| 1. |
- Viberg, Mats, 1961, et al.
(författare)
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Maximum Likelihood Array Processing in Spatially Correlated Noise Fields Using Parameterized Signals
- 1997
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Ingår i: IEEE Transactions on Signal Processing. - : Institute of Electrical and Electronics Engineers (IEEE). - 1941-0476 .- 1053-587X. ; 45, s. 996-1004
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Tidskriftsartikel (refereegranskat)abstract
- This paper deals with the problem of estimating signal parameters using an array of sensors. This problem is of interest in a variety of applications, such as radar and sonar source localization. A vast number of estimation techniques have been proposed in the literature during the past two decades. Most of these can deliver consistent estimates only if the covariance matrix of the background noise is known. In many applications, the aforementioned assumption is unrealistic. Recently, a number of contributions have addressed the problem of signal parameter estimation in unknown noise environments based on various assumptions on the noise. Herein, a different approach is taken. We assume instead that the signals are partially known. The received signals are modeled as linear combinations of certain known basis functions. The exact maximum likelihood (ML) estimator for the problem at hand is derived, as well as a computationally more attractive approximation. The Cramer Rao lower bound (CRB) on the estimation error variance is also derived and found to coincide with the CRB, assuming an arbitrary deterministic model and known noise covariance.
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| 2. |
- Zhang, Xi, et al.
(författare)
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Power Allocation and Bit Loading for Spatial Multiplexing in MIMO Systems
- 2003
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Ingår i: Proceedings IEEE International Conference on Acoustics, Speech, and Signal Processing. - NEW YORK : IEEE. ; , s. 53-56, s. 53-56
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Konferensbidrag (refereegranskat)abstract
- The power assignment problem is important for Multiple-Input-Multiple-Output (MIMO) systems to achieve high capacity. Although this problem is solved by well-known water filling algorithms, this does not provide an optimal solution if the system is constrained to a fixed raw bit error rate threshold and to discrete modulation orders. In this work an approximate approach, called QoS based WF, is proposed to solve the power assignment problem with such constrains. It is shown to outperform quantization of the conventional water filling solution and a well known bit loading algorithm (Chow’s algorithm) used in the Digital Subscriber Lines (DSL).
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| 3. |
- 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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| 4. |
- Martin, Cristoff, et al.
(författare)
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Approximate Transmit Covariance Optimization of MIMO Systems with Covariance Feedback
- 2003
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Ingår i: Proceedings Asilomar Conference on Signals, Systems & Computers. - : IEEE. ; , s. 1047-1051
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Konferensbidrag (refereegranskat)abstract
- The data rate of a multiple input, multiple output (MIMO) communication link can be improved if knowledge about the channel statistics is exploited at the transmitter. However, many realistic system scenarios require computationally prohibitive Monte Carlo methods in order to optimize the transmit covariance for maximization of the exact mutual information. This paper instead considers an approximative approach to maximize the performance of a communication link where covariance feedback is available at the transmitter. The algorithm presented is based on an asymptotic expression of the mutual information that allows for correlation at both the transmit and the receive side of the system. From simulations we demonstrate significant gain over beamforming and pure divversity schemes in many realistic system scenarios.
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| 5. |
- You, Lei, et al.
(författare)
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Power and Load Optimization in Interference-Coupled Non-Orthogonal Multiple Access Networks
- 2018
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Ingår i: 2018 IEEE Global Communications Conference (GLOBECOM). - : IEEE. - 9781538647271
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Konferensbidrag (refereegranskat)abstract
- Towards energy savings in large-scale non-orthogonal multiple access (NOMA) networks, we investigate power and load optimization for multi-cell and multi-carrier NOMA systems in this paper. To capture the coupling relation of mutual interference among cells, firstly, we extend a load-coupling model from orthogonal multiple access (OMA) to NOMA networks. Next, with this analytical tool, we formulate the considered optimization problem in NOMA-based load-coupled systems, where optimizing load, power, and determining decoding order are the key aspects in the optimization. Theoretically, we prove that the minimum network energy consumption can be achieved by using all the time-frequency resources in each cell to deliver users' demand. To achieve the optimal load and enable efficient power optimization, we develop a power-adjustment algorithm. Numerical results demonstrate promising energy-saving gains of NOMA over OMA in large-scale cellular networks, in particular for the high-demand and resource-limited scenarios.
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| 6. |
- Garcia, Frederic, et al.
(författare)
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A new 1-D colour model and its application to image filtering
- 2011
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Ingår i: ISPA 2011 - 7th International Symposium on Image and Signal Processing and Analysis. ; , s. 134-138
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Konferensbidrag (refereegranskat)abstract
- This paper introduces a new 1-D model to encodecoloured images for an efficient subsequent processing. Thisrepresentation is equivalent to, but more compact than, the 3-DHCL conical representation. It consists in gathering all the hue,chroma and luminance information in one component, namely,the cumulative spiral angle, where the spirals in question aredefined as a sampling of the solid HCL cone. We use theproposed model for joint bilateral upsampling of low-resolutiondepth maps. The results show that, in addition to preserving theperceptual properties of the HCL colour representation, usingthe proposed model leads to a solution that is more accuratethan when using grayscale images.
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| 7. |
- Huang, Yongming, et al.
(författare)
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Distributed Multicell Beamforming With Limited Intercell Coordination
- 2011
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Ingår i: IEEE Transactions on Signal Processing. - 1053-587X .- 1941-0476. ; 59:2, s. 728-738
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Tidskriftsartikel (refereegranskat)abstract
- This paper studies distributed optimization schemes for multicell joint beamforming and power allocation in time-division-duplex (TDD) multicell downlink systems where only limited-capacity intercell information exchange is permitted. With an aim to maximize the worst-user signal-to-interference-and-noise ratio (SINR), we devise a hierarchical iterative algorithm to optimize downlink beamforming and intercell power allocation jointly in a distributed manner. The proposed scheme is proved to converge to the global optimum. For fast convergence and to reduce the burden of intercell parameter exchange, we further propose to exploit previous iterations adaptively. Results illustrate that the proposed scheme can achieve near-optimal performance even with a few iterations, hence providing a good tradeoff between performance and backhaul consumption. The performance under quantized parameter exchange is also examined.
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| 8. |
- von Wrycza, Peter, 1981-, et al.
(författare)
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Spectrum Allocation from a Game Theoretic Perspective : Properties of Nash Equilibria
- 2008
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Ingår i: 2008 42ND ASILOMAR CONFERENCE ON SIGNALS, SYSTEMS AND COMPUTERS, VOLS 1-4. - New York : IEEE. - 9781424429400 ; , s. 1542-1546
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Konferensbidrag (refereegranskat)abstract
- We consider a scenario consisting of two transmit-receive pairs coexisting in the same area and communicating using the same portion of the spectrum. Applying a game theoretic framework, each pair is regarded as a player whose payoff function is the individual link rate and power is allocated using the iterative water-filling algorithm. We study the dynamics of such a game and find properties of the resulting Nash equilibria. For high interference scenarios, operating points admitting complete, partial or no overlap are possible and we present conditions under which the different Nash equilibria are achievable. Based on this analysis, a modified water-filling algorithm is designed to increase the sum-rate of the communication links. Its performance is compared to that of the iterative water-filling algorithm by numerical simulations. Although we restrict the analysis to a two player game, analogous concepts can be used to design decentralized algorithms for scenarios with more players.
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| 9. |
- Alodeh, M., et al.
(författare)
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Symbol-level and multicast precoding for multiuser multiantenna downlink : A state-of-the-art, classification, and challenges
- 2018
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Ingår i: IEEE Communications Surveys and Tutorials. - : Institute of Electrical and Electronics Engineers (IEEE). - 1553-877X. ; 20:3, s. 1733-1757
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Tidskriftsartikel (refereegranskat)abstract
- Precoding has been conventionally considered as an effective means of mitigating or exploiting the interference in the multiantenna downlink channel, where multiple users are simultaneously served with independent information over the same channel resources. The early works in this area were focused on transmitting an individual information stream to each user by constructing weighted linear combinations of symbol blocks (codewords). However, more recent works have moved beyond this traditional view by: 1) transmitting distinct data streams to groups of users and 2) applying precoding on a symbol-per-symbol basis. In this context, the current survey presents a unified view and classification of precoding techniques with respect to two main axes: 1) the switching rate of the precoding weights, leading to the classes of block-level and symbol-level precoding and 2) the number of users that each stream is addressed to, hence unicast, multicast, and broadcast precoding. Furthermore, the classified techniques are compared through representative numerical results to demonstrate their relative performance and uncover fundamental insights. Finally, a list of open theoretical problems and practical challenges are presented to inspire further research in this area1.1The concepts of precoding and beamforming are used interchangeably throughout this paper.
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| 10. |
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