Browsing by Author "Wijenayake, C"

Now showing 1 - 13 of 13

item: Article-Full-text
Design and Implementation of 5-D IIR Depth Velocity Filters for Light Field Video Processing
(Institute of Electrical and Electronics Engineers Inc., 2019) Wijenayake, C; Liyanage, N; Edussooriya, C; Seatang, H; Agathoklis, P; Bruton, L
The design and hardware implementation of a lowcomplexity signal processing algorithm is proposed for real-time depth-velocity filtering in 5-D light field videos (LFVs). The proposed design is based on a stable 5-D infinite impulse response (IIR) digital filter having three cascaded sections, each synthesized using the concept of multidimensional passive network resonance. A novel semi-systolic hardware implementation is proposed. Each section of the filter is implemented and tested on a Xilinx Virtex-7 FPGA platform using Matlab based hardware co-simulation with both synthetic and real LFV signals. A realtime processing throughput of 467 LFV frames/s is implied with each section of the filter operating at 204, 164 and 115 MHz for input LFV frames of size 9×9×220×360.
item: Conference-Full-text
A low-complexity 2-d fir parallelogram filter for broadband beamforming with sparse linear arrays
(IEEE, 2023-12-09) Pakiyarajah, D; Edussooriya, CUS; Wijenayake, C; Madanayake, A; Abeysooriya, R; Adikariwattage, V; Hemachandra, K
Broadband beamformers designed as twodimensional (2-D) spatially-interpolated finite-extent impulse responses (FIR) filters, using a cascade structure, cannot employ sparse linear arrays despite significantly reducing the computational complexity. This happens due to the fact that the 2-D masking filter requires spatial samples equal to the spatial order at the input. Therefore, the output of the 2-D spatially-interpolated prototype filter should be computed for more than one spatial index. In order to address this limitation, we propose a 2-D spatially-interpolated FIR filter using a parallel structure. With the proposed structure, both 2-D spatially-interpolated prototype filter and the 2-D masking filter need to compute the output only for one spatial index, therefore allowing to employ sparse linear arrays. In order to support broadband beamforming, we design the 2-D FIR filter to have a parallelogram passband. Furthermore, we design the 2-D FIR filter to have linear phase response and to be optimal in the minimax sense. The simulation results confirm that the proposed 2-D FIR filter provides a considerable reduction in the number of antennas, compared to previously proposed 2-D FIR filters, with a slight degradation in the fidelity of enhanced broadband signals, which are distorted by strong radio frequency interference and noise signals.
item: Conference-Full-text
Minimax design of m-d complex-coefficient fir filters with nearly-constant low group delays
(IEEE, 2023-12-09) Pakiyarajah, D; Edussooriya, CUS; Wijenayake, C; Madanayake, A; Abeysooriya, R; Adikariwattage, V; Hemachandra, K
The optimal designs of multi-dimensional (M-D) complex-coefficient finite-extent impulse response (FIR) filters with low group delays predominantly consider only the minimization of the frequency response error. This leads to substantial deviation of the group delay from the desired constant group delay of such a filter, especially near the passband edges. In this paper, we propose a minimax design method for M-D complexcoefficient FIR filters with reduced group delay error. We incorporate constraints on phase response error while minimizing the frequency response error. We formulate the proposed minimax design method as a second-order cone programming problem. Design examples confirm that the proposed minimax design method significantly reduces the group delay error compared to previously proposed methods.
item: Conference-Full-text
Multi depth-velocity filters for enhancing multiple moving objects in 5-d light field videos
(IEEE, 2020-07) Liyanage, N; Jayaweera, SS; Edussooriya, CUS; Wijenayake, C; Madanayake, A; Agathoklis, P; Bruton, L; Ambikairajah, E; Weeraddana, C; Edussooriya, CUS; Abeysooriya, RP
A moving object in a five-dimensional (5-D) light field video (LFV) can be selectively enhanced using the depth and the velocity of the object. In this paper, a 5-D depth-velocity (DV) filter is proposed to enhance multiple moving objects at different depths and with different velocities in an LFV. The 5-D DV filter is designed as a cascade of an infinite-extent impulse response multi-depth filter and a finite-extent impulse response multi-velocity filter. Experimental results obtained with numerically generated and real LFVs indicate that more than 15 dB improvement in signal-to-interference ratio can be achieved with the proposed 5-D multi DV filter compared to previously proposed multi depth-only filters.
item: Conference-Abstract
Multi-beam 8 × 8 RF aperture digital beamformers using mMultiplierless 2-D FFT appro ximations
Kulasekera, S; Madanayake, A; Wijenayake, C; Bayer, FM; Suarez, D; Cintra, RJ
The two-dimensional (2-D) discrete Fourier transform (DFT) is widely used in digital signal processing (DSP) and computing applications. Fast Fourier transforms (FFTs) are widely used as low-complexity algorithms for the computation of the DFT as it reduces the required computation operations from O(N2) to O(N log2 N). The multiplicative complexity is used as a benchmark in comparing different algorithms as it affects the circuit complexity, chip area and power. This paper introduces a new class of multiplierless hardware algorithm consisting only of arithmetic adder circuits that closely approximates the 2-D version of the 8-point DFT. The paper discusses the theory behind the proposed new algorithm, with the DFT presented in the form of an 8 × 8 matrix. Furthermore it provide a multi-beam RF aperture application example where the 2-D DFT approximation has been used to closely obtain the antenna array patterns.
item: Conference-Full-text
Multi-Beam 8 × 8 RF Aperture Digital Beamformers Using Multiplierless 2-D FFT Approximations
(2015-08-03) Kulasekera, S; Madanayake, A; Wijenayake, C; Bayer, FM; Cintra, RJ
The two-dimensional (2-D) discrete Fourier transform (DFT) is widely used in digital signal processing (DSP) and computing applications. Fast Fourier transforms (FFTs) are widely used as low-complexity algorithms for the computation of the DFT as it reduces the required computation operations from O(N2) to O(N log2 N). The multiplicative complexity is used as a benchmark in comparing different algorithms as it affects the circuit complexity, chip area and power. This paper introduces a new class of multiplierless hardware algorithm consisting only of arithmetic adder circuits that closely approximates the 2-D version of the 8-point DFT. The paper discusses the theory behind the proposed new algorithm, with the DFT presented in the form of an 8 × 8 matrix. Furthermore it provide a multi-beam RF aperture application example where the 2-D DFT approximation has been used to closely obtain the antenna array patterns.
item: Article-Full-text
Multi-depth filtering and occlusion suppression in 4-D light fields: Algorithms and architectures
(Elsevier, 2020) Liyanage, N; Wijenayake, C; Edussooriya, C; Madanayake, A; Agathoklis, P; Bruton, LT; Ambikairajah, E
Low-complexity signal processing algorithms and reconfigurable digital hardware architectures are proposed for multi-depth filtering and occlusion suppression in 4-D light fields (LFs). The proposed multi-depth-pass (MDP) and multi-depth-reject (MDR) 4-D filters allow simultaneous enhancement of planar objects at multiple desired depths and attenuation of planar objects at multiple undesired depths, thereby achieving electronically tunable multi-depth focusing. Partial-separability and recursive nature of the proposed MDP and MDR transfer functions ensure ultra-low hardware complexity suitable for real-time processing of large volume of input samples encountered in 4-D LFs. Filter synthesis details and examples with synthetic and real LFs of size 15  ×  15 × 434  ×  625 are presented. A generic framework encapsulating a multitude of possible digital hardware realizations is described, employing J-unfolding and look-ahead pipelining albeit with modifications as applicable to the underlying multi-dimensional signal flow graphs to obtain increased real-time throughput. Proof-of-concept digital designs are provided for the 2-passband case of a MDP filter verifying a real-time throughput of  ≈ 490 LFs of size 9  ×  9 × 434  ×  625 per second for filters operating at 135 MHz on a Xilinx Virtex-7 FPGA device.
item: Article-Full-text
Multi-Volumetric refocusing of light fields
(IEEE, 2021) Jayaweera, SS; Edussooriya, CUS; Wijenayake, C; Agathoklis, P; Bruton, LT
Geometric information of scenes available with fourdimensional (4-D) light fields (LFs) paves the way for postcapture refocusing. Light field refocusing methods proposed so far have been limited to a single planar or a volumetric region of a scene. In this paper, we demonstrate simultaneous refocusing of multiple volumetric regions in LFs. To this end, we employ a 4-D sparse finite-extent impulse response (FIR) filter consisting of multiple hyperfan-shaped passbands. We design the 4-D sparse FIR filter as an optimal filter in the least-squares sense. Experimental results confirm that the proposed filter provides 63% average reduction in computational complexity with negligible degradation in the fidelity of multi-volumetric refocused LFs compared to a 4-D nonsparse FIR filter
item: Conference-Abstract
An Overview of multi-dimensional RF signal processing for array receivers
Madanayake, A; Wijenayake, C; Belostotski, L; Bruton, LT
In this review paper, recent advancements in multidimensional (MD) spatio-temporal signal processing for highlydirectional radio frequency (RF) antenna array based receivers are discussed. MD network-resonant beamforming filters having infinite impulse response (IIR) and recursive spatio-temporal signal flow graphs are reviewed. The concept of MD networkresonant pre-filtering is described as a modification to existing phased/timed array beamforming back-ends to achieve improved side-lobe performance in the array pattern, leading to better interference rejection capabilities. Both digital and analog signal processing models are described in terms of their system transfer functions and signal flow graphs. Example MD frequency response and RF antenna array pattern simulations are presented.
item: Conference-Full-text
An Overview of Multi-Dimensional RF Signal Processing for Array Receivers
(2015-08-03) Madanayake, A; Wijenayake, C; Belostotski, L; Bruton, Len T
In this review paper, recent advancements in multidimensional (MD) spatio-temporal signal processing for highlydirectional radio frequency (RF) antenna array based receivers are discussed. MD network-resonant beamforming filters having infinite impulse response (IIR) and recursive spatio-temporal signal flow graphs are reviewed. The concept of MD networkresonant pre-filtering is described as a modification to existing phased/timed array beamforming back-ends to achieve improved side-lobe performance in the array pattern, leading to better interference rejection capabilities. Both digital and analog signal processing models are described in terms of their system transfer functions and signal flow graphs. Example MD frequency response and RF antenna array pattern simulations are presented.
item: Conference-Abstract
Real-Time FPGA-Based multi-beam directional sensing of 2.4 GHz ISM RF sources
PulipatI, S; Ariyarathna, V; Edussooriya, CUS; Wijenayake, C; Wang, X; Madanayake, A
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-anddump 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. Preliminary experimental measurements obtained with Wi- Fi devices and the first energy detector verify the proof-of-concept directional sensing of the proposed system.
item: Article-Full-text
Real-time light field denoising using a novel linear 4-D hyperfan filter
(IEE, 2020) Premaratne, SU; Liyanage, N; Edussooriya, CUS; Wijenayake, C
Four-dimensional (4-D) light fields (LFs) enable novel imaging technologies, which are traditionally based on two-dimensional images. In most of these applications, denoising of LFs is required as a preprocessing technique before any subsequent processing. We propose a real-time LF denoising method using a novel 4-D linear and shift-invariant hyperfan filter. The proposed method exploits sparsity of the spectrum of a LF and the 4-D hyperfan filter is implemented in the 4-D mixed-domain (i.e.,two-dimensional space and two-dimensional frequency) leading to significant reductions in computational and memory complexities. A software implementation of the proposed method provides better or comparable denoising performance for grayscale and color LFs with respect to the metrics peak-signal-to-noise ratio (PSNR) and structural similarity (SSIM) compared to previously reported linear LF denoising methods, while reducing the processing time approximately by 66% and 31% for grayscale and color LFs, respectively. Furthermore, we propose a semi-systolic hardware architecture for the proposed denoising method, and implement on a field-programmable gate array (FPGA). The FPGA implementation implies a throughput of 25 LFs/s for LFs of size 11×11×625×434 and provides approximately 13 dB improvement in PSNR and 0.7 improvement in SSIM for grayscale LFs verifying the suitability for real-time processing.
item: Article-Full-text
Real-time light field signal processing using 4D/5D linear digital filter FPGA circuits
(IEEE, 2021) Edussooriya, CUS; Wijenayake, C; Madanayake, A; Liyanage, N; Premaratne, S; Vorhies, JT; Dansereau, DG; Agathoklis, P; Bruton, LT
Light fields (LFs) and light field videos (LFVs) capture both angular and spatial variation of light rays emanating from scenes. This richness of information leads to novel applications such as post-capture refocusing, depth estimation and depth-velocity filtering which are not possible with images and videos. These capabilities come, however, with a significant increase in data to be processed. In order to fully exploit opportunities provided by LFs and LFVs, low-complexity signal processing algorithms that process LF and LFV data in realtime are required. In this paper, we survey such state-of-theart algorithms, in particular for depth filtering, refocusing and denoising of LFs and depth-velcoty filtering for LFVs, and future directions for these real-time LF an LFV processing algorithms.