| 1. |
- Abrahamsson, Olle, et al.
(author)
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Opinion Dynamics with Random Actions and a Stubborn Agent
- 2019
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In: CONFERENCE RECORD OF THE 2019 FIFTY-THIRD ASILOMAR CONFERENCE ON SIGNALS, SYSTEMS & COMPUTERS. - : IEEE. - 9781728143002 ; , s. 1486-1490
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Conference paper (peer-reviewed)abstract
- We study opinion dynamics in a social network with stubborn agents who influence their neighbors but who themselves always stick to their initial opinion. We consider first the well-known DeGroot model. While it is known in the literature that this model can lead to consensus even in the presence of a stubborn agent, we show that the same result holds under weaker assumptions than has been previously reported. We then consider a recent extension of the DeGroot model in which the opinion of each agent is a random Bernoulli distributed variable, and by leveraging on the first result we establish that this model also leads to consensus, in the sense of convergence in probability, in the presence of a stubborn agent. Moreover, all agents opinions converge to that of the stubborn agent.
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| 2. |
- Abrahamsson, Olle, et al.
(author)
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Structural Balance Considerations for Networks with Preference Orders as Node Attributes
- 2022
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In: 2022 56TH ASILOMAR CONFERENCE ON SIGNALS, SYSTEMS, AND COMPUTERS. - : IEEE. - 9781665459068 - 9781665459075 ; , s. 1255-1261
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Conference paper (peer-reviewed)abstract
- We discuss possible definitions of structural balance conditions in a network with preference orderings as node attributes. The main result is that for the case with three alternatives (A, B, C) we reduce the (3!)(3) = 216 possible configurations of triangles to 10 equivalence classes, and use these as measures of balance of a triangle towards possible extensions of structural balance theory. Moreover, we derive a general formula for the number of equivalent classes for preferences on n alternatives. Finally, we analyze a real-world data set and compare its empirical distribution of triangle equivalence classes to a null hypothesis in which preferences are randomly assigned to the nodes.
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| 3. |
- Abrahamsson, R., et al.
(author)
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Elimination of leakage and ground-bounce effects in ground-penetrating radar data
- 2001
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In: Proceedings of the 11th IEEE Signal Processing Workshop on Statistical Signal Processing, 2001. - 0780370112 ; , s. 150-153
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Conference paper (peer-reviewed)abstract
- We address the problem of removing specular ground surface reflections and leakage/cross-talk from downward looking stepped frequency ground-penetrating radar (GPR) data. A new model for the ground-bounce and the leakage/cross-talk is introduced. An algorithm that jointly estimates these effects from collected data is presented. The algorithm has the sound foundation of a nonlinear least squares (LS) fit to the presented model. The minimization is performed in a cyclic manner where one step is a linear LS minimization and the other step is a non-linear LS minimization where the optimum can efficiently be found using, e.g., the chirp-transform algorithm. The results after applying the algorithm to measured GPR data, collected at a US army test range, are also shown
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| 4. |
- Akbar, Noman, et al.
(author)
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Downlink Power Control in Massive MIMO Networks with Distributed Antenna Arrays
- 2018
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In: 2018 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC). - : IEEE. - 9781538631805 - 9781538631812
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Conference paper (peer-reviewed)abstract
- In this paper, we investigate downlink power control in massive multiple-input multiple-output (MIMO) networks with distributed antenna arrays. The base station (BS) in each cell consists of multiple antenna arrays, which are deployed in arbitrary locations within the cell. Due to the spatial separation between antenna arrays, the large-scale propagation effect is different from a user to different antenna arrays in a cell, which makes power control a challenging problem as compared to conventional massive MIMO. We assume that the BS in each cell obtains the channel estimates via uplink pilots. Based on the channel estimates, the BSs perform maximum ratio transmission for the downlink. We then derive a closed-form spectral efficiency (SE) expression, where the channels are subject to correlated fading. Utilizing the derived expression, we propose a max-min power control algorithm to ensure that each user in the network receives a uniform quality of service. Numerical results demonstrate that, for the network considered in this work, optimizing for max-min SE through the max-min power control improves the sum SE of the network as compared to the equal power allocation.
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| 5. |
- Alty, Stephen R., et al.
(author)
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Efficient implementation of the time-recursive Capon and APES spectral estimators
- 2004
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In: EUSIPCO <em>2004</em>. - 3200001658 ; , s. 1269-1272
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Conference paper (peer-reviewed)abstract
- A method for the computationally efficient sliding window time-updating of the Capon and APES spectral estimators based on the time-variant displacement structure of the data covariance matrix is presented. The proposed algorithm forms a natural extension of the computationally most efficient algorithm to date, and offers a significant computationalgain as compared to the computational complexity associated with the batch re-evaluation of the spectral estimates for each time-update.
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| 6. |
- Aslam, Mohammed Zahid, et al.
(author)
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Large-scale Massive MIMO Network Evaluation Using Ray-based Deterministic Simulations
- 2018
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In: 2018 IEEE 29TH ANNUAL INTERNATIONAL SYMPOSIUM ON PERSONAL, INDOOR AND MOBILE RADIO COMMUNICATIONS (PIMRC). - : IEEE. - 9781538660096
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Conference paper (peer-reviewed)abstract
- Large-scale massive MIMO network deployments can provide higher spectral efficiency and better coverage for future communication systems like 5G. Due to the large number of antennas at the base station, the system achieves stable channel quality and spatially separable channels to the different users. In this paper, linear, planar, circular and cylindrical arrays are used in the evaluation of a large-scale multi-cell massive MIMO network. The system-level performance is predicted using two different kinds of channel models. First, a ray-based deterministic tool is utilized in a real North American city environment. Second, an independent and identically distributed (i.i.d.) Rayleigh fading channel model is considered, as often used in previously published massive MIMO studies. The analysis is conducted in a 16-macro-cell network with outdoor and randomly distributed users. It is shown that the array configuration has a large impact on the throughput statistics. Although the system level performance with i.i.d. Rayleigh fading can be close to the deterministic prediction in some situations (e.g., with large linear arrays), significant differences are noticed when considering other types of arrays.
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| 7. |
- Avazkonandeh Gharavol, Ebrahim, 1980-, et al.
(author)
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Robust Joint Optimization of MIMO Interfering Relay Channels with Imperfect CSI
- 2011
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In: 2001 4th IEEE International Workshop on Computational Advances in Multi-Sensor Adaptive Processing (CAMSAP). - Piscataway, NJ, USA : IEEE. - 9781457721045 ; , s. 209-212
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Conference paper (peer-reviewed)abstract
- In this paper we deal with the problem of the joint optimization of the precoders, equalizers and relay beamformer of a multiple-input multiple-output interfering relay channel. This network can be regarded az a generalized model for both one-way and two-way relay channels with/without direct interfering links. Unlike the conventional design procedures, we assume that the Channel State Information (CSI) is not known perfectly. The imperfect CSI is described using the norm bounded error framework. We use a system-wide Sum Mean Square Error (SMSE) based problem formulation which is constrained using the transmit power of the terminals and the relay node. The problem at hand, from a worst-case design perspective, is a multilinear, and hence, a nonconvex problem which is also semiinfinite in its constraints. We use a generalized version of the Peterson’s lemma to handle the semi-infiniteness and reduce the original problem to a single Linear Matrix Inequality (LMI). However, this LMI is not convex, and to resolve this issue we propose an iterative algorithm based on the alternating convex search methodology to solve the aforementioned problem. Finally simulation results, i.e., the convergence of the proposed algorithm and the SMSE properties, are included to asses the performance of the proposed algorithm.
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| 8. |
- Avazkonandeh Gharavol, Ebrahim, 1980-, et al.
(author)
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Robust Joint Optimization of Non-regenerative MIMO Relay Channels with Imperfect CSI
- 2011
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In: Conference Record of the Forty Fifth Asilomar Conference on Signals, Systems and Computers (ASILOMAR), 2011. - : IEEE Computer Society. - 9781467303217 ; , s. 1589-1593
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Conference paper (peer-reviewed)abstract
- In this paper, we deal with the problem of joint optimization of the source precoder, the relay beamformer and the destination equalizer in a nonregenerative relay network with only a partial knowledge of the Channel State Information (CSI).We model the partial CSI using a deterministic norm bounded error model, and we use a system-wide mean square error performance measure which is constrained based on the transmit power regulations for both source and relay nodes.Most conventional designs employ the average performance optimization, however, we solve this problem from a worst-case design perspective.The original problem formulation is a semi-infinite trilinear optimization problem which is not convex.To solve this problem we extend the existing theories to deal with the constraints which are semi-infinite in different independent complex matrix variables.We show that the equivalent approximate problem is a set of linear matrix inequalities, that can be solved iteratively.Finally simulation results assess the performance of the proposed scheme.
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| 9. |
- Axell, Erik, 1980-, et al.
(author)
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A Bayesian Approach to Spectrum Sensing, Denoising and Anomaly Detection
- 2009
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In: Proceedings of the 34th IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP'09). - 9781424423545 - 9781424423538 ; , s. 2333-2336
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Conference paper (peer-reviewed)abstract
- This paper deals with the problem of discriminating samples that contain only noise from samples that contain a signal embedded in noise. The focus is on the case when the variance of the noise is unknown. We derive the optimal soft decision detector using a Bayesian approach. The complexity of this optimal detector grows exponentially with the number of observations and as a remedy, we propose a number of approximations to it. The problem under study is a fundamental one and it has applications in signal denoising, anomaly detection, and spectrum sensing for cognitive radio. We illustrate the results in the context of the latter.
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| 10. |
- Axell, Erik, et al.
(author)
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A Unified Framework for GLRT-Based Spectrum Sensing of Signals with Covariance Matrices with Known Eigenvalue Multiplicities
- 2011
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In: Proceedings of the IEEE International Conference on Acoustics, Speech and SignalProcessing (ICASSP). - : IEEE conference proceedings. ; , s. 2956-2959
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Conference paper (peer-reviewed)abstract
- In this paper, we create a unified framework for spectrum sensing of signals which have covariance matrices with known eigenvalue multiplicities. We derive the generalized likelihood-ratio test (GLRT) for this problem, with arbitrary eigenvalue multiplicities under both hypotheses. We also show a number of applications to spectrum sensing for cognitive radio and show that the GLRT for these applications, of which some are already known, are special cases of the general result.
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