| 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. |
- Björnson, Emil, et al.
(författare)
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Capacity Limits and Multiplexing Gains of MIMO Channels with Transceiver Impairments
- 2013
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Ingår i: IEEE Communications Letters. - : IEEE Communications Society. - 1089-7798 .- 1558-2558. ; 17:1, s. 91-94
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Tidskriftsartikel (refereegranskat)abstract
- The capacity of ideal MIMO channels has a high-SNR slope that equals the minimum of the number of transmit and receive antennas. This letter analyzes if this result holds when there are distortions from physical transceiver impairments. We prove analytically that such physical MIMO channels have a finite upper capacity limit, for any channel distribution and SNR. The high-SNR slope thus collapses to zero. This appears discouraging, but we prove the encouraging result that the relative capacity gain of employing MIMO is at least as large as with ideal transceivers.
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| 3. |
- Björnson, Emil, 1983-, et al.
(författare)
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Impact of Spatial Correlation and Precoding Design in OSTBC MIMO Systems
- 2010
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Ingår i: IEEE Transactions on Wireless Communications. - : IEEE. - 1536-1276 .- 1558-2248. ; 9:11, s. 3578-3589
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Tidskriftsartikel (refereegranskat)abstract
- The impact of transmission design and spatial correlation on the symbol error rate (SER) is analyzed for multi-antenna communication links. The receiver has perfect channel state information (CSI), while the transmitter has either statistical or no CSI. The transmission is based on orthogonal space-time block codes (OSTBCs) and linear precoding. The precoding strategy that minimizes the worst-case SER is derived for the case when the transmitter has no CSI. Based on this strategy, the intuitive result that spatial correlation degrades the SER performance is proved mathematically. In the case when the transmitter knows the channel statistics, the correlation matrix is assumed to be jointly-correlated (a generalization of the Kronecker model). The eigenvectors of the SER-optimal precoding matrix are shown to originate from the correlation matrix and the remaining power allocation is a convex problem. Equal power allocation is SER-optimal at high SNR. Beamforming is SER-optimal at low SNR, or for increasing constellation sizes, and its optimality range is characterized. A heuristic low-complexity power allocation is proposed and evaluated numerically. Finally, it is proved analytically that receive-side correlation always degrades the SER. Transmit-side correlation will however improve the SER at low to medium SNR, while its impact is negligible at high SNR.
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| 4. |
- Gershman, Alex B., et al.
(författare)
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Convex Optimization-Based Beamforming : From Receive to Transmit and Network Designs
- 2010
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Ingår i: IEEE signal processing magazine (Print). - : IEEE. - 1053-5888 .- 1558-0792. ; 27:3, s. 62-75
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Tidskriftsartikel (refereegranskat)abstract
- In this article, an overview of advanced convex optimization approaches to-multisensor beamforming is presented, and connections are drawn between different types of optimization-based beamformers that apply to a broad class of receive, transmit, and network beamformer design problems. It is demonstrated that convex optimization provides an indispensable set of tools for beamforming, enabling rigorous formulation and effective solution of both long-standing and emerging design problems.
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| 5. |
- Grotz, Joel, et al.
(författare)
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Signal Detection and Synchronization for Interference Overloaded Satellite Broadcast Reception
- 2010
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Ingår i: IEEE Transactions on Wireless Communications. - : IEEE. - 1536-1276 .- 1558-2248. ; 9:10, s. 3052-3063
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Tidskriftsartikel (refereegranskat)abstract
- We address fixed satellite broadcast reception with the goal of decreasing the aperture of the receiving antenna. The front-end antenna size is commonly determined by the presence of interference from adjacent satellites. A small antenna aperture leads to interference from neighboring satellites utilizing the same frequency bands. We propose a reception system with. M multiple input elements and with subsequent joint detection of desired and interfering signals that provides reliable communication in the presence of multiple interfering signals. An iterative least squares technique is adopted combining spatial and temporal processing and achieving robustness against pointing errors. Simulation results show how the proposed joint spatial and temporal adapted mechanism outperforms the simple combination of existing techniques under interference overloaded conditions. Also, we demonstrate how to accurately synchronize the signals as part of the detection procedure. The technique is evaluated in a realistic simulation study representing the conditions encountered in a DVB-S2 broadcast scenario.
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| 6. |
- Tran, Le-Nam, et al.
(författare)
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Iterative Precoder Design and User Scheduling for Block-Diagonalized Systems
- 2012
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Ingår i: IEEE Transactions on Signal Processing. - : IEEE Signal Processing Society. - 1053-587X. ; 60:7, s. 3726-3739
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Tidskriftsartikel (refereegranskat)abstract
- The block diagonalization (BD) scheme is a low-complexity suboptimal precoding technique for multiuser MIMO downlink channels, which completely precancels the multiuser interference. Accordingly, the precoder of each user lies in the null space of other users channel matrices. In this paper, we propose an iterative algorithm using QR decompositions (QRDs) to compute the precoders. Specifically, to avoid dealing with a large concatenated matrix, we apply the QRD to a sequence of matrices of lower dimensions. One problem of BD schemes is that the number of users that can be simultaneously supported is limited due to zero interference constraints. When the number of users is large, a set of users must be selected, and selection algorithms should be designed to exploit the multiuser diversity gain. Finding the optimal set of users requires an exhaustive search, which has too high computational complexity to be practically useful. Based on the iterative precoder design, this paper proposes a low-complexity user selection algorithm using a greedy method, in which the precoders of selected users are recursively updated after each selection step. The selection metric of the proposed scheduling algorithm relies on the product of the squared row norms of the effective channel matrices, which is related to the eigenvalues by the Hadamard and Schur inequalities. An asymptotic analysis is provided to show that the proposed algorithm can achieve the optimal sum rate scaling of the MIMO broadcast channel. The numerical results show that the proposed algorithm achieves a good trade-off between sum rate performance and computational complexity.When users suffer different channel conditions, providing fairness among users is of critical importance. To address this problem, we also propose two fair scheduling (FS) algorithms, one imposing fairness in the approximation of the data rate, and another directly imposing fairness in the product of the squared row norms of the effective cha- nel matrices.
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| 7. |
- Wang, Jiaheng, et al.
(författare)
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Robust maximin MIMO precoding for arbitrary convex uncertainty sets
- 2012
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Ingår i: Acoustics, Speech and Signal Processing (ICASSP), 2012 IEEE International Conference on. - : IEEE. - 9781467300469 ; , s. 3045-3048
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Konferensbidrag (refereegranskat)abstract
- We consider a worst-case robust precoding design for multi-input multi-output (MIMO) communication systems with imperfect channel state information at the transmitter (CSIT). Instead of a particular choice, we consider a general imperfect CSIT model that only assumes the channel errors to be within a convex set, which includes most common imperfect CSIT models as special cases. The robust precoding design is formulated as a maximin problem, aiming at maximizing the worst-case received signal-to-noise ratio or minimizing the worst-case error probability. It is shown that the robust precoder can be easily obtained by solving a convex problem. We further provide an equivalent but more practical form of the convex problem that can be efficiently handled with common optimization methods and software packages.
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| 8. |
- 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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| 9. |
- 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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| 10. |
- 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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