Error and channel capacity analysis of SIMO and MISO free-space opt ical communications

Free-space optical (FSO) communication is a promising solution, when higher capacities of data transmission, higher security, higher flexibility and robustness to RF interferences are required. Despite its advantages, the performance of a FSO link could be degraded due to atmospheric turbulence, which causes random fluctuations of the phase and the amplitude of the received signal. The use of multiple transmit/receive apertures have the potential to mitigate the degradation of fading effects, on turbulent optical channels. In this paper, we investigate the symbol-error-rate (SER) and the channel capacity (as the two principal factors in communication systems) of FSO links, using diversity and Q-Ary PPM modulation with a comparative viewpoint. It is shown that in a defined received energy per symbol, employing diversity in receiver is more efficient than the transmitter (five orders of magnitude lower SER and more efficient channel capacity).