Department Publications

Multiple antenna techniques that allow energy beamforming have been looked upon as a possible candidate for increasing the transfer efficiency between the energy transmitter (ET) and the energy receiver in wireless power transfer. This paper introduces a novel scheme that facilitates energy beamforming by utilizing received signal strength indicator (RSSI) values to estimate the channel. First, in the training stage, the ET will transmit using each beamforming vector in a codebook, which is predefined using a Cramer-Rao lower bound analysis. RSSI value corresponding to each beamforming vector is fed back to the ET, and these values are used to estimate the channel through a maximum likelihood analysis. The results that are obtained are remarkably simple, requires minimal processing, and can be easily implemented. The paper also validates the analytical results numerically, as well as experimentally, and …

Activity recognition in videos in a deep-learning setting-or otherwise-uses both static and pre-computed motion components. The method of combining the two components, while keeping the burden on the deep network less, still remains uninvestigated. Moreover, it is not clear what the level of contribution of individual components is, and how to control the contribution. In this paper, we use a combination of convolutional-neural-network-generated static features and motion features in the form of motion tubes. We propose three schemas for combining static and motion components: based on a variance ratio, principal components, and Cholesky decomposition. The Cholesky-decomposition-based method allows the control of contributions. The ratio given by variance analysis of static and motion features matches well with the experimental optimal ratio used in the Cholesky decomposition-based method. The …

A 5-D depth–velocity filter is proposed for enhancing moving objects in noisy light field videos (LFVs) (also known as plenoptic videos). The proposed filter consists of an ultra-low complexity 5-D IIR depth filter and a 5-D FIR velocity filter. The 5-D IIR depth filter is employed to denoise a noisy LFV. The denoised LFV is then utilized to estimate the 3-D apparent velocity of the moving object of interest. The 5-D FIR velocity filter is designed based on the estimated 3-D apparent velocity and is used to enhance the moving object of interest while attenuating other interfering moving objects. Experimental results confirm the effectiveness of the proposed 5-D depth–velocity filter compared to previously reported 5-D depth–velocity filters.

A low-complexity 2-D FIR trapezoidal filter is proposed for enhancing broadband plane waves. Motivated by the design technique of 1-D interpolated FIR filters, the proposed filter is realized by cascading a low-complexity spatiallyupsampled 2-D FIR filter having a trapezoidal passband and a low-complexity 2-D FIR masking filter having a parallelogram passband. Experimental results confirm that the proposed filter provides 74% reduction of the computational-complexity compared to conventional 2-D FIR fan and conventional 2-D FIR trapezoidal filters without deteriorating the performance in enhancing 2-D broadband plane waves distorted by strong interference and noise signals.

This paper introduces a novel traffic reduction method for Networked Control Systems (NCS) called Deadband Error Modulation (DEM). The deadband modifies the periodic dynamics of Delta Modulation (DM) based techniques such as our previously proposed Event Triggered Adaptive Differential Modulation (ETADM). Like ETADM it can be used for encoding individual scalar elements of a vector (i.e., the state vector or control input). It is also robust to bounded packet drops.

Screen content coding (SCC) extension to High Efficiency Video Coding (HEVC) offers substantial compression efficiency over the existing HEVC standard for computer generated content. However, this gain in compression efficiency is achieved at the expense of further computational complexity with several resource hungry coding tools. Hence, extension of SCC to HEVC hardware encoders can be challenging. This paper presents resource efficient hardware designs for two key SCC tools, Intra Block Copy and Palette Coding. Moreover, a new hash search approach is proposed for Intra Block Copy, while a hardware friendly palette indices coding scheme is suggested for Palette Coding. These designs are targeted to achieve the throughput necessary for an 1080p 30 frames/s encoder, and incurs coding loss of 11.4% and 5.1% respectively in all intra configurations. The designs are synthesized for a Virtex-7 …

Most of the intrusion detection and prevention systems (NIDS/NIPS) are utilizing signature based matching which makes use of a stored rule base for distinguishing malicious network traffic. Dynamic rule-base updates has become a requirement due to the increasingly large number of new attack types identified every day, while the downtime associated with rule base updates has become a major drawback in hardware based Network Intrusion Prevention Systems. In addition, the NIPS are facing the challenge of expanding their throughput to cope with the ever growing high bandwidth requirement. This paper presents a novel scalable architecture for a NIPS with stateful packet inspection. The implementation is capable of processing Snort signatures and also analyzing packet streams to detect attacks with TCP segment manipulation. The system ensures run-time rule reconfigurability, which eliminates the risk of …

A high-gain non-isolated DC-DC converter is proposed with a inversely coupled inductor and a voltage lift cell. Energy stored in the leakage inductance of the coupled inductor is recycled through a voltage lift cell to obtain high voltage conversion ratio. The operation of the proposed converter is explained using its equivalent circuits which are used to derive static gain expression. The operation of the proposed converter is analyzed with non-ideal components to predict their influence on voltage conversion ratio and the efficiency. The operation of the proposed converter is validated using software simulation under ideal and non-ideal conditions.

An ultra-low complexity three-dimensional (3-D) linear-phase infinite-extent impulse response (IIR) velocity filter is proposed for attenuating moving artifacts in videos while enhancing objects moving on smooth approximately-linear trajectories. The proposed 3-D linear-phase IIR velocity filter consists of an ultra-low complexity 3-D wide-angle linear-phase IIR cone filter bank between two two-dimensional (2-D) spatial variable-shift filters. The ultra-low complexity 3-D wide-angle linear-phase IIR cone filter bank consists of a one-dimensional (1-D) temporal modified discrete Fourier transform filter bank and 2-D spatial allpass, IIR highpass and allstop filters. A typical 3-D linear-phase IIR velocity filter of order , applied to enhance a heavily corrupted test video signal, requires only 26 real multiplications and 60 real additions to process a sample and provides a scene-complexity-independent signal-to …

Many real world stochastic processes are non-stationary, which means that the probability distribution that generates data samples is time-varying. In the context of machine learning, this phenomenon is known as concept drift. It is important that machine learning models are able to adapt to concept drift in order to prevent degradation in accuracy. In this paper, we present two algorithms for drift detection and adaptation. Drift is measured by continuously tracking a difference metric between probability distributions estimated from two sample windows preceding a time point. High values for the difference metric indicates that concept drift has occurred, and the model must be adapted. Adaptation is done by training a new model for the drifted process, and adding it to an ensemble of models. Previously trained models are retained, and their weights in the ensemble are adjusted to reflect similarity with the current …

Purpose Automatic Optical Inspection (AOI) systems, used in electronics industry have been primarily developed to inspect soldering defects of Surface Mount Devices (SMD) on a Printed Circuit Board (PCB). However, no commercially available AOI system exists that can be integrated to a desktop soldering robotic system, which is capable of identifying soldering defects of Through Hole Technology (THT) solder joints along with the soldering process. In our research, we have implemented an AOI platform that is capable of performing automatic quality assurance of THT solder joints in a much efficient way. In this paper, we have presented a novel approach to identify soldering defects of THT solder joints, based on the location of THT component lead top. This paper presents the methodologies that can be used to precisely identify and localize THT component lead inside a solder joint. Design/methodology/approach We have discussed the importance of lead top localization and presented a detailed description on the methodologies that can be used to precisely segment and localize THT lead top inside the solder joint. Findings It could be observed that the precise localization of THT lead top makes the soldering quality assurance process more accurate. A combination of template matching algorithms and colour model transformation provide the most accurate outcome in localizing the component lead top inside solder joint, according to the analysis carried out in this paper. Research limitations/implications When the component lead top is fully covered by the soldering, the implemented methodologies will not be able to identify the actual …

A novel multidimensional spatio-temporal signal processing algorithm is proposed for depth-velocity filtering in 5-D light field videos along with a tutorial review of light field video spectra and the general architecture of associated 5-D depth-velocity filters. A 5-D FIR filter having a hyperfan-shaped passband which can selectively enhance the spectra of moving objects in light field videos based on their depth and motion trajectory is employed. A 5-D hyperfan-shaped passband is highly desired to achieve enhanced spatio-temporal selectivity over a wide range of lower frequencies. Experimental results are provided by using a light field videos captured using a Lytro light-field camera and mean structural similarity index is used to verify the effectiveness of the proposed 5-D FIR hyperfan depth-velocity filter.

A throughput analysis is conducted for a large scale peer-to-peer wireless network whose devices are capable of operating in both full- and half-duplex modes, using the tools of stochastic geometry. Each device selects its operating duplex mode based on the distance to its partner node. In both duplex modes, the energy consumption and the hardware configurations of the nodes are made equivalent for fair comparisons between full-duplex and half-duplex operations. Using the results of the analysis, an approach is proposed to determine a distance threshold value for duplex mode selection, and the proposed distance threshold can be computed offline. It is found that the throughput performance of the hybrid full-/half-duplex network generated with the proposed distance threshold based duplex mode selection technique outperforms both the pure half-duplex and pure full-duplex network settings for most …

Software industry has shown an exponential growth during the last decade with regards to technology development. The prime aim of the software industry is to deliver high quality software to the end user satisfying the clients as per the agreed norms of the business. Hence, software testing has become an important phase in the software life cycle, ensuring the ultimate product quality. The purpose of this study is to examine whether there is a relationship between testing constraints and test types executed in software companies. The research expects to provide recommendations to use test types effectively. A conceptual model was developed and three hypotheses were derived based on the extensive literature review carried out. According to the results it can be claimed that there is a negative strong relationship between testing constraints and the level of test type execution. Also there is a positive strong …

We present a simulation study of a cooperate car following application implemented by the Wireless Access for Vehicular Environments (WAVE) protocol stack, which uses the MAC and Physical layers defined by the IEEE 802.11p protocol. This is a simple Intelligent Transportation Systems (ITS) application which forms the foundation for autonomous driving. As with many safety-critical ITS applications, cooperate car following uses beaconing as the primary means of communication. The beacon frequency and the transmit power of the mobile nodes are considered as the key communication parameters, while the vehicle density is considered as the key traffic parameter. The two main factors affecting the performance, the end-to-end delay and the packet loss, are studied for different scenarios defined by the above parameters. Results indicate how the application performance may be improved by adapting the …

We consider a single-input-single-output (SISO) system with quadrature phase shift keying (QPSK) modulation and derive an easy-to-evaluate expression for the symbol error probability (SEP) when a general n-bit phase quantization is used at the receiver. We further evaluate the expressions asymptotically to characterize the diversity order and the quantization penalty at high signal-to-noise ratios (SNRs). We observe that the system with n-bit phase quantization achieves full diversity order of one when n > 2. Numerical examples are used to verify the analysis.

Accurate attitude estimation in high dynamic motion scenarios like unmanned aerial vehicle navigation or human motion and magnetically disturbed indoor environments requires compensation of accelerometer disturbances as well as magnetometer disturbances. This paper proposes a novel algorithm for accelerometer disturbance rejection by adaptive estimation of accelerometer measurement covariance matrix online. Magnetic disturbances are generally lasting long compared to accelerometer disturbances which are generally short term in indoor navigation environments. Novel two step Kalman filter update method is proposed to separate attitude correction from heading correction. The magnetometer is used only for heading update such that the attitude estimation is not affected by errors in magnetometer measurement. Performances of the proposed algorithms are shown by using real world sensor data.

Highly flexible FPAA and FPGA based universal sensor node design targeting researchers is discussed in this paper. The reconfigurable system is capable of supporting up to three low power analog sensors and two digital sensors in parallel. This facilitates dynamic configurability and remote monitoring by connecting the device to the internet. The design can be utilized in development of remote sensing devices to be establish at locations where frequent repairing and maintenance is difficult. Compensability for aging, adjustability to different environments, flexibility are key advantages of this system.

There exists some common bottlenecks among the many available Software Defined Networking (SDN) controllers. Of these, the current analysis uses the Floodlight software controller to identify bottlenecks. The analysis has implemented these bottlenecks in a Field Programmable Gate Array (FPGA) in order to assess its feasibility. Thereafter, a Hybrid SDN controller has been developed. Generally Hybrid SDN refers to a networking approach where traditional networking and SDN protocols are used and operated in the same environment. Hybrid in this paper context refers to a controller which is developed both on software and hardware platforms in order to achieve a higher scalability which is a current issue existing in software controller, and thereby overcoming the identified bottlenecks. The analysis has offloaded computational intensive models to an FPGA and tested for performance. These performance figures have then been compared against the performance figures as of a stand-alone software controller.

The aim of this study is to design a Home Automation system by interfacing Power Line Communication (PLC) with GSM communication which would enable the user to control appliances by sending commands via SMS. A communication model based on Star Topology is utilized in this home automation system which can be scaled at a low cost. The communication system facilitates secured communication by using BlumGoldwasser cryptosystem. The communication system employs a master Central Control System placed at the switch board and slave receiver nodes in household appliances. This system was planned from the outset to make as simpler and cost effective as possible so that it would be affordable to more households in low income countries. The system was tested in a lab environment at a maximum distance of 20 m and the operation was verified. Subsequently, Signal levels were obtained at …

This paper presents a comprehensive framework to analyze the impact of aggregate interference from an underlay clustered Device-to-Device (D2D) network on the performance of its primary cellular network, when different power control schemes are used at the D2D network. A single base station, located at the center, operates with a cellular network and a D2D network, modeled using a homogeneous spatial Poisson Point Process and a Poisson Cluster Process, respectively. Using this system, the cellular network performance is examined under three power control schemes used by the D2D network namely, no power control, path loss inversion and channel inversion. For each scheme, the coverage probability of the cellular network is analyzed. Numerical results indicate that the cellular network performance is greatly dependent on the D2D system parameters such as density, size of a cell, number of …

Pulse Transit Time (PTT)/Pulse Wave Velocity (PWV) measurement based non-invasive blood pressure estimation is of much interest at present, as it enables continuous monitoring of blood pressure in a more comfortable manner compared to traditional cuff based methods, without hindering natural user behavior. In this study we have investigated the possibility of estimating blood pressure using PTT without the need of external calibrations. The parametric model developed in our previous research is improved eliminating the need of initial calibration which requires external blood pressure measurement from a reference device. The results suggest that there is a potential of developing calibrationless blood pressure estimation methods based on PTT/PWV which may require further testing and validation.

A complex activity is a temporal composition of sub-events, and a sub-event typically consists of several low level micro-actions, such as body movement of different actors. Extracting these micro actions explicitly is beneficial for complex activity recognition due to actor selectivity, higher discriminative power, and motion clutter suppression. Moreover, considering both static and motion features is vital for activity recognition. However, optimally controlling the contribution from static and motion features still remains uninvestigated. In this work, we extract motion features at micro level, preserving the actor identity, to later obtain a high-level motion descriptor using a probabilistic model. Furthermore, we propose two novel schemas for combining static and motion features: Cholesky-transformation based and entropy-based. The former allows to control the contribution ratio precisely, while the latter obtains the optimal …

Power control schemes are proposed for a full-duplex (FD) device-to-device (D2D) network operating as an underlay of a primary FD network. As networks with different quality of service (QoS) requirements may coexist in future heterogeneous networks, it is assumed that the underlay D2D network is operating with best effort QoS provisioning, while the primary FD network requires guaranteed QoS. A centralized power control (CPC) solution is proposed by casting the power control problem as a convex optimization problem. Furthermore, a heuristic distributed power control (DPC) solution is proposed to reduce information feedback overhead. It is found that the heuristic DPC achieves D2D user data rate that is within 87% and 80% of that provided by the CPC scheme in 3-node and 2-node FD primary network, respectively.

This extended abstract critically investigates the possible new compliance standards of academic and research ethics that may result from the implementation ofthe Right to Information Act (RTIA) ofSri Lanka. The RTIA was enacted in quick succession to the 19lh Amendment of the 1978 Constitution of Sri Lanka enacted on 4th August 2016. The 19th Amendment made the right to information from public bodies a constitutional right (Article 14A). The provisions of the RTIA could have profound legal ramifications on the way in which research is conducted in Sri Lanka: especially with respect to non medical research, that involves private data.