Relay-assisted OFDM transmission for indoor visible light communication

Abstract

Due to copyright restrictions, the access to the full text of this article is only available via subscription.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

Relay-assisted OFDM-based visible light communications over multipath channels

“…In our simulation study, we consider a room with dimensions of 5×5×3 m. The corresponding optical PDPs are obtained in Zemax ® using non-sequential ray tracing [9] and presented in Fig. 1.…”

“…can be further defined as another optimization parameter to denote the fraction of the total number of LED chips shared between source and relay [9]. This parameter is related to the DC energy consumption of LEDs and therefore the illumination level.…”

“…Source and relay nodes respectively consume 2 and 2 (1 − ) where is an energy optimization parameter to denote the fraction of the total energy shared between source and relay [9].…”

“…In our earlier work [9], we proposed a cooperative VLC scheme based on DC biased optical orthogonal frequency division multiplexing (DCO-OFDM) and evaluated the bit error rate (BER) performance under illumination constraints. In [9], the frequency-selectivity characteristics of multipath VLC channel were ignored under the assumption that signal bandwidth is lower than coherence bandwidth of channel; therefore, multipath components are non-resolvable. In this paper, we revisit our work in [9] and investigate the performance of cooperative OFDM VLC system over a frequency-selective channel.…”

“…In [9], the frequency-selectivity characteristics of multipath VLC channel were ignored under the assumption that signal bandwidth is lower than coherence bandwidth of channel; therefore, multipath components are non-resolvable. In this paper, we revisit our work in [9] and investigate the performance of cooperative OFDM VLC system over a frequency-selective channel. Specifically, we consider different pulse shaping filters (such as truncated sinc and raised cosine) and demonstrate the effect of multipath propagation on the error rate performance.…”