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| 2. |
- Gustafsson, Oscar, 1973-, et al.
(författare)
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An empirical study on standard cell synthesis of elementary function look-up tables
- 2008
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Ingår i: Conference Record - Asilomar Conference on Signals, Systems and Computers. - Piscataway, NJ : IEEE. - 9781424429417 - 9781424429400 ; , s. 1810-1813
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Konferensbidrag (refereegranskat)abstract
- When hardware for implementing elementary functions is discussed it is often stated that for "small enough" tables it is possible to just synthesize the HDL description to standard cells. In this work we investigate this fact and show that the resulting cell area primarily depends on the smallest of the number of input and output bits, while the contribution of the larger of the two bit-widths is significantly smaller.
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| 3. |
- Gustafsson, Oscar, 1973-
(författare)
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Towards optimal multiple constant multiplication : a hypergraph approach
- 2008
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Ingår i: Conference Record of the Asilomar Conference on Signals Systems and Computers. - Piscataway, NJ : IEEE. - 9781424429400 - 9781424429417 ; , s. 1805-1809
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Konferensbidrag (refereegranskat)abstract
- In this work a novel approach to the multiple constant multiplication problem, i.e., finding a realization of a number of constant multiplications by using shift and addition with a minimum number of additions, is presented. By using a directed hypergraph, the problem comes down to finding a Steiner hypertree in the graph. The proposed formulation can guarantee an optimal solution, given that an optimal Steiner hypertree is found. However, finding a Steiner tree in a hypergraph is an NP-hard problem. Therefore, we present algorithms for different partial problems and discuss how they can be used to solve the whole problem. An integer linear programming model is used to solve the Steiner hypertree problem. The model can also include additional constraints such as adder depth and fan-out.
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| 4. |
- Hammarberg, Peter, et al.
(författare)
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On the performance of iterative receivers for interfering MIMO-OFDM systems in measured channels
- 2008
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Ingår i: 42nd Asilomar Conference on Signals, Systems and Computers. - 1058-6393. - 9781424429400 ; , s. 141-145
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Konferensbidrag (refereegranskat)abstract
- This paper investigates the gains harvested through base station cooperation in the up-link for a multi-user (MU) Multiple-Input Multiple-Output Orthogonal Frequency Division Multiplexing (MIMO-OFDM) system, operating in a real indoor environment. The base stations perform joint detection using an iterative receiver that carries out multi-user detection and channel estimation via soft information from the single-user decoders. Performance evaluation is carried out using real channels from an indoor dynamic dual MIMO link measurement campaign. The measured scenario represent a real life situation where two users communicate with two base stations, each with two antennas, in an environment resembling a shopping mall or an airport terminal. System performance is evaluated in terms of both Bit-Error Rate (BER) vs. Signal-to-Interference Ratio (SIR) and Cumulative Distribution Functions (CDF) for the instantaneous BER. Also, the impact of using soft information in the channel estimation is analyzed.
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| 5. |
- Lindahl, Erik, et al.
(författare)
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Architecture-aware design of a decimation filter based on a dual wordlength multiply-accumulate unit
- 2008
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Ingår i: Conference Record - Asilomar Conference on Signals, Systems and Computers. - Piscataway, NJ : IEEE. - 9781424429400 - 9781424429417 ; , s. 1897-1901
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Konferensbidrag (refereegranskat)abstract
- In this work we present the design and implementation of a decimation filter for an audio range AE-modulator. The architecture is based on a dual wordlength multiply-accumulate (MAC) unit to handle the reduced wordlength of the input. Each stage is composed of FIR filters which are mapped to the MAC unit. The design trade-offs and decisions for co-design of architecture and filters are discussed.
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| 6. |
- Lindblom, Johannes, et al.
(författare)
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Parametrization of the MISO Interference Channel with Transmit Beamforming and Partial Channel State Information
- 2008
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Ingår i: Proceedings of the 42nd Asilomar Conference on Signals, Systems and Computers (ACSSC'08). - 9781424429400 ; , s. 1103-1107
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- We study the achievable rate region of the multipleinputsingle-output (MISO) interference channel (IFC), under theassumption that all receivers treat the interference as additiveGaussian noise. The main result is a parameterization of thePareto boundary for the case where there are two users, thetransmitters use beamforming, and the channel state information(CSI) is only partially known at the transmitters. The result isillustrated by two numerical results.
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| 7. |
- Maurer, Johannes, et al.
(författare)
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Multi-threshold top - Full-diversity vector perturbation precodingwith finite-rate feedforward
- 2008
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Ingår i: 2008 42ND ASILOMAR CONFERENCE ON SIGNALS, SYSTEMS AND COMPUTERS. - 9781424429400 ; , s. 428-432
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Konferensbidrag (refereegranskat)abstract
- We consider vector perturbation (VP) precoding for a multiple antenna broadcast scenario with Multiple noncooperative users. Under an instantaneous transmit power constraint, VP precoding requires the feedforward of a power normalization factor to the users. Simple quantization of the power normalization factor is shown to result in an error floor. To overcome this problem, we propose a new precoding scheme that uses a finite set of power normalization factors and avoids transmission at all when the available power is not sufficient to perform channel equalization at the transmit side. With this scheme, full diversity can be achieved (even with imperfect channel state information) while simultaneously significant amounts of transmit power can be saved.
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| 8. |
- Tavares, Marcos B.S., et al.
(författare)
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New Multi-User OFDM Scheme: Braided Code Division Multiple Access
- 2008
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Ingår i: [Host publication title missing]. - 9781424429400 ; , s. 963-967
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Konferensbidrag (refereegranskat)abstract
- In this paper, we present a new multiple access scheme using OFDM modulation which we call braided code division multiple access (BCDMA). The principle behind this novel multiple access technique is to combine in one single scheme a very efficient error correction code, interleaving for channel diversity exploitation and, simultaneously, a multiple access method for a large number of users. BCDMA is based on braided codes, which are iteratively decodable codes defined on graphs and provide excellent performance with relatively low decoding complexity.
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| 9. |
- Thobaben, Ragnar
(författare)
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On Distributed Codes with Noisy Relays
- 2008
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Ingår i: 2008 42ND ASILOMAR CONFERENCE ON SIGNALS, SYSTEMS AND COMPUTERS. - 9781424429400 ; , s. 1010-1014
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Konferensbidrag (refereegranskat)abstract
- In this paper, we address the design of distributed schemes for the 3-node relay channel with half-duplex constraint. We first discuss the general problem of optimally re-encoding noisy data at the relay and summarize recently proposed approximations. Based on an analysis of the extrinsic information transfer characteristics of the component codes we investigate the potential of "weak" Turbo or LDPC codes which are employed by the source node in order to increase the reliability of the relay when decoding is not possible. The results show that we can indeed gain from the proposed code design.
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| 10. |
- 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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