Molecular communications with longitudinal carrier waves: Baseband to passband modulation

Traditional molecular communications via diffusion (MCvD) systems have used baseband pulse modulation techniques by varying properties of molecular pulses such as the amplitude, the frequency of the transversal wave of the pulse, and the time delay between subsequent pulses. Given the difficulty of implementing chemical bandwidth, molecular communications has a limited data rate. In this letter, we propose and implement passband modulation by precisely controlling the longitudinal wave properties of molecules, effectively creating distinguishable carrier waves. This is achieved through a simple oscillation of the transmitter. Molecular frequency division multiplexing is achieved and we demonstrate that different molecular information streams can co-exist in the same space and time channel, creating bandwidth for MCvD.