Performance of hybrid cellular-VLC link for indoor environments under dynamic user movement

Abstract

Visible light communications (VLC) is an emerging technology that complements the existing cellular network in order to provide high throughput, secure and power efficient indoor communication system. In this paper, we analyze the performance of hybrid cellular-VLC downlink where the outdoor coverage is provided via cellular network, and the indoor coverage is provided through a VLC system. In the proposed framework, VLC access point (AP) helps to communicate the information between the base station (BTS) and user by acting as a decode-and-forward (DF) relay. The relay decodes the received signal from the base station and then uses the decoded signal to modulate the intensity of the optical transmitter. Multiple light emitting diode (LED) transmitters with rectangular deployment are considered for a VLC transmitter. The channel model for VLC link has been modeled as an integrating sphere VLC channel which includes both line-of-sight (LOS) and non-line-of-sight (NLOS) links. Further, the movement and density of people have also been considered while deriving the closed-form expressions for the outage probability and bit-error-rate (BER) for the hybrid cellular-VLC downlink. In addition, the proposed work also utilizes optimal Lambertian order (OLO) to achieve increased average received optical power through LOS path and uniform delay spread in an indoor environment. It has been shown that by using the proposed hybrid cellular-VLC downlink, it is possible to achieve significant amount of power saving (approximately 51%) at BTS as compared to direct cellular link. Finally, the dimming range is calculated for the proposed system under dimming constraint. Results show that dimming range up to 70% can be achieved in the hybrid cellular-VLC link.