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- Aamodt, K., et al.
(författare)
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Alignment of the ALICE Inner Tracking System with cosmic-ray tracks
- 2010
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Ingår i: Journal of Instrumentation. - 1748-0221. ; 5
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Konferensbidrag (refereegranskat)abstract
- ALICE (A Large Ion Collider Experiment) is the LHC (Large Hadron Collider) experiment devoted to investigating the strongly interacting matter created in nucleus-nucleus collisions at the LHC energies. The ALICE ITS, Inner Tracking System, consists of six cylindrical layers of silicon detectors with three different technologies; in the outward direction: two layers of pixel detectors, two layers each of drift, and strip detectors. The number of parameters to be determined in the spatial alignment of the 2198 sensor modules of the ITS is about 13,000. The target alignment precision is well below 10 mu m in some cases (pixels). The sources of alignment information include survey measurements, and the reconstructed tracks from cosmic rays and from proton-proton collisions. The main track-based alignment method uses the Millepede global approach. An iterative local method was developed and used as well. We present the results obtained for the ITS alignment using about 10(5) charged tracks from cosmic rays that have been collected during summer 2008, with the ALICE solenoidal magnet switched off.
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| 8. |
- Han, Sang Wook, et al.
(författare)
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An asynchronous distributed power allocation scheme for sum-rate maximization on cognitive GMACs
- 2013
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Ingår i: Proceedings of 2013 6th Joint IFIP Wireless and Mobile Networking Conference, WMNC 2013. - New York : IEEE. - 9781467356169 ; , s. 6549031-
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Konferensbidrag (refereegranskat)abstract
- This paper considers an asynchronous distributed power allocation scheme for sum-rate-maximization under cognitive Gaussian multiple access channels (GMACs), where primary users and secondary users may communicate under mutual interference with the Gaussian noise. Formulating the problem as a standard nonconvex quadratically constrained quadratic problem (QCQP) provides a simple distributed method to find a solution using iterative Jacobian method instead of using centralized schemes. A totally asynchronous distributed power allocation for sum-rate maximization on cognitive GMACs is suggested. Simulation results show that this distributed algorithm for power allocation converges to a fixed point and the solution achieves almost the same performance as exhaustive search.
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| 9. |
- Han, Sang Wook, et al.
(författare)
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An efficient spectrum sharing for throughput enhancement in heterogeneous networks
- 2014
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Ingår i: Proceedings of the International Symposium on Consumer Electronics, ISCE. - 9781479945924
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Konferensbidrag (refereegranskat)abstract
- Spectrum sharing has been considered as one of candidate technologies for enhancing spectral efficiency in wireless networks. Efficient cooperation among multiple radio access networks and proper system parameter setting regarding spectrum sharing are required in order to accomplish improvement on the system performance through spectrum sharing in such heterogeneous networks. This paper proposes a spectrum sharing scheme among access networks utilizing licensed and unlicensed band with an objective of enhancing system throughput while satisfying the user quality of service (QoS) under a simple condition of user deployment. A problem formulation to achieve the objective is suggested which enhances the system' spectral efficiency.
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| 10. |
- Han, S. -W, et al.
(författare)
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Distributed power allocation for cooperative access in cognitive radios to guarantee QoS for cell edge primary users
- 2013
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Ingår i: Proceedings of 2013 6th Joint IFIP Wireless and Mobile Networking Conference, WMNC 2013. - New York : IEEE. - 9781467356169 ; , s. 6549027-
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Konferensbidrag (refereegranskat)abstract
- Cognitive radio (CR) systems have been proposed for efficient usage of spare spectrum licensed to primary systems. This leads to the issue of providing as much spectrum to CR users as possible while not degrading the quality of service (QoS) of primary users of the spectrum. This paper proposes a novel cooperation scheme between primary and CR users to guarantee QoS of primary users up to the cell edge while making the licensed spectrum available for opportunistic access by the CR users. We suggest that the primary users at the cell edge, who have poor QoS, should allow secondary users to access their spectrum, while at the same time, the secondary users would help to enhance the primary users QoS using superposition coding on the primary users transmissions. Thus the proposed method can provide a so called 'win-win strategy' by benefiting both primary and CR users. The proposed cooperative access scheme in cognitive radios solves efficiently the sum-rate maximization problem on cognitive Gaussian Multiple Access Channels (GMACs) for power allocation of primary systems that cooperates with CR systems in a distributed fashion. We solved the problem using iterative Jacobian method in a distributed manner. Numerical results show that the QoS of primary users at the cell edge is improved by the proposed cooperative access scheme.
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