Absorption Shift Keying for Molecular Communication via Diffusion

In molecular communication (MC), molecules can play dual roles, one as information carriers and the other as energy providers based on chemical reactions, the importance of which is self-evident. In this paper, we propose a novel modulation scheme, termed absorption shift keying (AbSK), to harvest unused molecules while boosting system performance. It relies on a third switch-controllable molecule harvesting node in addition to both transmitter and receiver in a conventional point-to-point MC scenario. In this setting, the proposed AbSK encodes information onto the ON/OFF state of the third node, so that it can act as a secondary source while capturing redundant molecules released by the primary source (or transmitter). Two detectors are designed for AbSK, namely ideal maximum likelihood and two-step detectors. Asymptotically tight bounds on the bit error rates of both detectors are derived in closed-form. Simulation results validate our theoretical analysis and show that the proposed AbSK outperforms benchmarks and additionally captures molecules to power future transmissions.