Capacity and Optimum Signal Constellations for VLC Systems

Abstract

In this paper, the capacity of the point-to-point VLC system is investigated by means of functional analysis subject to amplitude constraint (and average intensity constraint). It is proved that the capacity can be reached by a unique probability density function (PDF). Two sets of necessary and sufficient conditions for the optimum PDF are derived. Moreover, the capacity-achieving PDF are proved to be discrete and finite. Given that the capacity can be achieved by a set of discrete and finite constellations, the capacity-achieving constellation optimization problems under amplitude constraint (and average intensity constraint) are formulated and algorithms are proposed to solve the corresponding problem. Since digital implementation is applied in most practical VLC systems, constellation optimization problem maximizing the mutual information subject to an additional equal probability constraint are put forward and analyzed.

Tight Capacity Bounds for Indoor Visible Light Communications With Signal-Dependent Noise

“…Proof 8: See Appendix H. 5 Similar to the lower bound in Theorem 2, the lower bound in Theorem 6 is also valid for all values of optical intensities. 6 Similar to the upper bound in Theorem 3, the upper bound in Theorem 7 is also valid only when the optical intensity is sufficiently large.…”

“…Remark 1. For the VLC having only the signal-independent noise, we derive the secrecy capacity lower bound (15) in Corollary 1 based on the principle of OELIE (11), while the authors in [29] also derived a lower bound ( 8) by using the entropy power inequality (EPI). It can be easily shown that the lower bound (15) in Corollary 1 is smaller than the lower bound (8) in [29].…”

“…With the fast development of light-emitting diodes (LEDs), visible light communications (VLC) has attracted considerable interest recently [3], [4]. As a compelling alternative technology for radio frequency (RF) communications, VLC is free from RF interference and is license-free [5]. Undoubtedly, VLC has become a promising candidate for future wireless communications.…”

“…However, these bounds do not consider the effects of the modulation schemes on the capacity performance. Employing pulse amplitude modulation [9], orthogonal frequency division multiplexing [10], and color shift keying [11], the authors investigated the channel capacities of VLC, respectively. In addition, by considering some actual factors, such as spatially random receiver [12] and signal interference [13], the authors further evaluated the channel capacities of VLC.…”

Study of the Performance of Deep Learning-Based Channel Equalization for Indoor Visible Light Communication Systems

“…Visible light communication (VLC) is a promising technique for indoor short-range wireless communications systems [1,2]. It has many advantages such as high anti-electromagnetic interference, low cost, good safety, and a rich and license-free spectrum.…”