An optical IM/DD based spatial transmission diversity achievable relay scheme

This paper presents an optical intensity-modulated direct-detection (IM/DD) based relay scheme for indoor optical wireless communication system. Multiple distributed optical relay links are set up between relay stations (RS) and mobile terminals (MT) to create multiple safe signal propagation links for wireless communication so that at least one link is available for data streaming. Different from conventional relay scheme, the phase shift of RF signals is pre-adjusted based on maximum ratio transmission (MRT) technique, and then relayed from multiple distributed optical transmitters which are set up in different places. The proposed relay scheme not only enhances signal power and achieves diversity, but also avoids possible obstruction of line-of-sight (LOS) signal. Furthermore since propagation phase variation of incoherent optical signal can be neglected, the propagation space becomes a non-directional scalar space, resulting in a much simpler system structure, where multiple optical antenna elements can be freely arranged, phase shift due to different transmitting paths is solely decided by the distance between transmitter and receiver, etc. The paper presents these features and also provides computer simulation results to demonstrate the performance. Simulation results show that the proposed relay system is much feasible and attractive, and it would be one of the promising candidates for future wireless and pervasive healthcare communication systems.