A fundamental framework for molecular communication channels: Timing & payload

As system sizes shrink, the usual macroscopic methods of communication using electromagnetic and acoustic waves become increasingly less efficient owing to mismatches between realizable antenna sizes and the propagation characteristics of the medium. Thus, at the scale of microns and below, communication methods which utilize molecular messengers become attractive, a notion supported by the ubiquity of molecular signaling in biological systems, sometimes using identical molecules (tokens) and sometimes using tokens with embedded payloads such as, for instance, m-RNA. Here we consider a wide range of molecular signaling techniques used by biological systems, and by applying simple information-theoretic concepts seek to develop an outerbound model which distills the plethora of channel details to (1) timing, and (2) molecular “packet” payloads as the information-bearing agents. We find that both bits/joule and bits/sec/joule efficiencies are greatly increased by using tokens with only 1-bit payloads and that overall information carriage efficiency (and consequently, bit rate) is best served by using tokens with large payloads.