  Diffusion-based molecular communication over nanonetworks is an emerging
communication paradigm that enables nanomachines to communicate by using
molecules as the information carrier. For such a communication paradigm,
Concentration Shift Keying (CSK) has been considered as one of the most
promising techniques for modulating information symbols, owing to its inherent
simplicity and practicality. CSK modulated subsequent information symbols,
however, may interfere with each other due to the random amount of time that
molecules of each modulated symbols take to reach the receiver nanomachine. To
alleviate Inter Symbol Interference (ISI) problem associated with CSK, we
propose a new modulation technique called Zebra-CSK. The proposed Zebra-CSK
adds inhibitor molecules in CSK-modulated molecular signal to selectively
suppress ISI causing molecules. Numerical results from our newly developed
probabilistic analytical model show that Zebra-CSK not only enhances capacity
of the molecular channel but also reduces symbol error probability observed at
the receiver nanomachine.
