Compact Optimal Pilot Design for Channel Estimation in MIMO VLC Systems

Abstract

In visible light communication (VLC) systems, like in radio frequency (RF) wireless communication systems, the channel has to be estimated to aid transceiver operations such as data detection and precoding. The LEDs which serve as VLC transmitters have to maintain a desired average intensity as they are simultaneously used for both data transmission as well as lighting, and each LED also has a maximum power constraint. In this paper, we are concerned with channel estimation in VLC systems under these constraints. Specifically, we consider extensions to combinational codes for optimal pilot transmission assuming that the receiver employs a zero-forcing decoder. We construct optimal codes which need much fewer pilot channel uses for channel estimation compared to that needed by combinational codes. We propose a recursive algorithm to construct such codes that are short in length and meet the optimality constraints. The bit error performance achieved using the estimates of the channel obtained using the proposed codes are shown to be quite close to that with perfect channel knowledge.