Browsing by Author "Kizilirmak, R. C."

Now showing 1 - 5 of 5

Metadata only
eU-OFDM based multiple access for visible light communication networks
(IEEE, 2017) Djengomemgoto, Gerard; Narmanlıoğlu, Ömer; Kizilirmak, R. C.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat; Djengomemgoto, Gerard; Narmanlıoğlu, Ömer
In this paper, we propose a novel protocol for cooperative multiple access in visible light communication (VLC) networks. The proposed protocol exploits the features of enhanced unipolar orthogonal frequency division multiplexing (eU-OFDM) scheme in order to enable user terminals to sequentially access the multi-hop network. The signal-to-noise ratios (SNRs) for user terminals within the network are derived and the individual bit-error-rate (BER) expressions are presented. We evaluate the BER performances of each user in the network through Monte Carlo simulation. The theoretical results validates the simulation results.
Open Access
Link adaptation for MIMO OFDM visible light communication systems
(IEEE, 2017-11-10) Narmanlıoğlu, Ömer; Kizilirmak, R. C.; Baykas, T.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat; Narmanlıoğlu, Ömer
In this paper, we investigate link adaptation for an orthogonal frequency division multiplexing (OFDM)-based multiple-input multiple-output (MIMO) visible light communication (VLC) system. The proposed adaptive OFDM VLC system supports both repetition coding (RC) and spatial multiplexing (SM) as MIMO modes and allows spatial mode switching based on channel conditions. Regarding to the instantaneous signal-to-noise ratio for both RC and SM modes, the maximum constellation size that can be supported for each MIMO mode on each subcarrier is determined. The MIMO mode that gives the highest spectral efficiency (SE) is then selected. The proposed joint MIMO mode selection and bit loading scheme maximizes the SE while satisfying a target bit error rate. Our numerical results reveal that a peak data rate up to 18.3 Gb/sec can be achieved in a 16 × 16 MIMO setting using light emitting diodes with cut-off frequency of 10 MHz in typical indoor environments.
Metadata only
Non-orthogonal multiple access (NOMA) for indoor visible light communications
(IEEE, 2015) Kizilirmak, R. C.; Rowel, C. R.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat
Providing multiple access support to visible light communication (VLC) systems requires new networking architecture. Non-orthogonal multiple access (NOMA) is a proposed multiple access technique for future cellular systems. In this work, based on a realistic indoor channel conditions, we apply NOMA to indoor VLC channels and demonstrate its superior performance over orthogonal frequency division multiple access (OFDMA).
Metadata only
Relay-assisted OFDM transmission for indoor visible light communication
(IEEE, 2014) Kizilirmak, R. C.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat
In this study, we investigate a relay-assisted visible light communication (VEC) system where an intermediate light source cooperates with the main light source. Specifically, we consider two light sources in an office space; one is the information source employed on the ceiling and the other one is a task light mounted on a desk. Our system builds upon DC biased optical orthogonal frequency division multiplexing (DCO-OFDM). The task light performs amplify-and-forward relaying to assist the communication and operates in half-duplex mode. We investigate the error rate performance of the proposed OFDM-based relay-assisted VEC system. Furthermore, we present joint AC and DC optimal power allocation in order to improve the performance. The DC power allocation is controlled by sharing the number of LED chips between the terminals and the AC power allocation decides the fraction of the information signal energy to be consumed at the terminals. Simulation results reveal that the VLC. system performance can be improved via relay-assisted transmission and the performance gain as much as 6 dB can be achieved.
Metadata only
Relay-assisted OFDM-based visible light communications over multipath channels
(IEEE, 2015-07) Narmanlıoğlu, Ömer; Kizilirmak, R. C.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat; Narmanlıoğlu, Ömer
In this paper, we investigate the performance of relay-assisted visible light communication (VLC) system over multipath channels. We consider an indoor environment where the ceiling light serves as the information source and a desk light helps the source forward the information to the destination. The VLC system is built on orthogonal frequency division multiplexing (OFDM) with either amplify-and-forward or decode-and-forward relaying. A realistic channel impulse response of the indoor environment generated through ray tracing is used. Through simulations, we present the bit error rate performance of OFDM-based relay-assisted VLC system over indoor multipath channels and quantify the performance degradation with respect to idealistic single tap channels. We further discuss the impact of imperfect channel estimation on the performance.