LSMS and Receiver Diversity Combining Methods for High-speed Optical Wireless Links

Abstract

In this paper, we investigate diversity-combining schemes for multibeam spot diffusing transmission based on a novel line strip multibeam system (LSMS). The proposed system employs a multibeam transmitter and a composite receiver consisting of narrow field-of-view (FOV) branches. Performance analyses of various combining techniques including equal gain combining (EGC), maximum ratio combining (MRC), as well as selection combining (SC) are presented. It is known that diversity methods result in an improved signal-to-noise ratio (SNR) at a price of increased complexity. The performance impairments imposed by multipath dispersion and ambient light noise are assessed with particular attention to their impact on the combining schemes. The focus in this paper, however, is on attaining a low-complexity high-speed infrared wireless link based on LSMS and a limited number of receiver branches. Our results show that the proposed low complexity diversity combining scheme, EQC, provides a significant and equal performance improvement compare to SC and MRC. Furthermore, LSMS employing angle diversity receiver with three and seven narrow FOV branches is evaluated. We have also compared the LSMS results with a conventional system that employs a wide FOV receiver. Simulation results demonstrate a promising performance improvement of up to 4 dB in SNR over the case of three branches and 28 dB over the conventional diffuse link.