  Chlorophylls and carotenoids, key components of photosynthetic systems, are
proposed for molecular communications at the nanoscale with the mechanism of
resonance energy transfer. Both types of pigments are introduced focusing on
their exceptional properties like energy harvesting, ultra-low energy
consumption during transmissions, picoseconds delays, an ability for signal
conversions, and bio-compatibility. The theoretical considerations are
supported by two spectroscopic experiments on the photosystem II complex. The
first experiment aims at the description of the photosystem II including
calculation of the energy transfer efficiency between carotenoids and
chlorophylls. In the second one, the photochemical efficiency is estimated,
showing how effective the chlorophylls are in further energy processing. With
the experimentally determined values, communication and energetic performance
are analyzed, the probability of channel blockage is calculated and the energy
consumption per bit is estimated. Treating carotenoid molecules as
transmitters, chlorophylls as receivers, and the energy transfer between them
as a way to encode information, a throughput up to 1 Gbit/s is achievable with
a bit error rate below 10^-3, average transmission delays about 20 ps, and
energy consumption c.a. 2.0x10^-18 J/bit. These results indicate a high
potential of photosynthetic systems for nanocommunications and other related
applications, due to suitable energetic characteristics in terms of energy
harvesting abilities and low consumption for data transmissions.
