| 1. |
- Kaiser, Thomas, et al.
(författare)
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When will smart antennas be ready for the market? : Part II - results
- 2005
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Ingår i: IEEE signal processing magazine (Print). - 1053-5888. ; 22:6, s. 174-176
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Tidskriftsartikel (övrigt vetenskapligt)abstract
- The aim of this two-part forum is to shed more light on the future of smartantennas (SA) through discussions among a balanced group of experts from academia and industry. In part I, which appeared in the March 2005 issue of IEEE Signal Processing Magazine, each of the experts stated his own opinion after exchanging some thoughts by e-mail. Then, a panel session took place at ICAS-SP'05 and a public poll followed. Now, in part II, the results are summarized by the experts. The central topic of the forum was the expectedmarket breakthrough of SA.
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| 2. |
- Kristensson, Martin, et al.
(författare)
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Further Results and Insights on Subspace Based Sinusoidal Frequency Estimation
- 2001
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Ingår i: IEEE Transactions on Signal Processing. - IEEE Signal Processing Society. - 1053-587X. ; 49:12, s. 2962-2974
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Tidskriftsartikel (refereegranskat)abstract
- Subspace-based methods for parameter identification have received considerable attention in the literature. Starting with a scalar-valued process, it is well known that subspace-based identification of sinusoidal frequencies is possible if the scalar valued data is windowed to form a low-rank vector-valued process. MUSIC and ESPRIT-like estimators have, for some time, been applied to this vector model. In addition, a statistically attractive Markov-like procedure for this class of methods has been proposed. Herein, the Markov-like procedure is reinvestigated. Several results regarding rank, performance, and structure are given in a compact manner. The large sample equivalence with the approximate maximum likelihood method by Stoica et al. (1988) is also established
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| 3. |
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| 4. |
- Parkvall, Stefan, et al.
(författare)
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Asynchronous near-far resistant DS-CDMA receivers without a priori synchronization
- 1999
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Ingår i: IEEE Transactions on Communications. - 0090-6778. ; 47:1, s. 78-88
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, several receivers for data demodulation in an asynchronous direct-sequence code-division multiple access (DS-CDMA) system operating without prior knowledge of the propagation delays are proposed and compared. Special attention is paid to the near-far problem, and the proposed schemes are numerically shown to he near-far resistant, The near-far resistance is obtained by estimating the a priori unknown propagation delay using a subspace-based technique. Quantities obtained in the estimation procedure are used to design a filter used for suppression of interference, according to the minimum mean square error criterion. Either a decision feedback technique or a simple two-state Viterbi algorithm is subsequently used for the data demodulation in the uncoded case, By extending the trellis used in the Viterbi algorithm, error correcting coding is easily implemented.
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| 5. |
- Parkvall, Stefan, et al.
(författare)
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Sensitivity Analysis of Linear DS-CDMA Detectors to Propagation Delay Estimation Errors
- 1995
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Ingår i: Proceedings IEEE Global Telecommunications Conference. ; s. 1872-1876
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Konferensbidrag (refereegranskat)abstract
- An asynchronous direct-sequence code division multiple access (DS-CDMA) communication system operating over an additive white Gaussian noise (AWGN) channel is considered. In many applications, the near-far problem can be the limiting factor. Several near-far resistant receivers have therefore been proposed (e.g., the decorrelating receiver). These receivers assume perfect knowledge of the propagation delay from all users to the receiver. In practice, the delays are estimated and therefore subject to estimation errors. The performance penalty these errors impose on linear detectors, especially the decorrelating detector, is evaluated
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| 6. |
- Stoica, Petre, et al.
(författare)
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Comments on "Min-Norm interpretations and consistency of MUSIC, MODE, and ML"
- 1998
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Ingår i: IEEE Transactions on Signal Processing. - 1053-587X. ; 46:8, s. 2262-2263
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Tidskriftsartikel (refereegranskat)abstract
- The results and interpretations obtained in the above referred paper are shown to be well known or obvious. Additionally, corrections to some misleading statements in the aforementioned paper are presented.
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| 7. |
- Stoica, P, et al.
(författare)
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The evil of superefficiency
- 1996
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Ingår i: Signal Processing. - 0165-1684. ; 55:1, s. 133-136
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Tidskriftsartikel (refereegranskat)abstract
- We discuss the intriguing notion of statistical superefficiency in a straightforward manner with a minimum of formality. We point out that for any given parameter estimator there exist other estimators which have a strictly lower asymptotic variance and hence are statistically more efficient than the former. In particular, if the former estimator was statistically efficient (in the sense that its asymptotic variance was equal to the Cramer-Rao bound) then the latter estimators could be called ''superefficient''. Among others, the phenomenon of superefficiency implies that asymptotically there exists no uniformly minimum-variance parameter estimator.
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| 8. |
- Ström, Erik G, et al.
(författare)
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DS-CDMA synchronization in time-varying fading channels
- 1996
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Ingår i: IEEE Journal on Selected Areas in Communications. - 0733-8716. ; 14:8, s. 1636-1642
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Tidskriftsartikel (refereegranskat)abstract
- Herein, the problem of estimating propagation delays of the transmitted signals in a direct-sequence code-division multiple access (DS-CDMA) system operating over fading channels is considered. Even though this study is limited to the case when the propagation delays are fixed during the observation interval, the channel gain and phase are allowed to vary in time. Special attention is given to the near-far problem which is catastrophic for the standard acquisition algorithm. An estimator based on subspace identification techniques is proposed, and the Cramer-Rao bound, which serves as an optimality criterion, is derived. The Cramer-Rao bound is shown to be independent of the near-far problem, which implies that there is no fundamental reason for propagation delay estimators to be near-far limited. Furthermore, the proposed algorithm is experimentally shown to be robust against the near-far problem.
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| 9. |
- Ström, Erik G, et al.
(författare)
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Propagation delay estimation in asynchronous direct-sequence code-division multiple access systems
- 1996
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Ingår i: IEEE Transactions on Communications. - 0090-6778. ; 44:1, s. 84-93
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Tidskriftsartikel (refereegranskat)abstract
- In an asynchronous direct-sequence code-division multiple access CDS-CDMA) communication system, the parameter estimation problem, i.e., estimating the propagation delay, attenuation and phase shift of each user's transmitted signal, may be complicated by the so-called near-far problem. The near-far problem occurs when the amplitudes of the users' received signals are very dissimilar, as the case might be in many important applications, In particular, the standard method for estimating the propagation delays will fail in a near-far situation, Several new estimators, the maximum likelihood, an approximative maximum likelihood and a subspace-based estimator, are therefore proposed and are shown to be robust against the near-far problem, No knowledge of the transmitted bits is assumed, and the proposed estimators can thus be used for both acquisition and tracking. In addition, the Cramer-Rao bound is derived for the parameter estimation problem.
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| 10. |
- Tran, Le-Nam, et al.
(författare)
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Successive zero-forcing DPC with per-antenna power constraint : Optimal and suboptimal designs
- 2012
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Ingår i: Communications (ICC), 2012 IEEE International Conference on. - IEEE. - 978-145772052-9 ; s. 3746-3751
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Konferensbidrag (refereegranskat)abstract
- This paper considers the precoder designs for successive zero-forcing dirty paper coding (SZF-DPC), a suboptimal transmission technique for MIMO broadcast channels (MIMO BCs). Existing precoder designs for SZF-DPC often consider a sum power constraint. In this paper, we address the precoder design for SZF-DPC with per-antenna power constraints (PAPCs), which has not been well studied. First, we formulate the precoder design as a rank-constrained optimization problem, which is generally difficult to handle. To solve this problem, we follow a relaxation approach, and prove that the optimal solution of the relaxed problem is also optimal for the original problem. Considering the relaxed problem, we propose a numerically efficient algorithm to find the optimal solution, which exhibits a fast convergence rate. Suboptimal precoder designs, with lower computational complexity, are also presented, and compared with the optimal ones in terms of achievable sum rate and computational complexity.
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