Browsing by Author "Damen, M. O."

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Comparative performance evaluation of MIMO visible light communication systems
(IEEE, 2016) Damen, M. O.; Narmanlioglu, Omer; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat; Narmanlioglu, Omer
In this paper, we consider multiple-input multiple-output (MIMO) visible light communication (VLC) systems. The physical layer of VLC system builds upon optical orthogonal frequency division multiplexing (O-OFDM). Repetition code (RC), spatial multiplexing (SMUX) and spatial modulation (SMUD) are considered as MIMO techniques. We evaluate the performance of three MIMO O-OFDM VLC systems under consideration through the derivation of bit error rate expressions.
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Design and analysis of broadband amplify-and-forward cooperative systems: A fractionally-spaced sampling approach
(IEEE, 2016-10-01) Heidarpour, M. R.; Uysal, Murat; Damen, M. O.; Electrical & Electronics Engineering; UYSAL, Murat
In this paper, we propose novel fractionally-spaced frequency-domain equalizers for the amplify-and-forward cooperative systems. In the proposed equalization schemes, the sampling rate of the received signal remains at least as high as the Nyquist rate within the digital processing chain of the relay node(s), upon which a true fractionally-spaced equalization becomes feasible at the destination. Based on minimum-mean-square-error (MMSE) criterion, different equalization structures (linear and non-linear) are designed, and approximations for their bit error rate (BER) performance are presented. The BER performance of the proposed schemes are further lower bounded through a matched-filter bound (MFB) analysis which provides insight into system design such as optimum power allocation and relay selection strategy. Our results show that, under certain channel realizations and sampling phase errors (that may occur in the relay and destination terminals), the performance of the conventional symbol-spaced cooperative systems reduces to that of no relay scenario. However, the performance of cooperative systems with the proposed fractionally-spaced equalizers is independent of the samplers' phases, and as a result, full benefit of cooperation is retained.
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Fractionally spaced equalization for broadband amplify-and-forward cooperative systems
(IEEE, 2013) Heidarpour, M. R.; Uysal, Murat; Damen, M. O.; Electrical & Electronics Engineering; UYSAL, Murat
In this paper, we revisit the concept of fractionally spaced equalization (FSE) for broadband single-carrier amplify-and-forward (AaF) cooperative systems. Particularly, we investigate fractionally spaced frequency domain equalization (FS-FDE) for cooperative multi-relay systems. Our motivation stems from the elegant properties reported for the FSE in the point-to-point communication systems (i.e., its robustness to sampling phases and potential in achieving the optimum performance) and the scalability of the FDEs. In particular, we propose a TS/2-spaced equalizer that transforms the temporal sample sequence of the received signal to the frequency domain, applies linear/decision-feedback equalization, and returns the resulting signal back to the time domain for detection. The vital importance of using FS-FDE method in cooperative systems is disclosed in practical scenarios where the transmitted signals have nonzero roll-off components and sampling phase error may occur in relay(s) and destination terminals. Our results demonstrate that, under specific channel realizations and sampling errors, the cooperative systems with symbol spaced FDE (SS-FDE) fail to harvest the available cooperative diversity and the performance approaches to that of no relay scenario. On the other hand, the performance of cooperative system with FS-FDE method becomes independent of sampling phase errors and full benefit of cooperation is retained.