Indoor optical wireless systems (OWS) provide an attractive alternative for realizing next generation home access networks. Homodyne detection can be employed in order to enhance receiver sensitivity and spectral efficiency. In this paper, the application of space-time block-coding (STBC) techniques in a coherent OWS is theoretically and numerically investigated, taking into account the noise characteristics at the receiver. The performance of STBC multiple-input multiple-output (MIMO) systems, employing two transmit elements, is compared against single-input/single-output systems operating with the same total optical transmit power. It is shown that STBC is an effective means to increase the capacity of coherent OWS, improve their coverage, and decrease the required optical power at the transmitter. These results demonstrate the usefulness of MIMO techniques in the realization of future optical wireless local area networks.
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