ABSTRACT

This chapter describes the diversity techniques in high-speed near-infrared indoor Optical Wireless Communication (OWC) systems. High-speed near-infrared indoor OWC systems have been demonstrated using both line-of-sight (LOS) and non-LOS link configurations. The LOS link-based indoor OWC system has two key advantages: ultra-high channel bandwidth and high energy efficiency with low transmission power. In the LOS link-based indoor OWC systems, the communication link can be blocked by physical shadowing, such as cubicle partitions, furniture or moving personnel, especially when the user is moving. In indoor OWC systems with transmitter diversity, multiple optical transmitters available can be used to transmit the same signal or different signals, and multiple diversity coding schemes can be used. In addition to the repetition coding-based transmitter diversity scheme, the space-time block coding is also widely considered in indoor OWC systems. In the experimental demonstration system, the two OWC beams are spatially close to each other, and the free-space signal transmission distance is 1 m.