| 1. |
- Ainomäe, Ahti, 1981-, et al.
(författare)
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Distributed Diffusion LMS based Energy Detection
- 2014
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Ingår i: Proceedings of 6th International Congress on Ultra Modern Telecommunications and Control Systems and Workshops (ICUMT), 2014. ; , s. 176-183
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Konferensbidrag (refereegranskat)abstract
- Cognitive radio (CR) is seen as a promising technology to make radio spectrum usage more effective by providing an opportunistic access for secondary users to the licensed spectrum areas. CR systems need to detect the presence of a primary user (PU) signal by continuously sensing the spectrum area of interest. Radiowave propagation effects like fading and shadowing often complicate sensing of spectrum holes because the PU signal can be weak in a particular area. Cooperative spectrum sensing is seen as a prospective solution to enhance the detection of PU signals. This paper studies distributed spectrum sensing in a cognitive radio context. We investigate distributed energy detection schemes without using any fusion center. We propose the usage of distributed, diffusion least mean square (LMS) type of power estimation algorithms. In this paper an Adapt and Combine (ATC) diffusion based power estimation scheme is proposed and the performance is compared with the Combine and Adapt (CTA) and ring-around schemes in a common framework. The PU signal is assumed to be slowly fading. We analyse the resulting energy detection performance and verify the theoretical findings through simulations.
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| 2. |
- Ainomäe, Ahti, 1981-, et al.
(författare)
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Distributed Recursive Energy Detection
- 2014
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Ingår i: Proceedings of Wireless Communications and Networking Conference (WCNC), 2014. - : IEEE Communications Society. ; , s. 1242-1247
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Konferensbidrag (refereegranskat)abstract
- Recent studies have shown that, while the available licensed radio spectrum becomes more occupied, the assigned spectrum is significantly underutilized. To alleviate the situation, cognitive radio (CR) technology has been proposed to provide an opportunistic access to the licensed spectrum areas. CR systems are able to serve the secondary users for detecting and utilizing so called spectrum holes by sensing and adapting to the environment without causing harmful effects or interference to the licensed primary users (PU). CR systems need to detect the presence of a primary user by continuously sensing the spectrum area of interest. Radiowave propagation effects like fading and shadowing often complicate sensing of spectrum holes because the PU signal can be weak in a particular area. Cooperative spectrum sensing is seen as a prospective solution to enhance the detection of PU signals. This paper studies distributed spectrum sensing in a cognitive radio context. We investigate a distributed energy detection scheme without using any fusion center. Due to reduced communication such a topology is more energy efficient. The PU signal is assumed to be in slow fading. A recursive distributed power estimation and detection scheme is proposed. The theoretical findings are verified through simulations.
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| 3. |
- Aldayel, Omar, et al.
(författare)
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Evaluation of MIMO channel non-stationarity
- 2013
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Ingår i: 2013 Proceedings of the 21st European Signal Processing Conference (EUSIPCO). - : IEEE. - 9780992862602 ; , s. 6811769-
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Konferensbidrag (refereegranskat)abstract
- Several MIMO processing algorithms have been proposed that exploit long-term channel statistics, relaying on the critical assumption that this long-term information is valid long enough. In this paper, we consider the Correlation Matrix Distance (CMD) method previously proposed for the evaluation of MIMO channel non-stationarity. We highlight a couple of problems with the CMD measure and propose two new metrics that are more appropriate for non-stationarity evaluation. The performance of the CMD method and new correlation matrix distance metrics is investigated using measured 4×4 MIMO channels. Both Line-of-Sight (LOS) and Non-LOS (NLOS) environments are considered.
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| 4. |
- Anton-Haro, Caries, et al.
(författare)
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Cross-layer scheduling for multi-user MIMO systems
- 2006
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Ingår i: IEEE Communications Magazine. - 0163-6804 .- 1558-1896. ; 44:9, s. 39-45
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Tidskriftsartikel (refereegranskat)abstract
- The increasing demand of wireless services associated with the scarcity of the radio spectrum and the trend to provide end-to-end QoS in emerging and future applications calls for the design of spectrally efficient systems with QoS support. To fulfill these two requirements of spectral efficiency and QoS provision in the highly dynamic environment of mobile radio requires the collaboration of several layers in the system as well as the use of multiple transmit and receive antennas. In a packet network, one important component to achieve the aforementioned efficiency goals is a properly designed scheduling algorithm. Using an information-theoretic framework, we present an overview of the issues associated with the design of packet scheduling algorithms and review several proposed solutions. The article focuses on the advantages of a cross-layer approach to the resource allocation problem and identifies the trade-offs associated with the increased signaling needs. Also, we thoroughly discuss the additional degrees of freedom that multiple transmit and receive antennas can provide.
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| 5. |
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| 6. |
- Bengtsson, Mats, 1967-, et al.
(författare)
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A generalization of weighted subspace fitting to full-rank models
- 2001
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Ingår i: IEEE Transactions on Signal Processing. - : Institute of Electrical and Electronics Engineers (IEEE). - 1053-587X .- 1941-0476. ; 49:5, s. 1002-1012
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Tidskriftsartikel (refereegranskat)abstract
- The idea of subspace fitting provides a popular framework for different applications of parameter estimation and system identification. Previously, some algorithms have been suggested based on similar ideas, for a sensor array processing problem where the underlying data model is not low rank. We show that two of these algorithms (DSPE and DISPARE) fail to give consistent estimates and introduce a general class of subspace fitting-like algorithms for consistent estimation of parameters from a possibly full-rank data model. The asymptotic performance is analyzed, and an optimally weighted algorithm is derived. The result gives a lower bound on the estimation performance for any estimator based on a low-rank approximation of the linear space spanned by the sample data. We show that in general, for full-rank data models, no subspace-based method can reach the Cramer-Rao lower bound (CRB)
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| 7. |
- Bengtsson, Mats, 1967-
(författare)
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A pragmatic approach to multi-user spatial multiplexing
- 2002
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Ingår i: SAM2002. - NEW YORK : IEEE. - 0780375513 ; , s. 130-134
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Konferensbidrag (refereegranskat)abstract
- We suggest a new approach for spatial multiplexing in a narrowband system with several access points serving a number of mobile terminals. In contrast to previously suggested algorithms, this approach is formulated based on a systems perspective, generalizing earlier algorithms for jointly optimal beamforming and power control. Since global channel knowledge is required, the algorithm is mainly intended for system simulations where it provides a benchmark for the performance of any spatial multiplexing scheme with equal rate on the spatial channels.
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| 8. |
- Bengtsson, Mats, 1967-, et al.
(författare)
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Comparison and Cost Analysis of Smart and Opportunistic MIMO OFDM Schemes
- 2006
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Ingår i: IST Mobile & Wireless Communications Summit 2006.
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Konferensbidrag (refereegranskat)abstract
- This paper attempts to compare the system downlinkperformance of a smart antenna scheme for OFDMA thatutilizes channel covariance information with an opportunisticmulti-antenna scheme for OFDMA that uses fast limited feedbackof the instantaneous channel condition. The schemes areevaluated by means of simulations in a low load scenario andalso compared to a simple HSDPA-like scheme. The smartantenna method manages to utilize the multiple antennas betterthan the opportunistic scheme. Furthermore, the performanceof the schemes is inserted into a cost model that assumes thatthe receivers are relays that use short-range technologies tocommunicate with user equipments. Also in terms of cost peruser equipment, the smart antenna scheme proves to be moresuitable for the studied scenario.
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