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| 2. |
- Chatzidiamantis, N. 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: IEEE International Conference on Communications. - : IEEE. - 1550-3607. - 9781612842332 ; , s. Art. no. 5962684-
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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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| 3. |
- 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. - : Institute of Electrical and Electronics Engineers (IEEE). - 0733-8724 .- 1558-2213. ; 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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| 4. |
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| 5. |
- Matthaiou, Michail, 1981, et al.
(författare)
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A new lower bound on the ergodic capacity of distributed MIMO systems
- 2011
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Ingår i: IEEE Signal Processing Letters. - 1070-9908 .- 1558-2361. ; 18:4, s. 227-230
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Tidskriftsartikel (refereegranskat)abstract
- We present a novel and analytical lower bound on the ergodic capacity of distributed multiple-input multiple-output (D-MIMO) systems operating in composite Rayleigh/lognormal (RLN) fading and assuming double-sided spatial correlation. The proposed lower bound is applicable for finite number of antennas and remains tight across the entire Signal-to-Noise (SNR) regime. In addition, we perform a detailed low-SNR analysis that provides useful insights into the implications of the system parameters on MIMO capacity.
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| 6. |
- Matthaiou, Michail, 1981, et al.
(författare)
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On the capacity of generalized-K fading MIMO channels
- 2010
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Ingår i: IEEE Transactions on Signal Processing. - 1941-0476 .- 1053-587X. ; 58:11, s. 5939-5944
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Tidskriftsartikel (refereegranskat)abstract
- This correspondence explores the ergodic capacity of multiple-input multiple-output (MIMO) systems operating in generalized-K fading conditions. Using some recent results on majorization theory, we derive an analytical capacity bound which is applicable for arbitrary values of the signal-to-noise ratio (SNR) and number of antenna elements.In addition, we deduce simple bound approximations in the high-SNR regime and demonstrate that the effects of small and large-scale fading are decoupled. A similar statistical analysis is carried out for MIMO channelsunder K-fading, which represents a special case of generalized- fading that can be tackled via the Wishart matrix theory. The implications of the model parameters on the bound performance are also investigated viaMonte Carlo simulations.
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| 7. |
- Matthaiou, Michail, 1981, et al.
(författare)
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On the sum rate of ZF detectors in correlated K fading MIMO channels
- 2011
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Ingår i: ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings. - 1520-6149. - 9781457705397 ; , s. 3244-3247
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Konferensbidrag (refereegranskat)abstract
- This paper presents a detailed sum rate investigation of Zero-Forcing (ZF) detectors over composite multiple-input multiple-output (MIMO) channels. To this end, we consider the generic K distribution (Rayleigh/gamma distribution) to model the composite fading fluctuations and also assume the general case of semi-correlated small-scale fading. Novel exact analytical expressions are derived for the achievable sum rate followed by asymptotic expressions in the low Signal-to-Noise ratio (SNR) regime. In parallel, new, closed-form upper and lower bounds on the sum rate are derived that remain tight for all SNRs. The theoretical analysis is validated via a set of Monte-Carlo simulations.
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| 8. |
- Matthaiou, Michail, 1981, et al.
(författare)
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Performance analysis of space-time block codes over generalized-K fading MIMO channels
- 2011
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Ingår i: 2011 IEEE Swedish Communication Technologies Workshop, Swe-CTW 2011. - 9781457718786 ; :Art. no. 6082491, s. 68-73
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Konferensbidrag (refereegranskat)abstract
- This paper elaborates on the performance of orthogonal space-time block codes (STBCs) for multiple-input multiple-output (MIMO) systems operating in generalized-K fading conditions. The considered fading model is generic since it intimately encompasses both small-scale fading (modeled via the Nakagami-m distribution) and large-scale fading (modeled via the gamma distribution). In the following, new exact analytical expressions are derived for the Shannon capacity along with asymptotic expressions in the high and low Signal-to-Noise ratio (SNR) regimes. We also present exact tractable expressions followed by first-order expansions for the marginal outage probability and symbol error rate (SER); further, we quantify the performance of STBCs in terms of diversity order and coding gain. The derived analytical expressions are validated via a set of Monte-Carlo simulations which also demonstrate the implications of the model parameters on the overall performance.
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| 9. |
- Matthaiou, Michail, 1981, et al.
(författare)
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ZF detectors over correlated K MIMO channels
- 2011
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Ingår i: IEEE Transactions on Communications. - 0090-6778 .- 1558-0857. ; 59:6, s. 1591-1603
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Tidskriftsartikel (refereegranskat)abstract
- This paper provides a systematic characterization of Zero-Forcing (ZF) detectors over multiple-input multiple-output (MIMO) channels that experience both small and large-scale fading. In particular, we consider the generic K distribution (Rayleigh/gamma distribution) to model the composite fading fluctuations and also assume the general case of semi-correlated small-scale fading. In the following, novel exact analytical expressions for the achievable sum rate are derived, followed by asymptotic expressions in the high and low Signal-to-Noise ratio (SNR) regimes. In these limiting cases, two common and insightful affine expansions are studied followed by new, closed-form upper and lower bounds on the sum rate that remain tight for all SNRs. In the second part of the paper, we present exact tractable expressions along with first-order expansions for the symbol error rate (SER) and outage probability; we also quantify the performance of ZF detectors in terms of diversity order and array (or coding) gain. The implications of the model parameters on the ZF detector performance are investigated via Monte-Carlo simulations which also validate the theoretical analysis.
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