| 1. |
- Khormuji, Majid N., et al.
(författare)
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Rotation optimization for MPSK/MQAM signal constellations over rayleigh fading channels
- 2006
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Ingår i: 2006 10th IEEE Singapore International Conference on Communication Systems, Vols 1 and 2. - 9781424404100 ; , s. 671-675
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Konferensbidrag (refereegranskat)abstract
- The performance of uncoded phase-shift-keying (PSK) and quadrature amplitude modulation (QAM) schemes over fading channels can be improved by using coded modulation techniques. Improvement is due to the coding gain coupled with interleaving and depends on the complexity of the code. Recently, it was shown that constellation rotation coupled with interleaving can be used to improve the performance of QPSK modulation over block-fading single-input-single-output (SISO) wireless communication channels. This paper considers the use of such a scheme with higher order constellation sets such as 8PSK and 16QAM. A framework is then presented for the calculation of the optimum rotation angle for MPSK/MQAM schemes. A simple cost function based on the union bound of the symbol error probability (SEP) is defined. The optimum rotation angle is then found by minimizing the cost function using the gradient search algorithm. The obtained simulation results show considerable improvement over the conventional unrotated system.
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| 2. |
- Rizvi, Umar H., et al.
(författare)
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Combined multiple transmit antennas and multilevel modulation techniques
- 2007
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Ingår i: 28th Symposium on Information Theory in the Benelux. ; , s. 1-8
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Konferensbidrag (refereegranskat)abstract
- The use of a unique bit-to-symbol mapping for each diversity branch (often referred to as constellation rearrangement) is known to provide good performance for higher level linear modulation techniques when used in conjunction with orthogonal transmit diversity (OTD) and automatic repeat request (ARQ) schemes. This paper investigates the performance of constellation rearrangement scheme when used in conjunction with multiple transmit antennas and space time block codes. A modified space-time block coding structure is presented that employs a different constellation mapping on each diversity branch. It is seen that, the use of different constellation mappings in the space time block coded systems provide a better performance as compared to the OTD systems while maintaining the same spectral efficiency.
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| 3. |
- Zhang, Ming, et al.
(författare)
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Identification of the target self-antigens in reperfusion injury.
- 2006
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Ingår i: Journal of Experimental Medicine. - : Rockefeller University Press. - 0022-1007 .- 1540-9538. ; 203:1, s. 141-52
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Tidskriftsartikel (refereegranskat)abstract
- Reperfusion injury (RI), a potential life-threatening disorder, represents an acute inflammatory response after periods of ischemia resulting from myocardial infarction, stroke, surgery, or trauma. The recent identification of a monoclonal natural IgM that initiates RI led to the identification of nonmuscle myosin heavy chain type II A and C as the self-targets in two different tissues. These results identify a novel pathway in which the innate response to a highly conserved self-antigen expressed as a result of hypoxic stress results in tissue destruction.
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