Cooperative VLC system using OOK modulation with imperfect CSI

Abstract

Visible light communication (VLC) is one of the aspirant tools for high data rate communication. VLC system employed in a large room requires cooperative transmission for reliable end-to-end communication. Cooperative communication (CC) utilizes several relay approaches to forward the message from transmitter to envisioned destination, and thus, attains high spatial diversity gain, reduced power consumption, improved transmission reliability, increased coverage area, and potentially enhanced system capacity. This paper investigates the error performance of on-off keying (OOK) modulated VLC system in a cooperative environment, where the relay adopts decode-and-forward (DF) protocol. In particular, two cases of cooperative VLC system are considered; (1) Case I, in which the destination node is in direct link with the previous node while in blockage or outside the field of view (FoV) for all the other nodes, (2) Case II, in which the destination node is in direct link with all upstream nodes. For the practical suitability of the system, the imperfect channel state information (CSI) is considered for performance analysis. The mathematical expressions for bit-error-rate (BER) of the considered systems are derived in the presence of perfect and imperfect CSI. The error performance of the considered systems is investigated for the various system parameters such as signal-to-noise ratio (SNR), channel estimation error and receiver locations. The result shows that for the case of blockage, i.e., Case I, the end-to-end communication for two-hop network can be established with the BER of 2 × 10−4 at 128 dB SNR and channel estimation error of 10−12. Further, in the case of non-blockage, i.e., Case II, the result shows that for two-hop communication, the BER in cooperative transmission improved to 5 × 10−5 in compare to 5 × 10−2 in direct communication, at 128 dB SNR and 10−12 channel estimation error. The extensive simulations are carried out to verify the analytical findings.