Multiple Access for Visible Light Communications: Research Challenges and Future Trends

Abstract

The ever-increasing demand of mobile Internet and multimedia services poses unique and significant challenges for current and future generation wireless networks. These challenges are mainly relating to the support of massive ubiquitous connectivity, low latency and highly efficient utilization of spectrum resources. Therefore, it is vital to consider them extensively prior to design and deployment of future wireless networks. To this end, the present article provides a comprehensive overview of a particularly promising and effective wireless technology, namely, visible light communication (VLC). In this context, we initially provide a thorough overview of frequency domain multiple access techniques for single and multi-carrier systems, which is then followed by an in depth discussion on the technical considerations of optical code division multiple access techniques and their adoption in indoor VLC applications. Furthermore, we address space division multiple access and, finally, we revisit and analyze the distinct characteristics of a new technology, namely, non-orthogonal multiple access, which has been proposed recently as a particularly effective solution.

Performance analysis of user association strategy based on power-domain non-orthogonal multiple access in visible light communication multi-cell networks

“…1. Therefore, in VLC multiple cells, the edge user who should abandon the principle of proximity access with minimum visible-light channel attenuation should consider the cell deployment in (16). Note that the condition to satisfy for selecting the VPPA affects the access of edge users in the sequential iteration, and thus, the user association strategy focused in this paper can be commonly used for grouping and handover of edge users.…”

“…For coordinated scheduling, another study [15] reviewed the current research that used VLC access point (AP) cooperation techniques for improving VLC networks and mitigate interferences. For joint processing, both joint transmission (JT) [8,9,16,17] and dynamic cell selection (DCS) techniques have been studied [7]. From the above, user association in NOMA-VLC [18] is an important base for these multi-cell techniques; traditional proximity access principles [16,[19][20][21] favor the move towards the proximity of a transmitting light emitting diode (LED).…”

“…For joint processing, both joint transmission (JT) [8,9,16,17] and dynamic cell selection (DCS) techniques have been studied [7]. From the above, user association in NOMA-VLC [18] is an important base for these multi-cell techniques; traditional proximity access principles [16,[19][20][21] favor the move towards the proximity of a transmitting light emitting diode (LED). In addition, the principles of user association can be evaluated based on the received signal strength [22] and signal-to-noise ratio [17,23,24].…”

Multiple Access Techniques for VLC in Large Space Indoor Scenarios: A Comparative Study

“…At the receiver (Rx), each user correlates the received signal with its specific code in order to (ideally) suppress the IUI. For this, the SS should be distinguishable from its shifted version as well as the shifted versions of other users' SS [4]. Note that random optical codes (ROCs) are simpler to generate than OOCs [11], but they provide a sub-optimal performance.…”

“…Considering the general context of VLC applications, a general overview of the MU VLC techniques was presented in [2]. Also, a survey of different MA techniques for VLC applications was provided in [3] and [4]. Authors in [5] reviewed the non-orthogonal multiple access (NOMA) approach for VLC.…”