Browsing by Author "Tsiftsis, T. A."

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    Advances in broadband single-carrier transmission techniques: Theory and applications (ABSCTT 2012)
    (IEEE, 2012) Muhaidat, S.; Uysal, Murat; Tsiftsis, T. A.; Dianati, M.; Abualhaol, I.; Electrical & Electronics Engineering; UYSAL, Murat
    The fourth-generation (4G) wireless technology is expected to provide a wide variety of new services including high quality multimedia, internet access and other high-data-rate wireless services. Moreover, 4G technology will include several types of wireless broadband access communication systems. A major design challenge for high-speed broadband applications is the dispersive nature of frequency-selective fading channels which leads to the so-called inter-symbol interference (ISI).
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    Error-rate performance analysis of cooperative OFDMA system with decode-and-forward relaying
    (IEEE, 2014-06) Fareed, M. M.; Uysal, Murat; Tsiftsis, T. A.; Electrical & Electronics Engineering; UYSAL, Murat
    In this paper, we investigate the performance of a cooperative orthogonal frequency-division multiple-access (OFDMA) system with decode-and-forward (DaF) relaying. Specifically, we derive a closed-form approximate symbol-error-rate expression and analyze the achievable diversity orders. Depending on the relay location, a diversity order up to (L-SkD + 1) + Sigma(M)(m=1) min(L-SkRm + 1, L-RmD + 1) is available, where M is the number of relays, and L-SkD + 1, L-SkRm + 1, and L-RmD + 1 are the lengths of channel impulse responses of source-to-destination, source-to-mth relay, and mth relay-to-destination links, respectively. Monte Carlo simulation results are also presented to confirm the analytical findings.
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    Iterative near maximum-likelihood sequence detection for MIMO optical wireless systems
    (IEEE, 2010-04) Chatzidiamantis, N. D.; Uysal, Murat; Tsiftsis, T. A.; Karagiannidis, G. K.; Electrical & Electronics Engineering; UYSAL, Murat
    A major performance-limiting factor in terrestrial optical wireless (OW) systems is turbulence-induced fading. Exploiting the additional degrees of freedom in the spatial dimension, multiple laser transmitters combined with multiple receive apertures provide an effective solution for fading mitigation. Although multiple-input multiple-output (MIMO) OWsystems have been extensively studied in recent years, most of these works are mainly limited to symbol-by-symbol decoding. MLSD exploits the temporal correlation of turbulence-induced fading and promises further performance gains. In this paper, we investigate MLSD for intensity-modulation/direct-detection MIMO OW systems over log-normal atmospheric turbulence channels. Even with a low-order modulation scheme such as OOK, which is typically used inOWsystems, the complexity ofMLSD might be prohibitive. We therefore present an iterative sequence detector based on the expectation–maximization (EM) algorithm. The complexity of the proposed algorithm is considerably less than a direct evaluation of the log-likelihood function, and it is independent of the channel’s fading statistics. The Monte Carlo simulation results demonstrate that the EM-based algorithm outperforms the symbol-by-symbol decoder and achieves a performance, which lies within 0.3 dB of that of the optimal MLSD.