Abstract
Feature Issue on
Optical Wireless Communications (OWC)
The propagation of an on-off
keying modulated optical signal through an optical atmospheric turbulent channel is
considered. The intensity fluctuations of the signal observed at the receiver are
modeled using a gamma-gamma distribution. The capacity of this channel is determined
for a wide range of turbulence conditions. For a zero inner scale, the capacity
decreases monotonically as the turbulence strengthens. For non-zero inner scale, the
capacity is not monotonic with turbulence strength. Two error-correction schemes,
based on low-density parity-check (LDPC) codes, are investigated as a means to
improve the bit-error rate (BER) performance of the system. Very large coding
gains--ranging from 5.5 to 14 dB, depending on the turbulence conditions--are
obtained by these LDPC codes compared with Reed-Solomon error-correction codes of
similar rates and lengths.
© 2005 Optical Society of America
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