations are derived for the link distance thresholds to select the operating band of the D2D users. Furthermore, analytical expressions are derived to calculate the minimum required transmit power to achieve a guaranteed level of quality of service in each operating band. The results demonstrate that the proposed scheme achieves nearly 50% power saving compared to a monolithic (purely overlay or purely ISM band) D2D network.

A low-complexity wideband transmit beamformer is proposed using a digitally-fed uniform linear array of broadband Vivaldi antennas operating in the S-band. The proposed transmit beamformer employs a novel DSP feeding network based on a transmit-mode 2-D sparse finite-extent impulse response (FIR) filter having a planar passband in the 2-D frequency-wavenumber space. Electronic beam steering is achieved by changing the filter coefficients defined in closed-form and hard-thresholding (HT) is employed to obtain a sparse 2-D impulse responses of the filter. Full-wave electromagnetic simulations are used to obtain the far-field beam patterns produced by the 2-D sparse FIR filter in the frequency range 2-2.8 GHz for wideband signals with 33% fractional bandwidth. Computational complexity, beam directionality and side-lobe performance are investigated with varying HT along with quantitative comparisons …

Quad High Definition (QHD/4K) Virtual Reality (VR) Headsets with High Dynamic Range (HDR) technology will provide a superior experience to users. Wireless VR headsets are attractive as it offers freedom on mobility and higher user comfort. Cloud and workstations are capable of rendering 4K HDR scenes in real-time with ease. The efficient transmission of these scenes through wireless network requires the use of compression techniques. Decoding 4K HDR frames at VR devices in real-time is a challenge. Given the power and memory efficiency of the hardware decoders, in this paper we propose JPEG-XT Profile C based hardware architecture to decode 4K HDR frames in real-time. We employ novel methods for merged base and residual layer decoding pipelines, design of probability-based hybrid Huffman lookup table architecture and sparsity aware inverse zig-zag processing. Our decoder is implemented …

This paper has addressed the problem of transporting a long object from a given starting location to an end location using leader-follower robot formation in an environment filled with obstacles. Only the leader robot has the authority to make decisions. It possesses the main controller and is capable of navigating through an unknown environment using the data provided by on-board sensors. In the proposed system, a vision-based feedback method is combined with an explicit control method that oversights the virtual trailer between the leader and the follower. The parameters required to maintain a constant distance between the two robots are computed by the leader and transmitted to the follower directly. A fiducial marker is mounted on the front of the follower robot and is captured by a camera attached to the leader robot. Information exchanging methods based only on impedance control can be expensive …

Travelling along routine paths on foot is an exhausting and mundane task. Current personal mobility vehicles (PMVs), which address this issue, are driven manually and are too heavy to be carried by the user when needed. As a solution to this, an autonomous, self-balancing, lightweight, compact and low-cost PMV is developed. The device is capable of simultaneously self-balancing and navigating autonomously in an indoor environment. Moreover, it can be manually controlled using the developed smart mobile phone application. Self-balancing, localization, navigation and obstacle avoidance are achieved in real time using on-board sensors and processing units. Systematic experiments are carried out with the developed PMV in typical indoor environments in order to assess the robustness of the above features. The results show that the robot is able to successfully achieve its navigation tasks both with and …

Neural processing along the ascending auditory pathway is often associated with a progressive reduction in characteristic processing rates. For instance, the well-known frequency-following response (FFR) of the auditory midbrain, as measured with electroencephalography (EEG), is dominated by frequencies from~ 100 Hz to several hundred Hz, phase-locking to the stimulus waveform at those frequencies. In contrast, cortical responses, whether measured by EEG or magnetoencephalography (MEG), are typically characterized by frequencies of a few Hz to a few tens of Hz, time-locking to acoustic envelope features. In this study we investigated a crossover, cortically generated responses time-locked to continuous speech features at FFR-like rates. Using MEG, we analyzed high-frequency responses (70-300 Hz) to continuous speech using neural source-localized reverse correlation and its corresponding temporal response functions (TRFs). Continuous speech stimuli were presented to 40 subjects (17 younger, 23 older adults) with clinically normal hearing and their MEG responses were analyzed in the 70-300 Hz band. Consistent with the insensitivity of MEG to many subcortical structures, the spatiotemporal profile of these response components indicated a purely cortical origin with~ 40 ms peak latency and a right hemisphere bias. TRF analysis was performed using two separate aspects of the speech stimuli: a) the 70-300 Hz band of the speech waveform itself, and b) the 70-300 Hz temporal modulations in the high frequency envelope (300-4000 Hz) of the speech stimulus. The response was dominantly driven by the high frequency …

A novel content caching strategy is proposed for a cache enabled device-to-device (D2D) network where the user devices are allowed to communicate using millimeter wave (mmWave) D2D links (> 6GHz) as well as conventional sub 6 GHz cellular links. The proposed content placement strategy maximizes the successful content delivery probability of a line of sight D2D link. Furthermore, a heuristic algorithm is proposed for efficient content delivery. The overall scheme improves the successful traffic offloading gain of the network compared to conventional cache-hit maximizing content placement and delivery strategies. Significant energy efficiency improvements can also be achieved in ultra-dense networks.

The widespread use of high definition cameras for surveillance and related tasks has given rise to the concept of edge computing as transmitting and processing video streams in real time have become challenging. However, edge computing at low power and lower cost is difficult with general purpose processor hardware inside cameras. Finding a solution that meets the above requirements and demonstrates flexibility to handle diverse conditions is challenging. In this paper, we propose a coprocessor architecture which is specifically designed to perform machine vision related operations at the edge using very long instruction word (VLIW) architecture. It also supports multiple vision algorithms in the same hardware platform while supporting runtime reconfigurability, architectural flexibility, and extensibility. The system was practically realized on ZedBoard and verified for correct functionality and accuracy at 148.5 …

As silicon technology is scaling down, leakage power dissipation has become more significant among the all power dissipation mechanisms of complementary metal oxide semiconductor (CMOS) circuits. Minimum leakage vector (MLV) is a standby leakage power reduction technique for the combinational logic circuits. Though power gating is an excellent leakage power reduction technique compared to MLV standalone power gating technique has some inherent drawbacks like higher wake up time and circuit state loss. In this paper we combine MLV and power gating to achieve more leakage power reduction compared to MLV while mitigating the mentioned drawbacks of full circuit power gating. Instead of full circuit power gating, we developed a simple algorithm which runs in linear time to identify the gates with higher leakage power dissipation around which power gating can be carried out once combination …

We address the problem of identification of spherical objects, which are inside a layered structure by wireless sensing. Here, the backscatter response is used to identify the objects. It is a task, which is improved as the resolution gets higher. Therefore, to have a better resolution we consider the THz band. However, in the THz surface scattering expands the backscatter response of the layered structure in time. Thus, the backscatter response of the objects and the layered structure superimpose each other. This becomes even more severe due to the limited bandwidth at the receiver. In consequence, the exploitation of sophisticated signal separation methods for improved object identification is required. Therefore, we propose morphological component analysis (MCA), semi-blind MCA (MCA-SB) and singular value decomposition (SVD) methods. The MCA and MCA-SB rely on the sparse representation of signals …

This paper proposes a new method of estimation of the wet biomass of three floating aquatic plants, Spirodela polyrhiza, Lemna minor and Azolla pinnata. The method uses a homogeneity measure known as the J-value to detect the texture of the fronds of the plants from the uniform water surface. The proposed method is called J-value thresholding (JVT) and is highly accurate compared to the alternative green layer extraction (GLE). The average accuracy under normal illumination for the proposed method is 91.59% for Spirodela polyrhiza, 80.11% for Lemna minor and 77.4% for Azolla pinnata. Furthermore, it is robust to different illumination levels with the Pearson correlation coefficient of the estimates of different illumination levels being above 95%. When used to obtain the growth rate of each plant specie through linear regression, the result from the proposed method is highly consistent with the ground truth of …

In this paper, we introduce a novel algorithm that can dramatically reduce the number of antenna elements needed to accurately predict the direction of arrival (DOA) for multiple input multiple output (MIMO) radar. The new proposed algorithm predicts the received signal of a large antenna setup using reduced number of antenna by using coupled dictionary learning. Hence, this enables the MIMO radar to resolve more paths, which could not be resolved by the fewer antennas. Specifically, we overcome the problem of inaccurate DOA estimation due to a small virtual array setup. For example, we can use dictionary learning to predict 100 virtual array elements using only 25. To evaluate our algorithm, we used multiple signal classification (MUSIC) as a DOA estimation technique to estimate the DOA for non coherent multiple targets. The results show that using the predicted received signal, the proposed algorithm …

This paper describes the development of a quadrotor fixed-wing hybrid unmanned aerial vehicle (UAV). By combining the flying qualities of quadrotor UAV and that of fixed-wing UAVs it is possible to achieve superior flying qualities. This way, the vertical take-off and landing capability of quadrotors and the long endurance of fixed-wing UAVs have been put together, while eliminating the disadvantages of both of these UAV types. The proposed hybrid drone has shown exciting performance in taking-off, cruising and landing fully autonomously. Control transition from quadrotor to fixed-wing and backwards have been analyzed. Sky Scout fixed-wing drone has been used to build the hybrid UAV, and the performance has been successfully demonstrated through flight tests. This paper precent the complete design of a quadrotor fixed-wing hybrid aerial vehicle with modelling, simulation and experimental verification.