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| 2. |
- Seifi, Nima, 1981-, et al.
(författare)
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Impact of base station antenna tilt on the performance of network MIMO systems
- 2012
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Ingår i: IEEE 75th Vehicular Technology Conference, VTC Spring 2012, Yokohama, 6 May-9 June 2012. - 1550-2252. - 978-146730990-5
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Konferensbidrag (refereegranskat)abstract
- We study the downlink of a multicell MIMO system where clusters of multi-antenna base stations jointly serve multiple single-antenna users, commonly referred to as a network MIMO system. Most of the previous studies on network MIMO have only considered the azimuth pattern of the antenna, while ignoring the elevation pattern. In this paper, we consider both the azimuth and the elevation patterns and investigate the impact of the elevation angle tuning parameter, denoted as the antenna tilt, on the performance of such systems. Using system simulations, it is shown that the promised performance gains of network MIMO systems over conventional non-coordinated systems, crucially depend on the choice of the right tilt setting including the tilt type, i.e., mechanical or electrical, and the tilt angle. In particular, for tilt angles smaller than the optimum, network MIMO with intra-site coordination performs almost as well as the conventional system; while for tilt angles larger than the optimum, the performance of network MIMO with intra-site is similar to that of network MIMO with inter-site coordination.
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| 6. |
- Chatzidiamantis, Nestor D., et al.
(författare)
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Diversity combining in hybrid RF/FSO systems with PSK modulation
- 2011
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Ingår i: Proc. IEEE International Conference on Communications (ICC) Kyoto, 5-9 June 2011. - 0536-1486. - 978-161284233-2
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Konferensbidrag (refereegranskat)abstract
- We present a novel architecture for hybrid radio frequency (RF)/ free space optical (FSO) wireless systems without feedback or channel state information (CSI) at the transmitter. Under the assumption that 60 GHz RF and FSO systems support the same data rates, the proposed implementation transmits the same data over both links, using phase shift keying (PSK) as a common modulation scheme, and combines the signals from each individual link at the receiver on a symbol-by-symbol basis. Two popular diversity combining schemes are considered, namely, selection combining (SC) and maximal ratio combining (MRC), while tractable analytical approximations for the bit error rate (BER) are obtained. Investigations over various weather conditions and link distances revealed that the proposed implementation fully exploits the complementary nature of RF and FSO channels, even when one of the two available links fails. Furthermore, the comparison of the combining schemes demonstrates MRC as the optimum combining scheme, offering link distance gains compared to SC.
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| 7. |
- Chatzidiamantis, N. D., et al.
(författare)
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Inverse Gaussian Modeling of Turbulence-Induced Fading in Free-Space Optical Systems
- 2011
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Ingår i: Journal of Lightwave Technology. - 0733-8724. ; 29:10, s. 1590-1596
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Tidskriftsartikel (refereegranskat)abstract
- We propose the inverse Gaussian distribution, as a less complex alternative to the classical log-normal model, to describe turbulence-induced fading in free-space optical (FSO) systems operating in weak turbulence conditions and/or in the presence of aperture averaging effects. By conducting goodness of fit tests, we define the range of values of the scintillation index for various multiple-input multiple-output (MIMO) FSO configurations, where the two distributions approximate each other with a certain significance level. Furthermore, the bit error rate performance of two typical MIMO FSO systems is investigated over the new turbulence model; an intensity-modulation/direct detection MIMO FSO system with Q-ary pulse position modulation that employs repetition coding at the transmitter and equal gain combining at the receiver, and a heterodyne MIMO FSO system with differential phase-shift keying and maximal ratio combining at the receiver. Finally, numerical results are presented that validate the theoretical analysis and provide useful insights into the implications of the model parameters on the overall system performance.
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| 9. |
- de Kerret, Paul, et al.
(författare)
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Analytic framework for the mutual information cumulants of different MIMO channels
- 2010
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Ingår i: IEEE Global Telecommunications Conference (GLOBECOM). - 978-142445638-3
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Konferensbidrag (refereegranskat)abstract
- In this paper, we present a general analytical framework for the exact mutual information (MI) cumulants of multiple-input multiple-output (MIMO) systems with perfect receiver channel state information (CSI) and no transmitter CSI. Our derivation is based on a recent parameterization of the joint ordered eigenvalue probability density function (PDF) [1], that encompasses both uncorrelated/semi-correlated Rayleigh channels as well as uncorrelated Rician channels. In addition, we extend our framework to account for the cumulants of doubly-correlated Rayleigh channels and also to deduce tractable expressions in the high Signal-to-Noise ratio (SNR) regime. The cumulants are particularly useful to study all high-order statistics (HOS) of the MI; in fact, they can be used to express the MI mean and variance as a finite sum of determinants. Our analytical expressions are then validated via Monte-Carlo simulations with the attained accuracy being excellent in all cases.
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| 10. |
- Gopal, V., et al.
(författare)
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Performance analysis of distributed MIMO systems in Rayleigh/Inverse- Gaussian fading channels
- 2012
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Ingår i: IEEE Global Communications Conference, GLOBECOM 2012, Anaheim, United States, 3-7 December 2012. - 1930-529X. - 978-146730921-9 ; s. 2468-2474
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Konferensbidrag (refereegranskat)abstract
- In this paper, we pursue a performance evaluation of distributed multiple-input multiple-output (MIMO) systems in composite Rayleigh/Inverse- Gaussian fading channels. Capitalizing on some generic bounding techniques, we first derive new closed-form bounds on the ergodic capacity of optimal receivers. In order to gain useful insights into the impact of fading parameters on optimal receivers' performance, a detailed characterization in the asymptotically high and low signal-to-noise ratio regimes is also provided. In addition, we explore the 'large-system' regime and provide asymptotic expressions when the number of antennas grows large. A similar performance analysis is performed for the achievable sum rate of distributed MIMO systems employing linear minimum mean-square error receivers.
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