| 1. |
- Axell, Erik, et al.
(författare)
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On the Optimal K-term Approximation of a Sparse Parameter Vector MMSE Estimate
- 2009
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Ingår i: Proceedings of the 2009 IEEE Workshop on Statistical Signal Processing (SSP'09). - : IEEE. - 9781424427093 ; , s. 245-248
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Konferensbidrag (refereegranskat)abstract
- This paper considers approximations of marginalization sums thatarise in Bayesian inference problems. Optimal approximations ofsuch marginalization sums, using a fixed number of terms, are analyzedfor a simple model. The model under study is motivated byrecent studies of linear regression problems with sparse parametervectors, and of the problem of discriminating signal-plus-noise samplesfrom noise-only samples. It is shown that for the model understudy, if only one term is retained in the marginalization sum, thenthis term should be the one with the largest a posteriori probability.By contrast, if more than one (but not all) terms are to be retained,then these should generally not be the ones corresponding tothe components with largest a posteriori probabilities.
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| 2. |
- Axell, Erik
(författare)
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Spectrum Sensing Algorithms Based on Second-Order Statistics
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Cognitive radio is a new concept of reusing spectrum in an opportunistic manner. Cognitive radio is motivated by recent measurements of spectrum utilization, showing unused resources in frequency, time and space. Introducing cognitive radios in a primary network inevitably creates increased interference to the primary users. Secondary users must sense the spectrum and detect primary users' signals at very low SNR, to avoid causing too much interference.This dissertation studies this detection problem, known as spectrum sensing.The fundamental problem of spectrum sensing is to discriminate an observation that contains only noise from an observation that contains a very weak signal embedded in noise. In this work, detectors are derived that exploit known properties of the second-order moments of the signal. In particular, known structures of the signal covariance are exploited to circumvent the problem of unknown parameters, such as noise and signal powers or channel coefficients.The dissertation is comprised of six papers, all in different ways related to spectrum sensing based on second-order statistics. In the first paper, we considerspectrum sensing of orthogonal frequency-division multiplexed (OFDM) signals in an additive white Gaussian noise channel. For the case of completely known noise and signal powers, we set up a vector-matrix model for an OFDM signal with a cyclic prefix and derive the optimal Neyman-Pearson detector from first principles. For the case of completely unknown noise and signal powers, we derive a generalized likelihood ratio test (GLRT) based on empirical second-order statistics of the received data. The proposed GLRT detector exploits the non-stationary correlation structure of the OFDM signal and does not require any knowledge of the noise or signal powers.In the second paper, we create a unified framework for spectrum sensing of signals which have covariance matrices with known eigenvalue multiplicities. We derive the GLRT for this problem, with arbitrary eigenvalue multiplicities under both hypotheses. We also show a number of applications to spectrum sensing for cognitive radio.The general result of the second paper is used as a building block, in the third and fourth papers, for spectrum sensing of second-order cyclostationary signals received at multiple antennas and orthogonal space-time block coded (OSTBC) signals respectively. The proposed detector of the third paper exploits both the spatial and the temporal correlation of the received signal, from knowledge of the fundamental period of the cyclostationary signal and the eigenvalue multiplicities of the temporal covariance matrix.In the fourth paper, we consider spectrum sensing of signals encoded with an OSTBC. We show how knowledge of the eigenvalue multiplicities of the covariance matrix are inherent owing to the OSTBC, and propose an algorithm that exploits that knowledge for detection. We also derive theoretical bounds on the performance of the proposed detector. In addition, we show that the proposed detector is robust to a carrier frequency offset, and propose another detector that deals with timing synchronization using the detector for the synchronized case as a building block.A slightly different approach to covariance matrix estmation is taken in the fifth paper. We consider spectrum sensing of Gaussian signals with structured covariance matrices, and propose to estimate the unknown parameters of the covariance matrices using covariance matching estimation techniques (COMET). We also derive the optimal detector based on a Gaussian approximation of the sample covariance matrix, and show that this is closely connected to COMET.The last paper deals with the problem of discriminating samples that containonly noise from samples that contain a signal embedded in noise, 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 andit has applications in signal denoising, anomaly detection, and spectrum sensing for cognitive radio.
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| 3. |
- Larsson, Erik G., et al.
(författare)
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The Cramer-Rao Bound for Continuous-Time Autoregressive Parameter Estimation with Irregular Sampling
- 2002
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Ingår i: Circuits, systems, and signal processing. - : Springer Science and Business Media LLC. - 0278-081X .- 1531-5878. ; 21:6, s. 581-601
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Tidskriftsartikel (refereegranskat)abstract
- We consider the problem of estimating the parameters in a continuous-time autoregressive model given measurements taken at arbitrary time instants. This problem is of importance in applications ranging from time-series analysis to automatic control. We derive the Cramer-Rao bound (CRB) for this estimation problem by using a technique based on the Slepian-Bang's formula and residue calculus. Furthermore, we investigate by means of numerical experiments how different sampling schemes can affect the achievable estimation accuracy. We demonstrate that the achievable estimation accuracy is relatively insensitive to the choice of sampling strategy, even though it is generally not identical for different sampling schemes. This observation is also in line with recent results on parameter estimation for polynomial-phase signals. Finally, we discuss the asymptotic properties ofthe CRB.
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| 4. |
- Larsson, Erik K., et al.
(författare)
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Cramer-Rao bounds for continuous-time AR parameter estimation with irregular sampling
- 2001
-
Ingår i: Proc. of IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), 2001. vol. 5. - 0780370414 ; , s. 3097-3100
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Konferensbidrag (refereegranskat)abstract
- Consider the problem of estimating the parameters in a continuous-time autoregressive (AR) model given measurements taken at arbitrary time instants. In this paper the Cramer-Rao bound for this problem is derived by using a technique based on the Slepian-Bang's formula and residue calculus. Furthermore, we investigate by means of numerical experiments how different sampling schemes can affect the accuracy. Interestingly enough, however, for the examples studied, the estimation accuracy is relatively insensitive to the choice of sampling strategy.
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| 5. |
- Larsson, Erik K., et al.
(författare)
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The CRB for parameter estimation in irregularly sampled continuous-time ARMA system
- 2003
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Ingår i: Proc. of IEEE International Symposium on Signal Processing and Information Technology, (Darmstadt, Germany), Dec. 2003. - 0780382927 ; , s. 110-113
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Konferensbidrag (refereegranskat)abstract
- We derive novel and compact formulas for the Cramer-Rao bound (CRB) associated with the identification of the parameters in a continuous-time autoregressive moving-average (ARMA) model, given the nonuniformity of the sampled data. Our approach is based on a state-space formulation of the ARMA model, which facilitates a derivation of the CRB in closed form. Numerical examples illustrate our results.
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| 6. |
- Larsson, Erik K., et al.
(författare)
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The CRB for Parameter Estimation in IrregularlySampled Continuous-Time ARMA Systems
- 2004
-
Ingår i: IEEE Signal Processing Letters. - 1070-9908 .- 1558-2361. ; 11:2, s. 197-200
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Tidskriftsartikel (refereegranskat)abstract
- We derive novel and compact formulas for the Cramer-Rao bound (CRB) associated with the identification of the parameters in a continuous-time autoregressive moving-average (ARMA) model, given nonuniformly sampled data. Our approach is based on a state-space formulation of the ARMA model, which facilitates a derivation of the CRB in closed form. Numerical examples illustrate our results.
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| 7. |
- Östrand, Fredrik, et al.
(författare)
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Stereoisomeric composition of the sex pheromone of the pine sawfly Microdiprion pallipes (Hym., Diprionidae)
- 2003
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Ingår i: Chemoecology. - : Springer Science and Business Media LLC. - 0937-7409 .- 1423-0445. ; 13:3, s. 155-162
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Tidskriftsartikel (refereegranskat)abstract
- The basic chemical structure of the sex pheromone of the pine sawfly Microdiprion pallipes (Fallen) has earlier been identified as the propionate ester of (2S,3S,7 R/S,11 R/S)/(2R,3R,7 R/S,11 R/S)-3,7,11-trimethyl-2-tridecanol. We now report the results from further investigations on the male response to individual stereoisomers and to blends of stereoisomers, both in electroantennographic (EAG) recordings and in field trapping experiments. We also present our attempts to determine the stereochemistry of the compounds present in females of M. pallipes. By comparing gas chromatograms and mass spectra obtained from natural extracts with those from synthetic compounds it was found that the females contain one or more of the four (2S,3S,7 R/S,11 R/S)-3,7,11-trimethyl-2-tridecanol isomers (SS++-1). The active pheromone component is the corresponding propionate ester 2. In EAG experiments, males responded most strongly to five propionate ester samples, namely two four-isomer blends: SS++-2 and SR++-2, and three individual stereoisomers: SSSR-, SRRR- and SRSR-2. In a series of field trapping experiments it was found that males were attracted to the SR++-2 four-isomer blend and to the individual isomer SSSR-2. Based on the EAG-recordings and field responses of males and the stereoisomers found in the females, we suggest that the propionate ester of (2S,3S,7S,11R)-3,7,11-trimethyl-2-tridecanol (SSSR-2) is used as a main component of the sex pheromone in M. pallipes. Apparently the males react to other stereoisomers in addition to that or those produced by the females.
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| 8. |
- Abarenkov, Kessy, et al.
(författare)
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Annotating public fungal ITS sequences from the built environment according to the MIxS-Built Environment standard – a report from a May 23-24, 2016 workshop (Gothenburg, Sweden)
- 2016
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Ingår i: MycoKeys. - : Pensoft Publishers. - 1314-4057 .- 1314-4049. ; 16, s. 1-15
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Tidskriftsartikel (refereegranskat)abstract
- Recent molecular studies have identified substantial fungal diversity in indoor environments. Fungi and fungal particles have been linked to a range of potentially unwanted effects in the built environment, including asthma, decay of building materials, and food spoilage. The study of the built mycobiome is hampered by a number of constraints, one of which is the poor state of the metadata annotation of fungal DNA sequences from the built environment in public databases. In order to enable precise interrogation of such data – for example, “retrieve all fungal sequences recovered from bathrooms” – a workshop was organized at the University of Gothenburg (May 23-24, 2016) to annotate public fungal barcode (ITS) sequences according to the MIxS-Built Environment annotation standard (http://gensc.org/mixs/). The 36 participants assembled a total of 45,488 data points from the published literature, including the addition of 8,430 instances of countries of collection from a total of 83 countries, 5,801 instances of building types, and 3,876 instances of surface-air contaminants. The results were implemented in the UNITE database for molecular identification of fungi (http://unite.ut.ee) and were shared with other online resources. Data obtained from human/animal pathogenic fungi will furthermore be verified on culture based metadata for subsequent inclusion in the ISHAM-ITS database (http://its.mycologylab.org).
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| 9. |
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| 10. |
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| 11. |
- Adolfsson, Dan, et al.
(författare)
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On Scan Chain Diagnosis for Intermittent Faults
- 2009
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Ingår i: <em>IEEE Asian Test Symposium (ATS), Taichung, Taiwan, November 23-26, 2009.</em>. ; , s. 47-54
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Konferensbidrag (refereegranskat)abstract
- Diagnosis is increasingly important, not only for individual analysis of failing ICs, but also for high-volume test response analysis which enables yield and test improvement. Scan chain defects constitute a significant fraction of the overall digital defect universe, and hence it is well justified that scan chain diagnosis has received increasing research attention in recent years. In this paper, we address the problem of scan chain diagnosis for intermittent faults. We show that the conventional scan chain test pattern is likely to miss an intermittent fault, or inaccurately diagnose it. We propose an improved scan chain test pattern which we show to be effective. Subsequently, we demonstrate that the conventional bound calculation algorithm is likely to produce wrong results in the case of an intermittent fault. We propose a new lowerbound calculation method which does generate correct and tight bounds, even for an intermittence probability as low as 10%.
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| 12. |
- af Rosenschöld, Per Munck, et al.
(författare)
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The MCNP Monte Carlo Program
- 2012. - 2nd
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Ingår i: Monte Carlo Calculations in Nuclear Medicine : Applications in Diagnostic Imaging - Applications in Diagnostic Imaging. - : Taylor & Francis. - 9781439841099 - 9781439841105 ; , s. 153-172
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Bokkapitel (refereegranskat)abstract
- Monte Carlo N-Particle (MCNP) is a Monte Carlo code package allowing coupled neutron, photon, and electron transport calculations. Also, the possibility of performing heavy charged particle transport calculations was recently introduced with the twin MCNPX code package. An arbitrary three-dimensional problem can be formulated through the use of surfaces defining building blocks (“cells” that are assigned density, material, and relevant cross-section tables. The source can be specified as point, surface, or volumes using generic or as a phase/space file.
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| 13. |
- Ahlgren, Erik, 1962, et al.
(författare)
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Biokombi Rya - slutrapporter från ingående delprojekt
- 2007
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Inom projektet Biokombi Rya har ett flertal olika forskargrupper samarbetat för att studera system¬effekterna av förgasning av biobränsle ur olika aspekter. Syftet med projektet är att öka kunskapen om biobränsleförgasning i Sverige samt att utreda förutsättningar för att sådana anläggningar ska vara ekonomiskt och miljömässigt intressanta. En referensgrupp har varit kopplad till projektet där förutsättningar, resultat och slutsatser har behandlats.I denna underlagsrapport har slutrapporterna från projektets delprojekt samlats. De beskriver förutsättningar, metodansatser, använda data och resultat utförligt och utgör på så sätt ett viktigt komplement till den mer övergripande beskrivningen i projektets syntesrapport. De delrapporter som ingår har valts för att täcka in samtliga delar av projektet som är av allmänt intresse. Projektresultat som publicerats på annat sätt berörs dock mer kortfattat.Projektet Biokombi Rya har pågått under två år (2005-2006) och drivits av Chalmers EnergiCentrum. Förutom de omfattande analysinsatser som författarna till denna rapport står för, har Avdelningen för kemisk teknologi vid KTH, Siemens Industrial Turbines AB och Göteborg Energi AB bidragit med expertstöd. CIT Industriell Energianalys, med undertecknad som projektledare, har stått för projektledning och koordination.Projektet har finansierats av Energimyndigheten, Göteborg Energis forsknings¬stiftelse samt Göteborg Energi AB.
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| 14. |
- Allard, Christina, et al.
(författare)
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Rasbiologiskt språkbruk i statens rättsprocess mot sameby : DN Debatt 2015-06-11
- 2015
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Annan publikation (populärvet., debatt m.m.)abstract
- Statens hantering av forskningsresultat i rättsprocessen med Girjas sameby utgör ett hot mot Sverige som rättsstat och kunskapsnation. Åratal av svensk och internationell forskning underkänns och man använder ett språkbruk som skulle kunna vara hämtat från rasbiologins tid. Nu måste staten ta sitt ansvar och börja agera som en demokratisk rättsstat, skriver 59 forskare.
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| 15. |
- Altai, Mohamed, et al.
(författare)
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188Re-ZHER2:V2, a promising affibody-based targeting agent against HER2-expressing tumors : preclinical assessment
- 2014
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Ingår i: Journal of nuclear medicine : official publication, Society of Nuclear Medicine. - : Society of Nuclear Medicine. - 0161-5505 .- 1535-5667 .- 2159-662X. ; 55:11, s. 8-1842
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Tidskriftsartikel (refereegranskat)abstract
- UNLABELLED: Affibody molecules are small (7 kDa) nonimmunoglobulin scaffold proteins with favorable tumor-targeting properties. Studies concerning the influence of chelators on biodistribution of (99m)Tc-labeled Affibody molecules demonstrated that the variant with a C-terminal glycyl-glycyl-glycyl-cysteine peptide-based chelator (designated ZHER2:V2) has the best biodistribution profile in vivo and the lowest renal retention of radioactivity. The aim of this study was to evaluate (188)Re-ZHER2:V2 as a potential candidate for radionuclide therapy of human epidermal growth factor receptor type 2 (HER2)-expressing tumors.METHODS: ZHER2:V2 was labeled with (188)Re using a gluconate-containing kit. Targeting of HER2-overexpressing SKOV-3 ovarian carcinoma xenografts in nude mice was studied for a dosimetry assessment.RESULTS: Binding of (188)Re-ZHER2:V2 to living SKOV-3 cells was demonstrated to be specific, with an affinity of 6.4 ± 0.4 pM. The biodistribution study showed a rapid blood clearance (1.4 ± 0.1 percentage injected activity per gram [%ID/g] at 1 h after injection). The tumor uptake was 14 ± 2, 12 ± 2, 5 ± 2, and 1.8 ± 0.5 %IA/g at 1, 4, 24, and 48 h after injection, respectively. The in vivo targeting of HER2-expressing xenografts was specific. Already at 4 h after injection, tumor uptake exceeded kidney uptake (2.1 ± 0.2 %IA/g). Scintillation-camera imaging showed that tumor xenografts were the only sites with prominent accumulation of radioactivity at 4 h after injection. Based on the biokinetics, a dosimetry evaluation for humans suggests that (188)Re-ZHER2:V2 would provide an absorbed dose to tumor of 79 Gy without exceeding absorbed doses of 23 Gy to kidneys and 2 Gy to bone marrow. This indicates that future human radiotherapy studies may be feasible.CONCLUSION: (188)Re-ZHER2:V2 can deliver high absorbed doses to tumors without exceeding kidney and bone marrow toxicity limits.
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| 16. |
- Andersson, Anton, et al.
(författare)
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Design of a Foiling Optimist
- 2018
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Ingår i: Journal of Sailboat Technology. ; 2018, s. 1-24
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Tidskriftsartikel (refereegranskat)abstract
- Because of the successful application of hydrofoils on the America's Cup catamarans in the past two campaigns the interest in foiling sailing craft has boosted. Foils have been fitted to a large number of yachts with great success, ranging from dinghies to ocean racers. An interesting question is whether one of the slowest racing boats in the world, the Optimist dinghy, can foil, and if so, at what minimum wind speed. The present paper presents a comprehensive design campaign to answer the two questions. The campaign includes a newly developed Velocity Prediction Program (VPP) for foiling/non-foiling conditions, a wind tunnel test of sail aerodynamics, a towing tank test of hull hydrodynamics and a large number of numerical predictions of foil characteristics. An optimum foil configuration is developed and towing tank tested with satisfactory results. The final proof of the concept is a successful on the water test with stable foiling at a speed of 12 knots.
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| 17. |
- Axell, Erik, 1980-, et al.
(författare)
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A Bayesian Approach to Spectrum Sensing, Denoising and Anomaly Detection
- 2009
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Ingår i: Proceedings of the 34th IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP'09). - 9781424423545 - 9781424423538 ; , s. 2333-2336
-
Konferensbidrag (refereegranskat)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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| 18. |
- Axell, Erik, et al.
(författare)
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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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Ingår i: Proceedings of the IEEE International Conference on Acoustics, Speech and SignalProcessing (ICASSP). - : IEEE conference proceedings. ; , s. 2956-2959
-
Konferensbidrag (refereegranskat)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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| 19. |
- Axell, Erik, et al.
(författare)
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Capacity Considerations for Uncoordinated Communication in Geographical Spectrum Holes
- 2009
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Ingår i: Physical Communication. - : Elsevier. - 1874-4907. ; 2:1-2, s. 3-9
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Tidskriftsartikel (refereegranskat)abstract
- Cognitive radio is a new concept of reusing a licensed spectrum in an unlicensed manner. The motivation for cognitive radio is various measurements of spectrum utilization, that generally show unused resources in frequency, time and space. These "spectrum holes" could be exploited by cognitive radios. Some studies suggest that the spectrum is extremely underutilized, and that these spectrum holes could provide ten times the capacity of all existing wireless devices together. The spectrum could be reused either during time periods where the primary system is not active, or in geographical positions where the primary system is not operating. In this paper, we deal primarily with the concept of geographical reuse, in a frequency-planned primary network. We perform an analysis of the potential for communication in a geographical spectrum hole, and in particular the achievable sum-rate for a secondary network, to some order of magnitude. Simulation results show that a substantial sum-rate could be achieved if the secondary users communicate over small distances. For a small number of secondary links, the sum-rate increases linearly with the number of links. However, the spectrum hole gets saturated quite fast, due to interference caused by the secondary users. A spectrum hole may look large, but it disappears as soon as someone starts using it.
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| 20. |
- Axell, Erik, et al.
(författare)
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Comments on "Multiple Antenna Spectrum Sensing in Cognitive Radios"
- 2011
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Ingår i: IEEE Transactions on Wireless Communications. - : IEEE. - 1536-1276 .- 1558-2248. ; 10:5, s. 1678-1680
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Tidskriftsartikel (refereegranskat)abstract
- We point out an error in a derivation in the recent paper [1], and provide a correct and much shorter calculation of the result in question. In passing, we also connect the results in [1] to the literature on array signal processing and on principal component analysis, and show that the main findings of [1] follow as special cases of standard results in these fields.
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| 21. |
- Axell, Erik, et al.
(författare)
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Eigenvalue-Based Spectrum Sensing of Orthogonal Space-Time Block Coded Signals
- 2012
-
Ingår i: IEEE Transactions on Signal Processing. - : Institute of Electrical and Electronics Engineers (IEEE). - 1053-587X .- 1941-0476. ; 60:12, s. 6724-6728
-
Tidskriftsartikel (refereegranskat)abstract
- We consider spectrum sensing of signals encoded with an orthogonal space-time block code (OSTBC). We propose a CFAR detector based on knowledge of the eigenvalue multiplicities of the covariance matrix which are inherent owing to the OSTBC and derive theoretical performance bounds. In addition, we show that the proposed detector is robust to a carrier frequency offset, and propose a detector that deals with timing synchronization using the detector for the synchronized case as a building block. The proposed detectors are shown numerically to perform well.
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| 22. |
- Axell, Erik, et al.
(författare)
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GNSS spoofing detection using multiple mobile COTS receivers
- 2015
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Ingår i: ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781467369978 ; , s. 3192-3196
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Konferensbidrag (refereegranskat)abstract
- In this paper we deal with spoofing detection in GNSS receivers. We derive the optimal genie detector when the true positions are perfectly known, and the observation errors are Gaussian, as a benchmark for other detectors. The system model considers three dimensional positions, and includes correlated errors. In addition, we propose several detectors that do not need any position knowledge, that outperform recently proposed detectors in many interesting cases.
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| 23. |
- Axell, Erik, et al.
(författare)
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Multiantenna Spectrum Sensing of a Second-Order Cyclostationary Signal
- 2011
-
Ingår i: Proceedings of the 4th IEEE International Workshop on Computational Advances in Multi-Sensor Adaptive Processing (CAMSAP'11). - 9781457721038 ; , s. 329-332
-
Konferensbidrag (refereegranskat)abstract
- We consider spectrum sensing of a second-order cyclostationary signal receivedat multiple antennas. The proposed detector exploits both the spatial andthe temporal correlation of the received signal, from knowledge of thefundamental period of the cyclostationary signal and the eigenvaluemultiplicities of the temporal covariance matrix. All other parameters, suchas the channel gains or the noise power, are assumed to be unknown. The proposeddetector is shown numerically to outperform state-of-the-art detectors forspectrum sensing of anOFDM signal, both when using a single antenna and with multiple antennas.
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| 24. |
- Axell, Erik, et al.
(författare)
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Optimal and Near-Optimal Spectrum Sensing of OFDM Signals in AWGN Channels
- 2010
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Ingår i: Proceedings of the International Workshop on Cognitive Information Processing (CIP).
-
Konferensbidrag (refereegranskat)abstract
- We consider spectrum sensing of OFDM signals in an AWGN channel. For the case of completely unknown noise and signal powers, we derive a GLRT detector based on empirical second-order statistics of the received data. The proposed GLRT detector exploits the non-stationary correlation structure of the OFDM signal and does not require any knowledge of the noise power or the signal power. The GLRT detector is compared to state-of-the-art OFDM signal detectors, and shown to improve the detection performance with 5 dB SNR in relevant cases. For the case of completely known noise power and signal power, we present a brief derivation of the optimal Neyman-Pearson detector from first principles. We compare the optimal detector to the energy detector numerically, and show that the energy detector is near-optimal (within 0.2 dB SNR) when the noise variance is known. Thus, when the noise power is known, no substantial gain can be achieved by using any other detector than the energy detector.
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| 25. |
- Axell, Erik, et al.
(författare)
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Optimal and Sub-Optimal Spectrum Sensing of OFDM Signals in Known and Unknown Noise Variance
- 2011
-
Ingår i: IEEE Journal on Selected Areas in Communications. - : Institute of Electrical and Electronics Engineers (IEEE). - 0733-8716 .- 1558-0008. ; 29:2, s. 290-304
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Tidskriftsartikel (refereegranskat)abstract
- We consider spectrum sensing of OFDM signals in an AWGN channel. For the case of completely known noise and signal powers, we set up a vector-matrix model for an OFDM signal with a cyclic prefix and derive the optimal Neyman-Pearson detector from first principles. The optimal detector exploits the inherent correlation of the OFDM signal incurred by the repetition of data in the cyclic prefix, using knowledge of the length of the cyclic prefix and the length of the OFDM symbol. We compare the optimal detector to the energy detector numerically. We show that the energy detector is near-optimal (within 1 dB SNR) when the noise variance is known. Thus, when the noise power is known, no substantial gain can be achieved by using any other detector than the energy detector.For the case of completely unknown noise and signal powers, we derive a generalized likelihood ratio test (GLRT) based onempirical second-order statistics of the received data. The proposed GLRT detector exploits the non-stationary correlation structure of the OFDM signal and does not require any knowledge of the noise power or the signal power. The GLRT detector is compared to state-of-the-art OFDM signal detectors, and shown to improve the detection performance with 5 dB SNR in relevant cases.
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