| 1. |
- Gudmundson, Erik, et al.
(författare)
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Efficient Algorithms for Computing the Capon and APES Filters
- 2007
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Ingår i: CONFERENCE RECORD OF THE FORTY-FIRST ASILOMAR CONFERENCE ON SIGNALS, SYSTEMS & COMPUTERS, VOLS 1-5. - 9781424421091 ; , s. 427-430
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Konferensbidrag (refereegranskat)abstract
- The computation of the Capon and the amplitude and phase estimation (APES) filters can be very time consuming. The burden lies not only in the inversion of the sample covariance matrix, but also in the matrix multiplications. In this paper, we propose an efficient algorithm for the computation of the above mentioned filters, using Cholesky Factorization and fast Fourier transforms. Furthermore, we discuss and illustrate the benefits of using the proposed algorithms in the spectral analysis of data with missing samples.
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| 2. |
- Naucler, Peter, et al.
(författare)
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Separation of One-dimensional Waves - a Stochastic Systems Approach
- 2007
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Ingår i: CONFERENCE RECORD OF THE FORTY-FIRST ASILOMAR CONFERENCE ON SIGNALS, SYSTEMS & COMPUTERS, VOLS 1-5. - 9781424421091 ; , s. 661-665
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Konferensbidrag (refereegranskat)abstract
- In various applications it is of interest to extract the wave traveling in a certain direction of a medium. As waves that propagate in different directions generally overlap, it is not possible to directly measure the desired wave. This paper presents techniques for separation of broadband waves governed by the one-dimensional wave equation in the presence of measurement noise. The derived estimators are based on stochastic modeling of the waves and measurement noise, state space representations and optimal state estimation.
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| 3. |
- Thobaben, Ragnar, et al.
(författare)
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Sensor-network-aided cognitive radio : On the optimal receiver for estimate-and-forward protocols applied to the relay channel
- 2007
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Ingår i: CONFERENCE RECORD OF THE FORTY-FIRST ASILOMAR CONFERENCE ON SIGNALS, SYSTEMS & COMPUTERS, VOLS 1-5. - NEW YORK : IEEE. - 9781424421091 ; , s. 777-781
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Konferensbidrag (refereegranskat)abstract
- Cognitive radio describes a promising concept for improving the utilization of radio spectrum. It allows secondary users to access licensed radio spectrum in an opportunistic fashion, given that the quality of service for primary users is maintained. In this scenario, the detection of unused radio spectrum is the main obstacle: it requires the recognition of low-power signals in a noisy environment. Therefore, we consider the case where cognitive users are supported by a wireless sensor network (WSN) providing beliefs on the event that the primary user is active. The beliefs provided by the WSN nodes are then combined by the cognitive radio in order to make a final decision. Due to limitations in complexity, power, and bandwidth, the WSN nodes apply the estimate-and-forward protocol to communicate their beliefs and to relay the beliefs of adjacent nodes. For the case where the WSN is subject to noisy communication links, we derive and analyze the optimal receiver which provides the cognitive radio with log-likelihood ratios for the estimated and forwarded hypotheses. The performance of the optimal receiver is compared to the performance of sub-optimal receivers.
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| 4. |
- von Wrycza, Peter, 1981-, et al.
(författare)
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Decentralized dynamic channel allocation for MIMO systems
- 2007
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Ingår i: CONFERENCE RECORD OF THE FORTY-FIRST ASILOMAR CONFERENCE ON SIGNALS, SYSTEMS & COMPUTERS. - NEW YORK : IEEE. - 9781424421091 ; , s. 1689-1693
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Konferensbidrag (refereegranskat)abstract
- A common scenario in wireless communication systems is one where several systems coexist in the same area and communicate using the same portion of the spectrum, possibly even using different radio interfaces. Herein, we consider non-cooperative spectrum sharing rules for decentralized iterative dynamic channel allocation, based on utility functions, for multi-user systems with multiple antennas at both transmitters and receivers. Using the link rate as a utility function often leads to a suboptimal high-interference situation. The key to obtaining good separation over the scheduling slots, leading to higher spectral utilization, is a proper choice of utility function for the users. To obtain a decentralized scheduler with these desired properties, we introduce the idea of modifying the utility function and investigate its affect on the sum rate. A numerical example illustrates the performance compared to a scheduler employing the link rate as utility function.
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| 5. |
- Yao, Sha, et al.
(författare)
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Dimension expansion relaying for slow fading channels based on hybrid digital-analog source-channel coding
- 2007
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Ingår i: CONFERENCE RECORD OF THE FORTY-FIRST ASILOMAR CONFERENCE ON SIGNALS, SYSTEMS & COMPUTERS. - NEW YORK : IEEE. - 9781424421091 ; , s. 1463-1467
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Konferensbidrag (refereegranskat)abstract
- Hybirid digital-analog coding schemes for dimension compression/expansion have been proposed in source-channel coding to increase the robustness toward channel mismatch, in the absence of transmitter channel state information (CSIT). Recognizing that the same kind of robustness is needed at the relay in a three-node relay network, we propose novel relaying protocols based on hybrid digital-analog transmission. Since we focus on transmission over slow fading channels in the absence of CSIT, we use the notion of expected rate as performance measure. In the scenario where the incoming dimension is expanded by the relay, we present new expressions for expected rates achieved by the proposed hybrid digital-analog protocols. We also compare the performance of the new schemes to traditional digital-only (decode-and-forward or compress-and-forward) or analog-only (amplify-and-forward) relaying, as well as to performance bounds corresponding to genie-aided compress-and-forward relaying. Our new relaying protocols achieve significant gains in terms of achievable expected rates, and they are able to close in on the performance bounds. In particular we conclude that the best overall performance is obtained by an adaptive combination of decode-and-forward and hybrid digital-analog relaying.
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| 6. |
- Zhang, Xi, et al.
(författare)
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Robust MAC MIMO transceiver design with partial CSIT and CSIR
- 2007
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Ingår i: CONFERENCE RECORD OF THE FORTY-FIRST ASILOMAR CONFERENCE ON SIGNALS, SYSTEMS & COMPUTERS, VOLS 1-5. - NEW YORK : IEEE. - 9781424421091 ; , s. 324-328
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Konferensbidrag (refereegranskat)abstract
- In practical wireless systems, the design of linear MIMO transceivers should be robust to imperfect channel state information (CSI), especially in multiuser systems where accurate CSI is difficult to obtain. This paper considers the case in which the CSI is perturbed at both sides of the link. In such a case, it is possible to optimally design robust MIMO transceivers to minimize the average sum MSE of all the data streams and the users. For systems with a sum power constraint, our robust design can be shown to be a convex SDP problem; for systems with individual power constraints, our robust design is based on an underlying SDP problem.
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