Practical issues in the combining of MIMO techniques and RoF in OFDM/A systems

In this paper, several multipleinput multipleoutput (MIMO) techniques are studied for OFDM/A systems which have antennas connected to the base station with radio over fiber (RoF). The delay effects caused by the optical fibers on the fixed-beam transmit beamforming are studied via Monte Carlo simulations. Also the effect of combining RoF with other MIMO techniques in OFDM/A systems, like spatial multiplexing, spacetime coding, and receiver beamforming, is discussed. The results indicate that for phase shift differences lower than those corresponding to a 1 m unevenness in the fiber's length, RoF does not significantly decrease the performance of an OFDM/A system with fixed transmit beamforming, and with other MIMO techniques, the effect of employing RoF is negligible.