| 1. |
- Gustafsson, Oscar, 1973-, et al.
(author)
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Comparison of graphical and sub-expression elimination methods for design of efficient multipliers
- 2004
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In: Conference Record of the Thirty-Eighth Asilomar Conference on Signals, Systems and Computers, 2004, Volume 1. - : IEEE. - 0780386221 ; , s. 72-76
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Conference paper (other academic/artistic)abstract
- Relationships are examined between two traditional strategies used to design "multiplier blocks": graphical methods and common subexpression elimination (CSE), four applications: single multipliers, multiplier blocks (several products of a single multiplicand), FIR filters and matrix multipliers are compared. A new representation shows how graphical designs can be extracted from CSE designs. Algorithms for both approaches are compared. A new graphical algorithm for FIR filter design and new results for CSE in the multiple product case are presented so comparison can be made for all applications. We conclude that for simpler problems, graphical methods are best, while CSE works better for the more complex problems
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| 2. |
- Gustafsson, Oscar, et al.
(author)
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Improved multiple constant multiplication using minimum spanning trees
- 2004
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In: Conference Record of the Thirty-Eighth Asilomar Conference on Signals, Systems and Computers, 2004, Volume 1. - : IEEE. - 0780386221 ; , s. 63-66
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Conference paper (other academic/artistic)abstract
- Recently, a novel technique for the multiple constant multiplication (MCM) problem using minimum spanning trees (MSTs) has been proposed. The approach works by finding simple differences between the coefficients to realize and then applying the same method to the differences (which is an MCM problem as well). Each iteration is divided into two steps. First, finding a minimum spanning tree in the graph describing the differences between the coefficients. Second, as each edge in the graph may correspond to more than one difference, one difference is selected for each edge in the MST. Generally, both these stages have multiple solutions. The aim of this work is to more closely study how the MST and the differences should be selected to give better total results. It is also discussed how the two stages in each iteration may be joined into one problem.
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| 3. |
- Hu, Bin, et al.
(author)
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Iterative joint channel estimation and successive interference cancellation using a SISO-SAGE algorithm for coded CDMA
- 2004
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In: ASILOMAR CONFERENCE ON SIGNALS, SYSTEMS & COMPUTERS. - 0780386221 ; , s. 622-626
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Conference paper (peer-reviewed)abstract
- n this paper we propose an extension of the space alternating generalized expectation maximization (SAGE) algorithm that accepts as input and provides as output soft information. This so-called soft-input soft-output (SISO) SAGE algorithm is applied to joint successive interference cancellation and channel estimation and combined with SISO single-user decoders in an iterative CDMA receiver. Monte Carlo simulations in flat Rayleigh fading channel show that this receiver is robust against channel estimation errors and can support a high system load.
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| 4. |
- Kim, Thanh Tung, et al.
(author)
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On the convergence behavior of weighted space-time bit-interleaved coded modulation
- 2004
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In: Conference Record Of The Thirty-Eighth Asilomar Conference On Signals, Systems & Computers. - New York : IEEE. - 0780386221 ; , s. 1257-1261
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Conference paper (peer-reviewed)abstract
- We have recently proposed to use a so-called mixing matrix to improve the performance of a space-time bit-interleaved coded modulation system with channel state information at the transmitter (CSIT). The present paper reviews the general system setup, and then focuses on the impact of mixing matrices on the extrinsic information transfer characteristics of the inner detector. Our results show that with the mixing technique, a fixed outer code can interact efficiently with the inner detector under different assumptions on the quality of CSIT. Therefore, when combined with a turbo code, the proposed scheme performs very close to the capacity limits, even with partial CSIT.
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| 5. |
- Lundberg, Magnus, et al.
(author)
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Multi-rank Capon beamforming
- 2004
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In: Conference Record of the Thirty-Eighth Asilomar Conference on Signals, Systems and Computers. - : IEEE Communications Society. - 0780386221 ; , s. 2335-2339
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Conference paper (peer-reviewed)abstract
- This paper presents a multi-rank extension of the Capon beamformer. By expanding the rank of the beamformer it is possible to fully exploit situations in which signals lie in multi-dimensional subspaces, as opposed to the standard point source case. Such situations are commonly caused by array mismatches and scattered or distributed sources. The extension involves the design of a constraint matrix which can be interpreted in terms of signal power. Three possible choices for the constraint are proposed. These correspond to one non-adaptive choice, one choice that is dependent on the signal covariance structure only, and one choice that is both signal and data adaptive. Simulation examples are presented that show the promise of the idea of multi-rank Capon beamforming. Especially the signal- and data adaptive constraint appears very promising.
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| 6. |
- Pezeshki, Ali, et al.
(author)
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Empirical canonical correlation analysis in subspaces
- 2004
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In: Conference Record of the Thirty-Eighth Asilomar Conference on Signals, Systems and Computers. - : IEEE Communications Society. - 0780386221 ; , s. 994-997
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Conference paper (peer-reviewed)abstract
- This paper addresses canonical correlation analysis of two-channel data, when channel covariances are estimated from a limited number of samples, and are not necessarily full-rank. We show that empirical canonical correlations measure the cosines of the principal angles between the row spaces of the data matrices for the two channels. When the number of samples is smaller than the sum of the ranks of the two data matrices, some of the empirical canonical correlations become one, regardless of the two-channel model that generates the samples. In such cases, the empirical canonical correlations may not be used as estimates of correlation between random variables.
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| 7. |
- Selén, Yngve, et al.
(author)
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A model averaging approach for equalizing sparse communication channels
- 2004
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In: Conference Record of the 38th Asilomar Conference on Signals, Systems, and Computers. - : IEEE. - 0780386221 ; , s. 677-681
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Conference paper (peer-reviewed)abstract
- In communication applications it is important forequalization to have a good estimate of the channel over whichthe signal was transfered.In this paper we introduce the concept ofmodel averaging, where several channel estimates are used in a weightedmanner, to sparse communication channel estimation and equalization forchannels with intersymbol interference.We show via numericalexamples that the bit-error-rate (BER) can be reduced byour suggested method, compared to the BERs obtained usingchannel estimation methods not assuming any sparsity of the channel.
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| 8. |
- Sezgin, A., et al.
(author)
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Antenna selection with capacity-approaching space-time block codes
- 2004
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In: CONFERENCE RECORD OF THE THIRTY-EIGHTH ASILOMAR CONFERENCE ON SIGNALS, SYSTEMS & COMPUTERS, VOLS 1 AND 2. - 0780386221 ; , s. 1291-1294
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Conference paper (peer-reviewed)abstract
- Recently, a quasi-orthogonal space-time block code (QSTBC) capable of approaching the maximum outage mutual information of a MIMO system for the case of four transmit and one receive antennas was proposed. Based on the generalization of these QSTBC to 2(n) transmit antennas and arbitrary number of receive antennas, we analyze the impact of antenna selection (AS) by choosing one out of n(R) receive antennas based on different selection criteria on both the outage probability and the bit error rate. Furthermore, we derive a lower bound for the fraction of outage probability achieved with QSTBC combined with AS. Simulation results show, that even the ZF-detector with AS outperforms the ML-detector without AS by using only one extra antenna, thereby dramatically reducing the computational complexity of the receiver.
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| 9. |
- Svensson, Lennart, 1976, et al.
(author)
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Estimating complex covariance matrices
- 2004
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In: Conference Record of the Thirty-Eighth Asilomar Conference on Signals, Systems and Computers. - : IEEE Communications Society. - 0780386221 ; , s. 2151-2154
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Conference paper (peer-reviewed)abstract
- The problem of estimating complex covariance matrices is considered. The objective is to obtain a well behaving estimator that circumvents the weaknesses of the standard sample covariance and regularized estimators. To this end, we use a variational technique that previously has been successfully applied in the real data case. As a side result, an important identity for complex Wishart distributions is also derived. Simulations indicate substantial improvements compared to both the sample covariance and the regularized estimator.
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