Serial Relaying Over Gamma-Gamma MIMO FSO Links: Diversity Order and Aperture Allocation

Serial relaying is analyzed in the context where the Free-Space Optical (FSO) communicating nodes are equipped with multiple apertures. We derive asymptotic expressions for the outage probability over the gamma-gamma fading channel and we evaluate the diversity orders that can be achieved by combining the multi-hop and multi-aperture techniques. A recursive algorithm that optimally allocates the apertures to the hops is also proposed. Results highlight the importance of aperture allocation for multi-hop-multi-aperture systems where significant performance improvements can be gained.