Optimal LED placement in indoor VLC networks

Abstract

In the upcoming 5G systems, the use of optical attocells will be largely exploited, with the aim of extending connectivity to multiple users while reducing coverage holes in indoor environments. The deployment of light emitting diodes (LEDs) should be well considered in order to use the optimal number of attocells to guarantee both illumination and connectivity, as a large and unnecessary number of attocells in a room is not useful and can cause interference among neighboring lighting cells. On the other hand, a low number of LEDs may not guarantee the whole illumination/data coverage, causing outage to users attempting to access the medium. In this paper, we investigate the problem of optimal LEDs placement in indoor environments, subject to constraints on illumination and outage based on user data rate. Two approaches are introduced, focusing on (i) the minimization of the number of LEDs to be used to provide required services and (ii) the maximization of the number of users to be served with a fixed number of LEDs, respectively. Numerical results are carried out in different room scenarios, which distinguish from the probability density function of users laying in such environments.

Interference in multi-user optical wireless communications systems

“…This class consists of the techniques that allow an AP or set of APs to distribute defined resources across a set of users. It is divided into two further categories: [18,73,74] Differential detection (DD) [75] Spatial light modulators (SLM) [67] Orthogonal multiplexing (WDM) [53][54][55] AP placement and configuration [43][44][45][46] Beam control and steering [32,[47][48][49][50][51][52]68] Multiple access techniques (TDMA, OFDMA, CDMA) [19][20][21] Precoding (ZF, MMSE) for MU-MISO NOMA [29][30][31][33][34][35][36][37][38][39][40][41][42] [ [22][23][24][25][26][27][28] MA-SP MA-PHY spatial diversity multiple access -Spatial diversity. This class encompasses both of the PHY and SP cases and is concerned with receiving data by many spatially unique channels or multiple PDs then performing signal processing to have them de-correlated.…”

“…Results show that a hexagonal set-up for VLC APs gives best coverage and least interference fraction. Vegni et al [46] study optimal LED placement in indoor VLC networks under constraints of illumination and data rate outage. They propose two techniques-attocell minimization (ACM), aims to minimize the number of attocells that can serve a given number of users (to minimize unnecessary interference) and attocell user maximization (AUM), which maximizes the number of users that an attocell can serve.…”

“…Results show that a hexagonal set-up for VLC APs gives best coverage and least interference fraction. Vegni et al [46] minimize the number of attocells that can serve a given number of users (to minimize unnecessary interference) and attocell user maximization (AUM), which maximizes the number of users that an attocell can serve. The results show that a large half-power semiangle and lower data rate per user requirement can realize an improved guaranteed performance.…”

Optical-Interference Mitigation in Visible Light Communication for Intelligent Transport Systems Applications

“…Considering the vertical and horizontal movements of the vehicles due to road surface and traffic conditions [39], a set of four LEDs is arranged in a square shape to ensure the availability of adequate amounts of illumination in different conditions. A lower number of units will cause an insufficient level of received power [40]. On the other hand, increasing the number of LED units will result in high cost and complexity.…”

Experimental Demonstration of Zadoff–Chu Matrix Transform Precoding for MIMO-OFDM Visible Light Communications

“…With high luminous power, small size, good modulation performance, and low cost, white light-emitting diode (LED) is expected to be the recommended lighting equipment for the next generation [1,2]. Meanwhile, visible light communication (VLC) has drawn increasing attention in both academia and industry, which supports illumination and communication simultaneously by modulating signals onto the LED [3,4]. Compared with traditional radio frequency (RF) communications, VLC takes the advantages of high efficiency, licensing free, no electromagnetic interference, and high security [5].…”