Department Publications

With the popularization of a quad high-definition/4K video being dependent on the availability of real-time High Efficiency Video Coding (HEVC) decoders, hardware implementations have become more appealing due to their superior performance and low power consumption. In this paper, a field-programmable gate array (FPGA)-based hardware implementation of a 4K 30 frames/s real-time HEVC decoder is presented. An elastically pipelined decoder architecture is used to absorb variations in processing time and each pipeline stage is optimized to use available FPGA primitives. FPGA-specific challenges in managing critical path delays to achieve a target operating frequency of 150 MHz required many architectural novelties, such as exploitation of the sparsity of transformed coefficient matrix, single-cycle reference pixel processing in intra prediction, and flexible block ordering in deblocking filter/sample …

Five-dimensional (5-D) light field video (LFV) (also known as plenoptic video) is a more powerful form of representing information of dynamic scenes compared to conventional three-dimensional (3-D) video. In this paper, the 5-D spectrum of an object in an LFV is derived for the important practical case of objects moving with constant velocity and at constant depth. In particular, it is shown that the region of support (ROS) of the 5-D spectrum is a skewed 3-D hyperfan in the 5-D frequency domain, with the degree of skew depending on the velocity and depth of the moving object. Based on this analysis, a 5-D depth-velocity digital filter to enhance moving objects in LFVs is proposed, described and implemented. Further, by means of the commercially available Lytro light-field camera, LFVs of real scenes are generated and used to test and confirm the performance of the 5-D depth-velocity filters for enhancing such …

We investigate the problem of automatic action recognition and classification of videos. In this paper, we present a convolutional neural network architecture, which takes both motion and static information as inputs in a single stream. We show that the network is able to treat motion and static information as different feature maps and extract features off them, although stacked together. We trained and tested our network on Youtube dataset. Our network is able to surpass state-of-the-art hand-engineered feature methods. Furthermore, we also studied and compared the effect of providing static information to the network, in the task of action recognition. Our results justify the use of optic flows as the raw information of motion and also show the importance of static information, in the context of action recognition.

A 5-D IIR depth-velocity filter is proposed for enhancing objects moving on linear trajectories, with constant velocity and at constant depth, in light field videos (also known as plenoptic videos). The passband of the proposed filter is a plane in the 5-D frequency domain and is realized by cascading three first-order 5-D IIR filters having 4-D hyperplanar passbands of appropriate orientations. Numerical simulation results are presented to confirm the performance of the proposed filter.

In this paper, we focus on the ergodic downlink sum-rate performance of a system consisting of a set of heterogeneous users. We study three user selection schemes to group near-orthogonal users for simultaneous transmission. The first scheme is a random selection policy that achieves fairness, but does not exploit multi-user diversity. The second scheme is a greedy selection policy that fully exploits multi-user diversity, but does not achieve fairness, and the third scheme achieves fairness while partially exploiting multi-user diversity. We also consider two beamforming methods for data transmission, namely, maximum-ratio transmission and zero-forcing beamforming. In all scheduling schemes studied in the paper, there is a key parameter that controls the degrees of orthogonality of channel directions between co-scheduled users. We focus on optimally setting this parameter for each scheduling scheme such that …

This paper presents an implementation technique for the 40Gbps Ethernet Physical Coding Sublayer (PCS). The functionality of the 40Gbps Ethernet PCS is specified in the IEEE 802.3ba standard's clause 82. The paper also presents a scheme of verification of this implementation using an FPGA setup.

The spectrum of an object moving in 5-D light field videos (also known as plenoptic videos) with constant velocity and at non-constant depth is analyzed. Based on this analysis, a novel 5-D IIR adaptive depth-velocity filter is proposed for enhancing such objects. The time-variant coefficients of the proposed 5-D IIR adaptive depth-velocity filter are derived in closed form. Numerical simulation results confirm the effectiveness of the proposed filter compared to 3-D IIR adaptive velocity filters and 4-D IIR adaptive depth filters.

Five-dimensional (5-D) light field video (LFV) (also known as plenoptic video) is a more powerful form of representing information of dynamic scenes compared to conventional three-dimensional (3-D) video. In this dissertation, the spectra of moving objects in LFVs are analyzed, and it is shown that such moving objects can be enhanced based on their depth and velocity by employing 5-D digital filters, what is defined as depth-velocity filters. In particular, the spectral region of support (ROS) of a Lambertian object moving with constant velocity and at constant depth is shown to be a skewed 3-D hyperfan in the 5-D frequency domain. Furthermore, it is shown that the spectral ROS of a Lambertian object moving at non-constant depth can be approximated as a sequence of ROSs, each of which is a skewed 3-D hyperfan, in the 5-D continuous frequency domain. Based on the spectral analysis, a novel 5-D finite-extent impulse response (FIR) depth-velocity filter and a novel ultra-low complexity 5-D infinite-extent impulse response (IIR) depth-velocity filter are proposed for enhancing objects moving with constant velocity and at constant depth in LFVs. Furthermore, a novel ultra-low complexity 5-D IIR adaptive depth-velocity filter is proposed for enhancing objects moving at non-constant depth in LFVs. Also, an ultra-low complexity 3-D linear-phase IIR velocity filter that can be incorporated to design 5-D IIR depth-velocity filters is proposed. To the best of the author’s knowledge, the proposed 5-D FIR and IIR depth-velocity filters and the proposed 5-D IIR adaptive depth-velocity filter are the first such 5-D filters applied for enhancing moving objects in …

The outage probability of a two-hop coordinated decode-and-forward relay network is investigated. The case of two interfering cells is considered. This is analogous to the case when network coordination is performed with the dominant cochannel interfering cell. Different levels of network coordination are studied and their performances are compared. Exact expressions are derived for of the system for each coordination method. The impact of user location randomness on the outage probability is investigated.

We present a sensor platform to be mounted on the white cane used by the visually impaired. This can estimate the direction of user movement and enable the user to detect obstacles lying on the path in advance. The sensor platform contains an ultrasonic sensor and an IMU (Inertia Measurement Unit). We develop a model to estimate distances to obstacles in the path and their width based on sensor measurements. The model is demonstrated to have an overall accuracy of 84%, with accuracy as high as 90% for obstacles within 50cm in front of the user. Knowledge of obstacle locations and their size in advance, would enable us to guide visually impaired persons to deviate from their path and return to it after the obstacle has been passed.

Large debris created after natural disasters restrict access to inner parts of affected regions and slows down disaster relief operations. Power shovels are often used to clear wreckage but the process can take a lot of time. Moreover, it is dangerous to involve human workers in such conditions due to loose debris collapsing and causing severe damage. To speedup access to inner areas, instead of removing obstacles, they can be surmounted with the assistance of a carefully maneuvered power shovel arm. In this paper, an autonomous obstacle surmounting technique for an unmanned power shovel is proposed. Out of different sequences, the one that optimizes the total energy consumption is selected as the best candidate for surmounting a given obstacle by dynamic simulations. The experiments conducted using a miniaturized power shovel show the effectiveness of the proposed method.

The massive volume of video and image data, compels them to be stored in a distributed file system. To process the data stored in the distributed file system, Google proposed a programming model named MapReduce. Existing methods of processing images held in such a distributed file system, requires whole image or a substantial portion of the image to be streamed every time a filter is applied. In this work an image filtering technique using MapReduce programming model is proposed, which only requires the image to be streamed only once. The proposed technique extends for a cascade of image filters with the constrain of a fixed kernel size. To verify the proposed technique for a single filter a median filter is applied on an image with salt and pepper noise. In addition a corner detection algorithm is implemented with the use of a filter cascade. Comparison of the results of noise filtering and corner detection …

Two novel computationally efficient implementations for 3-D FIR cone filters are proposed in this paper. In the proposed implementations, the well-known 1-D quadrature mirror cosine modulated and 1-D directly designed temporal filter banks are cascaded with 2-D FIR circularly symmetric lowpass spatial filters to approximate the cone-shaped passband. Furthermore, the 3-D FIR frustum filters are derived from the proposed 3-D FIR cone filter implementations. The proposed implementations provide additional 2 dB signal-to-interference-and-noise ratio improvement compared to previously reported 3-D FIR cone and frustum filter implementations with reduced or equivalent computational complexity.

Large debris created after natural disasters restrict access to inner parts of affected regions, and slows down disaster relief operations. Power shovels are often used to clear wreckage but the process can take a lot of time. Moreover, it is dangerous to involve human workers operating heavy machinery in such unstable conditions. To speedup access to inner areas, obstacles can be surmounted with the assistance of carefully maneuvered power shovel arm, instead of removing them. In this work, an autonomous obstacle surmounting technique for an unmanned power shovel is proposed. Out of different sequences, the one that optimizes the total energy consumption is chosen as the best candidate for surmounting a given step-like obstacle. Dynamic simulation results show the effectiveness of the proposed method.

The outage probability of a two-hop coordinated decode-and-forward relay network is investigated. Relay coordination is performed only with the dominant interferer. Different levels of network coordination are studied and their performances are compared. Exact expressions are derived for the outage probability of a particular mobile user for each coordination scheme. Asymptotic outage probability is derived to identify the diversity and coding gains for each coordination scheme.

When establishing object correspondence across non-overlapping cameras, the existing methods combine separate likelihoods of appearance and kinematic features in a Bayesian framework, constructing a joint likelihood to compute the probability of re-detection. A drawback of these methods is not having a proper approach to reduce the search space when localizing an object in a subsequent camera once the kinematic and appearance features are extracted in the current camera. In this work we introduce a novel methodology to condition the location of an object on its appearance and time, without assuming independence between appearance and kinematic features, in contrast to existing work. We characterize the linear movement of objects in the unobserved region with an additive Gaussian noise model. Assuming that the cameras are affine, we transform the noise model onto the image plane of …

The inverse transform function of the HEVC Decoder has grown greatly in complexity with the addition of larger transform sizes and recent works have focused on efficient architectures that can achieve the required throughput. In this work we make the observation that a majority of the coefficients in a typical transform operation is zero, and therefore has no impact on the final outcome. We propose an architecture that can efficiently operate on such sparse matrices and introduce a scheduling strategy which completes a 2D IDCT with bare minimum iterations, with the added advantage of being able to integrate seamlessly with the entropy decoder without a coefficient reordering buffer. Experiments show that although the performance of this approach is scalable with the bit rate, a 120 MHz operating frequency is sufficient to handle QHD @ 48 Mbps, which is less than one third of the frequency requirement of prior work.

An ergodic rate analysis is presented for relay coordination schemes of two-hop decode-and forward relay networks. A simplified two-cell network model is used in the analysis. This model is related to a practically significant case, where the relay coordination is implemented with the cell which causes the most dominant cochannel interference level. Closed-form expressions are derived for the ergodic rate of the system. Simplified approximations are derived to approximate the ergodic rate behaviour in the asymptotically high signal-to-noise ratio regime.

The demand for high data rate wireless services has grown tremendously. The demand is expected to grow further at an increased pace. The scarcity of the usable radio frequency spectrum is a major bottleneck to cater to the growing demand for high data rate wireless services. Current cellular wireless networks rely on deploying small cells as a possible solution to cater to the growing demand. However, this practice has resulted in severe co-channel interference (CCI) levels in cellular networks. The first phase of this thesis investigates the impact of CCI on relay networks and distributed antenna systems, which are included in recent wireless standards such as long-term evolution advanced (LTE-A). The analytical results derived for system performance metrics, such as the outage probability and the ergodic rate, are used to obtain valuable insights for system design. The second stage of this thesis research …

Pitch and airspeed responses of a medium scale UAV were identified using the prediction error method. Data collection was conducted with an active closed loop autopilot control system. A naive SISO open loop transfer function was estimated using the parametric direct approach. Since its predictability was not significant, better estimators were developed using MISO parametric direct, and SISO parametric indirect method. The model validations were done to quantify their predictability.

Power shovels are used to clear wreckage after natural disasters but the process can consume a lot of time. Furthermore, operating such heavy machines in those circumstances is very dangerous for the involved human workers. To speed up access to inner parts of disaster stricken areas, obstacles can be surmounted with the assistance of carefully maneuvered arm, instead of removing them. In this paper, an autonomous obstacle surmounting technique for an unmanned power shovel is proposed. Out of different sequences, the one that optimizes the total energy consumption is chosen as the best candidate for surmounting a given step-like obstacle. Simulation and experiment results show the effectiveness of the proposed method.