| 1. |
- Christopoulos, Dimitrios, et al.
(författare)
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Capacity Analysis of Multibeam Joint Decoding over Composite Satellite Channels
- 2011
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Ingår i: Proc. of the 45th Asilomar Conference on Signals, Systems and Computer. - : IEEE Signal Processing Society. - 1058-6393. - 9781467303231
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Konferensbidrag (refereegranskat)abstract
- The throughput of current multibeam satellite systemsis limited by self interference. Interference mitigationtechniques have the potential to significantly increase the spectralefficiency of these satellite communication systems. The presentcontribution investigates the ergodic capacity of the return linkof a multibeam satellite system, where full frequency reuse is employedand user signals are jointly processed at the gateway. Theproposed model incorporates correlated satellite antennas overRician channels which represent some inherent characteristics ofsatellite communications. Additionally, the effects of shadowingcaused by user mobility, are modeled via the lognormal distribution.Hence, a composite Rician/lognormal fading channel withfully correlated receive antennas is considered. For this channel, anew lower bound on the ergodic capacity is analytically deducedand verified through simulations.
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| 2. |
- Abu-Shaban, Z., et al.
(författare)
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Enhanced List-based Group-wise overloaded receiver with application to satellite reception
- 2014
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Ingår i: 2014 IEEE International Conference on Communications (ICC). - : IEEE conference proceedings. ; , s. 5616-5621
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Konferensbidrag (refereegranskat)abstract
- The market trends towards the use of smaller dish antennas for TV satellite receivers, as well as the growing density of broadcasting satellites in orbit require the application of robust adjacent satellite interference (ASI) cancellation algorithms at the receivers. The wider beamwidth of a small size dish and the growing number of satellites in orbit impose an overloaded scenario, i.e., a scenario where the number of transmitting satellites exceeds the number of receiving antennas. For such a scenario, we present a two stage receiver to enhance signal detection from the satellite of interest, i.e., the satellite that the dish is pointing to, while reducing interference from neighboring satellites. Towards this objective, we propose an enhanced List-based Group-wise Search Detection (LGSD) receiver architecture that takes into account the spatially correlated additive noise and uses the signal-to-interference-plus-noise ratio (SINR) maximization criterion to improve detection performance. Simulations show that the proposed receiver structure enhances the performance of satellite systems in the presence of ASI when compared to existing methods.
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| 3. |
- Abu-Shaban, Z., et al.
(författare)
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Overloaded satellite receiver using SIC with hybrid beamforming and ML detection
- 2013
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Ingår i: 2013 IEEE 14th Workshop on Signal Processing Advances in Wireless Communications (SPAWC). - New York : IEEE. - 9781467355773 ; , s. 450-454
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Konferensbidrag (refereegranskat)abstract
- In this paper, a new receiver structure that is intended to detect the signals from multiple adjacent satellites in the presence of other interfering satellites is proposed. We tackle the worst case interference conditions, i.e., it is assumed that uncoded signals that fully overlap in frequency arrive at a multiple-element small-size parabolic antenna in a spatially correlated noise environment. The proposed successive interference cancellation (SIC) receiver, denoted by SIC Hy/ML, employs hybrid beamforming and disjoint maximum likelihood (ML) detection. Depending on the individual signals spatial position, the proposed SIC Hy/ML scheme takes advantage of two types of beamformers: a maximum ratio combining (MRC) beamformer and a compromised array response (CAR) beamformer. The performance of the proposed receiver is compared to an SIC receiver that uses only MRC beamforming scheme with ML detection for all signals, a joint ML detector, and a minimum mean square error detector. It is found that SIC Hy/ML outperforms the other schemes by a large margin.
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| 4. |
- Afzal, H., et al.
(författare)
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RGB-D multi-view system calibration for full 3D scene reconstruction
- 2014
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Ingår i: 2014 22nd International Conference on Pattern Recognition. - : IEEE conference proceedings. ; , s. 2459-2464
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Konferensbidrag (refereegranskat)abstract
- One of the most crucial requirements for building a multi-view system is the estimation of relative poses of all cameras. An approach tailored for a RGB-D cameras based multi-view system is missing. We propose BAICP+ which combines Bundle Adjustment (BA) and Iterative Closest Point (ICP) algorithms to take into account both 2D visual and 3D shape information in one minimization formulation to estimate relative pose parameters of each camera. BAICP+ is generic enough to take different types of visual features into account and can be easily adapted to varying quality of 2D and 3D data. We perform experiments on real and simulated data. Results show that with the right weighting factor BAICP+ has an optimal performance when compared to BA and ICP used independently or sequentially.
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| 5. |
- Al Ismaeil, Kassem, et al.
(författare)
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Bilateral Filter Evaluation Based on Exponential Kernels
- 2012
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Konferensbidrag (refereegranskat)abstract
- The well-known bilateral filter is used to smooth noisy images while keeping their edges. This filter is commonly used with Gaussian kernel functions without real justification. The choice of the kernel functions has a major effect on the filter behavior. We propose to use exponential kernels with L1 distances instead of Gaussian ones. We derive Stein's Unbiased Risk Estimate to find the optimal parameters of the new filter and compare its performance with the conventional one. We show that this new choice of the kernels has a comparable smoothing effect but with sharper edges due to the faster, smoothly decaying kernels.
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| 6. |
- Al Ismaeil, K., et al.
(författare)
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Depth super-resolution by enhanced shift and add
- 2013
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Ingår i: Computer Analysis of Images and Patterns. - Berlin, Heidelberg : Springer. - 9783642402456 ; , s. 100-107
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Konferensbidrag (refereegranskat)abstract
- We use multi-frame super-resolution, specifically, Shift & Add, to increase the resolution of depth data. In order to be able to deploy such a framework in practice, without requiring a very high number of observed low resolution frames, we improve the initial estimation of the high resolution frame. To that end, we propose a new data model that leads to a median estimation from densely upsampled low resolution frames. We show that this new formulation solves the problem of undefined pixels and further allows to improve the performance of pyramidal motion estimation in the context of super-resolution without additional computational cost. As a consequence, it increases the motion diversity within a small number of observed frames, making the enhancement of depth data more practical. Quantitative experiments run on the Middlebury dataset show that our method outperforms state-of-the-art techniques in terms of accuracy and robustness to the number of frames and to the noise level.
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| 7. |
- Al Ismaeil, K., et al.
(författare)
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Dynamic super resolution of depth sequences with non-rigid motions
- 2013
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Ingår i: 2013 IEEE International Conference on Image Processing, ICIP 2013 - Proceedings. - : IEEE Signal Processing Society. - 9781479923410 ; , s. 660-664
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Konferensbidrag (refereegranskat)abstract
- We enhance the resolution of depth videos acquired with low resolution time-of-flight cameras. To that end, we propose a new dedicated dynamic super-resolution that is capable to accurately super-resolve a depth sequence containing one or multiple moving objects without strong constraints on their shape or motion, thus clearly outperforming any existing super-resolution techniques that perform poorly on depth data and are either restricted to global motions or not precise because of an implicit estimation of motion. The proposed approach is based on a new data model that leads to a robust registration of all depth frames after a dense upsampling. The textureless nature of depth images allows to robustly handle sequences with multiple moving objects as confirmed by our experiments.
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| 8. |
- Al Ismaeil, K., et al.
(författare)
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Multi-frame super-resolution by enhanced shift & add
- 2013
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Ingår i: 2013 8th International Symposium on Image and Signal Processing and Analysis (ISPA). - : IEEE. - 9789531841948 ; , s. 171-176
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Konferensbidrag (refereegranskat)abstract
- A critical step in multi-frame super-resolution is the registration of frames based on their motion. We improve the performance of current state-of-the-art super-resolution techniques by proposing a more robust and accurate registration as early as in the initialization stage of the high resolution estimate. Indeed, we solve the limitations on scale and motion inherent to the classical Shift & Add approach by upsampling the low resolution frames up to the super-resolution factor prior to estimating motion or to median filtering. This is followed by an appropriate selective optimization, leading to an enhanced Shift & Add. Quantitative and qualitative evaluations have been conducted at two levels; the initial estimation and the final optimized superresolution. Results show that the proposed algorithm outperforms existing state-of-art methods.
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| 9. |
- Alodeh, M., et al.
(författare)
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A multicast approach for constructive interference precoding in MISO downlink channel
- 2014
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Ingår i: 2014 IEEE International Symposium on Information Theory. - : IEEE conference proceedings. ; , s. 2534-2538
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Konferensbidrag (refereegranskat)abstract
- This paper studies the concept of jointly utilizing the data information (DI) and channel state information (CSI) in order to design symbol-level precoders for a multiple input and single output (MISO) downlink channel. In this direction, the interference among the simultaneous data streams is transformed to useful signal that can improve the signal to interference noise ratio (SINR) of the downlink transmissions. We propose a maximum ratio transmissions (MRT) based algorithm that jointly exploits DI and CSI to gain the benefits from these useful signals. In this context, a novel framework to minimize the power consumption is proposed by formalizing the duality between the constructive interference downlink channel and the multicast channels. The numerical results have shown that the proposed schemes outperform other state of the art techniques.
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| 10. |
- Alodeh, M., et al.
(författare)
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Joint channel estimation and pilot allocation in underlay cognitive MISO networks
- 2014
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Ingår i: 2014 International Wireless Communications and Mobile Computing Conference (IWCMC). - : IEEE conference proceedings. ; , s. 797-802
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Konferensbidrag (refereegranskat)abstract
- Cognitive radios have been proposed as agile technologies to boost the spectrum utilization. This paper tackles the problem of channel estimation and its impact on downlink transmissions in an underlay cognitive radio scenario. We consider primary and cognitive base stations, each equipped with multiple antennas and serving multiple users. Primary networks often suffer from the cognitive interference, which can be mitigated by deploying beamforming at the cognitive systems to spatially direct the transmissions away from the primary receivers. The accuracy of the estimated channel state information (CSI) plays an important role in designing accurate beamformers that can regulate the amount of interference. However, channel estimate is affected by interference. Therefore, we propose different channel estimation and pilot allocation techniques to deal with the channel estimation at the cognitive systems, and to reduce the impact of contamination at the primary and cognitive systems. In an effort to tackle the contamination problem in primary and cognitive systems, we exploit the information embedded in the covariance matrices to successfully separate the channel estimate from other users' channels in correlated cognitive single input multiple input (SIMO) channels. A minimum mean square error (MMSE) framework is proposed by utilizing the second order statistics to separate the overlapping spatial paths that create the interference. We validate our algorithms by simulation and compare them to the state of the art techniques.
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